Quantum dot light emitting diode and display device

Abstract

The present invention relates to a quantum dot light emitting diode and a display device. The quantum dot light emitting diode comprises a first electron transport layer, a second electron transport layer and a quantum dot light emitting layer which are stacked; the material of the first electron transport layer is an inorganic metal oxide; the material of the second electron transport layer is an inorganic metal oxide doped with a first element and a second element; the first element is a lanthanide element, and the second element is selected from one or more of Zr, Hf, Nb, Ge, Ta and B. The quantum dot light emitting diode has a relatively good device life and can effectively improve the service life of the display device.

Description

Technical Field

[0001] The present invention relates to the field of electronic display technology, and in particular to a quantum dot light emitting diode and a display device. Background Art

[0002] Due to the unique optical properties of quantum dots, such as the luminescent wavelength being continuously adjustable with size and composition, narrow luminescent spectrum, high fluorescence efficiency, and good stability, display devices based on quantum dot light-emitting diodes (QLEDs) have received extensive attention and research in the display field. At the same time, QLED displays also have many features such as foldability, rollability, fast response speed, large viewing angle, and high contrast, and are therefore expected to become the next generation of display technology.

[0003] After nearly 30 years of research, the performance of QLED has been greatly improved. For example, the EQE of red, green and blue QLEDs has reached more than 20%, close to the theoretical limit; the life of red QLED has also reached the commercial standard. However, the development of QLED also faces many problems, especially the device life. For example, the life of blue QLED is still very low and difficult to meet commercial needs. Summary of the invention

[0004] Based on this, it is necessary to provide a quantum dot light emitting diode and a display device, wherein the quantum dot light emitting diode has a better device life and can effectively improve the service life of the display device.

[0005] A quantum dot light-emitting diode comprises a first electron transport layer, a second electron transport layer and a quantum dot light-emitting layer which are stacked; a material forming the second electron transport layer is doped with a first element and a second element; the first element is a lanthanide element, and the second element is selected from one or more of Zr, Hf, Nb, Ge, Ta and B.

[0006] In some embodiments, the material forming the first electron transport layer is an inorganic metal oxide; and the material forming the second electron transport layer is an inorganic metal oxide doped with a first element and a second element.

[0007] In some embodiments, the first element is one or more of Pr, La and Gd.

[0008] In some embodiments, in the second electron transport layer, the concentration of the first element is 1 wt %-5 wt %, and the concentration of the second element is 1 wt %-20 wt %.

[0009] In some embodiments, the inorganic metal oxide in the first electron transport layer is the same as or different from the inorganic metal oxide in the second electron transport layer, and each is independently selected from one or more of ZnO, ZnMgO and ZnAlO.

[0010] In some embodiments, the thickness ratio of the first electron transport layer to the second electron transport layer is 1:(1-4).

[0011] In some embodiments, the total thickness of the first electron transport layer and the second electron transport layer is 20 nm-200 nm.

[0012] In some embodiments, the first electron transport layer and the second electron transport layer are prepared by magnetron sputtering.

[0013] In some embodiments, the quantum dot material in the quantum dot light-emitting layer is one or more of CdSe / ZnSe, CdSe / CdS, CdSe / CdS / ZnS, ZnCdSeS, ZnCdSeS / ZnS, ZnCdS / ZnS and ZnSe / ZnS.

[0014] In some embodiments, the quantum dot light-emitting diode further comprises an anode, a cathode, a hole transport layer and a hole injection layer, the first electron transport layer is close to the cathode, the quantum dot light-emitting layer is close to the anode, the hole transport layer is arranged between the anode and the quantum dot light-emitting layer, and the hole injection layer is arranged between the anode and the hole transport layer;

[0015] The material of the hole transport layer is one or more of CDBP, mCBP, CBP, mCP, TCTA, TAPC and NPB; the material of the hole injection is one or more of HAT-CN, F4-TCNQ, MoO3, V2O5, WO3 and ReO3.

[0016] A display device comprises the above-mentioned quantum dot light emitting diode.

[0017] The above-mentioned quantum dot light-emitting diode is formed by stacking a first electron transport layer, a second electron transport layer and a quantum dot light-emitting layer, and doping the second electron transport layer with a first element and a second element, wherein the first element is a lanthanide element, and the second element is one or more of Zr, Hf, Nb, Ge, Ta and B. Under the synergistic effect of the above-mentioned specific first element and second element, the number of electrons accumulated in the electron transport layer can be effectively reduced, while reducing the fluorescence quenching of the quantum dot light-emitting layer by the electron transport layer, thereby achieving the purpose of improving the efficiency and device life of the QLED. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic diagram of a quantum dot electroluminescent device according to one embodiment of the present invention;

[0019] Figure 2 EQE-J curves of Example 1, Comparative Example 1 and Comparative Example 2;

[0020] Figure 3 The QLED lifespan curves of Example 1, Comparative Example 1 and Comparative Example 2 are shown. DETAILED DESCRIPTION

[0021] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively below, and preferred embodiments of the present invention are provided. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0023] See also Figure 1 In one embodiment of the present invention, a quantum dot light emitting diode (QLED) 10 is provided, comprising a first electron transport layer 121, a second electron transport layer 122 and a quantum dot light emitting layer 110 which are stacked; a material forming the second electron transport layer 121 is doped with a first element and a second element; the first element is a lanthanide element, and the second element is selected from one or more of Zr, Hf, Nb, Ge, Ta and B.

[0024] The technicians of the present invention found in the research that: in the blue light and green light QLED, there is an obvious electron barrier between the electron transport layer / quantum dot light-emitting layer, which causes a considerable part of the electrons to accumulate in the electron transport layer. These electrons accelerate the failure of the electron transport layer because they cannot be released in time, and then accelerate the life decay of the QLED. Therefore, the technicians of the present invention stacked the first electron transport layer 121, the second electron transport layer 122 and the quantum dot light-emitting layer 110, and doped the first element and the second element in the second electron transport layer 122, wherein the first element is a lanthanide element, and the second element is one or more of Zr, Hf, Nb, Ge, Ta and B. Under the synergistic effect of the above-mentioned specific first element and second element, the number of electrons accumulated in the electron transport layer can be effectively reduced, while reducing the fluorescence quenching of the quantum dot light-emitting layer by the electron transport layer, thereby achieving the purpose of improving the efficiency and device life of the QLED.

[0025] It is understandable that the material forming the second electron transport layer 121 and the material forming the second electron transport layer 122 can be an electron transport material acceptable in the art, and are not particularly limited here, and should be understood to be within the scope of protection of the present invention. In addition, in addition to the first element and the second element of the present invention, the second electron transport layer 122 can also be doped with other elements, as long as they do not conflict with the purpose of the present invention.

[0026] In some embodiments, the material forming the first electron transport layer 121 is an inorganic metal oxide; the material forming the second electron transport layer 122 is an inorganic metal oxide doped with a first element and a second element. By making the first electron transport layer 121 and the second electron transport layer 122 use inorganic metal oxides, it is convenient to use magnetron sputtering to prepare them, avoid the disadvantages caused by inkjet printing technology, and reduce the preparation cost.

[0027] In some embodiments, the first element is one or more of Pr, La and Gd. The first element is a lanthanide element, which can introduce an electron acceptor energy level near the bottom of the conduction band of the band gap of the electron transport material, thereby capturing the accumulated electrons, and then combining with the oxygen vacancies of the electron transport material, the two react to make the captured electrons undergo rapid non-radiative recombination, thereby greatly reducing the number of accumulated electrons in the electron transport layer, which is beneficial to improving the stability of the electron transport layer, and then improving the life of the QLED, among which Pr, La and Gd have particularly significant effects.

[0028] In some embodiments, the second element is an element that can reduce oxygen vacancies to further reduce the fluorescence quenching of the quantum dot light-emitting layer by the electron transport layer, thereby improving the efficiency and device life of the QLED.

[0029] In some embodiments, the first element is Pr and the second element is Zr; in some embodiments, the first element is Pr and the second element is Hf; in some embodiments, the first element is Pr and the second element is Nb; in some embodiments, the first element is Pr and the second element is Ge. In some embodiments, the first element is Pr and the second element is B. In some embodiments, the first element is Pr and the second element is Nb and Zr.

[0030] In some embodiments, in the second electron transport layer 122, the concentration of the first element is 1wt%-5wt%; further, the concentration of the first element is 2wt%-4wt%; further, the concentration of the first element is 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3.0wt%, 3.5wt%, 4.0wt%, 4.5wt% or 5wt%. By controlling the doping amount of the first element within the above range, the comprehensive effect of the device can be effectively guaranteed, avoiding poor effects caused by too low doping amount and the introduction of a large number of defects caused by too high doping amount, thereby weakening the function of the electron transport layer in transmitting electrons.

[0031] In some embodiments, in the second electron transport layer 122, the concentration of the second element is 1wt%-20wt%; further, the concentration of the second element is 5wt%-15wt%; further, the concentration of the second element is 8wt%-12wt%; further, the concentration of the second element is 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3.0wt%, 3.5wt%, 4.0wt%, 4.5wt%, 5wt%, 5. %, 5wt%, 6wt%, 6.5wt%, 7wt%, 7.5wt%, 8wt%, 8.5wt%, 9wt%, 9.5wt%, 10wt%, 10.5wt%, 11wt%, 11.5wt%, 12wt%, 12.5wt%, 13wt%, 13.5wt%, 14wt%, 14.5wt%, 15wt%, 16wt%, 17wt%, 18wt%, 19wt% or 20wt%. By controlling the doping amount of the second element within the above range, the comprehensive effect of the device can be effectively guaranteed, avoiding the poor effect caused by too low doping amount and the scattering of the transmitted electrons caused by too high doping amount, thereby affecting the transmission performance of the electron transport layer.

[0032] In some embodiments, in the second electron transport layer 122, the mass ratio of the first element to the second element is 1:0.1-1:10; in some embodiments, in the second electron transport layer 122, the mass ratio of the first element to the second element is less than 1; further, the mass ratio of the first element to the second element is 1:1-1:5; further, the mass ratio of the first element to the second element is 1:2-1:4, so as to obtain better synergistic effect.

[0033] It is understandable that the inorganic metal oxides in the first electron transport layer 121 and the second electron transport layer 122 may be the same or different, and conventional inorganic metal oxides that can be used to form electron transport layers in the art may be selected, and are not particularly limited here, and should be understood to be within the scope of protection of the present invention. In some embodiments, the inorganic metal oxide is an inorganic metal oxide containing Zn element; further, the inorganic metal oxide is selected from: one or more of ZnO, ZnMgO and ZnAlO.

[0034] In some embodiments, the thickness ratio of the first electron transport layer 121 to the second electron transport layer 122 is 1:(1-4); the thickness ratio of the first electron transport layer 121 to the second electron transport layer 122 is 1:(1.2-1.8); further, the thickness ratio of the first electron transport layer 121 to the second electron transport layer 122 is 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7 or 1:1.8. Since the first electron transport layer has the function of electron injection and the second electron transport layer plays a more important role in electron transmission, therefore, setting the first electron transport layer thinner and the second electron transport layer relatively thicker can effectively improve the efficiency and life of the QLED.

[0035] In some embodiments, the total thickness of the first electron transport layer 121 and the second electron transport layer 122 is 20-200 nm; further, the total thickness of the first electron transport layer 121 and the second electron transport layer 122 is 30-100 nm; further, the total thickness of the first electron transport layer 121 and the second electron transport layer 122 is 35-55 nm. By controlling the total thickness of the first electron transport layer 121 and the second electron transport layer 122 within the above range, the light emitting effect of the QLED can be effectively improved.

[0036] In some embodiments, the thickness of the first electron transport layer 121 is 20-50nm; further, the thickness of the first electron transport layer 121 is 20-30nm; further, the thickness of the first electron transport layer 121 is 20nm, 21nm, 22nm, 23nm, 24nm or 25nm. In some embodiments, the thickness of the second electron transport layer 122 is greater than or equal to the thickness of the first electron transport layer 121; further, the thickness of the second electron transport layer 122 is 25-50nm; further, the thickness of the second electron transport layer 122 is 28-32nm; further, the thickness of the second electron transport layer 122 is 16nm, 27nm, 28nm, 29nm, 30nm, 31nm or 32nm, to obtain a better combination effect.

[0037] In some embodiments, the first electron transport layer 121 and the second electron transport layer 122 are prepared by magnetron sputtering.

[0038] In some embodiments, the second electron transport layer 122 is in contact with the quantum dot light-emitting layer 110; further, the quantum dot material in the quantum dot light-emitting layer 110 is a green light or blue light quantum dot light-emitting material; further, the quantum dot material is one or more of CdSe / ZnSe, CdSe / CdS, CdSe / CdS / ZnS, ZnCdSeS, ZnCdSeS / ZnS, ZnCdS / ZnS and ZnSe / ZnS; further, the thickness of the quantum dot light-emitting layer 110 is 10-80nm; further, the thickness of the quantum dot light-emitting layer 110 is 10-40nm; further, the thickness of the quantum dot light-emitting layer 110 is 25nm, 28nm, 30nm, 32nm or 35nm.

[0039] In some embodiments, the quantum dot light-emitting diode 10 is an inverted quantum dot light-emitting diode. The bottom electrode and electron injection / transport layer of the inverted structure QLED can be prepared by magnetron sputtering, which is mature, stable, and controllable, and is very conducive to the preparation of large-size QLED display screens.

[0040] In some embodiments, the quantum dot light-emitting diode 10 further includes an anode 150 and a cathode 160, the quantum dot light-emitting layer 110 is disposed between the anode 150 and the cathode 160, the first electron transport layer 121 and the second electron transport layer 122 are disposed between the cathode 160 and the quantum dot light-emitting layer 110, and the first electron transport layer 121 is close to the cathode 160, and the second electron transport layer 122 is close to the quantum dot light-emitting layer 110. In some embodiments, transparent conductive ITO is used as the cathode and Al is used as the anode. In some embodiments, the thickness of the cathode 160 is 40-80nm; further, the thickness of the cathode 160 is 45-55nm; further, the thickness of the cathode 160 is 50nm; in some embodiments, the thickness of the anode 150 is 80-120nm; further, the thickness of the anode 150 is 90-110nm; further, the thickness of the anode 150 is 100nm.

[0041] In some embodiments, the quantum electroluminescent device 10 further includes a substrate 170 , and the cathode 160 is deposited on the substrate 170 .

[0042] In some embodiments, the quantum dot electroluminescent device 10 further includes a hole transport layer 130 disposed between the anode 150 and the quantum dot light-emitting layer 110, and a hole injection layer 140 disposed between the anode 150 and the hole transport layer 130; further, the material of the hole transport layer 130 is CDBP (4,4'-bis(9H-carbazole-9-yl)-2,2'-dimethylbiphenyl), mCBP (3,3'-bis(N-carbazole)-1,1'-biphenyl), CBP (4,4'-di(9-carbazole)biphenyl), mCP (1,3-dicarbazole-9-ylbenzene), TCTA (4,4',4"-tri(carbazole-9-yl)triphenylamine), TAPC (4,4'-cyclohexylbis[N,N-di(4-methylphenyl)aniline]) and NPB (N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'- Further, the material of the hole injection layer 140 is one or more of HAT-CN (2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene), F4-TCNQ (2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone), MoO3, V2O5, WO3 and ReO3; further, the thickness of the hole transport layer 130 is 15-50nm; further, the thickness of the hole transport layer 130 is 25-35nm; further, the thickness of the hole transport layer 130 is 30nm; further, the thickness of the hole injection layer 140 is 5-20nm; further, the thickness of the hole injection layer 140 is 8-12nm; further, the thickness of the hole injection layer 140 is 10nm.

[0043] An embodiment of the present invention provides a method for preparing the above quantum dot light-emitting diode, comprising the following steps:

[0044] S101: providing a cathode;

[0045] S102: depositing a first electron transport layer on the cathode;

[0046] S103: depositing a second electron transport layer on the first electron transport layer;

[0047] S104: depositing a quantum dot light-emitting layer on the second electron transport layer;

[0048] S105: depositing a hole transport layer on the quantum dot light-emitting layer;

[0049] S106: depositing a hole injection layer on the hole transport layer;

[0050] S107: depositing an anode on the hole injection layer.

[0051] In some embodiments, the first electron transport layer is prepared by magnetron sputtering in step S102; in some embodiments, the second electron transport layer is prepared by magnetron sputtering in step S103; in some embodiments, the quantum dot light-emitting layer is deposited by solution method in step S104; in some embodiments, the hole transport layer is deposited by evaporation in step S105; in some embodiments, the hole injection layer is deposited by evaporation in step S106; in some embodiments, the anode is deposited by evaporation in step S107. By selecting a suitable method according to the characteristics of each layer, the quality of each layer can be effectively improved, and the operation complexity and production cost can be reduced. In particular, by using magnetron sputtering to prepare the first electron transport layer and the second electron transport layer, compared with the inkjet printing method, the problem of poor compatibility between inkjet printing technology and nanoparticles, poor stability and repeatability, and thus low film quality can be effectively overcome. In addition, the second electron transport layer can be prepared by magnetron sputtering, and the type and content of the first element and the second element can be adjusted according to the needs, which can achieve the purpose of improving the service life of the device while reducing the operation complexity and production cost.

[0052] An embodiment of the present invention further provides a display device including the quantum dot light emitting diode. By using the quantum dot light emitting diode with a long device life, the service life of the display device can be effectively improved to meet the needs of modern display.

[0053] The present invention is described below with reference to specific embodiments. It should be noted that the following embodiments are merely illustrative and should not be construed as limiting the present invention.

[0054] Embodiment 1:

[0055] (1) Using transparent conductive film ITO as cathode with a thickness of 50nm;

[0056] (2) ZnO was deposited on ITO by magnetron sputtering as electron transport layer I with a thickness of 20 nm;

[0057] (3) ZnPr (3%) Zr (10%) O was deposited on the electron transport layer I by magnetron sputtering to form the electron transport layer II with a thickness of 30 nm;

[0058] (4) Depositing blue ZnCdS / ZnS as a quantum dot light-emitting layer on the electron transport layer II by solution method with a thickness of 15 nm;

[0059] (5) TCTA was deposited on the quantum dot light-emitting layer by evaporation method as a hole transport layer with a thickness of 30 nm;

[0060] (6) Depositing TCTA:MoO3 (10%) as a hole injection layer on the hole transport layer by evaporation with a thickness of 10 nm;

[0061] (7) Al was deposited on the hole injection layer by evaporation to a thickness of 100 nm as an anode.

[0062] Embodiment 2:

[0063] (1) Using transparent conductive film ITO as cathode with a thickness of 50nm;

[0064] (2) ZnO was deposited on ITO by magnetron sputtering as electron transport layer I with a thickness of 20 nm;

[0065] (3) ZnPr (3%) Hf (10%) O was deposited on the electron transport layer I by magnetron sputtering to form the electron transport layer II with a thickness of 30 nm;

[0066] (4) Depositing blue ZnCdS / ZnS as a quantum dot light-emitting layer on the electron transport layer II by solution method with a thickness of 15 nm;

[0067] (5) TCTA was deposited on the quantum dot light-emitting layer by evaporation method as a hole transport layer with a thickness of 30 nm;

[0068] (6) Depositing TCTA:MoO3 (10%) as a hole injection layer on the hole transport layer by evaporation with a thickness of 10 nm;

[0069] (7) Al was deposited on the hole injection layer by evaporation to a thickness of 100 nm as an anode.

[0070] Embodiment 3:

[0071] (1) Using transparent conductive film ITO as cathode with a thickness of 50nm;

[0072] (2) ZnO was deposited on ITO by magnetron sputtering as electron transport layer I with a thickness of 20 nm;

[0073] (3) ZnPr (3%) Nb (10%) O was deposited on the electron transport layer I by magnetron sputtering to form the electron transport layer II with a thickness of 30 nm;

[0074] (4) Depositing blue ZnCdS / ZnS as a quantum dot light-emitting layer on the electron transport layer II by solution method with a thickness of 15 nm;

[0075] (5) TCTA was deposited on the quantum dot light-emitting layer by evaporation method as a hole transport layer with a thickness of 30 nm;

[0076] (6) Depositing TCTA:MoO3 (10%) as a hole injection layer on the hole transport layer by evaporation with a thickness of 10 nm;

[0077] (7) Al was deposited on the hole injection layer by evaporation to a thickness of 100 nm as an anode.

[0078] Embodiment 4:

[0079] (1) Using transparent conductive film ITO as cathode with a thickness of 50nm;

[0080] (2) ZnO was deposited on ITO by magnetron sputtering as electron transport layer I with a thickness of 20 nm;

[0081] (3) ZnPr(3%)Ge(10%)O was deposited on the electron transport layer I by magnetron sputtering to form the electron transport layer II with a thickness of 30 nm;

[0082] (4) Depositing blue ZnCdS / ZnS as a quantum dot light-emitting layer on the electron transport layer II by solution method with a thickness of 15 nm;

[0083] (5) TCTA was deposited on the quantum dot light-emitting layer by evaporation method as a hole transport layer with a thickness of 30 nm;

[0084] (6) Depositing TCTA:MoO3 (10%) as a hole injection layer on the hole transport layer by evaporation with a thickness of 10 nm;

[0085] (7) Al was deposited on the hole injection layer by evaporation to a thickness of 100 nm as an anode.

[0086] Example 5

[0087] (1) Using transparent conductive film ITO as cathode with a thickness of 50nm;

[0088] (2) ZnO was deposited on ITO by magnetron sputtering as electron transport layer I with a thickness of 20 nm;

[0089] (3) ZnPr (3%) B (10%) O was deposited on the electron transport layer I by magnetron sputtering to form the electron transport layer II with a thickness of 30 nm;

[0090] (4) Depositing blue ZnCdS / ZnS as a quantum dot light-emitting layer on the electron transport layer II by solution method with a thickness of 15 nm;

[0091] (5) TCTA was deposited on the quantum dot light-emitting layer by evaporation method as a hole transport layer with a thickness of 30 nm;

[0092] (6) Depositing TCTA:MoO3 (10%) as a hole injection layer on the hole transport layer by evaporation with a thickness of 10 nm;

[0093] (7) Al was deposited on the hole injection layer by evaporation to a thickness of 100 nm as an anode.

[0094] Example 6

[0095] (1) Using transparent conductive film ITO as cathode with a thickness of 50nm;

[0096] (2) ZnO was deposited on ITO by magnetron sputtering as electron transport layer I with a thickness of 20 nm;

[0097] (3) ZnPr (3%) Nb (5%) Zr (5%) O was deposited on the electron transport layer I by magnetron sputtering to form the electron transport layer II with a thickness of 30 nm;

[0098] (4) Depositing blue ZnCdS / ZnS as a quantum dot light-emitting layer on the electron transport layer II by solution method with a thickness of 15 nm;

[0099] (5) TCTA was deposited on the quantum dot light-emitting layer by evaporation method as a hole transport layer with a thickness of 30 nm;

[0100] (6) Depositing TCTA:MoO3 (10%) as a hole injection layer on the hole transport layer by evaporation with a thickness of 10 nm;

[0101] (7) Al was deposited on the hole injection layer by evaporation to a thickness of 100 nm as an anode.

[0102] Example 7

[0103] (1) Using transparent conductive film ITO as cathode with a thickness of 50nm;

[0104] (2) ZnO was deposited on ITO by magnetron sputtering as electron transport layer I with a thickness of 20 nm;

[0105] (3) ZnPr (3%) Zr (1%) O was deposited on the electron transport layer I by magnetron sputtering to form the electron transport layer II with a thickness of 30 nm;

[0106] (4) Depositing blue ZnCdS / ZnS as a quantum dot light-emitting layer on the electron transport layer II by solution method with a thickness of 15 nm;

[0107] (5) TCTA was deposited on the quantum dot light-emitting layer by evaporation method as a hole transport layer with a thickness of 30 nm;

[0108] (6) Depositing TCTA:MoO3 (10%) as a hole injection layer on the hole transport layer by evaporation with a thickness of 10 nm;

[0109] (7) Al was deposited on the hole injection layer by evaporation to a thickness of 100 nm as an anode.

[0110] Example 8

[0111] (1) Using transparent conductive film ITO as cathode with a thickness of 50nm;

[0112] (2) ZnO was deposited on ITO by magnetron sputtering as electron transport layer I with a thickness of 20 nm;

[0113] (3) ZnPr (3%) Zr (20%) O was deposited on the electron transport layer I by magnetron sputtering to form the electron transport layer II with a thickness of 30 nm;

[0114] (4) Depositing blue ZnCdS / ZnS as a quantum dot light-emitting layer on the electron transport layer II by solution method with a thickness of 15 nm;

[0115] (5) TCTA was deposited on the quantum dot light-emitting layer by evaporation method as a hole transport layer with a thickness of 30 nm;

[0116] (6) Depositing TCTA:MoO3 (10%) as a hole injection layer on the hole transport layer by evaporation with a thickness of 10 nm;

[0117] (7) Al was deposited on the hole injection layer by evaporation to a thickness of 100 nm as an anode.

[0118] Comparative Example 1

[0119] (1) Using transparent conductive film ITO as cathode with a thickness of 50nm;

[0120] (2) ZnO was deposited on ITO by magnetron sputtering as an electron injection and transport layer with a thickness of 50 nm;

[0121] (3) Depositing blue ZnCdS / ZnS as a quantum dot light-emitting layer on the electron transport layer by solution method with a thickness of 15 nm;

[0122] (4) TCTA was deposited on the quantum dot light-emitting layer by evaporation method as a hole transport layer with a thickness of 30 nm;

[0123] (5) TCTA:MoO3 (10%) was deposited on the hole transport layer by evaporation method as a hole injection layer with a thickness of 10 nm;

[0124] (6) Al was deposited on the hole injection layer by evaporation to a thickness of 100 nm as an anode.

[0125] Comparative Example 2

[0126] (1) Using transparent conductive film ITO as cathode with a thickness of 50nm;

[0127] (2) ZnO was deposited on ITO by magnetron sputtering as electron transport layer I with a thickness of 20 nm;

[0128] (3) ZnZr (10%) O was deposited on the electron transport layer I by magnetron sputtering to form the electron transport layer II with a thickness of 30 nm;

[0129] (4) Depositing blue ZnCdS / ZnS as a quantum dot light-emitting layer on the electron transport layer II by solution method with a thickness of 15 nm;

[0130] (5) TCTA was deposited on the quantum dot light-emitting layer by evaporation method as a hole transport layer with a thickness of 30 nm;

[0131] (6) Depositing TCTA:MoO3 (10%) as a hole injection layer on the hole transport layer by evaporation with a thickness of 10 nm;

[0132] (7) Al was deposited on the hole injection layer by evaporation to a thickness of 100 nm as an anode.

[0133] Performance Testing

[0134] The QLEDs of Examples 1 to 8, Comparative Example 1, and Comparative Example 2 were subjected to performance tests, and the test results of the device lifespan are shown in Table 1:

[0135] Table 1

[0136] Example <![CDATA[T 95 @1000nits(h)]]> Example 1 24.0 Example 2 22.7 Example 3 19.6 Example 4 19.2 Example 5 17.3 Example 6 22.5 Example 7 16.8 Example 8 13.2 Comparative Example 1 2.3 Comparative Example 2 9.0

[0137] It can be seen from Table 1 that the QLEDs of Examples 1 to 8 all have relatively good device lifespans, which indicates that the QLEDs of the present invention have excellent device lifespans.

[0138] In addition, by comparing Example 1 with Comparative Examples 1 and 2, Comparative Example 1 does not contain a second electron transport layer, and the second electron transport layer of Comparative Example 2 contains only the second element. As can be seen from Table 1, the device life of Example 1 is significantly better than that of Comparative Examples 1 and 2. Figure 2 EQE-J curves of Example 1, Comparative Example 1 and Comparative Example 2 are shown in FIG. Figure 2It can be seen that compared with Comparative Example 1, the EQE of Comparative Example 2 and Example 1 have been greatly improved, and the improvement of EQE in Example 1 is greater than that in Comparative Example 2. This shows that after the Zr element doped the electron transport layer, the efficiency of the QLED was effectively improved, and the combined effect of the Zr and Pr elements after doping was significantly better than that of the Zr element, and there was a synergistic effect between the first element and the second element. In addition, compared with Comparative Examples 1 and 2, the efficiency roll-off of Example 1 is smoother. This shows that after the electron transport layer is doped with lanthanide elements, the number of electrons accumulated in the electron transport layer is greatly reduced, thereby alleviating the efficiency roll-off problem caused by electron annihilation.

[0139] in addition, Figure 3 The QLED lifespan curves of Example 1 and Comparative Example 1-Comparative Example 2 are shown in FIG. Figure 3 It can be seen that compared with Comparative Example 1, the lifespans of Comparative Example 2 and Example 1 are significantly improved, and compared with Comparative Example 2, the lifespan of Example 1 is increased by more than 2.5 times, indicating that the first element and the second element interact with each other after being doped in the electron transport layer, and the accumulated electrons in the electron transport layer are released, thereby greatly improving the lifespan of the QLED.

[0140] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0141] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A quantum dot light emitting diode, characterized in that: The invention comprises a first electron transport layer, a second electron transport layer and a quantum dot light-emitting layer which are stacked; a material forming the second electron transport layer is doped with a first element and a second element; in the second electron transport layer, the concentration of the first element is 1wt%-5wt%, and the concentration of the second element is 1wt%-20wt%; the first element is a lanthanide element, and the second element is selected from one or more of Zr, Hf, Nb, Ge, Ta and B; The material forming the first electron transport layer is an inorganic metal oxide; the material forming the second electron transport layer is an inorganic metal oxide doped with the first element and the second element.

2. The quantum dot light emitting diode according to claim 1, characterized in that: The first element is one or more of Pr, La and Gd.

3. The quantum dot light emitting diode according to claim 1, characterized in that: In the second electron transport layer, the concentration of the first element is 2wt%-4wt%, and the concentration of the second element is 5wt%-15wt%.

4. The quantum dot light emitting diode according to claim 1, characterized in that: The inorganic metal oxide in the first electron transport layer is the same as or different from the inorganic metal oxide in the second electron transport layer, and each is independently selected from one or more of ZnO, ZnMgO and ZnAlO.

5. The quantum dot light emitting diode according to claim 1, characterized in that: The thickness ratio of the first electron transport layer to the second electron transport layer is 1:(1-4).

6. The quantum dot light-emitting diode according to any one of claims 1 to 5, characterized in that: The total thickness of the first electron transport layer and the second electron transport layer is 20nm-200nm; and / or The first electron transport layer and the second electron transport layer are prepared by magnetron sputtering.

7. The quantum dot light emitting diode according to any one of claims 1 to 5, characterized in that: The quantum dot material in the quantum dot light-emitting layer is one or more of CdSe / ZnSe, CdSe / CdS, CdSe / CdS / ZnS, ZnCdSeS, ZnCdSeS / ZnS, ZnCdS / ZnS and ZnSe / ZnS.

8. The quantum dot light emitting diode according to any one of claims 1 to 5, characterized in that: It also includes an anode, a cathode, a hole transport layer and a hole injection layer, wherein the first electron transport layer is close to the cathode, the quantum dot light-emitting layer is close to the anode, the hole transport layer is arranged between the anode and the quantum dot light-emitting layer, and the hole injection layer is arranged between the anode and the hole transport layer; The material of the hole transport layer is one or more of CDBP, mCBP, CBP, mCP, TCTA, TAPC and NPB; The material of the hole injection layer is one or more of HAT-CN, F4-TCNQ, MoO3, V2O5, WO3 and ReO3.

9. A display device, characterized in that: A quantum dot light emitting diode comprising any one of claims 1 to 8.

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