Patent Application
20240008300
This application claims priority to Chinese Patent Application No. 202210734050.7 filed on Jun. 29, 2022, the disclosure of which is incorporated herein by reference in its entirety.
The present disclosure relates to a top-emission organic electroluminescent device. More specifically, the present disclosure relates to a top-emission organic electroluminescent device with a high-efficiency conversion rate and a display assembly comprising the top-emission organic electroluminescent device.
Since C. W. Tang and Van Slyke reported a high-brightness and low-voltage organic electroluminescent device in 1987, organic electroluminescence has been developed rapidly. With the increasing mature of the research on monochromatic organic electroluminescent devices with three primary colors: red, green and blue, especially the improvement of the performance of the blue-light device, such as the brightness and the lifetime. The organic electroluminescent device has entered a stage of actual application and has been widely used in daily used electronic products. In an actual commercial use, a large area and an active driving technology are mainstreams of an organic electroluminescence display technology at present. To achieve large-size display, a TFT backplane driving technology needs to be used. Based on this, the preparation of a traditional bottom-emission (BE) organic electroluminescent device (hereinafter referred to as a bottom-emission device) brings about the problem of low aperture ratio. Therefore, to achieve an active-driven, large-area and high-brightness organic electroluminescence display screen, a top-emission (TE) organic electroluminescent device (hereinafter referred to as a top-emission device) needs to be used. Among commercialized organic electroluminescent devices at present, generally, a top-emission organic light-emitting device is prepared and an optical microcavity in the device is adjusted to meet a requirement of the International Commission for Electrons and Optics for a color coordinate of a display.
As previously described, the commercial devices at present are top-emission devices. However, since the top-emission device has an optical microcavity effect, intrinsic characteristics of a material (for example, a spectrum of the top-emission device cannot reflect an intrinsic spectral shape of an emissive layer) are covered up, and for the top-emission device, a thickness of a film needs to be adjusted to adjust the microcavity to obtain a comprehensive evaluation of device performance, thereby increasing the number of experiments and resulting in a relatively high preparation cost. Therefore, the top-emission device is not the most suitable device structure for performing a performance evaluation of a new material. Since the bottom-emission device can well reflect the intrinsic characteristics of the material and is simple to prepare and low in cost, research and development personnel generally use the bottom-emission device to perform an initial evaluation of the performance of the new material when developing the new material, and then use a potential material in the top-emission device to save the time and the cost. Therefore, it is necessary to study an association of performance between a bottom-emission device and a top-emission device having the same device structure. If the device performance of the bottom-emission device can be associated to a certain extent with the performance of the top-emission device having the same device structure, the time and cost for material development and screening can be significantly saved.
In a mature organic electroluminescent device structure in the industry, an anode, a hole transporting region, an emissive layer (EML), an electron transporting region and a cathode (the cathode may further comprise an electron injection layer (EIL), constituting a multi-stack cathode) are generally comprised, where the hole transporting region may comprise a hole injection layer (HIL), a hole transporting layer (HTL), an electron blocking layer (EBL), and the electron transporting region may comprise a hole blocking layer (HBL) and an electron transporting layer (ETL). The HBL and/or the EBL may be selectively present due to different device structures. One or more layers of the same functional layer, for example, one or more layers of the HIL, may be used according to different requirements and optimization results of the device.
A working principle of the organic electroluminescent device is as follows: electrons and holes are injected through the cathode and the anode of the device under the drive of a certain voltage into the electron transporting region and the hole transporting region from the cathode and the anode, respectively, and then separately migrated to the emissive layer, the electrons and the holes are recombined to form excitons in the emissive layer, and visible light is emitted after the exciton recombination. Therefore, studying the exciton recombination behavior in the emissive layer is an important factor in studying the device performance.
In view of the above problems, the present disclosure aims to provide a high-efficiency top-emission organic electroluminescent device. The top-emission organic electroluminescent device comprises an anode, a multi-stack cathode and an emissive layer disposed between the two electrodes. The emissive layer comprises an emissive doped material, wherein a maximum emission wavelength of the emissive doped material is λmax, and 500 nm≤λmax≤700 nm. The top-emission organic electroluminescent device has a maximum external quantum efficiency conversion rate E, wherein when 500 nm≤λmax≤600 nm, E≥1.625; when 600 nm<λmax≤700 nm, E≥1.850; and E=EQEA/EQEB. EQEA is maximum external quantum efficiency of the top-emission device at a current density of Jo, and EQEB is maximum external quantum efficiency of a bottom-emission device at the current density of J0. The bottom-emission device has the same device structure as the top-emission device. The bottom-emission device has an exciton recombination region, and the exciton recombination peak position is located in the emissive layer within a region greater than 0% and less than or equal to 65% of the thickness of the emissive layer from the side close to the anode.
According to an embodiment of the present disclosure, disclosed is a top-emission organic electroluminescent device, which comprises:
According to an embodiment of the present disclosure, disclosed is a top-emission organic electroluminescent device, which comprises an anode, a cathode and an emissive layer disposed between the anode and the cathode;
According to an embodiment of the present disclosure, further disclosed is a display assembly, which comprises the top-emission organic electroluminescent device in the preceding embodiment.
According to an embodiment of the present disclosure, further disclosed is a use of the top-emission organic electroluminescent device in the preceding embodiment in an electronic device, an electronic element module, a display device or a lighting device.
In the present application, through researches on the exciton recombination peak position of the bottom-emission device having the same device structure as the top-emission organic electroluminescent device and the efficiency conversion rate E between the bottom-emission device and the top-emission device, it is found that compared to other top-emission organic electroluminescent devices, the top-emission organic electroluminescent device of the present disclosure can exhibit more excellent device performance even if the same organic emissive doped material is used.
As used in herein, “top” means furthest away from a substrate, while “bottom” means
closest to the substrate. Where a first layer is described as “disposed over” a second layer, the first layer is disposed further away from the substrate. There may be other layers between the first and second layers, unless it is specified that the first layer is “in contact with” the second layer. For example, a cathode may be described as “disposed over” an anode, even though there are various organic layers in between.
As used herein, the term “OLED device” comprises an anode layer, a cathode layer and one or more organic layers disposed between the anode layer and the cathode layer. An “OLED device” may be bottom-emission, that is, light is emitted from the substrate (a bottom-emission device), or may be top-emission, that is, light is emitted from the encapsulation layer (a top-emission device), or may be a transparent device, that is, light is emitted from both the substrate and the encapsulation side at the same time.
As used herein, the term “encapsulation layer” may be a thin film encapsulation with a thickness of less than 100 micrometers, which includes one or more thin films directly disposed on the device, or may be a cover glass glued to the substrate.
As used herein, the term “light extraction layer” may refer to a light diffuser film, or other microstructures having a light extraction effect, or a thin film coating having a light out-coupling effect. The light extraction layer may be disposed on a substrate surface of the OLED, and may also be disposed at other suitable positions, such as between the substrate and the anode, or between the organic layer and the cathode, or between the cathode and the encapsulation layer, or a surface of the encapsulation layer.
The sectional views of the organic electroluminescent devices provided in the specific embodiments of the present disclosure are schematically shown without limitation. The figures are not necessarily drawn to scale. Some of the layer structures in the figures can also be added or omitted as needed. Substrates of the organic electroluminescent devices can be fabricated on various types of substrates such as glass, plastic, and metal. The properties and functions of these various layers, as well as example materials, are described in more detail in U.S. Pat. No. 7,279,704 at cols. 6-10, the contents of which are incorporated by reference herein in its entirety.
Devices fabricated in accordance with embodiments of the present disclosure can be incorporated into a wide variety of consumer products that have one or more of the electronic component modules (or units) incorporated therein. Some examples of such consumer products include flat panel displays, monitors, medical monitors, televisions, billboards, lights for interior or exterior illumination and/or signaling, heads-up displays, fully or partially transparent displays, flexible displays, smart phones, tablets, phablets, wearable devices, smart watches, laptop computers, digital cameras, camcorders, viewfinders, micro-displays, 3-D displays, vehicles displays, and vehicle tail lights.
Halogen or halide—as used herein includes fluorine, chlorine, bromine, and iodine.
Alkyl—as used herein includes both straight and branched chain alkyl groups. Alkyl
may be alkyl having 1 to 20 carbon atoms, preferably alkyl having 1 to 12 carbon atoms, and more preferably alkyl having 1 to 6 carbon atoms. Examples of alkyl groups include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an s-butyl group, an isobutyl group, a t-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, an n-decyl group, an n-undecyl group, an n-dodecyl group, an n-tridecyl group, an n-tetradecyl group, an n-pentadecyl group, an n-hexadecyl group, an n-heptadecyl group, an n-octadecyl group, a neopentyl group, a 1-methylpentyl group, a 2-methylpentyl group, a 1-pentylhexyl group, a 1-butylpentyl group, a 1-heptyloctyl group, and a 3-methylpentyl group. Of the above, preferred are a methyl group, an ethyl group, a propyl group, an isopropyl group, a n-butyl group, an s-butyl group, an isobutyl group, a t-butyl group, an n-pentyl group, a neopentyl group, and an n-hexyl group. Additionally, the alkyl group may be optionally substituted.
Cycloalkyl—as used herein includes cyclic alkyl groups. The cycloalkyl groups may be those having 3 to 20 ring carbon atoms, preferably those having 4 to 10 carbon atoms. Examples of cycloalkyl include cyclobutyl, cyclopentyl, cyclohexyl, 4-methylcyclohexyl, 4,4-dimethylcylcohexyl, 1-adamantyl, 2-adamantyl, 1-norbornyl, 2-norbornyl, and the like. Of the above, preferred are cyclopentyl, cyclohexyl, 4-methylcyclohexyl, and 4,4-dimethylcylcohexyl. Additionally, the cycloalkyl group may be optionally substituted.
Heteroalkyl—as used herein, includes a group formed by replacing one or more carbons in an alkyl chain with a hetero-atom(s) selected from the group consisting of a nitrogen atom, an oxygen atom, a sulfur atom, a selenium atom, a phosphorus atom, a silicon atom, a germanium atom, and a boron atom. Heteroalkyl may be those having 1 to 20 carbon atoms, preferably those having 1 to 10 carbon atoms, and more preferably those having 1 to 6 carbon atoms. Examples of heteroalkyl include methoxymethyl, ethoxymethyl, ethoxyethyl, methylthiomethyl, ethylthiomethyl, ethylthioethyl, methoxymethoxymethyl, ethoxymethoxymethyl, ethoxyethoxyethyl, hydroxymethyl, hydroxyethyl, hydroxypropyl, mercaptomethyl, mercaptoethyl, mercaptopropyl, aminomethyl, aminoethyl, aminopropyl, dimethylaminomethyl, trimethylgermanylmethyl, trimethylgermanyl ethyl, trimethylgermanylisopropyl, dimethylethylgermanylmethyl, dimethylisopropylgermanylmethyl, tert-butylmethylgermanylmethyl, triethylgermanylmethyl, triethylgermanylethyl, triisopropylgermanylmethyl, triisopropylgermanylethyl, trimethylsilylmethyl, trimethylsilylethyl, and trimethyl silylsopropyl, triisopropylsilylmethyl, triisopropylsilylethyl. Additionally, the heteroalkyl group may be optionally substituted.
Alkenyl—as used herein includes straight chain, branched chain, and cyclic alkene groups. Alkenyl may be those having 2 to 20 carbon atoms, preferably those having 2 to 10 carbon atoms. Examples of alkenyl include vinyl, 1-propenyl group, 1-butenyl, 2-butenyl, 3-butenyl, 1,3-butandienyl, 1-methylvinyl, styryl, 2,2-diphenylvinyl, 1,2-diphenylvinyl, 1-methylallyl, 1,1-dimethylallyl, 2-methylallyl, 1-phenylallyl, 2-phenylallyl, 3-phenylallyl, 3,3 -diphenylallyl, 1,2-dimethylallyl, 1-phenyl-1-butenyl, 3-phenyl-1-butenyl, cyclopentenyl, cyclopentadienyl, cyclohexenyl, cycloheptenyl, cycloheptatrienyl, cyclooctenyl, cyclooctatetraenyl, and norbornenyl. Additionally, the alkenyl group may be optionally substituted.
Alkynyl—as used herein includes straight chain alkynyl groups. Alkynyl may be those having 2 to 20 carbon atoms, preferably those having 2 to 10 carbon atoms. Examples of alkynyl groups include ethynyl, propynyl, propargyl, 1-butynyl, 2-butynyl, 3-butynyl, 1-pentynyl, 2-pentynyl, 3,3 -dimethyl-1-butynyl, 3 -ethyl-3 -methyl-1-pentynyl, 3,3-diisopropyl-1-pentynyl, phenylethynyl, phenylpropynyl, etc. Of the above, preferred are ethynyl, propynyl, propargyl, 1-butynyl, 2-butynyl, 3-butynyl, 1-pentynyl, and phenylethynyl. Additionally, the alkynyl group may be optionally substituted.
Aryl or an aromatic group—as used herein includes non-condensed and condensed systems. Aryl may be those having 6 to 30 carbon atoms, preferably those having 6 to 20 carbon atoms, and more preferably those having 6 to 12 carbon atoms. Examples of aryl groups include phenyl, biphenyl, terphenyl, triphenylene, tetraphenylene, naphthalene, anthracene, phenalene, phenanthrene, fluorene, pyrene, chrysene, perylene, and azulene, preferably phenyl, biphenyl, terphenyl, triphenylene, fluorene, and naphthalene. Examples of non-condensed aryl groups include phenyl, biphenyl-2-yl, biphenyl-3-yl, biphenyl-4-yl, p-terphenyl-4-yl, p-terphenyl-3-yl, p-terphenyl-2-yl, m-terphenyl-4-yl, m-terphenyl-3-yl, m-terphenyl-2-yl, o-tolyl, m-tolyl, p-tolyl, p-(2-phenylpropyl)phenyl, 4′-methylbiphenylyl, 4″-t-butyl-p-terphenyl-4-yl, o-cumenyl, m-cumenyl, p-cumenyl, 2,3-xylyl, 3,4-xylyl, 2,5-xylyl, mesityl, and m-quarterphenyl. Additionally, the aryl group may be optionally substituted.
Heterocyclic groups or heterocycle—as used herein include non-aromatic cyclic groups. Non-aromatic heterocyclic groups include saturated heterocyclic groups having 3 to 20 ring atoms and unsaturated non-aromatic heterocyclic groups having 3 to 20 ring atoms, where at least one ring atom is selected from the group consisting of a nitrogen atom, an oxygen atom, a sulfur atom, a selenium atom, a silicon atom, a phosphorus atom, a germanium atom, and a boron atom. Preferred non-aromatic heterocyclic groups are those having 3 to 7 ring atoms, each of which includes at least one hetero-atom such as nitrogen, oxygen, silicon, or sulfur. Examples of non-aromatic heterocyclic groups include oxiranyl, oxetanyl, tetrahydrofuranyl, tetrahydropyranyl, dioxolanyl, dioxanyl, aziridinyl, dihydropyrrolyl, tetrahydropyrrolyl, piperidinyl, oxazolidinyl, morpholinyl, piperazinyl, oxepinyl, thiepinyl, azepinyl, and tetrahydrosilolyl. Additionally, the heterocyclic group may be optionally substituted.
Heteroaryl—as used herein, includes non-condensed and condensed hetero-aromatic groups having 1 to 5 hetero-atoms, where at least one hetero-atom is selected from the group consisting of a nitrogen atom, an oxygen atom, a sulfur atom, a selenium atom, a silicon atom, a phosphorus atom, a germanium atom, and a boron atom. A hetero-aromatic group is also referred to as heteroaryl. Heteroaryl may be those having 3 to 30 carbon atoms, preferably those having 3 to 20 carbon atoms, and more preferably those having 3 to 12 carbon atoms. Suitable heteroaryl groups include dibenzothiophene, dibenzofuran, dibenzoselenophene, furan, thiophene, benzofuran, benzothiophene, benzoselenophene, carbazole, indolocarbazole, pyridoindole, pyrrolodipyridine, pyrazole, imidazole, triazole, oxazole, thiazole, oxadiazole, oxatriazole, dioxazole, thiadiazole, pyridine, pyridazine, pyrimidine, pyrazine, triazine, oxazine, oxathiazine, oxadiazine, indole, benzimidazole, indazole, indoxazine, benzoxazole, benzisoxazole, benzothiazole, quinoline, isoquinoline, cinnoline, quinazoline, quinoxaline, naphthyridine, phthalazine, pteridine, xanthene, acridine, phenazine, phenothiazine, benzofuropyridine, furodipyridine, benzothienopyridine, thienodipyridine, benzoselenophenopyridine, and selenophenodipyridine, preferably dibenzothiophene, dibenzofuran, dibenzoselenophene, carbazole, indolocarbazole, imidazole, pyridine, triazine, benzimidazole, 1,2-azaborine, 1,3-azaborine, 1,4-azaborine, borazine, and aza-analogs thereof. Additionally, the heteroaryl group may be optionally substituted.
Alkoxy—as used herein, is represented by -O-alkyl, -O-cycloalkyl, -O-heteroalkyl, or -O-heterocyclic group. Examples and preferred examples of alkyl, cycloalkyl, heteroalkyl, and heterocyclic groups are the same as those described above. Alkoxy groups may be those having 1 to 20 carbon atoms, preferably those having 1 to 6 carbon atoms. Examples of alkoxy groups include methoxy, ethoxy, propoxy, butoxy, pentyloxy, hexyloxy, cyclopropyloxy, cyclobutyloxy, cyclopentyloxy, cyclohexyloxy, tetrahydrofuranyloxy, tetrahydropyranyloxy, methoxypropyloxy, ethoxyethyloxy, methoxymethyloxy, and ethoxymethyloxy. Additionally, the alkoxy group may be optionally substituted.
Aryloxy—as used herein, is represented by -O-aryl or -O-heteroaryl. Examples and preferred examples of aryl and heteroaryl are the same as those described above. Aryloxy groups may be those having 6 to 30 carbon atoms, preferably those having 6 to 20 carbon atoms. Examples of aryloxy groups include phenoxy and biphenyloxy. Additionally, the aryloxy group may be optionally substituted.
Arylalkyl—as used herein, contemplates alkyl substituted with an aryl group. Arylalkyl may be those having 7 to 30 carbon atoms, preferably those having 7 to 20 carbon atoms, and more preferably those having 7 to 13 carbon atoms. Examples of arylalkyl groups include benzyl, 1-phenylethyl, 2-phenylethyl, 1-phenylisopropyl, 2-phenylisopropyl, phenyl-t-butyl, alpha-naphthylmethyl, 1-alpha-naphthylethyl, 2-alpha-naphthylethyl, 1-alpha-naphthylisopropyl, 2-alpha-naphthylisopropyl, beta-naphthylmethyl, 1-beta-naphthylethyl, 2-beta-naphthylethyl, 1-beta-naphthylisopropyl, 2-beta-naphthylisopropyl, p-methylbenzyl, m-methylbenzyl, o-methylbenzyl, p-chlorobenzyl, m-chlorobenzyl, o-chlorobenzyl, p-bromobenzyl, m-bromobenzyl, o-bromobenzyl, p-iodobenzyl, m-iodobenzyl, o-iodobenzyl, p-hydroxybenzyl, m-hydroxybenzyl, o-hydroxybenzyl, p-aminobenzyl, m-aminobenzyl, o-aminobenzyl, p-nitrobenzyl, m-nitrobenzyl, o-nitrobenzyl, p-cyanobenzyl, m-cyanobenzyl, o-cyanobenzyl, 1-hydroxy-2-phenylisopropyl, and 1-chloro-2-phenylisopropyl. Of the above, preferred are benzyl, p-cyanobenzyl, m-cyanobenzyl, o-cyanobenzyl, 1-phenylethyl, 2-phenylethyl, 1-phenylisopropyl, and 2-phenylisopropyl. Additionally, the arylalkyl group may be optionally substituted.
Alkylsilyl—as used herein, contemplates a silyl group substituted with an alkyl group. Alkylsilyl groups may be those having 3 to 20 carbon atoms, preferably those having 3 to 10 carbon atoms. Examples of alkylsilyl groups include trimethylsilyl, triethylsilyl, methyldiethylsilyl, ethyldimethylsilyl, tripropylsilyl, tributylsilyl, triisopropylsilyl, methyldiisopropylsilyl, dimethylisopropylsilyl, tri-t-butylsilyl, triisobutylsilyl, dimethyl t-butylsilyl, and methyldi-t-butylsilyl. Additionally, the alkylsilyl group may be optionally substituted.
Arylsilyl—as used herein, contemplates a silyl group substituted with an aryl group. Arylsilyl groups may be those having 6 to 30 carbon atoms, preferably those having 8 to 20 carbon atoms. Examples of arylsilyl groups include triphenylsilyl, phenyldibiphenylylsilyl, diphenylbiphenylsilyl, phenyldiethylsilyl, diphenylethylsilyl, phenyldimethylsilyl, diphenylmethylsilyl, phenyldiisopropylsilyl, diphenylisopropylsilyl, diphenylbutylsilyl, diphenylisobutylsilyl, diphenyl t-butylsilyl. Additionally, the arylsilyl group may be optionally substituted.
Alkylgermanyl—as used herein contemplates germanyl substituted with an alkyl group. The alkylgermanyl may be those having 3 to 20 carbon atoms, preferably those having 3 to 10 carbon atoms. Examples of alkylgermanyl include trimethylgermanyl, triethylgermanyl, methyldiethylgermanyl, ethyldimethylgermanyl, tripropylgermanyl, tributylgermanyl, triisopropylgermanyl, methyldiisopropylgermanyl, dimethylisopropylgermanyl, tri-t-butylgermanyl, triisobutylgermanyl, dimethyl-t-butylgermanyl, and methyldi-t-butylgermanyl. Additionally, the alkylgermanyl may be optionally substituted.
Arylgermanyl—as used herein contemplates a germanyl substituted with at least one aryl group or heteroaryl group. Arylgermanyl may be those having 6 to 30 carbon atoms, preferably those having 8 to 20 carbon atoms. Examples of arylgermanyl include triphenylgermanyl, phenyldibiphenylylgermanyl, diphenylbiphenylgermanyl, phenyldiethylgermanyl, diphenylethylgermanyl, phenyldimethylgermanyl, diphenylmethylgermanyl, phenyldiisopropylgermanyl, diphenylisopropylgermanyl, diphenylbutylgermanyl, diphenylisobutylgermanyl, and diphenyl-t-butylgermanyl. Additionally, the arylgermanyl may be optionally substituted.
The term “aza” in azadibenzofuran, azadibenzothiophene, etc. means that one or more of C—H groups in the respective aromatic fragment are replaced by a nitrogen atom. For example, azatriphenylene encompasses dibenzo[f,h]quinoxaline, dibenzo[f,h]quinoline and other analogs with two or more nitrogens in the ring system. One of ordinary skill in the art can readily envision other nitrogen analogs of the aza-derivatives described above, and all such analogs are intended to be encompassed by the terms as set forth herein.
In the present disclosure, unless otherwise defined, when any term of the group consisting of substituted alkyl, substituted cycloalkyl, substituted heteroalkyl, substituted heterocyclic group, substituted arylalkyl, substituted alkoxy, substituted aryloxy, substituted alkenyl, substituted alkynyl, substituted aryl, substituted heteroaryl, substituted alkylsilyl, substituted arylsilyl, substituted alkylgermanyl, substituted arylgermanyl, substituted amino, substituted acyl, substituted carbonyl, a substituted carboxylic acid group, a substituted ester group, substituted sulfinyl, substituted sulfonyl, and substituted phosphino is used, it means that any group of alkyl, cycloalkyl, heteroalkyl, heterocyclic group, arylalkyl, alkoxy, aryloxy, alkenyl, alkynyl, aryl, heteroaryl, alkylsilyl, arylsilyl, alkylgermanyl, arylgermanyl, amino, acyl, carbonyl, a carboxylic acid group, an ester group, sulfinyl, sulfonyl, and phosphino may be substituted with one or more moieties selected from the group consisting of deuterium, halogen, unsubstituted alkyl having 1 to 20 carbon atoms, unsubstituted cycloalkyl having 3 to 20 ring carbon atoms, unsubstituted heteroalkyl having 1 to 20 carbon atoms, an unsubstituted heterocyclic group having 3 to 20 ring atoms, unsubstituted arylalkyl having 7 to 30 carbon atoms, unsubstituted alkoxy having 1 to 20 carbon atoms, unsubstituted aryloxy having 6 to 30 carbon atoms, unsubstituted alkenyl having 2 to 20 carbon atoms, unsubstituted alkynyl having 2 to 20 carbon atoms, unsubstituted aryl having 6 to 30 carbon atoms, unsubstituted heteroaryl having 3 to 30 carbon atoms, unsubstituted alkylsilyl having 3 to 20 carbon atoms, unsubstituted arylsilyl having 6 to 20 carbon atoms, unsubstituted alkylgermanyl having 3 to 20 carbon atoms, unsubstituted arylgermanyl group having 6 to 20 carbon atoms, unsubstituted amino having 0 to 20 carbon atoms, an acyl group, a carbonyl group, a carboxylic acid group, an ester group, a cyano group, an isocyano group, a hydroxyl group, a sulfanyl group, a sulfinyl group, a sulfonyl group, a phosphino group, and combinations thereof.
It is to be 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. phenyl, phenylene, naphthyl, dibenzofuryl) or as if it were the whole molecule (e.g. benzene, naphthalene, dibenzofuran). As used herein, these different ways of designating a substituent or an attached fragment are considered to be equivalent.
In the compounds mentioned in the present disclosure, hydrogen atoms may be partially or fully replaced by deuterium. Other atoms such as carbon and nitrogen may also be replaced by their other stable isotopes. The replacement by other stable isotopes in the compounds may be preferred due to its enhancements of device efficiency and stability.
In the compounds mentioned in the present disclosure, multiple substitution refers to a range that includes a di-substitution, up to the maximum available substitution. When substitution in the compounds mentioned in the present disclosure represents multiple substitution (including di-, tri-, and tetra-substitutions, etc.), that means the substituent may exist at a plurality of available substitution positions on its linking structure, the substituents present at a plurality of available substitution positions may be the same structure or different structures.
In the compounds mentioned in the present disclosure, adjacent substituents in the compounds cannot be joined to form a ring unless otherwise explicitly defined, for example, adjacent substituents can be optionally joined to form a ring. In the compounds mentioned in the present disclosure, the expression that adjacent substituents can be optionally joined to form a ring includes a case where adjacent substituents may be joined to form a ring and a case where adjacent substituents are not joined to form a ring. When adjacent substituents can be optionally joined to form a ring, the ring formed may be monocyclic or polycyclic (including spirocyclic, endocyclic, fusedcyclic, and etc.), as well as alicyclic, heteroalicyclic, aromatic, or heteroaromatic. In such expression, adjacent substituents may refer to substituents bonded to the same atom, substituents bonded to carbon atoms which are directly bonded to each other, or substituents bonded to carbon atoms which are more distant from each other. Preferably, adjacent substituents refer to substituents bonded to the same carbon atom and substituents bonded to carbon atoms which are directly bonded to each other.
The expression that adjacent substituents can be optionally joined to form a ring is also intended to mean that two substituents bonded to the same carbon atom are joined to each other via a chemical bond to form a ring, which can be exemplified by the following formula:
The expression that adjacent substituents can be optionally joined to form a ring is also intended to mean that two substituents bonded to carbon atoms which are directly bonded to each other are joined to each other via a chemical bond to form a ring, which can be exemplified by the following formula:
The expression that adjacent substituents can be optionally joined to form a ring is also intended to mean that two substituents bonded to a further distant carbon atom are joined to each other via a chemical bond to form a ring, which can be exemplified by the following formula:
Furthermore, the expression that adjacent substituents can be optionally joined to form a ring is also intended to mean that, in the case where one of the two substituents bonded to carbon atoms which are directly bonded to each other represents hydrogen, the second substituent is bonded at a position at which the hydrogen atom is bonded, thereby forming a ring. This is exemplified by the following formula:
According to an embodiment of the present disclosure, disclosed is a top-emission organic electroluminescent device, which comprises:
According to an embodiment of the present disclosure, disclosed is a top-emission organic electroluminescent device, which comprises a first anode; a first multi-stack cathode; and a first hole transporting region, a first emissive layer and a first electron transporting region that are disposed between the first anode and the first multi-stack cathode;
According to an embodiment of the present disclosure, disclosed is a top-emission organic electroluminescent device, which comprises a cathode, an anode and an emissive layer disposed between the cathode and the anode;
In this embodiment, the exciton recombination region is obtained via determination on a bottom-emission device having the same device structure as the top-emission device. For a specific test method, reference is made to an explanation of the term “exciton recombination peak position” in the present application.
According to an embodiment of the present disclosure, the first anode/anode has a reflectivity of greater than or equal to 85% at 550 nm.
According to an embodiment of the present disclosure, the first anode/anode has a reflectivity of greater than or equal to 90% at 550 nm.
According to an embodiment of the present disclosure, the first anode/anode has a reflectivity of greater than or equal to 95% at 550 nm.
According to an embodiment of the present disclosure, the first anode/anode is selected from the group consisting of the following materials: silver, aluminum, titanium, nickel, platinum, a combination of silver, aluminum, titanium, nickel or platinum and indium tin oxide (ITO), indium zinc oxide (IZO), molybdenum oxide (MoOx) or titanium nitride (TiN), and combinations thereof.
According to an embodiment of the present disclosure, the second anode has a transmittance of greater than or equal to 80% at 550 nm.
According to an embodiment of the present disclosure, the second anode has a transmittance of greater than or equal to 84% at 550 nm.
According to an embodiment of the present disclosure, the second anode has a transmittance of greater than or equal to 89% at 550 nm.
According to an embodiment of the present disclosure, the second anode is selected from the group consisting of the following materials: indium tin oxide (ITO), indium zinc oxide (IZO), molybdenum oxide (MoOx) and combinations thereof.
According to an embodiment of the present disclosure, when 500 nm≤λmax≤600 nm, the second anode is ITO with a thickness of greater than or equal to 700 Å and less than or equal to 900 Å.
According to an embodiment of the present disclosure, when 600 nm<λmax≤700 nm, the second anode is ITO with a thickness range of greater than or equal to 1100 Å and less than or equal to 1300 Å.
According to an embodiment of the present disclosure, the exciton recombination peak position is located in the emissive layer within a region less than 50% of the thickness of the emissive layer from the side close to the anode.
According to an embodiment of the present disclosure, the exciton recombination peak position is located in the emissive layer within a region less than 40% of the thickness of the emissive layer from the side close to the anode.
According to an embodiment of the present disclosure, the exciton recombination peak position is located in the emissive layer within a region less than 30% of the thickness of the emissive layer from the side close to the anode.
According to an embodiment of the present disclosure, the exciton recombination peak position is located in the emissive layer within a region greater than 2.5% of the thickness of the emissive layer from the side close to the anode.
According to an embodiment of the present disclosure, the exciton recombination peak position is located in the emissive layer within a region greater than 5% of the thickness of the emissive layer from the side close to the anode.
According to an embodiment of the present disclosure, the exciton recombination peak position is located in the emissive layer within a region greater than 7.5% of the thickness of the emissive layer from the side close to the anode.
According to an embodiment of the present disclosure, a distance between the exciton recombination peak position and the interface of the emissive layer on the side close to the anode is greater than 1 nm.
According to an embodiment of the present disclosure, the distance between the exciton recombination peak position and the interface of the emissive layer on the side close to the anode is greater than 3 nm.
According to an embodiment of the present disclosure, when 500 nm≤λmax≤600 nm, E≥1.640; preferably, E≥1.660.
According to an embodiment of the present disclosure, when 600 nm<λmax≤700 nm, E≥1.900; preferably, E≥2.000.
According to an embodiment of the present disclosure, when 500 nm≤λmax≤600 nm, a full width at half maximum of the photoluminescence spectrum of the emissive doped material is less than or equal to 53 nm, or less than or equal to 45 nm, or less than or equal to 40 nm, or less than or equal to 35 nm.
According to an embodiment of the present disclosure, when 600 nm<λmax≤700 nm, a full width at half maximum of the photoluminescence spectrum of the emissive doped material is less than or equal to 50 nm, or less than or equal to 40 nm, or less than or equal to 35 nm, or less than or equal to 30 nm.
According to an embodiment of the present disclosure, Jo is greater than 5 mA/cm2 and less than or equal to 50 mA/cm2.
According to an embodiment of the present disclosure, Jo is greater than 5 mA/cm2 and less than or equal to 35 mA/cm2.
According to an embodiment of the present disclosure, Jo is greater than 5 mA/cm2 and less than or equal to 15 mA/cm2.
According to an embodiment of the present disclosure, Jo is greater than 1 mA/cm2 and less than or equal to 50 mA/cm2.
According to an embodiment of the present disclosure, Jo is greater than 3 mA/cm2 and less than or equal to 35 mA/cm2.
According to an embodiment of the present disclosure, Jo is greater than 5 mA/cm2 and less than or equal to 15 mA/cm2.
According to an embodiment of the disclosure, when 500 nm≤λmax≤600 nm, under a condition that Jo is 10 mA/cm2, EQEB≥23.0%.
According to an embodiment of the present disclosure, when 600 nm<λmax≤700 nm, under the condition that Jo is 10 mA/cm2, EQEB≥24.0%.
According to an embodiment of the disclosure, when 500 nm≤λmax≤600 nm, under a condition that Jo is 10 mA/cm2, EQEA≥37.0%.
According to an embodiment of the present disclosure, when 600 nm<λmax≤700 nm, under the condition that Jo is 10 mA/cm2, EQEA≥50%.
According to an embodiment of the present disclosure, the emissive layer further comprises a first host material and/or a second host material.
According to an embodiment of the present disclosure, the emissive layer further comprises a first host material and/or a second host material, wherein the first host material is a p-type host material, and the second host material is an n-type material.
According to an embodiment of the present disclosure, when 500 nm≤λmax≤600 nm, an HOMO energy level of the emissive doped material <−5.100 eV.
According to an embodiment of the present disclosure, when 600 nm<λmax≤700 nm, the HOMO energy level of the emissive doped material <−5.110 eV.
According to an embodiment of the present disclosure, the first hole transporting region further comprises a first hole injection layer, a first hole transporting layer and/or a first electron blocking layer, and the second hole transporting region further comprises a first hole injection layer, a second hole transporting layer and/or a first electron blocking layer, wherein the first hole transporting layer and the second hole transporting layer comprise the same material type and doping proportion and only differs in thickness.
According to an embodiment of the present disclosure, the first hole transporting region further comprises a first hole injection layer, a first hole transporting layer and/or a first electron blocking layer, and the second hole transporting region further comprises a first hole injection layer, a first hole transporting layer and/or a second electron blocking layer, wherein the first electron blocking layer and the second electron blocking layer comprise the same material type and doping proportion and only differs in thickness.
According to an embodiment of the present disclosure, the first hole injection layer further comprises a p-type conductive doped material.
According to an embodiment of the present disclosure, disclosed is a display assembly, which comprises the top-emission organic electroluminescent device in any one of the preceding embodiments.
According to an embodiment of the present disclosure, further disclosed is a use of the top-emission organic electroluminescent device in any one of the preceding embodiments in an electronic device, an electronic element module, a display device or a lighting device.
According to an embodiment of the present disclosure, the emissive doped material has a general formula of M(La)m(Lb)n(Lc)q;
m is 1, 2 or 3, n is 0, 1 or 2, q is 0, 1 or 2, and m+n+q is equal to an oxidation state of the metal M; when m is greater than or equal to 2, a plurality of La may be identical or different; when n is 2, two Lb may be identical or different; when q is 2, two Lc may be identical or different;
the ligand La has a structure represented by Formula 1 or Formula 2:
‘------ ’ represents a position where the ligand La is coordinated to the metal M.
In the present disclosure, the expression that “in Formula 1, adjacent substituents R′, R1 and R2 can be optionally joined to form a ring” is intended to mean that any one or more of groups of adjacent substituents, such as two substituents R′, two substituents R1, two substituents R2, substituents R′ and R1, substituents R′ and R2, and substituents R1 and R2, can be joined to form a ring. Obviously, it is also possible that none of these substituents are joined to form a ring.
In the present disclosure, the expression that “in Formula 2, adjacent substituents RA and RB can be optionally joined to form a ring” is intended to mean that any one or more of groups of adjacent substituents, such as two substituents RA, two substituents RB, and substituents RA and RB, can be joined to form a ring. Obviously, it is also possible that none of these substituents are joined to form a ring.
According to an embodiment of the present disclosure, the ligands Lb and Lc are, at each occurrence identically or differently, selected from any one or two of the following structures:
In the present disclosure, the expression that “adjacent substituents Ra, Rb, Rc, RN1, RN2, RC1 and RC2 can be optionally joined to form a ring” is intended to mean that any one or more of groups of adjacent substituents, such as two substituents Ra, two substituents Rb, two substituents Rc, substituents Ra and Rb, substituents Ra and Rc, substituents Rb and Rc, substituents Ra and RN1, substituents Rb and RN1, substituents Ra and RC1, substituents Ra and RC2, substituents Rb and RC1, substituents Rb and RC2, and substituents RC1 and RC2, can be joined to form a ring. Obviously, it is also possible that none of these substituents are joined to form a ring.
According to an embodiment of the present disclosure, Cy is any structure selected from the group consisting of:
In the present disclosure, the expression that “two adjacent substituents R can be optionally joined to form a ring” is intended to mean that any one or more of groups of any two adjacent substituents R can be joined to form a ring. Obviously, it is also possible that none of these substituents are joined to form a ring.
According to an embodiment of the present disclosure, the ligand La has a structure represented by any one of Formula 1-1 and Formulas 2-1 to 2-3:
In the present disclosure, the expression that “in Formula 1-1, adjacent substituents R′, Rz, R1 and R2 can be optionally joined to form a ring” is intended to mean that any one or more of groups of adjacent substituents, such as two substituents R′, two substituents Rz, two substituents R1, two substituents R2, substituents R′ and R1, substituents R′ and R2, and substituents R1 and R2, can be joined to form a ring. Obviously, it is also possible that none of these substituents are joined to form a ring.
In the present disclosure, the expression that “in Formulas 2-1 to 2-3, adjacent substituents R′ and Ry can be optionally joined to form a ring” is intended to mean that any one or more of groups of adjacent substituents, such as two substituents R′, two substituents Ry, and substituents R′ and Ry, can be joined to form a ring. Obviously, it is also possible that none of these substituents are joined to form a ring.
According to an embodiment of the present disclosure, the emissive doped material is selected from the group consisting of the following compounds which are included without limitation:
In the present disclosure, a bottom-emission device having the “same” device structure as a top-emission device, or the reference that a bottom-emission device and a top-emission device are “same” in device structure, or other expressions with the same meaning, mean that the bottom-emission device and the top-emission device have the same material layers between the anode and the multi-stack cathode, that is, have the same number of layers, thickness, the same materials and doping proportions, except for a thickness of a material layer for adjusting a microcavity in the top-emission device, which is different due to a microcavity effect. The material layer for adjusting the microcavity is generally a hole transporting layer (HTL) and/or an electron blocking layer (EBL). For example, if the structure of the top-emission device is: first anode/first hole transporting region/first emissive layer/first electron transporting region/first multi-stack cathode, then the device structure of the bottom-emission device having the “same” device structure as the top-emission device is: second anode/second hole transporting region/first emissive layer/first electron transporting region/second multi-stack cathode, wherein material types and doping proportions of each layer of the first hole transporting region and the second hole transporting region are exactly the same, except for the thickness of the material layer for adjusting the microcavity; the top-emission device and the bottom-emission device have exactly the same first emissive layer, and the top-emission device and the bottom-emission device have exactly the same first electron transporting region, both of which may comprise the same one or more organic layers with the same material type, and when the organic layer is formed of two or more materials, the two or more materials also have the same doping (mass) proportion.
The device structure of the top-emission device is the same as the device structure of the bottom-emission device. However, requirements for the electrodes are different due to different light emission directions of the bottom-emission device and the top-emission device. Top-emitted light is emitted from the cathode of the device so that the cathode is required to have a relatively high transmittance, while bottom-emitted light is emitted from the anode of the device so that the anode is required to have a relatively high transmittance. In the bottom-emission device, the anode is generally a transparent or translucent material, including but not limited to ITO, IZO and MoOx (molybdenum oxide), and the material generally has a transparency of greater than 50%; preferably, the transparency is greater than 70%; the cathode is generally a material having a high reflectivity, including but not limited to Al and Ag, and the reflectivity is greater than 70%; preferably, the reflectivity is greater than 90%. In the top-emission device, the anode is generally a material or a combination of materials having a high reflectivity, including but not limited to Ag, Ti, Cr, Pt, Ni, TiN and a combination of the above materials with ITO and/or MoOx (molybdenum oxide), and the reflectivity is generally greater than 50%; preferably, the reflectivity is greater than 80%; more preferably, the reflectivity is greater than 90%; the cathode is generally a translucent or transparent conductive material, including but not limited to a MgAg alloy, MoOx, Yb, Ca, ITO, IZO or a combination thereof, and the conductive material generally has a transparency of greater than 30%; preferably, the transparency is greater than 50%.
The term “exactly the same” in the organic layers or the regions means that the organic materials used in the organic layers or the regions are of the same type. If the organic layer is composed of two or more materials, not only the two or more materials are the same, but also the doping proportions are substantially the same (an error of the doping proportion is within +/−5%, that is, the doping proportion is fluctuated ranging from 95% to 105% of a set doping proportion), and the thicknesses of the organic layers or the regions are also substantially the same (an error of the thicknesses of the organic layers or the regions is within +/−5%, that is, the thickness is fluctuated ranging from 95% to 105% of a set thickness). Here, “the organic materials are of the same type” means that the organic materials have the same chemical structural formula.
Herein, values of highest occupied molecular orbital (HOMO) energy levels and lowest unoccupied molecular orbital (LUMO) energy levels of all the compounds are measured through a cyclic voltammetry (CV) method. The test is conducted using an electrochemical workstation modelled CorrTest CS120 produced by Wuhan Corrtest Instruments Corp., Ltd and using a three-electrode working system where a platinum disk electrode serves as a working electrode, a Ag/AgNO3 electrode serves as a reference electrode, and a platinum wire electrode serves as an auxiliary electrode. The test is conducted at 25° C., anhydrous DMF is used as a solvent, 0.1 mol/L of tetrabutylammonium hexafluorophosphate is used as a supporting electrolyte, a compound to be tested is prepared into a solution of 10−3 mol/L, and nitrogen is introduced into the solution for 10 min for oxygen removal before the test. The parameters of the instrument are set as follows: a scan rate of 100 mV/s, a potential interval of 0.5 mV, and a test window of 1 V to −0.5 V. Herein, all the “HOMO energy levels” and “LUMO energy levels” are represented by negative values. The smaller the value (that is, the larger the absolute value), the deeper the energy level, and the larger the value (that is, the smaller the absolute value), the shallower the energy level.
Herein, “multi-stack cathode” refers to a multi-stack layer composed of a cathode and an organic layer in contact with the cathode. In the top-emission device, “multi-stack cathode” or “first multi-stack cathode” refers to a multi-stack layer composed of a cathode, an EIL and a capping layer (CPL). In the bottom-emission device, “multi-stack cathode” or “second multi-stack cathode” refers to a multi-stack layer composed of a cathode and an EIL. For example, structures of the multi-stack cathodes in the top-emission device and the bottom-emission device are schematically shown in the examples of the present application without limitation, respectively. Among which, the multi-stack cathode in the top-emission is prepared as “metal ytterbium (Yb) with a thickness of 10 Å is firstly evaporated as the electron injection layer (EIL), on which both metal magnesium (Mg) and metal silver (Ag) are simultaneously evaporated as the cathode (10:90, 140 Å), and then on which Compound CPL is evaporated as the capping layer (CPL, 650 Å), whereby the multi-stack structure is formed”. Transmittances of the two-layer structure of Yb 10 Å/Mg:Ag (10:90, 140 Å) in the multi-stack cathode are shown in Table 1, and optical refractive indexes (n values) of the CPL material layer with a thickness of 700 Å at specific wavelength bands are shown in Table 2. The multi-stack cathode in the bottom-emission device is prepared as “Compound Liq with a thickness of 10 Å is firstly evaporated as the electron injection layer (EIL), and then on which metal aluminum (Al) is evaporated as the cathode (1200 Å), whereby the multi-stack structure is formed”. Those skilled in the art may adjust the composition of the multi-stack cathode as needed. For example, a translucent material or combination is selected as the cathode of the top-emission device, such as a MgAg alloy, MoOx, Yb, Ca, ITO, IZO or combinations thereof; a material or a combination having a relatively high reflectivity is selected as the cathode of the bottom-emission device, such as Ag, Ti, Cr, Pt, Ni, TiN and a combination of the above materials with ITO and/or MoOx; a material or a combination of materials having a refractive index of greater than 1.8 in a region of visible light is generally selected as the CPL material. Suitable materials may be selected as the EIL layers in the above “first multi-stack cathode” and “second multi-stack cathode” as needed.
A method for testing the transmittance of the above-mentioned Yb 10 Å/Mg:Ag (10:90, 140 Å) thin film is as follows: on a quartz plate, metal ytterbium (Yb) with a thickness of 10 Å is firstly evaporated, on which both metal magnesium (Mg) and metal silver (Ag) are simultaneously evaporated as the cathode (10:90, 140 Å), whereby the two-layer structure Yb/Mg:Ag is formed; the test is conducted using an ultraviolet spectrophotometer (modelled UV7600) of SHANGHAI LENGGUANG TECH. CO., LTD to obtain transmittance values at a full wavelength; after three tests, an average value of the transmittances corresponding to 460 nm, 530 nm and 620 nm is taken.
A method for testing the optical refractive index (n value) of the above-mentioned CPL material is as follows: on a silicon wafer, a sample 700 Å thin film is evaporated in an evaporation chamber; the test is conducted using an ellipsometer (modelled ESNano) of BEIJING ELLITOP TECH. CO., LTD to obtain the refractive index n value; after three tests, an average value of the refractive indexes corresponding to 460 nm, 530 nm and 620 nm is taken.
Herein, a method for testing the maximum emission wavelength λmax and the full width at half maximum data of the photoluminescence spectrum of the organic emissive doped material is as follows: an organic emissive doped material sample is prepared into a solution with a concentration of 1×10−6 mol/L by using HPLC-grade of toluene, nitrogen is purged into the prepared solution for five minutes to remove oxygen, the solution is excited with light at a wavelength of 400 nm at room temperature (298 K), a luminescence spectrum of the solution is measured, and spectrum information is directly read from the spectrum, as shown in Table 3. The test instrument is a fluorescence spectrophotometer modelled LENGGUANG F98 produced by SHANGHAI LENGGUANG TECH. CO., LTD.
Herein, “efficiency conversion rate E” refers to a conversion rate between the maximum external quantum efficiency EQEA of the top-emission device and the maximum external quantum efficiency EQEB of the bottom-emission device having the same device structure as the top-emission device at the same current density Jo, that is, the efficiency conversion rate E=EQEA/EQEB. In the top-emission device, an emissive doped material adjusts the microcavity by adjusting a thickness of a film of the HTL or the EBL or a combination of the two layers and obtains the maximum external quantum efficiency EQEA; the same emissive doped material is used in the same bottom-emission device as the top-emission device, in this case, second external quantum efficiency measured at the current density Jo is EQEB, and 1 mA/cm2<Jo≤50 mA/cm2; preferably, 3 mA/cm2<Jo≤35 mA/cm2; more preferably, 5 mA/cm2<Jo≤15 mA/cm2.
Herein, “exciton recombination peak position” refers to a ratio of a position d of a probe layer where the exciton fraction achieves a maximum value to a total thickness of an EML, wherein d represents a distance between an interface (the interface refers to an interface between a layer contacted to the EML on the side of the anode and the EML) and the position of the probe layer. The layer contacted to the EML on the side of the anode includes, but is not limited to, the HTL or the EBL. “Exciton fraction” refers to a ratio of the number of excitons at a certain position in the emissive layer to the total number of excitons in the emissive layer. The exciton fraction reflects how much exciton recombination occurs within a diffusion length of the probe layer and can be used for characterizing a relative relationship of the exciton distribution of the device. The exciton fraction can be calculated according to electroluminescence (EL) spectrum data. Using
The probe layer mentioned in the above test of exciton recombination peak position generally comprises a probe material, which is generally selected from an emissive doped material which is similar to the emissive doped material in the EML in energy level and electrical performance but red-shifted compared to the maximum emission wavelength of the emissive doped material in the EML. Preferably, an emissive doped material with a maximum emission wavelength red-shifted at least 30 nm is selected as the probe material. Through the comparison of spectral intensities of the device in the case of the presence or absence of a probe at each specific position in the emissive layer, exciton fractions at corresponding positions of the EML are calculated, and the exciton recombination peak position is determined. The top-emission device and the bottom-emission device of the present application are schematically used as an example without limitation. In the present application, in Bottom-emission Devices 1-1 to 1-9, an emissive doped material with a maximum emission wavelength λmax of greater than or equal to 500 nm and less than or equal to 600 nm is used, and a probe layer of the device is composed of an emissive layer and a probe material RD01 in the device to be tested, wherein RD01 (a peak wavelength of a photoluminescence spectrum is 620 nm) has a doping proportion of 1%. In Bottom-emission Device 1-10 of the present application, an emissive doped material with a maximum emission wavelength λmax of greater than 600 nm and less than or equal to 700 nm is used, and a probe layer of the device is composed of an emissive layer and a probe material (RD02) in the device to be tested, wherein RD02 (a peak wavelength of a photoluminescence spectrum is 649 nm) has a doping proportion of 1%. The exciton fraction can be calculated according to a peak wavelength intensity of the probe material in an electroluminescence (EL) spectrum of the device with the probe layer.
In the case where the top-emission device and the bottom-emission device have the same device structure, the exciton recombination peak position of the bottom-emission device is tested, which may characterize the exciton recombination peak position of the corresponding top-emission device having the same device structure, or the exciton recombination peak position in the top-emission device may move slightly in an anode direction relative to the bottom-emission device tested. The microcavity effect is present in the top-emission device as previously mentioned. Therefore, the exciton recombination peak position in the device is generally tested in the bottom-emission device. When the exciton recombination region peak position in the bottom-emission device is within a certain range, the exciton recombination region peak position in the top-emission device also fluctuates within a small range corresponding to the exciton recombination region peak position in the bottom-emission device. Therefore, studying the exciton recombination region peak position of the bottom-emission device is an efficient and reliable means to study the performance of the top-emission device.
The exciton recombination peak position in the emissive layer of the device can be adjusted in multiple manners, such as a hole/electron injection layer, a hole/electron transporting layer and a hole/electron blocking layer. However, through researches, the inventor of the present application thinks that the EML plays a particularly important role in the exciton recombination position in the OLED device. The EML generally comprises a host material and an emissive doped material, wherein the host material generally comprises a p-type host material, an n-type host material or a bipolar host material according to transporting characteristics of the host material. The host material may be one or more types as needed, for example, two types of host material are comprised in the EML. The difference in transporting characteristic and energy level of the emissive doped material may also affect the transporting of carriers in the EML, thereby affecting the exciton recombination position. Therefore, proportions of multiple types of host material in the EML and a doping concentration of the emissive doped material can be adjusted so that the exciton recombination peak position in the EML is adjusted. For example, when the EML comprises two types of host material, which are the p-type host material and the n-type host material, respectively, a proportion of the p-type host material can be increased to improve a transporting capability of holes in the EML so that the exciton recombination region moves toward a side of the cathode; on the contrary, a proportion of the n-type host material can be increased to provide a transporting capability of electrons in the EML so that the exciton recombination region moves toward a side of the anode. In addition, if an emissive doped material with a very strong hole trapping capability is selected, holes transported to the EML will be quickly trapped by the emissive doped material, and the exciton recombination region will be close to the side of the anode; on the contrary, if the emissive doped material does not have a relatively strong hole trapping capability, the exciton recombination region will be far away from the side of the anode.
Although the top-emission device is a commercial device structure at present, since the top-emission device has an optical microcavity effect, intrinsic characteristics of the material (for example, the luminescence spectrum of the top-emission device cannot reflect intrinsic spectral characteristics of the emissive layer) are covered up, for the top-emission device, thicknesses of some organic layers need to be adjusted (for adjusting the microcavity) to perform a comprehensive evaluation of device performance, and finally, a device structure with the best device performance is obtained. Therefore, the top-emission device is used for evaluating the performance of a new material, thereby increasing the number of experiments and resulting in an increased and relatively high test cost, which is not the most suitable device structure for material screening. The bottom-emission device can well reflect the intrinsic characteristics of the material and is simple to prepare and low in cost so that the structure of the bottom-emission device is mostly used in the initial performance test and screening of the new material. Generally, research and development personnel generally perform preliminary screening on the performance of the new material by using the structure of the bottom-emission device first when developing the new material, and then use a potential material in the top-emission device to perform a performance evaluation to save the time and the cost.
Since organic electroluminescence is current-driven luminescence, quantum efficiency can effectively reflect the performance of the organic electroluminescence and is the most important parameter for measuring the device performance. EQE refers to a ratio of the number of photons finally emitted from the organic electroluminescent device to the number of injected carriers, which reflects the overall luminescence efficiency of the device and is one of the important parameters for evaluating the device performance. Therefore, it is very critical to study the efficiency conversion rate between the top-emission device and the bottom-emission device, which can significantly save the time and cost for material development and screening.
Through researches, the inventor of the present application has found that when the exciton recombination peak position of the bottom-emission device is in the emissive layer within a region greater than 0 and less than or equal to 65% of the thickness of the emissive layer from the side of the anode, the maximum external quantum efficiency conversion rate from the bottom-emission device to the top-emission device having the same device structure is higher, and in this case, the device performance of the top-emission device corresponding to the bottom-emission device can also reach an excellent level. While, for the bottom-emission device with the exciton recombination peak position in a region exceeding 65% of the thickness of the emissive layer from the side of the anode, the maximum external quantum efficiency conversion rate from the bottom-emission device to the top-emission device having the same device structure is lower, and the performance of the top-emission device corresponding to the bottom-emission device is also relatively poor. Moreover, even if EQE of bottom-emission devices is substantially the same in this case, for example, for a device whose EQE is 23% among the bottom-emission devices, if the exciton recombination peak position is controlled so that the maximum external quantum efficiency conversion rate E of the device is greater than 1.625, it can be predicted that the EQE of the top-emission having the same device structure will be greater than 23%*1.625=37%. That is, through researches, it is found in the present disclosure that when the exciton recombination peak position is located in the emissive layer within a region greater than 0% and less than or equal to 65% of the thickness of the emissive layer from the side close to the anode, for the emissive doped material whose maximum emission wavelength λmax is greater than or equal to 500 nm and less than or equal to 600 nm, the maximum external quantum efficiency conversion rate from the bottom-emission device to the top-emission device having the same device structure can reach 1.625 or more; for the emissive doped material whose λmax is greater than 600 nm and less than or equal to 700 nm, the maximum external quantum efficiency conversion rate from the bottom-emission device to the top-emission device having the same device structure can reach 1.850 or more. This means that a material system of the bottom-emission device can be directly used in the structure of the top-emission device and ideal device performance is obtained, thereby significantly reducing resources and time required for researchers to optimize the top-emission device, accelerating a progress of research and development and reducing a cost of research and development, which is of great significance to the commercial development of an OLED technology.
In the examples of devices, the characteristics of the devices were tested using conventional equipment in the art (including, but not limited to, evaporator produced by ANGSTROM ENGINEERING, optical testing system produced by SUZHOU FATAR, lifetime testing system produced by SUZHOU FATAR, and ellipsometer produced by BEIJING ELLITOP, etc.) by methods well-known to the persons skilled in the art. As the persons skilled in the art are aware of the above-mentioned equipment use, test methods, and other related contents, the inherent data of the sample can be obtained with certainty and without influence, so the above related contents are not further described in the present disclosure.
Hereinafter, the present disclosure is described in more detail with reference to the following examples. The compounds used in the following examples can be readily obtained by those skilled in the art, and therefore the synthesis methods thereof are not described here. Apparently, the following examples are only for the purpose of illustration and are not intended to limit the scope of the present disclosure. Based on the following examples, those skilled in the art can obtain other examples of the present disclosure by conducting improvements on these examples.
Bottom-emission Device 1-1: a green phosphorescent bottom-emission organic electroluminescent device 200 was prepared, as shown in
A glass substrate with a thickness of 0.7 mm was provided. On the glass substrate, indium tin oxide (ITO) with a thickness of 800 Å was pre-patterned for use as a second anode 210. Then, after the substrate was washed with deionized water and a detergent, a surface of ITO was treated with oxygen plasma and UV ozone. The substrate was dried in a glovebox to remove moisture, mounted on a holder and transferred into a vacuum chamber. Organic layers specified below were sequentially evaporated through vacuum thermal evaporation on the anode layer at a rate of 0.01 to 10 Å/s and a vacuum degree of about 10−6 Torr. Firstly, Compound HI was evaporated as a hole injection layer (HIL, 100 Å) 220, and Compound HT was evaporated as a hole transporting layer (HTL, 350 Å) 230. Then, Compound H1 was evaporated for use as an electron blocking layer (EBL, 50 Å) 240, on which Compound H1, Compound H2 and Compound GD-17 were simultaneously evaporated as a first emissive layer (EML, 48:48:4, 400 Å) 250, Compound H3 was evaporated as a hole blocking layer (HBL, 50 Å) 260, and Compounds ET and Liq were co-deposited as an electron transporting layer (ETL, 40:60, 350 Å) 270. Then, a second multi-stack cathode layer 280 was evaporated. Specifically, Compound Liq with a thickness of 10 Å was evaporated as an electron injection layer (EIL) 280a, and then metal aluminum (Al) was evaporated as a cathode (1200 Å) 280b. The device was transferred back to the glovebox and encapsulated with a glass lid 290 to complete the device.
The preparation method of Bottom-emission Device 1-2 was the same as that of Bottom-emission Device 1-1, except that in the emissive layer (EML), the ratio of Compound H1, Compound H2 and Compound GD-17 was 47:47:6.
The preparation method of Bottom-emission Device 1-3 was the same as that of Bottom-emission Device 1-1, except that Compound H1, Compound H2 and Compound GD-3 were simultaneously evaporated as the emissive layer and the ratio of Compound H1, Compound H2 and Compound GD-3 was 48:48:4.
The preparation method of Bottom-emission Device 1-4 was the same as that of Bottom-emission Device 1-3, except that in the emissive layer (EML), the ratio of Compound H1, Compound H2 and Compound GD-3 was 47:47:6.
The preparation method of Bottom-emission Device 1-5 was the same as that of Bottom-emission Device 1-1, except that in the emissive layer (EML), the ratio of Compound H1, Compound H2 and Compound GD-17 was 63:31:6.
The preparation method of Bottom-emission Device 1-6 was the same as that of Bottom-emission Device 1-3, except that in the emissive layer (EML), the ratio of Compound H1, Compound H2 and Compound GD-3 was 63:31:6.
The preparation method of Bottom-emission Device 1-7 was the same as that of Bottom-emission Device 1-1, except that Compound H1, Compound H2 and Compound GDA were simultaneously evaporated as the emissive layer and the ratio of Compound H1, Compound H2 and Compound GDA was 47:47:6.
The preparation method of Bottom-emission Device 1-8 was the same as that of Bottom-emission Device 1-7, except that in the emissive layer (EML), the ratio of Compound H1, Compound H2 and Compound GDA was 63:31:6.
The preparation method of Bottom-emission Device 1-9 was the same as that of Bottom-emission Device 1-7, except that in the emissive layer (EML), the ratio of Compound H1, Compound H2 and Compound GDA was 75:19:6.
Detailed structures and thicknesses of part of the devices of Bottom-emission Devices 1-1 to 1-9 are shown in Table 1. A layer using more than one material is obtained by doping different compounds at their weight ratio as recorded.
The structures of the compounds used in the devices are shown as follows:
Device performance of Bottom-emission Devices 1-1 to 1-9 is summarized in Table 5. The color coordinate CIE, the maximum emission peak wavelength λmax, the full width at half maximum FWHM and the maximum external quantum efficiency EQEB were measured at a current density of 10 mA/cm2. The exciton recombination peak position is a position in the emissive layer corresponding to a maximum exciton fraction obtained when the above Bottom-emission Devices 1-1 to 1-9 were tested.
As can be seen from the above device structures and device performance, through the adjustment of the emissive material in the emissive layer, the exciton recombination peak position can be adjusted. For example, the device structures of Bottom-emission Devices 1-2, 1-4 and 1-7 differ only in different emissive doped materials, while their exciton recombination peaks are differently positioned in the emissive layers. Similarly, through the adjustment of the mass ratio of the host material and the doped material in the emissive layer (including a mass ratio of two host materials), the exciton recombination peak position can also be adjusted. For example, through the comparison of Bottom-emission Devices 1-1, 1-2 and 1-5 and the comparison of Bottom-emission Devices 1-3, 1-4 and 1-6 show that they differ in different mass ratios of host materials and doped materials, while their exciton recombination peaks are differently positioned in the emissive layers.
As can be seen from the above Table 5, the exciton recombination peak positions measured for Bottom-emission Devices 1-1 to 1-4 are located in the emissive layer within a region greater than 0% and less than or equal to 65%, which are respectively at 25%, 25%, 25% and 50%, from the side close to the second anode. The exciton recombination peak positions measured for Bottom-emission Devices 1-5 to 1-9 are in a region outside the region of greater than 0 and less than or equal to 65% from the side of the emissive layer close to the second anode.
Top-emission Device Example: the following are Top-emission Device Examples having the “same” device structure in one-to-one correspondence with the above bottom-emission devices, that is, Top-emission Device 1-1 and the above Bottom-emission Device 1-1 have the “same” device structure, Top-emission Device 1-2 and the above Bottom-emission Device 1-2 have the “same” device structure, and it is true in other cases.
Top-emission Device 1-1: a green phosphorescent top-emission organic electroluminescent device 100 was prepared, as shown in
Firstly, a glass substrate with a thickness of 0.7 mm was provided. On the glass substrate, indium tin oxide (ITO) 75 Å/Ag 1500Å/ITO 150 Å was pre-patterned for use as a first anode 110. The substrate was dried in a glovebox to remove moisture, mounted on a holder and transferred into a vacuum chamber. Organic layers specified below were sequentially evaporated through vacuum thermal evaporation on the anode layer at a rate of 0.01 to 10 Å/s and a vacuum degree of about 10−6 Torr. Firstly, Compound HI was evaporated as a hole injection layer (HIL, 100 Å) 120, and Compound HT was evaporated as a hole transporting layer (HTL, ˜1400 Å) 130. The HTL was also used as a microcavity adjustment layer. The thickness of the HTL was adjusted to about 1400 Å to obtain a maximum value of external quantum efficiency EQE. Then, Compound H1 was evaporated for use as an electron blocking layer (EBL, 50 Å) 140, on which Compound H1, Compound H2 and Compound GD-17 were simultaneously evaporated as a first emissive layer (EML, 48:48:4, 400 Å) 150, Compound H3 was evaporated as a hole blocking layer (HBL, 50 Å) 160, and Compounds ET and Liq were co-deposited as an electron transporting layer (ETL, 40:60, 350 Å) 170. Then, a first multi-stack cathode layer 180 was evaporated. Specifically, metal ytterbium (Yb) with a thickness of 10 Å was evaporated as an electron injection layer (EIL) 180a, metal magnesium (Mg) and metal silver (Ag) were simultaneously evaporated as a cathode (10:90, 140 Å) 180b, and then a CPL material was evaporated as a capping layer (CPL, 650 Å) 180c. The device was transferred back to the glovebox and encapsulated with a glass lid 190 to complete the device.
In the following Top-emission Devices 1-2 to 1-9, the HTL was used as the microcavity adjustment layer. The thickness of the HTL was adjusted to about 1400 Å to obtain the maximum value of the external quantum efficiency EQE of the corresponding device.
The preparation method of Top-emission Device 1-2 was the same as that of Top-emission Device 1-1, except that in the emissive layer (EML), the ratio of Compound H1, Compound H2 and Compound GD-17 was 47:47:6.
The preparation method of Top-emission Device 1-3 was the same as that of Top-emission Device 1-1, except that Compound H1, Compound H2 and Compound GD-3 were simultaneously evaporated as the emissive layer and the ratio of Compound H1, Compound H2 and Compound GD-3 was 48:48:4.
The preparation method of Top-emission Device 1-4 was the same as that of Top-emission Device 1-3, except that in the emissive layer (EML), the ratio of Compound H1, Compound H2 and Compound GD-3 was 47:47:6.
The preparation method of Top-emission Device 1-5 was the same as that of Top-emission Device 1-1, except that in the emissive layer (EML), the ratio of Compound H1, Compound H2 and Compound GD-17 was 63:31:6.
The preparation method of Top-emission Device 1-6 was the same as that of Top-emission Device 1-3, except that in the emissive layer (EML), the ratio of Compound H1, Compound H2 and Compound GD-3 was 63:31:6.
The preparation method of Top-emission Device 1-7 was the same as that of Top-emission Device 1-1, except that Compound H1, Compound H2 and Compound GDA were simultaneously evaporated as the emissive layer and the ratio of Compound H1, Compound H2 and Compound GDA was 47:47:6.
The preparation method of Top-emission Device 1-8 was the same as that of Top-emission Device 1-7, except that in the emissive layer (EML), the ratio of Compound H1, Compound H2 and Compound GDA was 63:31:6.
The preparation method of Top-emission Device 1-9 was the same as that of Top-emission Device 1-7, except that in the emissive layer (EML), the ratio of Compound H1, Compound H2 and Compound GDA was 75:19:6.
Detailed structures and thicknesses of part of layers of the devices of Top-emission Devices 1-1 to 1-9 are shown in Table 6. A layer using more than one material is obtained by doping different compounds at their weight ratio as recorded.
Device performance of Top-emission Devices 1-1 to 1-9 is summarized in Table 7. The color coordinates CIEx and CIEy, the maximum emission peak wavelength λmax, the full width at half maximum FWHM and the maximum external quantum efficiency EQEA were measured at a current density of 10 mA/cm2. The efficiency conversion rate E is a ratio of the maximum external quantum efficiency EQE of the top-emission device and the corresponding bottom-emission device having the “same” device structure measured at a current density Jo=10 mA/cm2.
Top-emission Devices 1-1, 1-2 and 1-5 have the same device structures as the above Bottom-emission Devices 1-1, 1-2 and 1-5, respectively. The materials used in Bottom-emission Devices 1-1, 1-2 and 1-5 are all the same, except that the mass ratios of the host materials and the emissive doped material are different in the EMLs, which are H1 :H2:GD-17 (48:48:4), H1 :H2:GD-17 (47:47:6) and H1 :H2:GD-17 (63:31:6) in the EMLs, respectively.
Similarly, Top-emission Devices 1-3, 1-4 and 1-6 have the same device structures as the above Bottom-emission Devices 1-3, 1-4 and 1-6, respectively. The materials used in Bottom-emission Devices 1-3, 1-4 and 1-6 are all the same, except that the mass ratios of the host materials and the emissive doped material are different in the EMLs.
However, Top-emission Devices 1-7, 1-8 and 1-9 have the same device structures as the above Bottom-emission Devices 1-7, 1-8 and 1-9, respectively. In Bottom-emission Devices 1-7, 1-8 and 1-9, although the mass ratios of the host materials and the emissive doped material GDA in the EMLs are also adjusted to be different so that the exciton fraction distributions in the emissive layers of the bottom-emission devices are adjusted, as shown in
Efficiency conversion rates E measured at different current densities Jo for Top-emission Devices 1-1 to 1-9 are summarized in Table 8, and efficiency conversion rates E measured at 10 mA/cm2, 15 mA/cm2, 35 mA/cm2 and 50 mA/cm2 are recorded.
As shown in Table 8, in Top-emission Devices 1-1 to 1-9, when 500 nm≤λmax≤600 nm, as long as the corresponding bottom-emission device satisfies that the exciton recombination peak position is located in the emissive layer within a region greater than 0 and less than or equal to 65% of the thickness of the emissive layer from the side close to the anode, it can be satisfied that the efficiency conversion rate E is greater than or equal to 1.625 at different current densities.
Top-emission Device 1-10: a red phosphorescent top-emission organic electroluminescent device 300 is as shown in
Firstly, a glass substrate with a thickness of 0.7 mm was provided. On the glass substrate, indium tin oxide (ITO) 75 Å/Ag 1500 Å/ITO 150 Å was pre-patterned for use as a first anode 310. The substrate was dried in a glovebox to remove moisture, mounted on a holder and transferred into a vacuum chamber. Organic layers specified below were sequentially evaporated through vacuum thermal evaporation on the anode layer at a rate of 0.01 to 10 Å/s and a vacuum degree of about 10−6 Torr. Firstly, Compounds HT1 and PD were simultaneously evaporated as a hole injection layer (HIL, 97:3, 100 Å) 320, and Compound HT1 was evaporated as a hole transporting layer (HTL, ˜2000 Å) 330. The HTL was also used as a microcavity adjustment layer. The thickness of the HTL was adjusted to about 2000 Å to obtain a maximum value of external quantum efficiency EQE. Then, Compound EB was evaporated for use as an electron blocking layer (EBL, 50 Å) 340, on which Compound RH and Compound RD-5 were simultaneously evaporated as a first emissive layer (EML, 97:3, 400 Å) 350, and Compounds ET1 and Liq were co-deposited as an electron transporting layer (ETL, 140:210, 350 Å) 360. Then, a first multi-stack cathode layer 370 of the top-emission was evaporated. Specifically, metal ytterbium (Yb) with a thickness of 10 Å was evaporated as an electron injection layer (EIL) 370a, metal magnesium (Mg) and metal silver (Ag) were simultaneously evaporated as a cathode (14:126, 140 Å) 370b, and then a CPL material was evaporated as a capping layer (CPL, 650 Å) 370c. The device was transferred back to the glovebox and encapsulated with a glass lid 380 to complete the device.
Bottom-emission Device 1-10: a red phosphorescent bottom-emission organic electroluminescent device 400 having the same device structure as Top-emission Device 1-10 was prepared, as shown in
The preparation method of Bottom-emission Device 1-10 was the same as that of Top-emission Device 1-10, except that a glass substrate with a thickness of 0.7 mm was provided, on the glass substrate, indium tin oxide (ITO) with a thickness of 1200 Å was pre-patterned for use as a second anode 410, then, after the substrate was washed with deionized water and a detergent, a surface of ITO was treated with oxygen plasma and UV ozone, and the substrate was dried in a glovebox to remove moisture, mounted on a holder and transferred into a vacuum chamber; except that Compound HT1 was evaporated as a hole transporting layer (HTL, 400 Å) 430; except that a second multi-stack cathode layer 470 of the bottom-emission was evaporated, specifically, Compound Liq with a thickness of 10 Å was evaporated as an electron injection layer (EIL) 470a, and then metal aluminum (Al) was evaporated as a cathode (1200 Å) 470b.
Part of device structures of Top-emission Device 1-10 and Bottom-emission Device 1-10 are listed in Table 9. A layer using more than one material is obtained by doping different compounds at their weight ratio as recorded.
The new compounds used in the devices are shown as follows:
Device performance of Top-emission Device 1-10 and Bottom-emission Device 1-10 is summarized in Table 10 and Table 11. The color coordinates CIEx and CIEy, the maximum emission peak wavelength λmax, the full width at half maximum FWHM and the maximum external quantum efficiency EQE were measured at a current density of 10 mA/cm2. The maximum external quantum efficiency conversion rate E from the bottom-emission to the top-emission is, as previously described, a ratio of the maximum external efficiency EQE of Top-emission Device 1-10 and Bottom-emission Device 1-10 measured at a current density Jo=10 mA/cm2. The exciton recombination peak position is a position in the emissive layer corresponding to a maximum exciton fraction obtained when Bottom-emission Device 1-10 was tested.
The measured exciton fraction distribution of the above Bottom-emission Device 1-10 is shown in
To sum up, the present disclosure discloses a high-efficiency top-emission organic electroluminescent device. In the present application, the exciton recombination peak position and the efficiency conversion rate E are adjusted so that a top-emission device having excellent device performance is obtained. Compared to other organic electroluminescent devices, the top-emission organic electroluminescent device has more excellent performance and can exhibit more excellent device performance with the same organic emissive doped material.
It is to be understood that various embodiments described herein are merely examples and not intended to limit the scope of the present disclosure. Therefore, it is apparent to the persons skilled in the art that the present disclosure as claimed may include variations of specific embodiments and preferred embodiments described herein. Many of materials and structures described herein may be substituted with other materials and structures without departing from the spirit of the present disclosure. It is to be understood that various theories as to why the present disclosure works are not intended to be limitative.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202210734050.7 | Jun 2022 | CN | national |
