Quantum dot light emitting diode and preparation method thereof

Abstract

The application discloses a quantum dot light emitting diode and a preparation method thereof. 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. An interface layer is arranged between the hole transport layer and the quantum dot light emitting layer. The material of the interface layer is LiPON. 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. In the application, the interface layer can effectively reduce the hole injection barrier, improve the hole injection rate, effectively prevent the electron from tunneling and the hole from recombining in the non-quantum dot light emitting area, and thus improve the light emitting efficiency of the device.

Description

Technical Field

[0001] This invention relates to the field of quantum dots, and more particularly to a quantum dot light-emitting diode and its fabrication method. Background Technology

[0002] Quantum dot light-emitting diodes (QLEDs) possess excellent characteristics such as high color purity, narrow half-maximum width at half-maximum (WWHM) for high luminous efficiency, tunable emission color, and device stability, making them promising for applications in flat panel displays, solid-state lighting, and other fields. With continuous research and development, the external quantum efficiency (EQE) of quantum dot LEDs has significantly improved. The EQE of red and green quantum dot LEDs both exceed 25%, comparable to that of organic light-emitting diodes (OLEDs). However, the EQE and lifetime of blue quantum dot LEDs still do not meet the requirements.

[0003] Similar to OLED devices, QLED devices typically consist of an anode, a hole injection layer, a hole transport layer, a quantum dot emitting layer, an electron transport layer, and a cathode. Electrons and holes are injected from the cathode and anode, respectively, and recombine in the quantum dot emitting layer to emit light. Current electron transport layers are usually composed of nano-zinc oxide particles, which have high carrier concentration and mobility. The organic polymer materials used in the hole transport layer, such as PVK and TFB, suffer from low carrier mobility and deep quantum dot energy levels, making hole injection difficult. This leads to long-term hole accumulation in the hole transport layer or at the interface between the hole transport layer and the quantum dot emitting layer. Excessive electron injection causes electrons to easily migrate to the hole transport layer or its interface with the quantum dot emitting layer, ultimately resulting in electron-hole recombination in the non-emitting layer, severely impacting the efficiency and lifespan of the QLED device.

[0004] Therefore, existing technologies still need improvement. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a quantum dot light-emitting diode and its preparation method, aiming to solve the problem of low luminous efficiency of existing quantum dot light-emitting diodes.

[0006] The technical solution of the present invention is as follows:

[0007] A quantum dot light-emitting diode includes 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. An interface layer is disposed between the hole transport layer and the quantum dot light-emitting layer, and the interface layer material is LiPON. 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 method for fabricating a quantum dot light-emitting diode, comprising the following steps:

[0009] An anode substrate is provided, wherein a hole transport layer is disposed on the anode substrate;

[0010] An interface layer is fabricated on the hole transport layer, and the interface layer material is LiPON.

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

[0012] A cathode is fabricated in the quantum dot light-emitting layer to obtain the quantum dot light-emitting diode;

[0013] Alternatively, a cathode substrate is provided, on which a quantum dot light-emitting layer is fabricated;

[0014] An interface layer is prepared on the surface of the quantum dot light-emitting layer, and the interface layer material is LiPON;

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

[0016] An anode is fabricated on the hole transport layer to obtain the quantum dot light-emitting diode.

[0017] Beneficial effects: This invention provides an interface layer between the hole transport layer and the quantum dot light-emitting layer. Since 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, it can effectively reduce the hole injection barrier, thereby reducing material and device degradation caused by hole accumulation at the barrier interface. The interface layer can also effectively block electron tunneling, preventing electrons and holes from recombinating in the non-quantum dot light-emitting layer, thereby improving the luminous efficiency of the quantum dot light-emitting diode. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a preferred embodiment of a positive structure quantum dot light-emitting diode according to the present invention.

[0019] Figure 2 This is a schematic diagram of a preferred embodiment of an inverted quantum dot light-emitting diode according to the present invention.

[0020] Figure 3 This is a flowchart of a preferred embodiment of a method for fabricating a positive-structure quantum dot light-emitting diode according to the present invention.

[0021] Figure 4 This is a flowchart of a preferred embodiment of a method for fabricating an inverted quantum dot light-emitting diode according to the present invention. Detailed Implementation

[0022] This invention provides a quantum dot light-emitting diode and its fabrication method. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0023] Quantum dot light-emitting diodes (LEDs) come in various forms, and are classified into formal and inverse structures. The inverse structure quantum dot LED may include a substrate, a cathode, a quantum dot light-emitting layer, a hole transport layer, and an anode, stacked from bottom to top. The specific embodiments of this invention will primarily focus on... Figure 1 The positive-type quantum dot light-emitting diode shown is described as an example. Specifically, the positive-type quantum dot light-emitting diode includes an anode disposed on the surface of a substrate, a hole transport layer disposed on the surface of the anode, an interface layer disposed on the surface of the hole transport layer, a quantum dot light-emitting layer disposed on the interface layer, and a cathode disposed on the surface of the quantum dot light-emitting layer. The interface layer is made of LiPON, 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] Specifically, due to the significant potential barrier between the highest occupied level (HOMO) of the commonly used hole transport layer and the work function of the quantum dot emitting layer, it becomes difficult for holes to be injected from the hole transport layer into the quantum dot emitting layer, leading to an imbalance in hole and electron injection and severely affecting the luminous efficiency of quantum dot LEDs. This embodiment addresses this by placing an interface layer made of LiPON between the hole transport layer and the quantum dot emitting layer. The HOMO level of the interface layer is greater than that of the hole transport layer but less than that of the quantum dot emitting layer. This interface layer effectively reduces the hole injection barrier, thereby reducing material and device degradation caused by hole accumulation at the barrier interface, and thus effectively improving the luminous efficiency and lifespan of the quantum dot LED. In this embodiment, the HOMO level refers to its absolute value. That is, the absolute value of the HOMO level of the interface layer is greater than that of the hole transport layer but less than that of the quantum dot emitting layer.

[0025] Furthermore, since the energy level barrier between the electron transport material and the quantum dot emitting layer is typically small, electron injection is relatively easy to occur. This leads to some electrons easily tunneling to the hole transport layer or the interface between the hole transport layer and the quantum dot emitting layer, and recombinating with holes in non-quantum dot emitting layer regions, thus affecting the overall luminous efficiency of the quantum dot emitting diode. This embodiment addresses this by setting an interface layer composed of LiPON between the hole transport layer and the quantum dot emitting layer. LiPON has the properties of conducting ions and holes but not electrons. The ionic and hole conductivity of LiPON is more than four orders of magnitude higher than its electronic conductivity. Therefore, LiPON can not only effectively facilitate hole injection but also effectively prevent electrons from tunneling to the hole transport layer, avoiding luminescence in non-emitting regions, thereby improving the overall luminous efficiency of the quantum dot emitting diode.

[0026] Furthermore, since the hole transport layer of quantum dot light-emitting diodes is usually made of organic materials, such as PEDOT (polythiophene), these materials are sensitive to water and oxygen. Water and oxygen gradually penetrate from the encapsulating adhesive, affecting the stability of hole injection and transport. In this embodiment, by setting an interface layer composed of LiPON between the hole transport layer and the quantum dot light-emitting layer, water and oxygen penetration can be effectively blocked, thereby improving the lifespan of the device.

[0027] In some embodiments, the thickness of the interface layer is 10-200 nm. Within this range, the interface layer can both improve the hole injection rate and block electron tunneling. If the thickness of the interface layer is less than 10 nm, its effect on blocking electron tunneling to the hole transport layer is poor; if the thickness of the interface layer is greater than 200 nm, it increases the hole injection distance and affects the efficiency of hole transport to the quantum dot light-emitting layer.

[0028] In some embodiments, the HOMO level of the interface layer is 4.9-6.0 eV. In this embodiment, since the HOMO level of the hole transport layer is typically 4.9-5.4 eV and the HOMO level of the quantum dot emitting layer is typically 5.9-6.5 eV, the HOMO level of the interface layer is located between the HOMO levels of the hole transport layer and the quantum dot emitting layer. Therefore, it can effectively reduce the hole injection barrier, promote the hole injection rate, and reduce the material and device degradation caused by hole accumulation at the barrier interface, thereby effectively improving the luminous efficiency and lifespan of the quantum dot emitting diode. As an example, when TFB (HOMO level of 5.4 eV) is used as the hole transport layer material and Cds-ZnSe quantum dots (HOMO level of 5.9-6.1 eV) is used as the quantum dot emitting layer material, the HOMO level of the interface layer can be 5.4-6 eV.

[0029] 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(carbazole-9-yl)triphenylamine (TCTA), 4,4'-bis(9-carbazole)biphenyl (CBP), N,N'-diphenyl-N,N'-di(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (TPD), and N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine (NPB), but is not limited thereto.

[0030] In some embodiments, the quantum dot emitting layer is selected from one or more of binary quantum dots, ternary quantum dots, and quaternary quantum dots, but is not limited thereto. For example, 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。

[0031] In some embodiments, an electronic functional layer is disposed between the quantum dot light-emitting layer and the cathode. The electronic functional layer includes a hole blocking layer, an electron injection layer, and an electron transport layer, but is not limited thereto.

[0032] In some embodiments, the electron transport layer material is selected from one or more of ZnO, TiO, NiO, W2O3, Mo2O3, SnO, ZrO2, and Ta2O3, but is not limited thereto.

[0033] In some embodiments, a hole injection layer is also provided between the anode and the hole transport layer.

[0034] In some embodiments, the hole injection layer is one or more of PEDOT:PSS, WO3, MoO3 and V2O5, but is not limited thereto.

[0035] In some embodiments, the thickness of the hole injection layer is 30-120 nm.

[0036] In some embodiments, the cathode may be Au, Ag, Al, Cu, Mo, or alloys thereof, but is not limited thereto.

[0037] In some embodiments, the thickness of the anode is 5-120 nm.

[0038] In some embodiments, the thickness of the hole transport layer is 30-120 nm.

[0039] In some embodiments, the thickness of the quantum dot light-emitting layer is 10-200 nm.

[0040] In some embodiments, the thickness of the electron transport layer is 5-100 nm; the thickness of the cathode is 5-120 nm.

[0041] In some embodiments, the anode is one or more of ITO, FTO, ATO, AZO, GZO, IZO, MZO, and AMO, but is not limited thereto.

[0042] In some embodiments, the present invention also provides a quantum dot light-emitting diode with an inversion structure, such as... Figure 2 As shown, the inverted quantum dot light-emitting diode includes a cathode disposed on the surface of a substrate, a quantum dot light-emitting layer disposed on the surface of the cathode, an interface layer disposed on the surface of the quantum dot light-emitting layer, a hole transport layer disposed on the surface of the interface layer, and an anode disposed on the surface of the hole transport layer. The interface layer is made of LiPON, 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.

[0043] This embodiment employs an interface layer made of LiPON between the hole transport layer and the quantum dot emitting layer. The HOMO level of the interface layer is higher than that of the hole transport layer but lower than that of the quantum dot emitting layer. This interface layer effectively reduces the hole injection barrier, thereby minimizing material and device degradation caused by hole accumulation at the barrier interface, thus significantly improving the luminous efficiency and lifespan of the quantum dot emitting diode. The interface layer material is LiPON, which conducts ions and holes but not electrons. Therefore, LiPON not only effectively facilitates hole injection but also prevents electron tunneling to the hole transport layer, avoiding luminescence in non-emitting areas and thus improving the overall luminous efficiency of the quantum dot emitting diode.

[0044] In some implementations, a method such as... is also provided. Figure 1 The fabrication method of the quantum dot light-emitting diode with the positive structure shown is as follows: Figure 3 As shown, it includes the following steps:

[0045] S10. An anode substrate is provided, wherein a hole transport layer is provided on the anode substrate;

[0046] S20. An interface layer is prepared on the hole transport layer, wherein the interface layer material is LiPON.

[0047] S30. A quantum dot light-emitting layer is prepared in the interface layer;

[0048] S40. A cathode is prepared on the quantum dot light-emitting layer to obtain the quantum dot light-emitting diode.

[0049] In this 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 chemical vapor deposition, continuous ion layer adsorption and reaction, anodic oxidation, electrolytic deposition, and coprecipitation. The physical method includes, but is not limited to, physical coating or solution method. The solution method includes, but is not limited to, spin coating, printing, blade coating, dip coating, immersion coating, spraying, roller coating, casting, slot coating, and strip 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 plating, physical vapor deposition, atomic layer deposition, and pulsed laser deposition.

[0050] In some specific embodiments, an interface layer is prepared on the hole transport layer using a spin-coating method. This method specifically includes the following steps: dispersing LiPON in an organic solvent to obtain a LiPON solution; spin-coating the LiPON solution onto the surface of the hole transport layer; and thermally annealing at 100°C for 30 minutes to obtain the interface layer. In this embodiment, the organic solvent includes, but is not limited to, ethanol, methanol, butanol, acetone, isoacetone, nitrile, chlorobenzene, toluene, xylene, dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, and ethyl acetate. In this embodiment, the concentration of the LiPON solution is 1-2 wt%. Within this concentration range, the prepared interface layer can both reduce interfacial impedance and effectively improve the luminous performance of the quantum dot light-emitting diode.

[0051] In some embodiments, a method for fabricating an inverted quantum dot light-emitting diode is also provided, comprising the steps of: The present invention also provides a method for fabricating a quantum dot light-emitting diode with an inversion structure. Figure 2 The fabrication method of the inversion structure QLED shown is as follows: Figure 4 As shown, it includes the following steps:

[0052] S100. A cathode substrate is provided, on which a quantum dot light-emitting layer is formed;

[0053] S200. An interface layer is prepared on the surface of the quantum dot light-emitting layer, wherein the interface layer material is LiPON.

[0054] S300. A hole transport layer is prepared on the interface layer;

[0055] S400: An anode is prepared on the hole transport layer to obtain the quantum dot light-emitting diode.

[0056] In one embodiment of the present invention, the cathode substrate includes a substrate and a bottom electrode disposed on the substrate, the bottom electrode being a cathode; in another embodiment of the present invention, the cathode substrate may include a substrate, a bottom electrode stacked on the surface of the substrate, and an electron injection layer stacked on the surface of the substrate; in yet another embodiment of the present invention, the cathode substrate may include a substrate, a bottom electrode stacked on the surface of the substrate, an electron injection layer stacked on the surface of the substrate, and an electron transport layer stacked on the surface of the electron injection layer; in yet another embodiment of the present invention, the anode substrate may include a substrate, a bottom electrode stacked on the surface of the substrate, an electron injection layer stacked on the surface of the substrate, an electron transport layer stacked on the surface of the electron injection layer, and a hole blocking layer stacked on the surface of the electron transport layer.

[0057] The preparation methods for the above layers can be chemical or physical methods. Chemical methods include, but are not limited to, one or more of chemical vapor deposition, continuous ion layer adsorption and reaction, anodic oxidation, electrolytic deposition, and coprecipitation. Physical methods include, but are not limited to, physical coating or solution methods. Solution methods include, but are not limited to, spin coating, printing, blade coating, dip coating, immersion coating, spraying, roller coating, casting, slot coating, and strip coating. Physical coating methods include, but are not limited to, one or more of thermal evaporation coating, electron beam evaporation coating, magnetron sputtering, multi-arc ion plating, physical vapor deposition, atomic layer deposition, and pulsed laser deposition.

[0058] The following specific embodiments further illustrate the present invention's quantum dot light-emitting diode and its fabrication method:

[0059] Example 1

[0060] A method for fabricating a quantum dot light-emitting diode with a positive bottom-emitting structure includes the following steps:

[0061] Step S1: Deposit a hole injection layer on a transparent anode substrate, wherein the transparent anode is ITO, the hole injection layer material is WO3, the thickness of the transparent anode is 20nm, and the thickness of the hole injection layer is 60nm.

[0062] Step S2: Deposit a hole transport layer on the hole injection layer, wherein the hole transport layer material is PFB and the thickness of the hole transport layer is 60 nm;

[0063] Step S3: Deposit an interface layer on the hole transport layer. The interface layer material is LiPON, and the thickness of the interface layer is 100 nm.

[0064] Step S4: Deposit a quantum dot light-emitting layer on the interface layer, wherein the quantum dot light-emitting layer material is PbSe and the thickness of the quantum dot light-emitting layer is 50 nm;

[0065] Step S5: Deposit 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.

[0066] Step S6: Deposit a metal cathode on the electron transport layer. The cathode material is Ag, the cathode thickness is 100 nm, and the cathode reflects visible light at a rate of not less than 98%.

[0067] Example 2

[0068] A method for fabricating a quantum dot light-emitting diode with a positive top-emitting structure, comprising the following steps:

[0069] Step S1: Deposit a hole injection layer on a transparent anode substrate, wherein the transparent anode is FTO, the hole injection layer material is WO3, the thickness of the transparent anode is 20nm, and the thickness of the hole injection layer is 60nm.

[0070] Step S2: Deposit a hole transport layer on the hole injection layer, wherein the hole transport layer material is TCTA and the thickness of the hole transport layer is 60 nm;

[0071] Step S3: Deposit an interface layer on the hole transport layer. The interface layer material is LiPON, and the thickness of the interface layer is 100 nm.

[0072] Step S4: Deposit a quantum dot light-emitting layer on the interface layer, wherein the quantum dot light-emitting layer material is InP and the thickness of the quantum dot light-emitting layer is 50 nm;

[0073] Step S5: Deposit 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.

[0074] Step S6: Deposit a cathode on the electron transport layer. The cathode material is Ag, the cathode thickness is 100 nm, and the cathode transmittance of visible light is not less than 90%.

[0075] Example 3

[0076] A method for fabricating a quantum dot light-emitting diode with an inverted bottom-emitting structure, comprising the following steps:

[0077] Step S1: Deposit an Ag layer on the substrate by vapor deposition, wherein the thickness of the Ag layer is 5 nm;

[0078] Step S2: Deposit an electron transport layer on the Ag layer, wherein the electron transport layer material is SnO and the thickness of the electron transport layer is 50 nm;

[0079] Step S3: Deposit a quantum dot light-emitting layer on the electron transport layer, wherein the quantum dot light-emitting layer material is CdSe and the thickness of the quantum dot light-emitting layer is 50 nm;

[0080] Step S4: Deposit an interface layer on the quantum dot light-emitting layer. The material of the interface layer is LiPON, and the thickness of the interface layer is 80 nm.

[0081] Step S5: Deposit a hole transport layer on the interface layer, wherein the hole transport layer material is PVK and the thickness of the hole transport layer is 80 nm;

[0082] Step S6: Deposit a hole injection layer on the hole transport layer, wherein the hole injection layer material is PEDOT:PSS and the thickness of the hole injection layer is 60nm;

[0083] Step S7: Deposit an anode on the hole injection layer. The anode material is ITO, and the anode thickness is 120 nm. The anode reflects at least 98% of visible light.

[0084] Example 4

[0085] A method for fabricating a quantum dot light-emitting diode with an inverted top-emitting structure, comprising the following steps:

[0086] Step S1: Deposit an Ag layer on the substrate by vapor deposition, wherein the thickness of the Ag layer is 5 nm;

[0087] Step S2: Deposit an electron transport layer on the Ag layer, wherein the electron transport layer material is TiO and the thickness of the electron transport layer is 60 nm;

[0088] Step S3: Deposit a quantum dot light-emitting layer on the electron transport layer, wherein the quantum dot light-emitting layer material is CdTe and the thickness of the quantum dot light-emitting layer is 50 nm;

[0089] Step S4: Deposit an interface layer on the quantum dot light-emitting layer. The material of the interface layer is LiPON, and the thickness of the interface layer is 80 nm.

[0090] Step S5: Deposit a hole transport layer on the interface layer, wherein the hole transport layer material is PFB and the thickness of the hole transport layer is 80 nm;

[0091] Step S6: Deposit a hole injection layer on the hole transport layer. The hole injection layer material is MoO3, and the thickness of the hole injection layer is 60 nm.

[0092] Step S7: Deposit an anode on the hole injection layer. The anode material is ITO, and the thickness of the anode is 120 nm. The visible light transmittance of the anode is not less than 90%.

[0093] Comparative Example 1

[0094] A method for fabricating a quantum dot light-emitting diode with a positive bottom-emitting structure includes the following steps:

[0095] Step S1: Deposit a hole injection layer on a transparent anode substrate, wherein the transparent anode is ITO, the hole injection layer material is WO3, the thickness of the transparent anode is 20nm, and the thickness of the hole injection layer is 60nm.

[0096] Step S2: Deposit a hole transport layer on the hole injection layer, wherein the hole transport layer material is PFB and the thickness of the hole transport layer is 60 nm;

[0097] Step S3: Deposit a quantum dot luminescent layer on the hole transport layer, wherein the quantum dot luminescent layer material is PbSe and the thickness of the quantum dot luminescent layer is 50 nm;

[0098] Step S4: Deposit 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.

[0099] Step S5: Deposit a metal cathode on the electron transport layer. The cathode material is Ag, the cathode thickness is 100 nm, and the cathode reflects visible light at a rate of not less than 98%.

[0100] Comparative Example 2

[0101] A method for fabricating a quantum dot light-emitting diode with a positive top-emitting structure, comprising the following steps:

[0102] Step S1: Deposit a hole injection layer on a transparent anode substrate, wherein the transparent anode is FTO, the hole injection layer material is WO3, the thickness of the transparent anode is 20nm, and the thickness of the hole injection layer is 60nm.

[0103] Step S2: Deposit a hole transport layer on the hole injection layer, wherein the hole transport layer material is TCTA and the thickness of the hole transport layer is 60 nm;

[0104] Step S3: Deposit a quantum dot light-emitting layer on the hole transport layer, wherein the quantum dot light-emitting layer material is InP and the thickness of the quantum dot light-emitting layer is 50 nm;

[0105] Step S4: Deposit 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.

[0106] Step S5: Deposit a cathode on the electron transport layer. The cathode material is Ag, the cathode thickness is 100 nm, and the cathode transmittance of visible light is not less than 90%.

[0107] Comparative Example 3

[0108] A method for fabricating a quantum dot light-emitting diode with an inverted bottom-emitting structure, comprising the following steps:

[0109] Step S1: Deposit an Ag layer on the substrate by vapor deposition, wherein the thickness of the Ag layer is 5 nm;

[0110] Step S2: Deposit an electron transport layer on the Ag layer, wherein the electron transport layer material is SnO and the thickness of the electron transport layer is 50 nm;

[0111] Step S3: Deposit a quantum dot light-emitting layer on the electron transport layer, wherein the quantum dot light-emitting layer material is CdSe and the thickness of the quantum dot light-emitting layer is 50 nm;

[0112] Step S4: Deposit a hole transport layer on the quantum dot light-emitting layer, wherein the hole transport layer material is PVK and the thickness of the hole transport layer is 80 nm;

[0113] Step S5: Deposit a hole injection layer on the hole transport layer. The hole injection layer material is PEDOT:PSS, and the thickness of the hole injection layer is 60nm.

[0114] Step S6: Deposit an anode on the hole injection layer. The anode material is ITO, and the anode thickness is 120 nm. The anode reflects at least 98% of visible light.

[0115] Comparative Example 4

[0116] A method for fabricating a quantum dot light-emitting diode with an inverted top-emitting structure, comprising the following steps:

[0117] Step S1: Deposit an Ag layer on the substrate by vapor deposition, wherein the thickness of the Ag layer is 5 nm;

[0118] Step S2: Deposit an electron transport layer on the Ag layer, wherein the electron transport layer material is TiO and the thickness of the electron transport layer is 60 nm;

[0119] Step S3: Deposit a quantum dot light-emitting layer on the electron transport layer, wherein the quantum dot light-emitting layer material is CdTe and the thickness of the quantum dot light-emitting layer is 50 nm;

[0120] Step S4: Deposit a hole transport layer on the quantum dot light-emitting layer, wherein the hole transport layer material is PFB and the thickness of the hole transport layer is 80 nm;

[0121] Step S5: Deposit a hole injection layer on the hole transport layer, wherein the hole injection layer material is MoO3 and the thickness of the hole injection layer is 60 nm;

[0122] Step S6: Deposit an anode on the hole injection layer. The anode material is ITO, and the thickness of the anode is 120 nm. The visible light transmittance of the anode is not less than 90%.

[0123] 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:

[0124] Table 1 Performance test results of quantum dot light-emitting diodes

[0125]

[0126]

[0127] Comparing the data in Table 1, it can be seen that the only difference between Example 1 and Comparative Example 1 is the addition of an interface layer made of LiPON material between the hole transport layer and the quantum dot emitting layer. This increases the external quantum efficiency from 7.9% to 8.2% and the lifetime from 5.4h to 5.5h. Similarly, the only difference between Example 2 and Comparative Example 2 is the addition of an interface layer made of LiPON material between the hole transport layer and the quantum dot emitting layer. This increases the external quantum efficiency from 14.6% to 14.9% and the lifetime from 3.9h. The difference between Example 3 and Comparative Example 3 is only that an interface layer formed of LiPON material was added between the hole transport layer and the quantum dot light-emitting layer, which increased the external quantum efficiency from 8.3% to 8.5% and the lifetime from 5.9h to 6.1h. The difference between Example 4 and Comparative Example 4 is only that an interface layer formed of LiPON material was added between the hole transport layer and the quantum dot light-emitting layer, which increased the external quantum efficiency from 15.8% to 16.1% and the lifetime from 4.1h to 4.4h. From the above data, it can be seen that by providing an interface layer between the hole transport layer and the quantum dot light-emitting layer, the external quantum efficiency and lifetime of the quantum dot light-emitting diode can be effectively improved.

[0128] In summary, this invention optimizes quantum dot light-emitting diode devices by adding an interface layer to the hole transport layer and the quantum dot light-emitting layer, thereby reducing the hole injection barrier, improving hole injection, preventing hole accumulation at the interface, and effectively reducing the recombination of electrons tunneling into the hole transport layer in the non-quantum dot light-emitting region, thus improving device efficiency and lifetime. The interface layer can also effectively block the influence of water and oxygen on the organic hole injection and transport layer, improving device stability.

[0129] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

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 provided between the hole transport layer and the quantum dot emitting layer, and the interface layer material is LiPON; 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 any one of claims 1-2, 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.

4. The quantum dot light-emitting diode according to claim 3, characterized in that, The hole transport layer material is selected from TFB.

5. The quantum dot light-emitting diode according to any one of claims 1-2, 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.

6. The quantum dot light-emitting diode according to claim 5, 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。 7. 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.

8. A method for fabricating a quantum dot light-emitting diode, characterized in that, Including the following steps: An anode substrate is provided, on which a hole transport layer is formed; An interface layer is fabricated on the hole transport layer, and the interface layer material is LiPON. 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 light-emitting layer, and the interface layer material is LiPON; 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.

9. The method for fabricating a quantum dot light-emitting diode according to claim 8, characterized in that, The step of preparing the interface layer on the hole transport layer includes: The LiPON was dispersed in an organic solvent to prepare a LiPON solution; An interface layer is prepared on the surface of the hole transport layer, and the interface layer material is the LiPON. Alternatively, the step of preparing an interface layer on the surface of the quantum dot luminescent layer includes: The LiPON was dispersed in an organic solvent to prepare a LiPON solution; An interface layer is prepared on the surface of the quantum dot light-emitting layer, and the interface layer material is the LiPON.

10. The method for fabricating a quantum dot light-emitting diode according to claim 9, characterized in that, The concentration of the LiPON solution is 1-2 wt%.

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