Quantum dot light emitting diode and preparation method thereof

Abstract

The application discloses a quantum dot light emitting diode and a preparation method thereof, and the quantum dot light emitting diode comprises a quantum dot light emitting layer arranged between a cathode and an anode, and a hole transport layer arranged between the anode and the quantum dot light emitting layer, wherein an interface layer is arranged between the hole transport layer and the quantum dot light emitting layer, the interface layer is garnet, and a general structure formula of the garnet is Li3N3M2O 12 wherein M is Te or W; N is Y, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb or Lu; and a HOMO energy level of the interface layer is greater than a HOMO energy level of the hole transport layer and less than a HOMO energy level of the quantum dot light emitting layer. In the application, the interface layer can effectively reduce a hole injection barrier, improve a hole injection rate, effectively prevent electron tunneling and hole recombination in a non-quantum dot light emitting area, and thus improve the light emitting efficiency of the device.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of quantum dots, in particular to a quantum dot light emitting diode and a preparation method thereof. BACKGROUND

[0002] Quantum dot light emitting diode (QLED) has high color purity, narrow half-peak width, high light emitting efficiency, adjustable light emitting color and good device stability, etc., which makes it have wide application prospects in the fields of flat panel display, solid state lighting, etc. With the continuous development of research and development, the external quantum efficiency (EQE) of quantum dot light emitting diode has been significantly improved, among which the external quantum efficiency of red quantum dot light emitting diode and green quantum dot light emitting diode is higher than 25% level, which is comparable to organic light emitting diode (OLED) in efficiency, but the external quantum efficiency and lifetime of blue quantum dot light emitting diode still cannot meet the requirements.

[0003] Similar to OLED device, QLED device structure is usually composed of anode, hole injection layer, hole transport layer, quantum dot light emitting layer, electron transport layer and cathode, and electrons and holes are injected from the cathode and anode respectively, and then recombine and emit light in the quantum dot light emitting layer. The existing electron transport layer is usually composed of nano-zinc oxide particles, which has a high carrier concentration and mobility; the organic polymer materials used in the hole transport layer, such as PVK, TFB, etc., due to the low carrier mobility of the hole transport layer and the deep energy level of the quantum dot, which leads to the difficulty of hole injection, so that the holes are accumulated in the hole transport layer or the interface layer between the hole transport layer and the quantum dot light emitting layer for a long time, and the excessive injection of electrons leads to the transition of electrons to the hole transport layer or the interface layer between the hole transport layer and the quantum dot light emitting layer, which finally leads to the recombination of electrons and holes in the non-light emitting layer, which seriously affects the efficiency and lifetime of QLED device.

[0004] Therefore, the prior art still needs to be improved. SUMMARY

[0005] In view of the deficiencies of the prior art, the purpose of the present application is to provide a quantum dot light emitting diode and a preparation method thereof, which aims to solve the problem of low light emitting efficiency of the existing quantum dot light emitting diode.

[0006] The technical scheme of the present application is as follows:

[0007] A quantum dot light emitting diode, comprising a cathode, an anode, a quantum dot light emitting layer arranged between the cathode and the anode, and a hole transport layer arranged between the anode and the quantum dot light emitting layer, wherein an interface layer is arranged between the hole transport layer and the quantum dot light emitting layer, the material of the interface layer is garnet, and the structure general formula of the garnet is Li3N3M2O 12Wherein, M is Te or W; N is Y, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb or Lu; the HOMO energy level of the interface layer is greater than the HOMO energy level of the hole transport layer and less than the HOMO energy level of the quantum dot light emitting layer.

[0008] A preparation method of a quantum dot light emitting diode, comprising the steps of:

[0009] Providing an anode substrate, and a hole transport layer is prepared on the anode substrate;

[0010] An interface layer is prepared on the hole transport layer, and the material of the interface layer is garnet, and the general structure of the garnet is Li3N3M2O 12 Wherein, M is Te or W; N is Y, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb or Lu;

[0011] A quantum dot light emitting layer is prepared on the interface layer;

[0012] A cathode is prepared on the quantum dot light emitting layer, and the quantum dot light emitting diode is prepared;

[0013] Alternatively, a cathode substrate is provided, and a quantum dot light emitting layer is prepared on the cathode substrate;

[0014] An interface layer is prepared on the surface of the quantum dot light emitting layer, and the material of the interface layer is garnet, and the general structure of the garnet is Li3N3M2O 12 Wherein, M is Te or W; N is Y, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb or Lu;

[0015] A hole transport layer is prepared on the interface layer;

[0016] An anode is prepared on the hole transport layer, and the quantum dot light emitting diode is prepared.

[0017] Beneficial effects: the interface layer is arranged between the hole transport layer and the quantum dot light emitting layer, the HOMO energy level of the interface layer is located between the HOMO energy levels of the hole transport layer and the quantum dot light emitting layer, the injection barrier of holes can be effectively reduced, the material and device recession caused by the accumulation of holes at the barrier interface can be reduced, the interface layer can effectively block the electron tunneling, the recombination of electrons and holes in the non-quantum dot light emitting layer can be avoided, and the light emitting efficiency of the quantum dot light emitting diode is improved. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 It is a structure schematic diagram of a preferred embodiment of a positive structure quantum dot light emitting diode of the present application.

[0019] Figure 2 A structure diagram of a preferred embodiment of a quantum dot light emitting diode of the present application.

[0020] Figure 3 A flow chart of a preferred embodiment of a preparation method of a quantum dot light emitting diode of the present application.

[0021] Figure 4 A flow chart of a preferred embodiment of a preparation method of a quantum dot light emitting diode of the present application. DETAILED DESCRIPTION

[0022] The present application provides a quantum dot light emitting diode and a preparation method thereof. In order to make the purpose, technical scheme and effects of the present application more clear and explicit, the present application is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0023] The quantum dot light emitting diode has various forms, and the quantum dot light emitting diode is divided into a formal structure and a reverse structure. The quantum dot light emitting diode of the reverse structure can include a substrate, a cathode, a quantum dot light emitting layer, a hole transport layer and an anode which are stacked from bottom to top. In the specific embodiments of the present application, the quantum dot light emitting diode of the formal structure as shown in Figure 1 will be mainly introduced as an example. Specifically, the quantum dot light emitting diode of the formal structure includes an anode arranged on the surface of a substrate, a hole transport layer arranged on the surface of the anode, an interface layer arranged on the surface of the hole transport layer, a quantum dot light emitting layer arranged on the interface layer, and a cathode arranged on the surface of the quantum dot light emitting layer. The interface layer material is a garnet, and the structure general formula of the garnet is Li3N3M2O 12 wherein M is Te or W; N is Y, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb or Lu, and the HOMO energy level of the interface layer is greater than the HOMO energy level of the hole transport layer and less than the HOMO energy level of the quantum dot light emitting layer.

[0024] In particular, because there is a large potential barrier between the highest occupied molecular orbital (HOMO) of the commonly used hole transport layer and the work function of the quantum dot light emitting layer, it is difficult for holes to be injected from the hole transport layer to the quantum dot light emitting layer, resulting in an imbalance between the injection of holes and electrons, which seriously affects the light emitting efficiency of the quantum dot light emitting diode. The present embodiment provides an interface layer made of garnet between the hole transport layer and the quantum dot light emitting layer, the HOMO energy level of the interface layer is greater than the HOMO energy level of the hole transport layer and less than the HOMO energy level of the quantum dot light emitting layer, the interface layer can effectively reduce the injection potential barrier of holes, thereby reducing the material and device degradation caused by the accumulation of holes at the potential barrier interface, thereby effectively improving the light emitting efficiency and service life of the quantum dot light emitting diode. The size of the HOMO energy level in the present embodiment refers to the absolute value of the HOMO energy level. That is, the absolute value of the HOMO energy level of the interface layer in the present embodiment is greater than the absolute value of the HOMO energy level of the hole transport layer and less than the absolute value of the HOMO energy level of the quantum dot light emitting layer.

[0025] Further, because the energy level potential barrier between the electron transport material and the quantum dot light emitting layer is usually small, electron injection occurs easily, which causes some electrons to easily tunnel to the hole transport layer or the interface between the hole transport layer and the quantum dot light emitting layer, and to recombine with holes in the non-quantum dot light emitting layer region, thereby affecting the overall light emitting efficiency of the quantum dot light emitting diode. The present embodiment provides an interface layer composed of garnet between the hole transport layer and the quantum dot light emitting layer, the interface layer material is garnet, the general structure of the garnet is Li3N3M2O 12 , wherein M is Te or W; N is Y, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb or Lu, the garnet has the properties of conducting ions and holes, but not electrons, therefore, the garnet not only effectively helps the injection of holes, but also effectively prevents the tunneling of electrons to the hole transport layer, avoiding the device emitting light in the non-light emitting region, thereby improving the overall light emitting efficiency of the quantum dot light emitting diode.

[0026] Further, because the material used in the hole transport layer of the quantum dot light emitting diode is usually an organic material, such as PEDOT (polythiophene), etc., such materials are sensitive to water and oxygen, and the gradual penetration of water and oxygen from the encapsulating glue will affect the stability of hole injection and transport, the present embodiment further effectively blocks the penetration of water and oxygen by providing an interface layer composed of garnet between the hole transport layer and the quantum dot light emitting layer, thereby improving the service life of the device.

[0027] In some embodiments, Al 3+ , Y 3+ , Ga 3+ , Ta5+ Nb 5+ W 6+ one or more of the metal cations can effectively improve the hole conductivity of the garnet, thereby improving the light emitting efficiency of the quantum dot light emitting diode.

[0028] In some embodiments, the interface layer has a thickness of 10-200 nm. Within this range, the interface layer can both improve the hole injection rate and block the electron tunneling. If the thickness of the interface layer is less than 10 nm, the interface layer has a poor effect of blocking the electron tunneling to the hole transport layer. If the thickness of the interface layer is greater than 200 nm, the hole injection distance is increased, which affects the efficiency of the hole transport to the quantum dot light emitting layer.

[0029] In some embodiments, the HOMO energy level of the interface layer is 4.9-6.0 eV. In this embodiment, the HOMO energy level of the hole transport layer is generally 4.9-5.4 eV, and the HOMO energy level of the quantum dot light emitting layer is generally 5.9-6.5 eV. At this time, the HOMO energy level of the interface layer is between the HOMO energy levels of the hole transport layer and the quantum dot light emitting layer, and thus the hole injection barrier can be effectively reduced, the hole injection rate can be promoted, the material and device degradation caused by the accumulation of holes at the barrier interface can be reduced, and thus the light emitting efficiency and the service life of the quantum dot light emitting diode can be effectively improved. As an example, when TFB (HOMO energy level of 5.4 eV) is used as the hole transport layer material, and Cds-ZnSe quantum dots (HOMO energy level of 5.9-6.1 eV) are used as the quantum dot light emitting layer material, the HOMO energy level of the interface layer can be 5.4-6 eV.

[0030] In some specific embodiments, the interface layer material is Li3Nd3Te2O 12 In this embodiment, the HOMO energy level of Li3Nd3Te2O 12 is between the HOMO energy levels of the hole transport layer and the quantum dot light emitting layer, and thus the hole injection barrier can be effectively reduced, the hole injection rate can be promoted, the material and device degradation caused by the accumulation of holes at the barrier interface can be reduced, and thus the light emitting efficiency and the service life of the quantum dot light emitting diode can be effectively improved.

[0031] In some embodiments, the hole transport layer material is selected from one or more of poly(9,9-dioctylfluorene-CO-N-(4-butylphenyl)diphenylamine) (TFB), polyvinylcarbazole (PVK), poly(N,N'bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine) (Poly-TPD), poly(9,9-dioctylfluorene-co-bis-N,N-phenyl-1,4-phenylenediamine) (PFB), 4,4',4"-tris(carbazol-9-yl)triphenylamine (TCTA), 4,4'-bis(9-carbazolyl) biphenyl (CBP), N,N'-diphenyl-N,N'-di(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (TPD), N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine (NPB), but not limited thereto.

[0032] In some embodiments, the quantum dot light emitting layer is selected from one or more of binary phase quantum dots, ternary phase quantum dots, and quaternary phase quantum dots, but not limited thereto. As an example, the binary phase quantum dots are at least one of CdS, CdSe, CdTe, InP, AgS, PbS, PbSe, HgS; and / or, the ternary phase quantum dots are at least one of Zn X Cd 1-X S, Cu X In 1- X S, Zn X Cd 1-X Se, Zn X Se 1-X S, Zn X Cd 1-X Te, PbSe X S 1-X at least one of Zn X Cd 1-X S / ZnSe, Cu X In 1-X S / ZnS, Zn X Cd 1-X Se / ZnS, CuInSeS, Zn X Cd 1-X Te / ZnS, PbSe X S 1-X at least one of / ZnS, wherein 0 < X < 1.

[0033] In some embodiments, an electron functional layer is disposed between the quantum dot light emitting layer and the cathode, the electron functional layer including a hole blocking layer, an electron injection layer, and an electron transport layer, but not limited thereto.

[0034] In some embodiments, the electron transport layer material is selected from one or more of ZnO, TiO, NiO, W2O3, Mo2O3, TiO2, SnO, ZrO2, and Ta2O3, but not limited thereto.

[0035] In some embodiments, a hole injection layer is further provided between the anode and the hole transport layer.

[0036] In some embodiments, the hole injection layer is one or more of PEDOT:PSS, WO3, MoO3, and V2O5, but not limited thereto.

[0037] In some embodiments, the hole injection layer has a thickness of 30-120 nm.

[0038] In some embodiments, the cathode can be Au, Ag, Al, Cu, Mo, or alloys thereof, but not limited thereto.

[0039] In some embodiments, the anode has a thickness of 5-120 nm.

[0040] In some embodiments, the hole transport layer has a thickness of 30-120 nm.

[0041] In some embodiments, the quantum dot light emitting layer has a thickness of 10-200 nm.

[0042] In some embodiments, the electron transport layer has a thickness of 5-100 nm, and the cathode has a thickness of 5-120 nm.

[0043] In some embodiments, the anode is one or more of ITO, FTO, ATO, AZO, GZO, IZO, MZO, and AMO, but not limited thereto.

[0044] In some embodiments, the present application further provides a quantum dot light emitting diode with an inverted structure, as shown in FIG. 1. Figure 2 As shown in FIG. 1, the quantum dot light emitting diode with the inverted structure includes a cathode provided on a surface of a substrate, a quantum dot light emitting layer provided on a surface of the cathode, an interface layer provided on a surface of the quantum dot light emitting layer, a hole transport layer provided on a surface of the interface layer, and an anode provided on a surface of the hole transport layer, wherein the interface layer material is a garnet, and the structure general formula of the garnet is Li3N3M2O12, wherein M is Te or W, and N is Y, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, or Lu, and the HOMO energy level of the interface layer is greater than the HOMO energy level of the hole transport layer and less than the HOMO energy level of the quantum dot light emitting layer. 12

[0045] ​The embodiment sets an interface layer made of garnet between the hole transport layer and the quantum dot light-emitting layer, the HOMO energy level of the interface layer is greater than the HOMO energy level of the hole transport layer and less than the HOMO energy level of the quantum dot light-emitting layer, the interface layer can effectively reduce the injection barrier of holes, thereby reducing the material and device degradation caused by the accumulation of holes at the barrier interface, thereby effectively improving the light-emitting efficiency and service life of the quantum dot light-emitting diode. The interface layer material is garnet, the general structure of the garnet is Li3N3M2O 12 , wherein M is Te or W; N is Y, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb or Lu, the garnet has the properties of conducting ions and holes, but not electrons, the ion and hole conductivity of the garnet at room temperature is > 10 -3 S / cm, the electron conductivity of the garnet is less than the ion / hole conductivity by more than four orders of magnitude, and the garnet also has a wide electrochemical stability window: 0-9V. Therefore, the garnet not only effectively helps the injection of holes, but also effectively prevents the tunneling of electrons to the hole transport layer, avoiding the device emitting light in the non-light-emitting area, thereby improving the overall light-emitting efficiency of the quantum dot light-emitting diode.

[0046] In some embodiments, a preparation method of a quantum dot light-emitting diode with the positive structure as shown in Figure 1 is also provided, which comprises the steps of: Figure 3 as shown in the figure, comprising the steps of:

[0047] S10, providing an anode substrate, a hole transport layer is provided on the anode substrate;

[0048] S20, preparing an interface layer on the hole transport layer, the interface layer material is garnet, the general structure of the garnet is Li3N3M2O 12 , wherein M is Te or W; N is Y, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb or Lu;

[0049] S30, preparing a quantum dot light-emitting layer on the interface layer;

[0050] S40, preparing a cathode on the quantum dot light-emitting layer, thereby obtaining the quantum dot light-emitting diode.

[0051] In the embodiment, the preparation method of each layer can be a chemical method or a physical method. The chemical method includes, but is not limited to, one or more of a chemical vapor deposition method, a sequential ion layer adsorption and reaction method, an anodic oxidation method, an electrolytic deposition method, and a coprecipitation method. The physical method includes, but is not limited to, a physical coating method or a solution method. The solution method includes, but is not limited to, a spin coating method, a printing method, a blade coating method, an immersion-tow draw method, an immersion method, a spray coating method, a roll coating method, a casting method, a slot coating method, and a strip coating method. The physical coating method includes, but is not limited to, one or more of a thermal evaporation coating method, an electron beam evaporation coating method, a magnetron sputtering method, a multi-arc ion coating method, a physical vapor deposition method, an atomic layer deposition method, and a pulsed laser deposition method.

[0052] In some specific embodiments, the interface layer is prepared on the hole transport layer by a spin coating method, which specifically includes the steps of: dispersing the garnet in an organic solvent to obtain a garnet solution; spin coating the garnet solution on the surface of the hole transport layer, and performing thermal annealing at 100°C for 30 minutes to obtain the interface layer. In the embodiment, the organic solvent includes, but is not limited to, ethanol, methanol, butanol, acetone, isopropyl ketone, butyronitrile, chlorobenzene, toluene, xylene, dimethylformamide, dimethyl sulfoxide, N-methyl pyrrolidone, and ethyl acetate. In the embodiment, the concentration of the garnet solution is 1-2 wt%, and within the concentration range, the interface layer prepared can reduce the interface impedance and effectively improve the light-emitting performance of the quantum dot light-emitting diode.

[0053] In some embodiments, a preparation method of a quantum dot light-emitting diode with an inverted structure is also provided, which includes the steps of: Figure 2 As shown in the preparation method of the QLED with an inverted structure, Figure 4 As shown in the preparation method of the QLED with an inverted structure,

[0054] S100, providing a cathode substrate, and preparing a quantum dot light-emitting layer on the cathode substrate;

[0055] S200, preparing an interface layer on the surface of the quantum dot light-emitting layer, wherein the interface layer material is garnet, and the structure general formula of the garnet is Li3N3M2O 12 wherein M is Te or W; and N is Y, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, or Lu;

[0056] S300, preparing a hole transport layer on the interface layer;

[0057] S400, preparing an anode on the hole transport layer to obtain the quantum dot light-emitting diode.

[0058] In one embodiment of the present application, the cathode substrate comprises a substrate, a bottom electrode disposed on the substrate, the bottom electrode being a cathode; in another embodiment of the present application, the cathode substrate can comprise a substrate, a bottom electrode disposed on the surface of the substrate, and an electron injection layer disposed on the surface of the substrate; in another embodiment of the present application, the cathode substrate can comprise a substrate, a bottom electrode disposed on the surface of the substrate, an electron injection layer disposed on the surface of the substrate, and an electron transport layer disposed on the surface of the electron injection layer; in another embodiment of the present application, the anode substrate can comprise a substrate, a bottom electrode disposed on the surface of the substrate, an electron injection layer disposed on the surface of the substrate, an electron transport layer disposed on the surface of the electron injection layer, and a hole blocking layer disposed on the surface of the electron transport layer.

[0059] The preparation method of each layer can be a chemical method or a physical method, wherein the chemical method includes but is not limited to one or more of chemical vapor deposition, sequential ionic layer adsorption and reaction, anodic oxidation, electrolytic deposition, and coprecipitation; the physical method includes but is not limited to physical coating or a solution method, wherein the solution method includes but is not limited to spin coating, printing, blade coating, dip-coating, immersion, spraying, roll coating, casting, slot coating, and stripe coating; the physical coating method includes but is not limited to one or more of thermal evaporation coating, electron beam evaporation coating, magnetron sputtering, multi-arc ion coating, physical vapor deposition, atomic layer deposition, and pulsed laser deposition.

[0060] The present application is further explained and described by specific embodiments of a quantum dot light emitting diode and a preparation method thereof as follows:

[0061] Embodiment 1

[0062] A preparation method of a quantum dot light emitting diode with a normal bottom emission structure, comprising the following steps:

[0063] Step S1: depositing a hole injection layer on a transparent anode substrate, the transparent anode being ITO, the hole injection layer material being WO3, the thickness of the transparent anode being 20 nm, and the thickness of the hole injection layer being 60 nm;

[0064] Step S2: depositing a hole transport layer on the hole injection layer, the hole transport layer material being PFB, and the thickness of the hole transport layer being 60 nm;

[0065] Step S3: depositing an interface layer on the hole transport layer, the interface layer material being Li3Nd3Te2O 12 , and the thickness of the interface layer being 100 nm;

[0066] Step S4: depositing a quantum dot light emitting layer on the interface layer, the quantum dot light emitting layer material is PbSe, the thickness of the quantum dot light emitting layer is 50 nm;

[0067] Step S5: depositing an electron transport layer on the quantum dot light emitting layer, the electron transport layer material is TiO, the thickness of the electron transport layer is 60 nm;

[0068] Step S6: depositing a metal cathode on the electron transport layer, the cathode material is Ag, the thickness of the cathode is 100 nm, and the cathode reflects no less than 98% of visible light.

[0069] Example 2

[0070] A preparation method of a quantum dot light emitting diode with an upside top emission structure, comprising the following steps:

[0071] Step S1: depositing a hole injection layer on a transparent anode substrate, the transparent anode is FTO, the hole injection layer material is WO3, the thickness of the transparent anode is 20 nm, and the thickness of the hole injection layer is 60 nm;

[0072] Step S2: depositing a hole transport layer on the hole injection layer, the hole transport layer material is TCTA, and the thickness of the hole transport layer is 60 nm;

[0073] Step S3: depositing an interface layer on the hole transport layer, the interface layer material is Li3Nd3Te2O 12 , and the thickness of the interface layer is 100 nm;

[0074] Step S4: depositing a quantum dot light emitting layer on the interface layer, the quantum dot light emitting layer material is InP, and the thickness of the quantum dot light emitting layer is 50 nm;

[0075] Step S5: depositing an electron transport layer on the quantum dot light emitting layer, the electron transport layer material is NiO, and the thickness of the electron transport layer is 60 nm;

[0076] Step S6: depositing a cathode on the electron transport layer, the cathode material is Ag, the thickness of the cathode is 100 nm, and the cathode transmits no less than 90% of visible light.

[0077] Example 3

[0078] A preparation method of a quantum dot light emitting diode with an upside top emission structure, comprising the following steps:

[0079] Step S1: depositing an Ag layer on a substrate by evaporation, and the thickness of the Ag layer is 5 nm;

[0080] Step S2: Depositing an electron transport layer on the Ag layer, the electron transport layer material is SnO, the thickness of the electron transport layer is 50 nm;

[0081] Step S3: Depositing a quantum dot light emitting layer on the electron transport layer, the quantum dot light emitting layer material is CdSe, the thickness of the quantum dot light emitting layer is 50 nm;

[0082] Step S4: Depositing an interface layer on the quantum dot light emitting layer, the material of the interface layer is Li3Nd3Te2O 12 , the thickness of the interface layer is 80 nm;

[0083] Step S5: Depositing a hole transport layer on the interface layer, the hole transport layer material is PVK, the thickness of the hole transport layer is 80 nm;

[0084] Step S6: Depositing a hole injection layer on the hole transport layer, the hole injection layer material is PEDOT:PSS, the thickness of the hole injection layer is 60 nm;

[0085] Step S7: Depositing an anode on the hole injection layer, the anode material is ITO, the thickness of the anode is 120 nm; the anode reflects no less than 98% of visible light.

[0086] Example 4

[0087] A preparation method of a quantum dot light emitting diode with an inverted top emission structure, comprising the following steps:

[0088] Step S1: Depositing an Ag layer on a substrate by evaporation, the thickness of the Ag layer is 5 nm;

[0089] Step S2: Depositing an electron transport layer on the Ag layer, the electron transport layer material is TiO, the thickness of the electron transport layer is 60 nm;

[0090] Step S3: Depositing a quantum dot light emitting layer on the electron transport layer, the quantum dot light emitting layer material is CdTe, the thickness of the quantum dot light emitting layer is 50 nm;

[0091] Step S4: Depositing an interface layer on the quantum dot light emitting layer, the material of the interface layer is Li3Nd3Te2O 12 , the thickness of the interface layer is 80 nm;

[0092] Step S5: Depositing a hole transport layer on the interface layer, the hole transport layer material is PFB, the thickness of the hole transport layer is 80 nm;

[0093] Step S6: depositing a hole injection layer on the hole transport layer, the hole injection layer material is MoO3, the thickness of the hole injection layer is 60 nm;

[0094] Step S7: depositing an anode on the hole injection layer, the anode material is ITO, the thickness of the anode is 120 nm; the transmittance of the anode to visible light is not less than 90%.

[0095] Comparative Example 1

[0096] A preparation method of a quantum dot light emitting diode with an upside-down bottom emission structure, comprising the following steps:

[0097] Step S1: depositing a hole injection layer on a transparent anode substrate, the transparent anode is ITO, the hole injection layer material is WO3, the thickness of the transparent anode is 20 nm, and the thickness of the hole injection layer is 60 nm;

[0098] Step S2: depositing a hole transport layer on the hole injection layer, the hole transport layer material is PFB, the thickness of the hole transport layer is 60 nm;

[0099] Step S3: depositing a quantum dot light emitting layer on the hole transport layer, the quantum dot light emitting layer material is PbSe, and the thickness of the quantum dot light emitting layer is 50 nm;

[0100] Step S4: depositing an electron transport layer on the quantum dot light emitting layer, the electron transport layer material is TiO, and the thickness of the electron transport layer is 60 nm;

[0101] Step S5: depositing a metal cathode on the electron transport layer, the cathode material is Ag, the thickness of the cathode is 100 nm, and the reflectance of the cathode to visible light is not less than 98%.

[0102] Comparative Example 2

[0103] A preparation method of a quantum dot light emitting diode with an upside-down top emission structure, comprising the following steps:

[0104] Step S1: depositing a hole injection layer on a transparent anode substrate, the transparent anode is FTO, the hole injection layer material is WO3, the thickness of the transparent anode is 20 nm, and the thickness of the hole injection layer is 60 nm;

[0105] Step S2: depositing a hole transport layer on the hole injection layer, the hole transport layer material is TCTA, and the thickness of the hole transport layer is 60 nm;

[0106] Step S3: depositing a quantum dot light emitting layer on the hole transport layer, the quantum dot light emitting layer material is InP, and the thickness of the quantum dot light emitting layer is 50 nm;

[0107] Step S4: Depositing an electron transport layer on the quantum dot light emitting layer, the electron transport layer material is NiO, the thickness of the electron transport layer is 60 nm;

[0108] Step S5: Depositing a cathode on the electron transport layer, the cathode material is Ag, the thickness of the cathode is 100 nm, the transmission of the cathode to visible light is not less than 90%.

[0109] Comparative Example 3

[0110] A preparation method of a quantum dot light emitting diode with an inverted bottom emission structure, comprising the following steps:

[0111] Step S1: Depositing an Ag layer on a substrate by evaporation, the thickness of the Ag layer is 5 nm;

[0112] Step S2: Depositing an electron transport layer on the Ag layer, the electron transport layer material is SnO, the thickness of the electron transport layer is 50 nm;

[0113] Step S3: Depositing a quantum dot light emitting layer on the electron transport layer, the quantum dot light emitting layer material is CdSe, the thickness of the quantum dot light emitting layer is 50 nm;

[0114] Step S4: Depositing a hole transport layer on the quantum dot light emitting layer, the hole transport layer material is PVK, the thickness of the hole transport layer is 80 nm;

[0115] Step S5: Depositing a hole injection layer on the hole transport layer, the hole injection layer material is PEDOT:PSS, the thickness of the hole injection layer is 60 nm;

[0116] Step S6: Depositing an anode on the hole injection layer, the anode material is ITO, the thickness of the anode is 120 nm; the reflection of the anode to visible light is not less than 98%.

[0117] Comparative Example 4

[0118] A preparation method of a quantum dot light emitting diode with an inverted top emission structure, comprising the following steps:

[0119] Step S1: Depositing an Ag layer on a substrate by evaporation, the thickness of the Ag layer is 5 nm;

[0120] Step S2: Depositing an electron transport layer on the Ag layer, the electron transport layer material is TiO, the thickness of the electron transport layer is 60 nm;

[0121] Step S3: depositing a quantum dot light-emitting layer on the electron transport layer, the quantum dot light-emitting layer material being CdTe, the thickness of the quantum dot light-emitting layer being 50 nm;

[0122] Step S4: depositing a hole transport layer on the quantum dot light-emitting layer, the hole transport layer material being PFB, the thickness of the hole transport layer being 80 nm;

[0123] Step S5: depositing a hole injection layer on the hole transport layer, the hole injection layer material being MoO3, the thickness of the hole injection layer being 60 nm;

[0124] Step S6: depositing an anode on the hole injection layer, the anode material being ITO, the thickness of the anode being 120 nm; the transmittance of the anode to visible light being not less than 90%.

[0125] The performance of the quantum dot light-emitting diodes prepared in Examples 1-4 and Comparative Examples 1-4 was tested, and the results are shown in Table 1:

[0126] Table 1: Performance test results of quantum dot light-emitting diodes

[0127]

[0128]

[0129] As can be seen from the data in Table 1, the difference between Example 1 and Comparative Example 1 is only that an interface layer formed by Li3Nd3Te2O 12 is added between the hole transport layer and the quantum dot light-emitting layer, and the external quantum efficiency is increased from 7.9% to 9.1%, and the service life is increased from 5.4 h to 5.7 h; the difference between Example 2 and Comparative Example 2 is only that an interface layer formed by Li3Nd3Te2O 12 is added between the hole transport layer and the quantum dot light-emitting layer, and the external quantum efficiency is increased from 14.6% to 15.3%, and the service life is increased from 3.9 h to 4.3 h; the difference between Example 3 and Comparative Example 3 is only that an interface layer formed by Li3Nd3Te2O 12 is added between the hole transport layer and the quantum dot light-emitting layer, and the external quantum efficiency is increased from 8.3% to 8.7%, and the service life is increased from 5.9 h to 6.1 h; the difference between Example 4 and Comparative Example 4 is only that an interface layer formed by Li3Nd3Te2O 12The interface layer formed by the material improves the external quantum efficiency from 15.8% to 16.4% and the service life from 4.1h to 4.9h. Through the above data, it can be found that the interface layer arranged between the hole transport layer and the quantum dot light emitting layer can effectively improve the external quantum efficiency and the service life of the quantum dot light emitting diode.

[0130] In conclusion, the quantum dot light emitting diode device is optimized, the interface layer is added in the hole transport layer and the quantum dot light emitting layer, so as to reduce the hole injection barrier, improve the hole injection, avoid the accumulation of holes at the interface, effectively reduce the recombination of the electrons which are tunneled to the hole transport layer in the non-quantum dot light emitting area, improve the device efficiency and the service life, the interface layer can also effectively block the influence of water and oxygen on the organic hole injection and transport layer, and improve the device stability.

[0131] It should be understood that the application of the present application is not limited to the above examples, and those skilled in the art can make improvements or changes according to the above description, and all these improvements and changes shall belong to the protection scope of the appended claims of the present application.

Claims

1. A quantum dot light-emitting diode, comprising a cathode, an anode, a quantum dot light-emitting layer disposed between the cathode and the anode, and a hole transport layer disposed between the anode and the quantum dot light-emitting layer, characterized in that, An interface layer is disposed between the hole transport layer and the quantum dot luminescent layer. The interface layer material is garnet, and the general structural formula of garnet is Li3N3M2O. 12 Where M is Te or W; N is Y, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb or Lu; the HOMO energy level of the interface layer is greater than the HOMO energy level of the hole transport layer and less than the HOMO energy level of the quantum dot emitting layer.

2. The quantum dot light-emitting diode according to claim 1, characterized in that, The thickness of the interface layer is 10-200 nm.

3. The quantum dot light-emitting diode according to claim 1, characterized in that, The HOMO energy level of the interface layer is 5.4-6.0 eV.

4. The quantum dot light-emitting diode according to claim 1, characterized in that, The interface layer material is Li3Nd3Te2O 12 .

5. The quantum dot light-emitting diode according to any one of claims 1-3, characterized in that, The hole transport layer material is selected from one or more of TFB, PVK, Poly-TPD, PFB, TCTA, CBP, TPD and NPB.

6. The quantum dot light-emitting diode according to any one of claims 1-3, characterized in that, The quantum dot light-emitting layer material is selected from one or more of binary quantum dots, ternary quantum dots, and quaternary quantum dots.

7. The quantum dot light-emitting diode according to claim 6, characterized in that, The binary quantum dot is at least one of CdS, CdSe, CdTe, InP, AgS, PbS, PbSe, and HgS; and / or, the ternary quantum dot is Zn. X Cd 1-X S, Cu X In 1-X S, Zn X Cd 1-X Se、Zn X Se 1-X S, Zn X Cd 1-X Te, PbSe X S 1-X At least one of the following; and / or, the quaternary quantum dot is Zn X Cd 1-X S / ZnSe, Cu X In 1-X S / ZnS, Zn X Cd 1-X Se / ZnS, CuInSeS, Zn X Cd 1-X Te / ZnS, PbSe X S 1-X At least one of / ZnS, wherein 0 <X<1。 8. The quantum dot light-emitting diode according to claim 1, characterized in that, An electronic functional layer is disposed between the quantum dot light-emitting layer and the cathode; and / or, a hole injection layer is disposed between the anode and the hole transport layer.

9. A method for fabricating a quantum dot light-emitting diode, characterized in that, Including the following steps: An anode substrate is provided, wherein a hole transport layer is disposed on the anode substrate; An interface layer is fabricated on the hole transport layer, wherein the interface layer material is garnet, and the general structural formula of the garnet is Li3N3M2O. 12 Where M is Te or W; N is Y, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb or Lu; A quantum dot light-emitting layer is prepared in the interface layer; A cathode is fabricated in the quantum dot light-emitting layer to obtain the quantum dot light-emitting diode; Alternatively, a cathode substrate is provided, on which a quantum dot light-emitting layer is fabricated; An interface layer is prepared on the surface of the quantum dot luminescent layer. The interface layer material is garnet, and the general structural formula of garnet is Li3N3M2O. 12 Where M is Te or W; N is Y, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb or Lu; A hole transport layer is prepared in the interface layer; An anode is fabricated on the hole transport layer to obtain the quantum dot light-emitting diode. The HOMO energy level of the interface layer is greater than the HOMO energy level of the hole transport layer and less than the HOMO energy level of the quantum dot luminescent layer.

10. The method for fabricating a quantum dot light-emitting diode according to claim 9, characterized in that, The step of preparing the interface layer on the hole transport layer includes: The garnet was dispersed in an organic solvent to prepare a garnet solution; An interface layer is prepared on the surface of the hole transport layer, and the interface layer material is the garnet. Alternatively, the step of preparing an interface layer on the surface of the quantum dot luminescent layer includes: The garnet was dispersed in an organic solvent to prepare a garnet solution; An interface layer is prepared on the surface of the quantum dot luminescent layer, and the interface layer material is the garnet.

11. The method for fabricating a quantum dot light-emitting diode according to claim 10, characterized in that, The concentration of the garnet solution is 1-2 wt%.

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