Light-emitting device, preparation method thereof and display device

Abstract

The invention discloses a light-emitting device, a preparation method thereof and a display device, and relates to the technical field of display. The light-emitting device comprises an anode, a hole function layer, a transition layer, a light-emitting layer and a cathode. Wherein the valence band energy level absolute value of the hole function layer, the valence band energy level absolute value of the transition layer and the valence band energy level absolute value of the light-emitting layer are gradually increased in sequence. According to the light-emitting device provided by the invention, the valence band energy level gradient is formed among the hole function layer, the transition layer and the light-emitting layer, so that the hole injection barrier is effectively reduced, and the hole migration rate can be improved; the transition layer can also effectively block electron tunneling, thereby improving the light emitting efficiency of the light emitting device and prolonging the service life of the light emitting device.

Description

Technical Field

[0001] The present application relates to the field of display technology, and in particular to a light-emitting device, a method for preparing the light-emitting device, and a display device including the light-emitting device. Background Art

[0002] Currently, the widely used light-emitting devices are organic light-emitting diodes (OLEDs) and quantum dot light-emitting diodes (QLEDs). OLED has become the mainstream technology in the field of display technology due to its excellent display performance, such as self-luminescence, simple structure, ultra-thinness, fast response speed, wide viewing angle, low power consumption, and flexible display. QLED has the advantages of saturated color and adjustable wavelength of emitted light, and high quantum yield of photoluminescence and electroluminescence, and has become a strong competitor of OLED in recent years.

[0003] The structure of traditional OLED and QLED devices generally includes an anode, a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, an electron injection layer and a cathode. Under the action of the electric field, the holes generated by the anode of the light-emitting diode and the electrons generated by the cathode move and are injected into the hole transport layer and the electron transport layer respectively, and finally migrate to the light-emitting layer. When the two meet in the light-emitting layer, energy excitons are generated, thereby exciting the light-emitting molecules and finally producing visible light.

[0004] The luminous efficiency of existing light-emitting devices is relatively low and needs to be further improved. Summary of the invention

[0005] In view of this, the present application provides a light-emitting device, a method for preparing the light-emitting device, and a display device including the light-emitting device.

[0006] The embodiment of the present application is implemented as follows: a light-emitting device includes: a stacked anode, a hole functional layer, a transition layer, a light-emitting layer and a cathode; wherein the absolute value of the valence band energy level of the hole functional layer, the absolute value of the valence band energy level of the transition layer, and the absolute value of the valence band energy level of the light-emitting layer increase in sequence.

[0007] Optionally, in some embodiments of the present application, the absolute value of the difference between the valence band energy level of the transition layer and the valence band energy level of the hole functional layer is greater than 0 eV and less than 1.3 eV; and / or

[0008] The absolute value of the difference between the valence band energy level of the light-emitting layer and the valence band energy level of the transition layer is greater than 0 eV and less than 1.3 eV.

[0009] Optionally, in some embodiments of the present application, the material of the hole functional layer includes a P-type semiconductor; and / or

[0010] The material of the transition layer includes N-type semiconductor.

[0011] Optionally, in some embodiments of the present application, the P-type semiconductor includes one or more of a P-type inorganic semiconductor material and a P-type organic semiconductor material; the P-type inorganic semiconductor material includes one or more of a first doped metal oxide particle, a first undoped metal oxide particle, a metal sulfide, a metal selenide and a metal nitride, and the metal oxide in the first doped metal oxide particle and the metal oxide in the first undoped metal oxide particle each independently include MoO 3 , WO 3 、NiO、CrO 3 , CuO, Cu 2 O.V 2 O 5 The doping element in the first doped metal oxide particles includes one or more of Mo, W, Ni, Cr, Cu, and V, and the metal sulfide includes CuS, MoS 3 , WS 3 One or more of the metal selenides, wherein the metal selenides include MoSe 3 ,WSe 3One or more of the above, the metal nitride includes P-type gallium nitride; the P-type organic semiconductor material includes 4,4'-N,N'-dicarbazolyl-biphenyl, N,N'-diphenyl-N,N'-bis(1-naphthyl)-1,1'-biphenyl-4,4"-diamine, N,N'-diphenyl-N,N'-bis(3-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine, N,N'-bis(3-methylphenyl)-N,N '-Bis(phenyl)-spiro, N,N'-bis(4-(N,N'-diphenyl-amino)phenyl)-N,N'-diphenylbenzidine, 4,4',4'-tri(N-carbazolyl)-triphenylamine, 4,4',4'-tri(carbazolyl-9-yl)triphenylamine, trichloroisocyanuric acid, terbium-doped phosphate-based green luminescent materials, 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene, 4,4' , 4'-tri(N-3-methylphenyl-N-phenylamino)triphenylamine, poly[(9,9'-dioctylfluorene-2,7-diyl)-co-(4,4'-(N-(4-sec-butylphenyl)diphenylamine))], poly(4-butylphenyl-diphenylamine), poly[bis(4-phenyl)(4-butylphenyl)amine], polyaniline, polypyrrole, poly(p-phenylenevinylene), poly(phenylenevinylene), poly[2-methoxy-5-(2 -ethylhexyloxy)-1,4-phenylene vinylene], poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylene vinylene], copper phthalocyanine, aromatic tertiary amines, polynuclear aromatic tertiary amines, 4,4'-bis(p-carbazolyl)-1,1'-biphenyl compounds, N,N,N',N'-tetraarylbenzidine, PEDOT, PEDOT:PSS and its derivatives, PEDOT:PSS doped with s-MoO 3 derivatives, poly(N-vinylcarbazole) and its derivatives, polymethacrylate and its derivatives, poly(9,9-octylfluorene) and its derivatives, poly(spirofluorene) and its derivatives, N,N'-di(naphthalene-1-yl)-N,N'-diphenylbenzidine, spiro NPB, nano-polycrystalline diamond, microcrystalline cellulose and tetracyanoquinodimethane, doped graphene, undoped graphene, or more thereof; and / or

[0012] The N-type semiconductor includes an N-type inorganic semiconductor material, the N-type inorganic semiconductor material includes second doped metal oxide particles, the metal oxide in the second doped metal oxide particles includes zinc oxide, and the doping element in the second doped metal oxide particles includes cadmium.

[0013] Optionally, in some embodiments of the present application, the doping molar ratio of the doping element in the metal oxide is 10% to 35%; and / or

[0014] The average particle size of the second doped metal oxide particles is 5 nm to 20 nm.

[0015] Optionally, in some embodiments of the present application, the light-emitting device further includes an electronic functional layer, wherein the electronic functional layer is disposed between the light-emitting layer and the cathode, and the electronic functional layer includes one or more of an electron injection layer and an electron transport layer.

[0016] Optionally, in some embodiments of the present application, the anode and the cathode respectively include a metal oxide electrode or a composite electrode in which a metal is arranged between doped or undoped transparent metal oxides, and the material of the metal oxide electrode includes one or more of ITO, FTO, ATO, AZO, GZO, IZO, MZO and AMO, and the composite electrode includes AZO / Ag / AZO, AZO / Al / AZO, ITO / Ag / ITO, ITO / Al / ITO, ZnO / Ag / ZnO, ZnO / Al / ZnO, ZnS / Ag / ZnS, ZnS / Al / ZnS, TiO 2 / Ag / TiO 2 and TiO 2 / Al / TiO 2 One or more of; and / or

[0017] The material of the light-emitting layer includes one or more of organic light-emitting materials and quantum dots; the organic light-emitting material includes 4,4'-bis(N-carbazole)-1,1'-biphenyl: tris[2-(p-tolyl)pyridine iridium(III)], 4,4',4"-tris(carbazole-9-yl)triphenylamine: tris[2-(p-tolyl)pyridine iridium], diaromatic anthracene derivatives, distilbene aromatic derivatives, pyrene derivatives, fluorene derivatives, TBPe fluorescent materials, TTPX fluorescent materials, TBRb fluorescent materials, DBP fluorescent materials, delayed fluorescent materials, TTA materials, One or more of TADF materials, polymers containing BN covalent bonding, HLCT materials, and Exciplex luminescent materials; the quantum dots include one or more of single-structure quantum dots, core-shell structure quantum dots, and perovskite semiconductor materials, and the materials of the single-structure quantum dots, the core materials of the core-shell structure quantum dots, and the shell materials of the core-shell structure quantum dots are independently selected from one or more of II-VI group compounds, IV-VI group compounds, III-V group compounds, and I-III-VI group compounds; the shell of the core-shell structure quantum dots includes one or more layers, wherein the II-VI group compound comprises CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, HgS, HgSe, HgTe, CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, CdZnSeS, CdZnSeTe, Cd One or more of dZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe and HgZnSTe; the IV-VI group compound includes one or more of SnS, SnSe, SnTe, PbS, PbSe, PbTe, SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, SnPbSSe, SnPbSeTe and SnPbSTe;The III-V group compound includes one or more of GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InNP, InNAs, InNSb, InPAs, InPSb, GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs and InAlPSb; the I-III-VI group compound includes CuInS; 2 、CuInSe 2 AgInS 2 One or more of the following; the perovskite semiconductor material includes doped or undoped inorganic perovskite semiconductors and organic-inorganic hybrid perovskite semiconductors; the inorganic perovskite semiconductor has the general structural formula of AMX 3 , where A is Cs + ion, M is a divalent metal cation selected from Pb 2+ Sn 2+ , Cu 2+ 、Ni 2+ 、Cd 2+ Cr 2+ , Mn 2+ 、Co 2+ , Fe 2+ ,Ge 2+ , Yb 2+ 、Eu 2+ One or more of, X is a halogen anion selected from Cl - Br - ,I - One or more of the following; the general structural formula of the organic-inorganic hybrid perovskite semiconductor is BMX 3 , wherein B is an organic amine cation selected from CH 3 (CH 2 ) n-2 NH 3 + or [NH 3 (CH 2 ) n NH 3 ] 2+ , where n≥2, M is a divalent metal cation selected from Pb 2+ Sn 2+ , Cu 2+、Ni 2+ 、Cd 2+ Cr 2+ , Mn 2+ 、Co 2+ , Fe 2+ ,Ge 2+ , Yb 2+ 、Eu 2+ One or more of, X is a halogen anion selected from Cl - Br - ,I - One or more of; and / or

[0018] The materials of the electron injection layer and the electron transport layer respectively include one or more of the third doped metal oxide particles, the third undoped metal oxide particles, IIB-VIA semiconductor materials, IIIA-VA semiconductor materials and IB-IIIA-VIA semiconductor materials, and the materials of the third undoped metal oxide particles include ZnO, TiO 2 SnO 2 、ZrO 2 、 2 O 5 One or more of the following, the metal oxide in the third doped metal oxide particles includes ZnO, TiO 2 SnO 2 、ZrO 2 、 2 O 5 、Al 2 O 3 The doping elements in the third doped metal oxide particles include one or more of Al, Mg, Li, Mn, Y, La, Cu, Ni, Zr, Ce, In, and Ga. The IIB-VIA semiconductor materials include one or more of ZnS, ZnSe, and CdS. The IIIA-VA semiconductor materials include one or more of InP and GaP. The IB-IIIA-VIA semiconductor materials include one or more of CuInS and CuGaS.

[0019] Accordingly, an embodiment of the present application further provides a method for preparing a light-emitting device, comprising:

[0020] Providing a light-emitting device preform, wherein the light-emitting device preform comprises an anode and a hole functional layer;

[0021] Providing a transition material, and disposing the transition material on a side of the hole functional layer away from the anode to form a transition layer, wherein the absolute value of the valence band energy level of the hole functional layer is smaller than the absolute value of the valence band energy level of the transition layer;

[0022] forming a light-emitting layer and a cathode on the transition layer, wherein the absolute value of the valence band energy level of the transition layer is smaller than the absolute value of the valence band energy level of the light-emitting layer, to obtain a light-emitting device;

[0023] or,

[0024] Providing a light-emitting device preform, wherein the light-emitting device preform comprises a cathode and a light-emitting layer;

[0025] Providing a transition material, and disposing the transition material on a side of the light-emitting layer away from the cathode to form a transition layer, wherein the absolute value of the valence band energy level of the transition layer is smaller than the absolute value of the valence band energy level of the light-emitting layer;

[0026] A hole functional layer and an anode are formed on the transition layer, wherein the absolute value of the valence band energy level of the hole functional layer is smaller than the absolute value of the valence band energy level of the transition layer, thereby obtaining a light-emitting device.

[0027] Optionally, in some embodiments of the present application, the absolute value of the difference between the valence band energy level of the transition layer and the valence band energy level of the hole functional layer is greater than 0 eV and less than 1.3 eV; and / or

[0028] The absolute value of the difference between the valence band energy level of the light-emitting layer and the valence band energy level of the transition layer is greater than 0 eV and less than 1.3 eV; and / or

[0029] The material of the hole functional layer includes a P-type semiconductor; and / or

[0030] The transition material includes an N-type semiconductor.

[0031] Optionally, in some embodiments of the present application, the N-type semiconductor includes an N-type inorganic semiconductor material, the N-type inorganic semiconductor material includes second doped metal oxide particles, the metal oxide in the second doped metal oxide particles includes zinc oxide, the doping element in the second doped metal oxide particles includes cadmium, and / or the doping molar ratio of the doping element in the metal oxide is 10% to 35%, and / or the average particle size of the second doped metal oxide particles is 5nm to 20nm.

[0032] Optionally, in some embodiments of the present application, the method for preparing the transition material includes:

[0033] Providing a precursor solution, wherein the precursor solution includes a metal salt and a first solvent, wherein the metal salt includes a main metal salt and a doped metal salt;

[0034] An alkaline solution is provided, wherein the alkaline solution comprises an alkali and a second solvent, and the precursor solution and the alkaline solution are mixed to obtain a transition material.

[0035] Optionally, in some embodiments of the present application, the main metal salt includes a zinc salt; and / or

[0036] The doping metal salt comprises a cadmium salt; and / or

[0037] The base includes one or more of potassium hydroxide, lithium hydroxide, sodium hydroxide, ammonium hydroxide, ethylenediamine, ethanolamine, diethanolamine, triethanolamine, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide; and / or

[0038] The first solvent and the second solvent respectively include one or more of methanol, ethanol, propanol, butanol, ethylene glycol, isopropanol, glycerol, dimethylformamide, dimethyl sulfoxide, cyclopentane, ethyl nitrate, xylene, anisole, decalin, cyclohexane, cyclohexene, methylcyclohexane, ethylcyclohexane, limonene, hexane, octane, nonane, decane, dimethylacetamide, acetyl carbonate, N-methylpyrrolidone, tetrahydrofuran, ethyl acetate, and dichloromethane.

[0039] Optionally, in some embodiments of the present application, in the precursor solution, the molar concentration of the metal salt is 0.2 mol / L to 1 mol / L; and / or

[0040] The molar ratio of the main metal salt to the doping metal salt is 1:(0.01-0.05); and / or

[0041] The molar ratio of the base to the metal salt is (2-8):1; and / or

[0042] The temperature of the precursor solution and the alkali solution after mixing is 50° C. to 70° C., and the mixing time is 2 h to 4 h.

[0043] Optionally, in some embodiments of the present application, after forming the light-emitting layer on the transition layer, the method further comprises forming an electronic functional layer and a cathode to obtain a light-emitting device; or

[0044] The light emitting device preform further includes an electronic functional layer, and the electronic functional layer is arranged between the cathode and the light emitting layer.

[0045] Correspondingly, an embodiment of the present application further provides a display device, comprising the above-mentioned light-emitting device, or a light-emitting device manufactured by the above-mentioned manufacturing method.

[0046] The light-emitting device provided by the present application forms a valence band energy level gradient between the hole functional layer, the transition layer and the light-emitting layer, which effectively reduces the hole injection barrier and increases the hole migration rate; the transition layer can also effectively block electron tunneling, thereby improving the luminous efficiency of the light-emitting device and extending the service life of the light-emitting device. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0048] Figure 1 is a schematic structural diagram of a light-emitting device provided in an embodiment of the present application;

[0049] Figure 2 is a schematic structural diagram of another light-emitting device provided in an embodiment of the present application;

[0050] Figure 3 is a flow chart of a method for preparing a positive light-emitting device provided in an embodiment of the present application;

[0051] Figure 4 It is a flow chart of the method for preparing an inverted light-emitting device provided in an embodiment of the present application.

[0052] Reference numerals:

[0053] Light-emitting device 100 ; anode 10 ; hole functional layer 20 ; hole injection layer 201 ; hole transport layer 202 ; transition layer 30 ; light-emitting layer 40 ; cathode 50 ; and electronic functional layer 60 . DETAILED DESCRIPTION

[0054] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application. In addition, it should be understood that the specific implementation methods described herein are only used to illustrate and explain the present application, and are not used to limit the present application.

[0055] In this application, unless otherwise stated, directional words such as "upper" and "lower" generally refer to the upper and lower parts of the device in actual use or working state, specifically the drawing direction in the accompanying drawings; while "inner" and "outer" refer to the outline of the device. In addition, in the description of this application, the term "including" means "including but not limited to". The terms first, second, third, etc. are used only as labels and do not impose numerical requirements or establish an order.

[0056] In this application, "and / or" describes the association relationship of associated objects, indicating that there may be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural.

[0057] In the present application, "at least one" means one or more, and "plurality" means two or more. "One or several", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple, respectively.

[0058] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0059] The structure of a light-emitting device usually consists of an anode, a hole injection layer, a hole transport layer, a light-emitting layer, an electronic functional layer, and a cathode. Electrons and holes are injected from both ends, respectively, and recombine to emit light in the quantum dot light-emitting layer. The electron transport layer of existing light-emitting devices is usually composed of nano zinc oxide particles, which have a high carrier concentration and mobility; the hole transport layer usually uses organic polymer materials, such as PVK, TFB, etc. The carrier mobility of the hole transport layer is low, and the quantum dot energy level is too deep, which will lead to difficulties in hole injection, causing holes to accumulate in the hole transport layer or at the interface layer between the hole transport layer and the quantum dot light-emitting layer for a long time, and excessive electron injection makes it easy for them to jump to the hole transport layer or its interface layer with the quantum dot light-emitting layer, which ultimately leads to the recombination of electrons and holes in the non-light-emitting layer, and the loss of capacity through Auger recombination, which seriously affects the efficiency and life of the light-emitting device.

[0060] The technical solution of this application is as follows:

[0061] See also Figure 1 The present application provides a light-emitting device 100, comprising: a stacked anode 10, a hole functional layer 20, a transition layer 30, a light-emitting layer 40 and a cathode 50; wherein the absolute value of the valence band energy level of the hole functional layer 20, the absolute value of the valence band energy level of the transition layer 30, and the absolute value of the valence band energy level of the light-emitting layer 20 increase in sequence.

[0062] The light-emitting device 100 provided in the present application has an additional transition layer 30 between the hole functional layer 20 and the light-emitting layer 40, and the absolute value of the valence band energy level of the hole functional layer 20, the absolute value of the valence band energy level of the transition layer 30, and the absolute value of the valence band energy level of the light-emitting layer 40 are increased successively, so that a valence band energy level gradient is formed between the hole functional layer 20 and the light-emitting layer 40, which effectively reduces the hole injection barrier, increases the hole migration rate, and reduces the performance degradation of the light-emitting device 100 caused by the accumulation of holes at the barrier interface; the transition layer 30 can also effectively block electron tunneling and avoid the recombination of electrons and holes in the non-light-emitting layer 40, thereby improving the luminous efficiency of the light-emitting device 100 and extending the service life of the light-emitting device 100.

[0063] In some embodiments, the absolute value of the difference between the valence band energy level of the transition layer and the valence band energy level of the hole functional layer is greater than 0 eV and less than 1.3 eV, for example, greater than 0.01 eV and less than 1.2 eV, greater than 0.1 eV and less than 1 eV, greater than 0.2 eV and less than 0.8 eV, greater than 0.3 eV and less than 0.6 eV, greater than 0.4 eV and less than 0.5 eV, etc. Within the valence band energy level difference range, the injection barrier of the holes from the hole functional layer 20 to the transition layer 30 is small, which is conducive to the transmission of holes from the hole functional layer 20 to the transition layer 30.

[0064] In some embodiments, the absolute value of the difference between the valence band energy level of the light-emitting layer and the valence band energy level of the transition layer is greater than 0 eV and less than 1.3 eV, for example, greater than 0.01 eV and less than 1.2 eV, greater than 0.1 eV and less than 1 eV, greater than 0.2 eV and less than 0.8 eV, greater than 0.3 eV and less than 0.6 eV, greater than 0.4 eV and less than 0.5 eV, etc. Within the valence band energy level difference range, the injection barrier of the holes from the transition layer 30 to the light-emitting layer 40 is small, which is conducive to the transmission of holes from the transition layer 30 to the light-emitting layer 40.

[0065] In some embodiments, the hole functional layer 20 includes one or more of a hole injection layer 201 and a hole transport layer 202 , and the hole injection layer 201 is disposed between the anode 10 and the hole transport layer 202 .

[0066] In some embodiments, the material of the hole function layer 20 includes a P-type semiconductor.

[0067] Furthermore, the P-type semiconductor includes a P-type inorganic semiconductor material and a P-type organic semiconductor material.

[0068] Further, the P-type inorganic semiconductor material includes one or more of first doped metal oxide particles, first undoped metal oxide particles, metal sulfide, metal selenide and metal nitride, and the metal oxide in the first doped metal oxide particles and the metal oxide in the first undoped metal oxide particles each independently include MoO 3 , WO 3 、NiO、CrO 3 , CuO, Cu 2 O.V 2 O 5 The doping element in the first doped metal oxide particles includes one or more of Mo, W, Ni, Cr, Cu, and V, and the metal sulfide includes CuS, MoS 3 , WS 3 One or more of the metal selenides, wherein the metal selenides include MoSe 3 ,WSe 3 One or more of the above, wherein the metal nitride comprises P-type gallium nitride.

[0069] The P-type organic semiconductor material includes 4,4'-N,N'-dicarbazolyl-biphenyl, N,N'-diphenyl-N,N'-bis(1-naphthyl)-1,1'-biphenyl-4,4"-diamine, N,N'-diphenyl-N,N'-bis(3-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine, N,N'-bis(3-methylphenyl)-N,N'-bis(phenyl)-spiro, N,N'-di( 4-(N,N'-diphenyl-amino)phenyl)-N,N'-diphenylbenzidine, 4,4',4'-tri(N-carbazolyl)-triphenylamine, 4,4',4'-tri(carbazolyl-9-yl)triphenylamine, trichloroisocyanuric acid, terbium-doped phosphate-based green luminescent materials, 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene, 4,4',4'-tri(N-3-methyl) phenyl-N-phenylamino)triphenylamine, poly[(9,9'-dioctylfluorene-2,7-diyl)-co-(4,4'-(N-(4-sec-butylphenyl)diphenylamine))], poly(4-butylphenyl-diphenylamine), poly[bis(4-phenyl)(4-butylphenyl)amine], polyaniline, polypyrrole, poly(p-phenylenevinylene), poly(phenylenevinylene), poly[2-methoxy-5-(2-ethylhexyloxy) )-1,4-phenylene vinylene], poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylene vinylene], copper phthalocyanine, aromatic tertiary amines, polynuclear aromatic tertiary amines, 4,4'-bis(p-carbazolyl)-1,1'-biphenyl compounds, N,N,N',N'-tetraarylbenzidine, PEDOT, PEDOT:PSS and its derivatives, PEDOT:PSS doped with s-MoO 3 One or more of the following: derivatives of poly(N-vinylcarbazole) and its derivatives, polymethacrylate and its derivatives, poly(9,9-octylfluorene) and its derivatives, poly(spirofluorene) and its derivatives, N,N'-di(naphthalene-1-yl)-N,N'-diphenylbenzidine, spiro NPB, nano-polycrystalline diamond, microcrystalline cellulose and tetracyanoquinodimethane, doped graphene, and undoped graphene.

[0070] In some embodiments, the material of the transition layer 30 includes an N-type semiconductor.

[0071] Furthermore, the N-type semiconductor includes an N-type inorganic semiconductor material, the N-type inorganic semiconductor material includes second doped metal oxide particles, the metal oxide in the second doped metal oxide particles includes zinc oxide, and the doping element in the second doped metal oxide particles includes cadmium.

[0072] Specifically, the N-type semiconductor includes cadmium-doped zinc oxide.

[0073] In some embodiments, in the second doped metal oxide particles, the doping molar ratio of the doping element in the metal oxide is 10% to 35%, for example, 12% to 32%, 15% to 30%, 18% to 28%, 20% to 25%, 22% to 24%, etc. Within the doping ratio range of the doping element, it is beneficial for the doping element to effectively adjust the valence band energy level of the metal oxide, thereby promoting the transmission of holes.

[0074] When the material of the transition layer 30 is cadmium-doped zinc oxide, the absolute value of the valence band of zinc oxide is about 7.2 eV, the band gap of cadmium oxide is 2.3 eV, and the lattice constant of cadmium oxide is close to that of zinc oxide. Doping cadmium into zinc oxide can reduce the stress and defects of the material caused by lattice mismatch, so that Cd 2+ After entering the ZnO lattice, the molecular orbital is rearranged, thereby changing the relative position of the valence band top and the conduction band bottom, and narrowing the band gap, so that the valence band energy level of the cadmium-doped zinc oxide is between the hole functional layer 20 and the light-emitting layer 40, which can block electron relaxation and promote the transmission of holes.

[0075] It should be noted that the material of the hole functional layer 20 is a P-type semiconductor, and the material of the transition layer 30 is an N-type semiconductor. A PN junction can be formed between the P-type semiconductor and the N-type semiconductor. The direction of the current is transmitted from the hole functional layer 20 to the light-emitting layer 40. Under the action of the PN junction, the holes will be accelerated, thereby improving the hole transmission efficiency, thereby improving the hole and electron balance of the light-emitting device 100, promoting the holes and electrons to recombine and emit light in the light-emitting layer 40, and improving the light-emitting efficiency of the light-emitting device 100.

[0076] Furthermore, when the material of the hole functional layer 20 is a P-type inorganic semiconductor material, the properties of the hole functional layer 20 and the transition layer are closer and the stability is better. When the material of the hole functional layer 20 is a P-type organic semiconductor material, the P-type organic semiconductor material can inject more holes from the anode 10 side, promoting the injection and transmission of holes.

[0077] In some embodiments, the average particle size of the second doped metal oxide particles is 5 nm to 20 nm, for example, 6 nm to 19 nm, 8 nm to 18 nm, 10 nm to 16 nm, 12 nm to 15 nm, 13 nm to 14 nm, etc.

[0078] In some embodiments, the material of the light-emitting layer 40 includes one or more of an organic light-emitting material and a quantum dot light-emitting material.

[0079] The organic light-emitting material includes CBP:Ir(mppy) 3(4,4'-bis(N-carbazole)-1,1'-biphenyl:tris[2-(p-tolyl)pyridine iridium(III)]), TCTX:Ir(mmpy)(4,4',4"-tri(carbazole-9-yl)triphenylamine:tris[2-(p-tolyl)pyridine iridium]), diaromatic anthracene derivatives, distilbene aromatic derivatives, pyrene derivatives, fluorene derivatives, TBPe fluorescent materials, TTPX fluorescent materials, TBRb fluorescent materials, DBP fluorescent materials, delayed fluorescent materials, TTA materials, TADF (thermally activated delay) materials, polymers containing BN covalent bonds, HLCT (hybridized localized charge transfer excited state) materials, Exciplex (exciplex) luminescent materials, one or more thereof.

[0080] The quantum dot luminescent material includes one or more of single structure quantum dots, core-shell structure quantum dots and perovskite semiconductor materials.

[0081] The material of the single structure quantum dots, the core material of the core-shell structure quantum dots and the shell material of the core-shell structure quantum dots can be selected from but not limited to one or more of II-VI group compounds, IV-VI group compounds, III-V group compounds and I-III-VI group compounds. The shell layer of the core-shell structure quantum dots includes one or more layers, and the II-VI group compounds include one or more of CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, HgS, HgSe, HgTe, CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe and HgZnSTe. The IV-VI group compounds include one or more of SnS, SnSe, SnTe, PbS, PbSe, PbTe, SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, SnPbSSe, SnPbSeTe, and SnPbSTe. The III-V group compounds include one or more of GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InNP, InNAs, InNSb, InPAs, InPSb, GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs and InAlPSb. The I-III-VI group compounds include CuInS 2 、CuInSe 2 AgInS 2 One or more of the .

[0082] As an example, the core-shell structured quantum dots include one or more of CdSe / CdSeS / CdS, InP / ZnSeS / ZnS, CdZnSe / ZnSe / ZnS, CdSeS / ZnSeS / ZnS, CdSe / ZnS, CdSe / ZnSe / ZnS, ZnSe / ZnS, ZnSeTe / ZnS, CdSe / CdZnSeS / ZnS and InP / ZnSe / ZnS.

[0083] The perovskite semiconductor material includes a doped or undoped inorganic perovskite semiconductor, or an organic-inorganic hybrid perovskite semiconductor. The inorganic perovskite semiconductor has a general structural formula of AMX 3 , where A is Cs + ion, M is a divalent metal cation selected from Pb 2+ Sn 2+ , Cu 2+ 、Ni 2+ 、Cd 2+ Cr 2+ , Mn 2+ 、Co 2+ , Fe 2+ ,Ge 2+ , Yb 2+ 、Eu 2+ One or more of, X is a halogen anion selected from Cl - Br - ,I - The general structural formula of the organic-inorganic hybrid perovskite semiconductor is BMX 3 , wherein B is an organic amine cation selected from CH 3 (CH 2 ) n-2 NH 3 + or [NH 3 (CH 2 ) n NH 3 ] 2+ , where n≥2, M is a divalent metal cation selected from Pb 2+ Sn 2+ , Cu 2+ 、Ni 2+ 、Cd 2+ Cr 2+ , Mn 2+ 、Co 2+ , Fe 2+ ,Ge 2+ , Yb 2 + 、Eu 2+One or more of, X is a halogen anion selected from Cl - Br - ,I - One or more of the .

[0084] In some embodiments, the materials of the anode 10 and the cathode 50 include one or more of metal, carbon material and metal oxide respectively; the metal includes one or more of Al, Ag, Cu, Mo, Au, Ba, Ca, Yb and Mg; the carbon material includes one or more of graphite, carbon nanotubes, graphene and carbon fiber; the metal oxide includes a metal oxide electrode or a composite electrode in which a metal is arranged between doped or undoped transparent metal oxides, and the material of the metal oxide electrode includes one or more of ITO, FTO, ATO, AZO, GZO, IZO, MZO and AMO, and the composite electrode includes AZO / Ag / AZO, AZO / Al / AZO, ITO / Ag / ITO, ITO / Al / ITO, ZnO / Ag / ZnO, ZnO / Al / ZnO, ZnS / Ag / ZnS, ZnS / Al / ZnS, TiO 2 / Ag / TiO 2 and TiO 2 / Al / TiO 2 One or more of the above. Wherein, “ / ” indicates a stacked structure, for example, AZO / Ag / AZO indicates a composite electrode including an AZO layer, an Ag layer and an AZO layer stacked in sequence.

[0085] In some embodiments, see Figure 2 The light emitting device 100 further includes an electronic functional layer 60 , and the electronic functional layer 60 is disposed between the light emitting layer 40 and the cathode 50 .

[0086] In some embodiments, the electronic functional layer 60 includes one or more of an electron injection layer and an electron transport layer.

[0087] In some embodiments, the materials of the electron injection layer and the electron transport layer include one or more of doped or undoped semiconductor particles, quinoxaline compounds, imidazole compounds, triazine compounds, fluorene compounds, and hydroxyquinoline compounds. The semiconductor particles include one or more of zinc oxide, barium oxide, nickel oxide, titanium oxide, tin oxide, tantalum oxide, zirconium oxide, cadmium sulfide, zinc sulfide, molybdenum sulfide, tungsten sulfide, copper sulfide, zinc selenide, indium phosphide, gallium phosphide, and barium titanate, and the doped elements include one or more of indium, gallium, aluminum, magnesium, lithium, manganese, yttrium, lanthanum, copper, nickel, zirconium, cerium, and gadolinium.

[0088] In some embodiments, the thickness of the anode 10 is 40 nm to 100 nm, for example, 45 nm to 95 nm, 50 nm to 90 nm, 55 nm to 85 nm, 60 nm to 80 nm, 65 nm to 70 nm, etc.

[0089] In some embodiments, the thickness of the hole functional layer 20 is 20 nm to 60 nm, for example, 22 nm to 55 nm, 24 nm to 50 nm, 26 nm to 45 nm, 28 nm to 40 nm, 30 nm to 35 nm, etc.

[0090] Furthermore, the hole injection layer 201 has a thickness of 20 nm to 50 nm, for example, 22 nm to 48 nm, 25 nm to 45 nm, 28 nm to 42 nm, 30 nm to 40 nm, 32 nm to 35 nm, etc.

[0091] The thickness of the hole transport layer 202 is 30 nm to 60 nm, for example, 32 nm to 58 nm, 35 nm to 55 nm, 38 nm to 52 nm, 40 nm to 50 nm, 42 nm to 48 nm, etc.

[0092] In some embodiments, the thickness of the transition layer 30 is 10 nm to 20 nm, for example, 11 nm to 19 nm, 12 nm to 18 nm, 13 nm to 17 nm, 14 nm to 16 nm, etc. Within the thickness range, the transition layer 30 can improve the transmission efficiency of holes and prevent electrons and holes from being recombined at the interface between the hole functional layer 20 and the light emitting layer 40.

[0093] In some embodiments, the thickness of the light emitting layer 40 is 20 nm to 50 nm, for example, 22 nm to 48 nm, 25 nm to 45 nm, 28 nm to 42 nm, 30 nm to 40 nm, 32 nm to 35 nm, etc.

[0094] In some embodiments, the thickness of the electronic functional layer 60 is 20 nm to 60 nm, for example, 22 nm to 55 nm, 24 nm to 50 nm, 26 nm to 45 nm, 28 nm to 40 nm, 30 nm to 35 nm, etc.

[0095] In some embodiments, the thickness of the cathode 50 is 30 nm to 80 nm, for example, 35 nm to 75 nm, 40 nm to 70 nm, 45 nm to 65 nm, 50 nm to 60 nm, 52 nm to 55 nm, etc.

[0096] See also Figure 3 The present application also provides a method for preparing a light emitting device 100, comprising:

[0097] S11: providing a light-emitting device preform, wherein the light-emitting device preform comprises an anode 10 and a hole functional layer 20;

[0098] S12: providing a transition material, and disposing the transition material on a side of the hole functional layer 20 away from the anode 10 to form a transition layer 30, wherein the absolute value of the valence band energy level of the hole functional layer 20 is smaller than the absolute value of the valence band energy level of the transition layer 30;

[0099] S13: forming a light-emitting layer 40 and a cathode 50 on the transition layer 30 , wherein the absolute value of the valence band energy level of the transition layer is smaller than the absolute value of the valence band energy level of the light-emitting layer, and obtaining a light-emitting device 100 .

[0100] It can be understood that the above-mentioned light emitting device 100 is a normal light emitting device 100. In other embodiments, the light emitting device 100 can also be an inverted light emitting device 100. Figure 4 The method for preparing the inverted light emitting device 100 comprises:

[0101] S21: providing a light-emitting device preform, wherein the light-emitting device preform comprises a cathode 50 and a light-emitting layer 40;

[0102] S22: providing a transition material, and disposing the transition material on a side of the light-emitting layer 40 away from the cathode 50 to form a transition layer 30, wherein the absolute value of the valence band energy level of the transition layer 30 is smaller than the absolute value of the valence band energy level of the light-emitting layer 40;

[0103] S23: forming a hole functional layer 20 and an anode 10 on the transition layer 30 , wherein the material of the hole functional layer 20 includes a hole material, and the absolute value of the valence band energy level of the hole functional layer 20 is smaller than the absolute value of the valence band energy level of the transition layer 30 , to obtain a light-emitting device 100 .

[0104] In S12:

[0105] In some embodiments, the transition material includes cadmium-doped zinc oxide.

[0106] Furthermore, in the cadmium-doped zinc oxide, the doping molar ratio of cadmium is 10% to 35%, for example, 12% to 32%, 15% to 30%, 18% to 28%, 20% to 25%, 22% to 24%, etc. Within the doping ratio range of cadmium, it is beneficial to effectively adjust the valence band energy level of the cadmium-doped zinc oxide, thereby promoting the transmission of holes.

[0107] In some embodiments, the method for preparing the transition material comprises:

[0108] S121, providing a precursor solution, wherein the precursor solution includes a metal salt and a first solvent, and the metal salt includes a main metal salt and a doped metal salt;

[0109] S122, providing an alkaline solution, wherein the alkaline solution includes an alkali and a second solvent, and mixing the precursor solution and the alkaline solution to obtain a transition material.

[0110] In some embodiments, the primary metal salt comprises a zinc salt.

[0111] Furthermore, the zinc salt includes one or more of zinc sulfate, zinc chloride, zinc sulfamate, zinc bromide, zinc hydroxide, carbonyl zinc, zinc nitrate, zinc acetate and zinc acetate tetrahydrate.

[0112] In some embodiments, the doping metal salt comprises a cadmium salt.

[0113] Furthermore, the cadmium salt includes one or more of cadmium sulfate, cadmium chloride, cadmium sulfamate, cadmium bromide, cadmium hydroxide, carbonyl cadmium, cadmium nitrate, cadmium acetate and cadmium acetate tetrahydrate.

[0114] In some embodiments, the first solvent includes one or more of methanol, ethanol, propanol, butanol, ethylene glycol, isopropanol, glycerol, dimethylformamide, dimethyl sulfoxide, cyclopentane, ethyl nitrate, xylene, anisole, decalin, cyclohexane, cyclohexene, methylcyclohexane, ethylcyclohexane, limonene, hexane, octane, nonane, decane, dimethylacetamide, acetyl carbonate, N-methylpyrrolidone, tetrahydrofuran, ethyl acetate, and dichloromethane.

[0115] In some embodiments, in the precursor solution, the molar concentration of the metal salt is 0.2 mol / L to 1 mol / L, for example, 0.3 mol / L to 0.9 mol / L, 0.4 mol / L to 0.8 mol / L, 0.5 mol / L to 0.6 mol / L, etc. Within the molar concentration range, the metal salt is conducive to uniform dispersion.

[0116] In some embodiments, the molar ratio of the main metal salt to the doping metal salt is 1:(0.01-0.05), for example, 1:(0.015-0.045), 1:(0.02-0.04), 1:(0.025-0.035), 1:(0.03-0.032), etc. Within the molar ratio range, the doping metal salt can adjust the valence band energy level of the main metal salt to be between the valence band energy levels of the hole material and the luminescent material.

[0117] In the S112:

[0118] In some embodiments, the base includes one or more of potassium hydroxide, lithium hydroxide, sodium hydroxide, ammonium hydroxide, ethylenediamine, ethanolamine, diethanolamine, triethanolamine, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide.

[0119] In some embodiments, the second solvent includes one or more of methanol, ethanol, propanol, butanol, ethylene glycol, isopropanol, glycerol, dimethylformamide, dimethyl sulfoxide, cyclopentane, ethyl nitrate, xylene, anisole, decalin, cyclohexane, cyclohexene, methylcyclohexane, ethylcyclohexane, limonene, hexane, octane, nonane, decane, dimethylacetamide, acetyl carbonate, N-methylpyrrolidone, tetrahydrofuran, ethyl acetate, and dichloromethane.

[0120] In some embodiments, the molar ratio of the base to the metal salt is (2-8):1, for example, (2.5-7.5):1, (3-7):1, (3.5-6.5):1, (4-6):1, (5-5.5):1, etc. Within the molar ratio range, it is beneficial to promote the full reaction of the base and the metal salt.

[0121] In some embodiments, the temperature of the precursor solution and the alkali solution after mixing is 50°C to 70°C, for example, 52°C to 68°C, 54°C to 66°C, 55°C to 65°C, 56°C to 62°C, 58°C to 60°C, etc. The time is 2h to 4h, for example, 2.2h to 3.8h, 2.4h to 3.6h, 2.5h to 3.5h, 2.6h to 3.2h, 2.8h to 3h, etc. In this way, it is beneficial to accelerate the reaction rate and improve the yield of the transition material.

[0122] In some embodiments, the method of mixing the precursor solution and the alkali solution comprises: adding the precursor solution dropwise to the alkali solution. It is understood that the dropwise addition method makes it easier to control the amount of the precursor solution and facilitates the precursor solution and the alkali solution to be fully mixed.

[0123] In some embodiments, the precursor solution and the alkali solution are mixed and then dried to obtain a transition material.

[0124] In some embodiments, the drying temperature is 50°C to 100°C, for example, 55°C to 95°C, 60°C to 90°C, 65°C to 85°C, 70°C to 80°C, 72°C to 78°C, etc. The drying time is 5h to 8h, for example, 5.2h to 7.8h, 5.5h to 7.5h, 5.8h to 7.2h, 6h to 7h, 6.2h to 6.8h, etc. In this way, the first solvent and unreacted alkali solution can be effectively removed to obtain a high-purity transition material.

[0125] It can be understood that the method for forming the transition layer 30 can adopt conventional techniques in the art, such as chemical methods or physical methods. Among them, the chemical method includes chemical vapor deposition, continuous ion layer adsorption and reaction method, anode 10 oxidation method, electrolytic deposition method, and coprecipitation method. The physical method includes physical coating method and solution method, among which the physical coating method includes: thermal evaporation coating method, electron beam evaporation coating method, magnetron sputtering method, multi-arc ion coating method, physical vapor deposition method, atomic layer deposition method, pulsed laser deposition method, etc.; the solution method can be spin coating method, printing method, inkjet printing method, blade coating method, printing method, dip pulling method, immersion method, spraying method, roll coating method, casting method, slit coating method and strip coating method, etc.

[0126] In at least one embodiment, when preparing the upright light-emitting device 100, the method for forming the transition layer 30 is a solution method, including: providing a transition material, dissolving the transition material in a third solvent to obtain a transition material dispersion, and disposing the transition material dispersion on a side of the hole functional layer 20 away from the anode 10 to obtain the transition layer 30.

[0127] Accordingly, when preparing the inverted light-emitting device 100, the method for forming the transition layer 30 is a solution method, including: providing a transition material, dissolving the transition material in a third solvent to obtain a transition material dispersion, and setting the transition material dispersion on the side of the light-emitting layer 40 away from the cathode 50 to obtain the transition layer 30.

[0128] In some embodiments, the third solvent includes one or more of methanol, ethanol, propanol, butanol, ethylene glycol, isopropanol, glycerol, dimethylformamide, dimethyl sulfoxide, cyclobutane, ethyl nitrate, xylene, anisole, decalin, cyclohexane, cyclohexene, methylcyclohexane, ethylcyclohexane, limonene, hexane, octane, nonane, decane, dimethylacetamide, acetyl carbonate, N-methylpyrrolidone, tetrahydrofuran, ethyl acetate, and dichloromethane.

[0129] In some embodiments, in the transition material dispersion, the mass concentration of the transition material is 5 mg / mL to 10 mg / mL, for example, 5.5 mg / mL to 9.5 mg / mL, 6 mg / mL to 9 mg / mL, 6.5 mg / mL to 8.5 mg / mL, 7 mg / mL to 8 mg / mL, 7.2 mg / mL to 7.5 mg / mL, etc. Within the mass concentration range, the dissolution and dispersion of the transition material is facilitated.

[0130] In S13:

[0131] In some embodiments, after forming the light-emitting layer 40 on the transition layer 30 , the electronic functional layer 60 and the cathode 50 are further formed to obtain the light-emitting device 100 .

[0132] Correspondingly, when preparing the inverted light-emitting device 100 , the light-emitting device preform further includes an electronic functional layer 60 , and the electronic functional layer 60 is disposed between the cathode 50 and the light-emitting layer 40 .

[0133] In some embodiments, the electronic functional layer 60 includes one or more of an electron injection layer and an electron transport layer.

[0134] The materials and thicknesses of the anode 10 , cathode 50 , light-emitting layer 40 , hole functional layer 20 , and electron functional layer 60 are as mentioned above and will not be described in detail here.

[0135] In a third aspect, the present application further relates to a display device, which includes the light-emitting device 100 .

[0136] The display device can be any electronic product with a display function, including but not limited to smart phones, tablet computers, laptops, digital cameras, digital video cameras, smart wearable devices, smart weighing electronic scales, car displays, televisions or e-book readers, among which smart wearable devices can be, for example, smart bracelets, smart watches, virtual reality (VR) helmets, etc.

[0137] The present application is described in detail below through specific embodiments. The following embodiments are only partial embodiments of the present application and are not limitations of the present application.

[0138] Example 1

[0139] This embodiment provides a light emitting device, and the preparation method is as follows:

[0140] Providing an ITO glass, wherein the thickness of the ITO glass is 1.8 mm, using a cotton swab dipped in water to wipe the surface of the ITO glass to remove impurities visible to the naked eye, then using deionized water, acetone, ethanol and isopropanol to ultrasonically clean the ITO glass for 15 minutes, and then blowing it dry with nitrogen to obtain a 50 nm anode;

[0141] Take 0.5g of nickel acetylacetonate, dissolve it in 30mL of butanol, stir it evenly in a 60℃ water bath for 50min, then place it in a 100mL polytetrafluoroethylene reactor, react it at 180℃ in a forced air drying oven for 8h, cool it naturally to room temperature, separate the centrifugal precipitate, wash it with deionized water and anhydrous ethanol for 3 times, dry it at 110℃ for 8h to obtain nickel oxide, dissolve it in an ethanol solution to prepare a 30mg / mL nickel oxide solution;

[0142] The nickel oxide solution was spin-coated on the ITO anode and annealed at 150° C. for 15 min to obtain a 40 nm hole functional layer, wherein the absolute value of the valence band energy level of the hole functional layer was 5.4 eV;

[0143] Add zinc acetate and cadmium sulfate to 100 mL of ethanol to form a solution with a total concentration of 0.5 mol / L, wherein the zinc ion: cadmium ion (molar ratio) is 1:0.03, stir and dissolve at a constant temperature of 70°C, then add potassium hydroxide dissolved in ethanol alkali solution dropwise, wherein the sum of hydroxide: zinc ion and cadmium ion (molar ratio) is 2:1, continue stirring at 70°C for 3 hours to obtain a uniform transparent solution, dry it at 60°C for 7 hours to obtain cadmium-doped zinc oxide, dissolve it in ethanol to prepare an 8 mg / mL cadmium-doped zinc oxide solution;

[0144] 15 μL of cadmium-doped zinc oxide solution was taken with a pipette and dropped on the surface of the hole functional layer, followed by spin coating at 5000 rpm for 15 seconds, and then annealed at 110°C for 15 minutes to obtain a 15 nm transition layer, wherein the absolute value of the valence band energy level of the transition layer was 6.2 eV;

[0145] CdZnSe quantum dots were dissolved in n-hexane to prepare a quantum dot solution with a concentration of 15 mg / mL; 45 μL was taken with a pipette and dropped on the transition layer for spin coating at a speed of 3500 rpm for 45 seconds, followed by annealing at a temperature of 120°C for 15 minutes to obtain a 30 nm quantum dot light-emitting layer, wherein the absolute value of the valence band energy level of the light-emitting layer was 6.7 eV;

[0146] Prepare 20 mL of 1 mol / L tetramethylammonium hydroxide ethanol solution, drop by drop in 10 mL of 0.3 mol / L zinc acetate dimethyl sulfoxide solution at room temperature, continue stirring for 1.5 h after the dropwise addition, take 8 mL of the above solution and mix with 15 mL of ethyl acetate, and centrifuge at a speed of 4000 rpm for 4 min, repeat three times, the lower precipitate is zinc oxide nanoparticles, dissolve the nanoparticles in ethanol solution to prepare a zinc oxide solution with a concentration of 25 mg / mL;

[0147] 40 μL of zinc oxide solution was sucked with a pipette and slowly dripped on the light-emitting layer for spin coating at a speed of 4000 rpm for 30 seconds, followed by annealing at a temperature of 140°C for 15 minutes to obtain a 30 nm electronic functional layer;

[0148] After placing the device into the vacuum coating machine and pumping the vacuum to 4×10 -6 mbar, firstly, the magnesium target is evaporated. The Ag target was turned on and the Ag target was deposited at a rate of 20 nm. The cathode was obtained by evaporating 35 nm at a rate of 100 nm.

[0149] The device is encapsulated with ultraviolet curing adhesive to obtain a light-emitting device.

[0150] Example 2

[0151] This embodiment is basically the same as Embodiment 1, except that in this embodiment, the CdZnSe quantum dots in the light-emitting layer are replaced with CdSeS, wherein the absolute value of the valence band energy level of the light-emitting layer is 6.6V.

[0152] Example 3

[0153] This embodiment is substantially the same as Embodiment 1, except that, in this embodiment, the molar ratio of zinc ions to cadmium ions is 1:0.01, wherein the absolute value of the valence band energy level of the transition layer is 6.6 eV.

[0154] Example 4

[0155] This embodiment is substantially the same as the embodiment 1, except that, in this embodiment, the molar ratio of zinc ions to cadmium ions is 1:0.05, wherein the absolute value of the valence band energy level of the transition layer is 5.8 eV.

[0156] Example 5

[0157] This embodiment is substantially the same as Embodiment 1, except that the thickness of the transition layer in this embodiment is 10 nm.

[0158] Example 6

[0159] This embodiment is substantially the same as Embodiment 1, except that the thickness of the transition layer in this embodiment is 20 nm.

[0160] Example 7

[0161] This embodiment is basically the same as Embodiment 1, except that, in this embodiment, a PRDOT:PSS hole injection layer is first set on the ITO anode, and then a hole transport layer is prepared according to the method of the hole functional layer, and then a transition layer, an electronic functional layer and a cathode are prepared on the hole transport layer.

[0162] Comparative Example 1

[0163] This comparative example is substantially the same as Example 1, except that no transition layer is provided in this comparative example.

[0164] Comparative Example 2

[0165] This comparative example is substantially the same as Example 1, except that no transition layer is provided in this comparative example, and the zinc oxide material of the electronic functional layer is replaced by a cadmium-doped zinc oxide material of the transition layer.

[0166] Comparative Example 3

[0167] This comparative example is substantially the same as Example 1, except that in this comparative example, a transition layer is disposed between the electronic functional layer and the light-emitting layer.

[0168] The current efficiency CE and the maximum external quantum efficiency EQE of the light emitting devices of Examples 1 to 7 and Comparative Examples 1 to 3 were measured. max , and T95@1k nit test to obtain the current efficiency CE and maximum external quantum efficiency EQE of the light-emitting device max , and T95@1k nit. The test results are shown in Table 1.

[0169] The current efficiency CE is calculated as follows: the current efficiency is obtained by dividing the brightness of the light-emitting device by the current passing through the light-emitting device, and its unit is cd / A.

[0170] The maximum external quantum efficiency was measured by controlling the efficiency test system built by QE PRO spectrometer, Keithley 2400, and Keithley 6485 through LabView, with a driving current of 2 mA.

[0171] T95@1k nit is tested using a 128-channel life test system customized by Guangzhou New Vision Company. The system architecture is a constant voltage and constant current source to drive QLED, test changes in voltage or current, photodiode detectors and test systems to test changes in QLED brightness (photocurrent), and a brightness meter to test and calibrate QLED brightness (photocurrent) to obtain the time it takes for the initial brightness of the light-emitting diode to decay to 95%, with a driving current of 2mA. T95@1k nit refers to the time it takes for the initial brightness of the device to decay to 95%, and is converted to the aging time under 1k nit.

[0172] Table 1

[0173]

[0174] From Table 1, we can see that:

[0175] It can be seen from Examples 1 to 2 and Comparative Example 1 that the provision of a transition layer between the hole functional layer and the light-emitting layer can effectively improve the maximum external quantum efficiency, current efficiency and service life of the light-emitting device. This is because the holes are transferred from the hole functional layer to the light-emitting layer through the transition layer, which reduces the hole injection barrier and promotes hole injection into the light-emitting layer and electron recombination luminescence.

[0176] It can be seen from Example 1, Examples 3 to 4 and Comparative Example 1 that the cadmium doping amount affects the valence band energy level of the cadmium-doped zinc oxide. The more cadmium doping, the lower the valence band energy level of the cadmium-doped zinc oxide. The performance of the light-emitting device of Example 1 is better than that of the light-emitting devices of Examples 3 and 4. This is because when the valence band energy level of the cadmium-doped zinc oxide is appropriate, it is beneficial for holes to be transferred from the hole functional layer to the transition layer, and from the transition layer to the light-emitting layer, thereby avoiding the accumulation of holes at the interface between the hole functional layer and the light-emitting layer.

[0177] It can be seen from Example 1, Examples 5 to 7 and Comparative Example 1 that when the thickness of the transition layer is appropriate, it is beneficial to the transmission of holes; adding a hole injection layer has little effect on the performance of the light-emitting device. Compared with the light-emitting device of Comparative Example 1, the maximum external quantum efficiency, current efficiency and service life of the light-emitting devices of Example 1 and Examples 5 to 7 are significantly improved;

[0178] From Example 1 and Comparative Examples 2-3, it can be seen that using cadmium-doped zinc oxide as the material on the electronic functional side has little effect on electron injection, while adding a layer of cadmium-doped zinc oxide as a transition layer between the light-emitting layer and the hole functional layer can effectively increase the migration rate of holes and improve the performance of the light-emitting device.

[0179] The light-emitting device and its preparation method, and the display device provided in the embodiments of the present application are introduced in detail above. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method of the present application and its core idea; at the same time, for technical personnel in this field, according to the idea of ​​the present application, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A light emitting device, characterized in that: include: An anode, a hole functional layer, a transition layer, a light-emitting layer and a cathode are stacked; wherein the absolute value of the valence band energy level of the hole functional layer, the absolute value of the valence band energy level of the transition layer and the absolute value of the valence band energy level of the light-emitting layer increase in sequence.

2. The light emitting device according to claim 1, wherein The absolute value of the difference between the valence band energy level of the transition layer and the valence band energy level of the hole functional layer is greater than 0 eV and less than 1.3 eV; and / or An absolute value of a difference between a valence band energy level of the light-emitting layer and a valence band energy level of the transition layer is greater than 0 eV and less than 1.3 eV.

3. The light emitting device according to claim 1, wherein The material of the hole functional layer includes a P-type semiconductor; and / or The material of the transition layer includes N-type semiconductor.

4. The light emitting device according to claim 3, wherein The P-type semiconductor includes one or more of a P-type inorganic semiconductor material and a P-type organic semiconductor material; the P-type inorganic semiconductor material includes one or more of a first doped metal oxide particle, a first undoped metal oxide particle, a metal sulfide, a metal selenide and a metal nitride, the metal oxide in the first doped metal oxide particle and the metal oxide in the first undoped metal oxide particle each independently include one or more of MoO3, WO3, NiO, CrO3, CuO, Cu2O, V2O5, the doping element in the first doped metal oxide particle includes one or more of Mo, W, Ni, Cr, Cu, V, the metal sulfide includes one or more of CuS, MoS3, WS3, the metal selenide includes one or more of MoSe3 and WSe3, and the metal nitride includes P-type gallium nitride;The P-type organic semiconductor materials include 4,4'-N,N'-dicarbazolyl-biphenyl, N,N'-diphenyl-N,N'-bis(1-naphthyl)-1,1'-biphenyl-4,4"-diamine, N,N'-diphenyl-N,N'-bis(3-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine, N,N'-bis(3-methylphenyl)-N,N'-bis(phenyl)-spiro, N,N'-bis(4-(N,N'-diphenyl-amino)phenyl)-N,N'-diphenylbenzidine, 4,4'-diamine. ,4'-tris(N-carbazolyl)-triphenylamine, 4,4',4'-tris(carbazol-9-yl)triphenylamine, trichloroisocyanuric acid, terbium-doped phosphate-based green luminescent materials, 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene, 4,4',4'-tris(N-3-methylphenyl-N-phenylamino)triphenylamine, poly[(9,9'-dioctylfluorene-2,7-diyl)-co-(4,4'-(N-(4-sec-butylphenyl)diphenylamine))], poly(4-butyl) phenyl-diphenylamine), poly[bis(4-phenyl)(4-butylphenyl)amine], polyaniline, polypyrrole, poly(p-phenylenevinylene), poly(phenylenevinylene), poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene], poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylenevinylene], copper phthalocyanine, aromatic tertiary amine, polynuclear aromatic tertiary amine, 4,4'-bis(p-carbazolyl)-1,1'-biphenyl compound, N,N,N',N'- One or more of tetraarylbenzidine, PEDOT, PEDOT:PSS and derivatives thereof, derivatives of PEDOT:PSS doped with s-MoO3, poly(N-vinylcarbazole) and derivatives thereof, polymethacrylate and derivatives thereof, poly(9,9-octylfluorene) and derivatives thereof, poly(spirofluorene) and derivatives thereof, N,N'-di(naphthalene-1-yl)-N,N'-diphenylbenzidine, spiro NPB, nano-polycrystalline diamond, microcrystalline cellulose and tetracyanoquinodimethane, doped graphene, and undoped graphene; and / or; The N-type semiconductor includes an N-type inorganic semiconductor material, the N-type inorganic semiconductor material includes second doped metal oxide particles, the metal oxide in the second doped metal oxide particles includes zinc oxide, and the doping element in the second doped metal oxide particles includes cadmium.

5. The light emitting device according to claim 4, wherein The doping molar ratio of the doping element in the metal oxide is 10% to 35%; and / or The average particle size of the second doped metal oxide particles is 5 nm to 20 nm.

6. The light emitting device according to claim 1, wherein The light emitting device further comprises an electronic functional layer, which is arranged between the light emitting layer and the cathode. The electronic functional layer comprises one or more of an electron injection layer and an electron transport layer.

7. The light emitting device according to claim 6, wherein The anode and the cathode respectively include a metal oxide electrode or a composite electrode in which a metal is arranged between doped or undoped transparent metal oxides, wherein the material of the metal oxide electrode includes one or more of ITO, FTO, ATO, AZO, GZO, IZO, MZO and AMO, and the composite electrode includes one or more of AZO / Ag / AZO, AZO / Al / AZO, ITO / Ag / ITO, ITO / Al / ITO, ZnO / Ag / ZnO, ZnO / Al / ZnO, ZnS / Ag / ZnS, ZnS / Al / ZnS, TiO2 / Ag / TiO2 and TiO2 / Al / TiO2; and / or The material of the light-emitting layer includes one or more of an organic light-emitting material and a quantum dot; the organic light-emitting material includes 4,4'-bis(N-carbazole)-1,1'-biphenyl: tris[2-(p-tolyl)pyridine iridium(III)], 4,4',4"-tris(carbazole-9-yl)triphenylamine: tris[2-(p-tolyl)pyridine iridium], diaromatic anthracene derivatives, distyrene aromatic derivatives, pyrene derivatives, fluorene derivatives, TBPe fluorescent materials, TTPX fluorescent materials, TBRb fluorescent materials, DBP fluorescent materials, delayed fluorescent materials, TTA materials, One or more of TADF materials, polymers containing BN covalent bonding, HLCT materials, and Exciplex luminescent materials; the quantum dots include one or more of single-structure quantum dots, core-shell structure quantum dots, and perovskite-type semiconductor materials, and the materials of the single-structure quantum dots, the core materials of the core-shell structure quantum dots, and the shell materials of the core-shell structure quantum dots are independently selected from one or more of II-VI group compounds, IV-VI group compounds, III-V group compounds, and I-III-VI group compounds; the shell of the core-shell structure quantum dots includes one or more layer or layers, the II-VI group compound includes CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, HgS, HgSe, HgTe, CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, CdZnSeS, CdZnSeTe, Cd One or more of dZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe and HgZnSTe; the IV-VI group compound includes one or more of SnS, SnSe, SnTe, PbS, PbSe, PbTe, SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, SnPbSSe, SnPbSeTe and SnPbSTe;The III-V compounds include GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, GaNP, GaNAs, GaNSb, GaPAs, GaPSb, and AlN P, AlNAs, AlNSb, AlPAs, AlPSb, InNP, InNAs, InNSb, InPAs, InPSb, GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInN P, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs and InAlPSb; the I-III-VI group compound includes one or more of CuInS2, CuInSe2 and AgInS2; the perovskite semiconductor material includes doped or undoped inorganic perovskite semiconductors, organic-inorganic hybrid perovskite semiconductors; the inorganic perovskite semiconductor has a general structural formula of AMX3, wherein A is Cs; + ion, M is a divalent metal cation selected from Pb 2+ 、Sn 2+ 、Cu 2+ 、Ni 2+ 、Cd 2+ Cr 2+ 、Mn 2+ 、Co 2+ 、Fe 2+ 、Ge 2+ 、Yb 2+ 、Eu 2+ One or more of, X is a halogen anion selected from Cl - Br - , I - One or more of the following; the general structural formula of the organic-inorganic hybrid perovskite semiconductor is BMX3, wherein B is an organic amine cation selected from CH3(CH2) n-2 NH3 + or [NH3(CH2) n NH3] 2+ , where n≥2, M is a divalent metal cation selected from Pb 2+ 、Sn 2+ 、Cu 2+ 、Ni 2+ 、Cd 2+ Cr 2+ 、Mn 2+ 、Co 2+ 、Fe 2+ 、Ge 2+ 、Yb 2+ 、Eu 2+ One or more of, X is a halogen anion selected from Cl - Br - , I - One or more of; and / or The materials of the electron injection layer and the electron transport layer respectively include one or more of the third doped metal oxide particles, the third undoped metal oxide particles, IIB-VIA semiconductor materials, IIIA-VA semiconductor materials and IB-IIIA-VIA semiconductor materials. The material of the third undoped metal oxide particles includes one or more of ZnO, TiO2, SnO2, ZrO2 and Ta2O5. The metal oxide in the third doped metal oxide particles includes ZnO, TiO2, SnO2, ZrO2 and Ta2O5.

2. One or more of Ta2O5, Al2O3, the doping elements in the third doped metal oxide particles include one or more of Al, Mg, Li, Mn, Y, La, Cu, Ni, Zr, Ce, In, and Ga, the IIB-VIA group semiconductor materials include one or more of ZnS, ZnSe, and CdS, the IIIA-VA group semiconductor materials include one or more of InP and GaP, and the IB-IIIA-VIA group semiconductor materials include one or more of CuInS and CuGaS.

8. A method for preparing a light-emitting device, characterized in that: include: Providing a light-emitting device preform, wherein the light-emitting device preform comprises an anode and a hole functional layer; Providing a transition material, and disposing the transition material on a side of the hole functional layer away from the anode to form a transition layer, wherein the absolute value of the valence band energy level of the hole functional layer is smaller than the absolute value of the valence band energy level of the transition layer; forming a light-emitting layer and a cathode on the transition layer, wherein the absolute value of the valence band energy level of the transition layer is smaller than the absolute value of the valence band energy level of the light-emitting layer, to obtain a light-emitting device; or, Providing a light-emitting device preform, wherein the light-emitting device preform includes a cathode and a light-emitting layer; Providing a transition material, and disposing the transition material on a side of the light-emitting layer away from the cathode to form a transition layer, wherein the absolute value of the valence band energy level of the transition layer is smaller than the absolute value of the valence band energy level of the light-emitting layer; A hole functional layer and an anode are formed on the transition layer, wherein the absolute value of the valence band energy level of the hole functional layer is smaller than the absolute value of the valence band energy level of the transition layer, thereby obtaining a light-emitting device.

9. The preparation method according to claim 8, wherein The absolute value of the difference between the valence band energy level of the transition layer and the valence band energy level of the hole functional layer is greater than 0 eV and less than 1.3 eV; and / or The absolute value of the difference between the valence band energy level of the light-emitting layer and the valence band energy level of the transition layer is greater than 0 eV and less than 1.3 eV; and / or The material of the hole functional layer includes a P-type semiconductor; and / or The transition material includes an N-type semiconductor.

10. The preparation method according to claim 9, characterized in that The N-type semiconductor includes an N-type inorganic semiconductor material, the N-type inorganic semiconductor material includes second doped metal oxide particles, the metal oxide in the second doped metal oxide particles includes zinc oxide, the doping element in the second doped metal oxide particles includes cadmium, and / or the doping molar ratio of the doping element in the metal oxide is 10% to 35%, and / or the average particle size of the second doped metal oxide particles is 5 nm to 20 nm.

11. The preparation method according to claim 8, characterized in that The preparation method of the transition material comprises: Providing a precursor solution, wherein the precursor solution includes a metal salt and a first solvent, wherein the metal salt includes a main metal salt and a doping metal salt; An alkaline solution is provided, wherein the alkaline solution includes an alkali and a second solvent, and the precursor solution and the alkaline solution are mixed to obtain a transition material.

12. The preparation method according to claim 11, characterized in that The main metal salt comprises a zinc salt; and / or The doping metal salt comprises a cadmium salt; and / or The base includes one or more of potassium hydroxide, lithium hydroxide, sodium hydroxide, ammonium hydroxide, ethylenediamine, ethanolamine, diethanolamine, triethanolamine, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide; and / or The first solvent and the second solvent respectively include one or more of methanol, ethanol, propanol, butanol, ethylene glycol, isopropanol, glycerol, dimethylformamide, dimethyl sulfoxide, cyclopentane, ethyl nitrate, xylene, anisole, decalin, cyclohexane, cyclohexene, methylcyclohexane, ethylcyclohexane, limonene, hexane, octane, nonane, decane, dimethylacetamide, acetyl carbonate, N-methylpyrrolidone, tetrahydrofuran, ethyl acetate, and dichloromethane.

13. The preparation method according to claim 11, wherein In the precursor solution, the molar concentration of the metal salt is 0.2 mol / L to 1 mol / L; and / or The molar ratio of the main metal salt to the doping metal salt is 1:(0.01-0.05); and / or The molar ratio of the base to the metal salt is (2-8):1; and / or The temperature of the precursor solution and the alkali solution after mixing is 50° C. to 70° C., and the mixing time is 2 hours to 4 hours.

14. The preparation method according to claim 8, wherein After forming the light-emitting layer on the transition layer, the step of forming an electronic functional layer and a cathode to obtain a light-emitting device is also included; or The light emitting device preform further includes an electronic functional layer, which is disposed between the cathode and the light emitting layer.

15. A display device, characterized in that: The invention comprises a light-emitting device according to any one of claims 1 to 7, or a light-emitting device prepared by the preparation method according to any one of claims 8 to 14.

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