CN113690378A

CN113690378A - Quantum dot light-emitting device, preparation method thereof and display panel

Info

Publication number: CN113690378A
Application number: CN202110979870.8A
Authority: CN
Inventors: 梅文海
Original assignee: BOE Technology Group Co Ltd; Beijing BOE Technology Development Co Ltd
Current assignee: BOE Technology Group Co Ltd; Beijing BOE Technology Development Co Ltd
Priority date: 2021-08-25
Filing date: 2021-08-25
Publication date: 2021-11-23
Anticipated expiration: 2041-08-25
Also published as: CN113690378B

Abstract

The application relates to the technical field of display, and provides a quantum dot light-emitting device, a preparation method thereof and a display panel. The quantum dot light-emitting device comprises a carrier transmission layer and a quantum dot layer; the carrier transport layer includes a first portion, a second portion, and a third portion; the quantum dot layer comprises a first quantum dot unit, a second quantum dot unit and a third quantum dot unit which are different in emitted light color; a first quantum dot unit disposed on the first portion, a second quantum dot unit disposed on the second portion, and a third quantum dot unit disposed on the third portion; the hydrophilicity of the surface of the first part close to the first quantum dot unit, the hydrophilicity of the surface of the second part close to the second quantum dot unit and the hydrophilicity of the surface of the third part close to the third quantum dot unit are different. Different hydrophilicities are arranged on the surface of the carrier transport layer under the sub-pixels with different colors, so that the quantum dots with strong hydrophobicity after exposure are removed, and color mixing does not exist in full-color quantum dot display.

Description

Quantum dot light-emitting device, preparation method thereof and display panel

Technical Field

The application relates to the technical field of display, in particular to a quantum dot light-emitting device, a preparation method thereof and a display panel.

Background

A Quantum dot Light Emitting diode Display (QLED) is a novel Display technology developed based on an Organic Light Emitting Display (OLED). The light emitting layer adopted by the QLED is a quantum dot layer, and the principle is that electrons/holes are injected into the quantum dot layer through an electron/hole transport layer, and the electrons and the holes are combined in the quantum dot layer to emit light. Compared with the OLED, the QLED has the advantages of narrow light-emitting peak, high color saturation, wide color gamut and the like.

With the deep development of the quantum dot technology, the research of quantum dot display is increasingly deep, the quantum efficiency is continuously improved, the level of industrialization is basically reached, and the industrialization is a future trend by further adopting new processes and technologies. The preparation of high-resolution QLED or QD-LCD by using quantum dots for patterning is an important issue, but the residue is easily formed after the development process in the current process of directly patterning the quantum dots, so that the color mixing problem exists in full-color quantum dot display.

Disclosure of Invention

The application aims to provide a quantum dot light-emitting device, which enables quantum dots with strong hydrophobicity after exposure to be removed in a developing process by controlling hydrophilicity of different degrees on the surface of a carrier transmission layer under sub-pixels with different colors, so that the problem of quantum dot residue on the carrier transmission layer is solved, and color mixing does not exist in the display of the obtained full-color quantum dots.

A first aspect of the present application provides a quantum dot light emitting device including a carrier transport layer and a quantum dot layer; the carrier transport layer includes a first portion, a second portion, and a third portion; the quantum dot layer comprises a first quantum dot unit, a second quantum dot unit and a third quantum dot unit; a first quantum dot unit disposed on the first portion, a second quantum dot unit disposed on the second portion, and a third quantum dot unit disposed on the third portion; the colors of the light emitted by the first quantum dot unit, the second quantum dot unit and the third quantum dot unit are different; the hydrophilicity of the surface of the first portion on the side close to the first quantum dot unit, the hydrophilicity of the surface of the second portion on the side close to the second quantum dot unit, and the hydrophilicity of the surface of the third portion on the side close to the third quantum dot unit are different.

In some embodiments, the hydrophilicity of a surface of the first portion on a side close to the first quantum dot unit is greater than the hydrophilicity of a surface of the second portion on a side close to the second quantum dot unit, and the hydrophilicity of a surface of the second portion on a side close to the second quantum dot unit is greater than the hydrophilicity of a surface of the third portion on a side close to the third quantum dot unit.

In some embodiments, a hydroxyl group is attached to the carrier transport layer.

In some embodiments, the hydroxyl group includes a first hydroxyl group and a second hydroxyl group, the first hydroxyl group being attached to the carrier transport layer by an adsorption bond; the second hydroxyl is connected on the carrier transport layer through a dangling bond.

In some embodiments, the first number of hydroxyl groups attached to the first moiety is greater than the first number of hydroxyl groups attached to the second moiety, and the first number of hydroxyl groups attached to the second moiety is greater than the first number of hydroxyl groups attached to the third moiety.

In some embodiments, the number of second hydroxyl groups attached to the first portion, the number of second hydroxyl groups attached to the second portion, and the number of second hydroxyl groups attached to the third portion are the same.

In some embodiments, the electron binding energy of the first hydroxyl group to the carrier transport layer is less than the electron binding energy of the second hydroxyl group to the carrier transport layer.

In some embodiments, the stability of the luminescence quantum yield of the first quantum dot unit is greater than the stability of the luminescence quantum yield of the second quantum dot unit; the stability of the luminescence quantum yield of the second quantum dot unit is greater than the stability of the luminescence quantum yield of the third quantum dot unit.

In some embodiments, the carrier transport layer is an electron transport layer, further comprising: the quantum dot structure comprises a first electrode, a hole transport layer, a hole injection layer and a second electrode, wherein the first electrode is arranged on one side, far away from the quantum dot layer, of the electron transport layer, and the hole transport layer, the hole injection layer and the second electrode are sequentially arranged on one side, far away from the electron transport layer, of the quantum dot layer.

In some embodiments, the carrier transport layer is a hole transport layer, further comprising: the quantum dot structure comprises a hole injection layer and a second electrode which are sequentially arranged on one side of the hole transmission layer, which is far away from the quantum dot layer, and an electron transmission layer and a first electrode which are sequentially arranged on one side of the quantum dot layer, which is far away from the hole transmission layer.

In some embodiments, the carrier transport layer is in direct contact with the quantum dot layer.

The second aspect of the present application provides a method for manufacturing a quantum dot light emitting device, including: forming a carrier transport layer and a quantum dot layer; wherein the carrier transport layer includes a first portion, a second portion, and a third portion; the quantum dot layer comprises a first quantum dot unit, a second quantum dot unit and a third quantum dot unit; the colors of the light emitted by the first quantum dot unit, the second quantum dot unit and the third quantum dot unit are different; a first quantum dot unit disposed on the first portion, a second quantum dot unit disposed on the second portion, and a third quantum dot unit disposed on the third portion; the hydrophilicity of the surface of the first portion on the side close to the first quantum dot unit, the hydrophilicity of the surface of the second portion on the side close to the second quantum dot unit, and the hydrophilicity of the surface of the third portion on the side close to the third quantum dot unit are different.

In some embodiments, the hydrophilicity of the surface of the first portion on the side close to the first quantum dot unit, the hydrophilicity of the surface of the second portion on the side close to the second quantum dot unit, and the hydrophilicity of the surface of the third portion on the side close to the third quantum dot unit are different by means of ultraviolet light irradiation.

In some embodiments, the method for manufacturing the quantum dot light emitting device comprises: carrying out first ultraviolet irradiation on the carrier transport layer; spin coating a first quantum dot layer; exposing and developing to pattern the first quantum dot layer to form a first quantum dot unit; dark state treatment is carried out, so that the original hydrophilicity of the carrier transport layer which is not covered is recovered; carrying out secondary ultraviolet irradiation on the carrier transport layer; spin coating a second quantum dot layer; exposing and developing to pattern the second quantum dot layer to form a second quantum dot unit; dark state treatment is carried out, so that the original hydrophilicity of the carrier transport layer which is not covered is recovered; carrying out third ultraviolet irradiation on the carrier transport layer; spin coating a third quantum dot layer; and exposing and developing to pattern the third quantum dot layer to form a third quantum dot unit.

In some embodiments, the first exposure to uv light is at a dose greater than the second exposure to uv light, and the second exposure to uv light is at a dose greater than the third exposure to uv light.

The third aspect of the present application provides a display panel comprising the quantum dot light-emitting device provided by the first aspect of the present application.

According to the quantum dot light-emitting device, the surfaces of the carrier transmission layers under the sub-pixels with different colors have hydrophilicity in different degrees; after the quantum dots of spin coating are solidified, the exposed non-solidified quantum dots have strong hydrophobicity, and in the developing process, the quantum dots with strong hydrophobicity and the carrier transmission layer with strong hydrophilicity have a strong repulsion effect, so that the quantum dots to be removed are removed, the residual problem after patterning of the quantum dots can be avoided, color mixing does not exist in full-color quantum dot display, and the product quality and the display quality are improved.

Of course, not all advantages described above need to be achieved at the same time in the practice of any one product or method of the present application.

Drawings

In order to more clearly illustrate the technical solutions in the present application or the prior art, the drawings needed for describing the embodiments or the prior art are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and other embodiments can be obtained by those skilled in the art according to the drawings.

FIG. 1 is a schematic diagram showing the change of the number of hydroxyl groups adsorbed on the surface of an electron transport layer after the electron transport layer is irradiated by ultraviolet light;

FIG. 2a is a graph of the contact angle test results for a zinc oxide electron transport layer after irradiation with UV light at a dose of 4500 mj;

FIG. 2b is a graph of the contact angle test results for a zinc oxide electron transport layer after irradiation with UV light at a dose of 13500 mj;

FIG. 2c is a graph of the residual photoluminescence spectrum (PL) of red quantum dots on the zinc oxide electron transport layer after irradiation with UV light at a dose of 4500mj and the zinc oxide electron transport layer after irradiation with UV light at a dose of 13500 mj;

FIG. 3 is a schematic diagram of sub-pixels of different colors in combination with portions of different hydrophilic electron transport layers;

fig. 4 is a schematic structural diagram of an inverted-structure quantum dot light-emitting device;

FIG. 5 is a schematic structural diagram of a quantum dot light-emitting device with a front-mounted structure;

fig. 6 is a schematic view of a manufacturing process of the quantum dot light-emitting device with the inverted structure.

Detailed Description

The technical solutions in the present application will be described clearly and completely with reference to the accompanying drawings in the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments that can be derived by one of ordinary skill in the art from the description herein are intended to be within the scope of the present disclosure.

A first aspect of the present application provides a quantum dot light emitting device including a carrier transport layer and a quantum dot layer; the carrier transport layer includes a first portion, a second portion, and a third portion; the quantum dot layer comprises a first quantum dot unit, a second quantum dot unit and a third quantum dot unit; a first quantum dot unit disposed on the first portion, a second quantum dot layer disposed on the second portion, and a third quantum dot layer disposed on the third portion; the colors of the light emitted by the first quantum dot unit, the second quantum dot unit and the third quantum dot unit are different; the hydrophilicity of the surface of the first portion on the side close to the first quantum dot unit, the hydrophilicity of the surface of the second portion on the side close to the second quantum dot unit, and the hydrophilicity of the surface of the third portion on the side close to the third quantum dot unit are different.

According to the quantum dot light-emitting device provided by the application, the surfaces of the carrier transmission layers under the quantum dot units with different colors have hydrophilicity in different degrees; after the quantum dots of spin coating solidify, the exposed non-solidified quantum dots have strong hydrophobicity, and in the developing process, the quantum dots with strong hydrophobicity and the carrier transmission layer with strong hydrophilicity have a strong repulsion effect, so that the quantum dots to be removed are easy to remove, the residual problem after the patterning of the quantum dots can be avoided, the color mixing does not exist in the full-color quantum dot display, and the product quality and the display quality are improved.

In a further embodiment of the present application, the hydrophilicity of the surface of the first portion on the side close to the first quantum dot unit is greater than the hydrophilicity of the surface of the second portion on the side close to the second quantum dot unit, and the hydrophilicity of the surface of the second portion on the side close to the second quantum dot unit is greater than the hydrophilicity of the surface of the third portion on the side close to the third quantum dot unit.

By controlling the hydrophilicity of different parts of the surfaces of the carrier transmission layers corresponding to the quantum dot units with different colors, the hydrophilicity is reduced as much as possible under the condition that the quantum dot residues can be removed, so that the quantum dot quenching is avoided.

In a further embodiment of the present application, a hydroxyl group is attached to the carrier transport layer.

In a further embodiment of the present application, the hydroxyl group includes a first hydroxyl group and a second hydroxyl group, the first hydroxyl group being connected to the carrier transport layer by an adsorption bond; the second hydroxyl is connected on the carrier transport layer through a dangling bond.

In further embodiments of the present application, the number of first hydroxyl groups attached to the first moiety is greater than the number of first hydroxyl groups attached to the second moiety, and the number of first hydroxyl groups attached to the second moiety is greater than the number of first hydroxyl groups attached to the third moiety.

In a further embodiment of the present application, the number of second hydroxyl groups attached to the first portion, the number of second hydroxyl groups attached to the second portion, and the number of second hydroxyl groups attached to the third portion are the same.

The inventor finds in research that a carrier transport layer such as a zinc oxide electron transport layer irradiated by ultraviolet light can increase the number of hydroxyl groups connected, thereby increasing the hydrophilicity of the surface of the electron transport layer, and the specific result is shown in fig. 1. Fig. 1 is a schematic diagram showing the change of the number of hydroxyl groups attached to the surface of the electron transport layer after being irradiated by ultraviolet light, and it can be known from fig. 1 that: after the electron transport layer 11 formed on the first electrode 10 is irradiated by ultraviolet light, the number of hydroxyl groups connected to the electron transport layer through an adsorption bond is increased, the number of hydroxyl groups connected to the electron transport layer through a suspension bond is not changed, and the number of total hydroxyl groups connected to the electron transport layer is increased.

When the inventors test the contact angle of the zinc oxide electron transport layer with water, the stronger the hydrophilicity of the surface of the electron transport layer, the less the quantum dots remain, and the specific results are shown in fig. 2a, 2b and 2 c. Fig. 2a is a graph showing the contact angle test result of the zinc oxide electron transport layer after being irradiated by ultraviolet light with a dose of 4500mj, and it can be seen from fig. 2a that the contact angle of the liquid drop is large. Fig. 2b is a graph showing the contact angle test result of the zinc oxide electron transport layer after being irradiated by ultraviolet light with a dose of 13500mj, and it can be seen from fig. 2b that the contact angle of the liquid drop is small. Fig. 2c is a graph of photoluminescence spectra (PL) of red quantum dots remaining on the zinc oxide electron transport layer after the irradiation of ultraviolet light with a dose of 4500mj and the zinc oxide electron transport layer after the irradiation of ultraviolet light with a dose of 13500mj, and it can be seen from fig. 2c that there is red quantum dot remaining on the zinc oxide electron transport layer after the irradiation of ultraviolet light with a dose of 4500mj (corresponding to curve a) and there is no red quantum dot remaining on the zinc oxide electron transport layer after the irradiation of ultraviolet light with a dose of 13500mj (corresponding to curve b).

In further embodiments of the present application, the electron binding energy of the first hydroxyl group to the carrier transport layer is less than the electron binding energy of the second hydroxyl group to the carrier transport layer.

In a further embodiment of the present application, the stability of the luminescence quantum yield of the first quantum dot unit is greater than the stability of the luminescence quantum yield of the second quantum dot unit; the stability of the luminescence quantum yield of the second quantum dot unit is greater than the stability of the luminescence quantum yield of the third quantum dot unit.

The stability of the luminescence quantum yield is the ability of the luminescence quantum yield to remain constant as the processing conditions change. The stability of the luminescence quantum yield is high, which means that the change of the luminescence quantum yield is small under different processing conditions; the small stability of the luminescence quantum yield means that the luminescence quantum yield varies greatly under different processing conditions.

The first quantum dot unit that this application adopted can be red quantum dot unit, and the second quantum dot unit can be green quantum dot unit, and the third quantum dot unit can be blue quantum dot unit.

Due to the fact that the red quantum dots, the green quantum dots and the blue quantum dots are different in size, the specific surface areas of the quantum dots are different, the number of surface ligands is different, and therefore the hydrophilic capacities of the surfaces of the quantum dots with different colors are different. The stability of the luminous quantum yield of the red quantum dots is maximum, and the surface ligand is minimum; the stability of the luminous quantum yield of the blue quantum dots is minimum, and the surface ligand is maximum; therefore, the carrier transmission layer corresponding to the red quantum dot unit has the strongest hydrophilicity and the largest hydroxyl content; and the carrier transmission layer corresponding to the blue quantum dot unit has the weakest hydrophilicity and the least hydroxyl content.

Fig. 3 shows a schematic diagram of sub-pixels with different colors and portions of hydrophilic electron transport layer, as can be seen from fig. 3: the numbers of the hydroxyl groups adsorbed on the surfaces of the first part 111, the second part 112 and the third part 113 of the electron transport layer formed on the first electrode 10 are different, and different electron transport layer parts are matched with quantum dot layers with different colors; specifically, the number of hydroxyl groups adsorbed on the surface of the first part 111 of the electron transport layer collocated with the red quantum dot unit R is the largest, and the number of hydroxyl groups adsorbed on the surface of the third part 113 of the electron transport layer collocated with the blue quantum dot unit B is the smallest.

The hydrophilicity of the surface of the first part of the carrier transmission layer corresponding to the red quantum dot unit is controlled to be larger than the hydrophilicity of the surface of the second part of the carrier transmission layer corresponding to the green quantum dot unit, the hydrophilicity of the surface of the second part of the carrier transmission layer corresponding to the green quantum dot unit is larger than the hydrophilicity of the surface of the third part of the carrier transmission layer corresponding to the blue quantum dot unit, under the condition that the quantum dot residues can be removed, the adsorption quantity of hydroxyl on the surface of the carrier transmission layer is reduced as far as possible, the phenomenon that the quenching of the quantum dots is easily caused due to the fact that the excessive hydroxyl on the surface of the carrier transmission layer is in direct contact with the quantum dots is avoided, and finally the product quality and the display quality are improved.

In a further embodiment of the present application, the carrier transport layer is an electron transport layer, further comprising: the quantum dot structure comprises a first electrode, a hole transport layer, a hole injection layer and a second electrode, wherein the first electrode is arranged on one side, far away from the quantum dot layer, of the electron transport layer, and the hole transport layer, the hole injection layer and the second electrode are sequentially arranged on one side, far away from the electron transport layer, of the quantum dot layer.

The material of the electron transport layer adopted in the application is at least one selected from zinc oxide, titanium oxide, zirconium oxide, magnesium-doped zinc oxide, tin oxide, lithium-doped zinc oxide, gallium-doped zinc oxide and aluminum-doped zinc oxide.

The electron transport layer adopted by the application has hydrophilicity, and the structure of the material can be a porous nano structure. The porous nanostructure refers to a structure with holes formed between the nanostructures, and the specific shape is not limited, for example, the nanostructure may include a nanorod or a spherical nanoparticle.

The method for preparing the electron transport layer is not limited in the present application as long as the object of the present application can be achieved, and for example, the electron transport layer material may be spin-coated on the first electrode and then annealed.

The electron transport layer material may be dissolved or suspended in a solvent, and the solvent used herein is not limited as long as the purpose of the present application can be achieved, for example, an ethanol solution. The concentration of the electron transport layer material dissolved or suspended in the solvent is not limited as long as the object of the present application can be achieved, and for example, the mass concentration is 75 mg/mL.

The method for spin coating the electron transport layer material on the first electrode is a method commonly used in the art, and is not limited herein, and for example, the spin coating may be performed by a sol-gel method. The temperature and time of annealing in the present application are not limited as long as the object of the present application can be achieved, and for example, the annealing may be performed at 180 ℃ for 1 min.

The structure schematic diagram of the quantum dot light-emitting device with the inverted structure provided by the present application is shown in fig. 4, and it can be seen from fig. 4 that: the quantum dot light-emitting device with the inverted structure comprises a first electrode 10, an electron transport layer 11, a quantum dot layer 12, a hole transport layer 13, a hole injection layer 14 and a second electrode 15 which are sequentially stacked; wherein the electron transport layer 11 includes a first portion 111, a second portion 112, and a third portion 113, the hydrophilicity of the surface of the first portion 111 on the side close to the quantum dot layer 12 is greater than the hydrophilicity of the surface of the second portion 112 on the side close to the quantum dot layer 12, and the hydrophilicity of the surface of the second portion 112 on the side close to the quantum dot layer 12 is greater than the hydrophilicity of the surface of the third portion 113 on the side close to the quantum dot layer 12; the quantum dot layer 12 includes red quantum dot units R, green quantum dot units G, and blue quantum dot units B; the red quantum dot unit R is disposed on the first portion 111, the green quantum dot unit G is disposed on the second portion 112, and the blue quantum dot unit B is disposed on the third portion 113.

The quantum dot light emitting device with the inverted structure provided by the present application may further include an electron injection layer disposed between the electron transport layer 11 and the first electrode 10.

The materials of the electron injection layer, the hole transport layer and the hole injection layer are not limited, and can be determined according to actual requirements.

The first electrode 10 can be used as a cathode, and the material of the first electrode is not limited, and for example, the first electrode can be ITO (indium tin oxide), FTO (fluorine-doped SnO)₂) Aluminum (Al), silver (Ag), and the like.

The second electrode 14 may serve as an anode, and the material of the second electrode is not limited, and may be, for example, silver (Ag), aluminum (Al), IZO (indium zinc oxide), and the like.

In a further embodiment of the present application, the carrier transport layer is a hole transport layer, further comprising: the quantum dot structure comprises a hole injection layer and a second electrode which are sequentially arranged on one side of the hole transmission layer, which is far away from the quantum dot layer, and an electron transmission layer and a first electrode which are sequentially arranged on one side of the quantum dot layer, which is far away from the hole transmission layer.

The material of the hole transport layer used in the present application is selected from at least one of nickel oxide, molybdenum oxide, tungsten oxide, vanadium oxide, molybdenum sulfide, tungsten sulfide, and copper oxide.

The hole transport layer adopted by the application has hydrophilicity, and the structure of the material can be a porous nano structure. The porous nanostructure refers to a structure with holes formed between the nanostructures, and the specific shape is not limited, for example, the nanostructure may include a nanorod or a spherical nanoparticle.

The method for preparing the hole transport layer is not limited in the present application as long as the object of the present application can be achieved, and for example, the hole transport layer material may be spin-coated on the second electrode and then annealed.

The hole transport layer material may be dissolved or suspended in a solvent, and the solvent used herein is not limited as long as the purpose of the present application can be achieved, for example, an ethanol solution. The concentration of the hole transport layer material dissolved or suspended in the solvent is not limited as long as the object of the present application can be achieved, and for example, the mass concentration is 25 mg/mL.

The method of spin coating the hole transport layer material on the second electrode is a method commonly used in the art and is not limited herein. The temperature and time of annealing are not limited in the present application as long as the object of the present application can be achieved, and for example, the annealing may be performed at 120 ℃ for 2 min.

The structural schematic diagram of the quantum dot light-emitting device with the positive structure provided by the application is shown in fig. 5, and it can be seen from fig. 5 that: the positive structure quantum dot light-emitting device comprises a second electrode 20, a hole injection layer 31, a hole transport layer 21, a quantum dot layer 22, an electron transport layer 23 and a first electrode 24 which are sequentially stacked; wherein the hole transport layer 21 includes a first portion 211, a second portion 212, and a third portion 213, the hydrophilicity of the surface of the first portion 211 on the side close to the quantum dot layer 12 is greater than the hydrophilicity of the surface of the second portion 212 on the side close to the quantum dot layer 12, and the hydrophilicity of the surface of the second portion 212 on the side close to the quantum dot layer 12 is greater than the hydrophilicity of the surface of the third portion 213 on the side close to the quantum dot layer 12; the quantum dot layer 22 includes red, green and blue quantum dot units R, G and B; the red quantum dot unit R is disposed on the first portion 211, the green quantum dot unit G is disposed on the second portion 212, and the blue quantum dot unit B is disposed on the third portion 213.

The front-mounted structure quantum dot light-emitting device provided by the application can further comprise an electron injection layer, and the electron injection layer is arranged between the electron transport layer 23 and the first electrode 24.

The materials of the electron injection layer, the electron transport layer and the hole injection layer are not limited in the present application, and may be determined according to actual requirements.

The first electrode 24 can be used as a cathode, and the material of the first electrode is not limited, and for example, the first electrode can be ITO (indium tin oxide), FTO (fluorine-doped SnO)₂) Aluminum (Al), silver (Ag), and the like.

The second electrode 20 may serve as an anode, and the material of the second electrode is not limited, and may be, for example, silver (Ag), aluminum (Al), IZO (indium zinc oxide), and the like.

In a further embodiment of the present application, the hydrophilicity of the surface of the first portion on the side close to the first quantum dot unit, the hydrophilicity of the surface of the second portion on the side close to the second quantum dot unit, and the hydrophilicity of the surface of the third portion on the side close to the third quantum dot unit are made different by means of ultraviolet light irradiation.

In a further embodiment of the present application, a method for manufacturing a quantum dot light emitting device includes the steps of:

(1) carrying out first ultraviolet irradiation on the carrier transport layer;

(2) spin coating a first quantum dot layer;

(3) exposing and developing to pattern the first quantum dot layer to form a first quantum dot unit;

(4) dark state treatment is carried out, so that the original hydrophilicity of the carrier transport layer which is not covered is recovered;

(5) carrying out secondary ultraviolet irradiation on the carrier transport layer;

(6) spin coating a second quantum dot layer;

(7) exposing and developing to pattern the second quantum dot layer to form a second quantum dot unit;

(8) dark state treatment is carried out, so that the original hydrophilicity of the carrier transport layer which is not covered is recovered;

(9) carrying out third ultraviolet irradiation on the carrier transport layer;

(10) spin coating a third quantum dot layer;

(11) and exposing and developing to pattern the third quantum dot layer to form a third quantum dot unit.

In a further embodiment of the present application, the dose of the first irradiation of ultraviolet light is greater than the dose of the second irradiation of ultraviolet light, and the dose of the second irradiation of ultraviolet light is greater than the dose of the third irradiation of ultraviolet light.

The dosage of ultraviolet light irradiating the carrier transport layer can influence the adsorption quantity of hydroxyl on the surface of the carrier transport layer, and the adsorption quantity of the hydroxyl on the surface of different parts of the carrier transport layer is different by controlling the dosage of ultraviolet light irradiating in different steps, so that the adsorption quantity of the hydroxyl on the surface is reduced as much as possible under the condition that the quantum dot residue can be removed, and the phenomenon that quenching of the quantum dot is easily caused due to direct contact of excessive hydroxyl and the quantum dot is avoided.

The dose of the ultraviolet irradiation is not particularly limited as long as the object of the present application can be achieved, and for example, the dose of the first ultraviolet irradiation used in the step (1) is 9000mj to 18000 mj; the dose of the second ultraviolet irradiation adopted in the step (5) is 8100mj-13500 mj; the dose of the third ultraviolet irradiation adopted in the step (9) is 6300mj to 9000 mj.

The emission wavelength of the ultraviolet light source used for the ultraviolet light irradiation is not limited as long as the object of the present application can be achieved, and for example, the emission wavelength of the ultraviolet light source used for the ultraviolet light irradiation is 155nm to 435 nm.

The time of the dark state treatment is not limited in the present application as long as the object of the present application can be achieved, and for example, the time of the dark state treatment is not less than 12 hours.

In the developing process, the quantum dots with strong hydrophobicity are removed, so that an uncovered carrier transport layer is formed. The carrier transport layer which is not covered can be restored to the original hydrophilic state by performing a dark state treatment such as a dark state standing.

When the quantum dot layer is spin-coated, the quantum dot dispersion liquid adopted comprises the quantum dots, and the quantum dots are coordinated and combined with the photolysis hydrophilic ligand. The material structure of the quantum dot is not limited in the present application, and for example, the quantum dot may include a core-shell structure or a perovskite nanocrystal structure. Specifically, the core-shell structure includes an inner core layer and a coating layer surrounding the inner core layer, the inner core layer is made of cadmium selenide (CdSe) or cadmium sulfide (CdS), and the coating layer is made of any one of zinc sulfide (ZnS), zinc oxide (ZnO) and zinc selenide (ZnSe). The red and green quantum dots are generally InP system materials, such as InP/ZnS or InP/ZnSe, and mainly have different sizes; and blue quantum dots are generally quantum dot materials of the ZnSe system.

The quantum dot dispersion solution adopted by the application comprises the photolysis hydrophilic ligand which is in coordination combination with the quantum dots, and the photolysis hydrophilic ligand is configured to enable the quantum dot layer to have hydrophobicity after exposure. The quantum dot layer includes photolyzable hydrophilic ligands, thereby having hydrophilicity; in the exposure process, the photolytic hydrophilic ligand is decomposed to form a hydrophobic end, so that the quantum dots to be removed have strong hydrophobicity; in the subsequent development process, quantum dots with strong hydrophobicity and carrier transport layers with strong hydrophilicity have a large repulsive effect, so that the quantum dots to be removed are removed. The material and structure of the photolyzable hydrophilic ligand coordinately bound to the quantum dot are not limited as long as the purpose of the present application can be achieved, and for example, R-2-amino-3- (S-thiobutyl) propionic acid may be used as the photolyzable hydrophilic ligand.

The quantum dot dispersion used in the present application may include a photoacid generator to promote the photolytic hydrophilic ligand to decompose to form a hydrophobic end. The kind of the photoacid generator in the present application is not limited, and for example, 2, 4-bis (trichloromethyl) -6-p-methoxystyryl-S-triazine may be used as the photoacid generator, and the added mass may be 5% of the total mass of the quantum dot dispersion.

The preparation method of the quantum dot dispersion liquid is not limited in the present application, and is a method commonly used in the art. For example, the quantum dot material is a cadmium selenide/zinc sulfide core-shell structure, and the original ligand is oleic acid; the preparation method of the quantum dot dispersion liquid comprises the following steps: drying the solvent of the quantum dot octane dispersion liquid, dispersing the dispersion liquid by using chloroform, adding a ligand R-2-amino-3- (S-thiobutyl) propionic acid, and stirring at room temperature to complete ligand exchange; then, precipitating the quantum dots by using methanol, centrifuging and removing a supernatant; and dispersing the quantum dots by using chloroform, precipitating by using methanol, centrifuging, removing supernatant, and re-dispersing the quantum dot powder in toluene after vacuum pumping to obtain the quantum dot dispersion liquid. Further, 2, 4-bis (trichloromethyl) -6-p-methoxystyryl-S-triazine as a photoacid generator was added to the obtained quantum dot dispersion.

The method of spin-coating the quantum dot layer on the carrier transport layer after the ultraviolet light irradiation is a method commonly used in the art, and the present application is not limited as long as the object of the present application can be achieved, for example, spin-coating at a rate of 3000rpm for 30 s. The quantum dot layer to be patterned formed herein includes a retention region and a removal region.

The dose of the ultraviolet light irradiation used in the exposure is not limited as long as the object of the present application can be achieved, and for example, the dose of the ultraviolet light irradiation is 150 mj.

The exposure method used in the present application is a method commonly used in the art, and the present application is not limited as long as the purpose of the present application can be achieved. For example, a mask is used to expose a quantum dot layer to be patterned; the mask plate comprises a light transmitting area and a light shading area, the light transmitting area corresponds to a removing area of the quantum dot layer to be patterned, and the light shading area corresponds to a reserved area of the quantum dot layer to be patterned. The light rays emitted to the removal region of the quantum dot layer to be patterned can pass through the light transmission region of the mask plate, so that the quantum dot layer positioned in the removal region is exposed, the photolytic hydrophilic ligand of the quantum dot layer in the region is subjected to photolysis, the surface characteristic of the quantum dot layer in the region is further changed, and the quantum dot layer has hydrophobicity. And the light rays emitted to the reserved area of the quantum dot layer to be patterned are blocked by the shading area of the mask plate and cannot pass through the reserved area, so that the quantum dot layer positioned in the reserved area is not exposed, and the original hydrophilicity is kept.

The developing method used in the present application is a method commonly used in the art, and the present application is not limited as long as the object of the present application can be achieved. For example, development with chloroform may be performed to remove the quantum dot layer located at the removal region. In order to obtain better film forming effect, annealing at 120 ℃ can be adopted for 15-20 min after the development is finished.

Because the quantum dot layer of the removal region has strong hydrophobicity, and the surface of the carrier transport layer has strong hydrophilicity; then, in the developing process, the quantum dots with strong hydrophobicity and the carrier transport layer with strong hydrophilicity have a strong repulsive action, so that the quantum dots in the removal region are removed, the residue problem after patterning of the quantum dots can be avoided, and the product quality and the display quality are improved.

When the quantum dot light-emitting device is prepared, a first electrode can be formed first, an electron transmission layer is formed on the first electrode, and a first quantum dot unit, a second quantum dot unit and a third quantum dot unit are formed on the electron transmission layer respectively; and then sequentially forming a hole transport layer, a hole injection layer and a second electrode to obtain the quantum dot light-emitting device. The above methods are all methods commonly used in the art, and the application is not limited.

When the quantum dot light-emitting device is prepared, a second electrode can be formed first, a hole injection layer and a hole transport layer are sequentially formed on the second electrode, and a first quantum dot unit, a second quantum dot unit and a third quantum dot unit are respectively formed on the hole transport layer; and then forming an electron transmission layer and a first electrode in sequence to obtain the quantum dot light-emitting device. The above methods are all methods commonly used in the art, and the application is not limited.

The steps included in the manufacturing method of the quantum dot light-emitting device with the inverted structure are further described with reference to the flowchart of fig. 6.

(1) Referring to fig. 6 a, the first electrode 10 is formed first.

(2) Referring to fig. 6 b, an electron transport layer 11 is formed on the first electrode 10.

(3) Referring to a diagram c in fig. 6, the electron transport layer 11 is irradiated with ultraviolet light for the first time; wherein the dosage of the first ultraviolet irradiation is 9000mj-18000mj, and the light-emitting wavelength of the adopted ultraviolet light source is 365 nm.

(4) Referring to fig. 6 d, a red quantum dot layer (RQD) is spin-coated to form a red quantum dot layer 121 to be patterned, and the red quantum dot layer 121 to be patterned includes a removal region and a retention region.

(5) Referring to a graph e in fig. 6, when the red quantum dots are exposed to ultraviolet light, the photolyzable hydrophilic ligand of the red quantum dots in the removal region is photolyzed, so that the quantum dot layer in the removal region has hydrophobicity; the photolyzable hydrophilic ligand of the red quantum dot positioned in the retention region is not subjected to photolysis, and the red quantum dot layer of the retention region has hydrophilicity. After development, the quantum dot layer located in the retention region remains, and the quantum dot layer located in the removal region is washed away, forming red quantum dot units R and an uncovered electron transport layer 11.

(6) Referring to f in fig. 6, the dark state treatment for 12 hours restores the original hydrophilicity of the electron transport layer 11, which is not covered.

(7) Referring to fig. 6, g, the electron transport layer 11 is irradiated with ultraviolet light for the second time; wherein the dose of the second ultraviolet irradiation is 8100mj-13500mj, and the light-emitting wavelength of the adopted ultraviolet light source is 365 nm.

(8) Referring to fig. 6, h, a green quantum dot layer (GQD) is spin-coated to form a green quantum dot layer 122 to be patterned, and the green quantum dot layer 122 to be patterned includes a removal region and a retention region.

(9) Referring to the diagram i in fig. 6, when the green quantum dots are exposed to ultraviolet light, the photolyzable hydrophilic ligand of the green quantum dots in the removal region is photolyzed, so that the quantum dot layer in the removal region has hydrophobicity; the photolyzable hydrophilic ligand of the green quantum dot positioned in the retention region is not subjected to photolysis, and the green quantum dot layer of the retention region has hydrophilicity. After development, the quantum dot layer in the retention region is retained, and the quantum dot layer in the removal region is washed away, thereby forming green quantum dot units G and an uncovered electron transport layer 11.

(10) Referring to j in fig. 6, the dark state treatment for 12 hours restores the original hydrophilicity of the electron transport layer 11 that is not covered.

(11) Referring to a diagram k in fig. 6, the electron transport layer 11 is irradiated with ultraviolet light for the third time; wherein the dose of the third ultraviolet irradiation is 6300mj-9000mj, and the light-emitting wavelength of the adopted ultraviolet light source is 365 nm.

(12) Referring to l diagram in fig. 6, a blue quantum dot layer (BQD) is spin-coated to form a blue quantum dot layer 123 to be patterned, and the blue quantum dot layer 123 to be patterned includes a removal region and a retention region.

(13) Referring to the diagram m in fig. 6, when the blue quantum dots are exposed to ultraviolet light, the photolyzable hydrophilic ligand of the blue quantum dots in the removal region is photolyzed, so that the quantum dot layer in the removal region has hydrophobicity; the photolyzable hydrophilic ligand of the blue quantum dot positioned in the retention region is not subjected to photolysis, and the blue quantum dot layer of the retention region has hydrophilicity. After development, the quantum dot layer in the retention region is retained, and the quantum dot layer in the removal region is washed away to form a blue quantum dot unit B.

(14) Referring to an n diagram in fig. 6, on the quantum dot layer 12 (including the red quantum dot unit R, the green quantum dot unit G, and the blue quantum dot unit B), the hole transport layer 13, the hole injection layer 14, and the second electrode 15 are sequentially formed.

The third aspect of the present application provides a display panel comprising the quantum dot light-emitting device provided by the first aspect of the present application. The display panel can be a QLED display panel, and can also be any product or component with a display function, such as a television, a digital camera, a mobile phone, a tablet personal computer and the like comprising the QLED display panel; the method has the advantages of no cross color, high resolution and good display performance.

The present application will be described in detail with reference to specific examples.

The quantum dot materials of the red quantum dots, the green quantum dots and the blue quantum dots adopted in the embodiments 1 to 5 and the comparative example 1 are all cadmium selenide/zinc sulfide core-shell structures, the original ligand is oleic acid, and the concentration is 20 mg/mL; wherein the size of the red quantum dots is 7-10nm, the size of the green quantum dots is 5-7nm, and the size of the blue quantum dots is less than 5 nm.

Example 1

Preparing red quantum dot dispersion liquid by ligand exchange: 1mL of red quantum dot octane dispersion liquid with the concentration of 20mg/mL is taken, the solvent is dried and then dispersed by chloroform, 0.33mL of ligand R-2-amino-3- (S-thiobutyl) propionic acid is added, and the mixture is stirred for 4 hours at room temperature to complete ligand exchange; then 8mL of methanol is used for precipitating the red quantum dots, and supernatant is discarded after centrifugation; dispersing red quantum dots by using 1mL of chloroform, precipitating by using 8mL of methanol, centrifuging, removing a supernatant, vacuum-drying at 80 ℃, re-dissolving red quantum dot powder in toluene, and adding a photoacid generator 2, 4-bis (trichloromethyl) -6-p-methoxystyryl-S-triazine to obtain a red quantum dot dispersion liquid with the concentration of 5mg/mL, wherein the mass percentage of the 2, 4-bis (trichloromethyl) -6-p-methoxystyryl-S-triazine in the red quantum dot dispersion liquid is 5%.

Preparing a green quantum dot dispersion by ligand exchange: the specific steps are the same as the preparation of the red quantum dot dispersion liquid by ligand exchange.

Preparing a blue quantum dot dispersion by ligand exchange: the specific steps are the same as the preparation of the red quantum dot dispersion liquid by ligand exchange.

The preparation method of the inverted bottom emission quantum dot light-emitting device comprises the following steps:

using a sol-gel method to spin-coat zinc oxide nanoparticle ethanol dispersion liquid with the mass concentration of 75mg/mL on an ITO substrate, wherein the spin-coating speed is 2000rpm, and the time is 30 s; and annealing at 180 ℃ for 1min after the spin coating is finished to form the electron transport layer.

Irradiating the electron transport layer for the first time by adopting an ultraviolet light source with the luminous wavelength of 365nm, wherein the irradiation dose is 18000 mj; and then spin-coating the red quantum dot dispersion liquid prepared by ligand exchange, wherein the spin-coating speed is 3000rpm, and the time is 30 s. After the spin coating was completed, an ultraviolet exposure of 150mj was performed. Developing by using chloroform after the exposure is finished; and annealing at 120 ℃ for 20min after the development is finished to form a red quantum dot unit, and standing in a dark state for 12 hours.

Irradiating the electron transport layer for the second time by adopting an ultraviolet light source with the luminous wavelength of 365nm, wherein the irradiation dose is 13500 mj; and then spin-coating the green quantum dot dispersion liquid prepared by ligand exchange, wherein the spin-coating speed is 3000rpm, and the time is 30 s. After the spin coating was completed, an ultraviolet exposure of 150mj was performed. Developing by using chloroform after the exposure is finished; and annealing at 120 ℃ for 20min after the development is finished to form a green quantum dot unit, and standing in a dark state for 12 hours.

Irradiating the electron transport layer for the third time by adopting an ultraviolet light source with the luminous wavelength of 365nm, wherein the irradiation dose is 9000 mj; and then spin-coating the blue quantum dot dispersion liquid prepared by ligand exchange, wherein the spin-coating speed is 3000rpm, and the time is 30 s. After the spin coating was completed, an ultraviolet exposure of 150mj was performed. Developing by using chloroform after the exposure is finished; and annealing at 120 ℃ for 20min after the development is finished to form a blue quantum dot unit.

Preparing a hole transport layer and a hole injection layer by adopting an evaporation method; and then evaporating a silver electrode for 120nm to obtain the inverted bottom emission quantum dot light-emitting device.

Example 2

The preparation of red quantum dot dispersion liquid by ligand exchange, the preparation of green quantum dot dispersion liquid by ligand exchange, and the preparation of blue quantum dot dispersion liquid by ligand exchange were the same as in example 1.

The preparation method of the positive bottom emission quantum dot light-emitting device comprises the following steps:

spin-coating a nickel oxide nanoparticle ethanol dispersion liquid with the mass concentration of 25mg/mL on an ITO substrate, wherein the spin-coating speed is 2000rpm, and the time is 30 s; and annealing at 120 ℃ for 2min after the spin coating is finished to form a hole transport layer.

Irradiating the hole transport layer for the first time by adopting an ultraviolet light source with the luminous wavelength of 365nm, wherein the irradiation dose is 18000 mj; and then spin-coating the red quantum dot dispersion liquid prepared by ligand exchange, wherein the spin-coating speed is 3000rpm, and the time is 30 s. After the spin coating was completed, an ultraviolet exposure of 150mj was performed. Developing by using chloroform after the exposure is finished; and annealing at 120 ℃ for 15min after the development is finished to form a red quantum dot unit, and standing in a dark state for 12 hours.

Irradiating the hole transport layer for the second time by adopting an ultraviolet light source with the luminous wavelength of 365nm, wherein the irradiation dose is 13500 mj; and then spin-coating the green quantum dot dispersion liquid prepared by ligand exchange, wherein the spin-coating speed is 3000rpm, and the time is 30 s. After the spin coating was completed, an ultraviolet exposure of 150mj was performed. Developing by using chloroform after the exposure is finished; and annealing at 120 ℃ for 20min after the development is finished to form a green quantum dot unit, and standing in a dark state for 12 hours.

Irradiating the hole transport layer for the third time by adopting an ultraviolet light source with the luminous wavelength of 365nm, wherein the irradiation dose is 9000 mj; and then spin-coating the blue quantum dot dispersion liquid prepared by ligand exchange, wherein the spin-coating speed is 3000rpm, and the time is 30 s. After the spin coating was completed, an ultraviolet exposure of 150mj was performed. Developing by using chloroform after the exposure is finished; and annealing at 120 ℃ for 20min after the development is finished to form a blue quantum dot unit.

Spin-coating a zinc oxide nanoparticle ethanol dispersion liquid with the mass concentration of 30mg/mL, wherein the spin-coating speed is 3000rpm, and the time is 30 s; annealing at 120 ℃ for 20min after the spin coating is finished to form an electron transport layer; and then evaporating an aluminum electrode for 120nm to obtain the positive bottom emission quantum dot light-emitting device.

Example 3

The preparation method of the positive top emission quantum dot light-emitting device comprises the following steps:

spin-coating a nickel oxide nanoparticle ethanol dispersion liquid with the mass concentration of 25mg/mL on an ITO/Ag/ITO substrate, wherein the spin-coating speed is 2000rpm, and the time is 30 s; and annealing at 120 ℃ for 2min after the spin coating is finished to form a hole transport layer.

Irradiating the hole transport layer for the first time by adopting an ultraviolet light source with the luminous wavelength of 365nm, wherein the irradiation dose is 18000 mj; and then spin-coating the red quantum dot dispersion liquid prepared by ligand exchange, wherein the spin-coating speed is 3000rpm, and the time is 30 s. After the spin coating was completed, an ultraviolet exposure of 150mj was performed. Developing by using chloroform after the exposure is finished; and annealing at 120 ℃ for 20min after the development is finished to form a red quantum dot unit, and standing in a dark state for 12 hours.

Spin-coating zinc oxide nanoparticle dispersion liquid with the mass concentration of 30mg/mL, wherein the spin-coating speed is 3000rpm and the time is 30 s; annealing at 120 ℃ for 20min after the spin coating is finished to form an electron transport layer; and sputtering an Indium Gallium Zinc Oxide (IGZO) electrode by 50nm to obtain the positive top emission quantum dot light-emitting device.

Example 4

The preparation method of the inverted bottom emission quantum dot light-emitting device is the same as that of the embodiment 1 except that the dose of the first irradiation of the ultraviolet light is 9000mj, the dose of the second irradiation of the ultraviolet light is 8100mj, and the dose of the third irradiation of the ultraviolet light is 6300 mj.

Example 5

The process for preparing an inverted bottom emission quantum dot light-emitting device was the same as example 1 except that the dose of the first irradiation of ultraviolet light was 16200mj, the dose of the second irradiation was 10800mj, and the dose of the third irradiation was 7200 mj.

Comparative example 1

And (3) spin-coating the red quantum dot dispersion liquid prepared by ligand exchange, wherein the spin-coating speed is 3000rpm, and the time is 30 s. After the spin coating was completed, an ultraviolet exposure of 150mj was performed. Developing by using chloroform after the exposure is finished; and annealing at 120 ℃ for 20min after the development is finished to form a red quantum dot unit.

And spin-coating the green quantum dot dispersion prepared by ligand exchange, wherein the spin-coating speed is 3000rpm, and the time is 30 s. After the spin coating was completed, an ultraviolet exposure of 150mj was performed. Developing by using chloroform after the exposure is finished; and annealing at 120 ℃ for 20min after the development is finished to form a green quantum dot unit.

And spin-coating the blue quantum dot dispersion liquid prepared by ligand exchange, wherein the spin-coating speed is 3000rpm, and the time is 30 s. After the spin coating was completed, an ultraviolet exposure of 150mj was performed. Developing by using chloroform after the exposure is finished; and annealing at 120 ℃ for 20min after the development is finished to form a blue quantum dot unit.

Quantum dot residue detection was performed on the quantum dot light-emitting devices prepared in examples 1 to 5 and comparative example 1, respectively, using a photoluminescence detection method, and the results of the detection are shown in table 1.

TABLE 1 Quantum dot residual detection results

From the results, it can be seen that the quantum dot residues on the carrier transport layer can be removed by the preparation method provided in embodiments 1 to 5 of the present application; however, with the preparation method provided in comparative example 1, quantum dots remained on the carrier transport layer.

It can be seen from the above embodiments that in the process of preparing the quantum dot light emitting device, the quantum dots on the surface of the carrier transport layer are removed, so that color mixing does not exist in full-color quantum dot display, and the product quality and the display quality are improved.

All the embodiments in the present specification are described in a related manner, and the same and similar parts among the embodiments may be referred to each other, and each embodiment focuses on the differences from the other embodiments.

The above description is only for the preferred embodiment of the present application and is not intended to limit the scope of the present application. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application are included in the protection scope of the present application.

Claims

1. A quantum dot light emitting device includes a carrier transport layer and a quantum dot layer;

the carrier transport layer includes a first portion, a second portion, and a third portion;

the quantum dot layer comprises a first quantum dot unit, a second quantum dot unit and a third quantum dot unit;

the first quantum dot unit is disposed on the first portion, the second quantum dot unit is disposed on the second portion, and the third quantum dot unit is disposed on the third portion;

the colors of the light emitted by the first quantum dot unit, the second quantum dot unit and the third quantum dot unit are different;

the hydrophilicity of the surface of the first portion on the side close to the first quantum dot unit, the hydrophilicity of the surface of the second portion on the side close to the second quantum dot unit, and the hydrophilicity of the surface of the third portion on the side close to the third quantum dot unit are different.

2. The quantum dot light-emitting device according to claim 1, wherein a surface of the first portion on a side close to the first quantum dot unit has a hydrophilicity higher than a surface of the second portion on a side close to the second quantum dot unit, and a surface of the second portion on a side close to the second quantum dot unit has a hydrophilicity higher than a surface of the third portion on a side close to the third quantum dot unit.

3. The quantum dot light-emitting device according to claim 1, wherein a hydroxyl group is attached to the carrier transport layer.

4. The qd-led device of claim 3, wherein the hydroxyl groups comprise a first hydroxyl group and a second hydroxyl group;

the first hydroxyl is connected to the carrier transport layer through an adsorption bond;

the second hydroxyl is connected to the carrier transport layer through a dangling bond.

5. The qd-led device of claim 4, wherein the first number of hydroxyl groups connected to the first portion is greater than the first number of hydroxyl groups connected to the second portion, and the first number of hydroxyl groups connected to the second portion is greater than the first number of hydroxyl groups connected to the third portion.

6. The qd-led device of claim 4, wherein the number of second hydroxyl groups attached to the first portion, the number of second hydroxyl groups attached to the second portion, and the number of second hydroxyl groups attached to the third portion are the same.

7. The qd-led device of claim 4, wherein the electron binding energy of the first hydroxyl group to the carrier transport layer is less than the electron binding energy of the second hydroxyl group to the carrier transport layer.

8. The quantum dot light-emitting device according to claim 1, wherein stability of the light emission quantum yield of the first quantum dot unit is larger than that of the second quantum dot unit; the stability of the luminescence quantum yield of the second quantum dot unit is greater than the stability of the luminescence quantum yield of the third quantum dot unit.

9. The quantum dot light-emitting device according to claim 1, wherein the carrier transport layer is an electron transport layer, further comprising: the quantum dot structure comprises a first electrode, a hole transport layer, a hole injection layer and a second electrode, wherein the first electrode is arranged on one side, far away from the quantum dot layer, of the electron transport layer, and the hole transport layer, the hole injection layer and the second electrode are sequentially arranged on one side, far away from the electron transport layer, of the quantum dot layer.

10. The quantum dot light-emitting device according to claim 1, wherein the carrier transport layer is a hole transport layer, further comprising: the quantum dot structure comprises a quantum dot layer, a hole injection layer, a second electrode, an electron transport layer and a first electrode, wherein the hole injection layer and the second electrode are sequentially arranged on one side, far away from the quantum dot layer, of the hole transport layer, and the electron transport layer and the first electrode are sequentially arranged on one side, far away from the hole transport layer, of the quantum dot layer.

11. The quantum dot light-emitting device according to claim 1, wherein the carrier transport layer is in direct contact with the quantum dot layer.

12. A method of fabricating a quantum dot light emitting device according to any of claims 1 to 11, comprising:

forming a carrier transport layer and a quantum dot layer;

wherein the carrier transport layer includes a first portion, a second portion, and a third portion;

13. The production method according to claim 12, wherein the hydrophilicity of the surface of the first portion on the side close to the first quantum dot unit, the hydrophilicity of the surface of the second portion on the side close to the second quantum dot unit, and the hydrophilicity of the surface of the third portion on the side close to the third quantum dot unit are made different by irradiation with ultraviolet light.

14. The method of claim 12, comprising:

carrying out first ultraviolet irradiation on the carrier transport layer;

spin coating a first quantum dot layer;

exposing and developing to pattern the first quantum dot layer to form a first quantum dot unit;

dark state treatment is carried out, so that the original hydrophilicity of the carrier transport layer which is not covered is recovered;

carrying out secondary ultraviolet irradiation on the carrier transport layer;

spin coating a second quantum dot layer;

exposing and developing to pattern the second quantum dot layer to form a second quantum dot unit;

carrying out third ultraviolet irradiation on the carrier transport layer;

spin coating a third quantum dot layer;

and exposing and developing to pattern the third quantum dot layer to form a third quantum dot unit.

15. The method for preparing a composite material according to claim 14, wherein the dose of the first irradiation of ultraviolet light is larger than the dose of the second irradiation of ultraviolet light, and the dose of the second irradiation of ultraviolet light is larger than the dose of the third irradiation of ultraviolet light.

16. A display panel comprising a qd-led device as claimed in any one of claims 1 to 11.