ORGANIC ELECTROLUMINESCENT DEVICE

The present invention relates to organic electroluminescent devices including one or more light-emitting layers B, each of which is composed of one or more sublayers, wherein the one or more sublayers of each light-emitting layer B as a whole include at least one host material H^B, at least one phosphorescence material P^B, at least one small FWHM emitter S^B, and optionally at least one TADF material E^B, wherein the at least one, preferably each, S^Bemits light with a full width at half maximum (FWHM) of less than or equal to 0.25 eV. Furthermore, the present invention relates to a method for generating light by means of an organic electroluminescent device according to the present invention.

DESCRIPTION

Organic electroluminescent devices containing one or more light-emitting layers based on organics such as, e.g., organic light-emitting diodes (OLEDs), light-emitting electrochemical cells (LECs) and light-emitting transistors gain increasing importance. In particular, OLEDs are promising devices for electronic products such as e.g., screens, displays and illumination devices. In contrast to most electroluminescent devices essentially based on inorganics, organic electroluminescent devices based on organics are often rather flexible and producible in particularly thin layers. The OLED-based screens and displays already available today bear either good efficiencies and long lifetimes or good color purity and long lifetimes, but do not combine all three properties, i.e., good efficiency, long lifetime, and good color purity.

The color purity or color point of an OLED is typically provided by CIEx and CIEy coordinates, whereas the color gamut for the next display generation is provided by so-called BT-2020 and DCPI3 values. Generally, in order to achieve these color coordinates, top emitting devices are needed to adjust the color coordinate by changing the cavity. In order to achieve high efficiency in top emitting devices while targeting these color gamut, a narrow emission spectrum in bottom emitting devices is needed.

State-of-the-art phosphorescence emitters exhibit a rather broad emission, which is reflected in a broad emission of phosphorescence-based OLEDs (PHOLEDs) with a full-width-half-maximum (FWHM) of the emission spectrum, which is typically larger than 0.25 eV. The broad emission spectrum of PHOLEDs in bottom devices, leads to high losses in out-coupling efficiency for top emitting device structure while targeting BT-2020 and DCPI3 color gamut.

Additionally, phosphorescence materials are typically based on transition metals, e.g., iridium, which are quite expensive materials within the OLED stack due to their typically low abundance. Thus, transition metal based materials have the most potential for cost reduction of OLEDs. Lowering of the content of transition metals within the OLED stack thus is a key performance indicator for pricing of OLED applications.

Recently, some fluorescence or thermally-activated-delayed-fluorescence (TADF) emitters have been developed that display a rather narrow emission spectrum, which exhibits an FWHM of the emission spectrum, which is typically smaller than or equal to 0.25 eV, and therefore more suitable to achieve BT-2020 and DCPI3 color gamut. However, such fluorescence and TADF emitters typically suffer from low efficiency due to decreasing efficiencies at higher luminance (i.e., the roll-off behaviour of an OLED) as well as low lifetimes due to for example the exciton-polaron annihilation or exciton-exciton annihilation.

These disadvantages may be overcome to some extend by applying so-called hyper approaches. The latter rely on the use of an energy pump which transfers energy to a fluorescent emitter preferably displaying a narrow emission spectrum as stated above. The energy pump may for example be a TADF material displaying reversed-intersystem crossing (RISC) or a transition metal complex displaying efficient intersystem crossing (ISC). However, these approaches still do not provide organic electroluminescent devices combining all of the aforementioned desirable features, namely: good efficiency, long lifetime, and good color purity.

A central element of an organic electroluminescent device for generating light typically is the at least one light-emitting layer placed between an anode and a cathode. When a voltage (and electrical current) is applied to an organic electroluminescent device, holes and electrons are injected from an anode and a cathode, respectively.

Typically, a hole transport layer is (typically) located between a light-emitting layer and an anode, and an electron transport layer is typically located between a light-emitting layer and a cathode. The different layers are sequentially disposed. Excitons of high energy are then generated by recombination of the holes and the electrons in a light-emitting layer. The decay of such excited states (e.g., singlet states such as S1 and/or triplet states such as T1 to the ground state (S0) desirably leads to the emission of light.

Surprisingly, it has been found that an organic electroluminescent device's light-emitting layer consisting of one or more layers including a phosphorescence material, a small full width at half maximum (FWHM) emitter, a host material, and optionally a TADF material, provides an organic electroluminescent device having a long lifetime, a high quantum yield and exhibiting narrow emission, ideally suitable to achieve the BT-2020 and DCPI3 color gamut.

Herein, a phosphorescence material and/or an optional TADF material might transfer energy to a small full width at half maximum (FWHM) emitter displaying emission of light.

The present invention relates to an organic electroluminescent device including at least one light-emitting layer B which is composed of one or more sublayers, wherein the one or more sublayers are adjacent to each other and as a whole contain:

- (i) at least one host material H^B, which has a lowermost excited singlet state energy level E(S1^H) and a lowermost excited triplet state energy level E(T1^H); and
- (ii) at least one phosphorescence material P^B, which has a lowermost excited singlet state energy level E(S1^P) and a lowermost excited triplet state energy level E(T1^P); and
- (iii) at least one small full width at half maximum (FWHM) emitter S^B, which has a lowermost excited singlet state energy level E(S1^S) and a lowermost excited triplet state energy level E(T1^S), wherein S^Bemits light with a full width at half maximum (FWHM) of less than or equal to 0.25 eV; and optionally
- (iv) at least one thermally activated delayed fluorescence (TADF) material E^B, which has a lowermost excited singlet state energy level E(S1^E) and a lowermost excited triplet state energy level E(T1^E),
- wherein the one or more sublayers which are located at the outer surface of a light-emitting layer B contain at least one (emitter) material selected from the group consisting of phosphorescence material P^B, small FWHM emitter S^B, and TADF material E^B.

One aspect of the present invention relates to an organic electroluminescent device which includes at least one light-emitting layer B including one or more sublayers, wherein the one or more sublayers are adjacent to each other and as a whole contain:

- (i) a host material H^B, which has a lowermost excited singlet state energy level E(S1^H) and a lowermost excited triplet state energy level E(T1^H); and
- (ii) a phosphorescence material P^B, which has a lowermost excited singlet state energy level E(S1^P) and a lowermost excited triplet state energy level E(T1^P); and
- (iii) a small full width at half maximum (FWHM) emitter S^B, which has a lowermost excited singlet state energy level E(S1^S) and a lowermost excited triplet state energy level E(T1^S), wherein S^Bemits light with a full width at half maximum (FWHM) of less than or equal to 0.25 eV; and optionally
- (iv) a thermally activated delayed fluorescence (TADF) material E^B, which has a lowermost excited singlet state energy level E(S1^E) and a lowermost excited triplet state energy level E(T1^E),
- wherein the one or more sublayers which are located at the outer surface of a light-emitting layer B contain at least one (emitter) material selected from the group consisting of phosphorescence material P^B, small FWHM emitter S^B, and TADF material E^B.

In one embodiment of the invention, at least one of the one or more sublayers of the at least one light-emitting layer B includes:

- (iv) at least one thermally activated delayed fluorescence (TADF) material E^B, which has a lowermost excited singlet state energy level E(S1^E) and a lowermost excited triplet state energy level E(T1^E).

In one embodiment of the invention, the organic electroluminescent device includes at least one light-emitting layer B composed of one or more sublayers, wherein the one or more sublayers of the light-emitting layer B include:

- (i) at least one host material H^B, which has a lowermost excited singlet state energy level E(S1^H) and a lowermost excited triplet state energy level E(T1^H); and
- (ii) at least one phosphorescence material P^B, which has a lowermost excited singlet state energy level E(S1^P) and a lowermost excited triplet state energy level E(T1^P); and
- (iii) at least one small full width at half maximum (FWHM) emitter S^B, which has a lowermost excited singlet state energy level E(S1^S) and a lowermost excited triplet state energy level E(T1^S),
- wherein S^Bemits light with a full width at half maximum (FWHM) of less than or equal to 0.25 eV; and optionally
- (iv) at least one thermally activated delayed fluorescence (TADF) material E^B, which has a lowermost excited singlet state energy level E(S1^E) and a lowermost excited triplet state energy level E(T1^E).

- (i) a host material H^B, which has a lowermost excited singlet state energy level E(S1^H) and a lowermost excited triplet state energy level E(T1^H); and
- (ii) a phosphorescence material P^B, which has a lowermost excited singlet state energy level E(S1^P) and a lowermost excited triplet state energy level E(T1^P); and
- (iii) a small full width at half maximum (FWHM) emitter S^B, which has a lowermost excited singlet state energy level E(S1^S) and a lowermost excited triplet state energy level E(T1^S),
- wherein S^Bemits light with a full width at half maximum (FWHM) of less than or equal to 0.25 eV; and
- (iv) a thermally activated delayed fluorescence (TADF) material E^B, which has a lowermost excited singlet state energy level E(S1^E) and a lowermost excited triplet state energy level E(T1^E).

- (i) at least one host material H^B, which has a lowermost excited singlet state energy level E(S1^H) and a lowermost excited triplet state energy level E(T1^H); and
- (ii) at least one phosphorescence material P^B, which has a lowermost excited singlet state energy level E(S1^P) and a lowermost excited triplet state energy level E(T1^P); and
- (iii) at least one small full width at half maximum (FWHM) emitter S^B, which has a lowermost excited singlet state energy level E(S1^S) and a lowermost excited triplet state energy level E(T1^S),
- wherein S^Bemits light with a full width at half maximum (FWHM) of less than or equal to 0.25 eV; and
- (iv) at least one thermally activated delayed fluorescence (TADF) material E^B, which has a lowermost excited singlet state energy level E(S1^E) and a lowermost excited triplet state energy level E(T1^E).

In one embodiment of the invention, the organic electroluminescent device includes at least one light-emitting layer B including:

- (i) at least one host material H^B, which has a lowermost excited singlet state energy level E(S1^H) and a lowermost excited triplet state energy level E(T1^H); and
- (ii) at least one phosphorescence material P^B, which has a lowermost excited singlet state energy level E(S1^P) and a lowermost excited triplet state energy level E(T1^P); and
- (iii) at least one small full width at half maximum (FWHM) emitter S^B, which has a lowermost excited singlet state energy level E(S1^S) and a lowermost excited triplet state energy level E(T1^S), wherein S^Bemits light with a full width at half maximum (FWHM) of less than or equal to 0.25 eV; and
- (iv) at least one thermally activated delayed fluorescence (TADF) material E^B, which has a lowermost excited singlet state energy level E(S1^E) and a lowermost excited triplet state energy level E(T1^E).

In one embodiment of the invention, the organic electroluminescent device includes a light-emitting layer B composed of exactly one layer including:

- (i) a host material H^B; and
- (ii) a phosphorescence material P^B; and
- (iii) a small full width at half maximum (FWHM) emitter S^B; and optionally
- (iv) a TADF material E^B.

In a preferred embodiment, the organic electroluminescent device includes a light-emitting layer B composed of exactly one layer including:

- (i) at least one host material H^B; and
- (ii) at least one phosphorescence material P^B; and
- (iii) at least one small full width at half maximum (FWHM) emitter S^B; and
- (iv) at least one thermally activated delayed fluorescence (TADF) material E^B.

Combination of Sublayers

In a preferred embodiment of the invention, the electroluminescent device according to the invention includes at least one light-emitting layer B consisting of exactly one (sub)layer. In a preferred embodiment of the invention, each light-emitting layer B included in the electroluminescent device according to the invention consists of exactly one (sub)layer. In a preferred embodiment of the invention, the electroluminescent device according to the invention includes exactly one light-emitting layer B consisting of exactly one (sub)layer.

In another embodiment of the invention, the electroluminescent device according to the invention includes at least one light-emitting layer B composed of more than one sublayer. In another embodiment of the invention, each light-emitting layer B included in the electroluminescent device according to the invention includes more than one sublayer. In another embodiment of the invention, each light-emitting layer B included in the electroluminescent device according to the invention consists of more than one sublayer.

In another embodiment of the invention, the electroluminescent device according to the invention includes exactly one light-emitting layer B composed of more than one sublayer. In another embodiment of the invention, the electroluminescent device according to the invention includes at least one light-emitting layer B composed of exactly two sublayers.

In another embodiment of the invention, each light-emitting layer B included in the electroluminescent device according to the invention is composed of exactly two sublayers. In another embodiment of the invention, the electroluminescent device according to the invention includes exactly one light-emitting layer B composed of exactly two sublayers.

In another embodiment of the invention, the electroluminescent device according to the invention includes at least one light-emitting layer B composed of more than two sublayers. In another embodiment of the invention, each light-emitting layer B included in the electroluminescent device according to the invention is composed of more than two sublayers.

In another embodiment of the invention, the electroluminescent device according to the invention includes exactly one light-emitting layer B composed of more than two sublayers.

In one embodiment of the invention, each light-emitting layer B of the organic electroluminescent device according to the invention includes exactly one, exactly two, or exactly three sublayers.

It is understood that different sublayers of a light-emitting layer B do not necessarily all include the same materials or even the same materials in the same ratios.

It is understood that different sublayers of a light-emitting layer B are adjacent to each other.

In one embodiment of the invention, at least one sublayer includes exactly one TADF material E^Band exactly one phosphorescence material P^B.

In one embodiment of the invention, an electroluminescent device according to the invention includes at least one light-emitting layer B composed of more than one sublayers, wherein at least one sublayer does not include a TADF material E^B, a phosphorescence material P^B, or a small FWHM emitter S^B.

In one embodiment of the invention, an electroluminescent device according to the invention includes at least one light-emitting layer B composed of one or more than one sublayers, wherein at least one sublayer includes at least one host material H^B, exactly one phosphorescence material P^B, and exactly one small FWHM emitter S^B.

In one embodiment of the invention, an electroluminescent device according to the invention includes at least one light-emitting layer B composed of one or more than one sublayers, wherein at least one sublayer includes at least one host material H^B, exactly one TADF material E^B, exactly one phosphorescence material P^B, and exactly one small FWHM emitter S^B.

In one embodiment of the invention, an electroluminescent device according to the invention includes at least one light-emitting layer B composed of one or more than one sublayers, wherein at least one sublayer includes exactly one host material H^B, exactly one TADF material E^B, exactly one phosphorescence material P^B, and exactly one small FWHM emitter S^B.

In one embodiment of the invention, an electroluminescent device according to the invention includes at least one light-emitting layer B composed of one or more than one sublayers, wherein at least one sublayer includes exactly one host material H^B, exactly one phosphorescence material P^B, and exactly one small FWHM emitter S^B.

In a preferred embodiment of the invention, an electroluminescent device according to the invention includes at least one light-emitting layer B composed of one or more than one sublayers, wherein at least one sublayer includes exactly one phosphorescence material P^B.

In a preferred embodiment of the invention, a sublayer includes exactly one TADF material E^Band a sublayer (preferably another sublayer) includes exactly one phosphorescence material P^Band exactly one small FWHM emitter S^B.

In a preferred embodiment of the invention, an electroluminescent device according to the invention includes at least one light-emitting layer B including (or consisting of) three or more than three sublayers, wherein the first sublayer B1 includes exactly one TADF material E^B, the second sublayer B2 exactly one phosphorescence material P^B, and the third sublayer B3 includes exactly one small FWHM emitter S^B.

It is understood that the sublayers of a light-emitting layer B can be fabricated in different orders, e.g., B1-B2-B3, B1-B3-B2, B2-B1-B3, B2-B3-B1, B3-B2-B1, B3-B1-B2, and with one or more different sublayers in between.

In a preferred embodiment of the invention, an electroluminescent device according to the invention includes at least one light-emitting layer B including (or consisting of) two or more than two sublayers, wherein the first sublayer B1 includes exactly one TADF material E^Band exactly one phosphorescence material P^B, and the second sublayer B2 includes exactly one small FWHM emitter S^B.

In a preferred embodiment of the invention, an electroluminescent device according to the invention includes at least one light-emitting layer B including (or consisting of) two or more than two sublayers, wherein the first sublayer B1 includes exactly one TADF material E^Band the second sublayer B2 includes exactly one phosphorescence material P^Band exactly one small FWHM emitter S^B.

In a preferred embodiment of the invention, an electroluminescent device according to the invention includes at least one light-emitting layer B including (or consisting of) two or more than two sublayers, wherein the first sublayer B1 includes exactly one phosphorescence material P^B, and the second sublayer B2 includes exactly one TADF material E^Band exactly one small FWHM emitter S^B.

In a preferred embodiment of the invention, an electroluminescent device according to the invention includes at least one light-emitting layer B including (or consisting of) two or more than two sublayers, wherein the first sublayer B1 includes exactly one small FWHM emitter S^B, and the second sublayer B2 includes exactly one TADF material E^Band exactly one phosphorescence material P^B. In a preferred embodiment, sublayers B1 and B2 are (directly) adjacent to each other, in other words, are in (direct) contact with each other.

It is understood that an organic electroluminescent device according to the invention may optionally also include one or more light-emitting layers which do not fulfill the requirements given for a light-emitting layer B in the context of the present invention. In other words: An organic electroluminescent device according to the present invention includes at least one light-emitting layer B as defined herein and may optionally include one or more additional light-emitting layers for which the requirements given herein for a light-emitting layer B do not necessarily apply. In another embodiment of the invention, at least one, but not all light-emitting layers included in an organic electroluminescent device according to the invention are light-emitting layers B as defined within the specific embodiments of the invention.

In a preferred embodiment of the invention, each light-emitting layer included in an organic electroluminescent device according to the invention is a light-emitting layer B as defined within the specific embodiments of the invention.

Composition of the Light-Emitting Layer(s) (EML) B

The (at least one) host material H^B, (at least one) phosphorescence material P^B, and the (at least one) small FWHM emitter S^Bmay be included in the organic electroluminescent device in any amount and any ratio.

In a preferred embodiment, the (at least one) host material H^B, (at least one) phosphorescence material P^B, (at least one) thermally activated delayed fluorescence (TADF) material E^B, and the (at least one) small FWHM emitter S^Bmay be included in the organic electroluminescent device in any amount and any ratio.

In a preferred embodiment of the invention, the electroluminescent device according to the invention includes at least one light-emitting layer B composed of one or more than one sublayer, wherein each of the at least one sublayer includes more of the (at least one) host material H^B(more specific: H^Pand/or H^Nand/or H^BP), than of the (at least one) small FWHM emitter S^B, according to the weight.

In a preferred embodiment of the invention, each of the at least one light-emitting layer B in an organic electroluminescent device according to the present invention includes more of the at least one TADF material E^Bthan of the at least one small FWHM emitter S^B, according to the weight.

In a preferred embodiment, in the organic electroluminescent device according to the present invention, the at least one light-emitting layer B as a whole (consisting of one (sub)layer or including more than one sublayers) includes (or consists of):

- (i) 30-99.8% by weight of one or more host materials H^B;
- (ii) 0.1-30% by weight of one or more phosphorescence materials P^B; and
- (iii) 0.1-10% by weight of one or more small FWHM emitters S^B; and optionally
- (v) 0-69.8% by weight of one or more solvents.

- (i) 30-99.8% by weight, preferably 60-99.8% by weight, of one or more host materials H^B;
- (ii) 0.1-50% by weight, preferably 0.1-30% by weight, of one or more phosphorescence materials P^B; and
- (iii) 0.1-20% by weight, preferably 0.1-10% by weight, of one or more small FWHM emitters S^B; and optionally
- (v) 0-3% by weight of one or more solvents.

- (i) 30-99.8% by weight of one or more host materials H^B;
- (ii) 0.1-20% by weight of one or more phosphorescence materials P^B; and
- (iii) 0.1-10% by weight of one or more small FWHM emitters S^B; and optionally
- (v) 0-69.8% by weight of one or more solvents.

- (i) 30-99.8% by weight, preferably 70-99.8% by weight, of one or more host materials H^B;
- (ii) 0.1-20% by weight of one or more phosphorescence materials P^B; and
- (iii) 0.1-50% by weight, preferably 0.1-10% by weight, of one or more small FWHM emitters S^B; and optionally
- (v) 0-3% by weight of one or more solvents.

In a preferred embodiment, wherein E^Bis optional, in an organic electroluminescent device according to the present invention, the (at least one) light-emitting layer B as a whole (consisting of one (sub)layer or including more than one sublayers) includes (or consists of):

- (i) 30-99.8% by weight of one or more host materials H^B;
- (ii) 0.1-30% by weight of one or more phosphorescence materials P^B; and
- (iii) 0.1-10% by weight of one or more small FWHM emitters S^B; and optionally
- (iv) 0-69.8 by weight of one or more TADF material E^B; and optionally
- (v) 0-69.8% by weight of one or more solvents.

- (i) 30-99.8% by weight of one or more host materials H^B;
- (ii) 0.1-30% by weight of one or more phosphorescence materials P^B; and
- (iii) 0.1-10% by weight of one or more small FWHM emitters S^B; and optionally
- (iv) 0-69.8 by weight of one or more TADF material E^B; and optionally
- (v) 0-3% by weight of one or more solvents.

- (i) 30-99.8% by weight of one or more host materials H^B;
- (ii) 0.1-20% by weight of one or more phosphorescence materials P^B; and
- (iii) 0.1-10% by weight of one or more small FWHM emitters S^B; and optionally
- (iv) 0-69.8 by weight of one or more TADF materials E^B; and optionally
- (v) 0-69.8% by weight of one or more solvents.

- (i) 30-99.8% by weight of one or more host materials H^B;
- (ii) 0.1-20% by weight of one or more phosphorescence materials P^B; and
- (iii) 0.1-10% by weight of one or more small FWHM emitters S^B; and optionally
- (iv) 0-69.8 by weight of one or more TADF materials E^B; and optionally
- (v) 0-3% by weight of one or more solvents.

In an even more preferred embodiment, wherein E^Bis necessary, in an organic electroluminescent device according to the present invention, the (at least one) light-emitting layer B as a whole (consisting of one (sub)layer or including more than one sublayers) includes (or consists of):

- (i) 30-87.8% by weight of one or more host materials H^B;
- (ii) 0.1-30% by weight of one or more phosphorescence materials P^B; and
- (iii) 0.1-10% by weight of one or more small FWHM emitters S^B; and
- (iv) 12-40% by weight of one or more TADF materials E^B; and optionally
- (v) 0-57.8% by weight of one or more solvents.

- (i) 30-87.8% by weight of one or more host materials H^B;
- (ii) 0.1-30% by weight of one or more phosphorescence materials P^B; and
- (iii) 0.1-10% by weight of one or more small FWHM emitters S^B; and
- (iv) 12-40% by weight of one or more TADF materials E^B; and optionally
- (v) 0-3% by weight of one or more solvents.

- (i) 30-87.8% by weight of one or more host materials H^B(also designated as host compound H^B);
- (ii) 0.1-20% by weight of one or more phosphorescence material P^B; and
- (iii) 0.1-10% by weight of one or more small FWHM emitters S^B; and
- (iv) 12-40% by weight of one or more TADF materials E^B; and optionally
- (v) 0-57.8% by weight of one or more solvents.

- (i) 30-87.8% by weight of one or more host materials H^B(also designated as host compound H^B);
- (ii) 0.1-20% by weight of one or more phosphorescence material P^B; and
- (iii) 0.1-10% by weight of one or more small FWHM emitters S^B; and
- (iv) 12-40% by weight of one or more TADF materials E^B; and optionally
- (v) 0-3% by weight of one or more solvents.

In one embodiment of the invention, the at least one, preferably each, light-emitting layer B includes less than or equal to 5% by weight of one or more phosphorescence material P^B.

In one embodiment of the invention, the organic electroluminescent device includes at least one light-emitting layer B including:

- (i) at least one host material H^B, which has a lowermost excited singlet state energy level E(S1^H) and a lowermost excited triplet state energy level E(T1^H);
- (ii) at least one phosphorescence material P^B, which has a lowermost excited singlet state energy level E(S1^P) and a lowermost excited triplet state energy level E(T1^P); and
- (iii) at least one small full width at half maximum (FWHM) emitter S^B, which has a lowermost excited singlet state energy level E(S1^S) and a lowermost excited triplet state energy level E(T1^S), wherein S^Bemits light with a full width at half maximum (FWHM) of less than or equal to 0.25 eV;
- (iv) at least one thermally activated delayed fluorescence (TADF) material E^B, which has a lowermost excited singlet state energy level E(S1^E) and a lowermost excited triplet state energy level E(T1^E),
- wherein the relations expressed by the following formulas (1) and (2) apply:

E(T1^H)>E(T1^P) (1)

E(T1^P)>E(S1^S) (2), and

- wherein the (at least one), preferably each, light-emitter layer B includes less than or equal to 5% by weight of one or more phosphorescence material P^B.

In one embodiment of the invention, the at least one, preferably each, light-emitting layer B includes or consists of:

- (i) 30-96.8% by weight of one or more host materials H^B(also designated as host compound H^B);
- (ii) 0.1-5% by weight of one or more phosphorescence materials P^B; and
- (iii) 0.1-10% by weight of one or more small FWHM emitters S^B;
- (iv) 3-69.8% by weight of one or more TADF materials E^B; and optionally
- (v) 0-66.8% by weight of one or more solvents.

In one embodiment of the invention, the at least one, preferably each, light-emitting layer B includes or consists of:

- (i) 30-96.8% by weight of one or more host materials H^B(also designated as host compound H^B);
- (ii) 0.1-5% by weight of one or more phosphorescence materials P^B; and
- (iii) 0.1-10% by weight of one or more small FWHM emitters S^B;
- (iv) 3-69.8% by weight of one or more TADF materials E^B; and optionally
- (v) 0-3% by weight of one or more solvents.

In one embodiment of the invention, the at least one, preferably each, light-emitting layer B includes or consists of:

- (i) 30-89.8% by weight of one or more host materials H^B;
- (ii) 0.1-5% by weight of one or more phosphorescence materials P^B; and
- (iii) 0.1-10% by weight of one or more small FWHM emitters S^B;
- (iv) 10-40% by weight of one or more TADF materials E^B; and optionally
- (v) 0-59.8% by weight of one or more solvents.

In one embodiment of the invention, the at least one, preferably each, light-emitting layer B includes or consists of:

- (i) 30-89.8% by weight of one or more host materials H^B;
- (ii) 0.1-5% by weight of one or more phosphorescence materials P^B; and
- (iii) 0.1-10% by weight of one or more small FWHM emitters S^B;
- (iv) 10-52% by weight of one or more TADF materials E^B; and optionally
- (v) 0-3% by weight of one or more solvents.

In one embodiment of the invention, the at least one, preferably each, light-emitting layer B includes or consists of:

- (i) 30-96.8% by weight of one or more host materials H^B;
- (ii) 0.1-5% by weight of one or more phosphorescence materials P^B; and
- (iii) 0.1-5% by weight of one or more small FWHM emitters S^B;
- (iv) 3-69.8% by weight of one or more TADF materials E^B; and optionally
- (v) 0-66.8% by weight of one or more solvents.

In one embodiment of the invention, the at least one, preferably each, light-emitting layer B includes or consists of:

- (i) 30-96.8% by weight of one or more host materials H^B;
- (ii) 0.1-5% by weight of one or more phosphorescence materials P^B; and
- (iii) 0.1-5% by weight of one or more small FWHM emitters S^B;
- (iv) 3-69.8% by weight of one or more TADF materials E^B; and optionally
- (v) 0-3% by weight of one or more solvents.

In a particularly preferred embodiment of the invention, the at least one, preferably each, light-emitting layer B includes or consists of:

- (i) 30-87.8% by weight of one or more host materials H^B;
- (ii) 0.1-5% by weight of one or more phosphorescence materials P^B; and
- (iii) 0.1-5% by weight of one or more small FWHM emitters S^B;
- (iv) 12-40% by weight of one or more TADF materials E^B; and optionally
- (v) 0-57.8% by weight of one or more solvents.

In a particularly preferred embodiment of the invention, the at least one, preferably each, light-emitting layer B includes or consists of:

- (i) 30-87.8% by weight of one or more host materials H^B;
- (ii) 0.1-5% by weight of one or more phosphorescence materials P^B; and
- (iii) 0.1-5% by weight of one or more small FWHM emitters S^B;
- (iv) 12-57% by weight of one or more TADF materials E^B; and optionally
- (v) 0-3% by weight of one or more solvents.

In one embodiment of the invention, the at least one, preferably each, light-emitting layer B includes less than or equal to 3% by weight, of phosphorescence material P^B.

In one embodiment of the invention, the at least one, preferably each, light-emitting layer B includes less than or equal to 1% by weight, of phosphorescence material P^B.

In one embodiment of the invention, the at least one, preferably each, light-emitting layer B includes 10-40% by weight of one or more TADF material E^B.

In one embodiment of the invention, the mass ratio of the (at least one) small full width at half maximum (FWHM) emitter S^Bto the (at least one) phosphorescence material P^B(S^B:P^B) is ≥1.

In one embodiment of the invention, in at least one light-emitting layer B, the mass ratio of the at least one small full width at half maximum (FWHM) emitter S^Bto the at least one phosphorescence material P^B(S^B:P^B) is ≥1. In one embodiment of the invention, in each light-emitting layer B, the mass ratio of the at least one small full width at half maximum (FWHM) emitter S^Bto the at least one phosphorescence material P^B(S^B:P^B) is ≥1.

In one embodiment of the invention, the mass ratio of the (at least one) small full width at half maximum (FWHM) emitter S^Bto the (at least one) phosphorescence material P^B(S^B:P^B) is ≤1.

In one embodiment of the invention, in at least one light-emitting layer B, the mass ratio of the at least one small full width at half maximum (FWHM) emitter S^Bto the at least one phosphorescence material P^B(S^B:P^B) is <1. In one embodiment of the invention, in each light-emitting layer B, the mass ratio of the at least one small full width at half maximum (FWHM) emitter S^Bto the at least one phosphorescence material P^B(S^B:P^B) is <1.

In one embodiment of the invention, the mass ratio S^B:P^Bis in the range of from 1:1 to 30:1, in the range of from 1.5:1 to 25:1, in the range from 2:1 to 20:1, in the range of from 4:1 to 15:1, in the range of from 5:1 to 12:1, or in the range of from 10:1 to 11:1. For example, the mass ratio S^B:P^Bis in the range of (approximately) 20:1, 15:1, 12:1, 10:1, 8:1, 5:1, 4:1, 2:1, 1.5:1 or 1:1.

In one embodiment of the invention, the mass ratio of the (at least one) small full width at half maximum (FWHM) emitter S^Bto the (at least one) phosphorescence material P^B(S^B:P^B) is <1.

In one embodiment of the invention, the mass ratio P^B:S^Bis in the range of from 1:1 to 30:1, in the range of from 1.5:1 to 25:1, in the range from 2:1 to 20:1, in the range of from 4:1 to 15:1, in the range of from 5:1 to 12:1, or in the range of from 10:1 to 11:1. For example, the mass ratio S^B:P^Bis in the range of (approximately) 20:1, 15:1, 12:1, 10:1, 8:1, 5:1, 4:1, 2:1, 1.5:1 or 1:1.

As stated previously, it is understood that different sublayers of a light-emitting layer B do not necessarily all include the same materials or even the same materials in the same ratios.

S1-T1-Energy Relations

In one embodiment of the invention, the relations expressed by the following formulas (1) and (2) apply:

E(T1^H)>E(T1^P) (1)

E(T1^P)>E(S1^S) (2),

- accordingly, the lowermost excited triplet state T1^Hof each host material H^Bis higher in energy than the lowermost excited triplet state T1^Pof each phosphorescence material P^B, and the lowermost excited triplet state T1^Pof each phosphorescence material P^Bis higher in energy than the lowermost excited singlet state S1^Sof each small FWHM emitter S^B.

In one embodiment, the aforementioned relations expressed by formulas (1) and (2) apply to materials included in the same light-emitting layer B of the organic electroluminescent device according to the invention.

An organic electroluminescent device including at least one light-emitting layer B including:

- (i) at least one host material H^B, which has a lowermost excited singlet state energy level E(S1^H) and a lowermost excited triplet state energy level E(T1^H); and
- (ii) at least one phosphorescence material P^B, which has a lowermost excited singlet state energy level E(S1^P) and a lowermost excited triplet state energy level E(T1^P); and
- (iii) at least one small full width at half maximum (FWHM) emitter S^B, which has a lowermost excited singlet state energy level E(S1^S) and a lowermost excited triplet state energy level E(T1^S), wherein S^Bemits light with a full width at half maximum (FWHM) of less than or equal to 0.25 eV; and
- (iv) at least one thermally activated delayed fluorescence (TADF) material E^B, which has a lowermost excited singlet state energy level E(S1^E) and a lowermost excited triplet state energy level E(T1^E),
- wherein the relations expressed by the following formulas (1) and (2) apply:

E(T1^H)>E(T1^P) (1)

E(T1^P)>E(S1^S) (2).

In one embodiment, the aforementioned relations expressed by formulas (1) and (2) apply to materials included in any of the at least one light-emitting layers B of the organic electroluminescent device according to the invention.

In a preferred embodiment of the invention, the relations expressed by the following formulas (3) and (4) apply.

E(T1^H)>E(T1^E) (3)

E(T1^E)>E(T1^P) (4),

- accordingly, the lowermost excited triplet state T1^Hof each host material H^Bis higher in energy than the lowermost excited triplet state T1^Eof each TADF material E^B, and the lowermost excited triplet state T1^Eof each TADF material E^Bis higher in energy than the lowermost excited triplet state T1^Pof each phosphorescence material P^B.

In one embodiment, the aforementioned relations expressed by formulas (3) and (4) apply to materials included in any of the at least one light-emitting layers B of the organic electroluminescent device according to the invention. In one embodiment, the aforementioned relations expressed by formulas (3) and (4) apply to materials included in the same light-emitting layer B of the organic electroluminescent device according to the invention.

In an alternative embodiment of the invention, the relations expressed by the following formulas (5) and (6) apply.

E(T1^P)>E(T1^E) (5)

E(S1^E)>E(S1^S) (6),

- accordingly, the lowermost excited triplet state T1^Pof each phosphorescence material P^Bis higher in energy than the lowermost excited triplet state T1^Eof each TADF material E^B, and the lowermost excited singlet state S1^Eof each TADF material E^Bis higher in energy the lowermost excited singlet state S1^Sof each small FWHM emitter S^B.

In one embodiment, the aforementioned relations expressed by formulas (5) and (6) apply to materials included in any of the at least one light-emitting layers B of the organic electroluminescent device according to the invention. In one embodiment, the aforementioned relations expressed by formulas (5) and (6) apply to materials included in the same light-emitting layer B of the organic electroluminescent device according to the invention.

In a preferred embodiment of the invention, the relations expressed by the following formulas (1) to (4) apply:

E(T1^H)>E(T1^P) (1)

E(T1^P)>E(S1^S) (2)

E(T1^H)>E(S1^E) (3)

E(T1^E)>E(T1^P) (4).

In one embodiment, the aforementioned relations expressed by formulas (1) to (4) apply to materials included in any of the at least one light-emitting layers B of the organic electroluminescent device according to the invention. In one embodiment, the aforementioned relations expressed by formulas (1) to (4) apply to materials included in the same light-emitting layer B of the organic electroluminescent device according to the invention.

In one embodiment of the invention, the difference (in energy) between the lowermost excited triplet state T1^Pof each phosphorescence material P^Band the lowermost excited triplet state T1^Eof each TADF material E^Bis smaller than 0.3 eV: E(T1^P)−E(T1^E)<0.3 eV, and E(T1^E)−E(T1^P)<0.3 eV, respectively.

In one embodiment of the invention, in at least one of the one or more light-emitting layers B, the difference in energy between the lowermost excited triplet state T1^Pof the at least one, preferably each, phosphorescence material P^Band the lowermost excited triplet state T1^Eof the at least one, preferably each, TADF material E^Bis smaller than 0.3 eV: E(T1^P)−E(T1^E)<0.3 eV, and E(T1^E)−E(T1^P)<0.3 eV, respectively.

In one embodiment of the invention, in each of the one or more light-emitting layers B, the difference in energy between the lowermost excited triplet state T1^Pof the at least one, preferably each, phosphorescence material P^Band the lowermost excited triplet state T1^Eof the at least one, preferably each, TADF material E^Bis smaller than 0.3 eV: E(T1^P)−E(T1^E)<0.3 eV, and E(T1^E)−E(T1^P)<0.3 eV, respectively.

In one embodiment of the invention, the relation expressed by the following formula (4) applies:

E(T1^E)>E(T1^P) (4).

In one embodiment, the aforementioned relation expressed by formula (4) applies to materials included in any of the at least one light-emitting layers B of the organic electroluminescent device according to the invention. In one embodiment, the aforementioned relation expressed by formula (4) applies to materials included in the same light-emitting layer B of the organic electroluminescent device according to the invention.

In a preferred embodiment of the invention, the difference in energy between the lowermost excited triplet state T1^Eof the at least one, preferably each, TADF material E^Band the lowermost excited triplet state T1^Pof the at least one, preferably each, phosphorescence material P^Bis smaller than 0.2 eV: E(T1^E)−E(T1^P)<0.2 eV.

In a preferred embodiment of the invention, in at least one of the one or more light-emitting layers B, the difference in energy between the lowermost excited triplet state T1^Eof the at least one, preferably each, TADF material E^Band the lowermost excited triplet state T1^Pof the at least one, preferably each, phosphorescence material P^Bis smaller than 0.2 eV: E(T1^E)−E(T1^P)<0.2 eV.

In a preferred embodiment of the invention, in each of the one or more light-emitting layers B, the difference in energy between the lowermost excited triplet state T1^Eof the at least one, preferably each, TADF material E^Band the lowermost excited triplet state T1^Pof the at least one, preferably each, phosphorescence material P^Bis smaller than 0.2 eV: E(T1^E)−E(T1^P)<0.2 eV.

In a preferred embodiment of the invention, the difference in energy between the lowermost excited triplet state T1^Pof the at least one, preferably each, phosphorescence material P^Band lowermost excited singlet state S1^S(energy level E(S1^S)) of the at least one, preferably each, small full width at half maximum (FWHM) emitter S^Bis smaller than 0.3 eV: E(T1^P)−E(S1^S)<0.3 eV.

In a preferred embodiment of the invention, in at least one of the one or more light-emitting layers B, the difference in energy between the lowermost excited triplet state T1^Pof the at least one, preferably each, phosphorescence material P^Band lowermost excited singlet state S1^Sof the at least one, preferably each, small full width at half maximum (FWHM) emitter S^Bis smaller than 0.3 eV: E(T1^P)−E(S1^S)<0.3 eV.

In a preferred embodiment of the invention, in each of the one or more light-emitting layers B, the difference in energy between the lowermost excited triplet state T1^Pof at least one, preferably each phosphorescence material P^Band lowermost excited singlet state S1^Sof at least one, preferably each small full width at half maximum (FWHM) emitter S^Bis smaller than 0.3 eV: E(T1^P)−E(S1^S)<0.3 eV.

In a preferred embodiment of the invention, the difference in energy between the lowermost excited triplet state T1^Pof each phosphorescence material P^Band lowermost excited singlet state S1^S(energy level E(S1^S)) of each small full width at half maximum (FWHM) emitter S^Bis smaller than 0.2 eV: E(T1^P)−E(S1^S)<0.2 eV.

In a preferred embodiment of the invention, in each of the one or more light-emitting layers B, the difference in energy between the lowermost excited triplet state T1^Pof the at least one, preferably each, phosphorescence material P^Band lowermost excited singlet state S1^Sof the at least one, preferably each, small full width at half maximum (FWHM) emitter S^Bis smaller than 0.2 eV: E(T1^P)−E(S1^S)<0.2 eV.

HOMO-LUMO Energies

In a preferred embodiment of the invention, the following requirements are fulfilled:

- (i) each host material H^Bhas a highest occupied molecular orbital HOMO(H^B) having an energy E^HOMO(H^B); and
- (ii) each phosphorescence material P^Bhas a highest occupied molecular orbital HOMO(P^B) having an energy E^HOMO(P^B); and
- (iii) each small full width at half maximum (FWHM) emitter S^Bhas a highest occupied molecular orbital HOMO(S^B) having an energy E^HOMO(S^B);
- wherein the relations expressed by the following formulas (10) and (11) apply:

E
^HOMO(P^B)>E^HOMO(H^B) (10)

E
^HOMO(P^B)>E^HOMO(S^B) (11).

In one embodiment, the aforementioned relations expressed by formulas (10) and (11) apply to materials included in any of the at least one light-emitting layers B of the organic electroluminescent device according to the invention. In one embodiment, the aforementioned relations expressed by formulas (10) and (11) apply to materials included in the same light-emitting layer B of the organic electroluminescent device according to the invention.

In one embodiment of the invention, the highest occupied molecular orbital HOMO(S^B) of each small full width at half maximum (FWHM) emitter S^Bhaving an energy E^HOMO(S^B) is higher in energy than the highest occupied molecular orbital HOMO(H^B) of each host material H^Bhaving an energy E^HOMO(H^B):

E
^HOMO(S^B)>E^HOMO(H^B).

In one embodiment of the invention, in at least one of the one or more light-emitting layers B, the highest occupied molecular orbital HOMO(S^B) of the at least one, preferably each, small full width at half maximum (FWHM) emitter S^Bhaving an energy E^HOMO(S^B) is higher in energy than the highest occupied molecular orbital HOMO(H^B) of the at least one, preferably each, host material H^Bhaving an energy E^HOMO(H^B):

E
^HOMO(S^B)>E^HOMO(H^B).

In one embodiment of the invention, in each of the at least one light-emitting layers B, the highest occupied molecular orbital HOMO(S^B) of the at least one, preferably each, small full width at half maximum (FWHM) emitter S^Bhaving an energy E^HOMO(S^B) is higher in energy than the highest occupied molecular orbital HOMO(H^B) of the at least one, preferably each, host material H^Bhaving an energy E^HOMO(H^B):

E
^HOMO(S^B)>E^HOMO(H^B).

In one embodiment of the invention, the highest occupied molecular orbital HOMO(S^B) of each small full width at half maximum (FWHM) emitter S^Bhaving an energy E^HOMO(S^B) is higher in energy than the highest occupied molecular orbital HOMO(E^B) of each TADF material E^Bhaving an energy E^HOMO(E^B):

E
^HOMO(S^B)>E^HOMO(E^B).

In one embodiment of the invention, in at least one of the one or more light-emitting layers B, the highest occupied molecular orbital HOMO(S^B) of the at least one, preferably each, small full width at half maximum (FWHM) emitter S^Bhaving an energy E^HOMO(S^B) is higher in energy than the highest occupied molecular orbital HOMO(E^B) of the at least one, preferably each, TADF material E^Bhaving an energy E^HOMO(E^B):

E
^HOMO(S^B)>E^HOMO(E^B).

In one embodiment of the invention, in each of the at least one light-emitting layers B, the highest occupied molecular orbital HOMO(S^B) of the at least one, preferably each, small full width at half maximum (FWHM) emitter S^Bhaving an energy E^HOMO(S^B) is higher in energy than the highest occupied molecular orbital HOMO(E^B) of the at least one, preferably each, TADF material E^Bhaving an energy E^HOMO(E^B):

E
^HOMO(S^B)>E^HOMO(E^B).

In one embodiment of the invention, the highest occupied molecular orbital HOMO(P^B) of the at least one, preferably each, phosphorescence material P^Bhaving an energy E^HOMO(P^B) is higher in energy than the highest occupied molecular orbital HOMO(E^B) of the at least one, preferably each, TADF material E^Bhaving an energy E^HOMO(E^B):

E
^HOMO(P^B)>E^HOMO(E^B).

In one embodiment of the invention, in at least one of the one or more light-emitting layers B, the highest occupied molecular orbital HOMO(P^B) of the at least one, preferably each, phosphorescence material P^Bhaving an energy E^HOMO(P^B) is higher in energy than the highest occupied molecular orbital HOMO(E^B) of the at least one, preferably each, TADF material E^Bhaving an energy E^HOMO(E^B):

E
^HOMO(P^B)>E^HOMO(E^B).

In one embodiment of the invention, in each of the at least one light-emitting layers B, the highest occupied molecular orbital HOMO(P^B) of the at least one, preferably each, phosphorescence material P^Bhaving an energy E^HOMO(P^B) is higher in energy than the highest occupied molecular orbital HOMO(E^B) of the at least one, preferably each, TADF material E^Bhaving an energy E^HOMO(E^B):

E
^HOMO(P^B)>E^HOMO(E^B).

In one embodiment of the invention, the highest occupied molecular orbital HOMO(P^B) of the at least one, preferably each, phosphorescence material P^Bhaving an energy E^HOMO(P^B) is higher in energy than the highest occupied molecular orbital HOMO(H^B) of the at least one, preferably each, host material H^Bhaving an energy E^HOMO(H^B):

E
^HOMO(P^B)>E^HOMO(H^B).

In one embodiment of the invention, in at least one of the one or more light-emitting layers B, the highest occupied molecular orbital HOMO(P^B) of the at least one, preferably each, phosphorescence material P^Bhaving an energy E^HOMO(P^B) is higher in energy than the highest occupied molecular orbital HOMO(H^B) of the at least one, preferably each, host material H^Bhaving an energy E^HOMO(H^B):

E
^HOMO(P^B)>E^HOMO(H^B).

In one embodiment of the invention, in each of the at least one light-emitting layers B, the highest occupied molecular orbital HOMO(P^B) of the at least one, preferably each, phosphorescence material P^Bhaving an energy E^HOMO(P^B) is higher in energy than the highest occupied molecular orbital HOMO(H^B) of the at least one, preferably each, host material H^Bhaving an energy E^HOMO(H^B):

E
^HOMO(P^B)>E^HOMO(H^B).

In one embodiment of the invention, the highest occupied molecular orbital HOMO(P^B) of the at least one, preferably each, phosphorescence material P^Bhaving an energy E^HOMO(P^B) is higher in energy than the highest occupied molecular orbital HOMO(S^B) of the at least one, preferably each, small full width at half maximum (FWHM) emitter S^Bhaving an energy E^HOMO(S^B):

E
^HOMO(P^B)>E^HOMO(S^B).

In one embodiment of the invention, in at least one of the one or more light-emitting layers B, the highest occupied molecular orbital HOMO(P^B) of the at least one, preferably each, phosphorescence material P^Bhaving an energy E^HOMO(P^B) is higher in energy than the highest occupied molecular orbital HOMO(S^B) of the at least one, preferably each, small full width at half maximum (FWHM) emitter S^Bhaving an energy E^HOMO(S^B):

E
^HOMO(P^B)>E^HOMO(S^B).

In one embodiment of the invention, in each of the at least one light-emitting layers B, the highest occupied molecular orbital HOMO(P^B) of the at least one, preferably each, phosphorescence material P^Bhaving an energy E^HOMO(P^B) is higher in energy than the highest occupied molecular orbital HOMO(S^B) of the at least one, preferably each, small full width at half maximum (FWHM) emitter S^Bhaving an energy E^HOMO(S^B):

E
^HOMO(P^B)>E^HOMO(S^B)

In one embodiment of the invention, the difference (in energy) between the highest occupied molecular orbital HOMO(P^B) of the at least one, preferably each, phosphorescence material P^Bhaving an energy E^HOMO(P^B) and the highest occupied molecular orbital HOMO(S^B) of the at least one, preferably each, small full width at half maximum (FWHM) emitter S^Bhaving an energy E^HOMO(S^B) is smaller than 0.3 eV:

E
^HOMO(P^B)−E^HOMO(S^B)<0.3 eV.

In one embodiment of the invention, in at least one of the one or more light-emitting layers B, the difference in energy between the highest occupied molecular orbital HOMO(P^B) of the at least one, preferably each, phosphorescence material P^Bhaving an energy E^HOMO(P^B) and the highest occupied molecular orbital HOMO(S^B) of the at least one, preferably each, small full width at half maximum (FWHM) emitter S^Bhaving an energy E^HOMO(S^B) is smaller than 0.3 eV:

E
^HOMO(P^B)−E^HOMO(S^B)<0.3 eV.

In one embodiment of the invention, in each of the at least one light-emitting layers B, the difference in energy between the highest occupied molecular orbital HOMO(P^B) of the at least one, preferably each, phosphorescence material P^Bhaving an energy E^HOMO(P^B) and the highest occupied molecular orbital HOMO(S^B) of the at least one, preferably each, small full width at half maximum (FWHM) emitter S^Bhaving an energy E^HOMO(S^B) is smaller than 0.3 eV:

E
^HOMO(P^B)−E^HOMO(S^B)<0.3 eV.

In one embodiment of the invention, the difference (in energy) between the highest occupied molecular orbital HOMO(P^B) of each phosphorescence material P^Bhaving an energy E^HOMO(P^B) and the highest occupied molecular orbital HOMO(S^B) of each small full width at half maximum (FWHM) emitter S^Bhaving an energy E^HOMO(S^B) is smaller than 0.2 eV: E^HOMO(P^B)−E^HOMO(S^B)<0.2 eV.

E
^HOMO(P^B)−E^HOMO(S^B)<0.2 eV.

In a preferred embodiment of the invention, the difference (in energy) between the highest occupied molecular orbital HOMO(P^B) of the at least one, preferably each, phosphorescence material P^Bhaving an energy E^HOMO(P^B) and the highest occupied molecular orbital HOMO(S^B) of the at least one, preferably each, small full width at half maximum (FWHM) emitter S^Bhaving an energy E^HOMO(S^B) is larger than 0.0 eV and smaller than 0.3 eV:

0.0 eV<E^HOMO(P^B)−E^HOMO(S^B)<0.3 eV.

In a preferred embodiment of the invention, in at least one of the one or more light-emitting layers B, the difference in energy between the highest occupied molecular orbital HOMO(P^B) of the at least one, preferably each, phosphorescence material P^Bhaving an energy E^HOMO(P^B) and the highest occupied molecular orbital HOMO(S^B) of the at least one, preferably each, small full width at half maximum (FWHM) emitter S^Bhaving an energy E^HOMO(S^B) is larger than 0.0 eV and smaller than 0.3 eV:

0.0 eV<E^HOMO(P^B)−E^HOMO(S^B)<0.3 eV.

In a preferred embodiment of the invention, in each of the at least one light-emitting layers B, the difference in energy between the highest occupied molecular orbital HOMO(P^B) of the at least one, preferably each, phosphorescence material P^Bhaving an energy E^HOMO(P^B) and the highest occupied molecular orbital HOMO(S^B) of the at least one, preferably each, small full width at half maximum (FWHM) emitter S^Bhaving an energy E^HOMO(S^B) is larger than 0.0 eV and smaller than 0.3 eV:

0.0 eV<E^HOMO(P^B)−E^HOMO(S^B)<0.3 eV.

0.1 eV≤E^HOMO(P^B)−E^HOMO(S^B)≤0.8 eV.

In a preferred embodiment of the invention, the following requirements are fulfilled:

- (i) each host material H^Bhas a lowest unoccupied molecular orbital LUMO(H^B) having an energy E^LUMO(H^B); and
- (ii) each phosphorescence material P^Bhas a lowest unoccupied molecular orbital LUMO(P^B) having an energy E^LUMO(P^B); and
- (iii) each small full width at half maximum (FWHM) emitter S^Bhas a lowest unoccupied molecular orbital LUMO(S^B) having an energy E^LUMO(S^B); and
- (iv) each thermally activated delayed fluorescence (TADF) material E^Bhas a lowest unoccupied molecular orbital LUMO(E^B) having an energy E^LUMO(E^B),
- wherein the relations expressed by the following formulas (12) to (13) apply:

E
^LUMO(E^B)<E^LUMO(H^B) (12)

E
^LUMO(E^B)<E^LUMO(P^B) (13).

In one embodiment, the aforementioned relations expressed by formulas (12) and (13) apply to materials included in any of the at least one light-emitting layers B of the organic electroluminescent device according to the invention. In one embodiment, the aforementioned relations expressed by formulas (12) and (13) apply to materials included in the same light-emitting layer B of the organic electroluminescent device according to the invention.

In one embodiment of the invention, the electroluminescent device including a light-emitting layer B composed of one or more sublayers, wherein the one or more sublayers of the light-emitting layer B include:

- (i) a host material H^Bhaving a lowest unoccupied molecular orbital LUMO(H^B) having an energy E^LUMO(H^B); and
- (ii) a phosphorescence material P^Bhaving a lowest unoccupied molecular orbital LUMO(P^B) having an energy E^LUMO(P^B); and
- (iii) a small full width at half maximum (FWHM) emitter S^Bhaving a lowest unoccupied molecular orbital LUMO(S^B) having an energy E^LUMO(S^B); and
- (iv) a thermally activated delayed fluorescence (TADF) material E^Bhaving a lowest unoccupied molecular orbital LUMO(E^B) having an energy E^LUMO(E^B),
- wherein the relations expressed by the following formulas (12) to (14) apply:

E
^LUMO(E^B)<E^LUMO(H^B) (12)

E
^LUMO(E^B)<E^LUMO(P^B) (13)

E
^LUMO(E^B)<E^LUMO(S^B) (14).

In one embodiment, the aforementioned relations expressed by formulas (12) to (14) apply to materials included in any of the at least one light-emitting layers B of the organic electroluminescent device according to the invention. In one embodiment, the aforementioned relations expressed by formulas (12) to (14) apply to materials included in the same light-emitting layer B of the organic electroluminescent device according to the invention.

In one embodiment of the invention, the relations expressed by the following formulas (10) to (13) apply:

E
^HOMO(P^B)>E^HOMO(H^B) (10)

E
^HOMO(P^B)>E^HOMO(S^B) (11)

E
^LUMO(E^B)<E^LUMO(H^B) (12)

E
^LUMO(E^B)<E^LUMO(P^B) (13).

In one embodiment, the aforementioned relations expressed by formulas (10) to (13) apply to materials included in any of the at least one light-emitting layers B of the organic electroluminescent device according to the invention. In one embodiment, the aforementioned relations expressed by formulas (10) to (13) apply to materials included in the same light-emitting layer B of the organic electroluminescent device according to the invention.

In one embodiment of the invention, the relations expressed by the following formulas (10) to (14) apply:

E
^HOMO(P^B)>E^HOMO(H^B) (10)

E
^HOMO(P^B)>E^HOMO(S^B) (11)

E
^LUMO(E^B)<E^LUMO(H^B) (12)

E
^LUMO(E^B)<E^LUMO(P^B) (13)

E
^LUMO(E^B)<E^LUMO(S^B) (14).

In one embodiment, the aforementioned relations expressed by formulas (10) to (14) apply to materials included in any of the at least one light-emitting layers B of the organic electroluminescent device according to the invention. In one embodiment, the aforementioned relations expressed by formulas (10) to (14) apply to materials included in the same light-emitting layer B of the organic electroluminescent device according to the invention.

In one embodiment of the invention, the lowest unoccupied molecular orbital LUMO(S^B) of the at least one, preferably each, small full width at half maximum (FWHM) emitter S^Bhaving an energy E^LUMO(S^B) is higher in energy than the lowest unoccupied molecular orbital LUMO(E^B) of the at least one, preferably each, TADF material E^Bhaving an energy E^LUMO(E^B):

E
^LUMO(S^B)>E^LUMO(E^B).

In one embodiment of the invention, in at least one of the one or more light-emitting layers B, the lowest unoccupied molecular orbital LUMO(S^B) of the at least one, preferably each, small full width at half maximum (FWHM) emitter S^Bhaving an energy E^LUMO(S^B) is higher in energy than the lowest unoccupied molecular orbital LUMO(E^B) of the at least one, preferably each, TADF material E^Bhaving an energy E^LUMO(E^B):

E
^LUMO(S^B)>E^LUMO(E^B).

In one embodiment of the invention, in each of the at least one light-emitting layers B, the lowest unoccupied molecular orbital LUMO(S^B) of the at least one, preferably each, small full width at half maximum (FWHM) emitter S^Bhaving an energy E^LUMO(S^B) is higher in energy than the lowest unoccupied molecular orbital LUMO(E^B) of the at least one, preferably each, TADF material E^Bhaving an energy E^LUMO(E^B):

E
^LUMO(S^B)>E^LUMO(E^B).

In one embodiment of the invention, the difference in energy between the lowest unoccupied molecular orbital LUMO(S^B) of the at least one, preferably each, small full width at half maximum (FWHM) emitter S^Bhaving an energy E^LUMO(S^B) and the lowest unoccupied molecular orbital LUMO(E^B) of the at least one, preferably each, TADF material E^Bhaving an energy E^LUMO(E^B) is smaller than 0.3 eV:

E
^LUMO(S^B)−E^LUMO(E^B)<0.3 eV.

In one embodiment of the invention, in at least one of the one or more light-emitting layers B, the difference in energy between the lowest unoccupied molecular orbital LUMO(S^B) of the at least one, preferably each, small full width at half maximum (FWHM) emitter S^Bhaving an energy E^LUMO(S^B) and the lowest unoccupied molecular orbital LUMO(E^B) of the at least one, preferably each, TADF material E^Bhaving an energy E^LUMO(E^B) is smaller than 0.3 eV:

E
^LUMO(S^B)−E^LUMO(E^B)<0.3 eV.

In one embodiment of the invention, in each of the at least one light-emitting layers B, the difference in energy between the lowest unoccupied molecular orbital LUMO(S^B) of the at least one, preferably each, small full width at half maximum (FWHM) emitter S^Bhaving an energy E^LUMO(S^B) and the lowest unoccupied molecular orbital LUMO(E^B) of the at least one, preferably each, TADF material E^Bhaving an energy E^LUMO(E^B) is smaller than 0.3 eV:

E
^LUMO(S^B)−E^LUMO(E^B)<0.3 eV.

In one embodiment of the invention, the difference (in energy) between the lowest unoccupied molecular orbital LUMO(S^B) of the at least one, preferably each, small full width at half maximum (FWHM) emitter S^Bhaving an energy E^LUMO(S^B) and the lowest unoccupied molecular orbital LUMO(E^B) of the at least one, preferably each, TADF material E^Bhaving an energy E^LUMO(E^B) is smaller than 0.2 eV:

E
^LUMO(S^B)−E^LUMO(E^B)<0.2 eV.

0.0 eV<E^LUMO(S^B)−E^LUMO(E^B)<0.3 eV.

In one embodiment of the invention, the lowest unoccupied molecular orbital LUMO(P^B) of each phosphorescence material P^Bhaving an energy E^LUMO(P^B) is higher in energy than the lowest unoccupied molecular orbital LUMO(E^B) of each TADF material E^Bhaving an energy E^LUMO(E^B):

E
^LUMO(P^B)>E^LUMO(E^B).

In one embodiment of the invention, in at least one of the one or more light-emitting layers B, the lowest unoccupied molecular orbital LUMO(P^B) of the at least one, preferably each, phosphorescence material P^Bhaving an energy E^LUMO(P^B) is higher in energy than the lowest unoccupied molecular orbital LUMO(E^B) of the at least one, preferably each, TADF material E^Bhaving an energy E^LUMO(E^B):

E
^LUMO(P^B)>E^LUMO(E^B).

In one embodiment of the invention, in each of the at least one light-emitting layers B, the lowest unoccupied molecular orbital LUMO(P^B) of the at least one, preferably each, phosphorescence material P^Bhaving an energy E^LUMO(P^B) is higher in energy than the lowest unoccupied molecular orbital LUMO(E^B) of the at least one, preferably each, TADF material E^Bhaving an energy E^LUMO(E^B):

E
^LUMO(P^B)>E^LUMO(E^B).

In one embodiment of the invention, the lowest unoccupied molecular orbital LUMO(H^B) of the at least one, preferably each, host material H^Bhaving an energy E^LUMO(H^B) is higher in energy than the lowest unoccupied molecular orbital LUMO(E^B) of the at least one, preferably each, TADF material E^Bhaving an energy E^LUMO(E^B):

E
^LUMO(H^B)>E^LUMO(E^B).

In one embodiment of the invention, in at least one of the one or more light-emitting layers B, the lowest unoccupied molecular orbital LUMO(H^B) of the at least one, preferably each, host material H^Bhaving an energy E^LUMO(H^B) is higher in energy than the lowest unoccupied molecular orbital LUMO(E^B) of the at least one, preferably each, TADF material E^Bhaving an energy E^LUMO(E^B):

E
^LUMO(H^B)>E^LUMO(E^B).

In one embodiment of the invention, in each of the at least one light-emitting layers B, the lowest unoccupied molecular orbital LUMO(H^B) of the at least one, preferably each, host material H^Bhaving an energy E^LUMO(H^B) is higher in energy than the lowest unoccupied molecular orbital LUMO(E^B) of the at least one, preferably each, TADF material E^Bhaving an energy E^LUMO(E^B):

E
^LUMO(H^B)>E^LUMO(E^B).

Relations of Emission Maxima

In one embodiment of the invention, the relations expressed by formulas (16) and (17) apply:

|E^λmax(P^B)−E^λmax(S^B)|<0.30 eV (16),

|E^λmax(E^B)−E^λmax(S^B)|<0.30 eV (17),

- which means: The difference in energy between the energy of the emission maximum E^λmax(P^B) of a phosphorescence material P^Bin the context of the present invention given in electron volt (eV) and the energy of the emission maximum E^λmax(S^B) of a small FWHM emitter S^Bin the context of the present invention given in electron volt (eV) is smaller than 0.30 eV. And: The difference in energy between the energy of the emission maximum E^λmax(E^B) of a TADF material E^Bin the context of the present invention given in electron volt (eV) and the energy of the emission maximum E^λmax(S^B) of a small FWHM emitter S^Bin the context of the present invention given in electron volt (eV) is smaller than 0.30 eV.

In one embodiment, the aforementioned relations expressed by formulas (16) and (17) apply to materials included in any of the at least one light-emitting layers B of the organic electroluminescent device according to the invention. In one embodiment, the aforementioned relations expressed by formulas (16) and (17) apply to materials included in the same light-emitting layer B of the organic electroluminescent device according to the invention.

An organic electroluminescent device including at least one light-emitting layer B which is composed of one or more sublayers, wherein the one or more sublayers are adjacent to each other and as a whole contain:

- (i) at least one host material H^B; and
- (ii) at least one phosphorescence material P^B, which has emission maximum λ_max(P^B) with an energy E^λmax(P^B); and
- (iii) at least one small full width at half maximum (FWHM) emitter S^B, which has emission maximum λ_max(S^B) with an energy E^λmax(S^B), wherein S^Bemits light with a full width at half maximum (FWHM) of less than or equal to 0.25 eV; and
- (iv) at least one thermally activated delayed fluorescence (TADF) material E^B, which has emission maximum λ_max(E^B) with an energy E^λmax(E^B),
- wherein the one or more sublayers which are located at the outer surface of the light-emitting layer B contain at least one (emitter) material selected from the group consisting of phosphorescence material P^B, small FWHM emitter S^B, and TADF material E^B, wherein the relations expressed by the following formulas (16) and (17) apply:

|E^λmax(P^B)−E^λmax(S^B)|<0.30 eV (16),

|E^λmax(E^B)−E^λmax(S^B)|<0.30 eV (17).

In a preferred embodiment of the invention, the relations expressed by formulas (18) and (19) apply:

|E^λmax(P^B)−E^λmax(S^B)|<0.20 eV (18),

|E^λmax(E^B)−E^λmax(S^B)|<0.20 eV (19),

- which means: The difference in energy between the energy of the emission maximum E^λmax(P^B) of a phosphorescence material P^Bin the context of the present invention given in electron volt (eV) and the energy of the emission maximum E^λmax(S^B) of a small FWHM emitter S^Bin the context of the present invention given in electron volt (eV) is smaller than 0.20 eV. And: The difference in energy between the energy of the emission maximum E^λmax(E^B) of a TADF material E^Bin the context of the present invention given in electron volt (eV) and the energy of the emission maximum E^λmax(S^B) of a small FWHM emitter S^Bin the context of the present invention given in electron volt (eV) is smaller than 0.20 eV.

In one embodiment, the aforementioned relations expressed by formulas (18) and (19) apply to materials included in any of the at least one light-emitting layers B of the organic electroluminescent device according to the invention. In one embodiment, the aforementioned relations expressed by formulas (18) and (19) apply to materials included in the same light-emitting layer B of the organic electroluminescent device according to the invention.

One embodiment of the invention refers to an organic electroluminescent device, wherein

- (ii) the at least one phosphorescence material P^B, has an emission maximum λ_max(P^B) with an energy E^λmax(P^B); and
- (iii) the at least one small full width at half maximum (FWHM) emitter S^B, has an emission maximum λ_max(S^B) with an energy E^λmax(S^B), wherein S^Bemits light with a full width at half maximum (FWHM) of less than or equal to 0.25 eV; and
- (iv) the at least one thermally activated delayed fluorescence (TADF) material E^B, has an emission maximum λ_max(E^B) with an energy E^λmax(E^B),
- wherein (18) and (19) apply:

|E^λmax(P^B)−E^λmax(S^B)|<0.20 eV (18),

|E^λmax(E^B)−E^λmax(S^B)|<0.20 eV (19).

In an even more preferred embodiment of the invention, the relations expressed by formulas (20) and (21) apply:

|E^λmax(P^B)−E^λmax(S^B)|<0.1 eV (20),

|E^λmax(E^B)−E^λmax(S^B)|<0.10 eV (21),

- which means: The difference in energy between the energy of the emission maximum E^λmax(P^B) of a phosphorescence material P^Bin the context of the present invention given in electron volt (eV) and the energy of the emission maximum E^λmax(S^B) of a small FWHM emitter S^Bin the context of the present invention given in electron volt (eV) is smaller than 0.10 eV. And: The difference in energy between the energy of the emission maximum E^λmax(E^B) of a TADF material E^Bin the context of the present invention given in electron volt (eV) and the energy of the emission maximum E^λmax(S^B) of a small FWHM emitter S^Bin the context of the present invention given in electron volt (eV) is smaller than 0.10 eV.

In one embodiment, the aforementioned relations expressed by formulas (20) and (21) apply to materials included in any of the at least one light-emitting layers B of the organic electroluminescent device according to the invention. In one embodiment, the aforementioned relations expressed by formulas (20) and (21) apply to materials included in the same light-emitting layer B of the organic electroluminescent device according to the invention.

In one embodiment of the invention, the relation expressed by formula (22) applies:

E
^λmax(P^B)>E^λmax(S^B) (22),

- which means that the energy of the emission maximum E^λmax(P^B) of a phosphorescence material P^Bin the context of the present invention given in electron volt (eV) is larger than the energy of the emission maximum E^λmax(S^B) of a small FWHM emitter S^Bin the context of the present invention given in electron volt (eV).

In one embodiment, the aforementioned relation expressed by formula (22) applies to materials included in any of the at least one light-emitting layers B of the organic electroluminescent device according to the invention. In one embodiment, the aforementioned relation expressed by formula (22) applies to materials included in the same light-emitting layer B of the organic electroluminescent device according to the invention.

In one embodiment of the invention, the relation expressed by formula (22-a) applies:

E
^λmax(E^B)>E^λmax(S^B) (22-a),

- which means that the energy of the emission maximum E^λmax(E^B) of a TADF material E^Bin the context of the present invention given in electron volt (eV) is larger than the energy of the emission maximum E^λmax(S^B) of a small FWHM emitter S^Bin the context of the present invention given in electron volt (eV).

In one embodiment, the aforementioned relation expressed by formula (22-a) applies to materials included in any of the at least one light-emitting layers B of the organic electroluminescent device according to the invention. In one embodiment, the aforementioned relation expressed by formula (22-a) applies to materials included in the same light-emitting layer B of the organic electroluminescent device according to the invention.

Device Colors & Performance

A further embodiment of the present invention relates to an electroluminescent device (e.g., an OLED), which emits light at a distinct color point. According to the present invention, the electroluminescent device (e.g., OLED) emits light with a narrow emission band (small full width at half maximum (FWHM)). In a preferred embodiment, the electroluminescent device (e.g., OLED) according to the invention emits light with a FWHM of the main emission peak of below 0.25 eV, more preferably of below 0.20 eV, even more preferably of below 0.15 eV or even below 0.13 eV.

A further embodiment of the present invention relates to an electroluminescent device (e.g., an OLED), which exhibits an external quantum efficiency at 1000 cd/m²(nits) of more than 10%, more preferably of more than 13%, more preferably of more than 15%, even more preferably of more than 18% or even more than 20% and exhibits an emission maximum between 500 nm and 560 nm.

A further embodiment of the present invention relates to an electroluminescent device (e.g., an OLED) which exhibits an external quantum efficiency at 1000 cd/m²of more than 10%, more preferably of more than 13%, more preferably of more than 15%, even more preferably of more than 18% or even more than 20% and exhibits an emission maximum between 515 nm and 540 nm.

In a preferred embodiment, the electroluminescent device (e.g., an OLED) exhibits a LT95 value at constant current density J₀=15 mA/cm²of more than 100 h, preferably more than 200 h, more preferably more than 400 h, even more preferably more than 750 h or even more than 1000 h.

A further embodiment of the present invention relates to an electroluminescent device (e.g., an OLED), which emits light with CIEx and CIEy color coordinates close to the CIEx (=0.170) and CIEy (=0.797) color coordinates of the primary color green (CIEx=0.170 and CIEy=0.797) as defined by ITU-R Recommendation BT.2020 (Rec. 2020) and thus may be suited for the use in Ultra High Definition (UHD) displays, e.g., UHD-TVs. In this context, the term “close to” refers to the ranges of CIEx and CIEy coordinates provided at the end of this paragraph. In commercial applications, typically top-emitting (top-electrode is typically transparent) devices are used, whereas test devices as used throughout the present application represent bottom-emitting devices (bottom-electrode and substrate are transparent). Accordingly, a further aspect of the present invention relates to an electroluminescent device (e.g., an OLED), whose emission exhibits a CIEx color coordinate of between 0.15 and 0.45 preferably between 0.15 and 0.35, more preferably between 0.15 and 0.30 or even more preferably between 0.15 and 0.25 or even between 0.15 and 0.20 and/or a CIEy color coordinate of between 0.60 and 0.92, preferably between 0.65 and 0.90, more preferably between 0.70 and 0.88 or even more preferably between 0.75 and 0.86 or even between 0.79 and 0.84.

A further embodiment of the present invention relates to an OLED, which emits light with CIEx and CIEy color coordinates close to the CIEx (=0.265) and CIEy (=0.65) color coordinates of the primary color green (CIEx=0.265 and CIEy=0.65) as defined by DCIP3. In this context, the term “close to” refers to the ranges of CIEx and CIEy coordinates provided at the end of this paragraph. In commercial applications, typically top-emitting (top-electrode is typically transparent) devices are used, whereas test devices as used throughout the present application represent bottom-emitting devices (bottom-electrode and substrate are transparent). Accordingly, a further aspect of the present invention relates to an OLED, whose bottom emission exhibits a CIEx color coordinate of between 0.2 and 0.45 preferably between 0.2 and 0.35 or more preferably between 0.2 and 0.30 or even more preferably between 0.24 and 0.28 or even between 0.25 and 0.27 and/or a CIEy color coordinate of between 0.60 and 0.9, preferably between 0.6 and 0.8, more preferably between 0.60 and 0.70 or even more preferably between 0.62 and 0.68 or even between 0.64 and 0.66.

A further embodiment of the present invention relates to an electroluminescent device (e.g., an OLED), which exhibits an external quantum efficiency at 1000 cd/m²of more than 10%, more preferably of more than 13%, more preferably of more than 15%, even more preferably of more than 18% or even more than 20% and/or exhibits an emission maximum between 420 nm and 500 nm, preferably between 430 nm and 490 nm, more preferably between 440 nm and 480 nm, even more preferably between 450 nm and 470 nm and/or exhibits a LT80 value at 500 cd/m²of more than 100 h, preferably more than 200 h, more preferably more than 400 h, even more preferably more than 750 h or even more than 1000 h.

A further aspect of the present invention relates to an OLED, which emits light with CIEx and CIEy color coordinates close to the CIEx (=0.131) and CIEy (=0.046) color coordinates of the primary color blue (CIEx=0.131 and CIEy=0.046) as defined by ITU-R Recommendation BT.2020 (Rec. 2020) and thus is suited for the use in Ultra High Definition (UHD) displays, e.g., UHD-TVs. In commercial applications, typically top-emitting (top-electrode is transparent) devices are used, whereas test devices as used throughout the present application represent bottom-emitting devices (bottom-electrode and substrate are transparent). The CIEy color coordinate of a blue device can be reduced by up to a factor of two, when changing from a bottom- to a top-emitting device, while the CIEx remains nearly unchanged (Okinaka et al., Society for Information Display International Symposium Digest of Technical Papers, 2015, 46(1):312-313, DOI:10.1002/sdtp.10480). Accordingly, a further aspect of the present invention relates to an OLED, whose emission exhibits a CIEx color coordinate of between 0.02 and 0.30, preferably between 0.03 and 0.25, more preferably between 0.05 and 0.20 or even more preferably between 0.08 and 0.18 or even between 0.10 and 0.15 and/or a CIEy color coordinate of between 0.00 and 0.45, preferably between 0.01 and 0.30, more preferably between 0.02 and 0.20 or even more preferably between 0.03 and 0.15 or even between 0.04 and 0.10.

A further aspect of the present invention relates to an electroluminescent device (e.g., an OLED), which exhibits an external quantum efficiency at 1000 cd/m²of more than 8%, more preferably of more than 10%, more preferably of more than 13%, even more preferably of more than 15% or even more than 20% and/or exhibits an emission maximum between 590 nm and 690 nm, preferably between 610 nm and 665 nm, even more preferably between 620 nm and 640 nm and/or exhibits a LT80 value at 500 cd/m²of more than 100 h, preferably more than 200 h, more preferably more than 400 h, even more preferably more than 750 h or even more than 1000 h. Accordingly, a further aspect of the present invention relates to an OLED, whose emission exhibits a CIEy color coordinate of more than 0.25, preferably more than 0.27, more preferably more than 0.29 or even more preferably more than 0.30.

A further embodiment of the present invention relates to an electroluminescent device (e.g., an OLED), which emits light with CIEx and CIEy color coordinates close to the CIEx (=0.708) and CIEy (=0.292) color coordinates of the primary color red (CIEx=0.708 and CIEy=0.292) as defined by ITU-R Recommendation BT.2020 (Rec. 2020) and thus is suited for the use in Ultra High Definition (UHD) displays, e.g., UHD-TVs. In this context, the term “close to” refers to the ranges of CIEx and CIEy coordinates provided at the end of this paragraph. In commercial applications, typically top-emitting (top-electrode is transparent) devices are used, whereas test devices as used throughout the present application represent bottom-emitting devices (bottom-electrode and substrate are transparent). Accordingly, a further aspect of the present invention relates to an OLED, whose emission exhibits a CIEx color coordinate of between 0.60 and 0.88, preferably between 0.61 and 0.83, more preferably between 0.63 and 0.78 or even more preferably between 0.66 and 0.76 or even between 0.68 and 0.73 and/or a CIEy color coordinate of between 0.25 and 0.70, preferably between 0.26 and 0.55, more preferably between 0.27 and 0.45 or even more preferably between 0.28 and 0.40 or even between 0.29 and 0.35.

Accordingly, a further aspect of the present invention relates to an electroluminescent device (e.g., an OLED), which exhibits an external quantum efficiency at 14500 cd/m²of more than 10%, more preferably of more than 13%, more preferably of more than 15%, even more preferably of more than 17% or even more than 20% and/or exhibits an emission maximum between 590 nm and 690 nm, preferably between 610 nm and 665 nm, even more preferably between 620 nm and 640 nm.

One of the purposes of interest of an organic electroluminescent device may be the generation of light. Thus, the present invention further relates to a method for generating light of a desired wavelength range, including the step of providing an organic electroluminescent device according to any the present invention.

Accordingly, a further aspect of the present invention relates to a method for generating light of a desired wavelength range, including the steps of

- (i) providing an organic electroluminescent device according to the present invention; and
- (ii) applying an electrical current to said organic electroluminescent device.

A further aspect of the present invention relates to a process of making the organic electroluminescent devices by assembling the elements described above. The present invention also relates to a method for generating green light, in particular by using said organic electroluminescent device.

A further aspect of the invention relates to an organic electroluminescent device, wherein (at least) one, preferably exactly one, of the relations expressed by the following formulas (23) to (25) applies to materials included in the same light-emitting layer B:

440 nm<λ_max(S^B)<470 nm (23)

510 nm<λ_max(S^B)<550 nm (24)

610 nm<λ_max(S^B)<665 nm (25),

- wherein λ_max(S^B) is the emission maximum of the at least one, preferably each, small FWHM emitter S^Band is given in nanometers (nm).

In one embodiment of the invention at least one, preferably exactly one, of the relations expressed by the following formulas (23) to (25) applies to materials included in any of the at least one light-emitting layers B of the organic electroluminescent device according to the invention.

A further aspect of the invention relates to a method for generating light, including the steps of:

- (i) providing an organic electroluminescent device according to the present invention
- (ii) applying an electrical current to said organic electroluminescent device.

A further aspect of the invention relates to a method for generating light, including the steps of:

- (i) providing an organic electroluminescent device according to the present invention
- (ii) applying an electrical current to said organic electroluminescent device,
- wherein the method is for generating light at a wavelength range selected from one of the following wavelength ranges:
- (i) from 510 nm to 550 nm, or
- (ii) from 440 nm to 470 nm, or
- (iii) from 610 nm to 665 nm.

The skilled artisan understands that the at least one TADF material E^Band the at least one phosphorescence material P^B(vide infra) may be used as emitters in organic electroluminescent devices. However, preferably, in the organic electroluminescent device according to the present invention, the main function of the at least one TADF material E^Band the at least one phosphorescence material P^Bis not emitting light. In a preferred embodiment, upon applying a voltage (and electrical current), the organic electroluminescent device according to the invention emits light, wherein this emission is mainly (i.e., to an extent of more than 50%, preferably of more than 60%, more preferably of more than 70%, even more preferably of more than 80% or even of more than 90%) attributed to fluorescent light emitted by the at least one small FWHM emitter S^B. In consequence, the organic electroluminescent device according to the present invention preferably also displays a narrow emission, which is expressed by a small FWHM of the main emission peak of below 0.25 eV, more preferably of below 0.20 eV, even more preferably of below 0.15 eV or even below 0.13 eV.

In a preferred embodiment of the invention, the relation expressed by the following formula (26) applies:

$\frac{F W H M^{D}}{F W H M^{S B}} \leq 1.5 0,$

- wherein
- FWHM^Drefers to the full width at half maximum (FWHM) in electron volts (eV) of the main emission peak of the organic electroluminescent device according to the present invention; and
- FWHM^SBrepresents the FWHM in electron volts (eV) of the photoluminescence spectrum (fluorescence spectrum, measured at room temperature, (i.e., approximately 20° C.) of a spin coated film of the one or more small FWHM emitters S^Bin the one or more host materials H^Bused in the light-emitting layer (EML) of the organic electroluminescent device with the FWHM of FWHM^D. This is to say that the spin coated film from which FWHM^SBis determined preferably includes the same small FWHM emitter or emitters S^Bin the same weight ratios as the light-emitting layer B of the organic electroluminescent device.

If, for example, the light-emitting layer B includes two small FWHM emitters S^Bwith a concentration of 1% by weight each, the spin coated film preferably also includes 1% by weight of each of the two small FWHM emitters S^B. In this exemplary case, the matrix material of the spin coated film would amount to 98% by weight of the spin coated film. This matrix material of the spin coated film may be selected to reflect the weight-ratio of the host materials H^Bincluded in the light-emitting layer B of the organic electroluminescent device. If, in the aforementioned example, the light-emitting layer B includes a single host material H^B, this host material would preferably be the sole matrix material of the spin coated film. If, however, in the aforementioned example, the light-emitting layer B includes two host materials H^B, one with a content of 60% by weight and the other with a content of 20% by weight (i.e., in a ratio of 3:1), the aforementioned matrix material of the spin coated film (including 1% by weight of each of the two small FWHM emitters S^B) would preferably be a 3:1-mixture of the two host materials H^Bas present in the EML.

If more than one light-emitting layer B is contained in an organic electroluminescent device according to the present invention, the relation expressed by the aforementioned formula (26) preferably applies to all light-emitting layers B included in the device.

In one embodiment, for at least one light-emitting layer B of the organic electroluminescent device according to the present invention, the aforementioned ratio FWHM^D:FWHM^SBis equal to or smaller than 1.50, preferably 1.40, even more preferably 1.30, still even more preferably 1.20, or even 1.10.

In one embodiment, for each light-emitting layer B of the organic electroluminescent device according to the present invention, the aforementioned ratio FWHM^D:FWHM^SBis equal to or smaller than 1.50, preferably 1.40, even more preferably 1.30, still even more preferably 1.20, or even 1.10.

It should be noted that for the selection of fluorescent emitters for the use as small FWHM emitters S^Bin the context of the present invention, the FWHM value may be determined as described in a later subchapter of this text (briefly: preferably from a spin coated film of the respective emitter in poly(methyl methacrylate) PMMA with a concentration of 1-5% by weight, in particular 2% by weight, or from a solution, vide infra). This is to say that the FWHM values of the exemplary small FWHM emitters S^Blisted in Table 1^Smay not be understood as FWHM^SBvalues in the context of equation (26) and the associated preferred embodiments of the present invention.

The examples and claims further illustrate the invention.

Host Material(s) H^B

According to the invention, any of the one or more host materials H^Bincluded in any of the at least one light-emitting layer B may be a p-host H^Pexhibiting high hole mobility, an n-host H^Nexhibiting high electron mobility, or a bipolar host material H^BPexhibiting both, high hole mobility and high electron mobility.

An n-host exhibiting high electron mobility in the context of the present invention preferably has a LUMO energy E^LUMO(H^N) equal to or smaller than −2.50 eV (E^LUMO(H^N)≤−2.50 eV). Preferably, E^LUMO(H^N)≤−2.60 eV, more preferably E^LUMO(H^N)≤−2.65 eV, and even more preferably, E^LUMO(H^N)≤−2.70 eV. The LUMO is the lowest unoccupied molecular orbital. The energy of the LUMO is determined as described in a later subchapter of this text.

A p-host exhibiting high hole mobility in the context of the present invention preferably has a HOMO energy E^HOMO(H^P) equal to or higher than −6.30 eV (E^HOMO(H^P)≥−6.30 eV), preferably E^HOMO(H^P)≥−5.90 eV, more preferably E^HOMO(H^P)≥−5.70 eV and even more preferably E^HOMO(H^P)≥−5.40 eV or even E^HOMO(H^P)≥−2.60 eV. The HOMO is the highest occupied molecular orbital. The energy of the HOMO is determined as described in a later subchapter of this text.

In one embodiment of the invention, each host material H^Bis a p-host H^Pwhich has a HOMO energy E^HOMO(H^P) equal to or higher than −6.30 eV (E^HOMO(H^P)≥−6.30 eV), preferably E^HOMO(H^P)≥−5.90 eV, more preferably E^HOMO(H^P)≥−5.70 eV, and even more preferably E^HOMO(H^P)≥−5.40 eV. The HOMO is the highest occupied molecular orbital. The energy of the HOMO is determined as described in a later subchapter of this text.

In one embodiment of the invention, the at least one, preferably each p-host H^Phas a HOMO energy E^HOMO(H^P) smaller than −5.60 eV.

In one embodiment of the invention, the organic electroluminescent device including at least one light-emitting layer B which is composed of one or more sublayers, wherein the one or more sublayers are adjacent to each other and as a whole contain:

- (i) at least one host material H^B, which has a lowermost excited singlet state energy level E(S1^H) and a lowermost excited triplet state energy level E(T1^H);
- (ii) at least one phosphorescence material P^B, which has a lowermost excited singlet state energy level E(S1^P) and a lowermost excited triplet state energy level E(T1^P); and
- (iii) at least one small full width at half maximum (FWHM) emitter S^B, which has a lowermost excited singlet state energy level E(S1^S) and a lowermost excited triplet state energy level E(T1^S), wherein S^Bemits light with a full width at half maximum (FWHM) of less than or equal to 0.25 eV; and optionally
- (iv) at least one thermally activated delayed fluorescence (TADF) material E^B, which has a lowermost excited singlet state energy level E(S1^E) and a lowermost excited triplet state energy level E(T1^E),
- wherein the one or more sublayers which are located at the outer surface of the light-emitting layer B contain at least one (emitter) material selected from the group consisting of phosphorescence material P^B, small FWHM emitter S^B, and TADF material E^B,
- wherein the at least one host material H^Bhas a highest occupied molecular orbital HOMO(H^B) having an energy E^HOMO(H^B), which is smaller than −5.60 eV, preferably wherein each host material H^Bhas a highest occupied molecular orbital HOMO(H^B) having an energy E^HOMO(H^B), which is smaller than −5.60 eV.

A bipolar host exhibiting high electron mobility in the context of the present invention preferably has a LUMO energy E^LUMO(H^BP) equal to or smaller than −2.50 eV (E^LUMO(H^BP)≤−2.50 eV). Preferably, E^LUMO(H^BP)≤−2.60 eV, more preferably E^LUMO(H^BP)≤−2.65 eV, and even more preferably, E^LUMO(H^BP)≤−2.70 eV. The LUMO is the lowest unoccupied molecular orbital. The energy of the LUMO is determined as described in a later subchapter of this text.

A bipolar host exhibiting high hole mobility in the context of the present invention preferably has a HOMO energy E^HOMO(H^BP) equal to or higher than −6.30 eV (E^HOMO(H^BP)≥−6.30 eV), preferably E^HOMO(H^BP)≥−5.90 eV. More, preferably, E^HOMO(H^BP)≥−5.70 eV and still even more preferably E^HOMO(H^BP)≥−5.40 eV. The HOMO is the highest occupied molecular orbital. The energy of the HOMO is determined as described in a later subchapter of this text.

In one embodiment of the invention, a bipolar host material H^BP, preferably each bipolar host material H^BPfulfills both of the following requirements:

- (i) It has a LUMO energy E^LUMO(H^P) equal to or smaller than −2.50 eV (E^LUMO(H^P)≤−2.50 eV). Preferably, E^LUMO(H^P)≤−2.60 eV, more preferably E^LUMO(H^P)≤−2.65 eV, and even more preferably, E^LUMO(H^P)≤−2.70 eV. The LUMO is the lowest unoccupied molecular orbital. The energy of the LUMO is determined as described in a later subchapter of this text.
- (ii) It has a HOMO energy E^HOMO(H^P) equal to or higher than −6.30 eV (E^HOMO(H^P)≥−6.30 eV), preferably E^HOMO(H^P)≥−5.90 eV. More preferably, E^HOMO(H^P)≥−5.70 eV and still even more preferably E^HOMO(H^P)≥−5.40 eV. The HOMO is the highest occupied molecular orbital. The energy of the HOMO is determined as described in a later subchapter of this text.

The person skilled in the art knows which materials are suitable host materials for use in organic electroluminescent devices such as those of the present invention. See for example: Y. Tao, C. Yang, J. Quin, Chemical Society Reviews 2011, 40, 2943, DOI: 10.1039/C0CS00160K; K. S. Yook, J. Y. Lee, The Chemical Record 2015, 16(1), 159, DOI: 10.1002/tcr.201500221; T. Chatterjee, K.-T. Wong, Advanced Optical Materials 2018, 7(1), 1800565, DOI: 10.1002/adom.201800565;

Q. Wang, Q.-S. Tian, Y.-L. Zhang, X. Tang, L.-S. Liao, Journal of Materials Chemistry C 2019, 7, 11329, DOI: 10.1039/C9TC03092A.

Furthermore, for example, US2006006365 (A1), US2006208221 (A1), US2005069729 (A1), EP1205527 (A1), US2009302752 (A1), US20090134784 (A1), US2009302742 (A1), US2010187977 (A1), US2010187977 (A1), US2012068170 (A1), US2012097899 (A1), US2006121308 (A1), US2006121308 (A1), US2009167166 (A1), US2007176147 (A1), US2015322091 (A1), US2011105778 (A1), US2011201778 (A1), US2011121274 (A1), US2009302742 (A1), US2010187977 (A1), US2010244009 (A1), US2009136779 (A1), EP2182040 (A2), US2012202997 (A1), US2019393424 (A1), US2019393425 (A1), US2020168819 (A1), US2020079762 (A1), and US2012292576 (A1) disclose host materials that may be used in organic electroluminescent devices according to the present invention. It is understood that this does not imply that the present invention is limited to organic electroluminescent devices including host materials disclosed in the cited references. It is also understood that any host materials used in the state of the art may also be suitable host materials H^Bin the context of the present invention.

In one embodiment of the invention, each light-emitting layer B of an organic electroluminescent device according to the invention includes one or more p-hosts H^P. In one embodiment of the invention, each light-emitting layer B of an organic electroluminescent device according to the invention includes only a single host material and this host material is a p-host H^P.

In one embodiment of the invention, each light-emitting layer B of an organic electroluminescent device according to the invention includes one or more n-hosts H^N. In another embodiment of the invention, each light-emitting layer B of an organic electroluminescent device according to the invention includes only a single host material and this host material is an n-host H^N.

In one embodiment of the invention, each light-emitting layer B of an organic electroluminescent device according to the invention includes one or more bipolar hosts H^BP. In one embodiment of the invention, each light-emitting layer B of an organic electroluminescent device according to the invention includes only a single host material and this host material is a bipolar host H^BP.

In another embodiment of the invention, at least one light-emitting layer B of an organic electroluminescent device according to the invention includes at least two different host materials H^B. In this case, the more than one host materials H^Bpresent in the respective light-emitting layer B may either all be p-hosts H^Por all be n-hosts H^N, or all be bipolar hosts H^BP, but may also be a combination thereof.

It is understood that, if an organic electroluminescent device according to the invention includes more than one light-emitting layer B, any of them may, independently of the one or more other light-emitting layers B, include either one host material H^Bor more than one host materials H^Bfor which the above-mentioned definitions apply. It is further understood that different light-emitting layers B included in an organic electroluminescent device according to the invention do not necessarily all include the same materials or even the same materials in the same concentrations.

It is understood that, if a light-emitting layer B of an organic electroluminescent device according to the invention is composed of more than one sublayer, any of them may, independently of the one or more other sublayers, include either one host material H^Bor more than one host materials H^Bfor which the above-mentioned definitions apply. It is further understood that different sublayers of a light-emitting layer B included in an organic electroluminescent device according to the invention do not necessarily all include the same materials or even the same materials in the same concentrations.

If included in the same light-emitting layer B of an organic electroluminescent device according to the invention, at least one p-host H^Pand at least one n-host H^Nmay optionally form an exciplex. The person skilled in the art knows how to choose pairs of H^Pand H^N, which form an exciplex and the selection criteria, including HOMO- and/or LUMO-energy level requirements of H^Pand H^N. This is to say that, in case exciplex formation may be aspired, the highest occupied molecular orbital (HOMO) of the p-host material H^Pmay be at least 0.20 eV higher in energy than the HOMO of the n-host material H^Nand the lowest unoccupied molecular orbital (LUMO) of the p-host material H^Pmay be at least 0.20 eV higher in energy than the LUMO of the n-host material H^N.

In a preferred embodiment of the invention, at least one host material H^B(e.g., H^P, H^N, and/or H^BP) is an organic host material, which, in the context of the invention, means that it does not contain any transition metals. In a preferred embodiment of the invention, all host materials H^B(H^P, H^N, and/or H^BP) in the electroluminescent device of the present invention are organic host materials, which, in the context of the invention, means that they do not contain any transition metals. Preferably, at least one host material H^B, more preferably all host materials H^B(H^P, H^Nand/or H^BP) predominantly consist of the elements hydrogen (H), carbon (C), and nitrogen (N), but may for example also include oxygen (O), boron (B), silicon (Si), fluorine (F), and bromine (Br).

In one embodiment of the invention, each host material H^Bis a p-host H^P.

In a preferred embodiment of the invention, a p-host H^P, optionally included in any of the at least one light-emitting layer B as a whole (consisting of one (sub)layer or including more than one sublayers), includes or consists of:

- one first chemical moiety, including or consisting of a structure according to any of the formulas H^P-I, H^P-II, H^P-III, H^P-IV, H^P-V, H^P-VI, H^P-VII, H^P-VIII, H^P-IX, and H^P-X:

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- and
- one or more second chemical moieties, each including or consisting of a structure according to any of formulas H^P-XI, H^P-XII, H^P-XIII, H^P-XIV, H^P-XV, H^P-XVI, H^P-XVI, H^P-XVIII, and H^P-XIX:

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- wherein each of the at least one second chemical moieties which is present in the p-host material H^Pis linked to the first chemical moiety via a single bond which is represented in the formulas above by a dashed line;
- wherein
- Z¹is at each occurrence independently of each other selected from the group consisting of a direct bond, C(R^II)₂, C═C(R^II)₂, C═O, C═NR^II, NR^II, O, Si(R^II)₂, S, S(O) and S(O)₂;
- R^Iis at each occurrence independently of each other a binding site of a single bond linking the first chemical moiety to a second chemical moiety or is selected from the group consisting of: hydrogen, deuterium, Me, ⁱPr, and ^tBu, and
- Ph, which is optionally substituted with one or more substituents independently of each other selected from the group consisting of: Me, ⁱPr, ^tBu, and Ph;
- wherein at least one R^Iis a binding site of a single bond linking the first chemical moiety to a second chemical moiety;
- R^IIis at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, Me, ⁱPr, ^tBu, and
- Ph, which is optionally substituted with one or more substituents independently of each other selected from the group consisting of: Me, ⁱPr, ^tBu, and Ph;
- wherein two or more adjacent substituents R^IImay optionally form an aliphatic or aromatic or heteroaromatic, carbo- or heterocyclic ring system so that the fused ring system consisting of a structure according to any of formulas H^P-XI, H^P-XII, H^P-XIII, H^P-XIV, H^P-XV, H^P-XVI, H^P-XVII, H^P-XVIII, and H^P-XIX as well as the additional rings optionally formed by adjacent substituents R^IIincludes in total 12-60 carbon atoms, preferably 14-32 carbon atoms.

In an even more preferred embodiment of the invention, Z¹is at each occurrence a direct bond and adjacent substituents R^IIdo not combine to form an additional ring system.

In a still even more preferred embodiment of the invention, a p-host H^Poptionally included in an organic electroluminescent device according to the invention is selected from the group consisting of the following structures:

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In a preferred embodiment of the invention, an n-host H^Noptionally included in any of the at least one light-emitting layer B as a whole (consisting of one (sub)layer or including more than one sublayers) includes or consists of a structure according to any of the formulas H^N-I, H^N-II, and H^N-III:

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- wherein R^IIIand R^IVare at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, Me, ⁱPr, ^tBu, CN, CF₃,
- Ph, which is optionally substituted with one or more substituents independently of each other selected from the group consisting of: Me, ⁱPr, ^tBu, and Ph; and
- a structure represented by any of the formulas H^N-IV, H^N-V, H^N-VI, H^N-VII, H^N-VIII, H^N-IX, H^N-X, H^N-XI, H^N-XII, H^N-XIII, and H^N-XIV:

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- wherein
- the dashed line indicates the binding site of a single bond connecting the structure according to any of formulas H^N-IV, H^N-V, H^N—VI, H^N-VII, H^N-VIII, H^N-IX, H^N-X, H^N-XI, H^N-XII, H^N-XIII, and H^N-XIV to a structure according to any of the formulas H^N-I, H^N-II, and H^N-III;
- X¹is oxygen (O), sulfur (S) or C(R^V)₂;
- R^Vis at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, Me, ⁱPr, ^tBu, and
- Ph, which is optionally substituted with one or more substituents independently of each other selected from the group consisting of: Me, ⁱPr, ^tBu, and Ph;
- wherein two or more adjacent substituents R^Vmay optionally form an aliphatic or aromatic or heteroaromatic, carbo- or heterocyclic ring system so that the fused ring system consisting of a structure according to any of formulas H^N-IV, H^N-V, H^N-VI, H^N-VII, H^N-VIII, H^N-IX, H^N-X, H^N-XI, H^N-XII, H^N-XIII, and H^N-XIV as well as the additional rings optionally formed by adjacent substituents R^Vincludes in total 8-60 carbon atoms, preferably 12-40 carbon atoms, more preferably 14-32 carbon atoms; and
- wherein in formulas H^N-I and H^N-II, at least one substituent R^IIIis CN.

In an even more preferred embodiment of the invention, an n-host H^Noptionally included in an organic electroluminescent device according to the invention is selected from the group consisting of the following structures:

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In one embodiment of the invention, no n-host H^Nincluded in any light-emitting layer B of an organic electroluminescent device according to the invention contains any phosphine oxide groups and, in particular, no n-host H^Nis bis[2-(diphenylphosphino)phenyl] ether oxide (DPEPO).

TADF Material(s) E^B

According to the invention, a thermally activated delayed fluorescence (TADF) material E^Bis characterized by exhibiting a ΔE_STvalue, which corresponds to the energy difference between the lowermost excited singlet state energy level E(S1^E) and the lowermost excited triplet state energy level E(T1^E), of less than 0.4 eV, preferably of less than 0.3 eV, more preferably of less than 0.2 eV, even more preferably of less than 0.1 eV, or even of less than 0.05 eV. Thus, ΔE_STof a TADF material E^Baccording to the invention is sufficiently small to allow for thermal repopulation of the lowermost excited singlet state S1^Efrom the lowermost excited triplet state T1^E(also referred to as up-intersystem crossing or reverse intersystem crossing, RISC) at room temperature (RT, i.e., (approximately) 20° C.).

Preferably, in the context of the present invention, TADF materials display both, prompt fluorescence when the emissive S1^Estate is reached in the cause of the charge carrier (hole and electron) recombination and delayed fluorescence when the emissive S1^Estate is reached via thermally activated RISC from the T1^Estate.

It is understood that a small FWHM emitter S^Bincluded in a light-emitting layer B of an organic electroluminescent device according to the invention may optionally also have a ΔE_STvalue of less than 0.4 eV and exhibit thermally activated delayed fluorescence (TADF). However, for any small FWHM emitter S^Bin the context of the invention, this is only an optional feature.

In a preferred embodiment of the invention, there is spectral overlap between the emission spectrum of at least one TADF material E^Band the absorption spectrum of at least one small FWHM emitter S^B(when both spectra are measured under comparable conditions). In this case, the at least one TADF material E^Bmay transfer energy to the at least one small FWHM emitter S^B.

According to the invention, a TADF material E^Bhas an emission maximum in the visible wavelength range of from 380 nm to 800 nm, typically measured with 10% by weight of the TADF material E^Bin poly(methyl methacrylate) PMMA at room temperature (i.e., (approximately) 20° C.).

In one embodiment of the invention, each TADF material E^Bhas an emission maximum in the deep blue wavelength range of from 380 nm to 470 nm, preferably 400 nm to 470 nm, typically measured with 10% by weight of the TADF material E^Bin poly(methyl methacrylate) PMMA at room temperature (i.e., (approximately) 20° C.).

In one embodiment of the invention, each TADF material E^Bhas an emission maximum in the green wavelength range of from 480 nm to 560 nm, preferably 500 nm to 560 nm, typically measured with 10% by weight of the TADF material E^Bin poly(methyl methacrylate) PMMA at room temperature (i.e., (approximately) 20° C.).

In one embodiment of the invention, each TADF material E^Bhas an emission maximum in the red wavelength range of from 600 nm to 665 nm, preferably 610 nm to 665 nm, typically measured with 10% by weight of the TADF material E^Bin poly(methyl methacrylate) PMMA at room temperature (i.e., (approximately) 20° C.).

In a preferred embodiment of the invention, the emission maximum (peak emission) of a TADF material E^Bis at a shorter wavelength than the emission maximum (peak emission) of a small FWHM emitter S^Bin the context of the present invention.

In a preferred embodiment of the invention, each TADF material E^Bis an organic TADF material, which, in the context of the invention, means that it does not contain any transition metals. Preferably, each TADF material E^Baccording to the invention predominantly consists of the elements hydrogen (H), carbon (C), and nitrogen (N), but may for example also include oxygen (O), boron (B), silicon (Si), fluorine (F), and bromine (Br).

In a preferred embodiment of the invention, each TADF material E^Bhas a molecular weight equal to or smaller than 800 g/mol.

In one embodiment of the invention, a TADF emitter E^Bexhibits a photoluminescence quantum yield (PLQY) equal to or higher than 30%, typically measured with 10% by weight of the TADF material E^Bin poly(methyl methacrylate) PMMA at room temperature (i.e., (approximately) 20° C.).

In a preferred embodiment of the invention, a TADF emitter E^Bexhibits a photoluminescence quantum yield (PLQY) equal to or higher than 50%, typically measured with 10% by weight of the TADF material E^Bin poly(methyl methacrylate) PMMA at room temperature (i.e., (approximately) 20° C.).

In an even more preferred embodiment of the invention, a TADF emitter E^Bexhibits a photoluminescence quantum yield (PLQY) equal to or higher than 70%, typically measured with 10% by weight of the TADF material E^Bin poly(methyl methacrylate) PMMA at room temperature (i.e., (approximately) 20° C.).

In one embodiment of the invention, the at least one, preferably each TADF material E^B

- (i) is characterized by exhibiting a ΔE_STvalue, which corresponds to the energy difference between the lowermost excited singlet state energy level E(S1^E) and the lowermost excited triplet state energy level E(T1^E), of less than 0.4 eV; and
- (ii) displays a photoluminescence quantum yield (PLQY) of more than 30%.

In one embodiment of the invention, the energy E^LUMO(E^B) of the lowest unoccupied molecular orbital LUMO(E^B) of each TADF material E^Bis smaller than −2.6 eV.

The person skilled in the art knows how to design TADF molecules E^Baccording to the invention and the structural features that such molecules typically display. Briefly, to facilitate the reverse intersystem crossing (RISC), ΔE_STis usually decreased and, in the context of the present invention, ΔE_STis smaller than 0.4 eV, as stated above. This is oftentimes achieved by designing TADF molecules E^Bso that the HOMO and LUMO are spatially largely separated on (electron-) donor and (electron-) acceptor groups, respectively. These groups are usually bulky or connected via spiro-junctions so that they are twisted and the spatial overlap of the HOMO and the LUMO is reduced. However, minimizing the spatial overlap of the HOMO and the LUMO also results in a reduction of the photoluminescence quantum yield (PLQY) of the TADF material, which is unfavorable. Therefore, in practice, these two effects are both taken into account to achieve a reduction of ΔE_STas well as a high PLQY.

One common approach for the design of TADF materials is to covalently attach one or more (electron-) donor moieties on which the HOMO is distributed and one or more (electron-) acceptor moieties on which the LUMO is distributed to the same bridge, herein referred to as linker group. A TADF material E^Bmay for example also include two or three linker groups which are bonded to the same acceptor moiety and additional donor and acceptor moieties may be bonded to each of these two or three linker groups.

One or more donor moieties and one or more acceptor moieties may also be bonded directly to each other (without the presence of a linker group).

Typical donor moieties are derivatives of diphenyl amine, carbazole, acridine, phenoxazine, and related structures.

Benzene-, biphenyl-, and to some extend also terphenyl-derivatives are common linker groups.

Nitrile groups are very common acceptor moieties in TADF molecules and known examples thereof include:

(i) Carbazolyl Dicyanobenzene Compounds

- such as 2CzPN (4,5-di(9H-carbazol-9-yl)phthalonitrile), DCzIPN (4,6-di(9H-carbazol-9-yl)isophthalonitrile), 4CzPN (3,4,5,6-tetra(9H-carbazol-9-yl)phthalonitrile), 4CzIPN (2,4,5,6-Tetra(9H-carbazol-9-yl)isophthalonitrile), 4CzTPN (2,4,5,6-tetra(9H-carbazol-9-yl)terephthalonitrile), and derivatives thereof;

(ii) Carbazolyl Cyanopyridine Compounds

- such as 4CzCNPy (2,3,5,6-tetra(9H-carbazol-9-yl)-4-cyanopyridine) and derivatives thereof;

(iii) Carbazolyl Cyanobiphenyl Compounds

- such as CNBPCz (4,4′,5,5′-tetra(9H-carbazol-9-yl)-[1,1′-biphenyl]-2,2′-dicarbonitrile), CzBPCN (4,4′,6,6′-tetra(9H-carbazol-9-yl)-[1,1′-biphenyl]-3,3′-dicarbonitrile), DDCzIPN (3,3′,5,5′-tetra(9H-carbazol-9-yl)-[1,1′-biphenyl]-2,2′,6,6′-tetracarbonitrile) and derivatives thereof;
- wherein in these materials, one or more of the nitrile groups may be replaced by fluorine (F) or trifluoromethyl (CF₃) as acceptor moieties.

Nitrogen-heterocycles such as triazine-, pyrimidine-, triazole-, oxadiazole-, thiadiazole-, heptazine-, 1,4-diazatriphenylene-, benzothiazole-, benzoxazole-, quinoxaline-, and diazafluorene-derivatives are also well-known acceptor moieties used for the construction of TADF molecules. Known examples of TADF molecules including for example a triazine acceptor include PIC-TRZ (7,7′-(6-([1,1′-biphenyl]-4-yl)-1,3,5-triazine-2,4-diyl)bis(5-phenyl-5,7-dihydroindolo[2,3-b]carbazole)), mBFCzTrz (5-(3-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-5H-benzofuro[3,2-c]carbazole), and DCzTrz (9,9′-(5-(4,6-diphenyl-1,3,5-triazin-2-yl)-1,3-phenylene)bis(9H-carbazole)).

Another group of TADF materials includes diaryl ketones such as benzophenone or (heteroaryl)aryl ketones such as 4-benzoylpyridine, 9,10-anthraquinone, 9H-xanthen-9-one, and derivatives thereof as acceptor moieties to which the donor moieties (usually carbazolyl substituents) are bonded. Examples of such TADF molecules include BPBCz (bis(4-(9′-phenyl-9H,9′H-[3,3′-bicarbazol]-9-yl)phenyl)methanone), mDCBP ((3,5-di(9H-carbazol-9-yl)phenyl)(pyridin-4-yl)methanone), AQ-DTBu-Cz (2,6-bis(4-(3,6-di-tert-butyl-9H-carbazol-9-yl)phenyl)anthracene-9,10-dione), and MCz-XT (3-(1,3,6,8-tetramethyl-9H-carbazol-9-yl)-9H-xanthen-9-one), respectively.

Sulfoxides, in particular diphenyl sulfoxides, are also commonly used as acceptor moieties for the construction of TADF materials and known examples include 4-PC-DPS (9-phenyl-3-(4-(phenylsulfonyl)phenyl)-9H-carbazole), DitBu-DPS (9,9′-(sulfonylbis(4,1-phenylene))bis(9H-carbazole)), and TXO-PhCz (2-(9-phenyl-9H-carbazol-3-yl)-9H-thioxanthen-9-one 10,10-dioxide).

Exemplarily, all groups of TADF molecules mentioned above may provide suitable TADF materials E^Bfor use according to the present invention, given that the specific materials fulfills the aforementioned basic requirement, namely the ΔE_STvalue being smaller than 0.4 eV.

The person skilled in the art knows that not only the structures named above, but many more materials may be suitable TADF materials E^Bin the context of the present invention. The skilled artisan is familiar with the design principles of such molecules and also knows how to design such molecules with a certain emission color (e.g., blue, green or red emission).

See for example: H. Tanaka, K. Shizu, H. Nakanotani, C. Adachi, Chemistry of Materials 2013, 25(18), 3766, DOI: 10.1021/cm402428a; J. Li, T. Nakagawa, J. MacDonald, Q. Zhang, H. Nomura, H. Miyazaki, C. Adachi, Advanced Materials 2013, 25(24), 3319, DOI: 10.1002/adma.201300575; K. Nasu, T. Nakagawa, H. Nomura, C.-J. Lin, C.-H. Cheng, M.-R. Tseng, T. Yasudaad, C. Adachi, Chemical Communications 2013, 49(88), 10385, DOI: 10.1039/c3cc44179b; Q. Zhang, B. Li1, S. Huang, H. Nomura, H. Tanaka, C. Adachi, Nature Photonics 2014, 8(4), 326, DOI: 10.1038/nphoton.2014.12; B. Wex, B. R. Kaafarani, Journal of Materials Chemistry C 2017, 5, 8622, DOI: 10.1039/c7tc02156a; Y. Im, M. Kim, Y. J. Cho, J.-A. Seo, K. S. Yook, J. Y. Lee, Chemistry of Materials 2017, 29(5), 1946, DOI: 10.1021/acs.chemmater.6b05324; T.-T. Bui, F. Goubard, M. Ibrahim-Ouali, D. Gigmes, F. Dumur, Beilstein Journal of Organic Chemistry 2018, 14, 282, DOI: 10.3762/bjoc.14.18; X. Liang, Z.-L. Tu, Y.-X. Zheng, Chemistry—A European Journal 2019, 25(22), 5623, DOI: 10.1002/chem.201805952.

Furthermore, for example, US2015105564 (A1), US2015048338 (A1), US2015141642 (A1), US2014336379 (A1), US2014138670 (A1), US2012241732 (A1), EP3315581 (A1), EP3483156 (A1), and US2018053901 (A1) disclose TADF materials E^Bthat may be used in organic electroluminescent devices according to the present invention. It is understood that this does not imply that the present invention is limited to organic electroluminescent devices including TADF materials disclosed in the cited references. It is also understood that any TADF materials used in the state of the art may also be suitable TADF materials E^Bin the context of the present invention.

In one embodiment of the invention, each TADF material E^Bincludes one or more chemical moieties independently of each other selected from the group consisting of CN, CF₃, and an optionally substituted 1,3,5-triazinyl group.

In one embodiment of the invention, each TADF material E^Bincludes one or more chemical moieties independently of each other selected from the group consisting of CN and an optionally substituted 1,3,5-triazinyl group.

In one embodiment of the invention, each TADF material E^Bincludes one or more optionally substituted 1,3,5-triazinyl group.

In one embodiment of the invention, each TADF material E^Bincludes one or more chemical moieties independently of each other selected from an amino group, indolyl, carbazolyl, and derivatives thereof, all of which may be optionally substituted, wherein these groups may be bonded to the core structure of the respective TADF molecule via a nitrogen (N) or via a carbon (C) atom, and wherein substituents bonded to these groups may form mono- or polycyclic, aliphatic or aromatic, carbo- or heterocyclic ring systems.

In a preferred embodiment of the invention, the at least one, preferably each TADF material E^Bincludes

- one or more first chemical moiety, independently of each other selected from an amino group, indolyl, carbazolyl, and derivatives thereof, all of which may be optionally substituted, wherein these groups may be bonded to the core structure of the respective TADF molecule via a nitrogen (N) or via a carbon (C) atom, and wherein substituents bonded to these groups may form mono- or polycyclic, aliphatic or aromatic, carbo- or heterocyclic ring systems;
- one or more second chemical moiety, independently of each other selected from the group consisting of CN, CF3, and an optionally substituted 1,3,5-triazinyl group.

In an even more preferred embodiment of the invention, the at least one, preferably each TADF material E^Bincludes

- one or more first chemical moiety, independently of each other selected from an amino group, indolyl, carbazolyl, and derivatives thereof, all of which may be optionally substituted, wherein these groups may be bonded to the core structure of the respective TADF molecule via a nitrogen (N) or via a carbon (C) atom, and wherein substituents bonded to these groups may form mono- or polycyclic, aliphatic or aromatic, carbo- or heterocyclic ring systems;
- one or more second chemical moiety, independently of each other selected from the group consisting of CN and an optionally substituted 1,3,5-triazinyl group.

In a still even more preferred embodiment of the invention, the at least one, preferably each TADF material E^Bincludes

- one or more first chemical moiety, independently of each other selected from an amino group, indolyl, carbazolyl, and derivatives thereof, all of which may be optionally substituted, wherein these groups may be bonded to the core structure of the respective TADF molecule via a nitrogen (N) or via a carbon (C) atom, and wherein substituents bonded to these groups may form mono- or polycyclic, aliphatic or aromatic, carbo- or heterocyclic ring systems;
- one or more optionally substituted 1,3,5-triazinyl group.

The person skilled in the art knows that the expression “derivatives thereof” means that the respective parent structure may be optionally substituted or any atom within the respective parent structure may be replaced by an atom of another element for example.

In one embodiment of the invention, the organic electroluminescent device including at least one light-emitting layer B including:

- (i) at least one host material H^B, which has a lowermost excited singlet state energy level E(S1^H) and a lowermost excited triplet state energy level E(T1^H); and
- (ii) at least one phosphorescence material P^B, which has a lowermost excited singlet state energy level E(S1^P) and a lowermost excited triplet state energy level E(T1^P); and
- (iii) at least one small full width at half maximum (FWHM) emitter S^B, which has a lowermost excited singlet state energy level E(S1^S) and a lowermost excited triplet state energy level E(T1^S), wherein S^Bemits light with a full width at half maximum (FWHM) of less than or equal to 0.25 eV; and
- (iv) at least one thermally activated delayed fluorescence (TADF) material E^B, which has a lowermost excited singlet state energy level E(S1^E) and a lowermost excited triplet state energy level E(T1^E),
- wherein the relations expressed by the following formulas (1) and (2) apply:

E(T1^H)>E(T1^P) (1)

E(T1^H)>E(T1^E) (2),

- wherein each TADF material E^Bincludes
- one or more first chemical moiety, independently of each other selected from an amino group, indolyl, carbazolyl, and derivatives thereof, all of which may be optionally substituted, wherein these groups may be bonded to the core structure of the respective TADF molecule via a nitrogen (N) or via a carbon (C) atom, and wherein substituents bonded to these groups may form mono- or polycyclic, aliphatic or aromatic, carbo- or heterocyclic ring systems;
- one or more second chemical moiety, independently of each other selected from the group consisting of CN and an optionally substituted 1,3,5-triazinyl group.

In one embodiment of the invention, each TADF material E^Bincludes

- one or more first chemical moiety, each including or consisting of a structure according to formula D-I:

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- and
- optionally, one or more second chemical moiety, each independently of each other selected from CN, CF₃, and a structure according to any of formulas A-I, A-II, A-III, and A-IV:

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- and
- one third chemical moiety including or consisting of a structure according to any of formulas L-I, L-II, L-III, L-IV, L-V, L-VI, L-VII, and L-VIII:

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- wherein
- the one or more first chemical moiety and the one or more second chemical moiety are covalently bonded via a single bond to the third chemical moiety;
- wherein in formula D-I:
- # represents the binding site of a single bond linking the respective first chemical moiety according to formula D-I to the third chemical moiety;
- Z²is at each occurrence independently of each other selected from the group consisting of a direct bond, CR¹R², C═CR¹R², C═O, C═NR¹, NR¹, O, SiR¹R², S, S(O) and S(O)₂;
- R^a, R^b, R^d, R¹, and R²are at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, N(R³)₂, OR³, Si(R³)₃, B(OR³)₂, OSO₂R³, CF₃, CN, F, Cl, Br, I,
- C₁-C₄₀-alkyl,
- which is optionally substituted with one or more substituents R³and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R³C═CR³, C≡C, Si(R³)₂, Ge(R³)₂, Sn(R³)₂, C═O, C═S, C═Se, C═NR³, P(═O)(R³), SO, SO₂, NR³, O, S or CONR³;
- C₁-C₄₀-alkoxy,
- which is optionally substituted with one or more substituents R³and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R³C═CR³, C≡C, Si(R³)₂, Ge(R³)₂, Sn(R³)₂, C═O, C═S, C═Se, C═NR³, P(═O)(R³), SO, SO₂, NR³, O, S or CONR³;
- C₁-C₄₀-thioalkoxy,
- which is optionally substituted with one or more substituents R³and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R³C═CR³, C≡C, Si(R³)₂, Ge(R³)₂, Sn(R³)₂, C═O, C═S, C═Se, C═NR³, P(═O)(R³), SO, SO₂, NR³, O, S or CONR³;
- C₂-C₄₀-alkenyl,
- which is optionally substituted with one or more substituents R³and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R³C═CR³, C≡C, Si(R³)₂, Ge(R³)₂, Sn(R³)₂, C═O, C═S, C═Se, C═NR³, P(═O)(R³), SO, SO₂, NR³, O, S or CONR³;
- C₂-C₄₀-alkynyl,
- which is optionally substituted with one or more substituents R³and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R³C═CR³, C≡C, Si(R³)₂, Ge(R³)₂, Sn(R³)₂, C═O, C═S, C═Se, C═NR³, P(═O)(R³), SO, SO₂, NR³, O, S or CONR³;
- C₆-C₆₀-aryl,
- which is optionally substituted with one or more substituents R³; and
- C₃-C₆₀-heteroaryl,
- which is optionally substituted with one or more substituents R³;
- R³is at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, N(R⁴)₂, OR⁴, Si(R⁴)₃, B(OR⁴)₂, OSO₂R⁴, CF₃, CN, F, Br, I,
- C₁-C₄₀-alkyl,
- which is optionally substituted with one or more substituents R⁴and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R⁴C═CR⁴, C≡C, Si(R⁴)₂, Ge(R⁴)₂, Sn(R⁴)₂, C═O, C═S, C═Se, C═NR⁴, P(═O)(R⁴), SO, SO₂, NR⁴, O, S or CONR⁴;
- C₁-C₄₀-alkoxy,
- which is optionally substituted with one or more substituents R⁴and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R⁴C═CR⁴, C≡C, Si(R⁴)₂, Ge(R⁴)₂, Sn(R⁴)₂, C═O, C═S, C═Se, C═NR⁴, P(═O)(R⁴), SO, SO₂, NR⁴, O, S or CONR⁴;
- C₁-C₄₀-thioalkoxy,
- which is optionally substituted with one or more substituents R⁴and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R⁴C═CR⁴, C≡C, Si(R⁴)₂, Ge(R⁴)₂, Sn(R⁴)₂, C═O, C═S, C═Se, C═NR⁴, P(═O)(R⁴), SO, SO₂, NR⁴, O, S or CONR⁴;
- C₂-C₄₀-alkenyl,
- which is optionally substituted with one or more substituents R⁴and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R⁴C═CR⁴, C≡C, Si(R⁴)₂, Ge(R⁴)₂, Sn(R⁴)₂, C═O, C═S, C═Se, C═NR⁴, P(═O)(R⁴), SO, SO₂, NR⁴, O, S or CONR⁴;
- C₂-C₄₀-alkynyl,
- which is optionally substituted with one or more substituents R⁴and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R⁴C═CR⁴, C≡C, Si(R⁴)₂, Ge(R⁴)₂, Sn(R⁴)₂, C═O, C═S, C═Se, C═NR⁴, P(═O)(R⁴), SO, SO₂, NR⁴, O, S or CONR⁴;
- C₆-C₆₀-aryl,
- which is optionally substituted with one or more substituents R⁴; and
- C₃-C₅₇-heteroaryl,
- which is optionally substituted with one or more substituents R⁴;
- wherein, optionally, any substituents R^a, R^b, R^d, R¹, R², R³, and R⁴independently of each other form a mono- or polycyclic, aliphatic or aromatic or heteroaromatic, carbo- or heterocyclic and/or benzo-fused ring system with one or more adjacent substituents selected from R^a, R^b, R^d, R¹, R², R³, and R⁴; wherein the optionally so formed ring system may optionally be substituted with one or more substituents R⁵;
- R⁴and R⁵are at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, OPh, CF₃, CN, F,
- C₁-C₅-alkyl,
- wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, CN, CF₃, or F;
- C₁-C₅-alkoxy,
- wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, CN, CF₃, or F;
- C₁-C₅-thioalkoxy,
- wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, CN, CF₃, or F;
- C₂-C₅-alkenyl,
- wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, CN, CF₃, or F;
- C₂-C₅-alkynyl,
- wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, CN, CF₃, or F;
- C₆-C₁₈-aryl,
- wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, C₁-C₅-alkyl, Ph or CN;
- C₃-C₁₇-heteroaryl,
- wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, Ph or C₁-C₅-alkyl;
- N(C₆-C₁₈-aryl)₂;
- N(C₃-C₁₇-heteroaryl)₂, and
- N(C₃-C₁₇-heteroaryl)(C₆-C₁₈-aryl);
- a is an integer and is 0 or 1;
- b is an integer and is at each occurrence 0 or 1, wherein both b are always identical;
- wherein both integers b are 0 when integer a is 1 and integer a is 0 when both integers b are 1;
- wherein in formulas A-I, A-II, A-III, A-IV:
- the dashed line indicates a single bond linking the respective second chemical moiety according to formula A-I, A-II, A-III or A-IV to the third chemical moiety;
- Q¹is at each occurrence independently of each other selected from nitrogen (N), CR⁶, and CR⁷, with the provision that in formula A-I, two adjacent groups Q¹cannot both be nitrogen (N); wherein, if none of the groups Q¹in formula A-I is nitrogen (N), at least one of the groups Q¹is CR⁷;
- Q²is at each occurrence independently of each other selected from nitrogen (N), and CR⁶, with the provisions that in formulas A-II and A-III, at least one group Q²is nitrogen (N) and that two adjacent groups Q²cannot both be nitrogen (N);
- R⁶and R⁸are at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, N(R⁹)₂, OR⁹, Si(R⁹)₃, B(OR⁹)₂, OSO₂R⁹, CF₃, CN, F, Cl, Br, I,
- C₁-C₄₀-alkyl,
- which is optionally substituted with one or more substituents R⁹and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R⁹C═CR⁹, C≡C, Si(R⁹)₂, Ge(R⁹)₂, Sn(R⁹)₂, C═O, C═S, C═Se, C═NR⁹, P(═O)(R⁹), SO, SO₂, NR⁹, O, S or CONR⁹;
- C₁-C₄₀-alkoxy,
- which is optionally substituted with one or more substituents R⁹and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R⁹C═CR⁹, C≡C, Si(R⁹)₂, Ge(R⁹)₂, Sn(R⁹)₂, C═O, C═S, C═Se, C═NR⁹, P(═O)(R⁹), SO, SO₂, NR⁹, O, S or CONR⁹;
- C₁-C₄₀-thioalkoxy,
- which is optionally substituted with one or more substituents R⁹and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R⁹C═CR⁹, C≡C, Si(R⁹)₂, Ge(R⁹)₂, Sn(R⁹)₂, C═O, C═S, C═Se, C═NR⁹, P(═O)(R⁹), SO, SO₂, NR⁹, O, S or CONR⁹;
- C₂-C₄₀-alkenyl,
- which is optionally substituted with one or more substituents R⁹and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R⁹C═CR⁹, C≡C, Si(R⁹)₂, Ge(R⁹)₂, Sn(R⁹)₂, C═O, C═S, C═Se, C═NR⁹, P(═O)(R⁹), SO, SO₂, NR⁹, O, S or CONR⁹;
- C₂-C₄₀-alkynyl,
- which is optionally substituted with one or more substituents R⁹and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R⁹C═CR⁹, C≡C, Si(R⁹)₂, Ge(R⁹)₂, Sn(R⁹)₂, C═O, C═S, C═Se, C═NR⁹, P(═O)(R⁹), SO, SO₂, NR⁹, O, S or CONR⁹;
- C₆-C₆₀-aryl,
- which is optionally substituted with one or more substituents R⁹; and
- C₃-C₆₀-heteroaryl,
- which is optionally substituted with one or more substituents R⁹;
- R⁹is at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, N(R¹⁰)₂, OR¹⁰, Si(R¹⁰)₃, B(OR¹⁰)₂, OSO₂R¹⁰, CF₃, CN, F, Cl, Br, I,
- C₁-C₄₀-alkyl,
- which is optionally substituted with one or more substituents R¹⁰and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R¹⁰C═CR¹⁰, C≡C, Si(R¹⁰)₂, Ge(R¹⁰)₂, Sn(R¹⁰)₂, C═O, C═S, C═Se, C═NR¹⁰, P(═O)(R¹⁰), SO, SO₂, NR¹⁰, O, S or CONR¹⁰;
- C₁-C₄₀-alkoxy,
- which is optionally substituted with one or more substituents R¹⁰and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R¹⁰C═CR¹⁰, C≡C, Si(R¹⁰)₂, Ge(R¹⁰)₂, Sn(R¹⁰)₂, C═O, C═S, C═Se, C═NR¹⁰, P(═O)(R¹⁰), SO, SO₂, NR¹⁰, O, S or CONR¹⁰;
- C₁-C₄₀-thioalkoxy,
- which is optionally substituted with one or more substituents R¹⁰and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R¹⁰C═CR¹⁰, C≡C, Si(R¹⁰)₂, Ge(R¹⁰)₂, Sn(R¹⁰)₂, C═O, C═S, C═Se, C═NR¹⁰, P(═O)(R¹⁰), SO, SO₂, NR¹⁰, O, S or CONR¹⁰;
- C₂-C₄₀-alkenyl,
- which is optionally substituted with one or more substituents R¹⁰and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R¹⁰C═CR¹⁰, C≡C, Si(R¹⁰)₂, Ge(R¹⁰)₂, Sn(R¹⁰)₂, C═O, C═S, C═Se, C═NR¹⁰, P(═O)(R¹⁰), SO, SO₂, NR¹⁰, O, S or CONR¹⁰;
- C₂-C₄₀-alkynyl,
- which is optionally substituted with one or more substituents R¹⁰and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R¹⁰C═CR¹⁰, C≡C, Si(R¹⁰)₂, Ge(R¹⁰)₂, Sn(R¹⁰)₂, C═O, C═S, C═Se, C═NR¹⁰, P(═O)(R¹⁰), SO, SO₂, NR¹⁰, O, S or CONR¹⁰;
- C₆-C₆₀-aryl,
- which is optionally substituted with one or more substituents R¹⁰; and
- C₃-C₆₀-heteroaryl,
- which is optionally substituted with one or more substituents R¹⁰;
- R¹⁰is at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, OPh, CF₃, CN, F,
- C₁-C₅-alkyl,
- wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, CN, CF₃, or F;
- C₁-C₅-alkoxy,
- wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, CN, CF₃, or F;
- C₁-C₅-thioalkoxy,
- wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, CN, CF₃, or F;
- C₂-C₅-alkenyl,
- wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, CN, CF₃, or F;
- C₂-C₅-alkynyl,
- wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, CN, CF₃, or F;
- C₆-C_18-aryl,
- wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, C₁-C₅-alkyl, Ph or CN;
- C₃-C₁₇-heteroaryl,
- wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, Ph or C₁-C₅-alkyl;
- N(Ce-Cle-aryl)₂;
- N(C₃-C₁₇-heteroaryl)₂, and
- N(C₃-C₁₇-heteroaryl)(C₆-C_18-aryl);
- R⁷is at each occurrence independently of each other selected from the group consisting of CN, CF₃and a structure according to formula EWG-I:

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- wherein R^Xis defined as R⁶, with the provision that at least one group R^Xin formula EWG-I is CN or CF₃;
- wherein the two adjacent groups R⁸in formula A-IV optionally form an aromatic ring, which is fused to the structure of formula A-IV and optionally substituted with one or more substituents R¹⁰; wherein the optionally so formed fused ring system includes in total 9 to 18 ring atoms;
- wherein in formulas L-I, L-II, L-III, L-IV, L-V, L-VI, L-VII, and L-VIII:
- Q³is at each occurrence independently of each other selected from nitrogen (N) and CR¹², with the provision that at least one Q³is nitrogen (N);
- R¹¹is at each occurrence independently of each other either the binding site of a single bond connecting a first or a second chemical moiety to the third chemical moiety or is independently of each other selected from the group consisting of: hydrogen, deuterium, F, Cl, Br, I,
- C₁-C₅-alkyl,
- wherein one or more hydrogen atoms are optionally substituted by deuterium;
- C₆-C₁₈-aryl,
- wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, C₁-C₅-alkyl groups, C₆-C₁₈-aryl groups, F, Cl, Br, and I;
- R¹²is defined as R⁶;
- wherein the maximum number of first and second chemical moieties attached to the third chemical moiety is only limited by the number of available binding sites on the third chemical moiety (in other words: the number of substituents R¹¹), with the aforementioned provision, that each TADF material E^Bincludes at least one first chemical moiety, at least one second chemical moiety, and exactly one third chemical moiety.

In a preferred embodiment of the invention,

- Z²is at each occurrence independently of each other selected from the group consisting of a direct bond, CR¹R², C═CR¹R², C═O, C═NR¹, NR¹, O, SiR¹R², S, S(O) and S(O)₂;
- R^a, R^b, R^d, R¹, and R²are at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, N(R³)₂, OR³, Si(R³)₃, CF₃, CN, F, Cl, Br, I,
- C₁-C₄₀-alkyl,
- which is optionally substituted with one or more substituents R³and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R³C═CR³, C≡C, Si(R³)₂, Ge(R³)₂, Sn(R³)₂, C═O, C═S, C═Se, C═NR³, P(═O)(R³), SO, SO₂, NR³, O, S or CONR³;
- C₆-C₆₀-aryl,
- which is optionally substituted with one or more substituents R³; and
- C₃-C₆₀-heteroaryl,
- which is optionally substituted with one or more substituents R³;
- R³is at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, N(R⁴)₂, OR⁴, Si(R⁴)₃, CF₃, CN, F, Br, I,
- C₁-C₄₀-alkyl,
- which is optionally substituted with one or more substituents R⁴and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R⁴C═CR⁴, C≡C, Si(R⁴)₂, Ge(R⁴)₂, Sn(R⁴)₂, C═O, C═S, C═Se, C═NR⁴, P(═O)(R⁴), SO, SO₂, NR⁴, O, S or CONR⁴;
- C₆-C₆₀-aryl,
- which is optionally substituted with one or more substituents R⁴; and
- C₃-C₅₇-heteroaryl,
- which is optionally substituted with one or more substituents R⁴;
- wherein, optionally, any of the substituents R^a, R^b, R^d, R¹, R², R³, and R⁴independently of each other form a mono- or polycyclic, aliphatic or aromatic or heteroaromatic, carbo- or heterocyclic and/or benzo-fused ring system with one or more adjacent substituents selected from R^a, R^b, R^d, R¹, R², R³, and R⁴; wherein the optionally so formed ring system may optionally be substituted with one or more substituents R⁵;
- R⁴and R⁵are at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, CF₃, CN, F,
- C₁-C₅-alkyl,
- wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, CN, CF₃, or F;
- C₆-C₁₈-aryl,
- wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, C₁-C₅-alkyl, Ph or CN;
- C₃-C₁₇-heteroaryl,
- wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, C₁-C₅-alkyl or Ph;
- N(C₆-C₁₈-aryl)₂;
- N(C₃-C₁₇-heteroaryl)₂, and
- N(C₃-C₁₇-heteroaryl)(C₆-C₁₈-aryl);
- a is an integer and is 0 or 1;
- b is an integer and is at each occurrence 0 or 1, wherein both b are always identical;
- wherein both integers b are 0 when integer a is 1 and integer a is 0 when both integers b are 1;
- Q¹is at each occurrence independently of each other selected from nitrogen (N), CR⁸, and CR⁷, with the provision that in formula A-I, two adjacent groups Q¹cannot both be nitrogen (N); wherein, if none of the groups Q¹in formula A-I is nitrogen (N), at least one of the groups Q¹is CR⁷;
- Q²is at each occurrence independently of each other selected from nitrogen (N), and CR⁸, with the provision that in formulas A-II and A-III, at least one group Q²is nitrogen (N) and that two adjacent groups Q²cannot both be nitrogen (N);
- R⁶and R⁸are at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, N(R⁹)₂, OR⁹, Si(R⁹)₃, CF₃, CN, F, Cl, Br, I,
- C₁-C₄₀-alkyl,
- which is optionally substituted with one or more substituents R⁹and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R⁹C═CR⁹, C≡C, Si(R⁹)₂, Ge(R⁹)₂, Sn(R⁹)₂, C═O, C═S, C═Se, C═NR⁹, P(═O)(R⁹), SO, SO₂, NR⁹, O, S or CONR⁹;
- C₆-C₆₀-aryl,
- which is optionally substituted with one or more substituents R⁹; and
- C₃-C₆₀-heteroaryl,
- which is optionally substituted with one or more substituents R⁹;
- R⁹is at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, N(R¹⁰)₂, OR¹⁰, Si(R¹⁰)₃, CF₃, CN, F, Cl, Br, I,
- C₁-C₄₀-alkyl,
- which is optionally substituted with one or more substituents R¹⁰and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R¹⁰C═CR¹⁰, C≡C, Si(R¹⁰)₂, Ge(R¹⁰)₂, Sn(R¹⁰)₂, C═O, C═S, C═Se, C═NR¹⁰, P(═O)(R¹⁰), SO, SO₂, NR¹⁰, O, S or CONR¹⁰;
- C₆-C₆₀-aryl,
- which is optionally substituted with one or more substituents R¹⁰; and
- C₃-C₆₀-heteroaryl,
- which is optionally substituted with one or more substituents R¹⁰;
- R¹⁰is at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, OPh, CF₃, CN, F,
- C₁-C₅-alkyl,
- wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, CN, CF₃, or F;
- C₆-C₁₈-aryl,
- wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, C₁-C₅-alkyl, Ph or CN;
- C₃-C₁₇-heteroaryl,
- wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, C₁-C₅-alkyl or Ph;
- N(C₆-C₁₈-aryl)₂;
- N(C₃-C₁₇-heteroaryl)₂, and
- N(C₃-C₁₇-heteroaryl)(C₆-C₁₈-aryl);
- R⁷is at each occurrence independently of each other selected from the group consisting of CN, CF₃and a structure according to formula EWG-I:

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- wherein R^Xis defined as R⁶, with the provision, that at least one group R^Xis CN or CF₃;
- wherein the two adjacent groups R⁸in formula A-IV optionally form an aromatic ring, which is fused to the structure of formula A-IV and optionally substituted with one or more substituents R¹⁰; wherein the optionally so formed fused ring system includes in total 9 to 18 ring atoms;
- Q³is at each occurrence independently of each other selected from nitrogen (N) and CR¹², with the provision that at least one Q³is nitrogen (N);
- R¹¹is at each occurrence independently of each other either the binding site of a single bond connecting a first or a second chemical moiety to the third chemical moiety or is independently of each other selected from the group consisting of: hydrogen, deuterium,
- C₁-C₅-alkyl,
- wherein one or more hydrogen atoms are optionally substituted by deuterium;
- C₆-C₁₈-aryl,
- wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, C₁-C₅-alkyl groups, and C₆-C₁₈-aryl groups;
- R¹²is defined as R⁶;
- wherein the maximum number of first and second chemical moieties attached to the third chemical moiety is only limited by the number of available binding sites on the third chemical moiety (in other words: the number of substituents R¹¹) (preferably, with the aforementioned provision, that each TADF material E^Bincludes at least one first chemical moiety, at least one second chemical moiety, and exactly one third chemical moiety).

In an even more preferred embodiment of the invention,

- Z²is at each occurrence independently of each other selected from the group consisting of a direct bond, CR¹R², C═CR¹R², C═O, C═NR¹, NR¹, O, SiR¹R², S, S(O) and S(O)₂;
- R^a, R^b, R^d, R¹, and R²are at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, N(R³)₂, OR³, Si(R³)₃, CF₃, CN, F, Cl, Br, I,
- C₁-C₅-alkyl,
- which is optionally substituted with one or more substituents R³
- C₆-C₁₈-aryl,
- which is optionally substituted with one or more substituents R³; and
- C₃-C₁₇-heteroaryl,
- which is optionally substituted with one or more substituents R³;
- R³is at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, N(R⁴)₂, Si(R⁴)₃, CF₃, CN, F,
- C₁-C₅-alkyl,
- which is optionally substituted with one or more substituents R⁴and
- C₆-C₁₈-aryl,
- which is optionally substituted with one or more substituents R⁴; and
- C₃-C₁₇-heteroaryl,
- which is optionally substituted with one or more substituents R⁴;
- wherein, optionally, any of the substituents R^a, R^b, R^d, R¹, R²and R³independently of each other form a mono- or polycyclic, aliphatic or aromatic or heteroaromatic, carbo- or heterocyclic and/or benzo-fused ring system with one or more adjacent substituents selected from R^a, R^b, R^d, R¹, R², and R³; wherein the optionally so formed ring system may optionally be substituted with one or more substituents R⁵;
- R⁴and R⁵are at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, CF₃, CN, F, Me, ⁱPr, ^tBu, N(Ph)₂, and
- Ph, wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, Me, ⁱPr, ^tBu, and Ph;
- a is an integer and is 0 or 1;
- b is an integer and is at each occurrence 0 or 1, wherein both b are always identical;
- wherein both integers b are 0 when integer a is 1 and integer a is 0 when both integers b are 1;
- Q¹is at each occurrence independently of each other selected from nitrogen (N), CR⁸, and CR⁷, with the provision that in formula A-I, two adjacent groups Q¹cannot both be nitrogen (N); wherein, if none of the groups Q¹in formula A-I is nitrogen (N), at least one of the groups Q¹is CR⁷;
- Q²is at each occurrence independently of each other selected from nitrogen (N), and CR⁶, with the provision that in formulas A-II and A-III, at least one group Q²is nitrogen (N) and that two adjacent groups Q²cannot both be nitrogen (N);
- R⁶and R⁸are at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, N(R⁹)₂, OR⁹, Si(R⁹)₃, CF₃, CN, F,
- C₁-C₅-alkyl,
- which is optionally substituted with one or more substituents R⁹;
- C₆-C₁₈-aryl,
- which is optionally substituted with one or more substituents R⁹; and
- C₃-C₁₇-heteroaryl,
- which is optionally substituted with one or more substituents R⁹;
- R⁹is at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, N(R¹⁰)₂, OR¹⁰, Si(R¹⁰)₃, CF₃, CN, F,
- C₁-C₅-alkyl,
- which is optionally substituted with one or more substituents R¹⁰
- C₆-C₁₈-aryl,
- which is optionally substituted with one or more substituents R¹⁰; and
- C₃-C₁₇-heteroaryl,
- which is optionally substituted with one or more substituents R¹⁰;
- R¹⁰is at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, Me, ⁱPr, ^tBu, CF₃, CN, F, N(Ph)₂, and
- Ph, wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, Me, ⁱPr, ^tBu, Ph, CN, CF₃, or F.
- R⁷is at each occurrence independently of each other selected from the group consisting of CN, CF₃and a structure according to formula EWG-I:

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- wherein R^Xis defined as R⁶, with the provision, that at least one group R^Xis CN or CF₃;
- wherein the two adjacent groups R⁸in formula A-IV optionally form an aromatic ring, which is fused to the structure of formula A-IV and optionally substituted with one or more substituents R¹⁰; wherein the optionally so formed fused ring system includes in total 9 to 18 ring atoms;
- Q³is at each occurrence independently of each other selected from nitrogen (N) and CR¹², with the provision that at least one Q³is nitrogen (N);
- R¹¹is at each occurrence independently of each other either the binding site of a single bond connecting a first or a second chemical moiety to the third chemical moiety or is independently of each other selected from the group consisting of: hydrogen, deuterium,
- C₁-C₅-alkyl,
- wherein one or more hydrogen atoms are optionally substituted by deuterium;
- C₆-C₁₈-aryl,
- which is optionally substituted with one or more substituents independently of each other selected from the group consisting of: deuterium, Me, ⁱPr, ^tBu, and Ph;
- R¹²is defined as R⁶;
- wherein the maximum number of first and second chemical moieties attached to the third chemical moiety is only limited by the number of available binding sites on the third chemical moiety (in other words: the number of substituents R¹¹) (preferably with the aforementioned provision, that each TADF material E^Bincludes at least one first chemical moiety, at least one second chemical moiety, and exactly one third chemical moiety).

In a still even more preferred embodiment of the invention,

- Z²is at each occurrence independently of each other selected from the group consisting of a direct bond, CR¹R², C═O, NR¹, O, SiR¹R², S, S(O) and S(O)₂;
- R^a, R^b, R^d, R¹, and R²are at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, N(R³)₂, OR³, Si(R³)₃, CF₃, CN,
- C₁-C₅-alkyl,
- which is optionally substituted with one or more substituents R³
- C₆-C₁₈-aryl,
- which is optionally substituted with one or more substituents R³; and
- C₃-C₁₇-heteroaryl,
- which is optionally substituted with one or more substituents R³;
- R³is at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, CF₃, CN, F, Me, ⁱPr, ^tBu, N(Ph)₂,
- Ph, wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, Me, ⁱPr, ^tBu, and Ph;
- wherein, optionally, any of the substituents R^a, R^b, R^d, R¹, and R²independently of each other form a mono- or polycyclic, aliphatic or aromatic or heteroaromatic, carbo- or heterocyclic and/or benzo-fused ring system with one or more adjacent substituents selected from R^a, R^b, R^d, R¹, and R²; wherein the optionally so formed ring system may optionally be substituted with one or more substituents independently of each other selected from the group consisting of: hydrogen, deuterium, Me, ⁱPr, ^tBu, CN, CF₃, F, and
- Ph, wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, Me, ⁱPr, ^tBu, and Ph;
- wherein an optionally so formed fused ring system constructed from the structure according to formula D-1 and the attached rings formed by adjacent substituents includes in total 13 to 30 ring atoms, preferably 16 to 30 ring atoms;
- a is an integer and is 0 or 1;
- b is an integer and is at each occurrence 0 or 1, wherein both b are always identical;
- wherein both integers b are 0 when integer a is 1 and integer a is 0 when both integers b are 1;
- Q¹is at each occurrence independently of each other selected from nitrogen (N), CR⁶, and CR⁷, with the provision that in formula A-I, two adjacent groups Q¹cannot both be nitrogen (N); wherein, if none of the groups Q¹in formula A-I is nitrogen (N), at least one of the groups Q¹is CR⁷;
- Q²is at each occurrence independently of each other selected from nitrogen (N), and CR⁶, with the provision that in formulas A-II and A-III, at least one group Q²is nitrogen (N) and that two adjacent groups Q²cannot both be nitrogen (N);
- R⁶and R⁸are at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, N(R⁹)₂, OR⁹, Si(R⁹)₃, CF₃, CN, F,
- C₁-C₅-alkyl,
- which is optionally substituted with one or more substituents R⁹;
- C₆-C₁₈-aryl,
- which is optionally substituted with one or more substituents R⁹; and
- C₃-C₁₇-heteroaryl,
- which is optionally substituted with one or more substituents R⁹;
- R⁹is at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, Me, ⁱPr, ^tBu, CF₃, CN, F, N(Ph)₂, and
- Ph, wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, Me, ⁱPr, ^tBu, Ph, CN, CF₃, or F.
- R⁷is at each occurrence independently of each other selected from the group consisting of CN, CF₃and a structure according to formula EWG-I:

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- wherein R^Xis defined as R⁶, with the provision, that at least one group R^Xis CN or CF₃;
- wherein the two adjacent groups R⁸in formula A-IV optionally form an aromatic ring, which is fused to the structure of formula A-IV and optionally substituted with one or more substituents independently of each other selected from the group consisting of: hydrogen, deuterium, Me, ⁱPr, ^tBu, CF₃, CN, and
- Ph, wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, Me, ⁱPr, ^tBu, Ph, CN or CF₃;
- wherein the optionally so formed fused ring system includes in total 9 to 18 ring atoms;
- Q³is at each occurrence independently of each other selected from nitrogen (N) and CR¹², with the provision that at least one Q³is nitrogen (N);
- R¹¹is at each occurrence independently of each other either the binding site of a single bond connecting a first or a second chemical moiety to the third chemical moiety or is independently of each other selected from the group consisting of: hydrogen, deuterium, Me, ⁱPr, ^tBu, and
- Ph, which is optionally substituted with one or more substituents independently of each other selected from the group consisting of: deuterium, Me, ⁱPr, ^tBu, and Ph;
- R¹²is defined as R⁶;
- wherein the maximum number of first and second chemical moieties attached to the third chemical moiety is only limited by the number of available binding sites on the third chemical moiety (in other words: the number of substituents R¹¹) (preferably with the aforementioned provision, that each TADF material E^Bincludes at least one first chemical moiety, at least one second chemical moiety, and exactly one third chemical moiety).

In a still even more preferred embodiment of the invention,

- Z²is at each occurrence independently of each other selected from the group consisting of a direct bond, CR¹R², C═O, NR¹, O, SiR¹R², S, S(O) and S(O)₂;
- R^a, R^b, and R^dare at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, N(R³)₂, OR³, Si(R³)₃, CF₃, CN, Me, ⁱPr, ^tBu,
- Ph, wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, Me, ⁱPr, ^tBu, and Ph;
- carbazolyl, wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, Me, ⁱPr, ^tBu, and Ph;
- triazinyl, wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, Me, ⁱPr, ^tBu, and Ph;
- pyrimidinyl, wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, Me, ⁱPr, ^tBu, and Ph;
- pyridinyl, wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, Me, ⁱPr, ^tBu, and Ph;
- R¹and R²are at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, N(R³)₂, OR³, Si(R³)₃, CF₃, CN,
- C₁-C₅-alkyl,
- which is optionally substituted with one or more substituents R³
- C₆-C₁₈-aryl,
- which is optionally substituted with one or more substituents R³; and
- C₃-C₁₇-heteroaryl,
- which is optionally substituted with one or more substituents R³;
- R³is at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, CF₃, CN, F, Me, ⁱPr, ^tBu, and
- Ph, wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, Me, ⁱPr, ^tBu, and Ph;
- wherein, optionally, any of the substituents R^a, R^b, R^d, R¹, and R²independently of each other form a mono- or polycyclic, aliphatic or aromatic or heteroaromatic, carbo- or heterocyclic and/or benzo-fused ring system with one or more adjacent substituents selected from R^a, R^b, R^d, R¹, and R²; wherein the optionally so formed ring system may optionally be substituted with one or more substituents independently of each other selected from the group consisting of: hydrogen, deuterium, Me, ⁱPr, ^tBu, CN, CF₃, F, and
- Ph, wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, Me, ⁱPr, ^tBu, and Ph;
- wherein an optionally so formed fused ring system constructed from the structure according to formula D1 and the attached rings formed by adjacent substituents includes in total 13 to 30 ring atoms, preferably 16 to 30 ring atoms;
- a is an integer and is 0 or 1;
- b is an integer and is at each occurrence 0 or 1, wherein both b are always identical;
- wherein both integers b are 0 when integer a is 1 and integer a is 0 when both integers b are 1;
- Q¹is at each occurrence independently of each other selected from nitrogen (N), CR⁶, and CR⁷, with the provision that in formula A-I, two adjacent groups Q¹cannot both be nitrogen (N); wherein, if none of the groups Q¹in formula A-I is nitrogen (N), at least one of the groups Q¹is CR⁷;
- Q²is at each occurrence independently of each other selected from nitrogen (N), and CR⁶, with the provision that in formulas A-II and A-III, at least one group Q²is nitrogen (N) and that two adjacent groups Q²cannot both be nitrogen (N);
- R⁶and R⁸are at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, N(R⁹)₂, OR⁹, Si(R⁹)₃, CF₃, CN, F,
- C₁-C₅-alkyl,
- which is optionally substituted with one or more substituents R⁹;
- C₆-C₁₈-aryl,
- which is optionally substituted with one or more substituents R⁹; and
- C₃-C₁₇-heteroaryl,
- which is optionally substituted with one or more substituents R⁹;
- R⁹is at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, Me, ⁱPr, ^tBu, CF₃, CN, F, N(Ph)₂, and
- Ph, wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, Me, ⁱPr, ^tBu, Ph, CN, CF₃, or F.
- R⁷is at each occurrence independently of each other selected from the group consisting of CN, CF₃and a structure according to formula EWG-I:

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- wherein R^Xis defined as R⁶, with the provision, that at least one group R^Xis CN or CF3;
- wherein the two adjacent groups R⁸in formula A-IV optionally form an aromatic ring, which is fused to the structure of formula A-IV and optionally substituted with one or more substituents independently of each other selected from the group consisting of: hydrogen, deuterium, Me, ⁱPr, ^tBu, and
- Ph, wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, Me, ⁱPr, ^tBu, Ph;
- wherein the optionally so formed fused ring system includes in total 9 to 18 ring atoms;
- Q³is at each occurrence independently of each other selected from nitrogen (N) and CR¹², with the provision that at least one Q³is nitrogen (N);
- R¹¹is at each occurrence independently of each other either the binding site of a single bond connecting a first or a second chemical moiety to the third chemical moiety or is independently of each other selected from the group consisting of: hydrogen, deuterium, Me, ⁱPr, ^tBu, and
- Ph, which is optionally substituted with one or more substituents independently of each other selected from the group consisting of: deuterium, Me, ⁱPr, ^tBu, and Ph;
- R¹²is defined as R⁶;
- wherein the maximum number of first and second chemical moieties attached to the third chemical moiety is only limited by the number of available binding sites on the third chemical moiety (in other words: the number of substituents R¹¹) (preferably with the aforementioned provision, that each TADF material E^Bincludes at least one first chemical moiety, at least one second chemical moiety, and exactly one third chemical moiety).

In a still even more preferred embodiment of the invention,

- Z²is at each occurrence independently of each other selected from the group consisting of a direct bond, CR¹R², C═O, NR¹, O, SiR¹R², S, S(O) and S(O)₂;
- R^a, R^b, and R^dare at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, N(R³)₂, OR³, Si(R³)₃, CF₃, CN, Me, ⁱPr, ^tBu,
- Ph, wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, Me, ⁱPr, ^tBu, and Ph; and
- carbazolyl, wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, Me, ⁱPr, ^tBu, and Ph;
- R¹and R²are at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, OR³, Si(R³)₃,
- C₁-C₅-alkyl,
- which is optionally substituted with one or more substituents R³
- C₆-C₁₈-aryl,
- which is optionally substituted with one or more substituents R³; and
- R³is at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, CF₃, CN, F, Me, ⁱPr, ^tBu, and
- Ph, wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, Me, ⁱPr, ^tBu, and Ph;
- wherein, optionally, any of the substituents R^a, R^b, R^d, R¹, and R²independently of each other form a mono- or polycyclic, aliphatic or aromatic or heteroaromatic, carbo- or heterocyclic and/or benzo-fused ring system with one or more substituents selected from R^a, R^b, R^d, R¹, and R²; wherein the optionally so formed ring system may optionally be substituted with one or more substituents independently of each other selected from the group consisting of: hydrogen, deuterium, Me, ⁱPr, ^tBu, CN, CF₃, F, and
- Ph, wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, Me, ⁱPr, ^tBu, and Ph;
- wherein an optionally so formed fused ring system constructed from the structure according to formula D1 and the attached rings formed by adjacent substituents includes in total 13 to 30 ring atoms, preferably 16 to 30 ring atoms;
- a is an integer and is 0 or 1;
- b is an integer and is at each occurrence 0 or 1, wherein both b are always identical;
- wherein both integers b are 0 when integer a is 1 and integer a is 0 when both integers b are 1;
- Q¹is at each occurrence independently of each other selected from nitrogen (N), CR⁶, and CR⁷, with the provision that in formula A-I, two adjacent groups Q¹cannot both be nitrogen (N); wherein, if none of the groups Q¹in formula A-I is nitrogen (N), at least one of the groups Q¹is CR⁷;
- Q²is at each occurrence independently of each other selected from nitrogen (N), and CR⁶, with the provision that in formulas A-II and A-III, at least one group Q²is nitrogen (N) and that two adjacent groups Q²cannot both be nitrogen (N);
- R⁶and R⁸are at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, OPh, N(Ph)₂, Si(Me)₃, Si(Ph)₃, CF₃, CN, F, Me, ⁱPr, ^tBu,
- Ph, wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, Me, ⁱPr, ^tBu, and Ph;
- carbazolyl, wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, Me, ⁱPr, ^tBu, and Ph;
- R⁷is at each occurrence independently of each other selected from the group consisting of CN, CF₃and a structure according to formula EWG-I:

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- wherein R^Xis defined as R⁶, with the provision, that at least one group R^Xis CN or CF3;
- wherein the two adjacent groups R⁸in formula A-IV optionally form an aromatic ring, which is fused to the structure of formula A-IV and optionally substituted with one or more substituents hydrogen, deuterium, Me, ⁱPr, ^tBu, and
- Ph, wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, Me, ⁱPr, ^tBu, Ph;
- wherein the optionally so formed fused ring system includes in total 9 to 18 ring atoms;
- Q³is at each occurrence independently of each other selected from nitrogen (N) and CR¹², with the provision that at least one Q³is nitrogen (N);
- R¹¹is at each occurrence independently of each other either the binding site of a single bond connecting a first or a second chemical moiety to the third chemical moiety or is independently of each other selected from the group consisting of: hydrogen, deuterium, Me, ⁱPr, ^tBu, and
- Ph, which is optionally substituted with one or more substituents independently of each other selected from the group consisting of: deuterium, Me, ⁱPr, ^tBu, and Ph;
- R¹²is defined as R⁶;
- wherein the maximum number of first and second chemical moieties attached to the third chemical moiety is only limited by the number of available binding sites on the third chemical moiety (in other words: the number of substituents R¹¹), (preferably with the aforementioned provision, that each TADF material E^Bincludes at least one first chemical moiety, at least one second chemical moiety, and exactly one third chemical moiety).

In a still even more preferred embodiment of the invention,

- Z²is at each occurrence independently of each other selected from the group consisting of a direct bond, CR¹R², C═O, NR¹, O, SiR¹R², S, S(O) and S(O)₂;
- R^a, R^b, and R^dare at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, N(Ph)₂, Si(Me)₃, Si(Ph)₃, CF₃, CN, Me, ⁱPr, ^tBu,
- Ph, wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, Me, ⁱPr, ^tBu, and Ph; and
- carbazolyl, wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, Me, ⁱPr, ^tBu, and Ph;
- R¹and R²are at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, Me, ⁱPr, ^tBu,
- Ph, wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, Me, ⁱPr, ^tBu, and Ph;
- wherein, optionally, any of the substituents R^a, R^b, R^d, R¹, and R²independently of each other form a mono- or polycyclic, aliphatic or aromatic or heteroaromatic, carbo- or heterocyclic and/or benzo-fused ring system with one or more substituents selected from R^a, R^b, R^d, R¹, and R²; wherein the optionally so formed ring system may optionally be substituted with one or more substituents independently of each other selected from the group consisting of: hydrogen, deuterium, Me, ⁱPr, ^tBu, CN, CF₃, F, and
- Ph, wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, Me, ⁱPr, ^tBu, and Ph;
- wherein an optionally so formed fused ring system constructed from the structure according to formula D1 and the attached rings formed by adjacent substituents includes in total 13 to 30 ring atoms, preferably 16 to 30 ring atoms;
- a is an integer and is 0 or 1;
- b is an integer and is at each occurrence 0 or 1, wherein both b are always identical;
- wherein both integers b are 0 when integer a is 1 and integer a is 0 when both integers b are 1;
- Q¹is at each occurrence independently of each other selected from nitrogen (N), CR⁶, and CR⁷, with the provision that in formula A-I, two adjacent groups Q¹cannot both be nitrogen (N); wherein, if none of the groups Q¹in formula A-I is nitrogen (N), at least one of the groups Q¹is CR⁷;
- Q²is at each occurrence independently of each other selected from nitrogen (N), and CR⁶, with the provision that in formulas A-II and A-III, at least one group Q²is nitrogen (N) and that two adjacent groups Q²cannot both be nitrogen (N);
- R⁶and R⁸are at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, N(Ph)₂, Si(Me)₃, Si(Ph)₃, Me, ⁱPr, ^tBu,
- Ph, wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, Me, ⁱPr, ^tBu, and Ph;
- carbazolyl, wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, Me, ⁱPr, ^tBu, and Ph;
- R⁷is at each occurrence independently of each other selected from the group consisting of CN, CF_aand a structure according to formula EWG-I:

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- wherein R^Xis defined as R⁶, but may also be CN or CF₃, with the provision, that at least one group R^Xis CN or CF₃;
- wherein the two adjacent groups R⁸in formula A-IV optionally form an aromatic ring, which is fused to the structure of formula A-IV and optionally substituted with one or more substituents hydrogen, deuterium, Me, ⁱPr, ^tBu, and
- Ph, wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, Me, ⁱPr, ^tBu, Ph;
- wherein the optionally so formed fused ring system includes in total 9 to 18 ring atoms;
- Q³is at each occurrence independently of each other selected from nitrogen (N) and CR¹², with the provision that at least one Q³is nitrogen (N);
- R¹¹is at each occurrence independently of each other either the binding site of a single bond connecting a first or a second chemical moiety to the third chemical moiety or is independently of each other selected from the group consisting of: hydrogen, deuterium, Me, ⁱPr, ^tBu, and
- Ph, which is optionally substituted with one or more substituents independently of each other selected from the group consisting of: deuterium, Me, ⁱPr, ^tBu, and Ph;
- R¹²is defined as R⁶;
- wherein the maximum number of first and second chemical moieties attached to the third chemical moiety is only limited by the number of available binding sites on the third chemical moiety (in other words: the number of substituents R¹¹) (preferably with the aforementioned provision, that each TADF material E^Bincludes at least one first chemical moiety, at least one second chemical moiety, and exactly one third chemical moiety).

In a particularly preferred embodiment of the invention,

- Z²is at each occurrence independently of each other selected from the group consisting of a direct bond, CR¹R², C═O, NR¹, O, SiR¹R², S, S(O) and S(O)₂;
- R^a, R^b, and R^dare at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, CF₃, CN, Me, ⁱPr, ^tBu, and
- Ph, wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, Me, ⁱPr, ^tBu, and Ph;
- R¹and R²are at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, Me, ⁱPr, ^tBu, and
- Ph, wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, Me, ⁱPr, ^tBu, and Ph;
- wherein, optionally, any of the substituents R^a, R^b, R^d, R¹, and R²independently of each other form a mono- or polycyclic, aliphatic or aromatic or heteroaromatic, carbo- or heterocyclic and/or benzo-fused ring system with one or more substituents selected from R^a, R^b, R^d, R¹, and R²; wherein the optionally so formed ring system may optionally be substituted with one or more substituents independently of each other selected from the group consisting of: hydrogen, deuterium, Me, ⁱPr, ^tBu, CN, CF₃, and
- Ph, wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, Me, ⁱPr, ^tBu, and Ph;
- wherein an optionally so formed fused ring system constructed from the structure according to formula D1 and the attached rings formed by adjacent substituents includes in total 13 to 30 ring atoms, preferably 16 to 30 ring atoms;
- a is an integer and is 0 or 1;
- b is an integer and is at each occurrence 0 or 1, wherein both b are always identical;
- wherein both integers b are 0 when integer a is 1 and integer a is 0 when both integers b are 1;
- Q¹is at each occurrence independently of each other selected from nitrogen (N), CR⁶, and CR⁷, with the provision that in formula A-I, two adjacent groups Q¹cannot both be nitrogen (N); wherein, if none of the groups Q¹in formula A-I is nitrogen (N), at least one of the groups Q¹is CR⁷;
- Q²is at each occurrence independently of each other selected from nitrogen (N), and CR⁶, with the provision that in formulas A-II and A-III, at least one group Q²is nitrogen (N) and that two adjacent groups Q²cannot both be nitrogen (N);
- R⁶and R⁸are at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, N(Ph)₂, Me, ⁱPr, ^tBu,
- Ph, wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, Me, ⁱPr, ^tBu, and Ph; and
- carbazolyl, wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, Me, ⁱPr, ^tBu, and Ph;
- R⁷is at each occurrence independently of each other selected from the group consisting of CN, CF₃and a structure according to formula EWG-I:

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- wherein R^Xis defined as R⁶, but may also be CN or CF₃, with the provision, that at least one group R^Xis CN or CF₃;
- wherein the two adjacent groups R⁸in formula A-IV optionally form an aromatic ring, which is fused to the structure of formula A-IV and optionally substituted with one or more substituents hydrogen, deuterium, Me, ⁱPr, ^tBu, and
- Ph, wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, Me, ⁱPr, ^tBu, Ph;
- wherein the optionally so formed fused ring system includes in total 9 to 18 ring atoms;
- Q³is at each occurrence independently of each other selected from nitrogen (N) and CR¹², with the provision that at least one Q³is nitrogen (N);
- R¹¹is at each occurrence independently of each other either the binding site of a single bond connecting a first or a second chemical moiety to the third chemical moiety or is independently of each other selected from the group consisting of: hydrogen, deuterium, Me, ⁱPr, ^tBu, and
- Ph, which is optionally substituted with one or more substituents independently of each other selected from the group consisting of: deuterium, Me, ⁱPr, ^tBu, and Ph;
- R¹²is defined as R⁶;
- wherein the maximum number of first and second chemical moieties attached to the third chemical moiety is only limited by the number of available binding sites on the third chemical moiety (in other words: the number of substituents R¹¹) (preferably with the aforementioned provision, that each TADF material E^Bincludes at least one first chemical moiety, at least one second chemical moiety, and exactly one third chemical moiety).

In a preferred embodiment of the invention, a is always 1 and b is always 0.

In a preferred embodiment of the invention, Z²is at each occurrence a direct bond.

In a preferred embodiment of the invention, R^ais at each occurrence hydrogen.

In a preferred embodiment of the invention, R^aand R^dare at each occurrence hydrogen.

In a preferred embodiment of the invention, Q³is at each occurrence nitrogen (N).

In one embodiment of the invention, at least one group R^Xin formula EWG-I is CN.

In a preferred embodiment of the invention, exactly one group R^Xin formula EWG-I is CN.

In a preferred embodiment of the invention, exactly one group R^Xin formula EWG-I is CN and no group R^Xin formula EWG-I is CF₃.

Examples of first chemical moieties according to the present invention are shown below, which does of course not imply that the present invention is limited to these examples:

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- wherein the aforementioned definitions apply.

Examples of second chemical moieties according to the present invention are shown below, which does of course not imply that the present invention is limited to these examples:

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- wherein the aforementioned definitions apply.

In a preferred embodiment of the invention, each TADF material E^Bhas a structure represented by any of formulas E^B-I, E^B-II, E^B-III, E^B-IV, E^B-V, E^B-VI, E^B-VII, E^B-VIII, E^B-IX, E^B-X, and E^B-XI:

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- wherein
- R¹³is defined as R¹¹with the provision that R¹³cannot be a binding site of a single bond connecting a first or a second chemical moiety to the third chemical moiety;
- R^Yis selected from CN and CF₃or R^Yincludes or consists of a structure according to formula BN-I:

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- which is bonded to the structure of formula E^B-I, E^B-II, E^B-III, E^B-IV, E^B-V, E^B-VI, E^B-VII, E^B-VIII or E^B-IX via a single bond indicated by the dashed line and wherein exactly one R^BNgroup is CN while the other two R^BNgroups are both hydrogen (H);
- and wherein apart from that the above-mentioned definitions apply.

In a preferred embodiment of the invention, R¹³is at each occurrence hydrogen.

In one embodiment of the invention, R^Yis at each occurrence CN.

In one embodiment of the invention, R^Yis at each occurrence CF₃.

In one embodiment of the invention, R^Yis at each occurrence a structure represented by formula BN-I.

In a preferred embodiment of the invention, R^Yis at each occurrence independently of each other selected from CN and a structure represented by formula BN-I.

In a preferred embodiment of the invention, each TADF material E^Bhas a structure represented by any of formulas E^B-1, E^B-II, E^B-III, E^B-IV, E^B-V, E^B-VI, E^B-VII, and E^B-X, wherein the aforementioned definitions apply.

In a preferred embodiment of the invention, each TADF material E^Bhas a structure represented by any of formulas E^B-1, E^B-III, E^B-V, E^B-VI, and E^B-X, wherein the aforementioned definitions apply.

Examples of TADF materials E^Bfor use in organic electroluminescent devices according to the invention are listed in the following, whereat this does not imply that only the shown examples are suitable TADF materials E^Bin the context of the present invention.

Non-limiting examples of TADF materials E^Baccording formula E^B-1 are shown below:

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Non-limiting examples of TADF materials E^Baccording formula E^B-11 are shown below:

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Non-limiting examples of TADF materials E^Baccording formula E^B-111 are shown below:

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Non-limiting examples of TADF materials E^Baccording formula E^B-IV are shown below:

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Non-limiting examples of TADF materials E^Baccording formula E^B-V are shown below:

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Non-limiting examples of TADF materials E^Baccording formula E^B-VI are shown below:

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Non-limiting examples of TADF materials E^Baccording formula E^B-VII are shown below:

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Non-limiting examples of TADF materials E^Baccording formula E^B-VIII are shown below:

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Non-limiting examples of TADF materials E^Baccording formula E^B-IX are shown below:

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Non-limiting examples of TADF materials E^Baccording formula E^B-X are shown below:

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Non-limiting examples of TADF materials E^Baccording formula E^B-XI are shown below:

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The synthesis of TADF materials E^Bcan be accomplished via standard reactions and reaction conditions known to the skilled artisan. Typically, in a first step, a coupling reaction, preferably a palladium-catalyzed coupling reaction, may be performed, which is exemplarily shown below for the synthesis of TADF materials E^Baccording to any of formulas E^B-III, E^B-IV, and E^B-V:

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E1 can be any boronic acid (R^B=H) or an equivalent boronic acid ester (R^B=alkyl or aryl), in particular two R^Bmay form a ring to give e.g., boronic acid pinacol esters. As second reactant E2 is used, wherein Hal refers to halogen and may be I, Br or Cl, but preferably is Br. Reaction conditions of such palladium-catalyzed coupling reactions are known the person skilled in the art, e.g., from WO 2017/005699, and it is known that the reacting groups of E1 and E2 can be interchanged as shown below to optimize the reaction yields:

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In a second step, the TADF molecules are obtained via the reaction of a nitrogen heterocycle in a nucleophilic aromatic substitution with the aryl halide, preferably aryl fluoride E3. Typical conditions include the use of a base, such as tribasic potassium phosphate or sodium hydride, for example, in an aprotic polar solvent, such as dimethyl sulfoxide (DMSO) or N,N-dimethylformamide (DMF), for example.

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In particular, the donor molecule E4 is a 3,6-substituted carbazole (e.g., 3,6-dimethylcarbazole, 3,6-diphenylcarbazole, 3,6-di-tert-butylcarbazole), a 2,7-substituted carbazole (e.g., 2,7-dimethylcarbazole, 2,7-diphenylcarbazole, 2,7-di-tert-butylcarbazole), a 1,8-substituted carbazole (e.g., 1,8-dimethylcarbazole, 1,8-diphenylcarbazole, 1,8-di-tert-butylcarbazole), a 1-substituted carbazole (e.g., 1-methylcarbazole, 1-phenylcarbazole, 1-tert-butylcarbazole), a 2-substituted carbazole (e.g., 2-methylcarbazole, 2-phenylcarbazole, 2-tert-butylcarbazole), or a 3-substituted carbazole (e.g., 3-methylcarbazole, 3-phenylcarbazole, 3-tert-butylcarbazole).

Alternatively, a halogen-substituted carbazole, particularly 3-bromocarbazole, can be used as E4.

In a subsequent reaction, a boronic acid ester functional group or boronic acid functional group may be exemplarily introduced at the position of the one or more halogen substituents, which was introduced via E4, to yield the corresponding carbazol-3-yl-boronic acid ester or carbazol-3-yl-boronic acid, e.g., via the reaction with bis(pinacolato)diboron (CAS No. 73183-34-3). Subsequently, one or more substituents R^a, R^bor R^dmay be introduced in place of the boronic acid ester group or the boronic acid group via a coupling reaction with the corresponding halogenated reactant, e.g., R^a-Hal, preferably R^a—Cl and R^a—Br.

Alternatively, one or more substituents R^a, R^bor R^dmay be introduced at the position of the one or more halogen substituents, which was introduced via D-H, via the reaction with a boronic acid of the substituent R^a[R^a—B(OH)₂], R^b[R^b—B(OH)₂] or R^d[R^d—B(OH)₂] or a corresponding boronic acid ester.

Further TADF materials E^Bmay be obtained analogously. A TADF material E^Bmay also be obtained by any alternative synthesis route suitable for this purpose.

An alternative synthesis route may include the introduction of a nitrogen heterocycle via copper- or palladium-catalyzed coupling to an aryl halide or aryl pseudohalide, preferably an aryl bromide, an aryl iodide, aryl triflate or an aryl tosylate.

Phosphorescence Material(s) P^B

The phosphorescence materials P^Bin the context of the present invention utilize the intramolecular spin-orbit interaction (heavy atom effect) caused by metal atoms to obtain light emission from triplets.

Generally, it is understood, that all phosphorescent complexes that are used in organic electroluminescent devices in the state of the art may also be used in an organic electroluminescent device according to the present invention.

It is common knowledge to those skilled in the art that phosphorescence materials P^Bused in organic electroluminescent devices are oftentimes complexes of Ir, Pt, Pd, Au, Os, Eu, Ru, Re, Ag and Cu, in the context of this invention preferably of Ir, Pt, and Pd, more preferably of Ir and Pt. The skilled artisan knows which materials are suitable as phosphorescence materials in organic electroluminescent devices and how to synthesize them. Furthermore, the skilled artisan is familiar with the design principles of phosphorescent complexes for use in organic electroluminescent devices and knows how to tune the emission of the complexes by means of structural variations.

See for example: C.-L. Ho, H. Li, W.-Y. Wong, Journal of Organometallic Chemistry 2014, 751, 261, DOI: 10.1016/j.jorganchem.2013.09.035; T. Fleetham, G. Li, J. Li, Advanced Science News 2017, 29, 1601861, DOI: 10.1002/adma.201601861; A. R. B. M. Yusoff, A. J. Huckaba, M. K. Nazeeruddin, Topics in Current Chemistry (Z) 2017, 375:39, 1, DOI: 10.1007/s41061-017-0126-7; T.-Y. Li, J. Wuc, Z.-G. Wua, Y.-X. Zheng, J.-L. Zuo, Y. Pan, Coordination Chemistry Reviews 2018, 374, 55, DOI: 10.1016/j.ccr.2018.06.014.

For example, US2020274081 (A1), US20010019782 (A1), US20020034656 (A1), US20030138657 (A1), US2005123791 (A1), US20060065890 (A1), US20060134462 (A1), US20070034863 (A1), US20070111026 (A1), US2007034863 (A1), US2007138437 (A1), US20080020237 (A1), US20080297033 (A1), US2008210930 (A1), US20090115322 (A1), US2009104472 (A1), US20100244004 (A1), US2010105902 (A1), US20110057559 (A1), US2011215710 (A1), US2012292601 (A1), US2013165653 (A1), US20140246656 (A1), US20030068526 (A1), US20050123788 (A1), US2005260449 (A1), US20060127696 (A1), US20060202194 (A1), US20070087321 (A1), US20070190359 (A1), US2007104979 (A1), US2007224450 (A1), US20080233410 (A1), US200805851 (A1), US20090039776 (A1), US20090179555 (A1), US20100090591 (A1), US20100295032 (A1), US20030072964 (A1), US20050244673 (A1), US20060008670 (A1), US20060134459 (A1), US20060251923 (A1), US20070103060 (A1), US20070231600 (A1), US2007104980 (A1), US2007278936 (A1), US20080261076 (A1), US2008161567 (A1), US20090108737 (A1), US2009085476 (A1), US20100148663 (A1), US2010102716 (A1), US2010270916 (A1), US20110204333 (A1), US2011285275 (A1), US2013033172 (A1), US2013334521 (A1), US2014103305 (A1), US2003068536 (A1), US2003085646 (A1), US2006228581 (A1), US2006197077 (A1), US2011114922 (A1), US2011114922 (A1), US2003054198 (A1), and EP2730583 (A1) disclose phosphorescence materials that may be used as phosphorescence materials P^Bin the context of the present invention. It is understood that this does not imply that the present invention is limited to organic electroluminescent devices including a phosphorescence materials described in one of the named references.

As laid out in US2020274081 (A1), examples of phosphorescent complexes for use in organic electroluminescent devices such as those of the present invention include the complexes shown below. Again, it is understood that the present invention is not limited to these examples.

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As stated above, the skilled artisan will realize that any phosphorescent complexes used in the state of the art may be suitable as phosphorescence materials P^Bin the context of the present invention.

In one embodiment of the invention, each phosphorescence material P^Bincludes Iridium (Ir).

In one embodiment of the invention, the at least one phosphorescence material P^B, preferably each phosphorescence material P^B, is an organometallic complex including either iridium (Ir) or platinum (Pt).

In one embodiment of the invention, the at least one phosphorescence material P^B, preferably each phosphorescence material P^B, is an organometallic complex including iridium (Ir).

In one embodiment of the invention, the at least one phosphorescence material P^B, preferably each phosphorescence material P^B, is an organometallic complex including platinum (Pt).

Non-limiting examples of phosphorescence materials P^Balso include compounds represented by the following general formula P^B-I,

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In formula P^B-I, M is selected from the group consisting of Ir, Pt, Au, Eu, Ru, Re, Ag and Cu;

- n is an integer of 1 to 3; and
- X²and Y¹together form at each occurrence independently from each other a bidentate monoanionic ligand.

In one embodiment of the invention, each phosphorescence materials P^Bincludes or consists of a structure according to formula P^B-I,

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- wherein, M is selected from the group consisting of Ir, Pt, Au, Eu, Ru, Re, Ag and Cu;
- n is an integer of 1 to 3; and
- X²and Y¹together form at each occurrence independently from each other a bidentate monoanionic ligand.

Examples of the compounds represented by the formula P^B-I include compounds represented by the following general formula P^B-II or general formula P^B-III:

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In formulas P^B-II and P^B-III, X¹is an aromatic ring which is carbon (C)-bonded to M and Y′ is a ring, which is nitrogen (N)-coordinated to M to form a ring.

X′ and Y′ are bonded, and X′ and Y′ may form a new ring. In formula P^B-III, Z³is a bidentate ligand having two oxygens (O). In the formulas P^B-II and P^B-III, M is preferably Ir from the viewpoint of high efficiency and long lifetime.

In the formulas P^B-II and P^B-III, the aromatic ring X is for example a C₆-C₃₀-aryl, preferably a C₆-C₁₆-aryl, even more preferably a C₆-C₁₂-aryl, and particularly preferably a C₆-C₁₀-aryl, wherein X′ at each occurrence is optionally substituted with one or more substituents R^E.

In the formulas P^B-II and P^B-III, Y′ is for example a C₂-C₃₀-heteroaryl, preferably a C₂-C₂₅-heteroaryl, more preferably a C₂-C₂₀-heteroaryl, even more preferably a C₂-C₁₅-heteroaryl, and particularly preferably a C₂-C₁₀-heteroaryl, wherein Y′ at each occurrence is optionally substituted with one or more substituents R^E. Furthermore, Y′ may be, for example, a C₁-C₅-heteroaryl, which is optionally substituted with one or more substituents R^E.

In the formulas P^B-II and P^B-III, the bidentate ligand having two oxygens (O) Z³is for example a C₂-C₃₀-bidentate ligand having two oxygens, a C₂-C₂₅-bidentate ligand having two oxygens, more preferably a C₂-C₂₀-bidentate ligand having two oxygens, even more preferably a C₂-C₁₅-bidentate ligand having two oxygens, and particularly preferably a C₂-C₁₀-bidentate ligand having two oxygens, wherein Z³at each occurrence is optionally substituted with one or more substituents R^E. Furthermore, Z³may be, for example, a C₂-C₅-bidentate ligand having two oxygens, which is optionally substituted with one or more substituents R^E.

R^Eis at each occurrence independently from another selected from the group consisting of hydrogen, deuterium, N(R^5E)₂, OR^5E,

- SR^5E, Si(R^5E)₃, CF₃, CN, halogen,
- C₁-C₄₀-alkyl, which is optionally substituted with one or more substituents R^5Eand wherein one or more non-adjacent CH₂-groups are optionally substituted by R^5EC═CR^5E, C≡C, Si(R^5E)₂, Ge(R^5E)₂, Sn(R^5E)₂, C═O, C═S, C═Se, C═NR^5E, P(═O)(R^5E), SO, SO₂, NR^5E, O, S or CONR^5E;
- C₁-C₄₀-thioalkoxy, which is optionally substituted with one or more substituents R^5Eand wherein one or more non-adjacent CH₂-groups are optionally substituted by R^5EC═CR^5E, C≡C, Si(R^5E)₂, Ge(R^5E)₂, Sn(R^5E)₂, C═O, C═S, C═Se, C═NR^5E, P(═O)(R^5E), SO, SO₂, NR^5E, 0, S or CONR^5E;
- C₆-C₆₀-aryl, which is optionally substituted with one or more substituents R^5E; and
- C₃-C₅₇-heteroaryl, which is optionally substituted with one or more substituents R^5E.
- R^5Eis at each occurrence independently from another selected from the group consisting of hydrogen, deuterium, N(R^6E)₂, OR^6E, SR^6E, Si(R^6E)₃, CF₃, CN, F,
- C₁-C₄₀-alkyl, which is optionally substituted with one or more substituents R^6Eand wherein one or more non-adjacent CH₂-groups are optionally substituted by R^6EC═CR^6E, C≡C, Si(R^6E)₂, Ge(R^6E)₂, Sn(R^6E)₂, C═O, C═S, C═Se, C═NR^6E, P(═O)(R^6E), SO, SO₂, NR^6E, O, S or CONR^6E;
- C₆-C₆₀-aryl, which is optionally substituted with one or more substituents R^6E; and
- C₃-C₅₇-heteroaryl, which is optionally substituted with one or more substituents R^6E.

R^6Eis at each occurrence independently from another selected from the group consisting of hydrogen, deuterium, OPh, CF₃, CN, F,

- C₁-C₅-alkyl, wherein one or more hydrogen atoms are optionally, independently from each other substituted by deuterium, CN, CF₃, or F;
- C₁-C₅-alkoxy,
- wherein one or more hydrogen atoms are optionally, independently from each other substituted by deuterium, CN, CF₃, or F;
- C₁-C₅-thioalkoxy,
- wherein one or more hydrogen atoms are optionally, independently from each other substituted by deuterium, CN, CF₃, or F;
- C₆-C₁₈-aryl, which is optionally substituted with one or more C₁-C₅-alkyl substituents;
- C₃-C₁₇-heteroaryl,
- which is optionally substituted with one or more C₁-C₅-alkyl substituents;
- N(C₆-C₁₈-aryl)₂;
- N(C₃-C₁₇-heteroaryl)₂, and
- N(C₃-C₁₇-heteroaryl)(C₆-C₁₈-aryl).

The substituents R^E, R^5E, or R^6Eindependently from each other optionally may form a mono- or polycyclic, aliphatic, aromatic, heteroaromatic and/or benzo-fused ring system with one or more substituents R^E, R^5E, R^6E, and/or with X′, Y′ and Z³.

Examples of the compound represented by formula P^B-II include Ir(ppy)₃, Ir(ppy)₂(acac), Ir(mppy)₃, Ir(PPy)₂(m-bppy), and BtpIr(acac), Ir(btp)₂(acac), Ir(2-phq)₃, Hex-Ir(phq)₃, Ir(fbi)₂(acac), fac-Tris(2-(3-p-xylyl)phenyl)pyridine iridium(III), Eu(dbm)₃(Phen), Ir(piq)₃, Ir(piq)₂(acac), Ir(Fiq)₂(acac), Ir(Flq)₂(acac), Ru(dtb-bpy)₃.2(PF6), Ir(2-phq)₃, Ir(BT)₂(acac), Ir(DMP)₃, Ir(Mpq)₃, Ir(phq)₂tpy, fac-Ir(ppy)₂Pc, Ir(dp)PQ₂, Ir(Dpm)(Piq)₂, Hex-Ir(piq)₂(acac), Hex-Ir(piq)₃, Ir(dmpq)₃, Ir(dmpq)₂(acac), FPQIrpic and the like.

Other examples of the compound represented by formula P^B-II include compounds represented by the following formulas P^B-II-1 to P^B-II-11. In the structural formula, “Me” represents a methyl group.

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Other examples of the compound represented by the formula P^B-III include compounds represented by the following formulas P^B-III-1 to P^B-III-6. In the structural formula, “Me” represents a methyl group.

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Furthermore, the iridium complexes described in US2003017361 (A1), US2004262576 (A1), WO2010027583 (A1), US2019245153 (A1), US2013119354 (A1), US2019233451 (A1), may be used. From the viewpoint of high efficiency in phosphorescence materials, Ir(ppy)₃and Hex-Ir(ppy)₃are often used for green light emission.

Small FWHM Emitter(s) S^B

A small full width at half maximum (FWHM) emitter S^Bin the context of the present invention is any emitter that has an emission spectrum, which exhibits an FWHM of less than or equal to 0.25 eV (≤0.25 eV), typically measured from a spin-coated film with 1 to 5% by weight, in particular with 2% by weight of emitter in poly(methyl methacrylate) PMMA at room temperature (i.e., (approximately) 20° C.). Alternatively, emission spectra of small FWHM emitters S^Bmay be measured in a solution, typically with 0.001-0.2 mg/mL of the emitter S^Bin dichloromethane or toluene at room temperature (i.e., (approximately) 20° C.).

In a preferred embodiment of the invention, a small FWHM emitter S^Bis any emitter that has an emission spectrum, which exhibits an FWHM of ≤0.24 eV, more preferably of ≤0.23 eV, even more preferably of ≤0.22 eV, of ≤0.21 eV or of ≤0.20 eV, measured from a spin-coated film with 1 to 5% by weight, in particular with 2% by weight of emitter S^Bin PMMA at room temperature. Alternatively, emission spectra of small FWHM emitters S^Bmay be measured in a solution, typically with 0.001-0.2 mg/mL of the emitter S^Bin dichloromethane or toluene at room temperature (i.e., (approximately) 20° C.). In other embodiments of the present invention, each small FWHM emitter S^Bexhibits an FWHM of ≤0.19 eV, of ≤0.18 eV, of ≤0.17 eV, of ≤0.16 eV, of ≤0.15 eV, of ≤0.14 eV, of ≤0.13 eV, of ≤0.12 eV, or of ≤0.11 eV.

In one embodiment of the invention, each small FWHM emitter S^Bemits light with an emission maximum in the wavelength range of from 400 nm to 470 nm, measured (with 1 to 5% by weight, in particular with 2% by weight of the emitter S^B) in PMMA at room temperature.

In one embodiment of the invention, each small FWHM emitter S^Bemits light with an emission maximum in the wavelength range of from 500 nm to 560 nm, measured (with 1 to 5% by weight, in particular with 2% by weight of the emitter S^B) in PMMA at room temperature.

In one embodiment of the invention, each small FWHM emitter S^Bemits light with an emission maximum in the wavelength range of from 610 nm to 665 nm, measured (with 1 to 5% by weight, in particular with 2% by weight of the emitter S^B) in PMMA at room temperature.

In one embodiment of the invention, each small FWHM emitter S^Bemits light with an emission maximum in the wavelength range of from 400 nm to 470 nm, measured with 0.001-0.2 mg/mL of the emitter S^Bin dichloromethane or toluene at room temperature (i.e., (approximately) 20° C.).

In one embodiment of the invention, each small FWHM emitter S^Bemits light with an emission maximum in the wavelength range of from 500 nm to 560 nm, measured with 0.001-0.2 mg/mL of the emitter S^Bin dichloromethane or toluene at room temperature (i.e., (approximately) 20° C.).

In one embodiment of the invention, each small FWHM emitter S^Bemits light with an emission maximum in the wavelength range of from 610 nm to 665 nm, measured with 0.001-0.2 mg/mL of the emitter S^Bin dichloromethane or toluene at room temperature (i.e., (approximately) 20° C.).

It is understood that a TADF material E^Bincluded in a light-emitting layer B of an organic electroluminescent device according to the invention may optionally also be an emitter with an emission spectrum which exhibits an FWHM of less than or equal to 0.25 eV (≤0.25 eV). Optionally, a TADF material E^Bincluded in a light-emitting layer B of an organic electroluminescent device according to the invention may also exhibit an emission maximum within the wavelength ranges specified above (namely: 400 nm to 470 nm, 500 nm to 560 nm, 610 nm to 665 nm).

In one embodiment of the invention, one of the relations expressed by the following formulas (23) to (25) applies:

440 nm<λ_max(S^B)<470 nm (23)

510 nm<λ_max(S^B)<550 nm (24)

610 nm<λ_max(S^B)<665 nm (25),

- wherein λ_max(S^B) refers to the emission maximum of a small FWHM emitter S^Bin the context of the present invention.

In one embodiment, the aforementioned relations expressed by formulas (23) to (25) apply to materials included in any of the at least one light-emitting layer B of the organic electroluminescent device according to the invention. In one embodiment, the aforementioned relations expressed by formulas (23) to (25) apply to materials included in the same light-emitting layer B of the organic electroluminescent device according to the invention.

In a preferred embodiment of the invention, each small FWHM emitter S^Bis an organic emitter, which, in the context of the invention, means that it does not contain any transition metals. Preferably, each small FWHM emitter S^Baccording to the invention predominantly consists of the elements hydrogen (H), carbon (C), nitrogen (N), and boron (B), but may for example also include oxygen (O), silicon (Si), fluorine (F), and bromine (Br).

In a preferred embodiment of the invention, each small FWHM emitter S^Bis a fluorescent emitter, which in the context of the present invention means that, upon electronic excitation (for example in an optoelectronic device according to the invention), the emitter is capable of emitting light at room temperature, wherein the emissive excited state is a singlet state.

In one embodiment of the invention, a small FWHM emitter S^Bexhibits a photoluminescence quantum yield (PLQY) equal to or higher than 50%, measured (with 1 to 5% by weight, in particular with 2% by weight of the emitter S^B) in PMMA at room temperature.

In a preferred embodiment of the invention, a small FWHM emitter S^Bexhibits a photoluminescence quantum yield (PLQY) equal to or higher than 60%, measured (with 1 to 5% by weight, in particular with 2% by weight of the emitter S^B) in PMMA at room temperature.

In an even more preferred embodiment of the invention, a small FWHM emitter S^Bexhibits a photoluminescence quantum yield (PLQY) equal to or higher than 70%, measured (with 1 to 5% by weight, in particular with 2% by weight of the emitter S^B) in PMMA at room temperature.

In a still even more preferred embodiment of the invention, a small FWHM emitter S^Bexhibits a photoluminescence quantum yield (PLQY) equal to or higher than 80%, measured (with 1 to 5% by weight, in particular with 2% by weight of the emitter S^B) in PMMA at room temperature.

In a particularly preferred embodiment of the invention, a small FWHM emitter S^Bexhibits a photoluminescence quantum yield (PLQY) equal to or higher than 90%, measured (with 1 to 5% by weight, in particular with 2% by weight of the emitter S^B) in PMMA at room temperature.

In one embodiment of the invention, a small FWHM emitter S^Bexhibits a photoluminescence quantum yield (PLQY) equal to or higher than 50%, measured with 0.001-0.2 mg/mL of the emitter S^Bin dichloromethane or toluene at room temperature (i.e., (approximately) 20° C.).

In a preferred embodiment of the invention, a small FWHM emitter S^Bexhibits a photoluminescence quantum yield (PLQY) equal to or higher than 60%, measured with 0.001-0.2 mg/mL of the emitter S^Bin dichloromethane or toluene at room temperature (i.e., (approximately) 20° C.).

In an even more preferred embodiment of the invention, a small FWHM emitter S^Bexhibits a photoluminescence quantum yield (PLQY) equal to or higher than 70%, measured with 0.001-0.2 mg/mL of the emitter S^Bin dichloromethane or toluene at room temperature (i.e., (approximately) 20° C.).

In a still even more preferred embodiment of the invention, a small FWHM emitter S^Bexhibits a photoluminescence quantum yield (PLQY) equal to or higher than 80%, measured with 0.001-0.2 mg/mL of the emitter S^Bin dichloromethane or toluene at room temperature (i.e., (approximately) 20° C.).

In a particularly preferred embodiment of the invention, a small FWHM emitter S^Bexhibits a photoluminescence quantum yield (PLQY) equal to or higher than 90%, measured with 0.001-0.2 mg/mL of the emitter S^Bin dichloromethane or toluene at room temperature (i.e., (approximately) 20° C.).

The person skilled in the art knows how to design small FWHM emitters S^Bwhich fulfill the above-mentioned requirements or preferred features.

A class of molecules suitable to provide small FWHM emitters S^Bin the context of the present invention are the well-known 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY)-based materials, whose structural features and application in organic electroluminescent devices have been reviewed in detail and are common knowledge to those skilled in the art. The state of the art also reveals how such materials may be synthesized and how to arrive at an emitter with a certain emission color.

See for example: J. Liao, Y. Wang, Y. Xu, H. Zhao, X. Xiao, X. Yang, Tetrahedron 2015, 71(31), 5078, DOI: 10.1016/j.tet.2015.05.054; B. M Squeo, M. Pasini, Supramolecular Chemistry 2020, 32(1), 56-70, DOI: 10.1080/10610278.2019.1691727; M. Poddar, R. Misra, Coordination Chemistry Reviews 2020, 421, 213462-213483; DOI: 10.1016/j.ccr.2020.213462.

The skilled artisan is also familiar with the fact that the BODIPY base structure shown below

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- is not ideally suitable as emitter in an organic electroluminescent device, for example due to intermolecular π-π interactions and the associated self-quenching.

It is common knowledge to those skilled in the art that one may arrive at more suitable emitter molecules for organic electroluminescent devices by attaching bulky groups as substituents to the BODIPY core structure shown above. These bulky groups may for example (among many others) be aryl, heteroaryl, alkyl or alkoxy substituents or condensed polycyclic aromatics, or heteroaromatics, all of which may optionally be substituted. The choice of suitable substituents at the BODIPY core is obvious for the skilled artisan and can easily be derived from the state of the art. The same holds true for the multitude of synthetic pathways which have been established for the synthesis and subsequent modification of such molecules.

See for example: B. M Squeo, M. Pasini, Supramolecular Chemistry 2020, 32(1), 56-70, DOI: 10.1080/10610278.2019.1691727; M. Poddar, R. Misra, Coordination Chemistry Reviews 2020, 421, 213462-213483; DOI: 10.1016/j.ccr.2020.213462.

Examples of BODIPY-based emitters that may be suitable as small FWHM emitters S^Bin the context of the present invention are shown below:

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It is understood that this does not imply that BODIPY-derivatives with other structural features than those shown above are not suited as small FWHM emitters S^Bin the context of the present invention.

For example, the BODIPY-derived structures disclosed in US2020251663 (A1), EP3671884 (A1), US20160230960 (A1), US20150303378 (A1) or derivatives thereof may be suitable small FWHM emitters S^Bfor use according to the present invention.

Furthermore, it is known to those skilled in the art, that one may also arrive at emitters for organic electroluminescent devices by replacing one or both of the fluorine substituents attached to the central boron atom of the BODIPY core structure by alkoxy or aryloxy groups which are attached via the oxygen atom and may optionally be substituted, preferably with electron-withdrawing substituents such as fluorine (F) or trifluoromethyl (CF₃). Such molecules are for example disclosed in US2012037890 (A1) and the person skilled in the art understands that these BODIPY-related compounds may also be suitable small FWHM emitters S^Bin the context of the present invention. Examples of such emitter molecules are shown below, which does not imply that only the shown structures may be suitable small FWHM emitters S^Bin the context of the present invention:

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Additionally, the BODIPY-related boron-containing emitters disclosed in US20190288221 (A1) constitute a group of emitters that may provide suitable small FWHM emitters S^Bfor use according to the present invention.

Another class of molecules suitable to provide small FWHM emitters S^Bin the context of the invention are near-range-charge-transfer (NRCT) emitters.

Typical NRCT emitters are described in the literature to show a delayed component in the time-resolved photoluminescence spectrum and exhibit a near-range HOMO-LUMO separation. See for example: T. Hatakeyama, K. Shiren, K. Nakajima, S. Nomura, S. Nakatsuka, K. Kinoshita, J. Ni, Y. Ono, and T. Ikuta, Advanced Materials 2016, 28(14), 2777, DOI: 10.1002/adma.201505491.

Typical NRCT emitters only show one emission band in the emission spectrum, wherein typical fluorescence emitters display several distinct emission bands due to vibrational progression.

The skilled artisan knows how to design and synthesize NRCT emitters that may be suitable as small FWHM emitters S^Bin the context of the present invention. For example, the emitters disclosed in EP3109253 (A1) may be used as small FWHM emitters S^Bin the context of the present invention.

Furthermore, for example, US2014058099 (A1), US2009295275 (A1), US2012319052 (A1), EP2182040 (A2), US2018069182 (A1), US2019393419 (A1), US2020006671 (A1), US2020098991 (A1), US2020176684 (A1), US2020161552 (A1), US2020227639 (A1), US2020185635 (A1), EP3686206 (A1), EP3686206 (A1), WO2020217229 (A1), WO2020208051 (A1), and US2020328351 (A1) disclose emitter materials that may be suitable as small FWHM emitters S^Bfor use according to the present invention.

A group of emitters that may be used as small FWHM emitters S^Bin the context of the present invention are the boron (B)-containing emitters including or consisting of a structure according to the following formula DABNA-I:

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- wherein
- each of ring A′, ring B′, and ring C′ independently of each other represents an aromatic or heteroaromatic ring, each including 5 to 24 ring atoms, out of which, in case of a heteroaromatic ring, 1 to 3 ring atoms are heteroatoms independently of each other selected from N, O, S, and Se; wherein
- one or more hydrogen atoms in each of the aromatic or heteroaromatic rings A′, B′, and C′ are optionally and independently of each other substituted by a substituent R^DABNA-1, which is at each occurrence independently of each other selected from the group consisting of: deuterium, N(R^DABNA-2)₂, OR^DABNA-2, SR^DABNA-2, Si(R^DABNA-2)₃, B(OR^DABNA-2)₂, OSO₂R^DABNA-2, CF₃, CN, halogen (F, Cl, Br, I),
- C₁-C₄₀-alkyl,
- which is optionally substituted with one or more substituents R^DABNA-2and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^DABNA-2C═CR^DABNA-2, C≡C, Si(R^DABNA-2)₂, Ge(R^DABNA-2)₂, Sn(R^DABNA-2)₂, C═O, C═S, C═Se, C═NR^DABNA-2, P(═O)(R^DABNA-2), SO, SO₂, NR^DABNA-2, O, S or CONR^DABNA-2;
- C₁-C₄₀-alkoxy,
- which is optionally substituted with one or more substituents R^DABNA-2and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^DABNA-2C═CR^DABNA-2, C≡C, Si(R^DABNA-2)₂, Ge(R^DABNA-2)₂, Sn(R^DABNA-2)₂, C═O, C═S, C═Se, C═NR^DABNA-2, P(═O)(R^DABNA-2), SO, SO₂, NR^DABNA-2, O, S or CONR^DABNA-2;
- C₁-C₄₀-thioalkoxy,
- which is optionally substituted with one or more substituents R^DABNA-2and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^DABNA-2C═CR^DABNA-2, C≡C, Si(R^DABNA-2)₂, Ge(R^DABNA-2)₂, Sn(R^DABNA-2)₂, C═O, C═S, C═Se, C═NR^DABNA-2, P(═O)(R^DABNA-2), SO, SO₂, NR^DABNA-2, O, S or CONR^DABNA-2;
- C₂-C₄₀-alkenyl,
- which is optionally substituted with one or more substituents R^DABNA-2and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^DABNA-2C═CR^DABNA-2, C≡C, Si(R^DABNA-2)₂, Ge(R^DABNA-2)₂, Sn(R^DABNA-2)₂, C═O, C═S, C═Se, C═NR^DABNA-2, P(═O)(R^DABNA-2), SO, SO₂, NR^DABNA-2, O, S or CONR^DABNA-2;
- C₂-C₄₀-alkynyl,
- which is optionally substituted with one or more substituents R^DABNA-2and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^DABNA-2C═CR^DABNA-2, Si(R^DABNA-2)₂, Ge(R^DABNA-2)₂, Sn(R^DABNA-2)₂, C═O, C═S, C═Se, C═NR^DABNA-2, P(═O)(R^DABNA-2), SO, SO₂, NR^DABNA-2, O, S or CONR^DABNA-2;
- C₆-C₆₀-aryl,
- which is optionally substituted with one or more substituents R^DABNA-2;
- C₃-C₅₇-heteroaryl,
- which is optionally substituted with one or more substituents R^DABNA-2;
- and aliphatic, cyclic amines including 4 to 18 carbon atoms and 1 to 3 nitrogen atoms;
- R^DABNA-2is at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, N(R^DABNA-6)₂, OR^DABNA-6, SR^DABNA-6, Si(R^DABNA-6)₃, B(OR^DABNA-6)₂, OSO₂R^DABNA-6, CF₃, CN, halogen (F, Cl, Br, I),
- C₁-C₅-alkyl,
- which is optionally substituted with one or more substituents R^DABNA-6and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^DABNA-6C═CR^DABNA-6, C≡C, Si(R^DABNA-6)₂, Ge(R^DABNA-6)₂, Sn(R^DABNA-6)₂, C═O, C═S, C═Se, C═NR^DABNA-6, P(═O)(R^DABNA-6), SO, SO₂, NR^DABNA-6, O, S or CONR^DABNA-6;
- C₁-C₅-alkoxy,
- which is optionally substituted with one or more substituents R^DABNA-6and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^DABNA-6C═CR^DABNA-6, C≡C, Si(R^DABNA-6)₂, Ge(R^DABNA-6)₂, Sn(R^DABNA-6)₂, C═O, C═S, C═Se, C═NR^DABNA-6, P(═O)(R^DABNA-6), SO, SO₂, NR^DABNA-6, O, S or CONR^DABNA-6;
- C₁-C₅-thioalkoxy,
- which is optionally substituted with one or more substituents R^DABNA-6and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^DABNA-6C═CR^DABNA-6, C≡C, Si(R^DABNA-6)₂, Ge(R^DABNA-6)₂, Sn(R^DABNA-6)₂, C═O, C═S, C═Se, C═NR^DABNA-6, P(═O)(R^DABNA-6), SO, SO₂, NR^DABNA-6, O, S or CONR^DABNA-6;
- C₂-C₅-alkenyl,
- which is optionally substituted with one or more substituents R^DABNA-6and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^DABNA-6C═CR^DABNA-6, C≡C, Si(R^DABNA-6)₂, Ge(R^DABNA-6)₂, Sn(R^DABNA-6)₂, C═O, C═S, C═Se, C═NR^DABNA-6, P(═O)(R^DABNA-6), SO, SO₂, NR^DABNA-6, O, S or CONR^DABNA-6;
- C₂-C₅-alkynyl,
- which is optionally substituted with one or more substituents R^DABNA-6and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^DABNA-6C═CR^DABNA-6, Si(R^DABNA-6)₂, Ge(R^DABNA-6)₂, Sn(R^DABNA-6)₂, C═O, C═S, C═Se, C═NR^DABNA-6, P(═O)(R^DABNA-6), SO, SO₂, NR^DABNA-6, O, S or CONR^DABNA-6;
- C₆-C₁₈-aryl,
- which is optionally substituted with one or more substituents R^DABNA-6;
- C₃-C₁₇-heteroaryl,
- which is optionally substituted with one or more substituents R^DABNA-6;
- and aliphatic, cyclic amines including 4 to 18 carbon atoms and 1 to 3 nitrogen atoms;
- wherein two or more adjacent substituents selected from R^DABNA-1and R^DABNA-2optionally form a mono- or polycyclic, aliphatic or aromatic or heteroaromatic, carbocyclic or heterocyclic ring system which is fused to the adjacent ring A′, B′ or C′, wherein the optionally so formed fused ring system (i.e., the respective ring A′, B′ or C′ and the additional ring(s) that are optionally fused to it) includes in total 8 to 30 ring atoms;
- Y^aand Y^bare independently of each other selected from a direct (single) bond, NR^DABNA-3, O, S, C(R^DABNA-3)₂, Si(R^DABNA-3)₂, BR^DABNA-3and Se;
- R^DABNA-3is at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, N(R^DABNA-4)₂, OR^DABNA-4, SR^DABNA-4, Si(R^DABNA-4)₃, B(OR^DABNA-4)₂, OSO₂R^DABNA-4, CF₃, CN, halogen (F, Cl, Br, I),
- C₁-C₄₀-alkyl,
- which is optionally substituted with one or more substituents R^DABNA-4and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^DABNA-4C═CR^DABNA-4, C≡C, Si(R^DABNA-4)₂, Ge(R^DABNA-4)₂, Sn(R^DABNA-4)₂, C═O, C═S, C═Se, C═NR^DABNA-4, P(═O)(R^DABNA-4), SO, SO₂, NR^DABNA-4, O, S or CONR^DABNA-4;
- C₁-C₄₀-alkoxy,
- which is optionally substituted with one or more substituents R^DABNA-4and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^DABNA-4C═CR^DABNA-4, C≡C, Si(R^DABNA-4)₂, Ge(R^DABNA-4)₂, Sn(R^DABNA-4)₂, C═O, C═S, C═Se, C═NR^DABNA-4, P(═O)(R^DABNA-4), SO, SO₂, NR^DABNA-4, O, S or CONR^DABNA-4;
- C₁-C₄₀-thioalkoxy,
- which is optionally substituted with one or more substituents R^DABNA-4and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^DABNA-4C═CR^DABNA-4, C≡C, Si(R^DABNA-4)₂, Ge(R^DABNA-4)₂, Sn(R^DABNA-4)₂, C═O, C═S, C═Se, C═NR^DABNA-4, P(═O)(R^DABNA-4), SO, SO₂, NR^DABNA-4, O, S or CONR^DABNA-4;
- C₂-C₄₀-alkenyl,
- which is optionally substituted with one or more substituents R^DABNA-4and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^DABNA-4C═CR^DABNA-4, C≡C, Si(R^DABNA-4)₂, Ge(R^DABNA-4)₂, Sn(R^DABNA-4)₂, C═O, C═S, C═Se, C═NR^DABNA-4, P(═O)(R^DABNA-4), SO, SO₂, NR^DABNA-4, O, S or CONR^DABNA-4;
- C₂-C₄₀-alkynyl,
- which is optionally substituted with one or more substituents R^DABNA-4and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^DABNA-4C═CR^DABNA-4, Si(R^DABNA-4)₂, Ge(R^DABNA-4)₂, Sn(R^DABNA-4)₂, C═O, C═S, C═Se, C═NR^DABNA-4, P(═O)(R^DABNA-4), SO, SO₂, NR^DABNA-4, O, S or CONR^DABNA-4;
- C₆-C₆₀-aryl,
- which is optionally substituted with one or more substituents R^DABNA-4;
- C₃-C₅₇-heteroaryl,
- which is optionally substituted with one or more substituents R^DABNA-4;
- and aliphatic, cyclic amines including 4 to 18 carbon atoms and 1 to 3 nitrogen atoms;
- R^DABNA-4is at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, N(R^DABNA-5)₂, OR^DABNA-5, SR^DABNA-5, Si(R^DABNA-5)₃, B(OR^DABNA-5)₂, OSO₂R^DABNA-5, CF₃, CN, halogen (F, Cl, Br, I),
- C₁-C₄₀-alkyl,
- which is optionally substituted with one or more substituents R^DABNA-5and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^DABNA-5C═CR^DABNA-5, C≡C, Si(R^DABNA-5)₂, Ge(R^DABNA-5)₂, Sn(R^DABNA-5)₂, C═O, C═S, C═Se, C═NR^DABNA-5, P(═O)(R^DABNA-5), SO, SO₂, NR^DABNA-5, O, S or CONR^DABNA-5;
- C₁-C₄₀-alkoxy,
- which is optionally substituted with one or more substituents R^DABNA-5and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^DABNA-5C═CR^DABNA-5, C≡C, Si(R^DABNA-5)₂, Ge(R^DABNA-5)₂, Sn(R^DABNA-5)₂, C═O, C═S, C═Se, C═NR^DABNA-5, P(═O)(R^DABNA-5), SO, SO₂, NR^DABNA-5, O, S or CONR^DABNA-5;
- C₁-C₄₀-thioalkoxy,
- which is optionally substituted with one or more substituents R^DABNA-5and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^DABNA-5C═CR^DABNA-5, C≡C, Si(R^DABNA-5)₂, Ge(R^DABNA-5)₂, Sn(R^DABNA-5)₂, C═O, C═S, C═Se, C═NR^DABNA-5, P(═O)(R^DABNA-5), SO, SO₂, NR^DABNA-5, O, S or CONR^DABNA-5;
- C₂-C₄₀-alkenyl,
- which is optionally substituted with one or more substituents R^DABNA-5and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^DABNA-5C═CR^DABNA-5, C≡C, Si(R^DABNA-5)₂, Ge(R^DABNA-5)₂, Sn(R^DABNA-5)₂, C═O, C═S, C═Se, C═NR^DABNA-5, P(═O)(R^DABNA-5), SO, SO₂, NR^DABNA-5, O, S or CONR^DABNA-5;
- C₂-C₄₀-alkynyl,
- which is optionally substituted with one or more substituents R^DABNA-5and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^DABNA-5C═CR^DABNA-5, Si(R^DABNA-5)₂, Ge(R^DABNA-5)₂, Sn(R^DABNA-5)₂, C═O, C═S, C═Se, C═NR^DABNA-5, P(═O)(R^DABNA-5), SO, SO₂, NR^DABNA-5, O, S or CONR^DABNA-5;
- C₆-C₆₀-aryl,
- which is optionally substituted with one or more substituents R^DABNA-5
- C₃-C₅₇-heteroaryl,
- which is optionally substituted with one or more substituents R^DABNA-5
- and aliphatic, cyclic amines including 4 to 18 carbon atoms and 1 to 3 nitrogen atoms;
- R^DABNA-5is at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, N(R^DABNA-6)₂, OR^DABNA-6, SR^DABNA-6, Si(R^DABNA-6)₃, B(OR^DABNA-6)₂, OSO₂R^DABNA-6, CF₃, CN, halogen (F, Cl, Br, I),
- C₁-C₅-alkyl,
- which is optionally substituted with one or more substituents R^DABNA-6and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^DABNA-6C═CR^DABNA-6, C≡C, Si(R^DABNA-6)₂, Ge(R^DABNA-6)₂, Sn(R^DABNA-6)₂, C═O, C═S, C═Se, C═NR^DABNA-6, P(═O)(R^DABNA-6), SO, SO₂, NR^DABNA-6, O, S or CONR^DABNA-6;
- C₁-C₅-alkoxy,
- which is optionally substituted with one or more substituents R^DABNA-6and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^DABNA-6C═CR^DABNA-6, C≡C, Si(R^DABNA-6)₂, Ge(R^DABNA-6)₂, Sn(R^DABNA-6)₂, C═O, C═S, C═Se, C═NR^DABNA-6, P(═O)(R^DABNA-6), SO, SO₂, NR^DABNA-6, O, S or CONR^DABNA-6;
- C₁-C₅-thioalkoxy,
- which is optionally substituted with one or more substituents R^DABNA-6and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^DABNA-6C═CR^DABNA-6, C≡C, Si(R^DABNA-6)₂, Ge(R^DABNA-6)₂, Sn(R^DABNA-6)₂, C═O, C═S, C═Se, C═NR^DABNA-6, P(═O)(R^DABNA-6), SO, SO₂, NR^DABNA-6, O, S or CONR^DABNA-6;
- C₂-C₅-alkenyl,
- which is optionally substituted with one or more substituents R^DABNA-6and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^DABNA-6C═CR^DABNA-6, C≡C, Si(R^DABNA-6)₂, Ge(R^DABNA-6)₂, Sn(R^DABNA-6)₂, C═O, C═S, C═Se, C═NR^DABNA-6, P(═O)(R^DABNA-6), SO, SO₂, NR^DABNA-6, O, S or CONR^DABNA-6;
- C₂-C₅-alkynyl,
- which is optionally substituted with one or more substituents R^DABNA-6and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^DABNA-6C═CR^DABNA-6, Si(R^DABNA-6)₂, Ge(R^DABNA-6)₂, Sn(R^DABNA-6)₂, C═O, C═S, C═Se, C═NR^DABNA-6, P(═O)(R^DABNA-6), SO, SO₂, NR^DABNA-6, O, S or CONR^DABNA-6;
- C₆-C₁₈-aryl,
- which is optionally substituted with one or more substituents R^DABNA-6;
- C₃-C₁₇-heteroaryl,
- which is optionally substituted with one or more substituents R^DABNA-6;
- and aliphatic, cyclic amines including 4 to 18 carbon atoms and 1 to 3 nitrogen atoms;
- wherein two or more adjacent substituents selected from R^DABNA-3, R^DABNA-4, and R^DABNA-5optionally form a mono- or polycyclic, aliphatic or aromatic or heteroaromatic, carbocyclic or heterocyclic ring system with each other, wherein the optionally so formed ring system includes in total 8 to 30 ring atoms;
- R^DABNA-6is at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, OPh (Ph=phenyl), SPh, CF₃, CN, F, Si(C₁-C₅-alkyl)₃, Si(Ph)₃,
- C₁-C₅-alkyl,
- wherein optionally one or more hydrogen atoms are independently substituted by deuterium, Ph, CN, CF₃, or F;
- C₁-C₅-alkoxy,
- wherein optionally one or more hydrogen atoms are independently substituted by deuterium, CN, CF₃, or F;
- C₁-C₅-thioalkoxy,
- wherein optionally one or more hydrogen atoms are independently substituted by deuterium, CN, CF₃, or F;
- C₂-C₅-alkenyl,
- wherein optionally one or more hydrogen atoms are independently substituted by deuterium, CN, CF₃, or F;
- C₂-C₅-alkynyl,
- wherein optionally one or more hydrogen atoms are independently substituted by deuterium, CN, CF₃, or F;
- C₆-C₁₈-aryl,
- wherein optionally one or more hydrogen atoms are independently substituted by deuterium, CN, CF₃, F, C₁-C₅-alkyl, SiMe₃, SiPh₃or C₆-C₁₈-aryl substituents;
- C₃-C₁₇-heteroaryl,
- wherein optionally one or more hydrogen atoms are independently substituted by deuterium, CN, CF₃, F, C₁-C₅-alkyl, SiMe₃, SiPh₃or C₆-C₁₈-aryl substituents;
- N(C₆-C₁₈-aryl)₂,
- N(C₃-C₁₇-heteroaryl)₂; and
- N(C₃-C₁₇-heteroaryl)(C₆-C₁₈-aryl);
- wherein in case, one of Y^aand Y^bis or both of Y^aand Y^bare NR^DABNA-3, C(R^DABNA-3)₂, Si(R^DABNA-3)₂, or BR^DABNA-3the one or the two substituents R^DABNA-3may optionally and independently of each other bond to one or both of the adjacent rings A′ and B′ (for Y^a=NR^DABNA-3, C(R^DABNA-3)₂, Si(R^DABNA-3)₂, or BR^DABNA-3) or A′ and C′ (for Y^b=NR^DABNA-3, C(R^DABNA-3)₂, Si(R^DABNA-3)₂, or BR^DABNA-3) via a direct (single) bond or via a connecting atom or atom group being in each case independently selected from NR^DABNA-1, O, S, C(R^DABNA-1)₂, Si(R^DABNA-1)₂, BR^DABNA-1ad Se;
- and wherein optionally, two or more, preferably two, structures of formula DABNA-I are conjugated with each other, preferably fused to each other by sharing at least one, more preferably exactly one, bond;
- wherein optionally two or more, preferably two, structures of formula DABNA-I are present in the emitter and share at least one, preferably exactly one, aromatic or heteroaromatic ring (i.e., this ring may be part of both structures of formula DABNA-I) which preferably is any of the rings A′, B′, and C′ of formula DABNA-I, but may also be any aromatic or heteroaromatic substituent selected from R^DABNA-1, R^DABNA-2, R^DABNA-3, R^DABNA-4, R^DABNA-5, and R^DABNA-6, in particular R^DABNA-3, or any aromatic or heteroaromatic ring formed by two or more adjacent substituents as stated above, wherein the shared ring may constitute the same or different moieties of the two or more structures of formula DABNA-I that share the ring (i.e., the shared ring may for example be ring C′ of both structures of formula DABNA-I optionally included in the emitter or the shared ring may for example be ring B′ of one and ring C′ of the other structure of formula DABNA-I optionally included in the emitter); and
- wherein optionally at least one of R^DABNA-1, R^DABNA-2, R^DABNA-3, R^DABNA-4, R^DABNA-5, and R^DABNA-6is replaced by a band to a further Chemical entity of formula DABNA-I and/or wherein optionally at least one hydrogen atom of any of R^DABNA-1, R^DABNA-2, R^DABNA-3, R^DABNA-4, R^DABNA-5, and R^DABNA-6is replaced by a bond to a further chemical entity of formula DABNA-I.

In one embodiment of the invention, in at least one, preferably each, light-emitting layer B, at least one of the one or more small FWHM emitters S^Bincludes a structure according to formula DABNA-I.

In one embodiment of the invention, in at least one, preferably each, light-emitting layer B, each small FWHM emitter S^Bincludes a structure according to formula DABNA-I.

In one embodiment of the invention, in at least one, preferably each, light-emitting layer B, at least one of the one or more small FWHM emitters S^Bconsists of a structure according to formula DABNA-I.

In one embodiment of the invention, in at least one, preferably each, light-emitting layer B, each small FWHM emitter S^Bconsists of a structure according to formula DABNA-I.

In a preferred embodiment of the invention, in which in at least one, preferably each, light-emitting layer B, at least one, preferably each, of the one or more small FWHM emitters S^Bincludes or consists of a structure according to formula DABNA-I, A′, B′, and C′ are all aromatic rings with 6 ring atoms each (i.e., they are all benzene rings).

In a preferred embodiment of the invention, in which in at least one, preferably each, light-emitting layer B, at least one, preferably each, of the one or more small FWHM emitters S^Bincludes or consists of a structure according to formula DABNA-I, Y^aand Y^bare independently of each other selected from NR^DABNA-3, O, and S.

In an even more preferred embodiment of the invention, in which in at least one, preferably each, light-emitting layer B, at least one, preferably each, of the one or more small FWHM emitters S^Bincludes or consists of a structure according to formula DABNA-I, Y^aand Y^bare independently of each other selected from NR^DABNA-3, and O.

In a particularly preferred embodiment of the invention, in which in at least one, preferably each, light-emitting layer B, at least one, preferably each, of the one or more small FWHM emitters S^Bincludes or consists of a structure according to formula DABNA-I, Y^aand Y^bare both NR^DABNA-3.

- R^DABNA-1, is at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, N(R^DABNA-2)₂, OR^DABNA-2, SR^DABNA-2; Si(R^DABNA-2)₃, CF₃, CN, F,
- C₁-C₅-alkyl,
- which is optionally substituted with one or more substituents R^DABNA-2;
- C₁-C₅-alkoxy,
- which is optionally substituted with one or more substituents R^DABNA-2;
- C₁-C₅-thioalkoxy,
- which is optionally substituted with one or more substituents R^DABNA-2;
- C₆-C₁₈-aryl,
- which is optionally substituted with one or more substituents R^DABNA-2;
- C₃-C₁₇-heteroaryl,
- which is optionally substituted with one or more substituents R^DABNA-2;
- R^DABNA-2is at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, N(R^DABNA-6)₂, OR^DABNA-6, SR^DABNA-6, Si(R^DABNA-6)₃, CF₃, CN, F,
- C₁-C₅-alkyl,
- which is optionally substituted with one or more substituents R^DABNA-6;
- C₆-C₁₈-aryl,
- which is optionally substituted with one or more substituents R^DABNA-6;
- C₃-C₁₇-heteroaryl,
- which is optionally substituted with one or more substituents R^DABNA-6;
- wherein two or more adjacent substituents selected from R^DABNA-1and R^DABNA-2optionally form a mono- or polycyclic, aliphatic or aromatic or heteroaromatic, carbocyclic or heterocyclic ring system which is fused to the adjacent ring A′, B′ or C′, wherein the optionally so formed fused ring system (i.e., the respective ring A′, B′ or C′ and the additional ring(s) that are optionally fused to it) includes in total 8 to 30 ring atoms.

- R^DABNA-1, is at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, N(R^DABNA-2)₂, OR^DABNA-2, SR^DABNA-2, Si(R^DABNA-2)₃,
- C₁-C₅-alkyl,
- which is optionally substituted with one or more substituents R^DABNA-2;
- C₆-C₁₈-aryl,
- which is optionally substituted with one or more substituents R^DABNA-2;
- C₃-C₁₇-heteroaryl,
- which is optionally substituted with one or more substituents R^DABNA-2;
- R^DABNA-2is at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, N(R^DABNA-6)₂, OR^DABNA-6, SR^DABNA-6, Si(R^DABNA-6)₃, CF₃, CN, F,
- C₁-C₅-alkyl,
- which is optionally substituted with one or more substituents R^DABNA-6;
- C₆-C₁₈-aryl,
- which is optionally substituted with one or more substituents R^DABNA-6;
- C₃-C₁₇-heteroaryl,
- which is optionally substituted with one or more substituents R^DABNA-6;
- wherein two or more adjacent substituents selected from R^DABNA-1and R^DABNA-2optionally form a mono- or polycyclic, aliphatic or aromatic or heteroaromatic, carbocyclic or heterocyclic ring system which is fused to the adjacent ring A′, B′ or C′, wherein the optionally so formed fused ring system (i.e., the respective ring A′, B′ or C′ and the additional ring(s) that are optionally fused to it) includes in total 8 to 30 ring atoms.

- R^DABNA-1, is at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, N(R^DABNA-2)₂, OR^DABNA-2, SR^DABNA-2
- C₁-C₅-alkyl,
- which is optionally substituted with one or more substituents R^DABNA-2;
- C₆-C₁₈-aryl,
- which is optionally substituted with one or more substituents R^DABNA-2;
- C₃-C₁₇-heteroaryl,
- which is optionally substituted with one or more substituents R^DABNA-2;
- R^DABNA-2is at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, N(Ph)₂, OPh, CN, Me, ⁱPr, ^tBu, Si(Me)₃,
- Ph,
- which is optionally substituted with one or more substituents R^DABNA-6;
- C₃-C₁₇-heteroaryl,
- which is optionally substituted with one or more substituents R^DABNA-6;
- wherein two or more adjacent R^DABNA-1form a mono- or polycyclic, aliphatic or aromatic or heteroaromatic, carbocyclic or heterocyclic ring system which is fused to the adjacent ring A′, B′ or C′, wherein the optionally so formed fused ring system (i.e., the respective ring A′, B′ or C′ and the additional ring(s) that are optionally fused to it) includes in total 8 to 30 ring atoms.

- R^DABNA-1, is at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, N(Ph)₂, OPh, Me, ⁱPr, ^tBu, Si(Me)₃,
- Ph,
- wherein one or more hydrogen atoms are optionally, independently from each other substituted by deuterium, Me, ⁱPr, ^tBu, Ph, or CN;
- C₃-C₁₇-heteroaryl,
- wherein one or more hydrogen atoms are optionally, independently from each other substituted by deuterium, Me, ⁱPr, ^tBu, Ph, or CN;
- wherein two or more adjacent substituents R^DABNA-1optionally form a mono- or polycyclic, aliphatic or aromatic or heteroaromatic, carbocyclic or heterocyclic ring system which is fused to the adjacent ring A′, B′ or C′, wherein the optionally so formed fused ring system (i.e., the respective ring A′, B′ or C′ and the additional ring(s) that are optionally fused to it) includes in total 8 to 30 ring atoms.

- R^DABNA-1, is at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, N(Ph)₂, Me, ⁱPr, ^tBu,
- Ph,
- wherein one or more hydrogen atoms are optionally, independently from each other substituted by deuterium, Me, ⁱPr, ^tBu, Ph or CN;
- carbazolyl,
- wherein one or more hydrogen atoms are optionally, independently from each other substituted by deuterium, Me, ⁱPr, ^tBu, Ph or CN;
- triazinyl,
- wherein one or more hydrogen atoms are optionally, independently from each other substituted by deuterium, Me, ⁱPr, ^tBu, or Ph;
- pyrimidinyl,
- wherein one or more hydrogen atoms are optionally, independently from each other substituted by deuterium, Me, ⁱPr, ^tBu, or Ph;
- pyridinyl,
- wherein one or more hydrogen atoms are optionally, independently from each other substituted by deuterium, Me, ⁱPr, ^tBu, or Ph;
- wherein two or more adjacent substituents R^DABNA-1optionally form a mono- or polycyclic, aliphatic or aromatic or heteroaromatic, carbocyclic or heterocyclic ring system which is fused to the adjacent ring A′, B′ or C′, wherein the optionally so formed fused ring system (i.e., the respective ring A′, B′ or C′ and the additional ring(s) that are optionally fused to it) includes in total 8 to 30 ring atoms.

In one embodiment of the invention, in which in at least one, preferably each, light-emitting layer B, at least one, preferably each, of the one or more small FWHM emitters S^Bincludes or consists of a structure according to formula DABNA-I, adjacent substituents selected from R^DABNA-1and R^DABNA-2do not form a mono- or polycyclic, aliphatic or aromatic or heteroaromatic, carbocyclic or heterocyclic ring system which is fused to the adjacent ring A′, B′ or C′.

- R^DABNA-3is at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium,
- C₁-C₄-alkyl,
- which is optionally substituted with one or more substituents R^DABNA-4;
- C₆-C₁₈-aryl,
- which is optionally substituted with one or more substituents R^DABNA-4;
- C₃-C₁₇-heteroaryl,
- which is optionally substituted with one or more substituents R^DABNA-4;
- R^DABNA-4is at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, N(R^DABNA-5)₂, OR^DABNA-5, SR^DABNA-5, Si(C₁-C₅-alkyl)₃, CF₃, CN, F,
- C₁-C₅-alkyl,
- which is optionally substituted with one or more substituents R^DABNA-5;
- C₆-C₁₈-aryl,
- which is optionally substituted with one or more substituents R^DABNA-5;
- C₃-C₁₇-heteroaryl,
- which is optionally substituted with one or more substituents R^DABNA-5;
- R^DABNA-5is at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, N(Ph)₂, OPh, Si(Me)₃, CF₃, CN, F,
- C₁-C₅-alkyl,
- wherein one or more hydrogen atoms are optionally, independently from each other substituted by deuterium;
- C₆-C₁₈-aryl,
- wherein one or more hydrogen atoms are optionally, independently from each other substituted by deuterium, Me, ⁱPr, ^tBu, Ph, or CN;
- C₃-C₁₇-heteroaryl,
- wherein one or more hydrogen atoms are optionally, independently from each other substituted by deuterium, Me, ⁱPr, ^tBu, Ph, or CN;
- wherein two or more adjacent substituents selected from R^DABNA-3, R^DABNA-4, and R^DABNA-5optionally form a mono- or polycyclic, aliphatic or aromatic or heteroaromatic, carbocyclic or heterocyclic ring system with each other, wherein the optionally so formed ring system includes in total 8 to 30 ring atoms.

- R^DABNA-3is at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium,
- C₁-C₄-alkyl,
- which is optionally substituted with one or more substituents R^DABNA-4;
- C₆-C₁₈-aryl,
- which is optionally substituted with one or more substituents R^DABNA-4;
- C₃-C₁₇-heteroaryl,
- which is optionally substituted with one or more substituents R^DABNA-4;
- R^DABNA-4is at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, N(Ph)₂, OPh, Si(Me)₃, CF₃, CN, F,
- C₁-C₅-alkyl,
- wherein one or more hydrogen atoms are optionally, independently from each other substituted by deuterium;
- C₆-C₁₈-aryl,
- wherein one or more hydrogen atoms are optionally, independently from each other substituted by deuterium, Me, ⁱPr, ^tBu, Ph, or CN;
- C₃-C₁₇-heteroaryl,
- wherein one or more hydrogen atoms are optionally, independently from each other substituted by deuterium, Me, ⁱPr, ^tBu, Ph, or CN;
- wherein two or more adjacent substituents selected from R^DABNA-3and R^DABNA-4do not form a mono- or polycyclic, aliphatic or aromatic or heteroaromatic, carbocyclic or heterocyclic ring system with each other.

- R^DABNA-3is at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium,
- C1-C4-alkyl,
- which is optionally substituted with one or more substituents R^DABNA-4;
- C₆-C₁₈-aryl,
- which is optionally substituted with one or more substituents R^DABNA-4;
- C₃-C₁₇-heteroaryl,
- which is optionally substituted with one or more substituents R^DABNA-4;
- R^DABNA-4is at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, CN, F,
- C₁-C₅-alkyl,
- wherein one or more hydrogen atoms are optionally, independently from each other substituted by deuterium;
- C₆-C₁₈-aryl,
- wherein one or more hydrogen atoms are optionally, independently from each other substituted by deuterium, Me, ⁱPr, ^tBu, Ph, or CN;
- C₃-C₁₇-heteroaryl,
- wherein one or more hydrogen atoms are optionally, independently from each other substituted by deuterium, Me, ⁱPr, ^tBu, Ph, or CN;
- wherein two or more adjacent substituents selected from R^DABNA-3and R^DABNA-4do not form a mono- or polycyclic, aliphatic or aromatic or heteroaromatic, carbocyclic or heterocyclic ring system with each other.

- R^DABNA-3is at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, Me, ⁱPr, ^tBu,
- C₆-C₁₈-aryl,
- wherein one or more hydrogen atoms are optionally, independently from each other substituted by deuterium, Me, ⁱPr, ^tBu, Ph, or CN;
- wherein two or more adjacent substituents selected from R^DABNA-3do not form a mono- or polycyclic, aliphatic or aromatic or heteroaromatic, carbocyclic or heterocyclic ring system with each other.

- R^DABNA-3is at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, Me, ⁱPr, ^tBu, and
- Ph,
- wherein one or more hydrogen atoms are optionally, independently from each other substituted by deuterium, Me, ⁱPr, ^tBu, Ph, or CN;
- wherein two or more adjacent substituents selected from R^DABNA-3do not form a mono- or polycyclic, aliphatic or aromatic or heteroaromatic, carbocyclic or heterocyclic ring system with each other.

- R^DABNA-6is at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, OPh (Ph=phenyl), SPh, CF₃, CN, F, Si(C₁-C₅-alkyl)₃, Si(Ph)₃,
- C₁-C₅-alkyl,
- wherein optionally one or more hydrogen atoms are independently substituted by deuterium, Ph, CN, CF₃, or F;
- C₆-C₁₈-aryl,
- wherein optionally one or more hydrogen atoms are independently substituted by deuterium, CN, CF₃, F, C₁-C₅-alkyl, SiMe₃, SiPh₃or C₆-C₁₈-aryl substituents;
- C₃-C₁₇-heteroaryl,
- wherein optionally one or more hydrogen atoms are independently substituted by deuterium, CN, CF₃, F, C₁-C₅-alkyl, SiMe₃, SiPh₃or C₆-C₁₈-aryl substituents;
- N(C₆-C₁₈-aryl)₂,
- N(C₃-C₁₇-heteroaryl)₂; and
- N(C₃-C₁₇-heteroaryl)(C₆-C₁₈-aryl).

- R^DABNA-6is at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, N(Ph)₂, OPh (Ph=phenyl), SPh, CF₃, CN, F, Si(Me)₃, Si(Ph)₃,
- C₁-C₅-alkyl,
- wherein optionally one or more hydrogen atoms are independently substituted by deuterium, Ph, CN, CF₃, or F;
- C₆-C₁₈-aryl,
- wherein optionally one or more hydrogen atoms are independently substituted by deuterium, CN, CF₃, F, Me, ⁱPr, ^tBu, SiMe₃, SiPh_aor Ph;
- C₃-C₁₇-heteroaryl,
- wherein optionally one or more hydrogen atoms are independently substituted by deuterium, CN, CF₃, F, Me, ⁱPr, ^tBu, SiMe₃, SiPh_aor Ph.

- R^DABNA-6is at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, N(Ph)₂, CN, F, Me, ⁱPr, ^tBu,
- Ph,
- wherein optionally one or more hydrogen atoms are independently substituted by deuterium, CN, Me, ⁱPr, ^tBu, or Ph;
- C₃-C₁₇-heteroaryl,
- wherein optionally one or more hydrogen atoms are independently substituted by deuterium, CN, Me, ⁱPr, ^tBu, or Ph.

- R^DABNA-6is at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, Me, ⁱPr, ^tBu,
- Ph,
- wherein optionally one or more hydrogen atoms are independently substituted by deuterium, Me, ⁱPr, ^tBu, or Ph.

In one embodiment of the invention, in which in at least one, preferably each, light-emitting layer B, at least one, preferably each, of the one or more small FWHM emitters S^Bincludes or consists of a structure according to formula DABNA-I, when Y^aand/or Y^bis/are NR^DABNA-3, C(R^DABNA-3)₂, Si(R^DABNA-3)₂, or BR^DABNA-3, the one or the two substituents R^DABNA-3do not bond to one or both of the adjacent rings A′ and B′ (for Y^a=NR^DABNA-3, C(R^DABNA-3)₂, Si(R^DABNA-3)₂, or BR^DABNA-3) or A′ and C′ (for Y^b=NR^DABNA-3, C(R^DABNA-3)₂, Si(R^DABNA-3)₂, or BR^DABNA-3).

In one embodiment, small FWHM emitters S^Bin the context of the present invention may optionally also be multimers (e.g., dimers) of the aforementioned formula DABNA-I, which means that their structure includes more than one subunits, each of which has a structure according to formula DABNA-I. In this case, the skilled artisan will understand that the two or more subunits according to formula DABNA-I may for example be conjugated, preferably fused to each other (i.e., sharing at least one bond, wherein the respective substituents attached to the atoms forming that bond may no longer be present). The two or more subunits may also share at least one, preferably exactly one, aromatic or heteroaromatic ring. This means that, for example, a small FWHM emitter S^Bmay include two or more subunits each having a structure of formula DABNA-I, wherein these two subunits share one aromatic or heteroaromatic ring (i.e., the respective ring is part of both subunits). As a result, the respective multimeric (e.g., dimeric) emitter S^Bmay not contain two whole subunits according to formula DABNA-I as the shared ring is only present once. Nevertheless, the skilled artisan will understand that herein, such an emitter is still considered a multimer (for example a dimer if two subunits having a structure of formula DABNA-I are included) of formula DABNA-I. The same holds true for multimers sharing more than one ring. It is preferred that the multimers are dimers including two subunits, each having a structure of formula DABNA-I.

In one embodiment of the invention, in at least one, preferably each, light-emitting layer B, at least one, preferably each small FWHM emitter S^B, is a dimer of formula DABNA-I as described above, which means that the emitter includes two subunits, each having a structure according to formula DABNA-I.

In one embodiment of the invention, in at least one, preferably each, light-emitting layer B, at least one, preferably each, of the one or more small FWHM emitters S^Bincludes or consists of two or more, preferably of exactly two, structures according to formula DABNA-I (i.e., subunits),

- wherein these subunits share at least one, preferably exactly one, aromatic or heteroaromatic ring (i.e., this ring may be part of both structures of formula DABNA-I) and wherein the shared ring(s) may be any of the rings A′, B′, and C′ of formula DABNA-I, but may also be any aromatic or heteroaromatic substituent selected from R^DABNA-1, R^DABNA-2, R^DABNA-3, R^DABNA-4, R^DABNA-5, and R^DABNA-6, in particular R^DABNA-3, or any aromatic or heteroaromatic ring formed by two or more adjacent substituents as stated above, wherein the shared ring may constitute the same or different moieties of the two or more structures of formula DABNA-I that share the ring (i.e., the shared ring may for example be ring C′ of both structures of formula DABNA-I optionally included in the emitter or the shared ring may for example be ring B′ of one and ring C′ of the other structure of formula DABNA-I optionally included in the emitter).

- wherein at least one of R^DABNA-1, R^DABNA-2, R^DABNA-3, R^DABNA-4, R^DABNA-5, and R^DABNA-6is replaced by a bond to a further chemical entity of formula DABNA-I and/or wherein at least one hydrogen atom of any of R^DABNA-1, R^DABNA-2, R^DABNA-3, R^DABNA-4, R^DABNA-5, and R^DABNA-6is replaced by a band to a further chemical entity of formula DABNA-I.

Non-limiting examples of emitters including or consisting of a structure according to formula DABNA-I that may be used as small FWHM emitters S^Baccording to the present invention are listed below.

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A group of emitters that may be used as small FWHM emitters S^Bin the context of the present invention are emitters including or consisting of a structure according to the following formula BNE-1 or a multimer thereof:

- wherein,
- c and d are both integers and independently of each other selected from 0 and 1;
- e and f are both integers and selected from 0 and 1, wherein e and f are (always) identical (i.e., both 0 or both 1);
- g and h are both integers and selected from 0 and 1, wherein g and h are (always) identical (i.e., both 0 or both 1);
- if d is 0, e and f are both 1, and if d is 1, e and f are both 0;
- if c is 0, g and h are both 1, and if c is 1, g and h are both 0;
- V¹is selected from nitrogen (N) and CR^BNE-V;
- V²is selected from nitrogen (N) and CR^BNE-I;
- X³is selected from the group consisting of a direct bond, CR^BNE-3R^BNE-4,
- C═CR^BNE-3′R^BNE-4′, C═O, C═NR^BNE-3, NR^BNE-3, O, SiR^BNE-3R^BNE-4, S, S(O) and S(O)₂;
- Y²is selected from the group consisting of a direct bond, CR^BNE-3′R^BNE-4′,
- C═CR^BNE-3′R^BNE-4′, C═O, C═NR^BNE-3′, NR^BNE-3′, O, SiR^BNE-3′R^BNE-4′, S, S(O) and S(O)₂;
- R^BNE-1, R^BNE-2, R^BNE-1′, R^BNE-2′, R^BNE-3, R^BNE-4, R^BNE-3′, R^BNE-4′, R^BNE-I, R^BNE-II, R^BNE-III, R^BNE-IV, and R^BNE-Vare each independently of each other selected from the group consisting of: hydrogen, deuterium, N(R^BNE-5)₂, OR^BNE-5, Si(R^BNE-5)₃, B(OR^BNE-5)₂, B(R^BNE-5)₂, OSO₂R^BNE-5, CF₃, CN, F, Cl, Br, I,
- C₁-C₄₀-alkyl,
- which is optionally substituted with one or more substituents R^BNE-5and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^BNE-5C═CR^BNE-5, C≡C, Si(R^BNE-5)₂, Ge(R^BNE-5)₂, Sn(R^BNE-5)₂, C═O, C═S, C═Se, C═NR^BNE-5, P(═O)(R^BNE-5), SO, SO₂, NR^BNE-5, O, S or CONR^BNE-5;
- C₁-C₄₀-alkoxy,
- which is optionally substituted with one or more substituents R^BNE-5and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^BNE-5C═CR^BNE-5, C≡C, Si(R^BNE-5)₂, Ge(R^BNE-5)₂, Sn(R^BNE-5)₂, C═O, C═S, C═Se, C═NR^BNE-5, P(═O)(R^BNE-5), SO, SO₂, NR^BNE-5, O, S or CONR^BNE-5;
- C₁-C₄₀-thioalkoxy,
- which is optionally substituted with one or more substituents R^BNE-5and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^BNE-5C═CR^BNE-5, C≡C, Si(R^BNE-5)₂, Ge(R^BNE-5)₂, Sn(R^BNE-5)₂, C═O, C═S, C═Se, C═NR^BNE-5, P(═O)(R^BNE-5), SO, SO₂, NR^BNE-5, O, S or CONR^BNE-5;
- C₂-C₄₀-alkenyl,
- which is optionally substituted with one or more substituents R^BNE-5and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^BNE-5C═CR^BNE-5, C≡C, Si(R^BNE-5)₂, Ge(R^BNE-5)₂, Sn(R^BNE-5)₂, C═O, C═S, C═Se, C═NR^BNE-5, P(═O)(R^BNE-5), SO, SO₂, NR^BNE-5, O, S or CONR^BNE-5;
- C₂-C₄₀-alkynyl,
- which is optionally substituted with one or more substituents R^BNE-5and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^BNE-5C═CR^BNE-5, C≡C, Si(R^BNE-5)₂, Ge(R^BNE-5)₂, Sn(R^BNE-5)₂, C═O, C═S, C═Se, C═NR^BNE-5, P(═O)(R^BNE-5), SO, SO₂, NR^BNE-5, O, S or CONR^BNE-5;
- C₆-C₆₀-aryl,
- which is optionally substituted with one or more substituents R^BNE-5; and
- C₂-C₅₇-heteroaryl,
- which is optionally substituted with one or more substituents R^BNE-5;
- R^BNE-d, R^BNE-d′, and R^BNE-eare independently of each other selected from the group consisting of: hydrogen, deuterium, N(R^BNE-5)₂, OR^BNE-5, Si(R^BNE-5)₃, B(OR^BNE-5)₂, B(R^BNE-5)₂, OSO₂R^BNE-5, CF₃, CN, F, Cl, Br, I,
- C₁-C₄₀-alkyl,
- which is optionally substituted with one or more substituents R^BNE-aand
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^BNE-5C═CR^BNE-5, C≡C, Si(R^BNE-5)₂, Ge(R^BNE-5)₂, Sn(R^BNE-5)₂, C═O, C═S, C═Se, C═NR^BNE-5, P(═O)(R^BNE-5), SO, SO₂, NR^BNE-5, O, S or CONR^BNE-5;
- C₁-C₄₀-alkoxy,
- which is optionally substituted with one or more substituents R^BNE-aand
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^BNE-5C═CR^BNE-5, C≡C, Si(R^BNE-5)₂, Ge(R^BNE-5)₂, Sn(R^BNE-5)₂, C═O, C═S, C═Se, C═NR^BNE-5, P(═O)(R^BNE-5), SO, SO₂, NR^BNE-5, O, S or CONR^BNE-5;
- C₁-C₄₀-thioalkoxy,
- which is optionally substituted with one or more substituents R^BNE-aand
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^BNE-5C═CR^BNE-5, C≡C, Si(R^BNE-5)₂, Ge(R^BNE-5)₂, Sn(R^BNE-5)₂, C═O, C═S, C═Se, C═NR^BNE-5, P(═O)(R^BNE-5), SO, SO₂, NR^BNE-5, O, S or CONR^BNE-5;
- C₂-C₄₀-alkenyl,
- which is optionally substituted with one or more substituents R^BNE-aand
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^BNE-5C═CR^BNE-5, C≡C, Si(R^BNE-5)₂, Ge(R^BNE-5)₂, Sn(R^BNE-5)₂, C═O, C═S, C═Se, C═NR^BNE-5, P(═O)(R^BNE-5), SO, SO₂, NR^BNE-5, O, S or CONR^BNE-5;
- C₂-C₄₀-alkynyl,
- which is optionally substituted with one or more substituents R^BNE-aand
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^BNE-C═CR^BNE-5, C≡C, Si(R^BNE-5)₂, Ge(R^BNE-5)₂, Sn(R^BNE-5)₂, C═O, C═S, C═Se, C═NR^BNE-5, P(═O)(R^BNE-5), SO, SO₂, NR^BNE-5, O, S or CONR^BNE-5;
- C₆-C₆₀-aryl,
- which is optionally substituted with one or more substituents R^BNE-a; and
- C₂-C₅₇-heteroaryl,
- which is optionally substituted with one or more substituents R^BNE-a;
- R^BNE-ais at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, N(R^BNE-5)₂, OR^BNE-5, Si(R^BNE-5)₃, B(OR^BNE-5)₂, B(R^BNE-5)₂, OSO₂R^BNE-5, CF₃, CN, F, Cl, Br, I,
- C₁-C₄₀-alkyl,
- which is optionally substituted with one or more substituents R^BNE-5and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^BNE-5C═CR^BNE-5, C≡C, Si(R^BNE-5)₂, Ge(R^BNE-5)₂, Sn(R^BNE-5)₂, C═O, C═S, C═Se, C═NR^BNE-5, P(═O)(R^BNE-5), SO, SO₂, NR^BNE-5, O, S or CONR^BNE-5;
- C₁-C₄₀-alkoxy,
- which is optionally substituted with one or more substituents R^BNE-5and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^BNE-5C═CR^BNE-5, C≡C, Si(R^BNE-5)₂, Ge(R^BNE-5)₂, Sn(R^BNE-5)₂, C═O, C═S, C═Se, C═NR^BNE-5, P(═O)(R^BNE-5), SO, SO₂, NR^BNE-5, O, S or CONR^BNE-5;
- C₁-C₄₀-thioalkoxy,
- which is optionally substituted with one or more substituents R^BNE-5and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^BNE-5C═CR^BNE-5, C≡C, Si(R^BNE-5)₂, Ge(R^BNE-5)₂, Sn(R^BNE-5)₂, C═O, C═S, C═Se, C═NR^BNE-5, P(═O)(R^BNE-5), SO, SO₂, NR^BNE-5, O, S or CONR^BNE-5;
- C₂-C₄₀-alkenyl,
- which is optionally substituted with one or more substituents R^BNE-5and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^BNE-5C═CR^BNE-5, C≡C, Si(R^BNE-5)₂, Ge(R^BNE-5)₂, Sn(R^BNE-5)₂, C═O, C═S, C═Se, C═NR^BNE-5, P(═O)(R^BNE-5), SO, SO₂, NR^BNE-5, O, S or CONR^BNE-5;
- C₂-C₄₀-alkynyl,
- which is optionally substituted with one or more substituents R^BNE-5and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^BNE-C═CR^BNE-5, C≡C, Si(R^BNE-5)₂, Ge(R^BNE-5)₂, Sn(R^BNE-5)₂, C═O, C═S, C═Se, C═NR^BNE-5, P(═O)(R^BNE-5), SO, SO₂, NR^BNE-5, O, S or CONR^BNE-5;
- C₆-C₆₀-aryl,
- which is optionally substituted with one or more substituents R^BNE-5; and
- C₂-C₅₇-heteroaryl,
- which is optionally substituted with one or more substituents R^BNE-5;
- R^BNE-5is at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, N(R^BNE-6)₂, OR^BNE-6, Si(R^BNE-6)₃, B(OR^BNE-6)₂, B(R^BNE-6)₂, OSO₂R^BNE-6, CF₃, CN, F, Cl, Br, I,
- C₁-C₄₀-alkyl,
- which is optionally substituted with one or more substituents R^BNE-6and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^BNE-6C═CR^BNE-6, C≡C, Si(R^BNE-6)₂, Ge(R^BNE-6)₂, Sn(R^BNE-6)₂, C═O, C═S, C═Se, C═NR^BNE-6, P(═O)(R^BNE-6), SO, SO₂, NR^BNE-6, O, S or CONR^BNE-6;
- C₁-C₄₀-alkoxy,
- which is optionally substituted with one or more substituents R^BNE-6and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^BNE-6C═CR^BNE-6, C≡C, Si(R^BNE-6)₂, Ge(R^BNE-6)₂, Sn(R^BNE-6)₂, C═O, C═S, C═Se, C═NR^BNE-6, P(═O)(R^BNE-6), SO, SO₂, NR^BNE-6, O, S or CONR^BNE-6;
- C₁-C₄₀-thioalkoxy,
- which is optionally substituted with one or more substituents R^BNE-6and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^BNE-6C═CR^BNE-6, C≡C, Si(R^BNE-6)₂, Ge(R^BNE-6)₂, Sn(R^BNE-6)₂, C═O, C═S, C═Se, C═NR^BNE-6, P(═O)(R^BNE-6), SO, SO₂, NR^BNE-6, O, S or CONR^BNE-6;
- C₂-C₄₀-alkenyl,
- which is optionally substituted with one or more substituents R^BNE-6and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^BNE-6C═CR^BNE-6, C≡C, Si(R^BNE-6)₂, Ge(R^BNE-6)₂, Sn(R^BNE-6)₂, C═O, C═S, C═Se, C═NR^BNE-6, P(═O)(R^BNE-6), SO, SO₂, NR^BNE-6, O, S or CONR^BNE-6;
- C₂-C₄₀-alkynyl,
- which is optionally substituted with one or more substituents R^BNE-6and
- wherein one or more non-adjacent CH₂-groups are optionally substituted by R^BNE-6C═CR^BNE-6, C≡C, Si(R^BNE-6)₂, Ge(R^BNE-6)₂, Sn(R^BNE-6)₂, C═O, C═S, C═Se, C═NR^BNE-6, P(═O)(R^BNE-6), SO, SO₂, NR^BNE-6, O, S or CONR^BNE-6;
- C₆-C₆₀-aryl,
- which is optionally substituted with one or more substituents RBE-8; and
- C₂-C₅₇-heteroaryl,
- which is optionally substituted with one or more substituents R^BNE-6;
- R^BNE-6is at each occurrence independently from another selected from the group consisting of: hydrogen, deuterium, OPh, CF₃, CN, F,
- C₁-C₅-alkyl,
- wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, CN, CF₃, Ph or F;
- C₁-C₅-alkoxy,
- wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, CN, CF₃, or F;
- C₁-C₅-thioalkoxy,
- wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, CN, CF₃, or F;
- C₂-C₅-alkenyl,
- wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, CN, CF₃, or F;
- C₂-C₅-alkynyl,
- wherein one or more hydrogen atoms are optionally, independently of each other substituted by deuterium, CN, CF₃, or F;
- C₆-C₁₈-aryl,
- which is optionally substituted with one or more C₁-C₅-alkyl substituents;
- C₂-C₁₇-heteroaryl,
- which is optionally substituted with one or more C₁-C₅-alkyl substituents;
- N(C₆-C₁₈-aryl)₂;
- N(C₂-C₁₇-heteroaryl)₂, and
- N(C₂-C₁₇-heteroaryl)(C₆-C₁₈-aryl);
- wherein R^BNE-IIIand R^BNE-eoptionally combine to form a direct single bond; and
- wherein two or more of substituents R^BNE-a, R^BNE-d, R^BNE-d′, R^BNE-e, R^BNE-3′, R^BNE-4′, R^BNE-5optionally form a mono- or polycyclic, aliphatic or aromatic, carbo- or heterocyclic and/or benzo-fused ring system with each other;
- wherein two or more of the substituents R^BNE-1, R^BNE-2, R^BNE-1′, R^BNE-2′, R^BNE-3, R^BNE-4, R^BNE-5, R^BNE-I, R^BNE-II, R^BNE-III, R^BNE-IV, R^BNE-Voptionally form a mono- or polycyclic, aliphatic or aromatic, carbo- or heterocyclic and/or benzo-fused ring system with each other;
- wherein optionally two or more, preferably two, structures of formula BNE-1 are conjugated with each other, preferably fused to each other by sharing at least one, more preferably exactly one, bond;
- wherein optionally two or more, preferably two, structures of formula BNE-1 are present in the emitter and share at least one, preferably exactly one, aromatic or heteroaromatic ring (i.e., this ring may be part of both structures of formula BNE-1) which preferably is any of the rings a, b, and c′ of formula BNE-1, but may also be any aromatic or heteroaromatic substituent selected from R^BNE-1, R^BNE-2, R^BNE-1′, R^BNE-2′, R^BNE-3, R^BNE-4, R^BNE-3′, R^BNE-4′, R^BNE-5, R^BNE-6, R^BNE-I, R^BNE-II, R^BNE-III, R^BNE-IV, R^BNE-V, R^BNE-a, R^BNE-e, R^BNE-d, and R^BNE-d′, or any aromatic or heteroaromatic ring formed by two or more substituents as stated above, wherein the shared ring may constitute the same or different moieties of the two or more structures of formula BNE-1 that share the ring (i.e., the shared ring may for example be ring c′ of both structures of formula BNE-1 optionally included in the emitter or the shared ring may for example be ring b of one and ring c′ of the other structure of formula BNE-1 optionally included in the emitter); and
- wherein optionally at least one of R^BNE-1, R^BNE-2, R^BNE-1′, R^BNE-2′, R^BNE-3, R^BNE-4, R^BNE-5, R^BNE-3′, R^BNE-4′, R^BNE-6, R^BNE-I, R^BNE-II, R^BNE-III, R^BNE-IV, R^BNE-V, R^BNE-a, R^BNE-e, R^BNE-d, or R^BNE-d′ is replaced by a bond to a further chemical entity of formula BNE-1 and/or wherein optionally at least one hydrogen atom of any of R^BNE-1, R^BNE-2, R^BNE-1′, R^BNE-2′, R^BNE-3, R^BNE-4, R^BNE-5, R^BNE-3′, R^BNE-4′, R^BNE-6, R^BNE-I, R^BNE-II, R^BNE-III, R^BNE-IV, R^BNE-V, R^BNE-a, R^BNE-e, R^BNE-d, or R^BNE-d′ is replaced by a bond to a further chemical entity of formula BNE-1.

In one embodiment of the invention, at least one of the one or more small FWHM emitters S^Bincludes a structure according to formula BNE-1.

In one embodiment of the invention, each small FWHM emitter S^Bincludes a structure according to formula BNE-1.

In one embodiment of the invention, at least one of the one or more small FWHM emitters S^Bconsists of a structure according to formula BNE-1.

In one embodiment of the invention, each small FWHM emitter S^Bconsists of a structure according to formula BNE-1.

In one embodiment of the invention, in which at least one, preferably each, of the one or more small FWHM emitters S^Bincludes or consists of a structure according to formula BNE-1, V¹is CR^BNE-Vand V²is CR^BNE-I.

In a preferred embodiment of the invention, in which at least one, preferably each, of the one or more small FWHM emitters S^Bincludes or consists of a structure according to formula BNE-1, c and d are both 1.