Patent Application
20230371364
The present invention relates to organic electroluminescent devices including a light-emitting layer B, which includes a TADF material EB, a small full width at half maximum (FWHM) emitter SB emitting blue light with a full width at half maximum (FWHM) of less than or equal to 0.25 eV, and a host material HB. Additionally, the organic electroluminescent devices according to the invention include an exciton management layer, which is adjacent to the light-emitting layer B, including a triplet-triplet-annihilation material. Furthermore, the present invention relates to a method for generating an organic electroluminescent device and to a method for generating blue light by means of an organic electroluminescent device according to the present invention.
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 by 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 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 including a light-emitting layer including a TADF material EB, a small full width at half maximum (FWHM) emitter SB emitting blue light with a full width at half maximum (FWHM) of less than or equal to 0.25 eV, and a host material HB, and an exciton management layer EXL, which is adjacent to the light-emitting layer, provides an organic electroluminescent device having a long lifetime, a high quantum yield and exhibiting narrow emission, ideally suitable to achieve the blue BT-2020 and DCPI3 color gamut.
Herein, TADF material EB may transfer excitation energy to the small full width at half maximum (FWHM) emitter SB which emits light.
The present invention relates to an organic electroluminescent device including a light-emitting layer B including:
Fulfilling the aforementioned requirements may result in an organic electroluminescent device having a long lifetime, a high quantum yield and exhibiting narrow emission, ideally suitable to achieve the blue BT-2020 and DCPI3 color gamut.
It is to be noted that throughout this text, reference will be made to relations between energies of excited states, orbitals, emission maxima and the like of components within the light-emitting layer B of the organic electroluminescent device according to the present invention. It is understood that a relation including energies of two specific components will only apply to light-emitting layer B that include both of these specific components. Additionally, the fact that a relation applies to the devices according to the present invention does not mean that all devices of the invention have to include all components that are referred to in said relation. This general note is applicable to all embodiments of the present invention.
Device Architecture
The person skilled in the art will notice that the light-emitting layer B will typically be incorporated in an organic electroluminescent device of the present invention. Preferably, such an organic electroluminescent device includes at least the following layers: at least one light-emitting layer B, at least one anode layer A and at least one cathode layer C.
Preferably, the light-emitting layer B is located between an anode layer A and a cathode layer C. Accordingly, the general set-up is preferably A-B-C. This does of course not exclude the presence of one or more optional further layers. These can be present at each side of A, of B and/or of C.
Preferably, an anode layer A is located on the surface of a substrate. The substrate may be formed by any material or composition of materials. Most frequently, glass slides are used as substrates. Alternatively, thin metal layers (e.g., copper, gold, silver or aluminum films) or plastic films or slides may be used. This may allow a higher degree of flexibility. At least one of both electrodes should be (essentially) transparent in order to allow light emission from the electroluminescent device (e.g., OLED). Usually, an anode layer A is mostly composed of materials allowing to obtain an (essentially) transparent film. Preferably, the anode layer A includes a large content or even consists of transparent conductive oxides (TCOs).
Such an anode layer A may exemplarily include indium tin oxide, aluminum zinc oxide, fluorine tin oxide, indium zinc oxide, PbO, SnO, zirconium oxide, molybdenum oxide, vanadium oxide, wolfram oxide, graphite, doped Si, doped Ge, doped GaAs, doped polyaniline, doped polypyrrole and/or doped polythiophene and mixtures of two or more thereof.
Particularly preferably, an anode layer A (essentially) consists of indium tin oxide (ITO) (e.g., (InO3)0.9(SnO2)0.1). The roughness of an anode layer A caused by the transparent conductive oxides (TCOs) may be compensated by using a hole injection layer (HIL). Further, a HIL may facilitate the injection of quasi charge carriers (i.e., holes) in that the transport of the quasi charge carriers from the TCO to a hole transport layer (HTL) is facilitated. A hole injection layer (HIL) may include poly-3,4-ethylenedioxy thiophene (PEDOT), polystyrene sulfonate (PSS), MoO2, V2O5, CuPC or CuI, in particular a mixture of PEDOT and PSS. A hole injection layer (HIL) may also prevent the diffusion of metals from an anode layer A into a hole transport layer (HTL). A HIL may exemplarily include PEDOT:PSS (poly-3,4-ethylenedioxy thiophene:polystyrene sulfonate), PEDOT (poly-3,4-ethylenedioxy thiophene), mMTDATA (4,4′,4″-tris[phenyl(m-tolyl)amino]triphenylamine), Spiro-TAD (2,2′,7,7′-tetrakis(n,n-diphenylamino)-9,9′-spirobifluorene), DNTPD (N1,N1′-(biphenyl-4,4′-diyl)bis(N1-phenyl-N4,N4-di-m-tolylbenzene-1,4-diamine), NPB (N,N′-nis-(1-naphthalenyl)-N,N′-bis-phenyl-(1,1′-biphenyl)-4,4′-diamine), NPNPB (N,N′-diphenyl-N,N′-di-[4-(N,N-diphenyl-amino)phenyl]benzidine), MeO-TPD (N,N,N′,N′-tetrakis(4-methoxyphenyl)-benzidine), HAT-CN (1,4,5,8,9,11-hexaazatriphenylen-hexacarbonitrile) and/or Spiro-NPD (N,N′-diphenyl-N,N′-bis-(1-naphthyl)-9,9′-spirobifluorene-2,7-diamine).
Adjacent to an anode layer A or a hole injection layer (HIL), typically a hole transport layer (HTL) is located. Herein, any hole transport compound may be used. Exemplarily, electron-rich heteroaromatic compounds such as triarylamines and/or carbazoles may be used as hole transport compound. A HTL may decrease the energy barrier between an anode layer A and a light-emitting layer B (serving as emitting layer (EML)). A hole transport layer (HTL) may also be an electron blocking layer (EBL). Preferably, hole transport compounds bear comparably high energy levels of their triplet states T1. Exemplarily a hole transport layer (HTL) may include a star-shaped heterocycle such as tris(4-carbazoyl-9-ylphenyl)amine (TCTA), poly-TPD (poly(4-butylphenyl-diphenyl-amine)), [alpha]-NPD (poly(4-butylphenyl-diphenyl-amine)), TAPC (4,4′-cyclohexyliden-bis[N,N-bis(4-methylphenyl)benzenamine]), 2-TNATA (4,4′,4″-tris[2-naphthyl(phenyl)-amino]triphenylamine), Spiro-TAD, DNTPD, NPB, NPNPB, MeO-TPD, HAT-CN and/or TrisPcz (9,9′-diphenyl-6-(9-phenyl-9H-carbazol-3-yl)-9H,9′H-3,3′-bicarbazole). In addition, a HTL may include a p-doped layer, which may be composed of an inorganic or organic dopant in an organic hole-transporting matrix. Transition metal oxides such as vanadium oxide, molybdenum oxide or tungsten oxide may exemplarily be used as inorganic dopant. Tetrafluorotetracyanoquinodimethane (F4-TCNQ), copper-pentafluorobenzoate (Cu(I)pFBz) or transition metal complexes may exemplarily be used as organic dopant.
An electron blocking layer (EBL) may exemplarily include mCP (1,3-bis(carbazol-9-yl)benzene), TCTA, 2-TNATA, mCBP (3,3-di(9H-carbazol-9-yl)biphenyl), 9-[3-(dibenzofuran-2-yl)phenyl]-9H-carbazole, 9-[3-(dibenzothiophen-2-yl)phenyl]-9H-carbazole, 9-[3,5-bis(2-dibenzofuranyl)phenyl]-9H-carbazole, 9-[3,5-bis(2-dibenzothiophenyl)phenyl]-9H-carbazole, tris-Pcz, CzSi (9-(4-tert-butylphenyl)-3,6-bis(triphenylsilyl)-9H-carbazole), and/or DCB (N,N′-dicarbazolyl-1,4-dimethylbenzene).
The composition of the one or more light-emitting layers B has been described above. Any of the one or more light-emitting layers B according to the invention preferably bears a thickness of not more than 1 mm, more preferably of not more than 0.1 mm, even more preferably of not more than 10 μm, even more preferably of not more than 1 μm, and particularly preferably of not more than 0.1 μm.
In an electron transport layer (ETL), any electron transporter may be used. Exemplarily, compounds poor of electrons such as, e.g., benzimidazoles, pyridines, triazoles, oxadiazoles (e.g., 1,3,4-oxadiazole), phosphine oxides and sulfone, may be used. Exemplarily, an electron transporter ETM (i.e. an electron transport material) may also be a star-shaped heterocycle such as 1,3,5-tri(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl (TPBi). An ETM may exemplarily be NBphen (2,9-bis(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline), Alq3 (Aluminum-tris(8-hydroxyquinoline)), TSPO1 (diphenyl-4-triphenylsilylphenyl-phosphinoxide), BPyTP2 (2,7-di(2,2′-bipyridin-5-yl)triphenyle), Sif87 (dibenzo[b,d]thiophen-2-yltriphenylsilane), Sif88 (dibenzo[b,d]thiophen-2-yl)diphenylsilane), BmPyPhB (1,3-bis[3,5-di(pyridin-3-yl)phenyl]benzene) and/or BTB (4,4′-bis-[2-(4,6-diphenyl-1,3,5-triazinyl)]-1,1′-biphenyl). Optionally, the electron transport layer may be doped with materials such as Liq (8-hydroxyquinolinolatolithium). Optionally, a second electron transport layer may be located between electron transport layer and cathode layer C. An electron transport layer (ETL) may also block holes or a hole-blocking layer (HBL) is introduced.
An HBL may, for example, include HBM1:
BCP (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline=Bathocuproine), BAIq (bis(8-hydroxy-2-methylquinoline)-(4-phenylphenoxy)aluminum), NBphen (2,9-bis(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline), Alq3 (Aluminum-tris(8-hydroxyquinoline)), TSPO1 (diphenyl-4-triphenylsilylphenyl-phosphinoxide), T2T (2,4,6-tris(biphenyl-3-yl)-1,3,5-triazine), T3T (2,4,6-tris(triphenyl-3-yl)-1,3,5-triazine), TST (2,4,6-tris(9,9′-spirobifluorene-2-yl)-1,3,5-triazine), DTST (2,4-diphenyl-6-(3′-triphenylsilylphenyl)-1,3,5-triazine), DTDBF (2,8-bis(4,6-diphenyl-1,3,5-triazinyl)dibenzofurane) and/or TCB/TCP (1,3,5-tris(N-carbazolyl)benzol/1,3,5-tris(carbazol)-9-yl)benzene).
Adjacent to an electron transport layer (ETL), a cathode layer C may be located. Exemplarily, a cathode layer C may include or may consist of a metal (e.g., Al, Au, Ag, Pt, Cu, Zn, Ni, Fe, Pb, LiF, Ca, Ba, Mg, In, W, or Pd) or a metal alloy. For practical reasons, a cathode layer C may also consist of (essentially) intransparent (non-transparent) metals such as Mg, Ca or Al. Alternatively or additionally, a cathode layer C may also include graphite and or carbon nanotubes (CNTs). Alternatively, a cathode layer C may also consist of nanoscale silver wires.
In a preferred embodiment, the organic electroluminescent device includes at least the following layers:
In a preferred embodiment, the organic electroluminescent device includes at least the following layers:
In a preferred embodiment, the organic electroluminescent device is an OLED, which includes the following layer structure:
Preferably, the order of the layers herein is A-HTL-EXL-B-ETL-C.
In one embodiment, the organic electroluminescent device is an OLED, which includes the following layer structure:
Preferably, the order of the layers herein is A-HTL-B-EXL-ETL-C.
In one embodiment, the exciton management layer EXL has a thickness, which is less than 15 nm.
In a preferred embodiment, the exciton management layer EXL has a thickness, which is less than 10 nm.
In a preferred embodiment, the exciton management layer EXL has a thickness, which is equal to or less than 5 nm.
In a preferred embodiment, the exciton management layer EXL has a thickness, which is less than 5 nm.
As known to the person skilled in the art, triplet-triplet annihilation (TTA) materials can be used as host materials HB. The TTA material enables triplet-triplet annihilation. Triplet-triplet annihilation may preferably result in a photon up-conversion. Accordingly, two, three or even more photons may facilitate photon up-conversion from the lowermost excited triplet state (T1TTA) to the first excited singlet state S1TTA of the TTA material HTTA. In a preferred embodiment, two photons facilitate photon up-conversion from T1TTA to S1TTA Triplet-triplet annihilation may thus be a process that through a number of energy transfer steps, may combine two (or optionally more than two) low frequency photons into one photon of higher frequency.
Optionally, the TTA material may include an absorbing moiety, a sensitizer moiety, and an emitting moiety (or annihilator moiety). In this context, an emitting moiety may, for example, be a polycyclic aromatic moiety such as, benzene, biphenyl, triphenyl, triphenylene, naphthalene, anthracene, phenalene, phenanthrene, fluorene, pyrene, chrysene, perylene, azulene. In a preferred embodiment, the polycyclic aromatic moiety includes an anthracene moiety or a derivative thereof. A sensitizer moiety and an emitting moiety may be located in two different chemical compounds (i.e., separated chemical entities) or may be both moieties embraced by one chemical compound.
According to the present invention, a TTA material is characterized in that it exhibits triplet-triplet annihilation from the lowermost excited triplet state (T1N) resulting in a triplet-triplet annihilated first excited singlet state S1N, having an energy of up to two times the energy of T1N.
According to the invention, a triplet-triplet annihilation (TTA) material converts energy from its first excited triplet state T1N to its first excited singlet state S1N by triplet-triplet annihilation.
In one embodiment of the present invention, a TTA material is characterized in that it exhibits triplet-triplet annihilation from T1N resulting in S1N, wherein S1N has an energy of 1.01 to 2 fold, 1.1 to 1.9 fold, 1.2 to 1.5 fold, 1.4 to 1.6 fold, or 1.5 to 2 fold times the energy of T1N.
As used herein, the terms “TTA material” and “TTA compound” may be understood interchangeably.
Typical “TTA material” can be found in the state of the art related to blue fluorescent OLEDs, as described by Kondakov (Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2015, 373:20140321). Such blue fluorescent OLEDs employ aromatic hydrocarbons such as anthracene derivatives as the main component (host) in the EML.
In a preferred embodiment, the TTA material enables sensitized triplet-triplet annihilation. Optionally, the TTA material may include one or more polycyclic aromatic structures. In a preferred embodiment, the TTA material includes at least one polycyclic aromatic structure and at least one further aromatic residue.
In a preferred embodiment of the invention, the TTA material HTTA is an anthracene derivative.
In one embodiment, the TTA material HTTA is an anthracene derivate of the following formula TTA
In one embodiment, the TTA material HTTA is an anthracene derivate of the following formula TTA, wherein
In one embodiment, HTTA is an anthracene derivate of the following formula TTA, wherein at least one of A1 is hydrogen. In one embodiment, HTTA is an anthracene derivate of the following formula TTA, wherein at least two of A1 are hydrogen. In one embodiment, HTTA is an anthracene derivate of the following formula TTA, wherein at least three of A1 are hydrogen. In one embodiment, HTTA is an anthracene derivate of the following formula TTA, wherein all of A1 are each hydrogen.
In one embodiment, HTTA is an anthracene derivate of the following formula TTA, wherein one of Ar is a residue selected from the group consisting of phenyl, naphthyl, phenanthryl, pyrenyl, triphenylenyl, dibenzoanthracenyl, fluorenyl, benzofluorenyl, anthracenyl, phenanthrenyl, benzonaphthofuranyl, benzonaphthothiophenyl, dibenzofuranyl, dibenzothiophenyl,
which may be each optionally substituted with one or more residues selected from the group consisting of C6-C60-aryl, C3-C57-heteroaryl, halogen, and C1-C40-(hetero)alkyl.
In one embodiment, HTTA is an anthracene derivate of the following formula TTA, wherein both Ar are residues each independently from each other selected from the group consisting of phenyl, naphthyl, phenanthryl, pyrenyl, triphenylenyl, dibenzoanthracenyl, fluorenyl, benzofluorenyl, anthracenyl, phenanthrenyl, benzonaphthofuranyl, benzonaphthothiophenyl, dibenzofuranyl, dibenzothiophenyl,
which may be each optionally substituted with one or more residues selected from the group consisting of C6-C60-aryl, C3-C57-heteroaryl, halogen, and C1-C40-(hetero)alkyl.
In one embodiment, the TTA material HTTA is an anthracene derivate selected from the following:
In one embodiment, the exciton management layer EXL includes a TTA material and an additional emitter.
In a preferred embodiment, the exciton management layer EXL includes a TTA material and an additional emitter, wherein the additional emitter in the exciton management layer EXL is a small full width at half maximum (FWHM) emitter SB, which emits light with a full width at half maximum (FWHM) of less than or equal to 0.25 eV and with an emission maximum between 440 and 480 nm.
Furthermore, the organic electroluminescent device may optionally include one or more protective layers protecting the device from damaging exposure to harmful species in the environment including, exemplarily moisture, vapor and/or gases.
An electroluminescent device (e.g., an OLED) may further, optionally, include a protection layer between an electron transport layer (ETL) D and a cathode layer C (which may be designated as electron injection layer (EIL)). This layer may include lithium fluoride, caesium fluoride, silver, Liq (8-hydroxyquinolinolatolithium), Li2O, BaF2, MgO and/or NaF.
Unless otherwise specified, any of the layers, including any of the sublayers, of the various embodiments may be deposited by any suitable method. The layers in the context of the present invention, including at least one light-emitting layer B (which may consist of a single (sub)layer or may include more than one sublayers) and/or one or more sublayers thereof, may optionally be prepared by means of liquid processing (also designated as “film processing”, “fluid processing”, “solution processing” or “solvent processing”). This means that the components included in the respective layer are applied to the surface of a part of a device in liquid state. Preferably, the layers in the context of the present invention, including the at least one light-emitting layer B and/or one or more sublayers thereof, may be prepared by means of spin-coating. This method well-known to those skilled in the art allows obtaining thin and (essentially) homogeneous layers and/or sublayers.
Alternatively, the layers in the context of the present invention, including the at least one light-emitting layer B and/or one or more sublayers thereof, may be prepared by other methods based on liquid processing such as, e.g., casting (e.g., drop-casting) and rolling methods, and printing methods (e.g., inkjet printing, gravure printing, blade coating). This may optionally be carried out in an inert atmosphere (e.g., in a nitrogen atmosphere).
In another preferred embodiment, the layers in the context of the present invention, including the at least one light-emitting layer B and/or one or more sublayers thereof, may be prepared by any other method known in the art, including but not limited to vacuum processing methods well-known to those skilled in the art such as, e.g., thermal (co-)evaporation, organic vapor phase deposition (OVPD), and deposition by organic vapor jet printing (OVJP).
One of the purposes of interest of an organic electroluminescent device may be the generation of the organic electroluminescent device via vacuum-deposition.
Accordingly, a further aspect of the present invention to a method for generating an organic electroluminescent device including the steps
In a preferred embodiment, the organic electroluminescent device is generated, wherein a light-emitting layer B is evaporated via vacuum-deposition and subsequently, an exciton management layer EXL is evaporated via vacuum-deposition. It will be understood that, in this embodiment, the exciton management layer EXL will preferably be deposited via vacuum-deposition on the light-emitting layer B. In other words, the exciton management layer EXL is preferably in direct contact with the light-emitting layer B. Thus, it is directly adjacent.
In a preferred embodiment, the organic electroluminescent device is generated, wherein an exciton management layer EXL is evaporated via vacuum-deposition and subsequently, a light-emitting layer B is evaporated via vacuum-deposition. It will be understood that, in this embodiment, the light-emitting layer B will preferably be deposited via vacuum-deposition on the exciton management layer EXL. In other words, the exciton management layer EXL is preferably in direct contact with the light-emitting layer B. Thus, it is directly adjacent.
When preparing layers, optionally including one or more sublayers thereof, by means of liquid processing, the solutions including the components of the (sub)layers (i.e., with respect to the light-emitting layer B of the present invention one or more TADF material EB, optionally one or more excitation energy transfer components EET-2, one or more small FWHM emitters SB, and optionally one or more host materials HB) may further include a volatile organic solvent. Such volatile organic solvent may optionally be one selected from the group consisting of tetrahydrofuran, dioxane, chlorobenzene, diethylene glycol diethyl ether, 2-(2-ethoxyethoxy)ethanol, gamma-butyrolactone, N-methyl pyrrolidinone, ethoxyethanol, xylene, toluene, anisole, phenetole, acetonitrile, tetrahydrothiophene, benzonitrile, pyridine, trihydrofuran, triarylamine, cyclohexanone, acetone, propylene carbonate, ethyl acetate, benzene and PGMEA (propylene glycol monoethyl ether acetate). Also a combination of two or more solvents may be used. After applied in liquid state, the layer may subsequently be dried and/or hardened by any means of the art, exemplarily at ambient conditions, at increased temperature (e.g., about 50° C. or about 60° C.) or at diminished pressure.
The organic electroluminescent device as a whole may also form a thin layer of a thickness of not more than 5 mm, not more than 2 mm, not more than 1 mm, not more than 0.5 mm, not more than 0.25 mm, not more than 100 μm, or not more than 10 μm.
An organic electroluminescent device (e.g., an OLED) may be small-sized (e.g., having a surface not larger than 5 mm2, or even not larger than 1 mm2), medium-sized (e.g., having a surface in the range of 0.5 to 20 cm2), or a large-sized (e.g., having a surface larger than 20 cm2). An organic electroluminescent device (e.g., an OLED) according to the present invention may optionally be used for generating screens, as large-area illuminating device, as luminescent wallpaper, luminescent window frame or glass, luminescent label, luminescent poser or flexible screen or display. Next to the common uses, an organic electroluminescent device (e.g., an OLED) may exemplarily also be used as luminescent films, “smart packaging” labels, or innovative design elements. Further they are usable for cell detection and examination (e.g., as bio labelling).
Composition of the Light-Emitting Layer (EML) B
In the following, when describing the composition of the light-emitting layer B of the organic electroluminescent device according to the present invention in more detail, reference is in some cases made to the content of certain materials in form of percentages. It is to be noted that, unless stated otherwise for specific embodiments, all percentages refer to weight percentages, which has the same meaning as percent by weight or % by weight ((weight/weight), (w/w), wt. %). It is understood that, when for example stating that the content of one or more small FWHM emitters SB in a specific composition is exemplarily 1%, this is to mean that the total weight of the one or more small FWHM emitters SB (i.e. of all SB-molecules combined) is 1% by weight, i.e. accounts for 1% of the total weight of the respective light-emitting layer B. It is understood that, whenever the composition of a light-emitting layer B is specified by providing the preferred content of its components in % by weight, the total content of all components adds up to 100% by weight (i.e. the total weight of the respective light-emitting layer B).
The host material HB, the TADF material EB and the small FWHM emitter SB may be included in the organic electroluminescent device according to the present invention in any amount and any ratio.
In one embodiment, in the organic electroluminescent device according to the present invention, the light-emitting layer B includes or consists of:
In one embodiment, in the organic electroluminescent device according to the present invention, the light-emitting layer B includes or consists of:
In a preferred embodiment, in the organic electroluminescent device according to the present invention, the light-emitting layer B includes or consists of:
In one embodiment, in the organic electroluminescent device according to the present invention, the light-emitting layer B includes or consists of:
In a preferred embodiment, in the organic electroluminescent device according to the present invention, the light-emitting layer B includes or consists of:
In a preferred embodiment, in the organic electroluminescent device according to the present invention, the light-emitting layer B includes or consists of:
In a preferred embodiment, in the organic electroluminescent device according to the present invention, the light-emitting layer B includes or consists of:
In a preferred embodiment, in the organic electroluminescent device according to the present invention, the light-emitting layer B includes or consists of:
In a preferred embodiment, in the organic electroluminescent device according to the present invention, the light-emitting layer B includes or consists of:
In a preferred embodiment, in the organic electroluminescent device according to the present invention, the light-emitting layer B includes or consists of:
In a preferred embodiment, in the organic electroluminescent device according to the present invention, the light-emitting layer B includes or consists of:
In a preferred embodiment, in the organic electroluminescent device according to the present invention, the light-emitting layer B includes or consists of:
In a preferred embodiment, in the organic electroluminescent device according to the present invention, the light-emitting layer B includes or consists of:
In a preferred embodiment of the invention, the light-emitting layer B includes less than or equal to 5% by weight, referred to the total weight of the light-emitting layer B, of the excitation energy transfer component EET-2 (meaning the total content of EET-2 in the respective light-emitting layer B is equal to or less than 5% by weight).
In a preferred embodiment of the invention, the light-emitting layer B includes less than or equal to 5% by weight, referred to the total weight of the light-emitting layer B, of the excitation energy transfer component EET-2 (meaning the total content of EET-2 in the respective light-emitting layer B is equal to or less than 5% by weight).
In a preferred embodiment of the invention, the light-emitting layer B includes less than or equal to 3% by weight, referred to the total weight of the light-emitting layer B, of the excitation energy transfer component EET-2 (meaning the total content of EET-2 in the respective light-emitting layer B is equal to or less than 3% by weight).
In one embodiment of the invention, the light-emitting layer B includes less than or equal to 5% by weight, referred to the total weight of the light-emitting layer B, of the small FWHM emitter SB (meaning the total content of SB in the respective light-emitting layer B is equal to or less than 5% by weight).
In a preferred embodiment of the invention, the light-emitting layer B includes less than or equal to 3% by weight, referred to the total weight of the light-emitting layer B, of the small FWHM emitter SB (meaning the total content of SB in the respective light-emitting layer B is equal to or less than 3% by weight).
In one embodiment of the invention, the light-emitting layer B includes less than or equal to 1% by weight, referred to the total weight of the light-emitting layer B, of the small FWHM emitter SB (meaning the total content of SB in the respective light-emitting layer B is equal to or less than 1% by weight).
In a preferred embodiment of the invention, the light-emitting layer B includes 15-50% by weight, referred to the total weight of the light-emitting layer B, of the TADF material EB (meaning the total content of EB in the respective light-emitting layer B is in the range of 15-50% by weight).
In a preferred embodiment of the invention, the light-emitting layer B includes 20-50% by weight, referred to the total weight of the light-emitting layer B, of the TADF material EB (meaning the total content of EB in the respective light-emitting layer B is in the range of 20-50% by weight).
In a preferred embodiment of the invention, the light-emitting layer B includes 20-45% by weight, referred to the total weight of the light-emitting layer B, of the TADF material EB (meaning the total content of EB in the respective light-emitting layer B is in the range of 20-45% by weight).
S1-T1-Energy Relations
In the context of the present invention:
In one embodiment of the invention, the relations expressed by the following formulas (7) to (9) apply to materials included in the light-emitting layer B:
E(S1H)>E(S1E) (7)
E(S1H)>E(S1EET-2) (8)
E(S1H)>E(S1S) (9)
Accordingly, the lowermost excited singlet state S1H of the host material HB is preferably higher in energy than the lowermost excited singlet state S1E of the TADF material EB (formula 7) and higher in energy than the lowermost excited singlet state S1EET-2 of the optional excitation energy transfer component EET-2 (formula 8) and higher in energy than the lowermost excited singlet state S1S of the small FWHM emitter SB (formula 9).
In one embodiment, the aforementioned relations expressed by formulas (7) to (9) apply to materials included in the light-emitting layer B of the organic electroluminescent device according to the invention.
In one embodiment of the invention, one or both of the relations expressed by the following formulas (10) and (11) apply to materials included in the same light-emitting layer B:
E(S1E)>E(S1S) (10)
E(S1EET-2)>E(S1S) (11).
Accordingly, the lowermost excited singlet state S1E of the TADF material EB(formula 10) and/or the lowermost excited singlet state S1EET-2 of the optional excitation energy transfer component EET-2 (formula 11) may preferably be higher in energy than the lowermost excited singlet state S1 of the small FWHM emitter SB.
In one embodiment, one or both of the aforementioned relations expressed by formulas (10) and (11) may apply to materials included in the 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 (7) to (11) apply to materials included in the same light-emitting layer B:
E(S1H)>E(S1E) (7)
E(S1H)>E(S1EET-2) (8)
E(S1H)>E(S1S) (9)
E(S1E)>E(S1S) (10)
E(S1EET-2)>E(S1S) (11).
In one embodiment, the aforementioned relations expressed by formulas (7) to (11) apply to materials included in the 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 (13) and (14) apply to materials included in the light-emitting layer B:
E(T1H)>E(T1E) (13)
E(T1E)≥E(T1EET-2) (14).
Accordingly, the lowermost excited triplet state T1H of the host material HB is preferably higher in energy than the lowermost excited triplet state T1E of the TADF material EB (formula 13); Additionally, the lowermost excited triplet state T1E of the TADF material EB is preferably equal in energy to or higher in energy than the lowermost excited triplet state T1EET-2 of the optional excitation energy transfer component EET-2 (formula 14).
In one embodiment, the aforementioned relations expressed by formulas (13) and (14) apply to materials included in the 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 (14) to (16) apply to materials included in the same light-emitting layer B:
E(T1E)≥E(T1EET-2) (14)
E(T1EET-2)>E(S1S) (15)
E(T1EET-2)>E(T1S) (16).
Accordingly, the lowermost excited triplet state T1E of the TADF material EB is preferably equal in energy to or higher in energy than the lowermost excited triplet state T1EET-2 of the optional excitation energy transfer component EET-2 (formula 14); the lowermost excited triplet state T1EET-2 of the optional excitation energy transfer component EET-2 is preferably higher in energy than the lowermost excited singlet state S1S of the small FWHM emitter SB (formula 15); the lowermost excited triplet state T1EET-2 of the optional excitation energy transfer component EET-2 is preferably higher in energy than the lowermost excited triplet state T1S of the small FWHM emitter SB (formula 16).
In one embodiment, the aforementioned relations expressed by formulas (14) to (16) apply to materials included in the 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 (7) to (10) and the following formula (15) apply:
E(S1H)>E(S1E) (7)
E(S1H)>E(S1EET-2) (8)
E(S1H)>E(S1S) (9)
E(S1E)>E(S1S) (10)
E(T1EET-2)>E(S1S) (15).
In one embodiment, the aforementioned relations expressed by formulas (7) to (10) and formula (15) apply to materials included the 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 (17) and (10) apply to materials included in the light-emitting layer B:
E(T1EET-2)>E(T1E) (17)
E(S1E)>E(S1S) (10).
Accordingly, the lowermost excited triplet state T1EET-2 of the optional excitation energy transfer component EET-2 may be higher in energy than the lowermost excited triplet state T1E of the TADF material EB (formula 17); and the lowermost excited singlet state S1E of the TADF material EB may be higher in energy the lowermost excited singlet state S1S of the small FWHM emitter SB (formula 10).
In an alternative embodiment, the aforementioned relations expressed by formulas (17) and (10) apply to materials included in the 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 (18), (15), (19), and (20) apply to materials included in the light-emitting layer B:
E(T1H)>E(T1EET-2) (18)
E(T1EET-2)>E(S1S) (15)
E(T1H)>E(S1E) (19)
E(T1E)>E(T1EET-2) (20).
Accordingly, the lowermost excited triplet state T1H the host material HB is preferably higher in energy than the lowermost excited triplet state T1EET-2 of the optional excitation energy transfer component EET-2 (formula 18); and the lowermost excited triplet state T1EET-2 of the optional excitation energy transfer component EET-2 is preferably higher in energy than the lowermost excited singlet state S1S of the small FWHM emitter SB (formula 15); and the lowermost excited triplet state T1H of the host material HB is preferably higher in energy than the lowermost excited singlet state S1E of the TADF material EB (formula 19); and the lowermost excited triplet state T1E of the TADF material EB is preferably higher in energy than the lowermost excited triplet state T1EET-2 of the optional excitation energy transfer component EET-2 (formula 20).
In one embodiment, the aforementioned relations expressed by formulas (18), (15), (19), and (20) apply to materials included in the light-emitting layer B of the organic electroluminescent device according to the invention.
In one embodiment of the invention, the lowermost excited triplet state T1EET-2 of the optional excitation energy transfer component EET-2 is equal to or higher in energy than the lowermost excited triplet state T1E of the TADF material EB:
E(T1EET-2)≥E(T1E) and
the difference in energy E(T1EET-2)−E(S1S) of the lowermost excited triplet state T1EET-2 of the optional excitation energy transfer component EET-2 and the lowermost excited singlet state S1 of the small FWHM emitter SB is equal to or smaller than 0.3 eV:
E(T1EET-2)−E(S1S)≤0.3 eV.
In one embodiment of the invention, the lowermost excited triplet state T1E of the TADF material EB is higher in energy than the lowermost excited triplet state T1EET-2 of the optional excitation energy transfer component EET-2:
E(T1E)>E(T1EET-2) and
the difference in energy E(T1E)−E(S1S) of the lowermost excited triplet state T1E of the TADF material EB and the lowermost excited singlet state S1S of the small FWHM emitter SB is equal to or smaller than 0.3 eV:
E(T1E)−E(S15)≤0.3 eV.
In a preferred embodiment of the invention, the lowermost excited triplet state T1EET-2 of the optional excitation energy transfer component EET-2 is equal to or higher in energy than the lowermost excited triplet state T1E of the TADF material EB:
E(T1EET-2)≥E(T1E)
and the difference in energy E(T1EET-2)−E(S1S) of the lowermost excited triplet state T1EET-2 of the optional excitation energy transfer component EET-2 and the lowermost excited singlet state S1 of the small FWHM emitter SB is equal to or smaller than 0.2 eV:
E(T1EET-2)−E(S1S)≤0.2 eV.
In a preferred of the invention, the lowermost excited triplet state T1E of the TADF material EB is higher in energy than the lowermost excited triplet state T1EET-2 of the optional excitation energy transfer component EET-2:
E(T1E)>E(T1EET-2) and
the difference in energy E(T1E)−E(S1S) of the lowermost excited triplet state T1E of the TADF material EB and the lowermost excited singlet state S1S of the small FWHM emitter SB is equal to or smaller than 0.2 eV:
E(T1E)−E(S1S)≤0.2 eV.
In one embodiment of the invention, the lowermost excited triplet state T1EET-2 of the optional excitation energy transfer component EET-2 is equal to or higher in energy than the lowermost excited triplet state T1E of the TADF material EB:
E(T1EET-2)≥E(T1E) and
the difference in energy E(T1EET-2)−E(T1) of the lowermost excited triplet state T1EET-2 of the optional excitation energy transfer component EET-2 and the lowermost excited triplet state T1S of the small FWHM emitter SB is equal to or smaller than 0.3 eV:
E(T1EET-2)−E(T1S)≤0.3 eV.
In one embodiment of the invention, the lowermost excited triplet state T1E of the TADF material EB is higher in energy than the lowermost excited triplet state T1EET-2 of the optional excitation energy transfer component EET-2:
E(T1E)>E(T1EET-2) and
the difference in energy E(T1EET-2)−E(T1S) of the lowermost excited triplet state T1EET-2 of the optional excitation energy transfer component EET-2 and the lowermost excited triplet state T1S of the small FWHM emitter SB is equal to or smaller than 0.3 eV:
E(T1E)−E(T15)≤0.3 eV.
In one embodiment of the invention, the lowermost excited triplet state T1EET-2 of the optional excitation energy transfer component EET-2 is higher in energy than the lowermost excited triplet state T1E of the TADF material EB:
E(T1EET-2)>E(T1E) and
and the difference in energy E(T1EET-2)−E(T1) of the lowermost excited triplet state T1EET-2 of the optional excitation energy transfer component EET-2 and the lowermost excited triplet state T1S of the small FWHM emitter SB is equal to or smaller than 0.2 eV:
E(T1EET-2)−E(T1S)≤0.2 eV.
In one embodiment of the invention, the lowermost excited triplet state T1E of the TADF material EB is higher in energy than the lowermost excited triplet state T1EET-2 of the optional excitation energy transfer component EET-2:
E(T1E)>E(T1EET-2) and
and the difference in energy E(T1EET-2)−E(T1) of the lowermost excited triplet state T1EET-2 of the optional excitation energy transfer component EET-2 and the lowermost excited triplet state T1S of the small FWHM emitter SB is equal to or smaller than 0.2 eV:
E(T1EET-2)−E(T1S)≤0.2 eV.
HOMO-, LUMO-Energy Relations
In the context of the present invention:
In a preferred embodiment, the relations expressed by the following formulas (1) to (3) apply to materials included in the light-emitting layer B:
E
LUMO(EB)<ELUMO(HB) (1)
E
LUMO(EB)<ELUMO(EET-2) (2)
E
LUMO(EB)<ELUMO(SB) (3)
In a preferred embodiment, the relations expressed by the following formulas (4) to (6) apply to materials included in the same light-emitting layer B:
E
HOMO(EET-2)≥EHOMO(HB) (4)
E
HOMO(EET-2)≥EHOMO(EB) (5)
E
HOMO(EET-2)≥EHOMO(SB) (6).
In a preferred embodiment, the relations expressed by the aforementioned formulas (1) to (6) apply to materials included in the light-emitting layer B.
In one embodiment of the invention, the highest occupied molecular orbital HOMO(SB) of the small full width at half maximum (FWHM) emitter SB having an energy EHOMO(SB) is higher in energy than the highest occupied molecular orbital HOMO(HB) of the host material HB having an energy EHOMO(HB):
E
HOMO(SB)>EHOMO(HB).
In one embodiment of the invention, the highest occupied molecular orbital HOMO(SB) of the small full width at half maximum (FWHM) emitter SB having an energy EHOMO(SB) is higher in energy than the highest occupied molecular orbital HOMO(EB) of the TADF material EB having an energy EHOMO(EB):
E
HOMO(SB)>EHOMO(EB).
In one embodiment of the invention, the highest occupied molecular orbital HOMO(EET-2) of the optional excitation energy transfer component EET-2 having an energy EHOMO(EET-2) is higher in energy than the highest occupied molecular orbital HOMO(EB) of the TADF material EB having an energy EHOMO(EB):
E
HOMO(EET-2)>EHOMO(EB).
In one embodiment of the invention, the highest occupied molecular orbital HOMO(EET-2) of the optional excitation energy transfer component EET-2 having an energy EHOMO(EET-2) is higher in energy than the highest occupied molecular orbital HOMO(HB) of the host material HB having an energy EHOMO(HB):
E
HOMO(EET-2)>EHOMO(HB).
In one embodiment of the invention, the highest occupied molecular orbital HOMO(EET-2) of the optional excitation energy transfer component EET-2 having an energy EHOMO(EET-2) is higher in energy than the highest occupied molecular orbital HOMO(SB) of the small full width at half maximum (FWHM) emitter SB having an energy EHOMO(SB):
E
HOMO(EET-2)>EHOMO(SB).
In one embodiment of the invention, the highest occupied molecular orbital HOMO(EB) of the TADF material EB is equal in energy to or lower in energy than the highest occupied molecular orbital HOMO(SB) of the small FWHM emitter SB:
E
HOMO(EB)≤EHOMO(SB).
In one embodiment of the invention, the difference (in energy) between the highest occupied molecular orbital HOMO(EET-2) of the optional excitation energy transfer component EET-2 having an energy EHOMO(EET-2) and the highest occupied molecular orbital HOMO(SB) of the small full width at half maximum (FWHM) emitter SB having an energy EHOMO(SB) is smaller than 0.3 eV:
E
HOMO(EET-2)−EHOMO(SB)<0.3 eV.
In one embodiment of the invention, the difference (in energy) between the highest occupied molecular orbital HOMO(EET-2) of the optional excitation energy transfer component EET-2 having an energy EHOMO(EET-2) and the highest occupied molecular orbital HOMO(SB) of the small full width at half maximum (FWHM) emitter SB having an energy EHOMO(SB) is smaller than 0.2 eV:
E
HOMO(EET-2)−EHOMO(SB)<0.2 eV.
In one embodiment of the invention, the difference (in energy) between the highest occupied molecular orbital HOMO(EET-2) of the optional excitation energy transfer component EET-2 having an energy EHOMO(EET-2) and the highest occupied molecular orbital HOMO(SB) of the small full width at half maximum (FWHM) emitter SB having an energy EHOMO(SB) is larger than 0.0 eV and smaller than 0.8 eV:
0.0 eV<EHOMO(EET-2)−EHOMO(SB)<0.8 eV.
In a preferred embodiment of the invention, the difference in energy between the highest occupied molecular orbital HOMO(EET-2) of the optional excitation energy transfer component EET-2 having an energy EHOMO(EET-2) and the highest occupied molecular orbital HOMO(SB) of the small full width at half maximum (FWHM) emitter SB having an energy EHOMO(SB) is larger than 0 eV (EHOMO(EET-2)−EHOMO(SB)>0 eV), preferably larger than 0.1 eV (EHOMO(EET-2)−EHOMO(SB)>0.1 eV), more preferably larger than 0.2 eV (EHOMO(EET-2)−EHOMO(SB)>0.2 eV), or even larger than 0.3 eV (EHOMO(EET-2)−EHOMO(SB)>0.3 eV).
In a preferred embodiment of the invention, the difference in energy between the highest occupied molecular orbital HOMO(EET-2) of the optional excitation energy transfer component EET-2 having an energy EHOMO(EET-2) and the highest occupied molecular orbital HOMO(EB) of the TADF material EB having an energy EHOMO(EB) is larger than 0 eV (EHOMO(EET-2)−EHOMO(EB)>0 eV), preferably larger than 0.1 eV (EHOMO(EET-2)−EHOMO(EB)>0.1 eV), more preferably larger than 0.2 eV (EHOMO(EET-2)−EHOMO(EB)>0.2 eV), more preferably larger than 0.3 eV (EHOMO(EET-2)−EHOMO(EB)>0.3 eV), even more preferably larger than 0.4 eV (EHOMO(EET-2)−EHOMO(EB)>0.4 eV), in particular larger than 0.5 eV (EHOMO(EET-2)−EHOMO(EB)>0.5 eV).
In a preferred embodiment of the invention, the difference in energy between the highest occupied molecular orbital HOMO(EET-2) of the optional excitation energy transfer component EET-2 having an energy EHOMO(EET-2) and the highest occupied molecular orbital HOMO(HB) of the host material HB having an energy EHOMO(HB) is larger than 0 eV (EHOMO(EET-2)−EHOMO(HB)>0 eV), preferably larger than 0.1 eV (EHOMO(EET-2)−EHOMO(HB)>0.1 eV), more preferably larger than 0.2 eV (EHOMO(EET-2)−EHOMO(HB)>0.2 eV), more preferably larger than 0.3 eV (EHOMO(EET-2)−EHOMO(HB)>0.3 eV), even more preferably larger than 0.4 eV (EHOMO(EET-2)−EHOMO(HB)>0.4 eV), in particular larger than 0.5 eV (EHOMO(EET-2)−EHOMO(HB)>0.5 eV).
In one embodiment of the invention, the difference in energy between the lowest unoccupied molecular orbital LUMO(SB) of the small full width at half maximum (FWHM) emitter SB having an energy ELUMO(SB) and the lowest unoccupied molecular orbital LUMO(EB) of the TADF material having an energy ELUMO(EB) is larger than 0.0 eV and smaller than 0.3 eV:
0.0 eV<ELUMO(SB)−ELUMO(EB)<0.3 eV.
In a preferred embodiment of the invention, the difference in energy between the lowest unoccupied molecular orbital LUMO(SB) of the small FWHM emitter SB having an energy ELUMO(SB) and the lowest unoccupied molecular orbital LUMO(EB) of the TADF material EB having an energy ELUMO(EB) is larger than 0 eV (ELUMO(SB)−ELUMO(EB)>0 eV), preferably larger than 0.1 eV (ELUMO(SB)−ELUMO(EB)>0.1 eV), more preferably larger than 0.2 eV (ELUMO(SB)−ELUMO(EB)>0.2 eV), particularly preferably larger than 0.3 eV (ELUMO(SB)−ELUMO(EB)>0.3 eV).
In a preferred embodiment of the invention, the difference in energy between the lowest unoccupied molecular orbital LUMO(EET-2) of the optional excitation energy transfer component EET-2 having an energy ELUMO(EET-2) and the lowest unoccupied molecular orbital LUMO(EB) of the TADF material EB having an energy ELUMO(EB) is larger than 0 eV (ELUMO(EET-2)−ELUMO(EB)>0 eV), preferably larger than 0.1 eV (ELUMO(EET-2)−ELUMO(EB)>0.1 eV), more preferably larger than 0.2 eV (ELUMO(EET-2)−ELUMO(EB)>0.2 eV), more preferably larger than 0.3 eV (ELUMO(EET-2)−ELUMO(EB)>0.3 eV), even more preferably larger than 0.4 eV (ELUMO(EET-2)−ELUMO(EB)>0.4 eV), in particular larger than 0.5 eV (ELUMO(EET-2)−ELUMO(EB)>0.5 eV).
In a preferred embodiment of the invention, the difference in energy between the lowest unoccupied molecular orbital LUMO(HB) of at least one, preferably each, host material HB having an energy ELUMO(HB) and the lowest unoccupied molecular orbital LUMO(EB) of the TADF material EB having an energy ELUMO(EB) is larger than 0 eV (ELUMO(HB)−ELUMO(EB)>0 eV), preferably larger than 0.1 eV (ELUMO(HB)−ELUMO(EB)>0.1 eV), more preferably larger than 0.2 eV (ELUMO(HB)−ELUMO(EB)>0.2 eV), more preferably larger than 0.3 eV (ELUMO(HB)−ELUMO(EB)>0.3 eV), even more preferably larger than 0.4 eV (ELUMO(HB)−ELUMO(EB)>0.4 eV), in particular larger than 0.5 eV (ELUMO(HB)−ELUMO(EB)>0.5 eV).
Relations of Emission Maxima
In one embodiment of the invention, one or both of the relations expressed by formulas (21) and (22) apply to materials included in the light-emitting layer B:
|Eλmax(EET-2)−Eλmax(SB)|<0.30 eV (21),
|Eλmax(EB)−Eλmax(SB)|<0.30 eV (22),
which means: Within the light-emitting layer B, the difference in energy between the energy of the emission maximum Eλmax(EET-2) of the optional excitation energy transfer component EET-2 given in electron volts (eV) and the energy of the emission maximum Eλmax(SB) of the small FWHM emitter SB given in electron volts (eV) is smaller than 0.30 eV (formula 21); and/or: The difference in energy between the energy of the emission maximum Eλmax(EB) of the TADF material EB given in electron volts (eV) and the energy of the emission maximum Eλmax(SB) of the small FWHM emitter SB given in electron volts (eV) is smaller than 0.30 eV (formula 22).
In one embodiment, one or both of the aforementioned relations expressed by formulas (21) and (22) apply to materials included the light-emitting layer B of the organic electroluminescent device according to the invention.
In a preferred embodiment of the invention, one or both of the relations expressed by formulas (23) and (24) apply to materials included in the light-emitting layer B:
|Eλmax(EET-2)−Eλmax(SB)|<0.20 eV (23),
|Eλmax(EB)−Eλmax(SB)|<0.20 eV (24),
which means: Within the light-emitting layer B, the difference in energy between the energy of the emission maximum Eλmax(EET-2) of the optional excitation energy transfer component EET-2 given in electron volts (eV) and the energy of the emission maximum Eλmax(SB) of the small FWHM emitter SB given in electron volts (eV) is smaller than 0.20 eV (formula 23); and/or: The difference in energy between the energy of the emission maximum Eλmax(EB) of the TADF material EB given in electron volts (eV) and the energy of the emission maximum Eλmax(SB) of the small FWHM emitter SB given in electron volts (eV) is smaller than 0.20 eV (formula 24).
In one embodiment, one or both of the aforementioned relations expressed by formulas (23) and (24) apply to materials included in the light-emitting layers B of the organic electroluminescent device according to the invention.
In an even more preferred embodiment of the invention, one or both of the relations expressed by formulas (25) and (26) apply to materials included in the light-emitting layer B:
|Eλmax(EET-2)−Eλmax(SB)|<0.10 eV (25),
|Eλmax(EB)−Eλmax(SB)|<0.10 eV (26),
which means: Within the light-emitting layer B, the difference in energy between the energy of the emission maximum Eλmax(EET-2) of the optional excitation energy transfer component EET-2 given in electron volts (eV) and the energy of the emission maximum Eλmax(SB) of the small FWHM emitter SB given in electron volts (eV) is smaller than 0.10 eV (formula 25); and/or: The difference in energy between the energy of the emission maximum Eλmax(EB) of the TADF material EB given in electron volts (eV) and the energy of the emission maximum Eλmax(SB) of the small FWHM emitter SB given in electron volts (eV) is smaller than 0.10 eV (formula 26).
In one embodiment, the aforementioned relations expressed by formulas (25) and (26) apply to materials included in the light-emitting layer B of the organic electroluminescent device according to the invention.
In one embodiment of the invention, the relation expressed by formula (27) applies to materials included in the light-emitting layer B:
E
λmax(EET-2)>Eλmax(SB) (27),
which means that, within the light-emitting layer B, the energy of the emission maximum Eλmax(EET-2) of the optional excitation energy transfer component EET-2 given in electron volts (eV) is larger than the energy of the emission maximum Eλmax(SB) of the small FWHM emitter SB given in electron volts (eV).
In one embodiment of the invention, the relation expressed by formula (28) applies to materials included in the light-emitting layer B:
E
λmax(EB)>Eλmax(SB) (28),
which means that, within the light-emitting layer B, the energy of the emission maximum Eλmax(EB) of the TADF material EB given in electron volts (eV) is larger than the energy of the emission maximum Eλmax(SB) of the small FWHM emitter SB given in electron volts (eV).
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.
In a preferred embodiment, the electroluminescent device (e.g., an OLED) exhibits a LT95 value at constant current density J0=15 mA/cm2 of more than 100 h, preferably more than 200 h, more preferably more than 300 h, even more preferably more than 400 h, still 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 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 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 440 nm and 480 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/m2 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 450 nm and 475 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/m2 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 460 nm and 475 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/m2 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/or exhibits an emission maximum between 440 nm and 480 nm, preferably between 450 nm and 475 nm, more preferably between 460 nm and 475 nm and/or exhibits a LT80 value at 500 cd/m2 of 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 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 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.
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
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 blue light, in particular by using said organic electroluminescent device.
A further aspect of the invention relates to an organic electroluminescent device, wherein the following formula (29) applies to materials included in the light-emitting layer B:
440 nm≤λmax(SB)≤480 nm (29)
wherein λmax(SB) is the emission maximum of the small FWHM emitter SB and is given in nanometers (nm).
A further aspect of the invention relates to a method for generating light, including the steps of:
A further aspect of the invention relates to a method for generating light, including the steps of:
A further aspect of the invention relates to a method for generating light, including the steps of:
A further aspect of the invention relates to a method for generating light, including the steps of:
The skilled artisan understands that, depending on their structure, the TADF material EB (vide infra) and the excitation energy transfer components EET-2 (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 TADF material EB and the excitation energy transfer components EET-2 is not the emission of 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 small FWHM emitters SB. 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 (32) applies:
If, for example, the light-emitting layer B includes two small FWHM emitters SB with 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 SB. 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 HB included 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 HB, 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 HB, 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 SB) would preferably be a 3:1-mixture of the two host materials HB as 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 (32) preferably applies to all light-emitting layers B included in the device.
In one embodiment, the light-emitting layer B of the organic electroluminescent device according to the present invention, the aforementioned ratio FWHMD:FWHMSB is 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 emitter SB in 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 SB listed in Table 1S may not be understood as FWHMSB values in the context of equation (32) and the associated preferred embodiments of the present invention.
The examples and claims further illustrate the invention.
Host Material(s) HB
According to the invention, any of the one or more host materials HB included in any of the one or more light-emitting layers B may be a p-host HP exhibiting high hole mobility, an n-host HN exhibiting high electron mobility, or a bipolar host material HBP exhibiting both, high hole mobility and high electron mobility.
An n-host HN exhibiting high electron mobility in the context of the present invention preferably has a LUMO energy ELUMO(HN) equal to or smaller than −2.50 eV (ELUMO(HN)≤−2.50 eV), preferably ELUMO(HN)≤−2.60 eV, more preferably ELUMO(HN)≤−2.65 eV, and even more preferably ELUMO(HN)≤−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 HP exhibiting high hole mobility in the context of the present invention preferably has a HOMO energy EHOMO(HP) equal to or higher than −6.30 eV (EHOMO(HP)≥−6.30 eV), preferably EHOMO(HP)≥−5.90 eV, more preferably EHOMO(HP)≥−5.70 eV, even more preferably EHOMO(HP)≥−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 a preferred embodiment of the invention, in each light-emitting layer B of an organic electroluminescent device according to the present invention, at least one, preferably each, host material HB is a p-host HP which has a HOMO energy EHOMO(HP) equal to or higher than −6.30 eV (EHOMO(HP)≥−6.30 eV), preferably EHOMO(HP)≥−5.90 eV, more preferably EHOMO(HP)≥−5.70 eV, and even more preferably EHOMO(HP)≥−5.40 eV. The HOMO is the highest occupied molecular orbital.
In one embodiment of the invention, within each light-emitting layer B, at least one, preferably each p-host HP included in a light-emitting layer B has a HOMO energy EHOMO(HP) smaller than −5.60 eV.
A bipolar host HBP exhibiting high electron mobility in the context of the present invention preferably has a LUMO energy ELUMO(HBP) equal to or smaller than −2.50 eV (ELUMO(HBP)≤−2.50 eV), preferably ELUMO(HBP)≤−2.60 eV, more preferably ELUMO(HBP)≤−2.65 eV, and even more preferably ELUMO(HBP)<−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 HBP exhibiting high hole mobility in the context of the present invention preferably has a HOMO energy EHOMO(HBP) equal to or higher than −6.30 eV (EHOMO(HBP)≥−6.30 eV), preferably EHOMO(HBP)≥−5.90 eV, more preferably EHOMO(HBP)≥−5.70 eV and still even more preferably EHOMO(HBP)≥−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 HBP preferably each bipolar host material HBP, fulfills both of the following requirements:
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 HB in the context of the present invention.
In a preferred embodiment of the invention, each light-emitting layer B of the organic electroluminescent device according to the invention includes one or more p-hosts HP. In one embodiment of the invention, each light-emitting layer B of the organic electroluminescent device according to the invention includes only a single host material HB and this host material is a p-host HP.
In one embodiment of the invention, each light-emitting layer B of the organic electroluminescent device according to the invention includes one or more n-hosts HN. In another embodiment of the invention, each light-emitting layer B of the organic electroluminescent device according to the invention includes only a single host material HB and this host material is an n-host HN.
In one embodiment of the invention, each light-emitting layer B of the organic electroluminescent device according to the invention includes one or more bipolar hosts HBP. In one embodiment of the invention, each light-emitting layer B of the organic electroluminescent device according to the invention includes only a single host material HB and this host material is a bipolar host HBP.
In another embodiment of the invention, at least one light-emitting layer B of the organic electroluminescent device according to the invention includes at least two different host materials HB. In this case, the more than one host materials HB present in the respective light-emitting layer B may either all be p-hosts HP or all be n-hosts HN, or all be bipolar hosts HBP, 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 layers B, any of them may, independently of the one or more other light-emitting layers B, include either one host material HB or more than one host materials HB for 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 or ratios.
It is understood that, if a light-emitting layer B of the organic electroluminescent device according to the invention is composed of more than one sublayers, any of them may, independently of the one or more other sublayers, include either one host material HB or more than one host materials HB for 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 or ratios.
If included in the same light-emitting layer B of the organic electroluminescent device according to the invention, at least one p-host HP and at least one n-host HN may optionally form an exciplex. The person skilled in the art knows how to choose pairs of HP and HN, which form an exciplex and the selection criteria, including HOMO- and/or LUMO-energy level requirements of HP and HN. This is to say that, in case exciplex formation may be aspired, the highest occupied molecular orbital (HOMO) of the p-host material HP may be at least 0.20 eV higher in energy than the HOMO of the n-host material HN and the lowest unoccupied molecular orbital (LUMO) of the p-host material HP may be at least 0.20 eV higher in energy than the LUMO of the n-host material HN.
In a preferred embodiment of the invention, at least one host material HB(e.g., HP, HN, and/or HBP) 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 HB (HP, HN, and/or HBP) 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 HB, more preferably all host materials HB (HP, HN and/or HBP) 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 HB is a p-host HP.
In one embodiment of the organic electroluminescent device according to the present invention, in at least one, preferably each, light-emitting layer B, each host material HB is a p-host HP.
In a preferred embodiment of the invention, a p-host HP, optionally included in any of the one or more light-emitting layers B as a whole (consisting of one (sub)layer or including more than one sublayers), includes or consists of:
In an even more preferred embodiment of the invention, Z1 is at each occurrence a direct bond and adjacent substituents RII do not combine to form an additional ring system.
In a still even more preferred embodiment of the invention, a p-host HP optionally included in the organic electroluminescent device according to the invention is selected from the group consisting of the following structures:
In a preferred embodiment of the invention, an n-host HN optionally included in any of the one or more light-emitting layers 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 HN-I, HN-II, and HN-III:
In an even more preferred embodiment of the invention, an n-host HN optionally included in the organic electroluminescent device according to the invention is selected from the group consisting of the following structures:
In one embodiment of the invention, no n-host HN included in any light-emitting layer B of the organic electroluminescent device according to the invention contains any phosphine oxide groups and, in particular, no n-host HN is bis[2-(diphenylphosphino)phenyl] ether oxide (DPEPO).
Excitation Energy Transfer Components EET-2
For the light-emitting layer B, the TADF material EB and the optional excitation energy transfer components EET-2 are preferably selected so that they are able to transfer excitation energy to the small FWHM emitters SB included in the same light-emitting-layer B of the organic electroluminescent device according to the present invention.
To enable this energy transfer, there preferably is spectral overlap between the emission spectrum at room temperature (i.e. (approximately) 20° C.) (e.g. fluorescence spectrum of the TADF material EB and the absorption spectrum at room temperature (i.e. (approximately) 20° C.) of the small FWHM emitter SB to which EB is supposed to transfer energy. Thus, in a preferred embodiment, within the light-emitting layer B, there is spectral overlap between the emission spectrum at room temperature (i.e. (approximately) 20° C.) of the TADF material EB and the absorption spectrum of the small FWHM emitter SB. The absorption and emission spectra are recorded as described in a later subchapter of this text.
In a preferred embodiment of the invention, within the light-emitting layer B, the optional excitation energy transfer component EET-2 transfers excitation energy to the small FWHM emitter SB.
To enable this energy transfer, there preferably is spectral overlap between the emission spectrum at room temperature (i.e. (approximately) 20° C.) (e.g. fluorescence spectrum if EET-2 is a TADF material EB and phosphorescence spectrum if EET-2 is a phosphorescence material PB, vide infra) of the optional excitation energy transfer component EET-2 and the absorption spectrum at room temperature (i.e. (approximately) 20° C.) of the small FWHM emitter SB to which EET-2 is supposed to transfer energy. Thus, in a preferred embodiment, the light-emitting layer B, there is spectral overlap between the emission spectrum at room temperature (i.e. (approximately) 20° C.) of the optional excitation energy transfer component EET-2 and the absorption spectrum at room temperature (i.e. (approximately) 20° C.) of the small FWHM emitter SB. The absorption and emission spectra are recorded as described in a later subchapter of this text.
In an even more preferred embodiment of the invention, within the light-emitting layer B, the TADF material EB as well as the optional excitation energy transfer component EET-2 included in the light-emitting layer B transfer energy to the small FWHM emitter SB.
In a preferred embodiment of the invention, within the light-emitting layer B, both of the following two conditions are fulfilled:
In a preferred embodiment, the light-emitting layer B, the lowest unoccupied molecular orbital LUMO(EB) of the TADF material EB has an energy ELUMO(EB) of less than −2.3 eV: ELUMO(EB)<−2.3 eV.
In a preferred embodiment, the light-emitting layer B, the lowest unoccupied molecular orbital LUMO(EB) of the TADF material EB has an energy ELUMO(EB) of less than −2.6 eV: ELUMO(EB)<−2.6 eV.
In a preferred embodiment, within the light-emitting layer B, the highest occupied molecular orbital HOMO(EB) of the TADF material EB has an energy EHOMO(EB) higher than −6.3 eV: EHOMO(EB)>−6.3 eV.
In a preferred embodiment, within the light-emitting layer B, the following two conditions are fulfilled:
In one embodiment of the invention, within the light-emitting layer B, the optional excitation energy transfer component EET-2 fulfills at least one, preferably exactly one, of the following two conditions:
In a preferred embodiment, within the light-emitting layer B the TADF material EB exhibits a ΔEST value, which corresponds to the energy difference between the lowermost excited singlet state energy level E(S1E) and the lowermost excited triplet state energy level E(T1E) 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.
In a preferred embodiment, within the light-emitting layer B the optional excitation energy transfer component EET-2 includes at least one, preferably exactly one, transition metal with a standard atomic weight of more than 40 (meaning that EET-2 is a (transition) metal with an atomic weight of more than 40, wherein the transition metal may be in any oxidation state).
In a preferred embodiment of the invention, within each light-emitting layer B both of the following two conditions:
In a preferred embodiment of the invention, in the light-emitting layer B, the optional excitation energy transfer component EET-2 fulfills at least one, preferably exactly one, of the following two conditions:
In a preferred embodiment, within at least one, preferably each, light-emitting layer B at least one, preferably each optional excitation energy transfer component EET-2 includes iridium (Ir) or platinum (Pt) (meaning that at least one atom within the respective EET-2 is iridium (Ir) or platinum (Pt), wherein Ir and Pt may be in any oxidation state, vide infra).
As stated previously, a light-emitting layer B in the context of the present invention includes a TADF material EB and an optional excitation energy transfer component EET-2, wherein these two species are not identical (i.e. they do not have the same chemical formulas). This means that, within each light-emitting layer B of the organic electroluminescent device according to the present invention, the TADF material EB and the excitation energy transfer components EET-2 may for example be independently of each other selected from the group consisting of TADF-material EB but in any case, their chemical structures may not be identical. This is to say that within a light-emitting layer B no EB has the same chemical formula (or structure) as an EET-2.
In a particularly preferred embodiment, the optional excitation energy transfer component EET-2 optionally included in the organic electroluminescent device according to the present invention is a phosphorescence material PB as defined herein.
In a particularly preferred embodiment, the optional excitation energy transfer component EET-2 optionally included in the organic electroluminescent device according to the present invention is a TADF material which may have the structural characteristics as defined for the TADF material EB as defined herein.
It is understood that any preferred features, properties, and embodiments described in the following for a TADF material EB may also apply to the optional excitation energy transfer component EET-2, if the excitation energy transfer component is selected to be a TADF material.
It is also understood that any preferred features, properties, and embodiments described in the following for a phosphorescence material PB may also apply to the optional excitation energy transfer component EET-2, if the excitation energy transfer component is selected to be a phosphorescence material PB.
TADF Material(s) EB
As known to the person skilled in the art, light emission from emitter materials (i.e. emissive dopants), for example in organic light-emitting diodes (OLEDs), may include fluorescence from excited singlet states (typically the lowermost excited singlet state S1) and phosphorescence from excited triplet states (typically the lowermost excited triplet state T1).
In the context of the present invention, a fluorescence emitter is capable of emitting light at room temperature (i.e. (approximately) 20° C.) upon electronic excitation (for example in an organic electroluminescent device), wherein the emissive excited state is a singlet state (typically the lowermost excited singlet state S1). Fluorescence emitters usually display prompt (i.e. direct) fluorescence on a timescale of nanoseconds, when the initial electronic excitation (for example by electron hole recombination) affords an excited singlet state of the emitter.
In the context of the present invention, a delayed fluorescence material is a material that is capable of reaching an excited singlet state (typically the lowermost excited singlet state S1) by means of reverse intersystem crossing (RISC; in other words: up intersystem crossing or inverse intersystem crossing) from an excited triplet state (typically from the lowermost excited triplet state T1) and that is furthermore capable of emitting light when returning from the so-reached excited singlet state (typically S1) to its electronic ground state. The fluorescence emission observed after RISC from an excited triplet state (typically T1) to the emissive excited singlet state (typically S1) occurs on a timescale (typically in the range of microseconds) that is slower than the timescale on which direct (i.e. prompt) fluorescence occurs (typically in the range of nanoseconds) and is thus referred to as delayed fluorescence (DF). When RISC from an excited triplet state (typically from T1) to an excited singlet state (typically to S1), occurs through thermal activation, and if the so populated excited singlet state emits light (delayed fluorescence emission), the process is referred to as thermally activated delayed fluorescence (TADF). Accordingly, a TADF material is a material that is capable of emitting thermally activated delayed fluorescence (TADF) as explained above. It is known to the person skilled in the art that, when the energy difference ΔEST between the lowermost excited singlet state energy level E(S1) and the lowermost excited triplet state energy level E(T1) of a fluorescence emitter is reduced, population of the lowermost excited singlet state from the lowermost excited triplet state by means of RISC may occur with high efficiency. Thus, it forms part of the common knowledge of those skilled in the art that a TADF material will typically have a small ΔEST value (vide infra).
The occurrence of (thermally activated) delayed fluorescence may for example be analyzed based on the decay curve obtained from time-resolved (i.e. transient) photoluminescence (PL) measurements. PL emission from a TADF material is divided into an emission component from excited singlet states (typically S1) generated by the initial excitation and an emission component from excited states singlet (typically S1) generated via excited triplet states (typically T1) by means of RISC. There is typically a significant difference in time between emission from the singlet excited states (typically S1) formed by the initial excitation and from the singlet excited states (typically S1) reached via RISC from excited triplet states (typically T1).
TADF materials preferably fulfill the following two conditions regarding the full decay dynamics:
In order to evaluate whether the preferred criterion (i) is fulfilled (i.e. the decay dynamics exhibit two time regimes, one typically in the nanosecond (ns) range and the other typically in the microsecond (μs) range), TCSPC (Time-correlated single-photon counting) may typically be used (vide infra) and the full decay dynamics may typically be analyzed as stated below. Alternatively, transient photoluminescence measurements with spectral resolution may be performed (vide infra).
In order to evaluate whether the preferred criterion (ii) is fulfilled (i.e. the shapes of the emission spectra in both time regimes coincide), transient photoluminescence measurements with spectral resolution may typically be performed (vide infra).
Experimental detail on these measurements is provided in a later subchapter of this text.
The ratio of delayed and prompt fluorescence (n-value) may be calculated by the integration of respective photoluminescence decays in time as laid out in a later subchapter of this text.
In the context of the present invention, a TADF material preferably exhibits an n-value (ratio of delayed to prompt fluorescence) larger than 0.05 (n>0.05), more preferably larger than 0.15 (n>0.15), more preferably larger than 0.25 (n>0.25), more preferably larger than 0.35 (n>0.35), more preferably larger than 0.45 (n>0.45), more preferably larger than 0.55 (n>0.55), more preferably larger than 0.65 (n>0.65), more preferably larger than 0.75 (n>0.75), more preferably larger than 0.85 (n>0.85), or even larger than 0.95 (n>0.95).
According to the invention, a thermally activated delayed fluorescence (TADF) material EB is characterized by exhibiting a ΔEST value, which corresponds to the energy difference between the lowermost excited singlet state energy level E(S1E) and the lowermost excited triplet state energy level E(T1E), 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, ΔEST of a TADF material EB according to the invention may be sufficiently small to allow for thermal repopulation of the lowermost excited singlet state S1E from the lowermost excited triplet state T1E (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 EB display both, prompt fluorescence and delayed fluorescence (when the emissive S1E state is reached via thermally activated RISC from the T1E state).
It is understood that a small FWHM emitter SB included in a light-emitting layer B of an organic electroluminescent device according to the invention may optionally also have a ΔEST value of less than 0.4 eV and exhibit thermally activated delayed fluorescence (TADF). However, for any small FWHM emitter SB in 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 EB and the absorption spectrum of at least one small FWHM emitter SB (when both spectra are measured under comparable conditions). In this case, the TADF material EB may transfer energy to the at least one small FWHM emitter SB.
According to the invention, the TADF material EB has an emission maximum in the deep blue wavelength range of from 380 nm to 470 nm, preferably 400 nm to 470 nm, typically measured from a spin-coated film with 10% by weight of the TADF material EB in 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 EB is at a shorter wavelength than the emission maximum (peak emission) of a small FWHM emitter SB in the context of the present invention.
In a preferred embodiment of the invention, each TADF material EB is an organic TADF material, which, in the context of the invention, means that it does not contain any transition metals. Preferably, each TADF material EB according 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 EB has a molecular weight equal to or smaller than 800 g/mol.
In one embodiment of the invention, a TADF emitter EB exhibits a photoluminescence quantum yield (PLQY) equal to or higher than 30%, typically measured from a spin-coated film with 10% by weight of the TADF material EB in poly(methyl methacrylate) PMMA at room temperature (i.e., (approximately) 20° C.).
In a preferred embodiment of the invention, a TADF emitter EB exhibits a photoluminescence quantum yield (PLQY) equal to or higher than 50%, typically measured from a spin-coated film with 10% by weight of the TADF material EB in poly(methyl methacrylate) PMMA at room temperature (i.e., (approximately) 20° C.).
In an even more preferred embodiment of the invention, a TADF emitter EB exhibits a photoluminescence quantum yield (PLQY) equal to or higher than 70%, typically measured from a spin-coated film with 10% by weight of the TADF material EB in poly(methyl methacrylate) PMMA at room temperature (i.e., (approximately) 20° C.).
In one embodiment of the invention, a TADF material EB
In one embodiment of the invention, the energy ELUMO(EB) of the lowest unoccupied molecular orbital LUMO(EB) of each TADF material EB is smaller than −2.6 eV.
It is to be noted that, although being typically capable of emitting fluorescence and (thermally activated) delayed fluorescence, a TADF material EB included in the organic electroluminescent device of the invention preferably mainly functions as “energy pump” and not as emitter material. This is to say that a phosphorescence material PB included in a light-emitting layer B preferably mainly transfers excitation energy to one or more small FWHM emitters SB that in turn serve as the main emitter material(s). The main function of a phosphorescence material PB in a light-emitting layer B is preferably not the emission of light. However, it may emit light to some extent.
The person skilled in the art knows how to design TADF materials (molecules) EB according to the invention and the structural features that such molecules typically display. Briefly, to facilitate the reverse intersystem crossing (RISC), ΔEST is usually decreased and, in the context of the present invention, ΔEST is smaller than 0.4 eV, as stated above. This is oftentimes achieved by designing TADF molecules EB so 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 ΔEST as 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 EB may 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:
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 EB for use according to the present invention, given that the specific materials fulfills the aforementioned basic requirement, namely the ΔEST value 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 EB in 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 EB 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 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 EB in the context of the present invention.
In one embodiment of the invention, each TADF material EB includes 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 EB includes 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 EB includes one or more optionally substituted 1,3,5-triazinyl group.
In one embodiment of the invention, each TADF material EB includes 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 or heteroaromatic, carbo- or heterocyclic ring systems.
In a preferred embodiment of the invention, the at least one, preferably each TADF material EB includes:
In an even more preferred embodiment of the invention, the at least one, preferably each TADF material EB includes:
In a still even more preferred embodiment of the invention, the at least one, preferably each TADF material EB includes:
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, each TADF material EB includes
In a preferred embodiment of the invention,
In an even more preferred embodiment of the invention,
In a still even more preferred embodiment of the invention,
In a still even more preferred embodiment of the invention,
In a still even more preferred embodiment of the invention,
In a still even more preferred embodiment of the invention,
In a particularly preferred embodiment of the invention,
In a preferred embodiment of the invention, a is always 1 and b is always 0.
In a preferred embodiment of the invention, Z2 is at each occurrence a direct bond.
In a preferred embodiment of the invention, Ra is at each occurrence hydrogen.
In a preferred embodiment of the invention, Ra and Rd are at each occurrence hydrogen.
In a preferred embodiment of the invention, Q3 is at each occurrence nitrogen (N).
In one embodiment of the invention, at least one group RX in formula EWG-I is CN.
In a preferred embodiment of the invention, exactly one group RX in formula EWG-I is CN.
In a preferred embodiment of the invention, exactly one group RX in formula EWG-I is CN and no group RX in 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:
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:
In a preferred embodiment of the invention, each TADF material EB has a structure represented by any of formulas EB-I, EB-II, EB-III, EB-IV, EB-V, EB-VI, EB-VII, EB-VIII, and EB-IX, EB-X, and EB-XI:
In a preferred embodiment of the invention, R13 is at each occurrence hydrogen.
In one embodiment of the invention, RY is at each occurrence CN.
In one embodiment of the invention, RY is at each occurrence CF3.
In one embodiment of the invention, RY is at each occurrence a structure represented by formula BN-I.
In a preferred embodiment of the invention, RY is 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 EB has a structure represented by any of formulas EB-I, EB-II, EB-III, EB-IV, EB-V, EB-VI, EB-VII, and EB-X, wherein the aforementioned definitions apply.
In a preferred embodiment of the invention, each TADF material EB has a structure represented by any of formulas EB-I, EB-II, EB-III, EB-V, and EB-X, wherein the aforementioned definitions apply.
Examples of TADF materials EB for 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 EB in the context of the present invention.
Non-limiting examples of TADF materials EB according formula EB-I are shown below:
Non-limiting examples of TADF materials EB according formula EB-II are shown below:
Non-limiting examples of TADF materials EB according formula EB-III are shown below:
Non-limiting examples of TADF materials EB according formula EB-IV are shown below:
Non-limiting examples of TADF materials EB according formula EB-V are shown below:
Non-limiting examples of TADF materials EB according formula EB-VI are shown below:
Non-limiting examples of TADF materials EB according formula EB-VII are shown below:
Non-limiting examples of TADF materials EB according formula EB-VIII are shown below:
Non-limiting examples of TADF materials EB according formula EB-IX are shown below:
Non-limiting examples of TADF materials EB according formula EB-X are shown below:
Non-limiting examples of TADF materials EB according formula EB-XI are shown below:
The synthesis of TADF materials EB can 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 EB according to any of formulas EB-III, EB-IV, and EB-V:
E1 can be any boronic acid (RB=H) or an equivalent boronic acid ester (RB=alkyl or aryl), in particular two RB may 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 C1, 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:
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.
In particular, the donor molecule E4 may be 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 for example the corresponding carbazolyl-boronic acid or ester such as a 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 Ra, Rb or Rd may 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. Ra-Hal, preferably Ra—Cl and Ra—Br.
Alternatively, one or more substituents Ra, Rb or Rd may 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 Ra [Ra—B(OH)2], Rb [Rb—B(OH)2] or Rd [Rd—B(OH)2] or a corresponding boronic acid ester.
Further TADF materials EB may be obtained analogously. A TADF material EB may 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) PB
The phosphorescence materials PB in 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 (i.e. excited triplet states, typically the lowermost excited triplet state T1). This is to say that a phosphorescence material PB is capable of emitting phosphorescence at room temperature (i.e. (approximately) 20° C., which is typically measured from a spin-coated film of the respective PB in poly(methyl methacrylate) (PMMA) with a concentration of 10% by weight of PB.
It is to be noted that, although being per definition capable of emitting phosphorescence, a phosphorescence material PB optionally included in the organic electroluminescent device of the invention as optional excitation energy transfer component EET-2 preferably mainly functions as “energy pump” and not as emitter material. This is to say that a phosphorescence material PB included in a light-emitting layer B preferably mainly transfers excitation energy to one or more small FWHM emitters SB that in turn serve as the main emitter material(s). The main function of a phosphorescence material PB in a light-emitting layer B is preferably not the emission of light. However, it may emit light to some extent.
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 PB used in organic electroluminescent devices are oftentimes complexes of Ir, Pd, Pt, 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 PB in 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.
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 PB in the context of the present invention.
In one embodiment of the invention, each phosphorescence material PB included in a light-emitting layer B includes Iridium (Ir).
In one embodiment of the invention, at least one phosphorescence material PB, preferably each phosphorescence material PB included in a light-emitting layer B, is an organometallic complex including either iridium (Ir) or platinum (Pt).
In one embodiment of the invention, the at least one phosphorescence material PB, preferably each phosphorescence material PB, included in a light-emitting layer B is an organometallic complex including iridium (Ir).
In one embodiment of the invention, the at least one phosphorescence material PB, preferably each phosphorescence material PB, included in a light-emitting layer B is an organometallic complex including platinum (Pt).
Non-limiting examples of phosphorescence materials PB also include compounds represented by the following general formula PB-I,
In formula PB-I, M is selected from the group consisting of Ir, Pt, Pd, Au, Eu, Ru, Re, Ag and Cu;
In one embodiment of the invention, each phosphorescence materials PB included in a light-emitting layer B includes or consists of a structure according to formula PB-I,
Examples of the compounds represented by the formula PB-I include compounds represented by the following general formula PBII or general formula PB-III:
In formulas PB-II and PB-III, X′ is 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 PB-III, Z3 is a bidentate ligand having two oxygens (O). In the formulas PB-II and PB-III, M is preferably Ir from the viewpoint of high efficiency and long lifetime.
In the formulas PB-II and PB-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 RE.
In the formulas PB-II and PB-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 RE. Furthermore, Y′ may be, for example, a C1-C5-heteroaryl, which is optionally substituted with one or more substituents RE.
In the formulas PB-II and PB-III, the bidentate ligand having two oxygens (O) Z3 is 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 Z3 at each occurrence is optionally substituted with one or more substituents RE. Furthermore, Z3 may be, for example, a C2-C5-bidentate ligand having two oxygens, which is optionally substituted with one or more substituents RE.
RE is at each occurrence independently from another selected from the group consisting of hydrogen, deuterium, N(R5E)2, OR5E,
R5E is at each occurrence independently from another selected from the group consisting of hydrogen, deuterium, N(R6E)2, OR6E, SR6E, Si(R6E)3, CF3, CN, F,
R6E is at each occurrence independently from another selected from the group consisting of hydrogen, deuterium, OPh, CF3, CN, F,
The substituents RE, R5E, or R6E independently from each other optionally may form a mono- or polycyclic, aliphatic, aromatic, heteroaromatic ring system with one or more substituents RE, R5E, R6E, and/or with X′, Y′ and Z3.
Non-limiting examples of the compound represented by formula PB-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 non-limiting examples of the compound represented by formula PB-II include compounds represented by the following formulas PB-II-1 to PB-II-11. In the structural formula, “Me” represents a methyl group.
Other non-limiting examples of the compound represented by the formula PB-III include compounds represented by the following formulas PB-III-1 to PB-III-6. In the structural formula, “Me” represents a methyl group.
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)3 and Hex-Ir(ppy)3 are often used for green light emission.
Exciplexes
It has been stated that TADF materials are capable of converting excited triplet states (preferably T1) to excited singlet states (preferably S1) by means of reverse intersystem crossing (RISC). It has also been stated that this typically requires a small ΔEST value, which is smaller than 0.4 eV for TADF materials EB by definition.
As also stated, this is oftentimes achieved by designing TADF molecules EB so that the HOMO and LUMO are spatially largely separated on (electron-) donor and (electron-) acceptor groups, respectively. However, another strategy to arrive at species that have small ΔEST values is the formation of exciplexes. As known to the skilled artisan an exciplex is an excited state charge transfer complex formed between a donor molecule and an acceptor molecule (i.e. an excited state donor-acceptor complexes). The person skilled in the art further understands that the spatial separation between the HOMO (on the donor molecule) and the LUMO (on the acceptor molecule) in exciplexes typically results in them having rather small ΔEST values and being oftentimes capable of converting excited triplet states (preferably T1) to excited singlet states (preferably S1) by means of reverse intersystem crossing (RISC).
Indeed, as known to the person skilled in the art, a TADF material may not just be a material that is on its own capable of RISC from an excited triplet state to an excited singlet state with subsequent emission of TADF as laid out above. It is known to those skilled in the art that a TADF material may in fact also be an exciplex that is formed from two kinds of materials, preferably from two host materials HB, more preferably from a p-host material HP and an n-host material HN (vide infra), whereat it is understood that the host materials HB (typically HP and HN) may themselves be TADF materials.
The person skilled in the art understands that any materials that are included in the same layer, in particular in the same EML, but also materials that are in adjacent layers and get in close proximity at the interface between these adjacent layers, may together form an exciplex. The person skilled in the art knows how to choose pairs of materials, in particular pairs of a p-host HP and an n-host HN, which form an exciplex and the selection criteria for the two components of said pair of materials, including HOMO- and/or LUMO-energy level requirements. This is to say that, in case exciplex formation may be aspired, the highest occupied molecular orbital (HOMO) of the one component, e.g. the p-host material HP, may be at least 0.20 eV higher in energy than the HOMO of the other component, e.g. the n-host material HN, and the lowest unoccupied molecular orbital (LUMO) of the one component, e.g. the p-host material HP, may be at least 0.20 eV higher in energy than the LUMO of the other component, e.g. the n-host material HN.
It belongs to the common knowledge of those skilled in the art that, if present in an EML of an organic electroluminescent device, in particular an OLED, an exciplex may have the function of an emitter material and emit light when a voltage and electrical current are applied to said device. As also commonly known from the state of the art, an exciplex may also be non-emissive and may for example transfer excitation energy to an emitter material, if included in an EML of an organic electroluminescent device.
Non-limiting examples of host materials HB that may together form an exciplex are listed below, wherein the donor molecule (i.e. the p-host HP) may be selected from the following structures:
and wherein the acceptor molecule (i.e. the n-host HN) may be selected from the following structures:
It is understood that exciplexes may be formed from any materials included in a light-emitting layer B in the context of the present invention, for example from different excitation energy transfer components (EB and/or EET-2) as well as from an excitation energy transfer component (EB and/or EET-2) and a small FWHM emitter SB or from a host material HB and an excitation energy transfer component EB or EET2 or a small FWHM emitter SB. Preferably however, they are formed from different host materials HB as stated above. It is also understood that an exciplex may also be formed and not serve as excitation energy transfer component itself.
Small FWHM Emitter(s) SB
A small full width at half maximum (FWHM) emitter SB in 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 SB may be measured in a solution, typically with 0.001-0.2 mg/mL of the emitter SB in dichloromethane or toluene at room temperature (i.e., (approximately) 20° C.).
In a preferred embodiment of the invention, a small FWHM emitter SB is 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 SB in PMMA at room temperature (i.e., (approximately) 20° C.). Alternatively, emission spectra of small FWHM emitters SB may be measured in a solution, typically with 0.001-0.2 mg/mL of the emitter SB in dichloromethane or toluene at room temperature (i.e., (approximately) 20° C.). In other embodiments of the present invention, each small FWHM emitter SB exhibits 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 SB emits light with an emission maximum in the wavelength range of from 440 nm to 480 nm, measured (with 1 to 5% by weight, in particular with 2% by weight of the emitter SB) in PMMA at room temperature.
In one embodiment of the invention, each small FWHM emitter SB emits light with an emission maximum in the wavelength range of from 440 nm to 480 nm, measured with 0.001-0.2 mg/mL of the emitter SB in dichloromethane or toluene at room temperature (i.e., (approximately) 20° C.).
It is understood that a TADF material EB included 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 EB included 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: 440 nm to 480 nm).
In one embodiment of the invention, the relation expressed by the following formula (29) applies:
440 nm≤λmax(SB)≤480 nm (29),
wherein λmax(SB) refers to the emission maximum of a small FWHM emitter SB in the context of the present invention.
In one embodiment, the aforementioned relation expressed by formula (29) applies to materials included the light-emitting layers B of the organic electroluminescent device according to the invention.
In a preferred embodiment of the invention, the small FWHM emitter SB is an organic emitter, which, in the context of the invention, means that it does not contain any transition metals. Preferably, the small FWHM emitter SB according 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, the small FWHM emitter SB is 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 SB exhibits 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 SB) in PMMA at room temperature.
In a preferred embodiment of the invention, a small FWHM emitter SB exhibits 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 SB) in PMMA at room temperature.
In an even more preferred embodiment of the invention, a small FWHM emitter SB exhibits 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 SB) in PMMA at room temperature.
In a still even more preferred embodiment of the invention, a small FWHM emitter SB exhibits 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 SB) in PMMA at room temperature.
In a particularly preferred embodiment of the invention, a small FWHM emitter SB exhibits 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 SB) in PMMA at room temperature.
In one embodiment of the invention, a small FWHM emitter SB exhibits a photoluminescence quantum yield (PLQY) equal to or higher than 50%, measured with 0.001-0.2 mg/mL of the emitter SB in dichloromethane or toluene at room temperature (i.e., (approximately) 20° C.).
In a preferred embodiment of the invention, a small FWHM emitter SB exhibits a photoluminescence quantum yield (PLQY) equal to or higher than 60%, measured with 0.001-0.2 mg/mL of the emitter SB in dichloromethane or toluene at room temperature (i.e., (approximately) 20° C.).
In an even more preferred embodiment of the invention, a small FWHM emitter SB exhibits a photoluminescence quantum yield (PLQY) equal to or higher than 70%, measured with 0.001-0.2 mg/mL of the emitter SB in 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 SB exhibits a photoluminescence quantum yield (PLQY) equal to or higher than 80%, measured with 0.001-0.2 mg/mL of the emitter SB in dichloromethane or toluene at room temperature (i.e., (approximately) 20° C.).
In a particularly preferred embodiment of the invention, a small FWHM emitter SB exhibits a photoluminescence quantum yield (PLQY) equal to or higher than 90%, measured with 0.001-0.2 mg/mL of the emitter SB in dichloromethane or toluene at room temperature (i.e., (approximately) 20° C.).
The person skilled in the art knows how to design small FWHM emitters SB which fulfill the above-mentioned requirements or preferred features.
Another class of molecules suitable to provide small FWHM emitters SB in 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 SB in the context of the present invention. For example, the emitters disclosed in EP3109253 (A1) may be used as small FWHM emitters SB in 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 SB for use according to the present invention.
A group of emitters that may be used as small FWHM emitters SB in 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:
wherein in case, one of Ya and Yb is or both of Ya and Yb are NRDABNA-3, C(RDABNA-3)2, Si(RDABNA-3)2, or BRDABNA-3 the one or the two substituents RDABNA-3 may optionally and independently of each other bond to one or both of the adjacent rings A′ and B′ (for Ya=NRDABNA-3, C(RDABNA-3)2, Si(RDABNA-3)2, or BRDABNA-3) or A′ and C′ (for Yb=NRDABNA-3, C(RDABNA-3)2, Si(RDABNA-3)2, or BRDABNA-3) via a direct (single) bond or via a connecting atom or atom group being in each case independently selected from NRDABNA-1, O, S, C(RDABNA-1)2, Si(RDABNA-1)2, BRDABNA-1, and Se;
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 SB includes 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 SB includes 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 SB consists 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 SB consists 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 SB includes 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 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 SB includes or consists of a structure according to formula DABNA-I, Ya and Yb are independently of each other selected from NRDABNA-3, O, S, C(RDABNA-3)2, and Si(RDABNA-3)2.
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 SB includes or consists of a structure according to formula DABNA-I, Ya and Yb are independently of each other selected from NRDABNA-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 SB includes or consists of a structure according to formula DABNA-I, Ya and Yb are independently of each other selected from NRDABNA-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 SB includes or consists of a structure according to formula DABNA-I, Ya and Yb are both NRDABNA-3.
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 SB includes or consists of a structure according to formula DABNA-I, Ya and Yb are identical and are both NRDABNA-3.
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 SB includes or consists of a structure according to formula DABNA-I,
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 SB includes or consists of a structure according to formula DABNA-I,
which is optionally substituted with one or more substituents RDABNA-2;
RDABNA-2 is at each occurrence independently of each other selected from the group consisting of: hydrogen, deuterium, N(RDABNA-6)2, ORDABNA-6, SRDABNA-6, Si(RDABNA-6)3, CF3, CN, F,
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 SB includes or consists of a structure according to formula DABNA-I,
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 SB includes or consists of a structure according to formula DABNA-I,
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 SB includes or consists of a structure according to formula DABNA-I,
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 SB includes or consists of a structure according to formula DABNA-I, adjacent substituents selected from RDABNA-1 and RDABNA-2 do 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′.
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 SB includes or consists of a structure according to formula DABNA-I,
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 SB includes or consists of a structure according to formula DABNA-I,
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 SB includes or consists of a structure according to formula DABNA-I,
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 SB includes or consists of a structure according to formula DABNA-I,
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 SB includes or consists of a structure according to formula DABNA-I,
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 SB includes or consists of a structure according to formula DABNA-I,
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 SB includes or consists of a structure according to formula DABNA-I,
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 SB includes or consists of a structure according to formula DABNA-I,
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 SB includes or consists of a structure according to formula DABNA-I,
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 SB includes or consists of a structure according to formula DABNA-I, when Ya and/or Yb is/are NRDABNA-3, C(RDABNA-3)2, Si(RDABNA-3)2, or BRDABNA-3, the one or the two substituents RDABNA-3 do not bond to one or both of the adjacent rings A′ and B′ (for Ya=NRDABNA-3, C(RDABNA-3)2, Si(RDABNA-3)2, or BRDABNA-3) or A′ and C′ (for Yb=NRDABNA-3, C(RDABNA-3)2, Si(RDABNA-3)2, or BRDABNA-3).
In one embodiment, small FWHM emitters SB in 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 SB may 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 SB may 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 SB, 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 SB includes 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 RDABNA-1, RDABNA-2, RDABNA-3, RDABNA-4, RDABNA-5, and RDABNA-6, in particular RDABNA-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).
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 SB includes or consists of two or more, preferably of exactly two, structures according to formula DABNA-I (i.e. subunits),
Non-limiting examples of emitters including or consisting of a structure according to formula DABNA-I that may be used as small FWHM emitters SB according to the present invention are listed below.
A group of emitters that may be used as small FWHM emitter SB in the context of the present invention are emitters including or consisting of a structure according to the following formula BNE-1:
In one embodiment of the invention, in the light-emitting layer B, the small FWHM emitters SB includes a structure according to formula BNE-1.
In one embodiment of the invention, the one small FWHM emitters SB includes or consists of a structure according to formula BNE-1, V1 is CRBNE-v and V2 is CRBNE-I.
In one embodiment of the invention, the small FWHM emitter SB includes or consists of a structure according to formula BNE-1, V1 and V2 are both nitrogen (N).
In one embodiment of the invention, the small FWHM emitter SB includes or consists of a structure according to formula BNE-1, V1 is nitrogen (N) and V2 is CRBNE-I.
In one embodiment of the invention, the small FWHM emitter SB includes or consists of a structure according to formula BNE-1, V1 is CRBNE-v and V2 is nitrogen (N).
In one embodiment of the invention, the small FWHM emitter SB includes or consists of a structure according to formula BNE-1, c and d are both 0.
In one embodiment of the invention, the small FWHM emitter SB includes or consists of a structure according to formula BNE-1, c is 0 and d is 1.
In one embodiment of the invention, the small FWHM emitter SB includes or consists of a structure according to formula BNE-1, c is 1 and d is 0.
In one embodiment of the invention, the small FWHM emitter SB includes or consists of a structure according to formula BNE-1, c and d are both 1.
In one embodiment of the invention, the small FWHM emitter SB includes or consists of a structure according to formula BNE-1,
In one embodiment of the invention, the small FWHM emitter SB includes or consists of a structure according to formula BNE-1,
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 SB includes or consists of a structure according to formula BNE-1,
In one embodiment of the invention, the small FWHM emitter SB includes or consists of a structure according to formula BNE-1,
In one embodiment of the invention, the small FWHM emitter SB includes or consists of a structure according to formula BNE-1,
In one embodiment of the invention, the small FWHM emitter SB includes or consists of a structure according to formula BNE-1,
In one embodiment of the invention, the small FWHM emitter SB includes or consists of a structure according to formula BNE-1,
In one embodiment of the invention, the small FWHM emitter SB includes or consists of a structure according to formula BNE-1,
In one embodiment of the invention, the small FWHM emitter SB includes or consists of a structure according to formula BNE-1,
In one embodiment of the invention, the small FWHM emitter SB includes or consists of a structure according to formula BNE-1, RBNE-III and RBNE-e combine to form a direct single bond.
In one embodiment of the invention, the small FWHM emitter SB includes or consists of a structure according to formula BNE-1, RBNE-III and RBNE-e do not combine to form a direct single bond.
In one embodiment, fluorescent emitters suitable as small FWHM emitters SB in the context of the present invention may optionally also be multimers (e.g. dimers) of the aforementioned formula BNE-1, which means that their structure includes more than one subunits, each of which has a structure according to formula BNE-1. In this case, the skilled artisan will understand that the two or more subunits according to formula BNE-1 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 SB may include two or more subunits each having a structure of formula BNE-1, 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 SB may not contain two whole subunits according to formula BNE-1 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 BNE-1 are included) of formula BNE-1. 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 BNE-1.
In one embodiment of the invention, the small FWHM emitter SB is a dimer of formula BNE-1 as described above, which means that the emitter includes two subunits, each having a structure according to formula BNE-1.
In one embodiment of the invention, the small FWHM emitter SB is a dimer of formula BNE-1 as described above, which means that the emitter includes two subunits, each having a structure according to formula BNE-1 (i.e. subunits),
In one embodiment of the invention, the small FWHM emitter SB is a dimer of formula BNE-1 as described above, which means that the emitter includes two subunits, each having a structure according to formula BNE-1 (i.e. subunits),
In one embodiment of the invention, the small FWHM emitter SB is a dimer of formula BNE-1 as described above, which means that the emitter includes two subunits, each having a structure according to formula BNE-1 (i.e. subunits),
Non-limiting examples of fluorescent emitters including or consisting of a structure according to the aforementioned formula BNE-1 that may be used as small FWHM emitters in the context of the present invention are shown below:
The synthesis of small FWHM emitters SB including or consisting of a structure according to formula BNE-1 can be accomplished via standard reactions and reaction conditions known to the skilled artisan.
Typically, the synthesis includes transition-metal catalyzed cross coupling reactions and a borylation reaction, all of which are known to the skilled artisan.
For example, WO2020135953 (A1) teaches how to synthesize small FWHM emitters SB including or consisting of a structure according to formula BNE-1. Furthermore, US2018047912 (A1) teaches how to synthesize small FWHM emitters SB including or consisting of a structure according to formula BNE-1, in particular with c and d being 0.
It is understood that the emitters disclosed in US2018047912 (A1) and WO2020135953 (A1) may also be used as small FWHM emitters SB in the context of the present invention.
In one embodiment of the invention, in at least one, preferably each, light-emitting layer B, at least one, preferably each, small FWHM emitter SB includes or consists of a structure according to either formula DABNA-I or formula BNE-1. The person skilled in the art understands this to mean that if more than one small FWHM emitters SB are present in a light-emitting layer B, they may all include or consist of a structure according to formula DABNA-I or all include or consist of a structure according to formula BNE-1 or some may include or consist of a structure according to formula DABNA-I, while others include or consist of a structure according to formula BNE-1.
One approach to design fluorescent emitters relies on the use of fluorescent polycyclic aromatic or heteroaromatic core structures. The latter are, in the context of the present invention, any structures including more than one aromatic or heteroaromatic ring, preferably more than two such rings, which are, even more preferably, fused to each other or linked via more than one direct bond or linking atom. In other words, the fluorescent core structures include at least one, preferably only one, rigid conjugated π-system.
The skilled artisan knows how to select a core structure for a fluorescent emitter, for example from US2017077418 (A1). Examples of common core structures of fluorescent emitters are listed below, wherein this does not imply that only these cores may provide small FWHM emitters SB suitable for the use according to the present invention:
The term fluorescent core structure in this context indicates that any molecule including the core may potentially be used as fluorescent emitter. The person skilled in the art knows that the core structure of such a fluorescent emitter may be optionally substituted and which substituents are suitable in this regard, for example from: US2017077418 (A1), M. Zhu. C. Yang, Chemical Society Reviews 2013, 42, 4963, DOI: 10.1039/c3cs35440g; S. Kima, B. Kimb, J. Leea, H. Shina, Y.-II Parkb, J. Park, Materials Science and Engineering R: Reports 2016, 99, 1, DOI: 10.1016/j.mser.2015.11.001; K. R. J. Thomas, N. Kapoor, M. N. K. P. Bolisetty, J.-H. Jou, Y.-L. Chen, Y.-C. Jou, The Journal of Organic Chemistry 2012, 77(8), 3921, DOI: 10.1021/jo300285v; M. Vanga, R. A. Lalancette, F. Jskle, Chemistry—A European Journal 2019, 25(43), 10133, DOI: 10.1002/chem.201901231.
Small FWHM emitters SB for use according to the present invention may be obtained from the aforementioned fluorescent core structures, for example, by attaching sterically demanding substituents to the core that hinder the contact between the fluorescent core and adjacent molecules in the respective layer of an organic electroluminescent device.
In the context of the present invention, a compound, for example a fluorescent emitter is considered to be sterically shielded, when a subsequently defined shielding parameter is equal to or below a certain limit which is also defined in a later subchapter of this text.
It is preferred that the substituents used to sterically shield a fluorescent emitter are not just bulky (i.e. sterically demanding), but also electronically inert, which in the context of the present invention means, that these substituents do not include an active atom as defined in a later subchapter of this text. It is understood that this does not imply that only electronically inert (in other words: not active) substituents may be attached to a fluorescent core structure such as the ones shown above. Active substituents may also be attached to the core structure and may be introduced on purpose to tune the photophysical properties of a fluorescent core structure. In this case, it is preferred, that the active atoms introduced via one or more substituents are again shielded by electronically inert (i.e. not active) substituents.
Based on the aforementioned information and common knowledge from the state of the art, the skilled artisan understands how to choose substituents for a fluorescent core structure that may induce steric shielding of the latter and that are electronically inert as stated above. In particular, US2017077418 (A1) discloses substituents suitable as electronically inert (in other words: not active) shielding substituents. Examples of such substituents include linear, branched or cyclic alkyl groups with 3 to 40 carbon atoms, preferably 3 to 20 carbon atoms, more preferably with 4 to 10 carbon atoms, wherein one or more hydrogen atoms may be replaced by a substituent, preferably by deuterium or fluorine. Other examples include alkoxy groups with 3 to 40 carbon atoms, preferably 3 to 20 carbon atoms, more preferably with 4 to 10 carbon atoms, wherein one or more hydrogen atoms may be replaced by a substituent, preferably by deuterium or fluorine. It is understood that these alkyl and alkoxy substituents may be substituted by substituents other than deuterium and fluorine, for example by aryl groups. In this case, it is preferred that the aryl group as substituent includes 6 to 30 aromatic ring atoms, more preferably 6 to 18 aromatic ring atoms, most preferably 6 aromatic ring atoms, and is preferably not a fused aromatic system such as anthracene, pyrene and the like. Other examples include aryl groups with 6 to 30 aromatic ring atoms, more preferably with 6 to 24 aromatic ring atoms. One or more hydrogen atom in these aryl substituents may be substituted and preferred substituents are for example aryl groups with 6 to 30 carbon atoms and linear, branched or cyclic alkyl groups with 1 to 20 carbon atoms. All substituents may be further substituted. It is understood that all sterically demanding and preferably also electronically inert (in other words: not active) substituents disclosed in US2017077418 (A1) may serve to sterically shield a fluorescent core (such as those described above) to afford sterically shielded fluorescent emitters suitable as small FWHM emitters SB for use according to the present invention.
Below, non-limiting examples of substituents are shown that may be used as sterically demanding (i.e. shielding) and electronically inert (i.e. not active) substituents in the context of the present invention (disclosed in US2017077418 (A1)):
It is also understood that a fluorescent core may not just bear such sterically shielding substituents, but may also be substituted by further, non-shielding substituents that may or may not be active groups in the context of the present invention (see below for a definition).
Below, examples of sterically shielded fluorescent emitters are shown that may be used as small FWHM emitters SB in the context of the present invention. This does not imply that the present invention is limited to organic electroluminescent devices including the shown emitters.
It is understood that sterically shielding substituents (that may or may not be electronically inert as stated above) may be attached to any fluorescent molecules, for example to the aforementioned polycyclic aromatic or heteroaromatic fluorescent cores, the BODIPY-derived structures and the NRCT emitters shown herein and to emitters including a structure of formula BNE-1. This may result in sterically shielded fluorescent emitters that may be suitable as small FWHM emitters SB according to the invention.
In one embodiment of the invention, within the light-emitting layer B, the small FWHM emitter SB fulfills at least one of the following requirements:
In one embodiment of the invention, the small FWHM emitter SB is a boron (B)-containing emitter, which means that at least one atom within each small FWHM emitter SB is boron (B).
In one embodiment of the invention, the small FWHM emitter SB includes a polycyclic aromatic or heteroaromatic core structure, wherein at least two aromatic rings are fused together (e.g. anthracene, pyrene or aza-derivatives thereof).
In one embodiment of the invention, within the light-emitting layer B, the small FWHM emitter SB fulfills at least one (or both) of the following requirements:
In one embodiment of the invention, the small FWHM emitter SB includes a pyrene core structure.
In a preferred embodiment of the invention, in the light-emitting layer B, the small FWHM emitter SB is a boron (B)- and nitrogen (N)-containing emitter, which means that at least one atom within each small FWHM emitter SB is boron (B) and at least one atom within each small FWHM emitter SB is nitrogen (N).
In a preferred embodiment of the invention, in the light-emitting layer B, the small FWHM emitter SB includes at least one boron atom (B)— that is (directly) covalently bonded to at least one nitrogen atom (N).
In a preferred embodiment of the invention, in the light-emitting layer B, the small FWHM emitter SB includes a boron atom (B) that is trivalent, i.e. bonded via three single bonds.
Steric Shielding
Determination of the Shielding Parameter A
The shielding parameter A of a molecule can be determined as exemplarily described in the following for (fluorescent) emitters, such as those mentioned above. It will be understood that the shielding parameter A typically refers to the unit Ångstrom (Å2). This does not imply that only such compounds may be sterically shielded in the context of the present invention, nor that a shielding parameter can only be determined for such compounds.
Determination of the Energy Levels of the Molecular Orbitals
The energy levels of the molecular orbitals may be determined via quantum chemical calculations. For this purpose, in the present case, the Turbomole software package (Turbomole GmbH), version 7.2, may be used. First, a geometry optimization of the ground state of the molecule may be performed using density functional theory (DFT), employing the def2-SV(P) basis set and the BP-86 functional. Subsequently, on the basis of the optimized geometry, a single-point energy calculation for the electronic ground state may be performed employing the B3-LYP functional. From the energy calculation, the highest occupied molecular orbital (HOMO), for example, may be obtained as the highest-energy orbital occupied by two electrons, and the lowest unoccupied molecular orbital (LUMO) as the lowest-energy unoccupied orbital. The energy levels may be obtained in an analogous manner for the other molecular orbitals such as HOMO−1, HOMO−2, . . . LUMO+1, LUMO+2 etc.
The method described herein is independent of the software package used. Examples of other frequently utilized programs for this purpose may be “Gaussian09” (Gaussian Inc.) and Q-Chem 4.1 (Q-Chem, Inc.).
Charge-Exchanging Molecular Orbitals of the (Fluorescent) Compound
Charge-exchanging molecular orbitals of the (fluorescent) compound may be considered to be the HOMO and LUMO, and all molecular orbitals that may be separated in energy by 75 meV or less from the HOMO or LUMO.
Determination of the Active Atoms of a Molecular Orbital
For each charge-exchanging molecular orbital, a determination of which atoms may be active may be conducted. In other words, a generally different set of active atoms may be found for each molecular orbital. There follows a description of how the active atoms of the HOMO may be determined. For all other charge-exchanging molecular orbitals (e.g. HOMO-1, LUMO, LUMO+1, etc.), the active atoms may be determined analogously.
The HOMO may be calculated as described above. To determine the active atoms, the surface on which the orbital has an absolute value of 0.035 (“isosurface with cutoff 0.035”) is inspected. For this purpose, in the present case, the Jmol software (http://jmol.sourceforge.net/), version 14.6.4, is used. Atoms around which orbital lobes with values equal to or larger than the cutoff value may be localized may be considered active. Atoms around which no orbital lobes with values equal to or larger than the cutoff value may be localized may be considered inactive.
4. Determination of the Active Atoms in the (Fluorescent) Compound
If one atom is active in at least one charge-exchanging molecular orbital, it may be considered to be active in respect of the (fluorescent) compound. Only atoms that may be inactive (non-active) in all charge-exchanging molecular orbitals may be inactive in respect of the (fluorescent) compound.
5. Determination of the Shielding Parameter A
In a first step, the solvent accessible surface area SASA may be determined for all active atoms according to the method described in B. Lee, F. M. Richards, Journal of Molecular Biology 1971, 55(3), 379, DOI: 10.1016/0022-2836(71)90324-X. For this purpose, the van-der-Waals surface of the atoms of a molecule may be considered to be impenetrable. The SASA of the entire molecule may be then defined as the area of the surface which may be traced by the center of a hard sphere (also called probe) with radius r (the so-called probe radius) while it may be rolled over all accessible points in space at which its surface may be in direct contact with the van-der-Waals surface of the molecule. The SASA value can also be determined for a subset of the atoms of a molecule. In that case, only the surface traced by the center of the probe at points where the surface of the probe may be in contact with the van-der-Waals surface of the atoms that may be part of the subset may be considered. The Lee-Richards algorithm used to determine the SASA for the present purpose may be part of the program package Free SASA (S. Mitternacht, Free SASA: An open source C library for solvent accessible surface area calculations. F1000Res. 2016; 5:189. Published 2016 Feb. 18. doi:10.12688/f1000research.7931.1). The van-der-Waals radii rvDwof the relevant elements may be compiled in the following reference: M. Mantina, A. C. Chamberlin, R. Valero, C. J. Cramer, D. G. Truhlar, The Journal of Physical Chemistry A 2009, 113(19), 5806, DOI: 10.1021/jp8111556. The probe radius r may be set to be 4 Å (r=4 Å) for all SASA determinations for the present purpose.
In the context of the present invention, the shielding parameter A may be obtained by dividing the solvent accessible surface area of the subset of active atoms (labeled S to distinguish from the SASA of the entire molecule) by the number n of active atoms:
A=S/n
In the context of the present invention, a compound may be defined as sterically well-shielded if the shielding parameter A has a value below 2 Å2 (A<2.0 Å2).
In the context of the present invention, a compound may be defined as sterically shielded if the shielding parameter A has a value of 1.0 to 5.0 Å2 (1.0 Å2≤A≤5.0 Å2), preferably 2.0 Å2 to 5.0 Å2 (2.0 Å2≤A≤5.0 Å2).
Below, exemplary (fluorescent) emitters are shown, alongside their shielding parameters A, which were determined as stated above. It will be understood that this does not imply that the present invention is limited to organic electroluminescent devices including one of the shown emitters. The depicted emitter compounds are merely non-limiting examples that represent optional embodiments of the invention.
In one embodiment of the invention, each small FWHM emitter SB included in an organic electroluminescent device according to the invention exhibits a shielding parameter A equal to or smaller than 5.0 Å2.
In one embodiment, in at least one, preferably each, light-emitting layer B of the organic electroluminescent device according to the present invention, at least one, preferably each, small FWHM emitter SB exhibits a shielding parameter A equal to or smaller than 5.0 Å2.
In a preferred embodiment of the invention, each small FWHM emitter SB included in an organic electroluminescent device according to the invention exhibits a shielding parameter A equal to or smaller than 2.0 Å2.
In one embodiment, in at least one, preferably each, light-emitting layer B of the organic electroluminescent device according to the present invention, at least one, preferably each, small FWHM emitter SB exhibits a shielding parameter A equal to or smaller than 2.0 Å2.
The person skilled in the art understands that not only a fluorescent emitter such as a small FWHM emitter SB according to the present invention may be sterically shielded by attaching shielding substituents. It is understood that for example also a TADF material EB in the context of the present invention and also a phosphorescence material PB in the context of the present invention may be shielded.
Excited State Lifetimes
A detailed description on how the excited state lifetimes are measured is provided in a following subchapter of this text.
In one embodiment of the invention, in the light-emitting layer B, at least one, preferably each, TADF material EB in the context of the present invention exhibits a delayed fluorescence lifetime
In one embodiment of the invention, in the light-emitting layer B, at least one, preferably each, TADF material EB in the context of the present invention exhibits a delayed fluorescence lifetime
In one embodiment of the invention, in the light-emitting layer B, at least one, preferably each, TADF material EB in the context of the present invention exhibits an a delayed fluorescence lifetime
In a preferred embodiment of the invention, in the light-emitting layer B, at least one, preferably each, TADF material EB in the context of the present invention exhibits a delayed fluorescence lifetime
In an even more preferred embodiment of the invention, in the light-emitting layer B, at least one, preferably each, TADF material EB in the context of the present invention exhibits a delayed fluorescence lifetime
In one embodiment of the invention, in the light-emitting layer B, the phosphorescence material PB in the context of the present invention exhibits an excited state lifetime
In a preferred embodiment of the invention, in the light-emitting layer B, the phosphorescence material PB in the context of the present invention exhibits an excited state lifetime
In an even more preferred embodiment of the invention, in the light-emitting layer B, the phosphorescence material PB in the context of the present invention exhibits an excited state lifetime
In one embodiment of the invention, in an organic electroluminescent device according to the invention, the addition of one or more TADF materials EB into the light-emitting layer B including a phosphorescence material PB, a small FWHM emitters SB and a host material HB, results in a decreased excited state lifetime of the organic electroluminescent device. In a preferred embodiment of the invention, the aforementioned addition of a TADF material EB according to the invention decreases the excited state lifetime of the organic electroluminescent device by at least 50%.
As used throughout, the term “layer” in the context of the present invention preferably refers to a body that bears an extensively planar geometry. It is understood that the same is true for all “sublayers” which a layer may compose.
As used herein, the terms organic electroluminescent device and optoelectronic device and organic light-emitting device may be understood in the broadest sense as any device including one or more light-emitting layers B, each as a whole including one or more TADF materials, one or more excitation energy transfer components EET-2, one or more small FWHM emitters SB, and optionally one or more host materials HB, for all of which the above-mentioned definitions and preferred embodiments may apply.
In a preferred embodiment of the invention, the organic electroluminescent device emits blue light from 440 to 480 nm. In a preferred embodiment of the invention, the organic electroluminescent device has a main emission peak in the range of from 440 to 480 nm. In a preferred embodiment of the invention, the organic electroluminescent device has an emission maximum of the main emission peak in the range of from 440 to 480 nm.
In a particularly preferred embodiment of the invention, the organic electroluminescent device emits blue light from 450 to 470 nm. In a particularly preferred embodiment of the invention, the organic electroluminescent device has a main emission peak in the range of from 450 to 470 nm. In a particularly preferred embodiment of the invention, the organic electroluminescent device has an emission maximum of the main emission peak in the range of from 450 to 470 nm.
In a preferred embodiment of the invention, the organic electroluminescent device is a device selected from the group consisting of an organic light-emitting diode (OLED), a light-emitting electrochemical cell (LEC), and a light-emitting transistor.
Particularly preferably, the organic electroluminescent device is an organic light-emitting diode (OLED). Optionally, the organic electroluminescent device as a whole may be intransparent (non-transparent), semi-transparent or (essentially) transparent.
As used throughout the present application, the term “cyclic group” may be understood in the broadest sense as any mono-, bi- or polycyclic moieties.
As used throughout the present application, the terms “ring” and “ring system” may be understood in the broadest sense as any mono-, bi- or polycyclic moieties.
The term “ring atom” refers to any atom which is part of the cyclic core of a ring or a ring structure, and not part of a substituent optionally attached to it.
As used throughout the present application, the term “carbocycle” may be understood in the broadest sense as any cyclic group in which the cyclic core structure includes only carbon atoms that may of course be substituted with hydrogen or any other substituents defined in the specific embodiments of the invention. It is understood that the term “carbocyclic” as adjective refers to cyclic groups in which the cyclic core structure includes only carbon atoms that may of course be substituted with hydrogen or any other substituents defined in the specific embodiments of the invention. It is understood that the term “carbocycle” or a “carbocyclic ring system” may refer to both, an aliphatic and an aromatic cyclic group or ring system.
As used throughout the present application, the term “heterocycle” may be understood in the broadest sense as any cyclic group in which the cyclic core structure includes not just carbon atoms, but also at least one heteroatom. It is understood that the term “heterocyclic” as adjective refers to cyclic groups in which the cyclic core structure includes not just carbon atoms, but also at least one heteroatom. The heteroatoms may, unless stated otherwise in specific embodiments, at each occurrence be the same or different and be individually selected from the group consisting of N, O, S, and Se. All carbon atoms or heteroatoms included in a heterocycle in the context of the invention may of course be substituted with hydrogen or any other substituents defined in the specific embodiments of the invention. It is understood that the term “heterocycle” or a “heterocyclic ring system” may refer to both, an aliphatic and a heteroaromatic cyclic group or ring system.
As used throughout the present application, the term “aromatic ring system” may be understood in the broadest sense as any bi- or polycyclic aromatic moiety.
As used throughout the present application, the term “heteroaromatic ring system” may be understood in the broadest sense as any bi- or polycyclic heteroaromatic moiety.
As used throughout the present application, the term “fused” when referring to aromatic or heteroaromatic ring systems means that the aromatic or heteroaromatic rings that are “fused” share at least one bond that is part of both ring systems. For example naphthalene (or naphthyl when referred to as substituent) or benzothiophene (or benzothiophenyl when referred to as substituent) are considered fused aromatic ring systems in the context of the present invention, in which two benzene rings (for naphthalene) or a thiophene and a benzene (for benzothiophene) share one bond. It is also understood that sharing a bond in this context includes sharing the two atoms that build up the respective bond and that fused aromatic or heteroaromatic ring systems can be understood as one aromatic or heteroaromatic system. Additionally, it is understood, that more than one bond may be shared by the aromatic or heteroaromatic rings building up a fused aromatic or heteroaromatic ring system (e.g. in pyrene). Furthermore, it will be understood that aliphatic ring systems may also be fused and that this has the same meaning as for aromatic or heteroaromatic ring systems, with the exception of course, that fused aliphatic ring systems are not aromatic.
As used throughout the present application, the terms “aryl” and “aromatic” may be understood in the broadest sense as any mono-, bi- or polycyclic aromatic moieties. Herein, unless indicated differently in specific embodiments, an aryl group preferably contains 6 to 60 aromatic ring atoms, and a heteroaryl group preferably contains 5 to 60 aromatic ring atoms, of which at least one is a heteroatom. Notwithstanding, throughout the application the number of aromatic ring atoms (in particular of aromatic ring atoms that are carbon atoms) may be given as subscripted number in the definition of certain substituents. In particular, the heteroaromatic ring includes one to three heteroatoms. Again, the terms “heteroaryl” and “heteroaromatic” may be understood in the broadest sense as any mono-, bi- or polycyclic heteroaromatic moieties that include at least one heteroatom. The heteroatoms may at each occurrence be the same or different and be individually selected from the group consisting of N, O, S, and Se. Accordingly, the term “arylene” refers to a divalent substituent that bears two binding sites to other molecular structures and thereby serving as a linker structure. In case, a group in the exemplary embodiments is defined differently from the definitions given here, for example, the number of aromatic ring atoms or number of heteroatoms differs from the given definition, the definition in the exemplary embodiments is to be applied. According to the invention, a condensed (annulated) aromatic or heteroaromatic polycycle is built of two or more single aromatic or heteroaromatic cycles, which formed the polycycle via a condensation reaction.
In particular, as used throughout the present application the term “aryl group” or “heteroaryl group” includes groups which can be bound via any position of the aromatic or heteroaromatic group, derived from benzene, naphthalene, anthracene, phenanthrene, pyrene, dihydropyrene, chrysene, perylene, fluoranthene, benzanthracene, benzophenanthrene, tetracene, pentacene, benzopyrene, furan, benzofuran, isobenzofuran, dibenzofuran, thiophene, benzothiophene, isobenzothiophene, dibenzothiophene; selenophene, benzoselenophene, isobenzoselenophene, dibenzoselenophene; pyrrole, indole, isoindole, carbazole, pyridine, quinoline, isoquinoline, acridine, phenanthridine, benzo-5,6-quinoline, benzo-6,7-quinoline, benzo-7,8-quinoline, phenothiazine, phenoxazine, pyrazole, indazole, imidazole, benzimidazole, naphthoimidazole, phenanthroimidazole, pyridoimidazole, pyrazinoimidazole, quinoxalinoimidazole, oxazole, benzoxazole, naphthooxazole, anthroxazol, phenanthroxazol, isoxazole, 1,2-thiazole, 1,3-thiazole, benzothiazole, pyridazine, benzopyridazine, pyrimidine, benzopyrimidine, 1,3,5-triazine, quinoxaline, pyrazine, phenazine, naphthyridine, carboline, benzocarboline, phenanthroline, 1,2,3-triazole, 1,2,4-triazole, benzotriazole, 1,2,3-oxadiazole, 1,2,4-oxadiazole, 1,2,5-oxadiazole, 1,2,3,4-tetrazine, purine, pteridine, indolizine and benzothiadiazole or combinations of the abovementioned groups.
In certain embodiments of the invention, adjacent substituents bonded to an aromatic or heteroaromatic ring may together form an additional mono- or polycyclic aliphatic or aromatic or heteroaromatic, carbocyclic or heterocyclic ring system which is fused to the aromatic or heteroaromatic ring to which the substituents are bonded. It is understood that the optionally so formed fused ring system will be larger (meaning it includes more ring atoms) than the aromatic or heteroaromatic ring to which the adjacent substituents are bonded. In these cases, the “total” amount of ring atoms included in the fused ring system is to be understood as the sum of ring atoms included in the aromatic or heteroaromatic ring to which the adjacent substituents are bonded and the ring atoms of the additional ring system formed by the adjacent substituents, wherein, however, the carbon atoms that are shared by the ring systems which are fused are counted once and not twice. For example, a benzene ring may have two adjacent substituents that form another benzene ring so that a naphthalene core is built. This naphthalene core then includes 10 ring atoms as two carbon atoms are shared by the two benzene rings and thus only counted once and not twice. The term “adjacent substituents” in this context refers to substituents attached to the same or to neighboring ring atoms (e.g., of a ring system).
As used throughout the present application, the term “aliphatic” when referring to ring systems may be understood in the broadest sense and means that none of the rings that build up the ring system is an aromatic or heteroaromatic ring. It is understood that such an aliphatic ring system may be fused to one or more aromatic or heteroaromatic rings so that some (but not all) carbon- or heteroatoms included in the core structure of the aliphatic ring system are part of an attached aromatic or heteroaromatic ring.
As used above and herein, the term “alkyl group” may be understood in the broadest sense as any linear, branched, or cyclic alkyl substituent. In particular, the term alkyl includes the substituents methyl (Me), ethyl (Et), n-propyl (nPr), i-propyl (iPr), cyclopropyl, n-butyl (nBu), i-butyl (iBu), s-butyl (sBu), t-butyl (tBu), cyclobutyl, 2-methylbutyl, n-pentyl, s-pentyl, t-pentyl, 2-pentyl, neo-pentyl, cyclopentyl, n-hexyl, s-hexyl, t-hexyl, 2-hexyl, 3-hexyl, neo-hexyl, cyclohexyl, 1-methylcyclopentyl, 2-methylpentyl, n-heptyl, 2-heptyl, 3-heptyl, 4-heptyl, cycloheptyl, 1-methylcyclohexyl, n-octyl, 2-ethylhexyl, cyclooctyl, 1-bicyclo[2,2,2]octyl, 2-bicyclo[2,2,2]-octyl, 2-(2,6-dimethyl)octyl, 3-(3,7-dimethyl)octyl, adamantyl, 2,2,2-trifluorethyl, 1,1-dimethyl-n-hex-1-yl, 1,1-dimethyl-n-hept-1-yl, 1,1-dimethyl-n-oct-1-yl, 1,1-dimethyl-n-dec-1-yl, 1,1-dimethyl-n-dodec-1-yl, 1,1-dimethyl-n-tetradec-1-yl, 1,1-dimethyl-n-hexadec-1-yl, 1,1-dimethyl-n-octadec-1-yl, 1,1-diethyl-n-hex-1-yl, 1,1-diethyl-n-hept-1-yl, 1,1-diethyl-n-oct-1-yl, 1,1-diethyl-n-dec-1-yl, 1,1-diethyl-n-dodec-1-yl, 1,1-diethyl-n-tetradec-1-yl, 1,1-diethyl-n-hexadec-1-yl, 1,1-diethyl-n-octadec-1-yl, 1-(n-propyl)-cyclohex-1-yl, 1-(n-butyl)-cyclohex-1-yl, 1-(n-hexyl)-cyclohex-1-yl, 1-(n-octyl)-cyclohex-1-yl and 1-(n-decyl)-cyclohex-1-yl.
As used above and herein, the term “alkenyl” includes linear, branched, and cyclic alkenyl substituents. The term alkenyl group exemplarily includes the substituents ethenyl, propenyl, butenyl, pentenyl, cyclopentenyl, hexenyl, cyclohexenyl, heptenyl, cycloheptenyl, octenyl, cyclooctenyl or cyclooctadienyl.
As used above and herein, the term “alkynyl” includes linear, branched, and cyclic alkynyl substituents. The term alkynyl group exemplarily includes ethynyl, propynyl, butynyl, pentynyl, hexynyl, heptynyl or octynyl.
As used above and herein, the term “alkoxy” includes linear, branched, and cyclic alkoxy substituents. The term alkoxy group exemplarily includes methoxy, ethoxy, n-propoxy, i-propoxy, n-butoxy, i-butoxy, s-butoxy, t-butoxy and 2-methylbutoxy.
As used above and herein, the term “thioalkoxy” includes linear, branched, and cyclic thioalkoxy substituents, in which the O of the exemplarily alkoxy groups is replaced by S.
As used above and herein, the terms “halogen” and “halo” may be understood in the broadest sense as being preferably fluorine, chlorine, bromine or iodine.
All hydrogen atoms (H) included in any structure referred to herein may at each occurrence independently of each other, and without this being indicated specifically, be replaced by deuterium (D). The replacement of hydrogen by deuterium is common practice and obvious for the person skilled in the art who also knows how to achieve this synthetically.
It is understood that when a molecular fragment is described as being a substituent or otherwise attached to another moiety, its name may be written as if it were a fragment (e.g. naphthyl, dibenzofuryl) or as if it were the whole molecule (e.g. naphthalene, dibenzofuran). As used herein, these different ways of designating a substituent or attached fragment are considered to be equivalent.
When referring to concentrations or compositions and unless stated otherwise, percentages refer to weight percentages, which has the same meaning as percent by weight or % by weight ((weight/weight), (w/w), wt. %).
Orbital and excited state energies can be determined either by means of experimental methods or by calculations employing quantum-chemical methods, in particular density functional theory calculations. Herein, the energy of the highest occupied molecular orbital EHOMO is determined by methods known to the person skilled in the art from cyclic voltammetry measurements with an accuracy of 0.1 eV.
The energy of the lowest unoccupied molecular orbital ELUMO may be determined by methods known to the person skilled in the art from cyclic voltammetry measurements with an accuracy of 0.1 eV. If ELUMO may be determined by cyclic voltammetry measurements, it will herein be denoted as ECVLUMO. Alternatively, and herein preferably, ELUMO is calculated as EHOMO+Egap, wherein the energy of the first excited singlet state S1 (vide infra) is used as Egap, unless stated otherwise, for host materials HB, TADF materials EB, and small FWHM emitters SB. This is to say that for host materials HB, TADF materials EB, and small FWHM emitters SB, Egap is determined from the onset of the emission spectrum at room temperature (i.e. approx. 20° C.) (steady-state spectrum; for TADF materials EB a spin-coated film of 10% by weight of EB in poly(methyl methacrylate), PMMA, is typically used; for small FWHM emitters SB a spin-coated film of 1-5%, preferably 2% by weight of SB in PMMA is typically used; for host materials HB a spin-coated neat film of the respective host material HB is typically used). For phosphorescence materials PB, Egap is also determined from the onset of the emission spectrum at room temperature (i.e. approx. 20° C.) (typically measured from a spin-coated film of 10% by weight of PB in PMMA).
Absorption spectra are recorded at room temperature (i.e. approximately 20° C.). For TADF materials EB, absorption spectra are typically measured from a spin-coated film of 10% by weight of EB in poly(methyl methacrylate) (PMMA). For small FWHM emitters SB absorption spectra are typically measured from a spin-coated film of 1-5%, preferably 2% by weight of SB in PMMA. For host materials HB absorption spectra are typically measured from a spin-coated neat film of the host material HB. For phosphorescence materials PB, absorption spectra are typically measured from a spin-coated film of 10% by weight of PB in PMMA. Alternatively, absorption spectra may also be recorded from solutions of the respective molecules, for example in dichloromethane or toluene, wherein the concentration of the solution is typically chosen so that the maximum absorbance preferably is in a range of 0.1 to 0.5.
The onset of an absorption spectrum is determined by computing the intersection of the tangent to the absorption spectrum with the x-axis. The tangent to the absorption spectrum is set at the low-energy side of the absorption band and at the point at half maximum of the maximum intensity of the absorption spectrum.
Unless stated otherwise, the energy of the first (i.e. the lowermost) excited triplet state T1 is determined from the onset the phosphorescence spectrum at 77K (for TADF materials EB a spin-coated film of 10% by weight of EB in PMMA is typically used; for small FWHM emitters SB a spin-coated film of 1-5%, preferably 2% by weight of SB in PMMA is typically used; for host materials HB, a spin-coated neat film of the respective host material HB is typically used; for phosphorescence materials PB a spin-coated film of 10% by weight of PB in PMMA is typically used and the measurement is typically performed at room temperature (i.e. approximately 20° C.). As laid out for instance in EP2690681A1, it is acknowledged that for TADF materials EB with small ΔEST values, intersystem crossing and reverse intersystem crossing may both occur even at low temperatures. In consequence, the emission spectrum at 77K may include emission from both, the S1 and the T1 state. However, as also described in EP2690681A1, the contribution/value of the triplet energy is typically considered dominant.
Unless stated otherwise, the energy of the first (i.e. the lowermost) excited singlet state S1 is determined from the onset the fluorescence spectrum at room temperature (i.e. approx. 20° C.) (steady-state spectrum; for TADF materials EB a spin-coated film of 10% by weight of EB in PMMA is typically used; for small FWHM emitters SB spin-coated film of 1-5%, preferably 2% by weight of SB in PMMA is typically used; for host materials HB, a spin-coated neat film of the respective host material HB is typically used; for phosphorescence materials PB a spin-coated film of 10% by weight of PB in PMMA is typically used). For phosphorescence materials PB displaying efficient intersystem crossing however, room temperature emission may be (mostly) phosphorescence and not fluorescence. In this case, the onset of the emission spectrum at room temperature (i.e. approx. 20° C.) is used to determine the energy of the first (i.e. the lowermost) excited triplet state T1 as stated above.
The onset of an emission spectrum is determined by computing the intersection of the tangent to the emission spectrum with the x-axis. The tangent to the emission spectrum is set at the high-energy side of the emission band and at the point at half maximum of the maximum intensity of the emission spectrum.
The ΔEST value, which corresponds to the energy difference between the first (i.e. the lowermost) excited singlet state (S1) and the first (i.e. the lowermost) excited triplet state (T1), is determined based on the first (i.e. the lowermost) excited singlet state energy and the first (i.e. the lowermost) excited triplet state energy, which were determined as stated above.
As known to the skilled artisan, the full width at half maximum (FWHM) of an emitter (for example a small FWHM emitter SB) is readily determined from the respective emission spectrum (fluorescence spectrum for fluorescent emitters and phosphorescence spectrum for phosphorescent emitters). For small FWHM emitters SB, the fluorescence spectrum is typically used. All reported, FWHM values typically refer to the main emission peak (i.e. the peak with the highest intensity). The means of determining the FWHM (herein preferably reported in electron volts, eV) are part of the common knowledge of those skilled in the art. Given for example that the main emission peak of an emission spectrum reaches its half maximum emission (i.e. 50% of the maximum emission intensity) at the two wavelengths λ1 and λ2, both obtained in nanometers (nm) from the emission spectrum, the FWHM in electron volts (eV) is commonly (and herein) determined using the following equation:
As used herein, if not defined more specifically in a particular context, the designation of the colors of emitted and/or absorbed light is as follows:
The invention is illustrated by the following examples and the claims.
Cyclic Voltammetry
Cyclic voltammograms of solutions having concentration of 10−3 mol/I of the organic molecules in dichloromethane or a suitable solvent and a suitable supporting electrolyte (e.g. 0.1 mol/I of tetrabutylammonium hexafluorophosphate) are measured. The measurements are conducted at room temperature (i.e. (approximately) 20° C.) and under nitrogen atmosphere with a three-electrode assembly (working and counter electrodes: Pt wire, reference electrode: Pt wire) and calibrated using FeCp2/FeCp2+ as internal standard. HOMO and LUMO data was corrected using ferrocene as internal standard against SCE.
Density Functional Theory Calculation
Molecular structures are optimized employing the BP86 functional and the resolution of identity approach (RI). Excitation energies are calculated using the (BP86) optimized structures employing Time-Dependent DFT (TD-DFT) methods. Def2-SVP basis sets and a m4-grid for numerical integration were used. The Turbomole program package was used for all calculations. Orbital and excited state energies are calculated with the B3LYP functional. However, herein, orbital and excited state energies are preferably determined experimentally as stated above. All orbital and excited state energies reported herein (see experimental results) have been determined experimentally.
Photophysical Measurements
Sample Pretreatment: Vacuum-Evaporation
As stated before, photophysical measurements of individual compounds (for example organic molecules or transition metal complexes) that may be included in a light-emitting layer B of the organic electroluminescent device according to the present invention (for example host materials HB, TADF materials EB, phosphorescence materials PB or small FWHM emitters SB) were typically performed using either spin-coated neat films (in case of host materials HB) or spin-coated films of the respective material in poly(methyl methacrylate) (PMMA) (e.g. for TADF materials EB phosphorescent materials PB, and small FWHM emitters SB). These films were spin coated films and, unless stated differently for specific measurements, the concentration of the materials in the PMMA-films was 10% by weight for TADF materials EB and for phosphorescent materials PB or 1-5%, preferably 2% by weight for small FWHM emitters SB. Alternatively, and as stated previously, some photophysical measurements may also be performed from solutions of the respective molecules, for example in dichloromethane or toluene, wherein the concentration of the solution is typically chosen so that the maximum absorbance preferably is in a range of 0.1 to 0.5.
Apparatus: Spin150, SPS euro.
The sample concentration was 1.0 mg/ml, typically dissolved in Toluene/DCM as suitable solvent.
Program: 7-30 sec. at 2000 U/min. After coating, the films were dried at 70° C. for 1 min.
For the purpose of further studying compositions of certain materials as present in the EML of organic electroluminescent devices (according to the present invention or comparative), the samples for photophysical measurements were produced from the same materials used for device fabrication by vacuum deposition of 50 nm of the respective light-emitting layer B on quartz substrates. Photophysical characterization of the samples are conducted under nitrogen atmosphere.
Absorption Measurements
A Thermo Scientific Evolution 201 UV-Visible Spectrophotometer is used to determine the wavelength of the absorption maximum of the sample in the wavelength region above 270 nm. This wavelength is used as excitation wavelength for photoluminescence spectral and quantum yield measurements.
Photoluminescence Spectra
Steady-state emission spectra are recorded using a Horiba Scientific, Modell FluoroMax-4 equipped with a 150 W Xenon-Arc lamp, excitation- and emissions monochromators. The samples are placed in a cuvette and flushed with nitrogen during the measurements.
Photoluminescence Quantum Yield Measurements
For photoluminescence quantum yield (PLQY) measurements an integrating sphere, the Absolute PL Quantum Yield Measurement C9920-03G system (Hamamatsu Photonics) is used. The samples are kept under nitrogen atmosphere throughout the measurement. Quantum yields are determined using the software U6039-05 and given in %. The yield is calculated using the equation:
TCSPC (Time-Correlated Single-Photon Counting)
Unless stated otherwise in the context of certain embodiments or analyses, excited state population dynamics are determined employing Edinburgh Instruments FS5 Spectrofluoremeters, equipped with an emission monochromator, a temperature stabilized photomultiplier as detector unit and a pulsed LED (310 nm central wavelength, 910 μs pulse width) as excitation source. The samples are placed in a cuvette and flushed with nitrogen during the measurements.
To determine the average decay time
The method may be applied for fluorescence and phosphorescence materials to determine the excited state lifetimes. For TADF materials, the full decay dynamics as described below need to be gathered.
Full Decay Dynamics
The full excited state population decay dynamics over several orders of magnitude in time and signal intensity is achieved by carrying out TCSPC measurements in 4 time windows: 200 ns, 1 μs, and 20 μs, and a longer measurement spanning >80 μs. The measured time curves are then processed in the following way:
A background correction is applied by determining the average signal level before excitation and subtracting.
Data analysis is done using mono-exponential or bi-exponential fitting of prompt fluorescence (PF) and delayed fluorescence (DF) decays separately. By weighting the specific decay time constants τi from the fits with the corresponding amplitudes Ai, the average lifetime
The ratio of delayed and prompt fluorescence (n-value) is calculated by the integration of respective photoluminescence decays in time.
Transient Photoluminescence Measurements with Spectral Resolution
In transient photoluminescence (PL) measurements with spectral resolution, PL spectra at defined delay times after pulsed optical excitation are recorded.
An exemplary device for measuring transient PL spectra includes:
In the course of the measurement, the sample is placed in the sample chamber and irradiated with the pulsed laser. Emitted light from the sample is taken in a 90 degree direction with respect to the irradiation direction of the laser pulses. It is dispersed by the spectrograph and directed onto the detector (the CCD camera in the exemplary device), thus obtaining a wavelength resolved emission spectrum. The time delay between laser irradiation and detection, and the duration (i.e. the gate time) of detection are controlled by the timing generator.
It should be noted, that transient photolumminescence may be measured by a device different from the one described in the exemplary device.
Production and Characterization of Organic Electroluminescence Devices
Via vacuum-deposition methods OLED devices including organic molecules according to the invention can be produced. If a layer contains more than one compound, the weight-percentage of one or more compounds is given in %. The total weight-percentage values amount to 100%, thus if a value is not given, the fraction of this compound equals to the difference between the given values and 100%.
The not fully optimized OLEDs are characterized using standard methods and measuring electroluminescence spectra, the external quantum efficiency (in %) in dependency on the intensity, calculated using the light detected by the photodiode, and the current. The FWHM of the devices is determined from the electroluminescence spectra as stated previously for photoluminescence spectra (fluorescence or phosphorescence). The reported FWHM refers to the main emission peak (i.e. the peak with the highest emission intensity). The OLED device lifetime is extracted from the change of the luminance during operation at constant current density. The LT50 value corresponds to the time, where the measured luminance decreased to 50% of the initial luminance, analogously LT80 corresponds to the time point, at which the measured luminance decreased to 80% of the initial luminance, LT97 to the time point, at which the measured luminance decreased to 97% of the initial luminance etc.
Accelerated lifetime measurements are performed (e.g. applying increased current densities). Exemplarily LT80 values at 500 cd/m2 are determined using the following equation:
wherein L0 denotes the initial luminance at the applied current density. The values correspond to the average of several pixels (typically two to eight).
Experimental Results
Stack Materials
1measured in neat film.
TADF materials EB that may be selected as the TADF material EB and excitation energy transfer component EET-2
Phosphorescence materials PB that may be selected as excitation energy transfer component EET-2
Small FWHM Emitters SB
Results I: EET-2 is a phosphorescence material PB in the light-emitting layer B (emission layer, 5)
Composition of the light-emitting layer B of devices D1 (the percentages refer to weight percent):
Setup 1 from Table 2 was used, wherein mCBP (HB-1) was used as host material HB, EB-1 was used as TADF material EB, PB-3 was used as excitation energy transfer component EET-2 (here exemplarily a phosphorescence material PB), and SB-15 was used as the small FWHM emitter SB.
Results II: EET-2 is a phosphorescence material PB in the light-emitting layer B (emission layer, 6) and exciton management layer EXL adjacent to B
Composition of the light-emitting layer B of devices D2 (the percentages refer to weight percent):
Setup 2 from Table 3 was used, wherein mCBP (HB-1) was used as host material HB, EB-1 was used as TADF material EB, PB-3 was used as excitation energy transfer component EET-2 (here exemplarily a phosphorescence material PB), and SB-15 was used as the small FWHM emitter SB.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20197071.2 | Sep 2020 | EP | regional |
| 20197072.0 | Sep 2020 | EP | regional |
| 20197073.8 | Sep 2020 | EP | regional |
| 20197074.6 | Sep 2020 | EP | regional |
| 20197075.3 | Sep 2020 | EP | regional |
| 20197076.1 | Sep 2020 | EP | regional |
| 20197588.5 | Sep 2020 | EP | regional |
| 20197589.3 | Sep 2020 | EP | regional |
| 20217041.1 | Dec 2020 | EP | regional |
| 21170775.7 | Apr 2021 | EP | regional |
| 21170776.5 | Apr 2021 | EP | regional |
| 21170779.9 | Apr 2021 | EP | regional |
| 21170783.1 | Apr 2021 | EP | regional |
| 21184616.7 | Jul 2021 | EP | regional |
| 21184619.1 | Jul 2021 | EP | regional |
| 21185402.1 | Jul 2021 | EP | regional |
| 21186615.7 | Jul 2021 | EP | regional |
This application is a U.S. National Phase Patent Application of International Patent Application Number PCT/EP2021/075655, filed on Sep. 17, 2021, which claims priority to European Patent Application Number 20197076.1, filed on Sep. 18, 2020, European Patent Application Number 20197075.3, filed on Sep. 18, 2020, European Patent Application Number 20197074.6, filed on Sep. 18, 2020, European Patent Application Number 20197073.8, filed on Sep. 18, 2020, European Patent Application Number 20197072.0, filed on Sep. 18, 2020, European Patent Application Number 20197071.2, filed on Sep. 18, 2020, European Patent Application Number 20197589.3, filed on Sep. 22, 2020, European Patent Application Number 20197588.5, filed on Sep. 22, 2020, European Patent Application Number 20217041.1, filed on Dec. 23, 2020, European Patent Application Number 21170783.1, filed on Apr. 27, 2021, European Patent Application Number 21170775.7, filed on Apr. 27, 2021, European Patent Application Number 21170776.5, filed on Apr. 27, 2021, European Patent Application Number 21170779.9, filed on Apr. 27, 2021, European Patent Application Number 21184616.7, filed on Jul. 8, 2021, European Patent Application Number 21184619.1, filed on Jul. 8, 2021, European Patent Application Number 21185402.1, filed on Jul. 13, 2021, and European Patent Application Number 21186615.7, filed on Jul. 20, 2021, the entire content of each of which is incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2021/075655 | 9/17/2021 | WO |
