CN114695804A - Electron transport layer material, QLED device, preparation method of QLED device and display device - Google Patents

Abstract

The invention provides an electron transport layer material and a preparation method thereof, a QLED device and a preparation method thereof and a display device. An electron transport layer material comprising: a metal oxide doped with a doping element, wherein the doping element comprises Li and F. By doping lithium element and fluorine element in the metal oxide, the electron transfer rate of the electron transport layer is effectively reduced, so that the quantity of electrons and holes in the luminescent layer tends to be more balanced, and the luminescent efficiency of the QLED device is improved.

Description

Electron transport layer material, QLED device and preparation method thereof, and display device

technical field

The present invention relates to the field of display, in particular, to an electron transport layer material and a preparation method thereof, a QLED device and a preparation method thereof, and a display device.

Background technique

Quantum dot light-emitting diodes (QLEDs) are gradually gaining favor in the commercial world in the field of new display technologies, which is due to the relatively excellent properties of quantum dots, such as luminescent color purity and good stability. A large number of scientific research achievements have been presented in the field of quantum dot light-emitting diode device research, in which the mobility of charges in different functional layers is an important technical parameter of QLED devices. Most of the QLED devices in the related art use metal oxide nanoparticles as the material for the electron transport layer, and the injection and transport efficiency of electrons in the device is much greater than the injection and transport efficiency of holes. Electron/hole injection is unbalanced, which in turn limits the improvement of device efficiency.

Therefore, the current electron transport layer materials and preparation methods thereof, QLED devices and preparation methods thereof, and display devices still need to be improved.

SUMMARY OF THE INVENTION

In one aspect of the present invention, the present invention provides an electron transport layer material, comprising: a metal oxide doped with a doping element, wherein the doping element includes Li and F. Thereby, the electron mobility of the electron transport layer can be precisely regulated.

According to an embodiment of the present invention, the metal oxide includes at least one of ZnO and NiO. Thereby, the electron mobility of the electron transport layer can be further regulated.

According to an embodiment of the present invention, the mass fraction of the fluorine element in the metal oxide is 25-40%, and the mass fraction of the lithium element in the metal oxide is 1-5%. Thereby, the electron mobility of the electron transport layer can be further regulated.

In another aspect of the present invention, the present invention provides a method for preparing the aforementioned electron transport layer material, comprising: providing a solvent, adding a metal oxide to the solvent to form a first solution, adding a lithium source substance and a fluorine source substance are added to the first solution to form a second solution, and the second solution is mixed to form a third solution. Thereby, an electron transport layer material having a slower electron mobility can be obtained.

According to an embodiment of the present invention, the solvent includes at least one of ethanol and isopropanol, the lithium source material is lithium acetate dihydrate, and the fluorine source material is tetramethylammonium hydroxide pentahydrate. As a result, a metal oxide doped with a dopant element can be obtained by a relatively simple method.

According to an embodiment of the present invention, the mass fraction of the lithium source substance in the second solution is 1-3%, and the mass fraction of the fluorine source substance in the second solution is 20-40%. Thus, the electron mobility of the electron transport layer can be precisely regulated.

In yet another aspect of the present invention, the present invention provides a method for preparing a QLED device, comprising: providing a substrate, an anode is provided on the substrate, the anode is located on one side of the substrate, and when the anode is far away from all the A hole injection layer is formed on one side of the substrate, a hole transport layer is formed on the side of the hole injection layer away from the anode, and light emission is formed on the side of the hole transport layer away from the hole injection layer layer, an electron transport layer is formed on the side of the light-emitting layer away from the hole transport layer, and a cathode is formed on the side of the electron transport layer away from the light-emitting layer, wherein the material for forming the electron transport layer is The obtained electron transport layer material is prepared by the method described above. Thus, a QLED device with higher luminous efficiency can be obtained.

According to an embodiment of the present invention, forming the hole injection layer further includes: performing a first spin coating process on a side of the anode away from the substrate to form a preformed hole injection layer, and the preformed hole injection layer is subjected to a first spin coating process. The injection layer is subjected to a first annealing treatment to form the hole injection layer. Thereby, a hole injection layer with high hole injection efficiency can be obtained relatively easily.

According to an embodiment of the present invention, the rotational speed of the first spin coating process is 3000-4000 rpm, and the time of the first spin coating process is 45-60 s. Thus, a hole injection layer with a moderate thickness can be obtained relatively easily.

According to an embodiment of the present invention, the temperature of the first annealing treatment is 140-160° C., and the time of the first annealing treatment is 10-20 min. Thereby, a hole injection layer with good performance can be obtained relatively easily.

According to an embodiment of the present invention, forming the hole transport layer further includes: performing a second spin coating process on a side of the hole injection layer away from the anode to form a preformed hole transport layer, The shaped hole transport layer is subjected to a second annealing treatment to form the hole transport layer. Thereby, a hole transport layer with high hole mobility can be obtained relatively easily.

According to an embodiment of the present invention, the rotational speed of the second spin coating process is 3000-3500 rpm, and the time of the second spin coating process is 40-50 s. Thus, a hole transport layer with a moderate thickness can be obtained relatively easily.

According to an embodiment of the present invention, the temperature of the second annealing treatment is 140-160° C., and the time of the second annealing treatment is 20-40 min. Thereby, a hole transport layer with good performance can be obtained relatively easily.

According to an embodiment of the present invention, forming the light emitting layer further includes: performing a third spin coating process on a side of the hole transport layer away from the hole injection layer to form the light emitting layer. Thereby, a light-emitting layer with good performance can be obtained relatively easily.

According to an embodiment of the present invention, the rotational speed of the third spin coating process is 2000-3000 rpm, and the time of the third spin coating process is 40-50 s. Thereby, a light-emitting layer with a moderate thickness can be obtained relatively easily.

According to an embodiment of the present invention, forming the electron transport layer further includes: performing a fourth spin coating process on a side of the light emitting layer away from the hole transport layer to form a preformed electron transport layer, The electron transport layer is subjected to a third annealing treatment to form the electron transport layer. Thereby, an electron transport layer with a slow electron transport rate can be obtained.

According to an embodiment of the present invention, the rotational speed of the fourth spin coating process is 2000-3000 rpm, and the time of the fourth spin coating process is 40-50 s. Thereby, an electron transport layer with a moderate thickness can be obtained relatively easily.

According to an embodiment of the present invention, the temperature of the third annealing treatment is 70-90° C., and the time of the third annealing treatment is 20-40 min. Thereby, an electron transport layer with good performance can be obtained relatively easily.

According to an embodiment of the present invention, it further includes: forming an encapsulation layer on a side of the cathode far away from the electron transport layer, and forming the encapsulation layer includes: providing pre-curing on a side of the cathode far away from the electron transport layer an adhesive layer, the pre-cured adhesive layer is subjected to light treatment to form the encapsulation layer. Therefore, the performance of the QLED device against external water vapor interference can be improved through the arrangement of the encapsulation layer.

According to an embodiment of the present invention, the material for forming the pre-cured adhesive layer is UV resin, the light treatment is ultraviolet light treatment, and the time of the ultraviolet light treatment is 30s. As a result, a QLED device with good packaging performance can be easily obtained.

In yet another aspect of the present invention, the present invention provides a QLED device prepared by the method described above. Therefore, the QLED device has all the features and advantages of the above-mentioned preparation method, which will not be repeated here.

According to an embodiment of the present invention, the material of the hole injection layer includes at least one of PEDOT and PVK, the material of the hole transport layer includes at least one of TFB and PMA, and the material of the light-emitting layer includes At least one of ZnCdS, CdSe and lnAlAs. Thereby, the luminous efficiency of the QLED device can be further improved.

In yet another aspect of the present invention, the present invention provides a display device comprising the aforementioned QLED device. Since the QLED device is as described above, the display device has all the features and advantages of the aforementioned QLED device, which will not be repeated here.

Description of drawings

The above and/or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of embodiments taken in conjunction with the accompanying drawings, wherein:

FIG. 1 shows a schematic flowchart of a method for preparing an electron transport layer material according to an embodiment of the present invention;

FIG. 2 shows a schematic flowchart of a method for fabricating a QLED device according to an embodiment of the present invention;

3 shows a schematic flowchart of a method for preparing a QLED device according to yet another embodiment of the present invention;

FIG. 4 shows a schematic structural diagram of a QLED device according to an embodiment of the present invention;

FIG. 5 shows a schematic structural diagram of a QLED device according to yet another embodiment of the present invention.

Description of reference numbers:

100: substrate; 200: anode; 300: hole injection layer; 400: hole transport layer; 500: light emitting layer; 600: electron transport layer; 700: cathode; 800: encapsulation layer.

Detailed ways

The following describes in detail the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals refer to the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary, only used to explain the present invention, and should not be construed as a limitation of the present invention.

This application is made based on the inventor's discovery of the following problems:

At present, the QLED devices in the related art usually use undoped metal oxides as the material for forming the electron transport layer. The mobility is much smaller than that of the metal oxide forming the electron transport layer, resulting in that the injection and transport efficiency of electrons in the device is much greater than the injection and transport efficiency of holes. Because electrons and holes need to couple in the light-emitting layer to form excitons, excitons radiate transitions, emit photons, and release energy. In the related art QLED device, the transport rate of electrons is higher than that of holes, which makes the number of carriers in the light-emitting layer unbalanced. The electrons and holes are in an unbalanced state, which greatly affects the luminous efficiency of the device.

The present application aims to solve one of the technical problems in the related art to a certain extent.

In one aspect of the present invention, the present invention provides an electron transport layer material, comprising: a metal oxide doped with doping elements, wherein the doping elements include Li and F. By doping lithium and fluorine in metal oxides, the electron migration rate of the electron transport layer is effectively reduced, so that the number of electrons and holes in the light-emitting layer tends to be more balanced, which is beneficial to improve the light emission of QLED devices. efficiency.

In order to facilitate understanding, the principle that the electron transport layer material in this application has the aforementioned beneficial effects is explained below:

In the related art, metal oxide nanoparticles without element doping are usually used as the material of the electron transport layer, such as ZnO and the like. The inventors found that the QLED device using element-free ZnO nanoparticles as the electron transport layer not only has the problems of excess electron injection, unbalanced carrier injection, and low luminous efficiency, but also has many surface defects of ZnO, which is incompatible with quantum dots. When the layers are in direct contact, charge accumulation will occur, and the defect state on the surface of ZnO will cause the exciton dissociation of the light-emitting layer, which in turn leads to the quenching of the light-emitting layer, resulting in a significant decrease in the external quantum efficiency (EQE) of the device.

In the related art, the method of inserting a buffer layer between the electron transport layer and the light-emitting layer is usually used to reduce the electron migration rate, but this method is difficult to obviously change the defect state of the ZnO surface, and the problem of quenching the light-emitting layer caused by the defect state of the ZnO surface cannot be solved. improve.

In this application, the inventors dope the metal oxide with appropriate amount of Li and F, so that the band gap of the metal oxide is widened, the conduction band position is moved up, and the electron injection at the interface between the electron transport layer and the cathode is increased. The potential barrier makes the injection of electrons more difficult, and the electron mobility of the electron transport layer is precisely adjusted to match the hole mobility of the device, which improves the balance of carriers to a certain extent. In addition, the doping element also effectively improves the surface defect state of the metal oxide, thereby inhibiting the quenching phenomenon of the metal oxide on the light-emitting layer, making the number of electrons and holes in the light-emitting layer more balanced, effectively improving the device. luminous efficiency.

According to some embodiments of the present invention, the kind of the metal oxide is not particularly limited, for example, the metal oxide may include at least one of ZnO and NiO. ZnO and NiO have good lattice structure and electrical properties, belong to wide-bandgap semiconductors at room temperature, have high exciton binding energy, and have a strong hole blocking effect when used as the electron transport layer of QLED devices. And the transmittance in the visible light region is as high as 90% or more, which helps to improve the luminous efficiency of the QLED device.

According to some embodiments of the present invention, the proportion of doping elements in the metal oxide is not particularly limited, for example, the mass fraction of fluorine in the metal oxide may be 25-40%, and the mass fraction of lithium in the metal oxide may be 1-5%. When the proportions of doping elements in the metal oxides are all within the above range, the electron mobility of the formed electron transport layer matches the hole mobility of the device; when the proportions of doping elements in the metal oxides are all less than the above ranges When the control effect of the doping element on the metal oxide is not obvious, the electron mobility of the electron transport layer is still much higher than the hole mobility of the device; when the proportion of the doping element in the metal oxide is greater than the above range When , the electron mobility of the electron transport layer is too low, which is unfavorable for the electrons of the cathode to migrate to the light-emitting layer through the electron transport layer. When the proportion of one of the doping elements is less than the above range, and the ratio of the other is greater than the above range, it is also unfavorable for electron transport, resulting in an excessively low electron transport rate, which is unfavorable for improving the performance of the device.

In another aspect of the present invention, the present invention proposes a method for preparing the aforementioned electron transport layer material. Specifically, referring to FIG. 1 , the method includes the following steps:

S10: Provide solvent

According to some embodiments of the present invention, the type of the solvent is not particularly limited as long as it can better disperse the metal oxide nanoparticles, for example, the solvent may be at least one of ethanol and isopropanol.

S20: Add metal oxide to solvent

According to some embodiments of the present invention, in this step, the metal oxide is added to the solvent to form the first solution, and the type of the metal oxide is not particularly limited, for example, the metal oxide may be at least one of ZnO and NiO. In order to facilitate the metal oxide to be uniformly dispersed in the solvent more quickly, the first solution can be stirred, and the temperature of the stirring can be room temperature.

S30: adding the lithium source material and the fluorine source material to the first solution

According to some embodiments of the present invention, in the step of adding a lithium source material and a fluorine source material to the first solution to form a second solution, the metal oxide nanoparticles are doped with an appropriate amount of Li by adding the lithium source and the fluorine source and F, thereby improving the electron mobility of metal oxides and surface defect states and electron transport layers.

According to some embodiments of the present invention, the types of the lithium source material and the fluorine source material are not particularly limited, for example, the lithium source material may be lithium acetate dihydrate (LiAc·H ₂ O), and the fluorine source material may be tetramethyl Ammonium hydroxide pentahydrate (TMAH).

According to some embodiments of the present invention, the ratio of the lithium source material and the fluorine source material added to the first solution is not particularly limited, as long as the addition can make the electron mobility of the metal oxide and the hole transport layer, hole The hole mobility of the injection layer may be matched. For example, the mass fraction of the lithium source substance in the second solution may be 1-3%, and the mass fraction of the fluorine source substance in the second solution may be 20-40%. As a result, the ratio of Li and F doped in the metal oxide can be kept within an appropriate range, so as to achieve precise regulation of electron mobility.

S40: Mixing the second solution

According to some embodiments of the present invention, the method of mixing treatment is not particularly limited, for example, the method of mixing treatment may be stirring treatment, preferably, the time of stirring treatment may be 1 h, and the temperature of stirring treatment may be room temperature.

In yet another aspect of the present invention, the present invention proposes a method for preparing a QLED device, specifically, referring to FIG. 2 , the method includes the following steps:

S100: Provide base plate

According to some embodiments of the present invention, the substrate is provided in the step, and the type of the substrate is not particularly limited. For example, the substrate can be made of conductive glass. Specifically, the conductive glass can be pretreated before use, and the pretreatment includes: sequentially using isopropyl The conductive glass is ultrasonically cleaned with alcohol, water, and acetone, and then treated with ultraviolet UV. The treatment time can be 5-10 minutes, which can effectively remove the residual oil-soluble or water-soluble impurities on the surface of the conductive glass. An anode is formed on one side surface of the anode, and the material for forming the anode is not particularly limited, for example, the material for forming the anode may be ITO. Thus, a substrate provided with an anode can be provided, wherein the anode is located on one side surface of the substrate.

S200: forming a hole injection layer on the side of the anode away from the substrate

According to some embodiments of the present invention, in this step, a hole injection layer is formed on the side of the anode away from the substrate. The method of forming the hole injection layer is not particularly limited, for example, a first spin coating process may be performed on the side of the anode away from the substrate to form a preformed hole injection layer, and the preformed hole injection layer may be subjected to a first annealing process to form a preformed hole injection layer. A hole injection layer is formed. Thus, under the action of an applied electric field, holes can be injected from the anode into the hole injection layer.

According to some embodiments of the present invention, the rotational speed and time of the rotational speed of the first spin coating process are not particularly limited. 60s. Thus, a hole injection layer with a moderate thickness can be obtained relatively easily.

According to some embodiments of the present invention, the temperature and time of the first annealing treatment are not particularly limited, for example, the temperature of the first annealing treatment may be 140-160° C., and the time of the first annealing treatment may be 10-20 min. Thereby, a hole injection layer with high hole injection efficiency can be obtained relatively easily.

According to some embodiments of the present invention, the material for forming the hole injection layer is not particularly limited, for example, the material for forming the hole injection layer may be PEDOT, PVK or other commercial compounds suitable for the hole injection layer.

S300: forming a hole transport layer on the side of the hole injection layer away from the anode

According to some embodiments of the present invention, in the step, a hole transport layer is formed on a side of the hole injection layer away from the anode. The method of forming the hole transport layer is not particularly limited, for example, a second spin coating process may be performed on the side of the hole injection layer away from the anode to form a preformed hole transport layer, and the preformed hole transport layer may be subjected to a second spin coating process. An annealing process is performed to form a hole transport layer. Thereby, the holes of the hole injection layer are transferred to the light emitting layer through the hole transport layer.

According to some embodiments of the present invention, the rotation speed and time of the second spin coating process are not particularly limited, for example, the rotation speed of the second spin coating process may be 3000-3500 rpm, and the time of the second spin coating process may be 40-50 s. Thus, a hole transport layer with a moderate thickness can be obtained relatively easily.

According to some embodiments of the present invention, the temperature and time of the second annealing treatment are not particularly limited, for example, the temperature of the second annealing treatment is 140-160° C., and the time of the second annealing treatment is 20-40 min. Thereby, a hole transport layer with high hole transport efficiency can be obtained relatively easily.

According to some embodiments of the present invention, the material for forming the hole transport layer is not particularly limited, for example, the material for forming the hole transport layer may be TFB, PMA or other commercially available compounds suitable for the hole transport layer.

S400: forming a light-emitting layer on the side of the hole transport layer away from the hole injection layer

According to some embodiments of the present invention, since electrons and holes need to couple in the light-emitting layer to form excitons, the excitons radiate transitions, emit photons, and release energy. However, the transport rate of electrons is higher than that of holes, which makes the number of carriers in the light-emitting layer unbalanced, resulting in an unbalanced phenomenon in which electrons are majority carriers and holes are minority carriers. In the present application, in this step, a light-emitting layer is formed on the side of the hole transport layer away from the hole injection layer, wherein the material for forming the light-emitting layer may be a quantum dot light-emitting material.

According to some embodiments of the present invention, the method of forming the light emitting layer is not particularly limited, for example, a third spin coating process may be performed on the side of the hole transport layer away from the hole injection layer to form the light emitting layer. According to some embodiments of the present invention, the rotational speed and time of the third spin coating process are not particularly limited. For example, the rotational speed of the third spin coating process may be 2000-3000 rpm, and the time of the third spin coating process may be 40-50 s. Thereby, a light-emitting layer with a moderate thickness can be obtained relatively easily.

According to some embodiments of the present invention, the material for forming the light-emitting layer is not particularly limited, for example, the material for forming the light-emitting layer may be ZnCdS, CdSe, lnAlAs or other commercial compounds suitable for the light-emitting layer.

S500: forming an electron transport layer on the side of the light-emitting layer away from the hole transport layer

According to some embodiments of the present invention, in this step, an electron transport layer is formed on the side of the light-emitting layer away from the hole transport layer, and the material for forming the electron transport layer may be an electron transport layer material prepared by the aforementioned method, here No longer.

According to some embodiments of the present invention, the method of forming the electron transport layer is not particularly limited, for example, a fourth spin coating process may be performed on the side of the light-emitting layer away from the hole transport layer to form a preformed electron transport layer, The electron transport layer is subjected to a third annealing treatment to form an electron transport layer. Thereby, an electron transport layer with a slow electron transport rate can be obtained.

According to some embodiments of the present invention, the rotation speed and time of the fourth spin coating process are not particularly limited, for example, the rotation speed of the fourth spin coating process may be 2000-3000 rpm, and the time of the fourth spin coating process may be 40-50 s. Thereby, an electron transport layer with a moderate thickness can be obtained relatively easily.

According to some embodiments of the present invention, the temperature and time of the third annealing treatment are not particularly limited, for example, the temperature of the third annealing treatment may be 70-90° C., and the time of the third annealing treatment may be 20-40 min. Thereby, the electrons of the cathode are transferred to the organic light emitting layer through the electron transport layer.

S600: forming a cathode on the side of the electron transport layer away from the light emitting layer

According to some embodiments of the present invention, in this step, a cathode is formed on the side of the electron transport layer away from the light-emitting layer, and the material for forming the cathode is not particularly limited, for example, the material for forming the cathode may be an Al film or an IZO film. Specifically, an Al film may be formed by a vacuum evaporation process, or an IZO film may be formed by a magnetron sputtering process.

In order to prevent external water vapor from entering the inside of the QLED device and improve the service life of the QLED device, referring to FIG. 3 , the steps of preparing the QLED device may further include:

S700: Forming an encapsulation layer on the side of the cathode away from the electron transport layer

According to some embodiments of the present invention, in this step, an encapsulation layer is formed on the side of the cathode away from the electron transport layer. The method of forming the encapsulation layer is not particularly limited. For example, pre-curing can be provided on the side of the cathode away from the electron transport layer. Adhesive layer, the pre-cured adhesive layer is subjected to light treatment to form an encapsulation layer. The arrangement of the encapsulation layer can effectively block the erosion of the internal structure of the QLED device by external water and oxygen, and improve the structural stability and durability of the QLED.

According to some embodiments of the present invention, the types of materials for forming the pre-cured adhesive layer are not particularly limited, for example, the material for forming the pre-cured adhesive layer may be UV resin, which can be cured by ultraviolet light treatment. The duration of UV light treatment can be 30s. As a result, a QLED device with good packaging performance can be easily obtained.

In yet another aspect of the present invention, the present invention provides a QLED device prepared by the aforementioned method. Therefore, the QLED device has all the features and advantages of the above-mentioned preparation method, which will not be repeated here.

According to some embodiments of the present invention, referring to FIG. 4 , the QLED device includes: a substrate 100 , an anode 200 is provided on the substrate 100 , the anode 200 is located on one side of the substrate 100 , a hole injection layer 300 is located on the anode 200 is located on the side away from the substrate 100, the hole transport layer 400, the hole transport layer 400 is located on the side of the hole injection layer 300 away from the anode 200, the light-emitting layer 500, the light-emitting layer 500 is located at the hole transport layer 400 away from the hole injection layer One side of 300, the electron transport layer 600, the electron transport layer 600 is located on the side of the light-emitting layer 500 away from the hole transport layer 400, the cathode 700, the cathode 700 is located on the side of the electron transport layer 600 away from the light-emitting layer 500, wherein the electron transport The material of the layer 600 is the electron transport layer material prepared by the aforementioned method.

According to some embodiments of the present invention, the structure of the QLED device is not particularly limited. For example, referring to FIG. 5 , on the side of the cathode 700 away from the electron transport layer 600 , an encapsulation layer 800 may also be provided, and the arrangement of the encapsulation layer can effectively block the The erosion of the internal structure of the QLED device by external water and oxygen improves the structural stability and durability of the QLED.

According to some embodiments of the present invention, the material of each layer in the QLED device is not particularly limited, for example, the material of the hole injection layer may include PEDOT, the material of the hole transport layer may include TFB, and the material of the light emitting layer may include ZnCdS. Thereby, the luminous efficiency of the QLED device can be further improved.

In yet another aspect of the present invention, the present invention provides a display device comprising the aforementioned QLED device. Therefore, the display device has all the features and advantages of the aforementioned QLED device, which will not be repeated here.

The solution of the present application will be described below through specific examples. It should be noted that the following examples are only used to illustrate the present application, and should not be regarded as limiting the scope of the present application. If no specific technique or condition is indicated in the examples, the technique or condition described in the literature in the field or the product specification is used. The reagents or instruments used without the manufacturer's indication are conventional products that can be obtained from the market.

Experimental example 1:

1. Preparation of electron transport layer materials:

(1) Preparation of the first solution: using ethanol as a solvent and ZnO as a metal oxide, a ZnO ethanol solution with a concentration of 30 mg/ml is prepared for subsequent use.

(2) Preparation of the second solution: Lithium acetate dihydrate and tetramethylammonium hydroxide pentahydrate were added to the aforementioned ZnO with a concentration of 30 mg/ml in the proportions of Li (2wt%) and F (35wt%), respectively. in solution.

(3) Preparation of the third solution: the second solution was continuously stirred at room temperature for 1 h and then filtered for use.

2. Preparation of QLED devices:

(1) Provide a transparent glass substrate with a thickness of 1 mm, and an ITO electrode with a square resistance of 30Ω/sq is deposited on the surface of the glass substrate, hereinafter referred to as an ITO substrate.

(2) Spin-coating the PEDOT solution on the ITO substrate, followed by annealing treatment, to form a hole injection layer. The rotational speed of the first spin coating treatment was 3000 rpm, the first spin coating treatment time was 45 s, the first annealing treatment temperature was 150° C., and the first annealing treatment time was 15 min.

(3) A 10 mg/ml TFB solution (solvent is chlorobenzene) was spin-coated on the hole injection layer, followed by annealing treatment to form a hole transport layer. The rotation speed of the second spin coating treatment is 3500 rpm, the time of the second spin coating treatment is 50 s, the temperature of the second annealing treatment is 150° C., and the time of the second annealing treatment is 30 min.

(4) 20 mg/ml of ZnCdS quantum dots (solvent is OCT) were spin-coated on the hole transport layer to form a light-emitting layer. The rotational speed of the third spin coating treatment was 2000-3000 rpm, and the time of the third spin coating treatment was 45 s.

(5) The electron transport layer material prepared above is spin-coated on the light-emitting layer, followed by annealing treatment to form an electron transport layer. The rotation speed of the fourth spin coating treatment was 2500 rpm, the time of the fourth spin coating treatment was 40 s, the temperature of the third annealing treatment was 80° C., and the time of the third annealing treatment was 30 min.

(6) Put the spin-coated device in step (5) into an evaporation device, and evaporate to form an AL electrode at a rate of 2 angstroms/second to form a cathode.

(7) Drop UV resin on the central area of the spin-coating surface of the ITO substrate, and after the cover glass is extruded to a uniform thickness, UV irradiation is performed to form an encapsulation layer. The duration of UV light treatment was 30 s.

Example 2-4

Examples 2-4 are consistent with Example 1, and are used to set up parallel experiments to reduce accidental errors.

Comparative Example 1

Comparative Example 1 is the same as Example 1, the difference is that no lithium source and fluorine source are added to the ZnO alcohol solution for forming the electron transport layer in Comparative Example 1, that is, step (2) in step 1 is not performed, and the A 30 mg/ml ZnO alcohol solution was spin-coated to form an electron transport layer.

Comparative Examples 2-4

Comparative Examples 2-4 are consistent with Comparative Example 1, and are used to set up parallel experiments to reduce accidental errors.

The EQE (external quantum efficiency) of the QLED devices in Examples 1-4 and Comparative Examples 1-4 were tested, and the test results are shown in Table 1.

Table 1

Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 average value EQE 7.83% 8.55% 7.90% 7.80% 8.02% Example 1 Example 2 Example 3 Example 4 average value EQE 13.55% 14.00% 13.85% 14.20% 13.90%

Referring to Table 1, it can be seen that the EQE of the QLED device is increased from 8.02% to 13.90%. This shows that by doping an appropriate amount of Li and F in the metal oxide, the band gap of the metal oxide can be widened, the conduction band position can be moved up, and the electron injection barrier at the interface between the electron transport layer and the cathode can be increased, so that the electrons The difficulty of injection is increased, and the electron mobility of the electron transport layer is precisely adjusted to match the hole mobility of the device, which effectively improves the balance of carriers. The improvement method of the electron transport layer material proposed in this application is simple and easy to implement, and the improvement effect is obvious.

In the description of the present invention, the orientation or positional relationship indicated by the terms "upper", "lower", etc. is based on the orientation or positional relationship shown in the accompanying drawings, which is only for the convenience of describing the present invention and does not require the present invention to be in a specific manner. The orientation configuration and operation are therefore not to be construed as limitations of the present invention.

In the description of this specification, description with reference to the terms "one embodiment", "another embodiment", etc. means that a particular feature, structure, material or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention . In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, those skilled in the art may combine and combine the different embodiments or examples described in this specification, as well as the features of the different embodiments or examples, without conflicting each other. In addition, it should be noted that in this specification, the terms "first" and "second" are only used for description purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features.

Although the embodiments of the present invention have been shown and described above, it should be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Embodiments are subject to variations, modifications, substitutions and variations.

Claims (15)

1. An electron transport layer material, comprising: a metal oxide doped with a doping element, wherein the doping element comprises Li and F.

2. The electron transport layer material of claim 1, wherein the metal oxide comprises at least one of ZnO and NiO.

3. The electron transport layer material according to claim 1, wherein the mass fraction of the fluorine element in the metal oxide is 25 to 40%, and the mass fraction of the lithium element in the metal oxide is 1 to 5%.

4. A process for preparing an electron transport layer material according to any of claims 1 to 3,

providing a solvent, and adding a solvent to the solvent,

adding a metal oxide to the solvent to form a first solution,

adding a lithium source material and a fluorine source material to the first solution to form a second solution,

the second solution is subjected to a mixing process to form a third solution.

5. The method of claim 4, wherein the solvent comprises at least one of ethyl alcohol and isopropyl alcohol, the lithium source is lithium acetate dihydrate, and the fluorine source is tetramethylammonium hydroxide pentahydrate.

6. The method according to claim 4, wherein the mass fraction of the lithium source material in the second solution is 1 to 3%, and the mass fraction of the fluorine source material in the second solution is 20 to 40%.

7. A method of making a QLED device, comprising:

providing a substrate, wherein an anode is arranged on the substrate and is positioned on one side of the substrate,

forming a hole injection layer on the anode side far away from the substrate,

a hole transport layer is formed on the side of the hole injection layer remote from the anode,

a light-emitting layer is formed on the side of the hole transport layer remote from the hole injection layer,

an electron transport layer is formed on the side of the light-emitting layer remote from the hole transport layer,

a cathode is formed on the side of the electron transport layer away from the light emitting layer,

wherein the material forming the electron transport layer is an electron transport layer material prepared by the method of any one of claims 4 to 6.

8. The method of claim 7, wherein forming the hole injection layer further comprises: performing a first spin coating treatment on one side of the anode, which is far away from the substrate, to form a preformed hole injection layer, and performing a first annealing treatment on the preformed hole injection layer to form the hole injection layer;

preferably, the rotation speed of the first spin coating treatment is 3000-4000rpm, and the time of the first spin coating treatment is 45-60 s;

preferably, the temperature of the first annealing treatment is 140-160 ℃, and the time of the first annealing treatment is 10-20 min.

9. The method of claim 7, wherein forming the hole transport layer further comprises: performing a second spin coating treatment on the side of the hole injection layer away from the anode to form a preformed hole transport layer, and performing a second annealing treatment on the preformed hole transport layer to form the hole transport layer;

preferably, the rotation speed of the second spin coating treatment is 3000-3500rpm, and the time of the second spin coating treatment is 40-50 s;

preferably, the temperature of the second annealing treatment is 140-160 ℃, and the time of the second annealing treatment is 20-40 min.

10. The method of claim 7, wherein forming the light emitting layer further comprises: performing third spin coating treatment on one side of the hole transport layer far away from the hole injection layer to form the light-emitting layer;

preferably, the rotation speed of the third spin coating process is 2000-3000rpm, and the time of the third spin coating process is 40-50 s.

11. The method of claim 7, wherein forming the electron transport layer further comprises: performing a fourth spin coating treatment on the side, away from the hole transport layer, of the light-emitting layer to form a preformed electron transport layer, and performing a third annealing treatment on the preformed electron transport layer to form the electron transport layer;

preferably, the rotation speed of the fourth spin coating treatment is 2000-3000rpm, and the time of the fourth spin coating treatment is 40-50 s;

preferably, the temperature of the third annealing treatment is 70-90 ℃, and the time of the third annealing treatment is 20-40 min.

12. The method of any one of claims 7-11, further comprising: forming an encapsulation layer on a side of the cathode away from the electron transport layer, the forming the encapsulation layer comprising: arranging a pre-cured adhesive layer on one side of the cathode, which is far away from the electron transport layer, and carrying out illumination treatment on the pre-cured adhesive layer to form the packaging layer;

preferably, the material for forming the pre-cured glue layer is UV resin, the illumination treatment is ultraviolet illumination treatment, and the time of the ultraviolet illumination treatment is 30 s.

13. A QLED device prepared by the method of any one of claims 7-12.

14. A QLED device according to claim 13, wherein the material of the hole injection layer comprises at least one of PEDOT and PVK, the material of the hole transport layer comprises at least one of TFB and PMA, and the material of the light emitting layer comprises at least one of ZnCdS, CdSe and lnAlAs.

15. A display apparatus comprising the QLED device according to claim 13 or 14.

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