Electroluminescent device and method for manufacturing the same, display device

Abstract

The application provides an electroluminescent device and a preparation method thereof and a display device, and relates to the technical field of display. The electroluminescent device comprises a first electrode and a second electrode arranged oppositely, at least two light-emitting units arranged in sequence and stacked between the first electrode and the second electrode, and at least one charge generation layer arranged between two adjacent light-emitting units respectively. The material of the charge generation layer comprises a first metal oxide, a second metal oxide and a third metal oxide. The conduction band energy level of the first metal oxide is between the conduction band energy level of the second metal oxide and -4.5 eV, and the valence band energy level of the third metal oxide is between the conduction band energy level of the first metal oxide and -5.5 eV. The electroluminescent device provided by the application has high charge generation efficiency of the charge generation layer and good device performance.

Description

Technical Field

[0001] This invention relates to the field of display technology, specifically to electroluminescent devices, their fabrication methods, and display devices. Background Technology

[0002] Stacked structures that connect light-emitting units, including the light-emitting layer, in series using a charge generation layer (CGL) offer advantages such as high current efficiency and long operating life, and are therefore widely used in the display technology field. However, the low charge generation efficiency of the charge generation layer in existing stacked devices significantly limits the development of stacked technology. Summary of the Invention

[0003] The purpose of this invention is to provide an electroluminescent device in which the charge generation layer has high charge generation efficiency and excellent device performance.

[0004] Another object of the present invention is to provide a method for fabricating an electroluminescent device.

[0005] Another object of the present invention is to provide a display device.

[0006] The technical problem solved by this invention is achieved by the following technical solution:

[0007] Electroluminescent devices, including:

[0008] The first and second electrodes are positioned relative to each other;

[0009] At least two light-emitting units, wherein the at least two light-emitting units are sequentially stacked between the first electrode and the second electrode; and

[0010] At least one charge generation layer is provided, and each charge generation layer is disposed between two adjacent light-emitting units. The material of the charge generation layer includes a first metal oxide, a second metal oxide, and a third metal oxide. The conduction band energy level of the first metal oxide is between the conduction band energy level of the second metal oxide and -4.5 eV, and the valence band energy level of the third metal oxide is between the conduction band energy level of the first metal oxide and -5.5 eV.

[0011] Optionally, in some embodiments of the present invention, -5.0 eV ≤ the conduction band energy level of the first metal oxide ≤ -4.5 eV; and / or

[0012] -5.0 eV ≤ conduction band level of the second metal oxide < -4.5 eV; and / or

[0013] -5.5eV ≤ valence band level of the third metal oxide ≤ -4.5eV; and / or

[0014] The first metal oxide is an n-type semiconductor; and / or

[0015] The third metal oxide is a p-type semiconductor.

[0016] Optionally, in some embodiments of the present invention, the first metal oxide is selected from ZnO, Zn x1 Mg y1 O, Zn x1 Al y1 O, Zn x2 Mg y2 Li z2 O, SnO2, Zn x1 Sn y1 One or more of O, wherein x1+y1=1 or x2+y2+z2=1; and / or

[0017] The second metal oxide is selected from one or more of MnO3 and WO3; and / or

[0018] The third metal oxide is selected from one or more of NiO, SnO, and CuO.

[0019] Optionally, in some embodiments of the present invention, the first metal oxide accounts for 10 to 40 wt% of the material of the charge generation layer; and / or

[0020] The second metal oxide accounts for 30–50 wt% of the material in the charge generation layer; and / or

[0021] The proportion of the third metal oxide in the charge generation layer material is 30-50 wt%.

[0022] Optionally, in some embodiments of the present invention, the thickness of the charge generation layer is 5–30 nm; and / or

[0023] The average particle sizes of the first metal oxide, the second metal oxide, and the third metal oxide are 3–15 nm, respectively.

[0024] Optionally, in some embodiments of the present invention, each light-emitting unit independently includes: a light-emitting layer; the material of the light-emitting layer is selected from one or more of the following: single-structure quantum dots, core-shell structure quantum dots, doped or undoped inorganic perovskite quantum dots, and organic-inorganic hybrid perovskite quantum dots; wherein, the single-structure quantum dots are selected from one or more of the following: group II-VI compounds, group III-V compounds, group II-V compounds, group III-VI compounds, group IV-VI compounds, group I-III-VI compounds, group II-IV-VI compounds, and group IV elements; the group II-VI compounds are selected from CdSe, CdS, CdTe, ZnSe, ZnS, CdTe, ZnTe, CdZnS, CdZnSe, CdZnTe, ZnSeS, ZnSeTe, ZnTeS, CdSeS, CdSeTe, CdTeS, CdZnSeS, CdZnSeTe, Cd... One or more of ZnSTe; III-V group compounds selected from InP, InAs, GaP, GaAs, GaN, GaSb, AlN, AlP, InAsP, InNP, InNSb, GaAlNP, InAlNP; IV-VI group compounds selected from PbS, PbSe; I-III-VI group compounds selected from CuInS2, CuInSe2, AgInS2; group IV elements selected from silicon, germanium; the core of the core-shell quantum dot is selected from any single-structure quantum dot; the shell material of the core-shell quantum dot is selected from CdS, CdTe, CdSe, CdSeTe, CdZnSe, CdZnS, CdSeS, ZnSe, ZnTe, ZnSeS, ZnS; the general structural formula of inorganic perovskite quantum dots is AMX3, where A is Cs. + M is 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 them, X is selected from Cl - ,Br - I - One or more of the following; the general structural formula of organic-inorganic hybrid perovskite quantum dots is BMX3, where B is selected from CH3(CH2). n-2 NH 3+ NH3(CH2) n NH32+ One or more of the following, where n≥2, and M is 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 them, X is selected from Cl - ,Br - I - One or more of them.

[0025] Optionally, in some embodiments of the present invention, each light-emitting unit further includes independently:

[0026] A first charge functional layer is disposed on the side of the light-emitting layer near the first electrode; and

[0027] The second charge functional layer is disposed on the side of the light-emitting layer near the second electrode;

[0028] The first charge functional layer and the second charge functional layer each independently include a charge injection layer and / or a charge transport layer, and each charge generation layer is disposed between the second charge functional layer of one light-emitting unit and the first charge functional layer of another light-emitting unit.

[0029] Optionally, in some embodiments of the present invention, the materials of the first electrode and the second electrode are independently selected from one or more of doped or undoped metals, silicon carbon materials, doped or undoped metal oxides, and composite electrode materials; wherein, the doped or undoped metals are selected from one or more of Al, Ag, Cu, Mo, Au, Ba, Ca, Mg, Ni, Pt, Ir, Ca:Al, LiF:Ca, LiF:Al, BaF2:Al, CsF:Al, CaCO3:Al, BaF2:Ca:Al, Au:Mg, and Ag:Mg; the silicon carbon materials are selected from silicon, graphite, carbon nanotubes, graphene, and carbon fibers. One or more; the doped or undoped metal oxide is selected from one or more of ITO, FTO, ATO, AZO, GZO, IZO, MZO, AMO, ITZO, ICO, SnO2, In2O3, Cd:ZnO, Ga:SnO2; the composite electrode material is selected from one or more of AZO / Ag / AZO, AZO / Al / AZO, ITO / Ag / ITO, ITO / Al / ITO, ZnO / Ag / ZnO, ZnO / Al / ZnO, TiO2 / Ag / TiO2, TiO2 / Al / TiO2, ZnS / Ag / ZnS, ZnS / Al / ZnS; and / or

[0030] The charge injection layer material is selected from Ca, Ba, CsF, CsCO3, PEIE, PEI, LiF, NaF, poly(ethylene dioxythiophene): polystyrene sulfonate, poly[9,9-dioctyl-fluorene-co-N-(4-butylphenyl)-diphenylamine], polyarylamines, poly(N-vinylcarbazole), polyaniline, polythiophene, polypyrrole, N,N,N',N'-tetra(4-methoxyphenyl)-benzidine, 4-bis[N-(1-naphthyl)-N-phenyl-amino]biphenyl, 4,4',4”- One or more of the following: tris[phenyl(m-tolyl)amino]triphenylamine, 4,4',4”-tris(N-carbazolyl)triphenylamine, 1,1-bis[(di-4-tolylamino)phenylcyclohexane, tetrafluoro-tetracyanoquinone dimethane-doped 4,4',4”-tris(diphenylamino)triphenylamine, p-doped phthalocyanine, F4-TCNQ-doped N,N′-diphenyl-N,N′-di(1-naphthyl)-1,1′-biphenyl-4,4″-diamine, hexaazabenzophenanthrene-hexanonitrile, and metal oxides; and / or

[0031] The charge transport layer material is selected from doped or undoped oxides, doped or undoped semiconductor particles, nitrides, Alq3, Almq3, DVPBi, TAZ, OXD, PBD, BND, PV, CBP, α-NPD, TPD, spiro-TPD, DNTPD, TCTA, m-MTDATA, TAPC, TFB, poly-TPD, polyaniline, polyfluorene, polypyrrole, PPV, MEH-PPV, MOMO-PPV, copper phthalocyanine, aromatic tertiary amines, polynuclear aromatic tertiary amines, 4,4'-bis(p-carbazolyl)-1,1'-biphenyl compounds, N,N,N',N'-tetraarylbenzidine, PEDOT:PSS and its derivatives, PVK and its derivatives, polymethacrylates and their derivatives, and poly (9,9-Octylfluorene) and its derivatives, poly(spirofluorene) and its derivatives, NPB, spiroNPB, HATCN; wherein the oxide is selected from one or more of TiO2, ZnO, ZrO2, SnO2, WO3, NiO, Ta2O3, HfO2, Al2O3, ZrSiO4, BaTiO3, BaZrO3, SrTiO3, MgTiO3, TiLiO, ZnAlO, ZnSnO, ZnLiO, InSnO, the semiconductor particle is selected from one or more of CdS, ZnSe, ZnS, the nitride is selected from Si3N4, and the doping element of the oxide and semiconductor particle is selected from one or more of Al, Mg, In, Li, Ga, Cd, Cs, Cu.

[0032] In addition, methods for fabricating electroluminescent devices include:

[0033] Provide the first electrode;

[0034] At least two light-emitting units and at least one charge-generating layer are formed on a first electrode; wherein each charge-generating layer is disposed between two adjacent light-emitting units, and the material of the charge-generating layer includes a first metal oxide, a second metal oxide, and a third metal oxide, wherein the conduction band energy level of the first metal oxide is between the conduction band energy level of the second metal oxide and -4.5 eV, and the valence band energy level of the third metal oxide is between the conduction band energy level of the first metal oxide and -5.5 eV; and

[0035] A second electrode is formed on the light-emitting unit.

[0036] In addition, the display device includes the electroluminescent device described above, or the electroluminescent device prepared by the preparation method described above.

[0037] Compared with the prior art, the present invention has the following beneficial effects: In the present invention, the material of the charge generation layer of the device includes a first metal oxide, a second metal oxide and a third metal oxide. Based on the appropriate matching of the conduction band / valence band energy levels of the three metal oxides, the formed charge generation layer can have a higher charge generation efficiency, and the device including the charge generation layer has a low turn-on voltage and high current efficiency. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a schematic diagram of the structure of the quantum dot light-emitting diode provided in Embodiment 1 of the present invention.

[0040] The reference numerals in the attached figures are summarized as follows:

[0041] First electrode 101; first hole injection layer 102; first hole transport layer 103; first light-emitting layer 104; first electron transport layer 105;

[0042] Charge generation layer 201;

[0043] Second hole transport layer 301; second light-emitting layer 302; second electron transport layer 303; second electrode 304. Detailed Implementation

[0044] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] The technical solutions provided by this invention will be described in detail below. It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of the embodiments. Furthermore, in the description of this invention, the term "comprising" means "including but not limited to". The terms "first", "second", "third", etc., are used merely as illustrative and do not impose numerical requirements or establish an order. Various embodiments of this invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of this invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range.

[0046] This invention provides an electroluminescent device, comprising:

[0047] The first and second electrodes are positioned relative to each other;

[0048] At least two light-emitting units, wherein the at least two light-emitting units are sequentially stacked between the first electrode and the second electrode; and

[0049] At least one charge generation layer is provided, and each charge generation layer is disposed between two adjacent light-emitting units. The material of the charge generation layer includes a first metal oxide, a second metal oxide, and a third metal oxide. The conduction band energy level of the first metal oxide is between the conduction band energy level of the second metal oxide and -4.5 eV, and the valence band energy level of the third metal oxide is between the conduction band energy level of the first metal oxide and -5.5 eV.

[0050] It should be noted that "between" includes cases where the values ​​are equal to the boundary values. Furthermore, -5.0eV ≤ conduction band level of the first metal oxide ≤ -4.5eV; -5.0eV ≤ conduction band level of the second metal oxide < -4.5eV; -5.5eV ≤ valence band level of the third metal oxide ≤ -4.5eV.

[0051] At least two light-emitting units are stacked units connected in series, and the at least two light-emitting units are connected by a charge-generating layer. The light-emitting units and the charge-generating layer can be stacked. The average particle size of the first metal oxide, the second metal oxide, and the third metal oxide can all be in the nanometer range.

[0052] The second metal oxide has a deep conduction band energy level, and the third metal oxide has a shallow valence band energy level. The charge generation layer includes multiple metal oxides based on energy level matching, resulting in a charge generation layer with higher charge generation efficiency.

[0053] In some embodiments, the first metal oxide may be selected as a metal oxide with electron transport capability; further, the first metal oxide is an n-type semiconductor. The first metal oxide with electron transport capability is capable of rapid electron transport.

[0054] In some embodiments, the third metal oxide is a p-type semiconductor.

[0055] Furthermore, the first metal oxide is selected from ZnO, Zn x1 Mg y1 O, Zn x1 Al y1 O, Zn x2 Mg y2 Li z2 O, SnO2, Zn x1Sn y1 One or more of O, wherein x1+y1=1 or x2+y2+z2=1; the second metal oxide is selected from one or more of MnO3 and WO3; the third metal oxide is selected from one or more of NiO, SnO and CuO.

[0056] In some embodiments, the first metal oxide accounts for 10-40 wt% of the material of the charge generation layer, for example, 10-20%, 15-30%, or 30-40%; the second metal oxide accounts for 30-50 wt% of the material of the charge generation layer, for example, 30-35%, 35-45%, or 42-50%; and the third metal oxide accounts for 30-50 wt% of the material of the charge generation layer, for example, 30-35%, 35-45%, or 42-50%.

[0057] In some embodiments, the thickness of the charge generation layer is 5–30 nm, and may also be 10–15 nm, 15–25 nm, or 22–30 nm.

[0058] In some embodiments, the average particle sizes of the first metal oxide, the second metal oxide, and the third metal oxide are 3–15 nm, and may also be 5–9 nm and 10–15 nm, respectively.

[0059] The electroluminescent devices provided by this invention are not limited to two-layer devices, three-layer devices, multi-layer devices, top-emitter devices, bottom-emitter devices, double-sided emitting devices, rigid devices, flexible devices, upright structure devices, inverted structure devices, etc. The electroluminescent devices can be one of quantum dot light-emitting diodes (QLEDs), organic light-emitting diodes (OLEDs), sub-millimeter light-emitting diodes (Mini LEDs), and micron light-emitting diodes (Micro LEDs).

[0060] In some embodiments, each light-emitting unit independently includes a light-emitting layer. When the electroluminescent device is a quantum dot light-emitting diode, the light-emitting layer can be a quantum dot light-emitting layer. The material of the quantum dot light-emitting layer can be one or more of red quantum dots, green quantum dots, and blue quantum dots. The photoluminescence wavelengths (PL) of the red, green, and blue quantum dot materials are 615–635 nm, 535–555 nm, and 465–480 nm, respectively. Furthermore, the material of the light-emitting layer can be selected from one or more of the following: single-structure quantum dots, core-shell structure quantum dots, doped or undoped inorganic perovskite quantum dots, and organic-inorganic hybrid perovskite quantum dots; wherein, the single-structure quantum dots are selected from one or more of the following: group II-VI compounds, group III-V compounds, group II-V compounds, group III-VI compounds, group IV-VI compounds, group I-III-VI compounds, group II-IV-VI compounds, and group IV elements; the group II-VI compounds are selected from one or more of the following: CdSe, CdS, CdTe, ZnSe, ZnS, ZnTe, CdZnS, CdZnSe, CdZnTe, ZnSeS, ZnSeTe, ZnTeS, CdSeS, CdSeTe, CdTeS, CdZnSeS, CdZnSeTe, and CdZnSTe. Group I-V compounds are selected from one or more of InP, InAs, GaP, GaAs, GaN, GaSb, AlN, AlP, InAsP, InNP, InNSb, GaAlNP, and InAlNP; Group IV-VI compounds are selected from one or more of PbS and PbSe; Group I-III-VI compounds are selected from one or more of CuInS2, CuInSe2, and AgInS2; Group IV elements are selected from one or more of silicon and germanium; the core of the core-shell quantum dot is selected from any single-structure quantum dot; the shell material of the core-shell quantum dot is selected from one or more of CdS, CdTe, CdSe, CdSeTe, CdZnSe, CdZnS, CdSeS, ZnSe, ZnTe, ZnSeS, and ZnS; the general structural formula of inorganic perovskite quantum dots is AMX3, where A is Cs. + M is 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 them, X is selected from Cl- ,Br - I - One or more of the following; the general structural formula of organic-inorganic hybrid perovskite quantum dots is BMX3, where B is selected from CH3(CH2). n-2 NH 3+ NH3(CH2) n NH3 2+ One or more of the following, where n≥2, and M is 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 them, X is selected from Cl - ,Br - I - One or more of the following. The light-emitting layer can have a thickness of 10–50 nm.

[0061] In some embodiments, each light-emitting unit independently further includes:

[0062] A first charge functional layer is disposed on the side of the light-emitting layer near the first electrode; and

[0063] The second charge functional layer is disposed on the side of the light-emitting layer near the second electrode;

[0064] The first charge functional layer and the second charge functional layer each independently include a charge injection layer and / or a charge transport layer, and each charge generation layer is disposed between the second charge functional layer of one light-emitting unit and the first charge functional layer of another light-emitting unit.

[0065] In some embodiments, the first electrode is an anode, then the first charge functional layer is a hole functional layer, the second charge functional layer is an electron functional layer, and the second electrode is a cathode. In other embodiments, the first electrode may also be a cathode, then the first charge functional layer is an electron functional layer, the second charge functional layer is a hole functional layer, and the second electrode is an anode.

[0066] Furthermore, since the first charge functional layer and the second charge functional layer each independently include a charge injection layer and / or a charge transport layer, for example, if the first charge functional layer is a hole functional layer, then the first charge functional layer may include a hole injection layer and / or a hole transport layer; if the second charge functional layer is an electron functional layer, then the second charge functional layer may include an electron injection layer and / or an electron transport layer.

[0067] In some embodiments, the materials of the first electrode and the second electrode are independently selected from one or more of doped or undoped metals, silicon carbon materials, doped or undoped metal oxides, and composite electrode materials; wherein, the doped or undoped metals are selected from one or more of Al, Ag, Cu, Mo, Au, Ba, Ca, Mg, Ni, Pt, Ir, Ca:Al, LiF:Ca, LiF:Al, BaF2:Al, CsF:Al, CaCO3:Al, BaF2:Ca:Al, Au:Mg, and Ag:Mg; and the silicon carbon materials are selected from one of silicon, graphite, carbon nanotubes, graphene, and carbon fibers. One or more; the doped or undoped metal oxides are selected from one or more of ITO, FTO, ATO, AZO, GZO, IZO, MZO, AMO, ITZO, ICO, SnO2, In2O3, Cd:ZnO, and Ga:SnO2; the composite electrode material is selected from one or more of AZO / Ag / AZO, AZO / Al / AZO, ITO / Ag / ITO, ITO / Al / ITO, ZnO / Ag / ZnO, ZnO / Al / ZnO, TiO2 / Ag / TiO2, TiO2 / Al / TiO2, ZnS / Ag / ZnS, and ZnS / Al / ZnS.

[0068] Furthermore, when the first or second electrode is the anode, the anode material can be selected from one or more of doped or undoped metal oxides, silicon carbon materials, metals, and composite electrode materials; wherein, the doped or undoped metal oxide is selected from one or more of ITO, FTO, ATO, IZO, ITZO, ICO, SnO2, In2O3, Cd:ZnO, Ga:SnO2, AZO, GZO, MZO, and AMO; the silicon carbon material is selected from one or more of silicon, graphite, carbon nanotubes, graphene, and carbon fibers; the metal is selected from... The anode can be a composite electrode consisting of one or more of Al, Ag, Cu, Mo, Au, Ba, Ca, and Mg; the composite electrode material is selected from one or more of AZO / Ag / AZO, AZO / Al / AZO, ITO / Ag / ITO, ITO / Al / ITO, ZnO / Ag / ZnO, ZnO / Al / ZnO, TiO2 / Ag / TiO2, TiO2 / Al / TiO2, ZnS / Ag / ZnS, and ZnS / Al / ZnS, i.e., the anode can be a composite electrode consisting of a metal sandwiched between doped or undoped metal oxides.

[0069] When the first or second electrode is a cathode, the cathode material can be selected from one or more of doped or undoped metals, silicon carbon materials, doped or undoped metal oxides, and composite electrode materials; wherein, the doped or undoped metal is selected from one or more of Al, Ag, Cu, Mo, Au, Ba, Ca, Mg, Pt, Ca:Al, LiF:Ca, LiF:Al, BaF2:Al, CsF:Al, CaCO3:Al, BaF2:Ca:Al, Au:Mg, and Ag:Mg, and the doped metal electrode is an alloy electrode; the silicon carbon material is selected from silicon, graphite, carbon nanotubes, graphene, and carbon fibers. One or more; the doped or undoped metal oxide is selected from one or more of ITO, FTO, ATO, AZO, GZO, IZO, MZO, and AMO; the composite electrode material is selected from one or more of AZO / Ag / AZO, AZO / Al / AZO, ITO / Ag / ITO, ITO / Al / ITO, ZnO / Ag / ZnO, ZnO / Al / ZnO, TiO2 / Ag / TiO2, TiO2 / Al / TiO2, ZnS / Ag / ZnS, and ZnS / Al / ZnS, that is, the cathode can be, for example, a composite electrode of AZO / Ag / AZO or AZO / Al / AZO. The thickness of the cathode can be 80–500 nm.

[0070] The charge injection layer material is selected from Ca, Ba, CsF, CsCO3, PEIE, PEI, LiF, NaF, poly(ethylene dioxythiophene): polystyrene sulfonate, poly[9,9-dioctyl-fluorene-co-N-(4-butylphenyl)-diphenylamine], polyarylamines, poly(N-vinylcarbazole), polyaniline, polythiophene, polypyrrole, N,N,N',N'-tetra(4-methoxyphenyl)-benzidine, 4-bis[N-(1-naphthyl)-N-phenyl-amino]biphenyl, 4,4',4” One or more of the following: tri[phenyl(m-tolyl)amino]triphenylamine, 4,4',4”-tris(N-carbazolyl)triphenylamine, 1,1-bis[(di-4-tolylamino)phenylcyclohexane, tetrafluoro-tetracyanoquinone dimethane-doped 4,4',4”-tris(diphenylamino)triphenylamine, p-doped phthalocyanine, F4-TCNQ-doped N,N′-diphenyl-N,N′-di(1-naphthyl)-1,1′-biphenyl-4,4″-diamine, hexaazabenzophenanthrene-hexanonitrile, and metal oxides.

[0071] Furthermore, when the charge injection layer is a hole injection layer, the material of the hole injection layer can be selected from poly(ethylene dioxythiophene):polystyrene sulfonate (PEDOT:PSS), poly[9,9-dioctyl-fluorene-co-N-(4-butylphenyl)-diphenylamine] (TFB), polyarylamines, poly(N-vinylcarbazole) (PVK), polyaniline (Pan), polythiophene, polypyrrole (PPY), N,N,N',N'-tetra(4-methoxyphenyl)-benzidine (TPD), 4-bis[N-(1-naphthyl)-N-phenyl-amino]biphenyl (α-NPD), 4,4',4”-tris[phenyl(m-tolyl)amino]triphenylamine (m-MTDATA), 4,4',4” The hole injection layer can be selected from one or more of the following: α-tris(N-carbazolyl)-triphenylamine (TCTA), 1,1-bis[(di-4-tolylamino)phenylcyclohexane (TAPC), 4,4',4'-tris(diphenylamino)triphenylamine (TDATA) doped with tetrafluoro-tetracyanoquinone dimethylane (F4-TCNQ), p-doped phthalocyanine (e.g., F4-TCNQ-doped zinc phthalocyanine (ZnPc)), F4-TCNQ-doped N,N′-diphenyl-N,N′-di(1-naphthyl)-1,1′-biphenyl-4,4″-diamine (α-NPD), hexaazabenzophenanthrene-hexanonitrile (HAT-CN), and metal oxides; wherein the metal oxide can be selected from one or more of MnO3 and WO3. The thickness of the hole injection layer can be 10–50 nm.

[0072] The charge transport layer material is selected from doped or undoped oxides, doped or undoped semiconductor particles, nitrides, Alq3, Almq3, DVPBi, TAZ, OXD, PBD, BND, PV, CBP, α-NPD, TPD, spiro-TPD, DNTPD, TCTA, m-MTDATA, TAPC, TFB, poly-TPD, polyaniline, polyfluorene, polypyrrole, PPV, MEH-PPV, MOMO-PPV, copper phthalocyanine, aromatic tertiary amines, polynuclear aromatic tertiary amines, 4,4'-bis(p-carbazolyl)-1,1'-biphenyl compounds, N,N,N',N'-tetraarylbenzidine, PEDOT:PSS and its derivatives, PVK and its derivatives, polymethacrylates and their derivatives, and poly (9,9-Octylfluorene) and its derivatives, poly(spirofluorene) and its derivatives, NPB, spiroNPB, HATCN; wherein the oxide is selected from one or more of TiO2, ZnO, ZrO2, SnO2, WO3, NiO, Ta2O3, HfO2, Al2O3, ZrSiO4, BaTiO3, BaZrO3, SrTiO3, MgTiO3, TiLiO, ZnAlO, ZnSnO, ZnLiO, InSnO, the semiconductor particle is selected from one or more of CdS, ZnSe, ZnS, the nitride is selected from Si3N4, and the doping element of the oxide and semiconductor particle is selected from one or more of Al, Mg, In, Li, Ga, Cd, Cs, Cu.

[0073] Furthermore, when the charge transport layer is an electron transport layer, the material of the electron transport layer can be selected from one or more of inorganic materials and organic materials. Specifically, the inorganic material can be selected from one or more of doped or undoped oxides, doped or undoped semiconductor particles, and nitrides. Further, the oxide can be selected from, but is not limited to, TiO2, ZnO, ZrO2, SnO2, WO3, NiO, Ta2O3, HfO2, Al2O3, ZrSiO4, BaTiO3, BaZrO3, SrTiO3, MgTiO3, TiLiO, ZnAlO, ZnSnO, ZnLiO, and InSnO; the semiconductor particles can be selected from, but are not limited to, CdS, ZnSe, and ZnS; the nitride can be Si3N4; and the doping elements of the oxide and semiconductor particles can be selected from, but are not limited to, Al, Mg, In, Li, Ga, Cd, Cs, and Cu. The organic material of the electron transport layer can be selected from one or more of oxazole compounds, isoxazole compounds, triazole compounds, isothiazole compounds, oxadiazole compounds, thiadiazole compounds, perylene compounds, and aluminum complexes. Further, it can be selected from one or more of Alq3, Almq3, DVPBi, TAZ, OXD, PBD, BND, and PV. The thickness of the electron transport layer can be 20–60 nm.

[0074] When the charge transport layer is a hole transport layer, the material of the hole transport layer can be an arylamine, such as 4,4'-N,N'-dicarbazolyl-biphenyl (CBP), N,N'-diphenyl-N,N'-bis(1-naphthyl)-1,1'-biphenyl-4,4”-diamine (α-NPD), N,N'-diphenyl-N,N'-bis(3-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine (TPD), N,N'-bis(3-methylphenyl)-N,N'-bis(phenyl)-spiroamine (spiro-TPD), N,N'-bis(4-(N,N'-diphenyl-amino)phenyl)-N,N'-diphenylbenzidine (DNTPD), 4,4',4'-tris(N-carbazolyl)-triphenylamine (TCTA), tris(3-methylphenylphenylamino)-triphenylamine (m-MTDATA), TAPC, poly[(9,9'-dioctylfluorene-2,7-diyl)-co-(4,4'-(N-(4-sec-butylphenyl)diphenylamine))](TFB) and poly(4-butylphenyl-diphenyl) Amines (poly-TPD); polyaniline; polyfluorene; polypyrrole; poly(p-)phenylene vinylidene and its derivatives, such as poly(phenylene vinylidene) (PPV), poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene vinylidene] (MEH-PPV) and poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylene vinylidene] (MOMO-PPV); copper phthalocyanine; aromatic tertiary amines or polynuclear aromatic tertiary amines; 4,4'-bis(p-carbazolyl)-1, 1'-Biphenyl compounds; N,N,N',N'-tetraarylbenzidine; PEDOT:PSS and its derivatives; poly(N-vinylcarbazole) (PVK) and its derivatives; polymethacrylate and its derivatives; poly(9,9-octylfluorene) and its derivatives; poly(spirofluorene) and its derivatives; N,N'-di(naphthyl-1-yl)-N,N'-diphenylbenzidine (NPB); spiroNPB; HATCN; p-NiO; or combinations of the foregoing compounds. The thickness of the hole transport layer can be 15–40 nm.

[0075] For example, in some embodiments, the light-emitting unit may include a first light-emitting unit and a second light-emitting unit, and the electroluminescent device preferably includes an anode, a first light-emitting unit (a first hole injection layer, a first hole transport layer, a first light-emitting layer, and a first electron transport layer) stacked together, a charge generation layer, a second light-emitting unit (a second hole transport layer, a second light-emitting layer, and a second electron transport layer), and a cathode.

[0076] In this process, the first metal oxide in the charge generation layer material can possess electron transport capabilities to rapidly transport electrons to the first electron transport layer. The conduction band energy level of the first metal oxide can be lower than that of the first electron transport layer material.

[0077] The first hole transport layer is preferably a conductive polymer, such as polyaniline, polyfluorene, TFB, PVK, Poly-TPD, etc. The first electron transport layer is preferably an N-type metal oxide, such as ZnO, Zn x1 Mg y1 O, Zn x1 Al y1 O, Zn x2 Mg y2 Li z2 O, SnO2, Zn x1 Sn y1 O, where x1+y1=1 or x2+y2+z2=1. The second hole transport layer is preferably a p-type metal oxide such as p-NiO, or a p-type organic material such as HATCN. The second electron transport layer is preferably a metal oxide, such as ZnO, Zn x1 Mg y1 O, Zn x1 Al y1 O, Zn x2 Mg y2 Li z2 O etc.

[0078] In addition, the present invention also provides a method for fabricating the above-mentioned electroluminescent device, comprising:

[0079] Provide the first electrode;

[0080] At least two light-emitting units and at least one charge-generating layer are formed on a first electrode; wherein each charge-generating layer is disposed between two adjacent light-emitting units, and the material of the charge-generating layer includes a first metal oxide, a second metal oxide, and a third metal oxide, wherein the conduction band energy level of the first metal oxide is between the conduction band energy level of the second metal oxide and -4.5 eV, and the valence band energy level of the third metal oxide is between the conduction band energy level of the first metal oxide and -5.5 eV; and

[0081] A second electrode is formed on the light-emitting unit.

[0082] It should be noted that the term "on" in the preparation method, which refers to forming another structural layer / unit "on" a certain structural layer / unit, is a broad concept. It includes "on" that has a contact or adjacent relationship, as well as "above" that has a spacing relationship. It can mean that the formed other structural layer / unit is adjacent to a certain structural layer / unit, or it can mean that there is a spacer layer / unit between the other structural layer / unit and a certain structural layer / unit.

[0083] The deposition / fabrication of the various structural layers of an electroluminescent device can be achieved using techniques well-known in the art, including chemical or physical methods. Chemical methods include, for example, chemical vapor deposition, continuous ion layer adsorption and reaction, anodic oxidation, electrolytic deposition, and co-precipitation. Physical methods can be physical deposition or solution processing. Specifically, physical deposition methods include, for example, thermal evaporation deposition, electron beam evaporation deposition, magnetron sputtering, multi-arc ion deposition, physical vapor deposition, atomic layer deposition, and pulsed laser deposition; solution processing methods include, for example, spin coating, printing, inkjet printing, blade coating, dip coating, immersion coating, spray coating, roller coating, casting, slot coating, and strip coating. Specific processing methods and conditions can be found in common practices in the art and will not be elaborated further here.

[0084] In addition, the present invention also provides a display device, including the electroluminescent device described above, or including the electroluminescent device prepared by the above-described preparation method.

[0085] Example 1

[0086] This embodiment provides a quantum dot light-emitting diode and its fabrication method, including:

[0087] Step S1. A first hole injection layer 102 is prepared on the first electrode 101 made of ITO material, the material being PEDOT:PSS, and the thickness being 15nm;

[0088] Step S2. Prepare a first hole transport layer 103 on the first hole injection layer 102. The material is PVK and the thickness is 25nm.

[0089] Step S3. Prepare a first light-emitting layer 104 of red quantum dots on the first hole transport layer 103. The material of the first light-emitting layer 104 is CdZnSe / ZnSe / ZnS (emission wavelength is 630nm) and the thickness is 15nm.

[0090] Step S4. On the first light-emitting layer 104, a first electron transport layer 105 is prepared, the material being Zn. 0.95 Mg 0.05 O (conduction band energy level is -3.75eV), thickness is 40nm;

[0091] Step S5. A charge generation layer 201 is prepared on the first electron transport layer 105. The charge generation layer 201 is made of ZnO, MnO3 and NiO in a mass ratio of 1:2:2 and has a thickness of 15 nm.

[0092] Step S6. Prepare a second hole transport layer 301 on the charge generation layer 201. The material is NiO and the thickness is 25 nm.

[0093] Step S7. Prepare a second light-emitting layer 302 of red quantum dots on the second hole transport layer 301. The material of the second light-emitting layer 302 is CdZnSe / ZnSe / ZnS (emission wavelength is 630nm) and the thickness is 15nm.

[0094] Step S8. Prepare a second electron transport layer 303 on the second light-emitting layer 302, the material being Zn. 0.95 Mg 0.05 O, with a thickness of 40nm;

[0095] Step S9. The second electrode 304 is prepared by vacuum evaporation process. The material is silver and the thickness is 100 nm.

[0096] Example 2

[0097] The quantum dot light-emitting diode and its preparation method provided in this embodiment are basically the same as those in Embodiment 1, except that in step S5 of this embodiment, the material of the charge generation layer includes SnO2, MnO3 and CuO in a mass ratio of 2:5:3 and the thickness is 25nm.

[0098] Example 3

[0099] The quantum dot light-emitting diode and its fabrication method provided in this embodiment are basically the same as those in Embodiment 1, except that: in step S5 of this embodiment, the material of the charge generation layer includes Zn with a mass ratio of 1:4:5. 0.9 Mg 0.1 O, WO3, NiO, with a thickness of 20nm.

[0100] Comparative Example 1

[0101] The quantum dot light-emitting diode and its fabrication method provided in this comparative example include:

[0102] Step S1. Prepare a first hole injection layer on the first electrode made of ITO material, the material being PEDOT:PSS, with a thickness of 15nm;

[0103] Step S2. Prepare a first hole transport layer on the first hole injection layer. The material is PVK and the thickness is 25nm.

[0104] Step S3. Prepare a first emitting layer of red quantum dots on the first hole transport layer. The material of the first emitting layer is CdZnSe / ZnSe / ZnS (emission wavelength is 630nm) and the thickness is 15nm.

[0105] Step S4. On the first light-emitting layer, a first electron transport layer is prepared, the material being Zn. 0.95 Mg 0.05 O (conduction band energy level is -3.75eV), thickness is 40nm;

[0106] Step S5. Prepare a second hole injection layer on the first electron transport layer. The material is PEDOT:PSS and the thickness is 15nm.

[0107] Step S6. Prepare a second hole transport layer on the second hole injection layer. The material is PVK and the thickness is 25 nm.

[0108] Step S7. Prepare a second light-emitting layer of red quantum dots on the second hole transport layer. The material of the second light-emitting layer is CdZnSe / ZnSe / ZnS (emission wavelength is 630nm) and the thickness is 15nm.

[0109] Step S8. Prepare a second electron transport layer on the second light-emitting layer, the material being Zn. 0.95 Mg 0.05 O, with a thickness of 40nm;

[0110] Step S9. Prepare the second electrode using a vacuum evaporation process. The material is silver and the thickness is 100 nm.

[0111] In this comparative example, the charge generation layer of the device is composed of a first electron transport layer and a second hole injection layer.

[0112] Comparative Example 2

[0113] The quantum dot light-emitting diode and its fabrication method provided in this comparative example include:

[0114] Step S1. Prepare a first hole injection layer on the first electrode made of ITO material, the material being PEDOT:PSS, with a thickness of 15nm;

[0115] Step S2. Prepare a first hole transport layer on the first hole injection layer. The material is PVK and the thickness is 25nm.

[0116] Step S3. Prepare a first emitting layer of red quantum dots on the first hole transport layer. The material of the first emitting layer is CdZnSe / ZnSe / ZnS (emission wavelength is 630nm) and the thickness is 15nm.

[0117] Step S4. On the first light-emitting layer, prepare the first-1 electron transport layer, the material of which is Zn. 0.95 Mg 0.05 O (conduction band energy level is -3.75eV), with a thickness of 25nm; the first-second electron transport layer is prepared on the first-first electron transport layer, with its conduction band energy level lower than that of the first-first electron transport layer. The material of the first-second electron transport layer is ZnO, with a thickness of 15nm.

[0118] Step S5. Prepare a second hole injection layer on the first-second electron transport layer. The material is MoO3 and the thickness is 10 nm.

[0119] Step S6. Prepare a second hole transport layer on the second hole injection layer. The material is NiO and the thickness is 25 nm.

[0120] Step S7. Prepare a second light-emitting layer of red quantum dots on the second hole transport layer. The material of the second light-emitting layer is CdZnSe / ZnSe / ZnS (emission wavelength is 630nm) and the thickness is 15nm.

[0121] Step S8. Prepare a second electron transport layer on the second light-emitting layer, the material being Zn. 0.95 Mg 0.05 O, with a thickness of 40nm;

[0122] Step S9. Prepare the second electrode using a vacuum evaporation process. The material is silver and the thickness is 100 nm.

[0123] In this comparative example, the charge generation layer of the device is composed of a second hole injection layer and a second hole transport layer.

[0124] The devices provided in Examples 1-3 and Comparative Examples 1-2 were tested, and the test results are shown in Table 1:

[0125] Table 1

[0126]

[0127]

[0128] As shown in Table 1, due to the large energy difference between the conduction band level of the first electron transport layer and the HOMO level of the second hole injection layer in the device provided by Comparative Example 1, the device has a high turn-on voltage and low current efficiency. Although the device provided by Comparative Example 2 is slightly better, it is still at a poor level. The electroluminescent device provided by the present invention has a lower turn-on voltage and higher current efficiency, and the device has excellent performance.

[0129] The technical solutions provided by the embodiments of the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. An electroluminescent device, characterized in that, include: The first and second electrodes are positioned relative to each other; At least two light-emitting units are arranged in a stacked manner between the first electrode and the second electrode; as well as At least one charge generation layer is provided, each charge generation layer being disposed between two adjacent light-emitting units. The material of the charge generation layer includes a first metal oxide, a second metal oxide, and a third metal oxide. The conduction band energy level of the first metal oxide is between the conduction band energy level of the second metal oxide and -4.5 eV, and the valence band energy level of the third metal oxide is between the conduction band energy level of the first metal oxide and -5.5 eV. -5.0eV≤conduction band energy level of the first metal oxide≤-4.5eV; -5.0eV ≤ the conduction band energy level of the second metal oxide < -4.5eV; -5.5eV ≤ Valence band level of the third metal oxide ≤ -4.5eV; The first metal oxide is an n-type semiconductor; The third metal oxide is a p-type semiconductor.

2. The electroluminescent device according to claim 1, characterized in that, The first metal oxide is selected from ZnO and Zn x1 Mg y1 O, Zn x1 Al y1 O, Zn x2 Mg y2 Li z2 O, SnO2, Zn x1 Sn y1 One or more of O, where x1+y1=1 or x2+y2+z2=1; and / or The second metal oxide is selected from one or more of MnO3 and WO3; and / or The third metal oxide is selected from one or more of NiO, SnO, and CuO.

3. The electroluminescent device according to claim 1, characterized in that, The first metal oxide accounts for 10-40 wt% of the material of the charge generation layer; and / or The second metal oxide accounts for 30-50 wt% of the material of the charge-generating layer; and / or The third metal oxide accounts for 30-50 wt% of the material of the charge generation layer.

4. The electroluminescent device according to claim 3, characterized in that, The first metal oxide accounts for 10-20 wt% of the material of the charge generation layer; and / or The second metal oxide comprises 35-45 wt% of the material of the charge-generating layer; and / or The third metal oxide accounts for 35-45 wt% of the material of the charge generation layer.

5. The electroluminescent device according to claim 1, characterized in that, The thickness of the charge generation layer is 5~30 nm; and / or The average particle size of the first metal oxide, the second metal oxide, and the third metal oxide is 3~15 nm, respectively.

6. The electroluminescent device according to any one of claims 1 to 5, characterized in that, Each of the light-emitting units independently includes: a light-emitting layer; the material of the light-emitting layer is selected from one or more of the following: single-structure quantum dots, core-shell structure quantum dots, doped or undoped inorganic perovskite quantum dots, and organic-inorganic hybrid perovskite quantum dots; wherein, the single-structure quantum dots are selected from one or more of the following: group II-VI compounds, group III-V compounds, group II-V compounds, group III-VI compounds, group IV-VI compounds, group I-III-VI compounds, group II-IV-VI compounds, and group IV elements; the group II-VI compounds are selected from one or more of the following: CdSe, CdS, CdTe, ZnSe, ZnS, CdTe, ZnTe, CdZnS, CdZnSe, CdZnTe, ZnSeS, ZnSeTe, ZnTeS, CdSeS, CdSeTe, CdTeS, CdZnSeS, CdZnSeTe, and CdZnSTe. The III-V group compounds are selected from one or more of InP, InAs, GaP, GaAs, GaN, GaSb, AlN, AlP, InAsP, InNP, InNSb, GaAlNP, and InAlNP; the IV-VI group compounds are selected from one or more of PbS and PbSe; the I-III-VI group compounds are selected from one or more of CuInS2, CuInSe2, and AgInS2; the group IV elemental is selected from one or more of silicon and germanium; the core of the core-shell quantum dot is selected from any of the single-structure quantum dots; the shell material of the core-shell quantum dot is selected from one or more of CdS, CdTe, CdSe, CdSeTe, CdZnSe, CdZnS, CdSeS, ZnSe, ZnTe, ZnSeS, and ZnS; the general structural formula of the inorganic perovskite quantum dot is AMX3, where A is Cs. + M is 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 them, X is selected from Cl - ,Br - I - One or more of the following; the general structural formula of the organic-inorganic hybrid perovskite quantum dots is BMX3, where B is selected from CH3(CH2). n-2 NH 3+ NH3(CH2) n NH3 2+ One or more of the following, where n≥2, and M is 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 them, X is selected from Cl - ,Br - I - One or more of them.

7. The electroluminescent device according to claim 6, characterized in that, Each of the light-emitting units also independently includes: A first charge functional layer is disposed on the side of the light-emitting layer near the first electrode; and A second charge functional layer is disposed on the side of the light-emitting layer near the second electrode; The first charge functional layer and the second charge functional layer each independently include a charge injection layer and / or a charge transport layer, and each charge generation layer is disposed between the second charge functional layer of one light-emitting unit and the first charge functional layer of another light-emitting unit.

8. The electroluminescent device according to claim 7, characterized in that, The materials of the first electrode and the second electrode are independently selected from one or more of doped or undoped metals, silicon carbon materials, doped or undoped metal oxides, and composite electrode materials; wherein the doped or undoped metals are selected from one or more of Al, Ag, Cu, Mo, Au, Ba, Ca, Mg, Ni, Pt, Ir, Ca:Al, LiF:Ca, LiF:Al, BaF2:Al, CsF:Al, CaCO3:Al, BaF2:Ca:Al, Au:Mg, and Ag:Mg; and the silicon carbon materials are selected from one or more of silicon, graphite, carbon nanotubes, graphene, and carbon fibers. The doped or undoped metal oxide is selected from one or more of ITO, FTO, ATO, AZO, GZO, IZO, MZO, AMO, ITZO, ICO, SnO2, In2O3, Cd:ZnO, and Ga:SnO2; the composite electrode material is selected from one or more of AZO / Ag / AZO, AZO / Al / AZO, ITO / Ag / ITO, ITO / Al / ITO, ZnO / Ag / ZnO, ZnO / Al / ZnO, TiO2 / Ag / TiO2, TiO2 / Al / TiO2, ZnS / Ag / ZnS, and ZnS / Al / ZnS; and / or The material of the charge injection layer is selected from Ca, Ba, CsF, CsCO3, PEIE, PEI, LiF, NaF, poly(ethylene dioxythiophene):polystyrene sulfonate, poly[9,9-dioctyl-fluorene-co-N-(4-butylphenyl)-diphenylamine], polyarylamines, poly(N-vinylcarbazole), polyaniline, polythiophene, polypyrrole, N,N,N',N'-tetra(4-methoxyphenyl)-benzidine, 4-bis[N-(1-naphthyl)-N-phenyl-amino]biphenyl, 4,4',4''- One or more of the following: tris[phenyl(m-tolyl)amino]triphenylamine, 4,4',4''-tris(N-carbazolyl)triphenylamine, 1,1-bis[(di-4-tolylamino)phenylcyclohexane, tetrafluoro-tetracyanoquinone dimethane-doped 4,4',4''-tris(diphenylamino)triphenylamine, p-doped phthalocyanine, F4-TCNQ-doped N,N′-diphenyl-N,N′-di(1-naphthyl)-1,1′-biphenyl-4,4″-diamine, hexaazabenzophenanthrene-hexanonitrile, and metal oxides; and / or The charge transport layer material is selected from doped or undoped oxides, doped or undoped semiconductor particles, nitrides, Alq3, Almq3, DVPBi, TAZ, OXD, PBD, BND, PV, CBP, α-NPD, TPD, spiro-TPD, DNTPD, TCTA, m-MTDATA, TAPC, TFB, poly-TPD, polyaniline, polyfluorene, polypyrrole, PPV, MEH-PPV, MOMO-PPV, copper phthalocyanine, aromatic tertiary amines, polynuclear aromatic tertiary amines, 4,4'-bis(p-carbazolyl)-1,1'-biphenyl compounds, N,N,N',N'-tetraarylbenzidine, PEDOT:PSS and its derivatives, PVK and its derivatives, polymethacrylate and its derivatives, poly(9 The oxide is selected from one or more of the following: 9-octylfluorene and its derivatives, poly(spirofluorene) and its derivatives, NPB, spiroNPB, and HATCN; wherein the oxide is selected from one or more of the following: TiO2, ZnO, ZrO2, SnO2, WO3, NiO, Ta2O3, HfO2, Al2O3, ZrSiO4, BaTiO3, BaZrO3, SrTiO3, MgTiO3, TiLiO, ZnAlO, ZnSnO, ZnLiO, and InSnO; the semiconductor particle is selected from one or more of the following: CdS, ZnSe, and ZnS; the nitride is selected from Si3N4; and the doping elements of the oxide and the semiconductor particle are selected from one or more of the following: Al, Mg, In, Li, Ga, Cd, Cs, and Cu.

9. A method for fabricating an electroluminescent device, characterized in that, include: Provide the first electrode; At least two light-emitting units and at least one charge-generating layer are formed on the first electrode; wherein each charge-generating layer is disposed between two adjacent light-emitting units, and the material of the charge-generating layer includes a first metal oxide, a second metal oxide, and a third metal oxide, wherein the conduction band energy level of the first metal oxide is between the conduction band energy level of the second metal oxide and -4.5 eV, and the valence band energy level of the third metal oxide is between the conduction band energy level of the first metal oxide and -5.5 eV; and A second electrode is formed on the light-emitting unit; Wherein, -5.0eV≤conduction band energy level of the first metal oxide≤-4.5eV; -5.0eV≤conduction band energy level of the second metal oxide<-4.5eV; -5.5eV≤valence band energy level of the third metal oxide≤-4.5eV; the first metal oxide is an n-type semiconductor; and the third metal oxide is a p-type semiconductor.

10. A display device, characterized in that, It includes the electroluminescent device according to any one of claims 1 to 8, or the electroluminescent device prepared by the preparation method according to claim 9.

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