A fluorescent organic electroluminescent device sensitized by thermally activated delayed fluorescent material

Abstract

The present invention discloses a fluorescent organic electroluminescent device based on thermally activated delayed fluorescent material. The light-emitting layer includes a main material, a thermally activated delayed fluorescent material and a fluorescent material, wherein the triplet energy level of the main material is higher than the singlet energy level of the thermally activated delayed fluorescent material, and the energy gap difference between the two is 0 to 2.0 eV (excluding 0); the thermally activated delayed fluorescent material is a thioxanthone derivative, and the difference between its singlet energy level and triplet energy level is less than 0.3 eV; the triplet energy level of the thermally activated delayed fluorescent material is higher than the singlet energy level of the fluorescent material, and the energy gap difference between the two is 0 to 1.5 eV (excluding 0). The efficiency of the fluorescent organic electroluminescent device is significantly improved, and the fluorescent organic electroluminescent device has a low turn-on voltage and excellent stability.

Description

Technical Field

[0001] The invention belongs to the field of organic electroluminescent devices, and in particular relates to a fluorescent organic electroluminescent device based on thermally activated sensitized thermally activated delayed fluorescent material. Background Art

[0002] Organic light-emitting diodes (OLEDs) have the advantages of being light, thin, flexible, low energy consumption, wide viewing angle and fast response. They have broad application prospects in the fields of display and lighting, and have therefore attracted more and more attention.

[0003] Organic light-emitting materials are an indispensable and important component of OLEDs and significantly affect the efficiency of devices. In 1987, Deng Qingyun and others from Kodak first reported a double-layer OLED device made of fluorescent material Alq3 as the light-emitting material. Although traditional fluorescent materials have the advantages of low cost and stable chemical properties, due to their forbidden electron spin flips, according to spin statistics, under electrical excitation, fluorescent materials can only utilize 25% of singlet excitons, resulting in OLED devices with fluorescent materials as light-emitting materials cannot achieve the ideal external quantum efficiencies (EQE).

[0004] In order to improve the utilization rate of excitons, heavy atoms are introduced to increase the intersystem crossing from singlet to triplet, thereby achieving 100% internal quantum efficiency. However, since phosphorescent materials contain heavy metal atoms, the material cost is increased. At the same time, the efficiency roll-off is large and there is a lack of stable blue light materials, which limits its further development. In order to overcome the above problems, pure organic thermally activated delayed fluorescence (TADF) materials have a small singlet-triplet energy level difference and can achieve 100% internal quantum efficiency, which is expected to become the third generation of organic light-emitting materials. However, this material currently still has the problem of low efficiency of fluorescent electroluminescent devices. Summary of the invention

[0005] In order to improve the efficiency of electroluminescent devices made of fluorescent materials, the present invention provides a thermally activated sensitized fluorescent organic electroluminescent device based on a thioxanthone thermally activated delayed fluorescent material. By using the thioxanthone thermally activated delayed fluorescent material as a co-dopant, the singlet and triplet excitons in the device can be fully utilized, thereby improving the device efficiency of the organic electroluminescent device.

[0006] An organic electroluminescent device, characterized in that the device comprises a light-emitting layer, wherein the light-emitting layer comprises a main material and a doping material, wherein the doping material comprises a thermally activated delayed fluorescent material and a fluorescent material.

[0007] The number of the light-emitting layer is one or more than one.

[0008] According to the present invention, the triplet energy level of the host material is higher than the singlet energy level of the thermally activated delayed fluorescent material, and the energy gap difference between the two is 0 to 2.0 eV (excluding 0). The host material can be one or a mixture of two or more.

[0009] The thermally activated delayed fluorescence material refers to a material that can emit thermally activated delayed fluorescence (TADF). TADF means that when the energy of the triplet excited state (T1) is close to that of the singlet excited state (S1), the triplet excited state can be transferred to the singlet excited state through a thermally activated reverse intersystem crossing (RISC) process to emit fluorescence.

[0010] According to the present invention, the energy level difference between the singlet state and the triplet state of the thermally activated delayed fluorescent material is less than 0.3 eV.

[0011] According to the present invention, the triplet energy level of the thermally activated delayed fluorescent material is higher than the singlet energy level of the fluorescent material, and the energy gap difference between the two is 0 to 1.5 eV (excluding zero).

[0012] According to the present invention, the fluorescent material accounts for 0.1-20% of the main material by mass, preferably 0.5-10%; the thermally activated delayed fluorescent material accounts for 5-80% of the main material by mass, preferably 10-40%.

[0013] According to the present invention, the thermally activated delayed fluorescent material is a thioxanthone derivative, and the thioxanthone derivative is selected from the following compounds of general formula (I), (II), and (III):

[0014]

[0015] Wherein, X1, X2, X3, X4, and X5 are independently selected from sulfur atoms, sulfone groups (-SO2-), and sulfoxide groups (-SO-); m, n, p, q, r, and s are independently selected from integers of 0 to 4; R1, R2, R3, R4, R5, and R6 are independently selected from H, C 1-30 Alkyl, C 2-30 Alkenyl, C 2-30 Alkynyl, cycloalkyl, aryl, heteroaryl, heterocyclic, halogen, amino, sulfonic acid, carboxylic acid, C 1-30 Alkoxy, aryloxy, -CO-C 1-30 Alkyl, -CO-aryl, -COO-C 1-30Alkyl, -COO-aryl, wherein the C 1-30 Alkyl, C 2-30 Alkenyl, C 2-30 Alkynyl, cycloalkyl, aryl, heteroaryl, heterocyclic group may be substituted by one or more substituents R a Substitution; the substituent R a Independent: C 1-30 Alkyl, C 2-30 Alkenyl, C 2-30 Alkynyl, aryl, halogen, amino, sulfonic acid, carboxylic acid, -CO-C 1-30 Alkyl, -CO-aryl, -COO-C 1-30 Alkyl, -COO-aryl.

[0016] According to the present invention, the thermally activated delayed fluorescent material is selected from the group consisting of, but not limited to, the following specific compounds:

[0017]

[0018] According to the present invention, the fluorescent material includes but is not limited to one or more of the following structures:

[0019]

[0020]

[0021]

[0022] According to the present invention, the host material can be any host material known in the prior art, for example, a carbazole-based material, such as mCBP (3,3′-di(9H-carbazole-9-yl)-1,1′-biphenyl), CBP (4,4′-di(9-carbazole)biphenyl), or mCP (1,3-bis(9-carbazole)benzene).

[0023] According to the present invention, the structure of the organic electroluminescent device can be various structures known in the prior art. Preferably, it includes: an anode layer, a hole injection layer, a hole transport layer, optionally an exciton blocking layer, a light-emitting layer, an electron transport layer, an electron injection layer, and a cathode layer. The organic electroluminescent device further includes a substrate (such as a glass substrate). The anode can be indium tin oxide. The hole injection layer can be a-NPD (N,N'-bis(naphthalene-1-yl)-N,N'-bis(phenyl)-2,2'-dimethylbenzidine). The hole transport layer may be TCTA (4,4',4"-tri(carbazole-9-yl)triphenylamine) or TAPC (4,4'-cyclohexylbis[N,N-bis(4-methylphenyl)aniline]). The optional exciton blocking layer is mCP (1,3-bis(9-carbazole)benzene). The electron transport layer may be B4PyMPM (4,6-bis(3,5-di(4-pyridyl)phenyl)-2-methylpyrimidine) or TmPyPB (1,3,5-tri[(3-pyridyl)-phenyl-3-yl]benzene). The electron injection layer is LiF and the cathode is Al.

[0024] According to the present invention, the structure of the organic electroluminescent device is:

[0025] ITO / a-NPD (35nm) / TCTA (10nm) / mCP (5nm) / mCBP: 15wt%TXO-TPA: 1wt%DBP (35nm) / B4PyMPM (45nm) / LiF (1.1nm) / Al (100nm), or

[0026] ITO / a-NPD (35nm) / TCTA (10nm) / mCP (5nm) / mCBP: 25wt%TXO-TPA: 1wt%DBP (17.5nm) / mCBP: 15wt%TXO-TPA: 2wt%DBP (17.5nm) / B4PyMPM (45nm) / LiF (1.1nm) / Al (100nm), or

[0027] ITO / TAPC (30nm) / CBP: 10wt% 2,7-TXO-PhCz: 0.5wt% DCJTB (20nm) / TmPyPB (50nm) / LiF (1.1nm) / Al (100nm), or

[0028] ITO / TAPC (30nm) / mCBP: 10wt% 2,7-TXO-PhCz: 0.5wt% DCJTB (20nm) / TmPyPB (50nm) / LiF (1.1nm) / Al (100nm), or

[0029] ITO / TAPC (30nm) / mCP: 5wt% 2,7-TXO-PhCz: 0.5wt% DCJTB (20nm) / TmPyPB (50nm) / LiF (1.1nm) / Al (100nm), or

[0030] ITO / TAPC(30nm) / CBP:10wt%2,7-TXO-PhCz:1wt%DCJTB(20nm) / TmPyPB(50nm) / LiF(1.1nm) / Al(100nm);

[0031] Among them, ITO is an indium tin oxide conductive film, a-NPD is N,N'-bis(naphthalene-1-yl)-N,N'-bis(phenyl)-2,2'-dimethylbenzidine, TCTA is 4,4',4"-tri(carbazole-9-yl)triphenylamine, TAPC is 4,4'-cyclohexylbis[N,N-di(4-methylphenyl)aniline], mCP is 1,3-bis(9-carbazole)benzene, mCBP is 3,3'-di(9H-carbazole-9-yl)-1,1'-biphenyl, CBP is 4,4'-di(9-carbazole)biphenyl, B4PyMPM is 4,6-bis(3,5-di(4-pyridyl)phenyl)-2-methylpyrimidine, and TmPyPB is 1,3,5-tri[(3-pyridyl)-phenyl-3-yl]benzene.

[0032] The present invention also provides a method for preparing the organic electroluminescent device, comprising: 1) preparing a hole injection layer in the organic electroluminescent device on an anode by vacuum thermal evaporation; 2) preparing a hole injection layer and a hole transport layer in the organic electroluminescent device by vacuum thermal evaporation; 3) optionally preparing an exciton blocking layer in the organic electroluminescent device by vacuum thermal evaporation; 4) preparing a light-emitting layer doped with the thermally activated delayed fluorescent material and the fluorescent material of the present invention by vacuum thermal evaporation, and optionally evaporating one or more light-emitting layers; 5) sequentially preparing an electron transport layer, an electron injection layer, and a cathode layer by vacuum thermal evaporation.

[0033] According to the present invention, in the method, the anode may be indium tin oxide. The hole injection layer may be a-NPD (N,N'-bis(naphthalene-1-yl)-N,N'-bis(phenyl)-2,2'-dimethylbenzidine). The hole transport layer may be TCTA (4,4',4"-tri(carbazole-9-yl)triphenylamine), TAPC (4,4'-cyclohexylbis[N,N-di(4-methylphenyl)aniline]). The optional exciton blocking layer is mCP (1,3-bis(9-carbazolyl)benzene). The light-emitting layer includes a single host material and a co-doped thermally activated delayed fluorescent material and a fluorescent material according to the present invention, wherein the single host material may be mCBP (3,3 The electron transport layer may be B4PyMPM (4,6-bis(3,5-di(4-pyridyl)phenyl)-2-methylpyrimidine) or TmPyPB (1,3,5-tris[(3-pyridyl)-phenyl-3-yl]benzene). The electron injection layer is LiF, and the cathode is Al.

[0034] The present invention further provides the use of the thermally activated sensitized fluorescent organic electroluminescent device based on the thermally activated delayed fluorescent material, which can be used in the fields of display devices and daily lighting.

[0035] The present invention also provides a display device, comprising the organic electroluminescent device of the present invention.

[0036] The beneficial effects of the present invention are as follows:

[0037] 1) The present invention provides a fluorescent organic electroluminescent device based on thermally activated delayed fluorescent material and thermally activated delayed fluorescent material as a sensitizer and a fluorescent material as a luminescent object. The thermally activated delayed fluorescent material can simultaneously capture and utilize singlet and triplet excitons, and the external quantum efficiency of the fluorescent organic electroluminescent device exceeds 5% through Foerster energy transfer from thermally activated delayed fluorescence to the fluorescent material, which significantly improves the efficiency of the fluorescent organic electroluminescent device and has a low turn-on voltage.

[0038] 2) The thermally activated sensitized fluorescent organic electroluminescent device based on the thermally activated delayed fluorescent material of the present invention can effectively regulate and utilize the triplet exciton energy, thereby significantly improving the efficiency of the fluorescent organic electroluminescent device. At the same time, due to the excellent chemical stability of the fluorescent material, an organic electroluminescent device with low turn-on voltage, small efficiency roll-off and good device stability can be obtained.

[0039] Definitions and explanations of terms

[0040] Unless otherwise defined, all technical terms herein have the same meaning as commonly understood by those skilled in the art to which the subject matter of the claims belongs. If there are multiple definitions for a term herein, the definition in this chapter shall prevail.

[0041] It should be understood that the above brief description and the following detailed description are exemplary and are only used for explanation, and do not limit the subject matter of the present application. In this application, unless otherwise specified, the terms "or" and "or" used mean "and / or". In addition, the terms "including" and other forms, such as "comprising", "including" and "containing" used are not restrictive.

[0042] The term "optional" or "optionally" means that the subsequently described event or circumstance may or may not occur, and that the description includes both the occurrence of said event or circumstance and the non-occurrence of said event or circumstance.

[0043] The term "halogen" refers to F, Cl, Br and I.

[0044] The term "C 1-30 "Alkyl" is understood to mean a straight or branched saturated monovalent hydrocarbon group having 1 to 30 carbon atoms, preferably C 1-10 Alkyl. "C 1-10 “Alkyl” is understood to mean a straight-chain or branched, saturated, monovalent hydrocarbon radical having 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 carbon atoms. The alkyl radical is, for example, methyl, ethyl, propyl, butyl, pentyl, hexyl, isopropyl, isobutyl, sec-butyl, tert-butyl, isopentyl, 2-methylbutyl, 1-methylbutyl, 1-ethylpropyl, 1,2-dimethylpropyl, neopentyl, 1,1-dimethylpropyl, 4-methylpentyl, 3-methylpentyl, 2-methylpentyl, 1-methylpentyl, 2-ethylbutyl, 1-ethylbutyl, 3,3-dimethylbutyl, 2,2-dimethylbutyl, 1,1-dimethylbutyl, 2,3-dimethylbutyl, 1,3-dimethylbutyl or 1,2-dimethylbutyl, etc. or their isomers. In particular, the radical has 1, 2, 3, 4, 5, 6 carbon atoms (“C 1-6 alkyl”), for example methyl, ethyl, propyl, butyl, isopropyl, isobutyl, sec-butyl, tert-butyl.

[0045] The term "C 2-30 "Alkenyl" is understood to mean a linear or branched monovalent hydrocarbon radical containing one or more double bonds and having 2 to 30 carbon atoms, preferably "C 2-10 "C 2-10 "Alkenyl" is understood to mean a linear or branched monovalent hydrocarbon radical containing one or more double bonds and having 2, 3, 4, 5, 6, 7, 8, 9 or 10 carbon atoms, in particular 2 or 3 carbon atoms ("C 2-3It should be understood that when the alkenyl group contains more than one double bond, the double bonds may be separated from each other or conjugated. The alkenyl group is, for example, vinyl, allyl, (E)-2-methylvinyl, (Z)-2-methylvinyl, (E)-but-2-enyl, (Z)-but-2-enyl, etc.

[0046] The term "C 2-30 "Alkynyl" is understood to mean a linear or branched monovalent hydrocarbon radical containing one or more triple bonds and having 2 to 30 carbon atoms, preferably "C2-C 10 The term "C2-C 10 “Alkynyl” is understood as meaning a straight-chain or branched, monovalent hydrocarbon radical which contains one or more triple bonds and has 2, 3, 4, 5, 6, 7, 8, 9 or 10 carbon atoms, in particular 2 or 3 carbon atoms (“C2-C3-alkynyl”). Such alkynyl groups are, for example, ethynyl, prop-1-ynyl, prop-2-ynyl, but-1-ynyl, but-2-ynyl, but-3-ynyl, pent-1-ynyl, pent-2-ynyl, pent-3-ynyl.

[0047] The term "cycloalkyl" is understood to mean a saturated monovalent monocyclic or bicyclic hydrocarbon ring having 3 to 20 carbon atoms, preferably "C 3-10 The term "Cycloalkyl" 3-10 "Cycloalkyl" is understood to mean a saturated, monovalent, monocyclic or bicyclic hydrocarbon ring having 3, 4, 5, 6, 7, 8, 9 or 10 carbon atoms. 3-10 The cycloalkyl group may be a monocyclic hydrocarbon group such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl or cyclodecyl, or a bicyclic hydrocarbon group such as a decalin ring.

[0048] The term "aryl" is understood to mean preferably a monovalent aromatic or partially aromatic monocyclic, bicyclic or tricyclic hydrocarbon ring having 6 to 20 carbon atoms, preferably "C 6-14 The term "C 6-14 The term "aryl" is understood to mean preferably a monovalent aromatic or partially aromatic monocyclic, bicyclic or tricyclic hydrocarbon ring ("C 6-14 or a ring having 9 carbon atoms ("C9 aryl"), for example indanyl or indenyl, or a ring having 10 carbon atoms ("C 10 aryl), such as tetrahydronaphthyl, dihydronaphthyl or naphthyl, or a ring having 13 carbon atoms ("C 13 aryl), such as fluorenyl, or a ring having 14 carbon atoms ("C 14 "aryl"), for example anthracenyl.

[0049] The term "heteroaryl" is understood as a monovalent monocyclic, bicyclic or tricyclic aromatic ring system having 5 to 20 ring atoms and containing 1 to 5 heteroatoms independently selected from N, O and S, for example "5-14 membered heteroaryl". The term "5-14 membered heteroaryl" is understood as a monovalent monocyclic, bicyclic or tricyclic aromatic ring system having 5, 6, 7, 8, 9, 10, 11, 12, 13 or 14 ring atoms, in particular 5 or 6 or 9 or 10 carbon atoms, and containing 1 to 5, preferably 1 to 3 heteroatoms independently selected from N, O and S, and, in each case, may additionally be benzo-fused. In particular, the heteroaryl group is selected from thienyl, furanyl, pyrrolyl, oxazolyl, thiazolyl, imidazolyl, pyrazolyl, isoxazolyl, isothiazolyl, oxadiazolyl, triazolyl, thiadiazolyl, thia-4H-pyrazolyl and the like and benzo derivatives thereof, such as benzofuranyl, benzothienyl, benzoxazolyl, benzisoxazolyl, benzimidazolyl, benzotriazolyl, indazolyl, indolyl, isoindolyl and the like; or pyridyl, pyridazinyl, pyrimidinyl, pyrazinyl, triazinyl and the like and benzo derivatives thereof, such as quinolyl, quinazolinyl, isoquinolyl and the like; or azinyl, indolizinyl, purinyl and the like and benzo derivatives thereof; or cinnolinyl, phthalazinyl, quinazolinyl, quinoxalinyl, naphthyridinyl, pteridinyl, carbazolyl, acridinyl, phenazinyl, phenothiazinyl, phenoxazinyl and the like.

[0050] The term "heterocyclyl" is understood to mean a saturated, unsaturated or partially saturated monocyclic, bicyclic or tricyclic ring containing from 3 to 20 ring atoms, wherein 1, 2, 3, 4 or 5 ring atoms are selected from nitrogen, sulfur or oxygen, and unless otherwise indicated, they may be connected via carbon or nitrogen, wherein -CH2- groups are optionally replaced by -C(O)-; it should be understood that when the total number of S atoms and O atoms in the heterocyclyl exceeds 1, these heteroatoms are not adjacent to each other. If the heterocyclyl is bicyclic or tricyclic, at least one ring may optionally be a heteroaromatic ring or an aromatic ring, provided that at least one ring is non-heteroaromatic. If the heterocyclyl is a monocyclic ring, it must not be aromatic. Examples of heterocyclic groups include, but are not limited to, piperidinyl, piperazinyl, azetidinyl, oxetanyl, morpholinyl, tetrahydroisoquinolyl, tetrahydroquinolyl, indolinyl, tetrahydropyranyl, dihydro-2H-pyranyl, tetrahydrofuranyl, tetrahydrothiopyranyl, tetrahydrothiopyran-1-oxide, dioxolyl, pyrrolidinyl, imidazolidinyl, pyrazolidinyl, pyrrolinyl, dithianyl, thiomorpholinyl, trithianyl. Optionally, the heterocyclic group can be benzo-fused. The heterocyclic group can be bicyclic, such as, but not limited to, 5,5-membered rings, such as hexahydrocyclopenta [c] pyrrole -2 (1H) -yl ring, or 5,6-membered bicyclic rings, such as hexahydropyrrolo [1,2-a] pyrazine -2 (1H) -yl ring. The ring containing the nitrogen atom may be partially unsaturated, i.e. it may contain one or more double bonds, such as but not limited to 2,5-dihydro-1H-pyrrolyl, 4H-[1,3,4]thiadiazinyl, 4,5-dihydrooxazolyl or 4H-[1,4]thiazinyl, or it may be benzo-fused, such as but not limited to dihydroisoquinolyl, 1,3-benzoxazolyl, 1,3-benzodioxolyl.

[0051] The term "amino" refers to -N(R 1 ) 2, said R 1 The same or different, independently selected from H, C 1-10 Alkyl, aryl, heteroaryl. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0053] Figure 1 This is the electroluminescence spectrum of the electroluminescent device based on TXO-TPA and DBP-doped mCBP as the single light-emitting layer of the device according to Example 1 of the present invention.

[0054] Figure 2 The graphs are the current density and brightness curves at different voltages of the electroluminescent device based on TXO-TPA and DBP-doped mCBP as a single light-emitting layer of the device according to Example 1 of the present invention.

[0055] Figure 3This is the electroluminescence spectrum of the electroluminescent device based on TXO-TPA and DBP-doped mCBP as the double light-emitting layer of the device according to Example 2 of the present invention.

[0056] Figure 4 The graphs are the current density and brightness curves at different voltages of the electroluminescent device based on TXO-TPA and DBP-doped mCBP as the double light-emitting layer of the device according to Example 2 of the present invention.

[0057] Figure 5 1 is the electroluminescence spectrum of the electroluminescent device based on 2,7-TXO-PhCz and DCJTB-doped CBP as the light-emitting layer of the device according to Example 3 of the present invention.

[0058] Figure 6 1 is the electroluminescence spectrum of the electroluminescent device based on 2,7-TXO-PhCz and DCJTB-doped mCBP as the light-emitting layer of the device according to Example 4 of the present invention.

[0059] Figure 7 It is the electroluminescence spectrum of the electroluminescent device based on 2,7-TXO-PhCz and DCJTB-doped mCP as the light-emitting layer of the device according to Example 5 of the present invention. DETAILED DESCRIPTION

[0060] In order to explain the present invention more clearly, the present invention is further described below in conjunction with specific embodiments and drawings. It should be understood by those skilled in the art that these descriptions are only exemplary and are not intended to limit the scope of the present invention.

[0061] TCTA: 4,4',4"-tri(carbazol-9-yl)triphenylamine; a-NPD: N,N'-bis(naphthalene-1-yl)-N,N'-bis(phenyl)-2,2'-dimethylbenzidine; mCP: 1,3-bis(9-carbazol-9-yl)benzene; mCBP: 3,3'-bis(9H-carbazol-9-yl)-1,1'-biphenyl; B4PyMPM: 4,6-bis(3,5-di(4-pyridyl)phenyl)-2-methylpyrimidine; TAPC: 4,4'-cyclohexylbis[N,N-di(4-methylphenyl)aniline]; CBP: 4,4'-bis(9-carbazol-9-yl)biphenyl; TmPyPB: 1,3,5-tri[(3-pyridyl)-phenyl-3-yl]benzene;

[0062] TXO-TPA: 2,7-TXO-PhCz:

[0063] DBP: DCJTB:

[0064] Example 1

[0065] The glass substrate with indium tin oxide (ITO) transparent conductive electrode was ultrasonically cleaned in commercial cleaning agent, deionized water, acetone, and ethanol for 10 minutes. The cleaned glass substrate was placed in a drying oven at 75 degrees Celsius for 10 minutes for use. Then, the dried glass substrate was subjected to ozone plasma surface treatment for 10 minutes. The treated substrate was quickly transferred to a vacuum chamber and the chamber pressure was lower than 5.0×10 -4 After Pa, the functional layer materials are sequentially deposited according to the device structure. First, 35nm of a-NPD is evaporated as the hole injection layer; then 10nm of TCTA is evaporated as the hole transport layer; mCP is evaporated on the hole transport layer as the exciton blocking layer with a thickness of 5nm; TXO-TPA and DBP-doped mCBP are evaporated on the exciton blocking layer as the light-emitting layer of the device, the doping ratio of TXO-TPA is 15% of the mass percentage of mCBP, the doping ratio of DBP is 1% of the mass percentage of mCBP, and the thickness of the light-emitting layer is 35nm; continue to evaporate a layer of B4PyMPM as the electron transport layer with a thickness of 45nm; finally, LiF layer and Al are evaporated on the above electron transport layer in sequence as the electron injection layer and cathode layer of the device, respectively, where the thickness of the LiF layer is 1.1nm and the thickness of the Al layer is 100nm.

[0066] The device structure of this embodiment is as follows:

[0067] ITO / a-NPD(35nm) / TCTA(10nm) / mCP(5nm) / mCBP:15wt%TXO-TPA:1wt%DBP(35nm) / B4PyMPM(45nm) / LiF(1.1nm) / Al(100nm). Among them, the evaporation rate of the electron injection layer LiF is 0.1 angstroms / second, the evaporation rate of the cathode Al is 3 angstroms / second, and the evaporation rate of other organic layers is 2 angstroms / second. After the evaporation of all functional layers is completed, the cavity is cooled for 10 minutes and then filled with nitrogen to take out the device. Then the device is photoelectrically tested using a PR655 spectrometer and CS-200 brightness meter produced by PhotoResearch and a Keithley2400 source meter produced by Geely.

[0068] The device performance indicators are as follows:

[0069] Start voltage: 2.8V;

[0070] Maximum brightness: 10098cd / m 2 ;

[0071] Maximum luminous efficiency: 20.6cd / A;

[0072] Maximum external quantum efficiency: 15.3%.

[0073] Figure 1 It is the electroluminescence spectrum of an electroluminescent device based on TXO-TPA and DBP-doped mCBP as the light-emitting layer of the device at a certain voltage, and the emission position is in the red light region; Figure 2 The curves of current density and brightness of electroluminescent devices based on TXO-TPA and DBP-doped mCBP as the light-emitting layer of the device at different voltages show that the device has a brightness of 1 cd / m 2 It can be turned on at any time, the turn-on voltage is 2.8V, and the maximum brightness is 10098cd / m 2 The maximum external quantum efficiency can reach 15.3%, exceeding the theoretical limit of ordinary fluorescent devices.

[0074] Example 2

[0075] The ITO glass substrate processing method, vacuum chamber pressure, evaporation rate and testing instrument are the same as those in Example 1. First, 35nm of a-NPD is evaporated as a hole injection layer; then 10nm of TCTA is evaporated as a hole transport layer; mCP is evaporated on the hole transport layer as an exciton blocking layer with a thickness of 5nm; TXO-TPA and DBP-doped mCBP are evaporated on the exciton blocking layer as the first light-emitting layer of the device, the doping ratio of TXO-TPA is 25% of the mass percentage of mCBP, the doping ratio of DBP is 1% of the mass percentage of mCBP, and the thickness of the light-emitting layer is 17.5nm; TXO is evaporated on the first light-emitting layer. -TPA and DBP doped mCBP is used as the second light-emitting layer of the device, the doping ratio of TXO-TPA is 15% by mass, the doping ratio of DBP is 2% by mass, and the thickness of the light-emitting layer is 17.5nm; continue to evaporate a layer of B4PyMPM as an electron transport layer with a thickness of 45nm; finally, LiF layer and Al are evaporated in sequence on the above-mentioned electron transport layer as the electron injection layer and cathode layer of the device respectively, wherein the thickness of the LiF layer is 1.1nm, and the thickness of the Al layer is 100nm.

[0076] The device structure of this embodiment is as follows:

[0077] ITO / a-NPD(35nm) / TCTA(10nm) / mCP(5nm) / mCBP:25wt%TXO-TPA:1wt%DBP(17.5nm) / mCBP:15wt%TXO-TPA:2wt%DBP(17.5nm) / B4PyMPM(45nm) / LiF(1.1nm) / Al(100nm).

[0078] The device performance indicators are as follows:

[0079] Start voltage: 2.5V;

[0080] Maximum brightness: 9478cd / m 2 ;

[0081] Maximum luminous efficiency: 22.1cd / A;

[0082] Maximum external quantum efficiency: 16.9%.

[0083] Figure 3 It is the electroluminescence spectrum of an electroluminescent device based on TXO-TPA and DBP-doped mCBP as the light-emitting layer of the device at a certain voltage, and the emission position is in the red light region; Figure 4 The curves of current density and brightness of electroluminescent devices based on TXO-TPA and DBP-doped mCBP as the light-emitting layer of the device at different voltages show that the device has a brightness of 1 cd / m 2 It can be turned on at any time, the turn-on voltage is 2.5V, and the maximum brightness is 9478cd / m 2 The maximum external quantum efficiency can reach 16.9%, exceeding the theoretical limit of ordinary fluorescent devices.

[0084] Example 3

[0085] The ITO glass substrate processing method, vacuum chamber pressure, evaporation rate and testing instrument are the same as those in Example 1. First, 30nm of TAPC is evaporated as a hole transport layer; 2,7-TXO-PhCz and DCJTB-doped CBP are evaporated on the hole transport layer as the light-emitting layer of the device, the doping ratio of 2,7-TXO-PhCz is 10% of the mass percentage of CBP, the doping ratio of DCJTB is 0.5% of the mass percentage of CBP, and the thickness of the light-emitting layer is 20nm; continue to evaporate a layer of TmPyPB as an electron transport layer with a thickness of 50nm; finally, LiF layer and Al are evaporated on the above-mentioned electron transport layer in sequence as the electron injection layer and cathode layer of the device, respectively, wherein the thickness of the LiF layer is 1.1nm, and the thickness of the Al layer is 100nm.

[0086] The device structure of this embodiment is as follows:

[0087] ITO / TAPC (30nm) / CBP: 10wt% 2,7-TXO-PhCz: 0.5wt%DCJTB (20nm) / TmPyPB (50nm) / LiF (1.1nm) / Al (100nm).

[0088] The device performance indicators are as follows:

[0089] Start voltage: 3.2V;

[0090] Maximum luminous efficiency: 33.4cd / A;

[0091] Maximum external quantum efficiency: 11.9%.

[0092] Figure 5 The electroluminescent spectrum of an electroluminescent device based on 2,7-TXO-PhCz and DCJTB-doped CBP as the light-emitting layer of the device at a certain voltage, the emission position is in the orange-red light region; the electroluminescent device based on 2,7-TXO-PhCz and DCJTB-doped CBP as the light-emitting layer of the device has an electroluminescent spectrum of 1 cd / m 2 It can be turned on at any time, with a turn-on voltage of 3.2V and a maximum external quantum efficiency of 11.9%, exceeding the theoretical limit of ordinary fluorescent devices.

[0093] Example 4

[0094] The ITO glass substrate processing method, vacuum chamber pressure, evaporation rate and testing instrument are the same as those in Example 1. First, 30nm of TAPC is evaporated as a hole transport layer; 2,7-TXO-PhCz and DCJTB doped mCBP are evaporated on the hole transport layer as the light-emitting layer of the device, the doping ratio of 2,7-TXO-PhCz is 10% of the mass percentage of mCBP, the doping ratio of DCJTB is 0.5% of the mass percentage of mCBP, and the thickness of the light-emitting layer is 20nm; continue to evaporate a layer of TmPyPB as an electron transport layer with a thickness of 50nm; finally, LiF layer and Al are evaporated on the above-mentioned electron transport layer in sequence as the electron injection layer and cathode layer of the device, respectively, wherein the thickness of the LiF layer is 1.1nm, and the thickness of the Al layer is 100nm.

[0095] The device structure of this embodiment is as follows:

[0096] ITO / TAPC(30nm) / mCBP:10wt%2,7-TXO-PhCz:0.5wt%DCJTB(20nm) / TmPyPB(50nm) / LiF(1.1nm) / Al(100nm).

[0097] The device performance indicators are as follows:

[0098] Start voltage: 3.8V;

[0099] Maximum luminous efficiency: 28.4cd / A;

[0100] Maximum external quantum efficiency: 10.3%.

[0101] Figure 6The electroluminescent spectrum of an electroluminescent device based on 2,7-TXO-PhCz and DCJTB doped mCBP as the light-emitting layer of the device at a certain voltage, the emission position is in the orange-red light region; the electroluminescent device based on 2,7-TXO-PhCz and DCJTB doped mCBP as the light-emitting layer of the device has a brightness of 1cd / m 2 It can be turned on at any time, with a turn-on voltage of 3.8V and a maximum external quantum efficiency of 10.3%, exceeding the theoretical limit of ordinary fluorescent devices.

[0102] Example 5

[0103] The ITO glass substrate processing method, vacuum chamber pressure, evaporation rate and testing instrument are the same as those in Example 1. First, 40nm of TAPC is evaporated as a hole transport layer; 2,7-TXO-PhCz and DCJTB doped mCP are evaporated on the hole transport layer as the light-emitting layer of the device, the doping ratio of 2,7-TXO-PhCz is 5% of the mass percentage of mCP, the doping ratio of DCJTB is 0.5% of the mass percentage of mCP, and the thickness of the light-emitting layer is 20nm; continue to evaporate a layer of TmPyPB as an electron transport layer with a thickness of 50nm; finally, LiF layer and Al are evaporated on the above-mentioned electron transport layer in sequence as the electron injection layer and cathode layer of the device, respectively, wherein the thickness of the LiF layer is 1.1nm, and the thickness of the Al layer is 100nm.

[0104] The device structure of this embodiment is as follows:

[0105] ITO / TAPC(30nm) / mCP:5wt%2,7-TXO-PhCz:0.5wt%DCJTB(20nm) / TmPyPB(50nm) / LiF(1.1nm) / Al(100nm).

[0106] The device performance indicators are as follows:

[0107] Start voltage: 3.8V;

[0108] Maximum luminous efficiency: 26.1cd / A;

[0109] Maximum external quantum efficiency: 10.1%.

[0110] Figure 7 The electroluminescence spectrum of an electroluminescent device based on 2,7-TXO-PhCz and DCJTB-doped mCP as the luminescent layer of the device at a certain voltage is given, and the emission position is in the orange-red light region; the electroluminescent device based on 2,7-TXO-PhCz and DCJTB-doped mCP as the luminescent layer of the device has a brightness of 1 cd / m 2It can be turned on at any time, with a turn-on voltage of 3.8V and a maximum external quantum efficiency of 10.1%, exceeding the theoretical limit of ordinary fluorescent devices.

[0111] Example 6

[0112] The ITO glass substrate processing method, vacuum chamber pressure, evaporation rate and testing instrument are the same as those in Example 1. First, 30nm of TAPC is evaporated as a hole transport layer; 2,7-TXO-PhCz and DCJTB doped CBP are evaporated on the hole transport layer as the light-emitting layer of the device, the doping ratio of 2,7-TXO-PhCz is 10% of the mass percentage of CBP, the doping ratio of DBP is 1% of the mass percentage of CBP, and the thickness of the light-emitting layer is 20nm; continue to evaporate a layer of TmPyPB as an electron transport layer with a thickness of 50nm; finally, LiF layer and Al are evaporated on the above-mentioned electron transport layer in sequence as the electron injection layer and cathode layer of the device, respectively, wherein the thickness of the LiF layer is 1.1nm, and the thickness of the Al layer is 100nm.

[0113] The device structure of this embodiment is as follows:

[0114] ITO / TAPC (30nm) / CBP: 10wt% 2,7-TXO-PhCz: 1wt%DBP (20nm) / TmPyPB (50nm) / LiF (1.1nm) / Al (100nm).

[0115] The device performance indicators are as follows:

[0116] Start voltage: 3.3V;

[0117] Maximum luminous efficiency: 17.6cd / A;

[0118] Maximum external quantum efficiency: 10.6%.

[0119] The emission position of the electroluminescent device based on 2,7-TXO-PhCz and DCJTB-doped mCBP as the light-emitting layer of the device is in the red region, and its brightness is 1 cd / m 2 It can be turned on at any time, with a turn-on voltage of 3.3V and a maximum external quantum efficiency of 10.6%, exceeding the theoretical limit of ordinary fluorescent devices.

[0120] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An organic electroluminescent device, characterized in that: The device comprises a light-emitting layer, the light-emitting layer comprising a host material and a dopant material, wherein the dopant material comprises a thermally activated delayed fluorescent material and a fluorescent material; The number of the light-emitting layer is one or more than one; The thermally activated delayed fluorescent material is a thioxanthone derivative, and the thioxanthone derivative is selected from the following compounds of general formula (I): Wherein, X1 is selected from sulfone group and sulfoxide group; m, n are independently selected from integers of 0-4, R1, R2 are independently selected from H, C 1-6 Alkyl, C 2-6 Alkenyl, C 2-6 Alkynyl, C 6-14 Aryl, 5-14 membered heteroaryl; wherein the C 6-14 Aryl, 5-14 membered heteroaryl is substituted by one or more substituents R a Substitution; the substituent R a Independent: C 6-14 Aryl, 5-14 membered heteroaryl, -N(R 1 ) 2, said R 1 The same, independently selected from C 6-14 Aryl, 5-14 membered heteroaryl; The heteroatom in the 5-14 membered heteroaryl group is N; Provided that in formula I, at least one of R1 and R2 is selected from a Substituted C 6-14 Aryl or 5-14 membered heteroaryl; The fluorescent material is selected from one or more of the following structures: The host material is mCBP (3,3′-di(9H-carbazol-9-yl)-1,1′-biphenyl), CBP (4,4′-di(9-carbazolyl)biphenyl) or mCP (1,3-bis(9-carbazolyl)benzene).

2. The organic electroluminescent device according to claim 1, characterized in that: The thermally activated delayed fluorescent material is selected from the following compounds:

3. The organic electroluminescent device according to claim 1 or 2, characterized in that: The triplet energy level of the host material is higher than the singlet energy level of the thermally activated delayed fluorescent material, and the energy gap difference between the two is 0 to 2.0 eV, but not including 0.

4. The organic electroluminescent device according to claim 1 or 2, characterized in that: The energy level difference between the singlet state and the triplet state of the thermally activated delayed fluorescent material is less than 0.3 eV.

5. The organic electroluminescent device according to claim 1 or 2, characterized in that: The triplet energy level of the thermally activated delayed fluorescent material is higher than the singlet energy level of the fluorescent material, and the energy gap difference between the two is 0 to 1.5 eV, but not including 0.

6. The organic electroluminescent device according to claim 1 or 2, characterized in that: The fluorescent material accounts for 0.1-20% of the main material by mass; the thermally activated delayed fluorescent material accounts for 5-80% of the main material by mass.

7. The organic electroluminescent device according to claim 1 or 2, characterized in that: The organic electroluminescent device further comprises: an anode layer, a hole injection layer, a hole transport layer, optionally an exciton blocking layer, a light-emitting layer, an electron transport layer, an electron injection layer, and a cathode layer; the organic electroluminescent device further comprises a substrate.

8. The organic electroluminescent device according to claim 7, characterized in that: The anode is indium tin oxide; the hole injection layer is a-NPD; the hole transport layer is TCTA, TAPC; the exciton blocking layer is mCP; the electron transport layer is B4PyMPM, TmPyPB; the electron injection layer is LiF, and the cathode is Al.

9. The organic electroluminescent device according to claim 2, characterized in that: It is: ITO / a-NPD / TCTA / mCP / mCBP:15wt%T1:1wt%DBP / B4PyMPM / LiF / Al, or ITO / a-NPD / TCTA / mCP / mCBP: 25wt%T1: 1wt%DBP / mCBP: 15wt%TXO-TPA: 2wt%DBP / B4PyMPM / LiF / Al, or ITO / TAPC / CBP:10wt%T9:0.5wt%DCJTB / TmPyPB / LiF / Al, or ITO / TAPC / mCBP:10wt%T9:0.5wt%DCJTB / TmPyPB / LiF / Al, or ITO / TAPC / mCP:5wt%T9:0.5wt%DCJTB / TmPyPB / LiF / Al, or ITO / TAPC / CBP:10wt%T9:1wt%DCJTB / TmPyPB / LiF / Al; Among them, ITO is an indium tin oxide conductive film, a-NPD is N,N'-bis(naphthalene-1-yl)-N,N'-bis(phenyl)-2,2'-dimethylbenzidine, TCTA is 4,4',4"-tri(carbazole-9-yl)triphenylamine, TAPC is 4,4'-cyclohexylbis[N,N-di(4-methylphenyl)aniline], mCP is 1,3-bis(9-carbazole)benzene, mCBP is 3,3'-di(9H-carbazole-9-yl)-1,1'-biphenyl, CBP is 4,4'-di(9-carbazole)biphenyl, B4PyMPM is 4,6-bis(3,5-di(4-pyridyl)phenyl)-2-methylpyrimidine, and TmPyPB is 1,3,5-tri[(3-pyridyl)-phenyl-3-yl]benzene.

10. Use of the organic electroluminescent device according to any one of claims 1 to 9, characterized in that: It is used in display devices and daily lighting fields.

11. A display device, characterized in that: An organic electroluminescent device comprising any one of claims 1 to 9.

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