WO2022233145A1

WO2022233145A1 - Quantum dot electroluminescent device

Info

Publication number: WO2022233145A1
Application number: PCT/CN2021/142090
Authority: WO
Inventors: 侯文军; 严依然; 徐威; 杨一行
Original assignee: Tcl科技集团股份有限公司
Priority date: 2021-05-07
Filing date: 2021-12-28
Publication date: 2022-11-10
Also published as: CN115312669A

Abstract

Disclosed in the present invention is a quantum dot electroluminescent device. The pure electronic device corresponding to the quantum dot electroluminescent device is denoted as an EOD device, and the pure hole device corresponding to the quantum dot electroluminescent device is denoted as an HOD device; at the same current density, a voltage corresponding to the EOD device is denoted as V_EOD, and a voltage corresponding to the HOD device is denoted as V_HOD, wherein at the current density of 5 mA/cm ² or more, a hole function layer and an electron functional layer of the quantum dot electroluminescent device are configured to be 0.5 V≤V_HOD-V_EOD≤10 V. It is found through researches and tests that when the hole function layer and the electron function layer of the quantum dot electroluminescent device are configured to be 0.5 V≤V_HOD-V_EOD≤10 V at the same current density, the quantum dot electroluminescent device has a long service life.

Description

A quantum dot electroluminescent device

priority

This disclosure claims the priority of the Chinese patent application with the application date of May 7, 2021, the application number is "202110498771.8", and the application name is "a quantum dot electroluminescent device", the entire content of which is approved by References are incorporated in this disclosure.

technical field

The present disclosure relates to the technical field of quantum dot electroluminescence devices, and in particular, to a quantum dot electroluminescence device.

Background technique

Due to the unique optoelectronic properties of quantum dots, such as continuous tunability of emission wavelength with size and composition, narrow emission spectrum, high fluorescence efficiency, and good stability, quantum dot-based electroluminescent diodes (QLEDs) have received extensive attention in the display field. and research. In addition, QLED display also has many advantages that cannot be achieved by LCD, such as large viewing angle, high contrast ratio, fast response speed, and flexibility, so it is expected to become the next-generation display technology.

After more than 20 years of development, quantum dot materials have been developed by leaps and bounds, and the external quantum efficiency of red, green and blue QLED devices has been greatly improved, especially in CdSe-based devices. The improved efficiency of QLED devices highlights its future prospects. So far, there have been many studies on structure and material optimization for QLED devices, including the selection of core-shell quantum dot materials and the alloying of core-shell interfaces to reduce surface defects and suppress Auger processes, and the selection of surface ligands for core-shell quantum dots. Design and optimize the design of charge transport layers, etc., to improve their external quantum efficiency and prolong their lifetime.

The research on QLED devices all use quantum dots with core-shell structure, which have been shown to have excellent performance. The shell layer can well protect the quantum dots, reduce surface defects and improve the quantum yield, and effectively suppress nonradiative transitions; the shell layer has also been shown to reduce the Foster energy transfer process in quantum dot films by increasing the thickness of the shell layer. dipole resonance, thereby improving the quantum yield of quantum dot films.

The QLED device needs to inject electrons and holes when it works. The simplest QLED device consists of a cathode, an electron transport layer, a quantum dot light-emitting layer, a hole transport layer and an anode. In the QLED device, the quantum dot film is sandwiched between the charge transport layer. When a forward bias voltage is applied to both ends of the QLED device, electrons and holes enter the quantum dot light-emitting layer through the electron transport layer and the hole transport layer, respectively, and enter the quantum dot light-emitting layer through the electron transport layer and the hole transport layer, respectively. The quantum dot light-emitting layer performs compound light emission. The charge transport layer not only affects the charge injection efficiency, but also imposes requirements on the QLED process and affects the external quantum efficiency. The electron-hole injection imbalance not only reduces the ability of the injected charge to convert into excitons, but also causes the charge to accumulate in the QLED device, increasing the non-radiative transition of charged excitons, resulting in lower efficiency and reduced lifetime. Efficient exciton formation in QLEDs requires charge transport layers with good blocking properties for efficient charge confinement within the QD layer and reasonable modulation of electron and hole injection for charge balance.

At present, the quantum efficiencies of quantum dot devices with three primary colors of red, green and blue are all greater than 20%, and the efficiency of quantum dot devices has reached the level of commercial application. However, there is still a certain gap between the corresponding device lifetime and OLED, especially for blue quantum dot devices.

Therefore, the existing technology still needs to be improved and developed.

SUMMARY OF THE INVENTION

In view of the above-mentioned deficiencies of the prior art, the present disclosure proposes a quantum dot electroluminescence device, aiming at solving the problem of low lifetime of the existing quantum dot electroluminescence device.

The technical solutions of the present disclosure are as follows:

A quantum dot electroluminescence device, wherein the pure electronic device corresponding to the quantum dot electroluminescence device is denoted as an EOD device, and the pure hole device corresponding to the quantum dot electroluminescence device is denoted as a HOD device;

Under the same current density, the voltage corresponding to the EOD device is denoted as V _EOD , and the voltage corresponding to the HOD device is denoted as V _HOD ;

Wherein, under the current density of 5 mA/cm ² or more, the hole functional layer and the electron functional layer of the quantum dot electroluminescent device are configured to be 0.5V≤V _HOD -V _EOD ≤10V.

Optionally, the current density is 5-50 mA/cm ² .

Optionally, the current density is 5-10 mA/cm ² .

Optionally, 3V≦V _HOD −V _EOD ≦5V.

Optionally, the lifetime T95 of the quantum dot electroluminescent device is greater than or equal to 10000h@1000nits.

Optionally, the hole functional layer includes a hole transport layer, and the electron functional layer is an electron transport layer;

in,

The hole transport layer material is TFB, the hole transport layer thickness is 15-25nm, the electron transport layer material is metal oxide Zn _x Mg _y O, wherein x is 0.90-0.97, y is 0.03-0.1 , the thickness of the electron transport layer is 20-50 nm;

Alternatively, the material of the hole transport layer is PVK, the thickness of the hole transport layer is 15-25 nm, and the material of the electron transport layer is metal oxide Zn _x Mg _y O, wherein x is 0.90-0.97 and y is 0.03 ~0.1, and the thickness of the electron transport layer is 20 to 50 nm;

Alternatively, the material of the hole transport layer is TFB, the thickness of the hole transport layer is 15-25 nm, the material of the electron transport layer is metal oxide ZnO, and the thickness of the electron transport layer is 20-50 nm.

The material of the hole transport layer is TFB, the thickness of the hole transport layer is 20-23 nm, the material of the electron transport layer is Zn _x Mg _y O, wherein x is 0.92-0.97, y is 0.03-0.08, and the The thickness of the electron transport layer is 25 to 35 nm.

Optionally, the quantum dot electroluminescent device includes an anode, a hole injection layer, a hole transport layer, a quantum dot light-emitting layer, an electron transport layer and a cathode that are stacked in sequence.

Optionally, the quantum dot electroluminescent device further comprises a light extraction layer,

When the cathode is a transmission electrode, the light extraction layer is located on the surface of the cathode on the side away from the anode;

Alternatively, when the cathode is a total reflection electrode, the light extraction layer is located on the surface of the anode on the side away from the cathode.

Optionally, the material of the quantum dot light-emitting layer is red light quantum dots, and the light emission wavelength of the red light quantum dots is 610-625 nm;

Alternatively, the material of the quantum dot light-emitting layer is green quantum dots, and the emission wavelength of the green quantum dots is 525-550 nm.

Beneficial effects: The present disclosure provides a long-life quantum dot device structure. In the present disclosure, under the same current density, when 0.5V≤V _HOD -V _EOD ≤10V, the quantum dot electroluminescence device has a long lifetime.

Description of drawings

FIG. 1 is a schematic structural diagram of a quantum dot electroluminescence device according to an embodiment of the present disclosure.

FIG. 2 is an EOD device corresponding to the quantum dot electroluminescent device shown in FIG. 1 .

FIG. 3 is a HOD device corresponding to the quantum dot electroluminescent device shown in FIG. 1 .

FIG. 4 is a schematic flowchart of a method for preparing a quantum dot electroluminescent device according to an embodiment of the present disclosure.

5 is the current-voltage curve of the EOD device and the HOD device corresponding to the quantum dot electroluminescent device in Example 1.

6 is the current-voltage curve of the EOD device and the HOD device corresponding to the quantum dot electroluminescent device in Example 2.

FIG. 7 is the current-voltage curve of the EOD device and the HOD device corresponding to the quantum dot electroluminescent device in Example 3. FIG.

FIG. 8 is the current-voltage curve of the EOD device and the HOD device corresponding to the quantum dot electroluminescent device in Example 4. FIG.

FIG. 9 is the current-voltage curve of the EOD device and the HOD device corresponding to the quantum dot electroluminescent device in Example 5. FIG.

FIG. 10 is the current-voltage curve of the EOD device and the HOD device corresponding to the quantum dot electroluminescent device in Example 6. FIG.

11 is the current-voltage curve of the EOD device and the HOD device corresponding to the quantum dot electroluminescent device in Comparative Example 1.

Detailed ways

The present disclosure provides a quantum dot electroluminescence device. In order to make the purpose, technical solutions and effects of the present disclosure clearer and clearer, the present disclosure will be described in further detail below. It should be understood that the specific embodiments described herein are only used to explain the present disclosure, but not to limit the present disclosure.

Embodiments of the present disclosure provide a quantum dot electroluminescence device, wherein a pure electronic device corresponding to the quantum dot electroluminescence device is denoted as an EOD device, and a pure hole device corresponding to the quantum dot electroluminescence device is denoted as an EOD device HOD device;

The inventors have found through research and testing that at a current density of more than 5 mA/cm ² , the hole functional layer and electron functional layer of the quantum dot electroluminescent device are configured to be 0.5V≤V _HOD -V _EOD ≤ 10V , the quantum dot electroluminescent device has a long lifetime. This is because the voltage difference between the HOD device and the EOD device is within this range, and more electrons are injected and transported in the quantum dot electroluminescence device. The accumulation of the point light-emitting layer, while promoting the injection of holes into the quantum point light-emitting layer, prolongs the delayed fluorescence lifetime of the excitons and reduces the non-radiative transition of the excitons, so that the quantum dot electroluminescent device has a long lifetime. When V _HOD -V _EOD <0.5V, the carrier of the device itself is in a relatively balanced state. At this time, the quantum dot will appear in the state of two electrons or two holes in the same quantum dot, which is easy to cause Auger recombination, resulting in The brightness decays quickly, which affects the lifespan; when V _HOD -V _EOD >10V, too many electrons accumulate in the quantum dots, which affects the stability of the quantum dots, especially their surface ligands, thereby affecting the lifespan.

It should be noted that the above current density is approximately in the range of 5-50 mA/cm ² . That is, in the range of 5-50 mA/cm ² , when 0.5V≦V _HOD −V _EOD ≦10V, the quantum dot electroluminescence device has a long life. In one embodiment, the current density is approximately in the range of 5-10 mA/cm ² .

In one embodiment, at a current density of 5 mA/cm ² or more, 3V≦V _HOD −V _EOD ≦5V, so as to further improve the lifetime of the quantum dot electroluminescent device.

It should be noted that the pure electronic device (ie, EOD device) corresponding to the quantum dot electroluminescence device refers to: the others are basically the same as the target quantum dot electroluminescence device, and the difference is that the target quantum dot electroluminescence device is electrically The hole functional layer between the anode and the quantum dot light-emitting layer in the electroluminescent device is replaced with a hole blocking layer, such as an electron transport layer used as the hole blocking layer, because the valence band of the inorganic electron transport layer is related to the work of the anode. The functions do not match, so that there is basically no hole injection and transport. Therefore, the charge in this device is caused by the injection and transport of electrons at the cathode terminal, and has nothing to do with holes. That is to say, in the EOD device, only electrons are injected and transported, and holes cannot be injected and transported. The EOD device is used to evaluate the electron injection and transport capability in the device.

The pure hole device (ie, HOD device) corresponding to the quantum dot electroluminescence device refers to: the others are basically the same as the target quantum dot electroluminescence device, and the difference is that the target quantum dot electroluminescence device is placed in the target quantum dot electroluminescence device. The electron functional layer between the cathode and the quantum dot light-emitting layer is replaced with an electron blocking layer, such as a hole transport layer used as the electron blocking layer, because the LUMO energy level of the organic hole transport layer does not match the work function of the cathode, As a result, there is basically no electron injection and transport. Therefore, the charge in this device is caused by the injection and transport of holes at the anode end, and has nothing to do with electrons. That is to say, in the HOD device, only holes are injected and transported, and electrons cannot be injected and transported. The HOD device was used to evaluate the hole injection and transport capabilities.

In this embodiment, the quantum dot electroluminescence device has various forms, and the quantum dot electroluminescence device is divided into a positive type structure and an inverse type structure. When the anode is located on the substrate, the quantum dot electroluminescence device is a positive type structure; When the cathode is located on the substrate, the quantum dot electroluminescent device has an inversion structure. This embodiment will mainly take the structure shown in FIG. 1 as an example for detailed description.

As shown in FIG. 1 , an embodiment of the present disclosure provides a quantum dot electroluminescence device, including an anode, a hole injection layer, a hole transport layer, a quantum dot light-emitting layer, an electron transport layer, a cathode, and a light extraction layer that are stacked in sequence. ;

Wherein, under the current density above 5mA/cm ² , the hole functional layer (hole injection layer and hole transport layer) and electron functional layer (electron transport layer) of the quantum dot electroluminescent device are configured to be 0.5 V≤V _HOD -V _EOD≤10V .

The EOD device corresponding to the quantum dot electroluminescent device shown in FIG. 1 can be shown in FIG. 2 , and the HOD device corresponding to the quantum dot electroluminescent device shown in FIG. 1 can be shown in FIG. 3 .

In this embodiment, the anode is a total reflection electrode, the cathode is a transmission electrode, the light emitted by the quantum dot electroluminescent device is emitted from the cathode, and a light extraction layer is arranged on the cathode, which can increase the light extraction efficiency, thereby improving the device's performance. Luminous efficiency. Of course, the anode can also be a transmissive electrode, and the cathode can be a total reflection electrode. The light emitted by the quantum dot electroluminescent device is emitted from the anode. The light extraction layer is arranged on the anode to increase the light extraction efficiency, thereby improving the efficiency of light extraction. The luminous efficiency of the device.

In one embodiment, the material of the light extraction layer can be the same as the material of the hole transport layer, such as CBP, etc.; it can also be the same as the material of the electron transport layer, such as LiF, etc.; it can also be o-phenanthroline and its derivatives, etc. In one embodiment, the thickness of the light extraction layer is about 30nm-150nm.

In one embodiment, when the quantum dot light-emitting layer emits red light, the emission wavelength of the red quantum dot is 610-635 nm.

In one embodiment, when the quantum dot light-emitting layer emits green light, the emission wavelength of the green quantum dots is 525-555 nm.

In one embodiment, when the quantum dot light-emitting layer emits blue light, the light-emitting wavelength of the blue-light quantum dots is 450-480 nm.

In one embodiment, the quantum dot light-emitting layer has a thickness of 5 nm-50 nm.

In one embodiment, the red light quantum dots, green light quantum dots and blue light quantum dots can be independently selected from one or more of binary phase, ternary phase, quaternary phase quantum dots, etc.; wherein binary phase Phase quantum dots include one or more of CdS, CdSe, CdTe, InP, AgS, PbS, PbSe, HgS, etc., and ternary quantum dots include one or more of ZnCdS, CuInS, ZnCdSe, ZnSeS, ZnCdTe, PbSeS, etc. Or more, the quaternary phase quantum dots include one or more of ZnCdS/ZnSe, CuInS/ZnS, ZnCdSe/ZnS, CuInSeS, ZnCdTe/ZnS, PbSeS/ZnS and the like. The quantum dots can be cadmium-containing or cadmium-free. The quantum dot light-emitting layer of the material has the characteristics of wide excitation spectrum and continuous distribution, and high stability of emission spectrum.

In one embodiment, the anode is a total reflection electrode, and the material of the total reflection electrode may be selected from one of metals such as Al, Ag, Mo, and their alloy materials, but is not limited thereto. It should be noted that, in the embodiment of the present disclosure, ITO electrodes (transparent electrodes), such as ITO/Ag/ITO, may be arranged on both sides of the total reflection electrode to reduce the work function of the electrodes and facilitate charge injection. In one embodiment, the thickness of the total reflection electrode is greater than or equal to 80 nm, such as 80 nm-120 nm. In one embodiment, the thickness of the ITO electrode is 10 nm-30 nm. In one embodiment, the cathode is a transmission electrode, and the material of the transmission electrode can be selected from one of Ag electrode and Ag:Mg alloy electrode, etc., and can also be selected from one of ITO, IZO, AZO, etc. kind. In one embodiment, the thickness of the cathode is about 5 nm-40 nm.

In one embodiment, the anode is a transmissive electrode, and the material of the transmissive electrode can be selected from one of ITO, IZO, AZO, and the like. In one embodiment, the cathode is a total reflection electrode, and the material of the total reflection electrode may be selected from one of metals such as Al, Ag, Mo, and their alloy materials, but is not limited thereto.

In one embodiment, the material of the hole injection layer may be selected from, but not limited to, poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) (PEDOT:PSS), CuPc , P3HT, transition metal oxide, transition metal chalcogenide one or two or more. Wherein, the transition metal oxide includes one or two or more of NiO _x , MoO _x , WO _x , CrO _x , and CuO. The metal chalcogenide compound includes one or two or more of MoS _x , _{MoSex , WS x} _, _WSex , and CuS. In one embodiment, the hole injection layer has a thickness of about 10 nm to 40 nm.

In one embodiment, the material of the hole transport layer can be selected from materials with good hole transport properties, such as but not limited to 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), 4,4',4"-tris(carbazol-9-yl)triphenylamine (TCTA), 4,4'-bis(9-carbazole)biphenyl (CBP), NPB, NiO One or more of , MoO ₃ , etc. In one embodiment, the thickness of the hole transport layer is about 10 nm-40 nm.

In one embodiment, the material of the electron transport layer can be conventional electron transport materials in the art, including but not limited to ZnO, MZO (magnesium zinc oxide), AMO (aluminum zinc oxide), MLZO (magnesium lithium zinc oxide) ), TiO ₂ , CsF, LiF, CsCO ₃ and Alq 3 or a mixture of any combination thereof. In one embodiment, the electron transport layer has a thickness of about 20nm-50nm.

In one embodiment, the hole functional layer includes a hole transport layer, and the electron functional layer is an electron transport layer;

in,

Under the above conditions, the hole functional layer and the electron functional layer of the quantum dot electroluminescence device are configured to be 0.5V≤V _HOD -V _EOD ≤10V, and the quantum dot electroluminescence device has a long lifetime.

Under the above conditions, the hole functional layer and the electron functional layer of the quantum dot electroluminescence device are configured to be 3V≤V _HOD -V _EOD ≤5V, and the quantum dot electroluminescence device has a longer lifetime.

Taking the structure shown in FIG. 1 as an example, the preparation method of the quantum dot electroluminescent device is introduced. An embodiment of the present disclosure provides a method for preparing a quantum dot electroluminescent device, as shown in FIG. 4 , including the steps:

S10, forming a hole injection layer on the anode;

S11, forming a hole transport layer on the hole injection layer;

S12, forming a quantum dot light-emitting layer on the hole transport layer;

S13, forming an electron transport layer on the quantum dot light-emitting layer;

S14, forming a cathode on the electron transport layer;

S15, forming a light extraction layer on the cathode to obtain a quantum dot electroluminescence device.

In the embodiments of the present disclosure, the above-mentioned methods for preparing the layers may be chemical methods or physical methods, wherein chemical methods include but are not limited to chemical vapor deposition methods, continuous ion layer adsorption and reaction methods, anodic oxidation methods, electrolytic deposition methods, and co-precipitation methods. One or more of; physical methods include but are not limited to solution methods (such as spin coating, printing, blade coating, dip-pulling, immersion, spraying, roll coating, casting, slot coating method or strip coating method, etc.), evaporation method (such as thermal evaporation method, electron beam evaporation method, magnetron sputtering method or multi-arc ion coating method, etc.), deposition method (such as physical vapor deposition method) , element layer deposition method, pulsed laser deposition method, etc.) one or more.

The present disclosure will be further described below through specific embodiments.

In an embodiment of the present disclosure, the preparation method of the quantum dot electroluminescence device of Embodiment 1 includes the following steps:

1) A layer of ITO/metal emitter electrode/ITO is deposited on the substrate as the first electrode, wherein the thickness of the first layer of ITO is 20nm, the material of the metal emitter electrode is Ag, the thickness is 100nm, and the thickness of the second layer of ITO is 25nm ;

2) preparing a hole injection layer on the first electrode, the hole injection layer material is polythiophene, and the thickness is 20 nm;

3) prepare a hole transport layer on the hole injection layer, the hole transport layer material is TFB, and the thickness is 25nm;

4) preparing a quantum dot light-emitting layer on the hole transport layer, the light-emitting layer material is a red light quantum dot material, and the light-emitting wavelength of the red light quantum dot material is 625nm, and the thickness is 25nm;

5) An electron transport layer is prepared on the quantum dot light-emitting layer, and the material of the electron transport layer is metal oxide Zn _x Mg _y O, wherein x is 0.95, y is 0.05, and the thickness is 30 nm;

6) Evaporating a cathode on the electron transport layer, the cathode is a Mg:Ag electrode with a thickness of 25nm;

7) Evaporating NPB organic light-extracting material on the cathode with a thickness of 60 nm.

The EOD device and the HOD device corresponding to the top-emitting quantum dot electroluminescence device in this embodiment are shown in FIG. 5 , in FIG. 5 , curve a is the current-voltage curve of the EOD device, and curve b is the current-voltage curve of the HOD device Curve, under the current density of 10mA/cm ² , V _HOD -V _EOD =2.5V, the lifetime T95 of the red quantum dot electroluminescent device is >10000h@1000nits.

In another embodiment of the present disclosure, the preparation method of the quantum dot electroluminescence device of Embodiment 2 includes the following steps:

3) preparing a hole transport layer on the hole injection layer, the hole transport layer material is PVK, and the thickness is 25nm;

4) prepare a quantum dot light-emitting layer on the hole transport layer, the light-emitting layer material is a red light quantum dot material, and the light-emitting wavelength of the red light quantum dot material is 625nm, and the thickness is 25nm;

5) An electron transport layer is prepared on the quantum dot light-emitting layer, and the material of the electron transport layer is metal oxide Zn _x Mg _y O, wherein x is 0.90, y is 0.1, and the thickness is 20 nm;

The EOD device and the HOD device corresponding to the top-emitting quantum dot electroluminescent device in this embodiment are shown in FIG. 6 , in FIG. 6 , curve a is the current-voltage curve of the EOD device, and curve b is the current-voltage curve of the HOD device Curve, under the current density of 5mA/cm ² , V _HOD -V _EOD =0.5V, the lifetime T95 of the red quantum dot electroluminescent device is about 7000h@1000nits.

In yet another embodiment of the present disclosure, the preparation method of the quantum dot electroluminescence device of Embodiment 3 includes the following steps:

2) preparing a hole injection layer on the first electrode, the material of the hole injection layer is polythiophene, and the thickness is 30 nm;

3) preparing a hole transport layer on the hole injection layer, the hole transport layer material is TFB, and the thickness is 15nm;

4) preparing a quantum dot light-emitting layer on the hole transport layer, the light-emitting layer material is a red light quantum dot material, and the light-emitting wavelength of the red light quantum dot material is 625nm, and the thickness is 10nm;

5) preparing an electron transport layer on the quantum dot light-emitting layer, the electron transport layer material is metal oxide ZnO, and the thickness is 50nm;

The EOD device and the HOD device corresponding to the top-emitting quantum dot electroluminescence device of this embodiment are shown in FIG. 7 , in FIG. 7 , curve a is the current-voltage curve of the EOD device, and curve b is the current-voltage curve of the HOD device Curve, under the current density of 20mA/cm ² , V _HOD -V _EOD =10V, the lifetime T95 of the red quantum dot electroluminescent device is >10000h@1000nits.

In yet another embodiment of the present disclosure, the preparation method of the quantum dot electroluminescent device of Embodiment 4 includes the following steps:

3) Prepare a hole transport layer on the hole injection layer, the hole transport layer material is TFB, and the thickness is 23 nm;

4) preparing a quantum dot light-emitting layer on the hole transport layer, the light-emitting layer material is a red light quantum dot material, and the light emission wavelength of the red light quantum dot material is 620nm, and the thickness is 25nm;

The EOD device and the HOD device corresponding to the top-emitting quantum dot electroluminescence device in this embodiment are shown in FIG. 8 . In FIG. 8 , curve a is the current-voltage curve of the EOD device, and curve b is the current-voltage curve of the HOD device. Curve, under the current density of 5mA/cm ² , V _HOD -V _EOD =4.3V, the lifetime T95 of the red quantum dot electroluminescent device is >15000h@1000nits.

In yet another embodiment of the present disclosure, the preparation method of the quantum dot electroluminescence device of Embodiment 5 includes the following steps:

4) preparing a quantum dot light-emitting layer on the hole transport layer, the light-emitting layer material is a red light quantum dot material, and the light-emitting wavelength of the red light quantum dot material is 620nm, and the thickness is 15nm;

5) An electron transport layer is prepared on the quantum dot light-emitting layer, and the material of the electron transport layer is metal oxide Zn _x Mg _y O, wherein x is 0.92, y is 0.08, and the thickness is 25 nm;

The EOD device and the HOD device corresponding to the top-emitting quantum dot electroluminescent device of this embodiment are shown in FIG. 9 , in FIG. 9, curve a is the current-voltage curve of the EOD device, and curve b is the current-voltage curve of the HOD device Curve, under the current density of 5mA/cm ² , V _HOD -V _EOD =3V, the lifetime T95 of the red quantum dot electroluminescent device is >12000h@1000nits.

In yet another embodiment of the present disclosure, the preparation method of the quantum dot electroluminescence device of Embodiment 6 includes the following steps:

3) preparing a hole transport layer on the hole injection layer, the hole transport layer material is TFB, and the thickness is 20nm;

4) preparing a quantum dot light-emitting layer on the hole transport layer, the light-emitting layer material is a red light quantum dot material, and the light-emitting wavelength of the red light quantum dot material is 620nm, and the thickness is 12nm;

5) preparing an electron transport layer on the quantum dot light-emitting layer, and the material of the electron transport layer is metal oxide Zn _x Mg _y O, wherein x is 0.97, y is 0.03, and the thickness is 35 nm;

The EOD device and the HOD device corresponding to the top-emitting quantum dot electroluminescent device in this embodiment are shown in FIG. 10 . In FIG. 10 , curve a is the current-voltage curve of the EOD device, and curve b is the current-voltage curve of the HOD device. Curve, under the current density of 5mA/cm ² , V _HOD -V _EOD =5V, the lifetime T95 of the red quantum dot electroluminescent device is >12000h@1000nits.

In a pair of examples of the present disclosure, the preparation method of the quantum dot electroluminescence device of the comparative example 1 includes the following steps:

3) Prepare a hole transport layer on the hole injection layer, the hole transport layer material is Poly-TPD, and the thickness is 20nm;

4) preparing a quantum dot light-emitting layer on the hole transport layer, the light-emitting layer material is a red light quantum dot material, and the light-emitting wavelength of the red light quantum dot material is 625 nm;

5) preparing an electron transport layer on the quantum dot light-emitting layer, the material of the electron transport layer is metal oxide ZnO, and the thickness is 40nm;

6) Evaporating cathode material on the electron transport layer, the cathode material is Mg:Ag alloy, and the thickness is 25nm;

7) Evaporate an organic light extraction material on the cathode with a thickness of 60 nm.

The EOD device and HOD device corresponding to the top-emitting quantum dot electroluminescence device of this comparative example are shown in Fig. 11 . In Fig. 11, curve a is the current-voltage curve of the EOD device, and curve b is the current-voltage curve of the HOD device. Curve, under the current density of 10mA/cm ² , V _HOD -V _EOD =0.2V, the lifetime T95 of the red quantum dot electroluminescent device is 1000h@1000nits.

It should be understood that the application of the present disclosure is not limited to the above examples, and those of ordinary skill in the art can make improvements or transformations according to the above descriptions, and all such improvements and transformations should fall within the protection scope of the appended claims of the present disclosure.

Claims

A quantum dot electroluminescence device, wherein the pure electronic device corresponding to the quantum dot electroluminescence device is denoted as an EOD device, and the pure hole device corresponding to the quantum dot electroluminescence device is denoted as a HOD device;

Under the same current density, the voltage corresponding to the EOD device is denoted as V EOD , and the voltage corresponding to the HOD device is denoted as V HOD ;

Wherein, under the current density of 5 mA/cm 2 or more, the hole functional layer and the electron functional layer of the quantum dot electroluminescent device are configured to be 0.5V≤V HOD -V EOD ≤10V.
The quantum dot electroluminescent device of claim 1, wherein the current density is 5-50 mA/cm 2 .
The quantum dot electroluminescent device of claim 2, wherein the current density is 5-10 mA/cm 2 .
The quantum dot electroluminescent device according to claim 1, wherein 3V≤V HOD -V EOD≤5V .
The quantum dot electroluminescence device according to claim 1, wherein the quantum dot electroluminescence device has a lifetime T95≥10000h@1000nits.
The quantum dot electroluminescence device according to claim 1, wherein the hole functional layer comprises a hole transport layer, and the electron functional layer is an electron transport layer;

in,

The hole transport layer material is TFB, the hole transport layer thickness is 15-25nm, the electron transport layer material is metal oxide Zn x Mg y O, wherein x is 0.90-0.97, y is 0.03-0.1 , the thickness of the electron transport layer is 20-50 nm;

Alternatively, the material of the hole transport layer is PVK, the thickness of the hole transport layer is 15-25 nm, and the material of the electron transport layer is metal oxide Zn x Mg y O, wherein x is 0.90-0.97 and y is 0.03 ~0.1, and the thickness of the electron transport layer is 20 to 50 nm;

Alternatively, the material of the hole transport layer is TFB, the thickness of the hole transport layer is 15-25 nm, the material of the electron transport layer is metal oxide ZnO, and the thickness of the electron transport layer is 20-50 nm.
The quantum dot electroluminescence device according to claim 4, wherein the hole functional layer comprises a hole transport layer, and the electron functional layer is an electron transport layer;

The material of the hole transport layer is TFB, the thickness of the hole transport layer is 20-23 nm, the material of the electron transport layer is Zn x Mg y O, wherein x is 0.92-0.97, y is 0.03-0.08, and the The thickness of the electron transport layer is 25 to 35 nm.
The quantum dot electroluminescence device according to claim 1, wherein the quantum dot electroluminescence device comprises an anode, a hole injection layer, a hole transport layer, a quantum dot light emitting layer, an electron transport layer and cathode.
The quantum dot electroluminescent device according to claim 8, wherein the quantum dot electroluminescent device further comprises a light extraction layer,

When the cathode is a transmission electrode, the light extraction layer is located on the surface of the cathode on the side away from the anode;

Alternatively, when the cathode is a total reflection electrode, the light extraction layer is located on the surface of the anode on the side away from the cathode.
The quantum dot electroluminescent device according to claim 9, wherein the thickness of the light extraction layer is 30nm-150nm.
The quantum dot electroluminescence device according to claim 8, wherein the material of the quantum dot light-emitting layer is red light quantum dots, and the light emission wavelength of the red light quantum dots is 610-625 nm;

Alternatively, the material of the quantum dot light-emitting layer is green light quantum dots, and the light emission wavelength of the green light quantum dots is 525-550 nm;

Alternatively, the material of the quantum dot light-emitting layer is blue-light quantum dots, and the light-emitting wavelength of the blue-light quantum dots is 450-480 nm.
The quantum dot electroluminescence device according to claim 11, wherein the red light quantum dots, green light quantum dots and blue light quantum dots are independently selected from one of binary phase, ternary phase, quaternary phase quantum dots, etc. one or more.
The quantum dot electroluminescence device according to claim 12, wherein the binary phase quantum dots comprise one or more of CdS, CdSe, CdTe, InP, AgS, PbS, PbSe, HgS and the like.
The quantum dot electroluminescent device according to claim 12, wherein the ternary phase quantum dots comprise one or more of ZnCdS, CuInS, ZnCdSe, ZnSeS, ZnCdTe, PbSeS and the like.
The quantum dot electroluminescence device according to claim 12, wherein the quaternary phase quantum dots comprise one or more of ZnCdS/ZnSe, CuInS/ZnS, ZnCdSe/ZnS, CuInSeS, ZnCdTe/ZnS, PbSeS/ZnS, etc. kind.
The quantum dot electroluminescent device according to claim 11, wherein the quantum dot light-emitting layer has a thickness of 5 nm-50 nm.