CN105826482A - Green-light quantum dot thin-film electroluminescence device and preparation method thereof - Google Patents

Abstract

The invention discloses a green light quantum dot thin film electroluminescent device and a preparation method thereof, comprising a sequentially stacked substrate, an anode, a hole injection layer, a hole transport layer, a green light quantum dot light-emitting layer, a green light energy transfer layer, an electronic Transport layer, electron injection layer and cathode; the thickness of the green light quantum dot light emitting layer is 8nm-15nm; the thickness of the green light energy transfer layer is 0.2nm-2nm. This green light quantum dot thin film electroluminescent device first adopts a green light quantum dot light-emitting layer with a thickness of 8nm to 15nm, so that the green light quantum dot light-emitting layer forms an incompletely continuous film, so that holes can partially pass through the green light quantum dot light-emitting layer Instead of excessive accumulation at the interface between the green light quantum dot light-emitting layer and the hole transport layer, excitons are formed on the green light energy transfer layer and then reach the green light quantum dot light-emitting layer through energy transfer to make them emit light, solving the problem of green quantum dot film The problem of high hole injection barriers in electroluminescent devices.

Description

Green light quantum dot thin film electroluminescence device and preparation method thereof

technical field

The invention relates to the field of thin film electroluminescent devices, in particular to a green light quantum dot thin film electroluminescent device and a preparation method thereof.

Background technique

Quantum dots (quantumdots, QDs) are composed of a limited number of atoms, and the three dimensions are all on the order of nanometers. Quantum dots are generally spherical or quasi-spherical, and are nanoparticles made of semiconductor materials (usually composed of IIB-VIA or IIIA-VA elements) with a stable diameter of 2-20 nm. Quantum dots are aggregates of atoms and molecules on the nanometer scale, which can be composed of a semiconductor material, such as group IIB.VIA elements (such as CdS, CdSe, CdTe, ZnSe, etc.) or group IIIA.VA elements (such as InP , InAs, etc.), can also be composed of two or more semiconductor materials. As a novel semiconductor nanomaterial, quantum dots have many unique nano-properties and can be applied as the light-emitting layer of thin-film electroluminescent devices.

However, since the work function of the transparent anode ITO commonly used in thin film electroluminescent devices is 4.8eV, which is far from the HOMO energy level (>6.0eV) of QDs, the hole injection barrier in QLED devices is generally high, requiring high However, the HOMO energy level of the commonly used hole injection materials is generally 5.2eV~6.0eV, which can basically meet the hole injection requirements for red QDs (~6.0eV). However, for green QDs (~6.5eV) and blue QDs (~6.8eV), it is difficult to meet the hole injection requirements due to the high hole injection barrier.

Contents of the invention

Based on this, it is necessary to provide a green light quantum dot thin film electroluminescence device and a preparation method thereof that can solve the problem of high hole injection barrier.

A green light quantum dot thin film electroluminescent device, comprising a substrate, an anode, a hole injection layer, a hole transport layer, a green light quantum dot light-emitting layer, a green light energy transfer layer, an electron transport layer, an electron injection layer and a cathode stacked in sequence ;

The material of the green light quantum dot light-emitting layer is green light quantum dots, and the thickness of the green light quantum dot light-emitting layer is 8nm-15nm;

The material of the green light energy transfer layer is a green light organic luminescent material, and the thickness of the green light energy transfer layer is 0.2nm-2nm.

In one embodiment, the green light quantum dots are CdSeZnS green light quantum dots with a core-shell structure, and the particle size of the CdSeZnS green light quantum dots with a core-shell structure is 6nm-15nm, wherein "CdSeZnS" is ZnS-coated CdSe.

In one embodiment, the green light organic light-emitting material is selected from tris(8-quinolinolato)aluminum, 2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1H, At least one of 5H,11H-10-(2-benzothiazolyl)-quinazino[9,9A,1GH]coumarin and tris(2-phenylpyridine)iridium.

In one embodiment, the material of the anode is ITO, FTO, AZO or IZO, and the thickness of the anode is 80nm-200nm.

In one embodiment, the material of the hole injection layer is a mixture of poly-3,4-dioxyethylenethiophene and polybenzenesulfonate, and the thickness of the hole injection layer is 20nm-40nm.

In one embodiment, the material of the hole transport layer is selected from poly(N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine) and poly(( At least one of 9,9-dioctylfluorene-2,7-diyl)-co(4,4'-(N-(4-sec-butylphenyl)diphenylamine)), the empty The thickness of the hole transport layer is 20 nm to 40 nm.

In one embodiment, the material of the electron transport layer is selected from at least one of N-arylbenzimidazole, diphenylphenanthroline, zinc oxide and titanium dioxide, and the thickness of the electron transport layer is 30nm ~60nm.

In one embodiment, the material of the electron injection layer is selected from at least one of lithium fluoride, lithium carbonate, cesium carbonate, cesium nitride, cesium chloride and cesium fluoride, and the thickness of the electron injection layer is 0.5nm ~ 5nm.

In one embodiment, the material of the cathode is aluminum, silver, magnesium, barium or calcium, and the thickness of the cathode is 80nm-150nm.

The preparation method of the above-mentioned green light quantum dot thin film electroluminescence device comprises the following steps:

providing a substrate and cleaning the substrate;

forming an anode on the cleaned substrate;

A hole injection layer, a hole transport layer, and a green quantum dot light-emitting layer are sequentially formed on the anode by a solution spin coating method, wherein the material of the green quantum dot light-emitting layer is a green quantum dot, and the green quantum dot emits light the thickness of the layer is 8 nm to 15 nm; and

A green light energy transfer layer, an electron transfer layer, an electron injection layer and a cathode are sequentially formed on the green light quantum dot light-emitting layer by a vacuum evaporation method, wherein the material of the green light energy transfer layer is a green light organic light-emitting material, The thickness of the green light energy transmission layer is 0.2nm-2nm.

This green light quantum dot thin film electroluminescent device first adopts a green light quantum dot light-emitting layer with a thickness of 8nm to 15nm, so that the green light quantum dot light-emitting layer forms an incompletely continuous film, so that holes can partially pass through the green light quantum dot light-emitting layer Instead of excessively accumulating at the interface between the green light quantum dot light-emitting layer and the hole transport layer, then insert green light energy with a lower HOMO energy level than that of the green light quantum dot light-emitting layer between the green light quantum dot light-emitting layer and the electron transport layer The transfer layer, holes are injected from the anode and then pass through the hole injection layer and the hole transport layer, and then partly pass through the green light quantum dot light-emitting layer to reach the position of the green light energy transfer layer and form excitons, and then pass through the energy transfer (ET, EnergyTransfer ) to reach the green light quantum dot light-emitting layer to make it emit light. The green light energy transfer layer is located at the interface of the green light quantum dot light-emitting layer and the electron transport layer at the same time. The thickness of the green light energy transfer layer is 0.2nm to 2nm, so that The green light energy transfer layer cannot form its own strong luminescence, does not affect the luminescence spectrum and color purity of the green quantum dot thin film electroluminescent device, and solves the problem of high hole injection barrier of the green quantum dot thin film electroluminescent device.

Description of drawings

Fig. 1 is a schematic structural view of a green light quantum dot thin film electroluminescent device according to an embodiment;

Fig. 2 is the flowchart of the preparation method of the green light quantum dot thin film electroluminescence device as shown in Fig. 1;

Fig. 3 is a comparison chart of the luminous performance of the green light quantum dot thin film electroluminescent devices prepared in Examples 1 to 4.

detailed description

The preparation method of the green light quantum dot thin film electroluminescence device will be further described in detail mainly in conjunction with the accompanying drawings and specific examples below.

The green light quantum dot thin film electroluminescence device of an embodiment as shown in Figure 1, comprises the substrate 10, anode 20, hole injection layer 30, hole transport layer 40, green light quantum dot light-emitting layer 50, green light layer stacked in sequence Energy transfer layer 60 , electron transfer layer 70 , electron injection layer 80 , and cathode 90 .

The substrate 10 is usually made of glass with high transmittance.

The material of the anode 20 is indium tin oxide (ITO), fluorine doped tin oxide (FTO), aluminum doped zinc oxide (AZO) or indium doped zinc oxide (IZO).

The thickness of the anode 20 is 80nm-200nm.

The material of the hole injection layer 30 is a mixture of poly-3,4-dioxyethylenethiophene (PEDOT) and polybenzenesulfonate (PSS). Preferably, the material of the hole injection layer 30 is a mixture of poly-3,4-dioxyethylenethiophene (PEDOT) and polybenzenesulfonate (PSS) with a mass ratio of 3:1.

The hole injection layer 30 has a thickness of 20 nm to 40 nm.

The material of the hole transport layer 40 is selected from poly(N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine) (Poly-TPD) and poly((9, At least one of 9-dioctylfluorene-2,7-diyl)-co(4,4′-(N-(4-sec-butylphenyl)diphenylamine)) (TFB).

The hole transport layer 40 has a thickness of 20 nm to 40 nm.

The material of the green light quantum dot light-emitting layer 50 is green light quantum dots. Preferably, the green light quantum dots are CdSeZnS green light quantum dots with a core-shell structure, and the particle size of the CdSeZnS green light quantum dots with a core-shell structure is 6 nm to 15 nm, wherein "CdSeZnS" is ZnS-coated CdSe. CdSeZnS green light quantum dots with core-shell structure can be purchased directly.

Preferably, the particle diameter of the CdSeZnS green light quantum dots with core-shell structure is 12.5nm.

The thickness of the green quantum dot light-emitting layer 50 is 8 nm to 15 nm, so that the green quantum dot light-emitting layer 50 is an incomplete continuous film, so that holes can partly pass through the green quantum dot light-emitting layer 50 without forming a gap between the green quantum dot light-emitting layer 50 and the hole. Excess accumulation at the hole transport layer 40 interface.

The material of the green light energy transfer layer 60 is a green light organic light emitting material. Specifically, the green organic luminescent material is selected from tris(8-hydroxyquinoline)aluminum (Alq3), 2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1H,5H, 11H-10-(2-Benzothiazolyl)-quinazino[9,9A,1GH]coumarin (C545) and tris(2-phenylpyridine)iridium(III)(Ir(ppy) ₃ ) at least one of the

The thickness of the green light energy transfer layer 60 is 0.2nm-2nm, so that the green light energy transfer layer 60 cannot form its own strong light emission, and does not affect the light emission spectrum and color purity of the green light quantum dot light emitting layer 50 .

The material of the electron transport layer 70 is at least one selected from N-arylbenzimidazole (TPBi), diphenylphenanthroline (Bphen), zinc oxide (ZnO) and titanium dioxide (TiO ₂ ).

The electron transport layer 70 has a thickness of 30 nm to 60 nm.

The material of the electron injection layer 80 is selected from lithium fluoride (LiF), lithium carbonate (Li ₂ CO ₃ ), cesium carbonate (Cs ₂ CO ₃ ), cesium nitride (CsN ₃ ), cesium chloride (CsCl) and fluoride At least one of cesium (CsF).

The electron injection layer 80 has a thickness of 0.5 nm to 5 nm.

The material of the cathode 90 is aluminum (Al), silver (Ag), magnesium (Mg), barium (Ba), or calcium (Ca).

The thickness of the cathode 90 is 80 nm to 150 nm.

This green light quantum dot thin film electroluminescent device first adopts a green light quantum dot light-emitting layer 50 with a thickness of 8nm-15nm, so that the green light quantum dot light-emitting layer 50 forms an incomplete continuous film, so that holes can partially pass through the green light quantum dots The light-emitting layer 50 does not accumulate too much at the interface between the green light quantum dot light-emitting layer 50 and the hole transport layer 40, and then inserts the HOMO energy level relative to the HOMO of the green light quantum dot light-emitting layer 50 between the green light quantum dot light-emitting layer 50 and the electron transport layer 70. In the green light energy transfer layer 60 with a lower energy level, after the holes are injected from the anode 20 and pass through the hole injection layer 30 and the hole transport layer 40, they can partially pass through the green quantum dot light-emitting layer 50 to reach the green light energy transfer layer 60. position and form excitons, and then reach the green quantum dot light-emitting layer 50 to emit light through energy transfer (ET, EnergyTransfer). interface, the thickness of the green light energy transfer layer 60 is 0.2 nm to 2 nm, so that the green light energy transfer layer 60 cannot form its own strong light emission, and does not affect the light emission spectrum and color purity of the green quantum dot thin film electroluminescent device. The invention solves the problem of high hole injection potential barrier of the green light quantum dot thin film electroluminescent device.

The preparation method of the above-mentioned green light quantum dot thin film electroluminescent device as shown in Figure 2 comprises the following steps:

S10 , providing a substrate 10 and cleaning the substrate 10 .

The substrate 10 is usually made of glass with high transmittance.

The operation of cleaning the substrate 10 is as follows: the substrate 10 is ultrasonically treated with detergent, acetone, ethanol and isopropanol for 15 minutes respectively.

S20 , forming an anode 20 on the cleaned substrate 10 obtained in S10 .

The material of the anode 20 is indium tin oxide (ITO), fluorine doped tin oxide (FTO), aluminum doped zinc oxide (AZO) or indium doped zinc oxide (IZO).

The thickness of the anode 20 is 80nm-200nm.

In the operation of forming the anode 20 on the cleaned substrate obtained in S10, the formation method of the anode 20 includes evaporation, spraying, sputtering, electrochemical evaporation deposition, electrochemical methods, etc., preferably sputtering.

S20 also includes the operation of ultrasonically treating the substrate 10 formed with the anode 20 with detergent, acetone, ethanol and isopropanol in sequence for 15 minutes, and then performing UV-ozone treatment for 15 minutes.

S30 , sequentially forming a hole injection layer 30 , a hole transport layer 40 and a green quantum dot light emitting layer 50 on the anode 20 formed in S20 by a solution spin coating method.

The material of the hole injection layer 30 is a mixture of poly-3,4-dioxyethylenethiophene (PEDOT) and polybenzenesulfonate (PSS). Preferably, the material of the hole injection layer 30 is a mixture of poly-3,4-dioxyethylenethiophene (PEDOT) and polybenzenesulfonate (PSS) with a mass ratio of 3:1.

The hole injection layer 30 has a thickness of 20 nm to 40 nm.

The material of the hole transport layer 40 is selected from poly(N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine) (Poly-TPD) and poly((9, At least one of 9-dioctylfluorene-2,7-diyl)-co(4,4′-(N-(4-sec-butylphenyl)diphenylamine)) (TFB).

The hole transport layer 40 has a thickness of 20 nm to 40 nm.

The material of the green light quantum dot light-emitting layer 50 is green light quantum dots. Preferably, the green light quantum dots are CdSeZnS green light quantum dots with a core-shell structure, and the particle size of the CdSeZnS green light quantum dots with a core-shell structure is 6 nm to 15 nm, wherein "CdSeZnS" is ZnS-coated CdSe. CdSeZnS green light quantum dots with core-shell structure can be purchased directly.

Preferably, the particle diameter of the CdSeZnS green light quantum dots with core-shell structure is 12.5nm.

The thickness of the green quantum dot light-emitting layer 50 is 8 nm to 15 nm, so that the green quantum dot light-emitting layer 50 is an incomplete continuous film, so that holes can partly pass through the green quantum dot light-emitting layer 50 without forming a gap between the green quantum dot light-emitting layer 50 and the hole. Excess accumulation at the hole transport layer 40 interface.

S40 , sequentially forming a green light energy transfer layer 60 , an electron transfer layer 70 , an electron injection layer 80 and a cathode 90 on the green quantum dot light-emitting layer 50 formed in S30 by vacuum evaporation.

The material of the green light energy transfer layer 60 is a green light organic light emitting material. Specifically, the green organic luminescent material is selected from tris(8-hydroxyquinoline)aluminum (Alq3), 2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1H,5H, 11H-10-(2-Benzothiazolyl)-quinazino[9,9A,1GH]coumarin (C545) and tris(2-phenylpyridine)iridium(III)(Ir(ppy) ₃ ) at least one of the

The thickness of the green light energy transfer layer 60 is 0.2nm-2nm, so that the green light energy transfer layer 60 cannot form its own strong light emission, and does not affect the light emission spectrum and color purity of the green light quantum dot light emitting layer 50 .

The material of the electron transport layer 70 is at least one selected from N-arylbenzimidazole (TPBi), diphenylphenanthroline (Bphen), zinc oxide (ZnO) and titanium dioxide (TiO ₂ ).

The electron transport layer 70 has a thickness of 30 nm to 60 nm.

The material of the electron injection layer 80 is selected from lithium fluoride (LiF), lithium carbonate (Li ₂ CO ₃ ), cesium carbonate (Cs ₂ CO ₃ ), cesium nitride (CsN ₃ ), cesium chloride (CsCl) and fluoride At least one of cesium (CsF).

The electron injection layer 80 has a thickness of 0.5 nm to 5 nm.

The material of the cathode 90 is aluminum (Al), silver (Ag), magnesium (Mg), barium (Ba), or calcium (Ca).

The thickness of the cathode 90 is 80 nm to 150 nm.

The preparation method of the green light quantum dot thin film electroluminescent device has simple process and convenient operation, and is applicable to the preparation of the green light quantum dot thin film electroluminescent device.

The following are specific examples.

Example 1

First, the glass substrate was ultrasonically treated with detergent, acetone, ethanol and isopropanol for 15 min each. Then sputter a layer of ITO conductive film with a thickness of 150nm on the glass substrate, and then perform UV-ozone treatment for 15min.

Then, the solution spin coating method was used to spin the mixture of PEDOT and PSS with a mass ratio of 3:1 to prepare the hole injection layer, the rotation speed was 5000 rpm, annealed at 150 ° C for 30 min, and the thickness of the hole injection layer was 20 nm. Then spin-coat 18 mg/mL poly-TPD in chlorobenzene solution to prepare a hole transport layer at a rotation speed of 3000 rpm, anneal at 110° C. for 60 min, and have a thickness of 40 nm. Then prepare the green light quantum dot light-emitting layer, using 7mg/mL green light CdSeZnS quantum dot toluene solution, rotating speed 2000rpm, annealing at 150°C for 30min, with a thickness of 12nm, to obtain a semi-finished product.

Afterwards, the semi-finished product was transferred to a high-vacuum chamber with a pressure of 10 ^-4 Pa, and 0.5nm Alq ₃ was sequentially deposited as the green light energy transfer layer, 30nm TPBi as the electron transfer layer, and 1nm LiF as the green light energy transfer layer by vacuum evaporation. The electron injection layer, and finally vacuum-evaporated 100nm Al as the cathode, to obtain the required green light quantum dot thin film electroluminescence device.

Example 2

First, the glass substrate was ultrasonically treated with detergent, acetone, ethanol and isopropanol for 15 min each. Then sputter a layer of ITO conductive film with a thickness of 150nm on the glass substrate, and then perform UV-ozone treatment for 15min.

Next, the solution spin coating method was used to spin a mixture of PEDOT and PSS with a mass ratio of 3:1 to prepare a hole injection layer at a rotation speed of 5000 rpm, annealing at 150° C. for 30 min, and a thickness of 20 nm. Then spin-coat 18 mg/mL poly-TPD in chlorobenzene solution to prepare a hole transport layer at a rotation speed of 3000 rpm, anneal at 110° C. for 60 min, and have a thickness of 40 nm. Then prepare the green light quantum dot light-emitting layer, using 5mg/mL green light CdSeZnS quantum dot toluene solution, rotating speed 2000rpm, annealing at 150°C for 30min, with a thickness of 8nm, to obtain a semi-finished product.

Afterwards, the semi-finished product was transferred to a high vacuum chamber with a pressure of 10 ^-4 Pa, and 1.8nm C545 was sequentially deposited as the green light energy transfer layer, 30nm TPBi as the electron transfer layer, and 1nm LiF as the electron transfer layer by vacuum evaporation. Inject the layer, and finally vacuum-deposit 100nm Al as the cathode to obtain the required green light quantum dot thin film electroluminescent device.

Example 3

First, the glass substrate was ultrasonically treated with detergent, acetone, ethanol and isopropanol for 15 min each. Then sputter a layer of ITO conductive film with a thickness of 150nm on the glass substrate, and then perform UV-ozone treatment for 15min.

Next, the solution spin coating method was used to spin a mixture of PEDOT and PSS with a mass ratio of 3:1 to prepare a hole injection layer at a rotation speed of 5000 rpm, annealing at 150° C. for 30 min, and a thickness of 20 nm. Then spin-coat 18 mg/mL poly-TPD in chlorobenzene solution to prepare a hole transport layer at a rotation speed of 3000 rpm, anneal at 110° C. for 60 min, and have a thickness of 40 nm. Then prepare the green light quantum dot light-emitting layer, using 7mg/mL green light CdSeZnS quantum dot toluene solution, rotating speed 2000rpm, annealing at 150°C for 30min, with a thickness of 12nm, to obtain a semi-finished product.

Afterwards, the semi-finished product was transferred to a high-vacuum chamber with a pressure of 10 ^-4 Pa, and 0.2nm Ir(ppy) ₃ was sequentially deposited by vacuum evaporation as the green light energy transfer layer, 30nm TPBi as the electron transfer layer, and 1nm LiF is used as the electron injection layer, and finally 100nm Al is vacuum-deposited as the cathode to obtain the required green light quantum dot thin film electroluminescent device.

Example 4

Example 4 The process of preparing a green quantum dot thin film electroluminescent device is basically the same as that of Example 1, the only difference being that the thickness of the green quantum dot light-emitting layer in Example 4 is 15 nm.

Luminescence tests were performed on the green light quantum dot thin film electroluminescent devices prepared in Examples 1 to 4, and FIG. 3 was obtained.

It can be seen from FIG. 3 that the green light quantum dot thin film electroluminescent devices prepared in Examples 1 to 4 all have good luminous properties.

The above-mentioned embodiments only express several implementation modes of the present invention, and the description thereof is relatively specific and detailed, but should not be construed as limiting the patent scope of the present invention. It should be pointed out that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent for the present invention should be based on the appended claims.

Claims (10)

1. A green light quantum dot thin film electroluminescence device, is characterized in that, comprises successively stacked substrate, anode, hole injection layer, hole transport layer, green light quantum dot light-emitting layer, green light energy transfer layer, electron transport layer , an electron injection layer and a cathode; The material of the green light quantum dot light-emitting layer is green light quantum dots, and the thickness of the green light quantum dot light-emitting layer is 8nm-15nm; The material of the green light energy transfer layer is a green light organic luminescent material, and the thickness of the green light energy transfer layer is 0.2nm-2nm. 2. The green light quantum dot thin film electroluminescent device according to claim 1, wherein the green light quantum dot is a CdSeZnS green light quantum dot of a core-shell structure, and the particle diameter of the CdSeZnS green light quantum dot of the core-shell structure is 6nm to 15nm, wherein "CdSeZnS" is ZnS-coated CdSe. 3. The green light quantum dot thin film electroluminescent device according to claim 1, wherein the green light organic luminescent material is selected from three (8-hydroxyquinoline) aluminum, 2,3,6,7-tetra Hydrogen-1,1,7,7-tetramethyl-1H,5H,11H-10-(2-benzothiazolyl)-quinazino[9,9A,1GH]coumarin and tris(2-phenyl At least one of the base pyridine) iridium. 4 . The green light quantum dot thin film electroluminescent device according to claim 1 , wherein the material of the anode is ITO, FTO, AZO or IZO, and the thickness of the anode is 80nm-200nm. 5. green light quantum dot thin film electroluminescent device according to claim 1, is characterized in that, the material of described hole injection layer is the mixture of poly 3,4-dioxyethylene thiophene and polybenzene sulfonate, so The thickness of the hole injection layer is 20nm-40nm. 6. The green light quantum dot thin film electroluminescent device according to claim 1, wherein the material of the hole transport layer is selected from poly(N,N'-bis(4-butylphenyl)-N , N'-bis(phenyl)benzidine) and poly((9,9-dioctylfluorene-2,7-diyl)-co(4,4'-(N-(4-sec-butyl At least one of phenyl)diphenylamine)), the thickness of the hole transport layer is 20nm-40nm. 7. green light quantum dot thin film electroluminescent device according to claim 1, is characterized in that, the material of described electron transport layer is selected from N-arylbenzimidazole, diphenyl-phenanthroline, zinc oxide and At least one of titanium dioxide, the thickness of the electron transport layer is 30nm-60nm. 8. green light quantum dot thin film electroluminescent device according to claim 1, is characterized in that, the material of described electron injection layer is selected from lithium fluoride, lithium carbonate, cesium carbonate, cesium nitride, cesium chloride and fluorine At least one of cesium chloride, the thickness of the electron injection layer is 0.5nm-5nm. 9 . The green light quantum dot thin film electroluminescent device according to claim 1 , wherein the material of the cathode is aluminum, silver, magnesium, barium or calcium, and the thickness of the cathode is 80 nm to 150 nm. 10. The preparation method of the green light quantum dot thin film electroluminescent device according to any one of claims 1 to 9, characterized in that it comprises the steps of: providing a substrate and cleaning the substrate; forming an anode on the cleaned substrate; A hole injection layer, a hole transport layer, and a green quantum dot light-emitting layer are sequentially formed on the anode by a solution spin coating method, wherein the material of the green quantum dot light-emitting layer is a green quantum dot, and the green quantum dot emits light the thickness of the layer is 8 nm to 15 nm; and A green light energy transfer layer, an electron transfer layer, an electron injection layer and a cathode are sequentially formed on the green light quantum dot light-emitting layer by a vacuum evaporation method, wherein the material of the green light energy transfer layer is a green light organic light-emitting material, The thickness of the green light energy transmission layer is 0.2nm-2nm.