Organic solar cell with vanadium bronze as electron transport layer and preparation method thereof

Abstract

The application discloses an organic solar cell with a vanadium bronze as an electron transport layer and a preparation method thereof. The solar cell comprises, from bottom to top, an ITO substrate, a vanadium bronze electron transport layer, an organic active layer, a hole transport layer and a metal anode. The vanadium bronze electron transport layer is composed of a vanadium bronze Na x V2O5 film. The preparation method comprises the following steps: pretreating the ITO substrate, adding ammonium metavanadate and sodium acetate into a container, stirring and dropping hydrogen peroxide solution, adding polyethanolamine, performing hydrothermal reaction, cleaning, drying and annealing to obtain the vanadium bronze film, and then preparing the organic active layer, the hole transport layer and the metal anode on the vanadium bronze film to obtain the organic solar cell. The organic solar cell has excellent photoelectric performance, high cell energy efficiency and stability, and has a wide thickness control range and a good application prospect.

Description

Technical Field

[0001] This invention belongs to the field of photovoltaic devices, and relates to an organic solar cell and its preparation method, specifically involving a method using vanadium bronze (Na₂O₃). x Organic solar cells with V2O5 as the electron transport layer and their preparation methods. Background Technology

[0002] Solar energy is a green, clean, and renewable energy source. Solar cells, as an effective way to convert light energy into electrical energy, have the potential to become an important medium in future energy supply. Improving the photoelectric conversion efficiency and cell stability of organic solar cells is the ultimate goal of photovoltaic device research.

[0003] Many organic photovoltaic materials are easily corroded by atmospheric substances such as H2O and O2, leading to a rapid decline in battery life and efficiency. Embedding a thin cathode layer can effectively prevent the degradation of solar cell performance. Traditional organic polymer solar cells use LiF as a cathode interface buffer layer. However, LiF itself is an insulating material, and its thickness is generally less than 1 nm during film preparation, making it difficult to control. Increased thickness hinders electron transport. Currently, many oxides, small organic molecules, and polymer materials have been developed and applied to organic photovoltaic devices to modify the cathode interface. For example, zinc oxide (ZnO), TiO2, polyethylene oxide (PEO), and PFN-Br can all effectively modify the interface and show promising application prospects. However, the aforementioned electron transport layers are all formed by solution processing or direct vapor deposition, and each has its own drawbacks. For example, ZnO has poor stability, TiO2 has unsatisfactory electrical properties, and organic electron transport materials are difficult and expensive to prepare. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide an organic solar cell with vanadium bronze as the electron transport layer, which has excellent photoelectric performance, high battery energy efficiency and stability and low requirements for electron transport layer thickness, and a method for its preparation.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution.

[0006] An organic solar cell using vanadium bronze as the electron transport layer, the solar cell comprising, from bottom to top, an ITO substrate, a vanadium bronze electron transport layer, an organic active layer, a hole transport layer, and a metal anode, wherein the vanadium bronze electron transport layer is composed of a vanadium bronze thin film, and the vanadium bronze is Na. x V2O5, 0 < x < 2.

[0007] In the aforementioned organic solar cell with vanadium bronze as the electron transport layer, preferably, the organic donor material of the organic active layer is PNTB, the organic acceptor material is N2200, the hole transport layer is a MoO3 hole transport layer, and the metal anode is an Al anode.

[0008] As a general technical concept, the present invention also provides a method for preparing the above-mentioned organic solar cell with vanadium bronze as the electron transport layer, comprising the following steps:

[0009] (1) Growth of vanadium bronze thin films on ITO substrates

[0010] (1.1) The ITO substrate is pretreated and placed in a reaction vessel for later use;

[0011] (1.2) Add ammonium metavanadate and sodium acetate to a container, stir and add hydrogen peroxide solution dropwise, then add polyethanolamine, transfer the resulting mixture to a reaction vessel, and carry out a hydrothermal reaction at 200℃~250℃ to grow vanadium bronze precursor on the ITO substrate. After cleaning and drying, a vanadium bronze precursor film is obtained. After annealing, an ITO substrate with vanadium bronze film attached is obtained, that is, a vanadium bronze electron transport layer is formed on the ITO substrate. The thickness of the vanadium bronze electron transport layer is 1nm~10nm.

[0012] (2) An organic active layer, a hole transport layer and a metal anode were successively prepared on the electron transport layer of vanadium bronze to obtain an organic solar cell with vanadium bronze as the electron transport layer.

[0013] In the above-mentioned method for preparing an organic solar cell with vanadium bronze as the electron transport layer, preferably, in step (1.2), the molar ratio of sodium acetate to ammonium metavanadate is (0, 1)∶1, the mass ratio of hydrogen peroxide solution to ammonium metavanadate is 20~50∶1, the mass fraction of hydrogen peroxide solution is 20%~50%, and the molar ratio of polyethanolamine to ammonium metavanadate is 1~5∶1.

[0014] In the above-mentioned method for preparing organic solar cells with vanadium bronze as the electron transport layer, preferably, in step (1.2), the hydrothermal reaction time is 120h to 168h, the cleaning is performed by washing with water and ethanol 3 to 5 times each, the drying temperature is 60℃ to 80℃, the annealing temperature is 150℃ to 180℃, and the annealing time is 2h to 4h.

[0015] In the above-mentioned method for preparing an organic solar cell with vanadium bronze as the electron transport layer, preferably, in step (1.2), the molar ratio of sodium acetate to ammonium metavanadate is 1:1, the mass ratio of 30wt% hydrogen peroxide solution to ammonium metavanadate is 30:1, the molar ratio of polyethanolamine to ammonium metavanadate is 3:1, the stirring time is 4 hours, the hydrothermal reaction temperature is 220°C, the hydrothermal reaction time is 144 hours, the cleaning is performed by washing with water and ethanol three times each, the drying temperature is 60°C, the annealing temperature is 165°C, and the annealing time is 3 hours.

[0016] In the above-mentioned method for preparing organic solar cells with vanadium bronze as the electron transport layer, preferably, in step (1), the pretreatment includes cleaning, drying and ozone treatment of the ITO substrate. The cleaning refers to ultrasonically cleaning the ITO substrate with acetone, ethanol and isopropanol for 30 min to 90 min in sequence, and the drying temperature is 60℃ to 80℃.

[0017] In the above-mentioned method for preparing an organic solar cell with vanadium bronze as the electron transport layer, preferably, in step (2), the preparation process of the organic active layer is as follows: the organic donor material PNTB and the organic acceptor material N2200 are dissolved in tetrahydrofuran, wherein the mass ratio of PNTB to N2200 is 1.5 to 2.5:1, and the total concentration of PNTB and N2200 in the solution is 4 mg / mL to 8 mg / mL. The mixture is stirred at 20°C to 25°C for 8 to 12 hours. 30 to 45 minutes before spin coating, 0.5% to 3% of 1,8-diiodooctane is added to the solution, and then the mixture is spin-coated onto the vanadium bronze electron transport layer. The spin coating speed is 1000 rpm to 5000 rpm, and the spin coating time is 20 to 60 seconds. After spin coating, the mixture is annealed at 120°C to 150°C for 15 to 20 minutes to obtain the organic active layer, the thickness of which is 80 nm to 200 nm.

[0018] In the above-mentioned method for preparing organic solar cells with vanadium bronze as the electron transport layer, preferably, in step (2), the hole transport layer and the metal anode are prepared by vacuum evaporation.

[0019] In the above-mentioned method for preparing an organic solar cell with vanadium bronze as the electron transport layer, preferably, in step (2), the hole transport layer is a MoO3 hole transport layer, the metal anode is an Al anode, and the vacuum degree of the MoO3 hole transport layer and the Al anode during evaporation is <9×10⁻⁶. -4 Pa, wherein the thickness of the MoO3 hole transport layer is 1 nm to 5 nm, and the thickness of the Al anode is 100 nm to 200 nm.

[0020] Compared with the prior art, the advantages of the present invention are as follows:

[0021] (1) This invention uses vanadium bronze (Na) 0.5 Organic solar cells with ITO (I₂O₅) as the electron transport layer exhibit excellent photoelectric performance, high energy efficiency, and stability, while also having low requirements for electron transport layer thickness and a wide range of thickness control. The cell structure is ITO / Na. x The V2O5 / PNTB∶N2200 / MoO3 / Al device structure achieves an energy conversion efficiency of 8.41%, and after 30 days of storage, the energy efficiency still reaches 6.54%, with an energy retention rate of 77.76%.

[0022] (2) The preparation method of the present invention uses vanadium bronze (Na₂O₃). x The vanadium bronze Na₂O₅ (V₂O₅) replaces the traditional organic solar cathode interface material LiF, changing the traditional inorganic metal oxide electron transport layer deposition method. This eliminates problems such as difficulty in controlling the deposition rate and thickness during deposition, and reduces the impact of excessive thickness leading to severe electron transport obstruction. Because the vanadium bronze Na₂O₅ prepared by this invention… x V₂O₅ exhibits excellent electron transport properties, which can effectively improve the energy efficiency of organic solar cells, while Na… x V₂O₅ thin films are used in organic solar cells where thickness requirements are not stringent, allowing for a wide range of thickness control. Additionally, Na… x V2O5 materials also exhibit good stability, slowing down the energy decay rate of organic solar cells. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of an organic solar cell using vanadium bronze as the electron transport layer in an embodiment of the present invention.

[0024] Figure 2 The device structure of Embodiment 2 of the present invention is ITO / Na. 0.5 Efficiency degradation diagram of V2O5 / PNTB∶N2200 / MoO3 / Al solar cells. Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention. All materials and instruments used in the following embodiments are commercially available.

[0026] Example 1

[0027] An organic solar cell of the present invention using vanadium bronze as the electron transport layer, such as Figure 1As shown, this solar cell employs a flip-chip structure, comprising, from bottom to top, an ITO substrate, a vanadium bronze electron transport layer, an organic active layer, a hole transport layer, and a metal anode. The vanadium bronze electron transport layer is composed of a vanadium bronze thin film, and the vanadium bronze is Na. x V₂O₅, x is 0.33, meaning the solar cell structure in this embodiment is ITO / Na. 0.33 V2O5 / PNTB∶N2200 / MoO3 / Al.

[0028] In this embodiment, the organic donor material of the organic active layer is PNTB, the organic acceptor material is N2200, the hole transport layer is a MoO3 hole transport layer, and the metal anode is an Al anode.

[0029] A method for fabricating an organic solar cell using vanadium bronze as the electron transport layer according to this embodiment includes the following steps:

[0030] (1) Growth of vanadium bronze (Na₂O₃) on an ITO substrate x V2O5 thin film

[0031] (1.1) The ITO substrate (ITO substrate) was ultrasonically cleaned with acetone-ethanol-isopropanol for 60 min each, dried in an oven at 60°C, and treated with ozone for 1 min. The pretreated ITO substrate was then placed into a reaction vessel.

[0032] (1.2) Vanadium bronze (Na) 0.33 Preparation of V2O5 thin film: 2.34 g of ammonium metavanadate and 0.27 g of sodium acetate were weighed into a beaker according to a certain ratio. The mixture was rapidly stirred at room temperature, and 70 g of 30% hydrogen peroxide was added dropwise until completely dissolved. Then, 4.3 g of polyethanolamine was added, and the mixture was stirred evenly. The resulting solution was transferred to a hydrothermal reactor. The reactor was tightened and placed at 220℃ for 144 h to grow a rough vanadium bronze precursor layer on the ITO substrate. After natural cooling, the ITO substrate was removed, rinsed three times with deionized water to remove large particles, and then washed three times with ethanol to remove residual organic solvents. The substrate was then dried at 60℃ to obtain vanadium bronze (Na2O5). 0.33 V2O5) precursor thin film, vanadium bronze (Na) 0.33 The V2O5 precursor film was annealed at 165°C for 2.5 hours on a heating stage to obtain an ITO substrate with an attached vanadium bronze film, the thickness of which was 5 nm.

[0033] (2) The organic donor and acceptor material PNTB:N2200 was weighed at a mass ratio of 2:1 and dissolved in tetrahydrofuran at 25°C with a solution concentration of 6 mg / mL. The stirring time was 10 h. 30 min before spin coating, 1% of the solution volume of DIO (1,8-diiodooctane) was added. Spin coating was performed at 3000 rpm for 20 s and annealed at 130°C for 15 min to obtain an organic active layer of PNTB:N2200 with a thickness of about 120 nm.

[0034] (3) Transfer the sample obtained in step (2) to a vacuum of 1×10 -4 In a vacuum evaporation chamber, a 2 nm thick MoO3 hole transport layer was deposited. When the deposition thickness was < 1 nm, the deposition rate was controlled at [value missing]. When the thickness reaches 1 nm, the evaporation rate is controlled at... After completion, continue with the deposition of Al electrodes. The current was gradually increased to improve the evaporation rate, and the aluminum plating thickness was 120 nm.

[0035] After completing the above steps, vanadium bronze (Na) is obtained. 0.33 Organic solar cells using V2O5 as the electron transport layer.

[0036] Example 2

[0037] An organic solar cell of the present invention uses vanadium bronze as the electron transport layer. The solar cell employs a flip-chip structure and includes, from bottom to top, an ITO substrate, a vanadium bronze electron transport layer, an organic active layer, a hole transport layer, and a metal anode. The vanadium bronze electron transport layer is composed of a vanadium bronze thin film, and the vanadium bronze is Na. x V₂O₅, x is 0.5, meaning the solar cell structure in this embodiment is ITO / Na. 0.5 V2O5 / PNTB∶N2200 / MoO3 / Al.

[0038] In this embodiment, the organic donor material of the organic active layer is PNTB, the organic acceptor material is N2200, the hole transport layer is a MoO3 hole transport layer, and the metal anode is an Al anode.

[0039] A method for fabricating an organic solar cell using vanadium bronze as the electron transport layer according to this embodiment includes the following steps:

[0040] (1) Growth of vanadium bronze (Na₂O₃) on an ITO substrate 0.5 V2O5 thin film

[0041] (1.1) The ITO substrate was ultrasonically cleaned with acetone-ethanol-isopropanol for 60 min in sequence, dried in an oven at 60℃, and treated with ozone for 1 min. The pretreated ITO substrate was then placed into a reaction vessel.

[0042] (1.2) Vanadium bronze (Na) 0.5 Preparation of V2O5 thin film: 1.17g of ammonium metavanadate and 0.205g of sodium acetate were weighed into a beaker according to a certain ratio. The mixture was rapidly stirred at room temperature, and 35g of 30% hydrogen peroxide was added dropwise until completely dissolved. Then, 2.15g of polyethanolamine was added and stirred evenly. The resulting mixture was transferred to a hydrothermal reactor. After tightening the reactor, it was placed at 220℃ for 144h to grow a rough vanadium bronze precursor layer on the ITO substrate. After natural cooling, the ITO substrate was removed, rinsed three times with deionized water to remove large particles, and then washed three times with ethanol to remove residual organic solvents. The substrate was then dried at 60℃ to obtain vanadium bronze (Na2O5). 0.5 Vanadium bronze (Na₂O₅) precursor film. 0.5 The V2O5 precursor film was annealed at 165°C for 2.5 hours on a heating stage to obtain an ITO substrate with an attached vanadium bronze film, the thickness of which was 5 nm.

[0043] (2) The organic donor-acceptor material PNTB:N2200 was weighed at a mass ratio of 2:1 and dissolved in tetrahydrofuran at 25°C with a solution concentration of 6 mg / mL. The stirring time was 10 h. 30 min before spin coating, 1% of the solution volume of DIO (1,8-diiodooctane) was added, and the mixture was spin-coated at 3000 rpm for 20 s and annealed at 130°C for 15 min to obtain an organic active layer of PNTB:N2200 with a thickness of about 120 nm.

[0044] (3) Transfer the sample obtained in step (2) to a vacuum of 1×10 -4 In a vacuum evaporation chamber, a 2 nm thick layer of MoO3 was deposited. When the deposition thickness was < 1 nm, the deposition rate was controlled at [value missing]. When the thickness reaches 1 nm, the evaporation rate is controlled at... After completion, continue with the deposition of Al electrodes. The current was gradually increased to improve the evaporation rate, and the aluminum plating thickness was 120 nm.

[0045] After completing the above steps, vanadium bronze (Na) is obtained. 0.5 Organic solar cells using V2O5 as the electron transport layer.

[0046] Example 3

[0047] An organic solar cell of the present invention uses vanadium bronze as the electron transport layer. The solar cell employs a flip-chip structure and includes, from bottom to top, an ITO substrate, a vanadium bronze electron transport layer, an organic active layer, a hole transport layer, and a metal anode. The vanadium bronze electron transport layer is composed of a vanadium bronze thin film, and the vanadium bronze is Na. xV2O5, x is 1, that is, the solar cell structure of this embodiment is ITO / NaV2O5 / PNTB∶N2200 / MoO3 / Al.

[0048] In this embodiment, the organic donor material of the organic active layer is PNTB, the organic acceptor material is N2200, the hole transport layer is a MoO3 hole transport layer, and the metal anode is an Al anode.

[0049] A method for fabricating an organic solar cell using vanadium bronze as the electron transport layer according to this embodiment includes the following steps:

[0050] (1) Growth of vanadium bronze (NaV2O5) thin films on ITO substrates

[0051] (1.1) The ITO substrate was ultrasonically cleaned with acetone-ethanol-isopropanol for 60 min in sequence, dried in an oven at 60℃, and treated with ozone for 1 min. The pretreated ITO substrate was then placed into a reaction vessel.

[0052] (1.2) Preparation of vanadium bronze (NaV2O5) thin film: 0.585 g of ammonium metavanadate and 0.205 g of sodium acetate were weighed into a beaker according to a certain ratio. The mixture was rapidly stirred at room temperature, and 17.5 g of 30% hydrogen peroxide was added dropwise. After complete dissolution, 1.08 g of polyethanolamine was added and stirred evenly. The resulting mixture was transferred to a hydrothermal reactor. The reactor was tightened and placed at 220℃ for 144 h. After natural cooling, the ITO substrate was removed and rinsed three times with deionized water to remove large particles from the surface. Then, it was washed three times with ethanol to remove residual organic solvents. The substrate was dried at 60℃ to obtain the vanadium bronze (NaV2O5) precursor thin film. The vanadium bronze (NaV2O5) precursor thin film was annealed at 165℃ for 2.5 h on a heating stage to obtain an ITO substrate with the vanadium bronze thin film attached.

[0053] (2) The organic donor-acceptor material PNTB:N2200 was weighed at a mass ratio of 2:1 and dissolved in tetrahydrofuran at 25°C with a solution concentration of 6 mg / mL. The stirring time was 10 h. 30 min before spin coating, 1% of the solution volume of DIO (1,8-diiodooctane) was added, and the mixture was spin-coated at 3000 rpm for 20 s and annealed at 130°C for 15 min to obtain an organic active layer of PNTB:N2200 with a thickness of about 120 nm.

[0054] (3) Transfer the sample obtained in step (2) to a vacuum of 1×10 -4 In a vacuum evaporation chamber, a 2 nm thick layer of MoO3 was deposited. When the deposition thickness was < 1 nm, the deposition rate was controlled at [value missing]. When the thickness reaches 1 nm, the evaporation rate is controlled at... After completion, continue with the deposition of Al electrodes. The current was gradually increased to improve the evaporation rate, and the aluminum plating thickness was 120 nm.

[0055] After completing the above steps, an organic solar cell with vanadium bronze (NaV2O5) as the electron transport layer is obtained.

[0056] The photoelectric performance parameters of the organic solar cell devices prepared in Examples 1-3 above are shown in Table 1. As can be seen from Table 1, the organic solar cell of the present invention, using vanadium bronze as the electron transport layer, has an ITO / Na... x The V2O5 / PNTB∶N2200 / MoO3 / Al devices exhibit excellent open-circuit voltage and short-circuit current, as well as high energy efficiency.

[0057] Table 1 Examples 1-3 Vanadium Bronze (Na) x Table of photoelectric performance parameters of organic solar cells with V2O5 as the electron transport layer

[0058] Example 1 <![CDATA[Na 0.33 V2O5]]> 14.69 0.82 68.84 8.09 Example 2 <![CDATA[Na 0.5 V2O5]]> 15.06 0.82 69.50 8.41 Example 3 <![CDATA[NaV2O5]]> 14.08 0.81 66.69 7.71

[0059] Energy decay test:

[0060] Based on the vanadium bronze (Na) of Example 2 0.5 An energy decay test was conducted on an organic solar cell using V₂O₅ as the electron transport layer. The test steps are as follows:

[0061] For 30 consecutive days, the ITO / Na in Example 2 0.5 The V₂O₅ / PNTB∶N₂200 / MoO₃ / Al device was subjected to JV testing, and then the device was stored in a glove box under a high-purity argon atmosphere to obtain Na. 0.5 Performance efficiency degradation data of V2O5 devices over one month. Figure 2 The device structure is ITO / Na 0.5 The efficiency degradation diagram of V2O5 / PNTB∶N2200 / MoO3 / Al solar cells, from... Figure 2 As can be seen, the energy conversion efficiency in Example 2 reached 8.41%, and after 30 days of storage, the energy efficiency still reached 6.54%, and the energy retention rate reached 77.76%, demonstrating excellent device stability.

[0062] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the spirit and technical essence of the present invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall still fall within the protection scope of the technical solutions of the present invention.

Claims

1. An organic solar cell using vanadium bronze as the electron transport layer, characterized in that, The solar cell comprises, from bottom to top, an ITO substrate, a vanadium bronze electron transport layer, an organic active layer, a hole transport layer, and a metal anode. The vanadium bronze electron transport layer is composed of a vanadium bronze thin film, and the vanadium bronze is Na₂O₃. x V2O5, 0 < x < 2; the organic donor material of the organic active layer is PNTB, the organic acceptor material is N2200, the hole transport layer is a MoO3 hole transport layer, and the metal anode is an Al anode.

2. A method for preparing an organic solar cell with vanadium bronze as the electron transport layer as described in claim 1, characterized in that, Includes the following steps: (1) Growth of vanadium bronze thin films on ITO substrates (1.1) The ITO substrate is pretreated and placed in a reaction vessel for later use; (1.2) Add ammonium metavanadate and sodium acetate to a container, stir and add hydrogen peroxide solution dropwise, then add polyethanolamine, transfer the resulting mixture to a reaction vessel, and carry out a hydrothermal reaction at 200℃~250℃ to grow vanadium bronze precursor on the ITO substrate. After cleaning and drying, a vanadium bronze precursor film is obtained. After annealing, an ITO substrate with vanadium bronze film attached is obtained, that is, a vanadium bronze electron transport layer is formed on the ITO substrate. The thickness of the vanadium bronze electron transport layer is 1nm~10nm. (2) An organic active layer, a hole transport layer and a metal anode were successively prepared on the electron transport layer of vanadium bronze to obtain an organic solar cell with vanadium bronze as the electron transport layer.

3. The method for preparing an organic solar cell with vanadium bronze as the electron transport layer according to claim 2, characterized in that, In step (1.2), the molar ratio of sodium acetate to ammonium metavanadate is (0, 1]∶1, the mass ratio of hydrogen peroxide solution to ammonium metavanadate is 20~50∶1, the mass fraction of hydrogen peroxide solution is 20%~50%, and the molar ratio of polyethanolamine to ammonium metavanadate is 1~5∶1.

4. The method for preparing an organic solar cell with vanadium bronze as the electron transport layer according to claim 3, characterized in that, In step (1.2), the hydrothermal reaction time is 120h to 168h, the cleaning is performed by washing with water and ethanol 3 to 5 times each, the drying temperature is 60℃ to 80℃, the annealing temperature is 150℃ to 180℃, and the annealing time is 2h to 4h.

5. The method for preparing an organic solar cell with vanadium bronze as the electron transport layer according to claim 4, characterized in that, In step (1.2), the molar ratio of sodium acetate to ammonium metavanadate is 1:1, the mass fraction of hydrogen peroxide solution is 30%, and the mass ratio of hydrogen peroxide solution to ammonium metavanadate is 30:1, the molar ratio of polyethanolamine to ammonium metavanadate is 3:1, the stirring time is 4 hours, the hydrothermal reaction temperature is 220°C, the hydrothermal reaction time is 144 hours, the cleaning is performed by washing with water and ethanol three times each, the drying temperature is 60°C, the annealing temperature is 165°C, and the annealing time is 3 hours.

6. The method for preparing an organic solar cell with vanadium bronze as the electron transport layer according to any one of claims 2 to 5, characterized in that, In step (1), the pretreatment includes cleaning, drying and ozone treatment of the ITO substrate. The cleaning refers to ultrasonically cleaning the ITO substrate with acetone, ethanol and isopropanol for 30 min to 90 min in sequence. The drying temperature is 60℃ to 80℃.

7. The method for preparing an organic solar cell with vanadium bronze as the electron transport layer according to any one of claims 2 to 5, characterized in that, In step (2), the preparation process of the organic active layer is as follows: the organic donor material PNTB and the organic acceptor material N2200 are dissolved in tetrahydrofuran, wherein the mass ratio of PNTB to N2200 is 1.5 to 2.5:1, and the total concentration of PNTB and N2200 in the solution is 4 mg / mL to 8 mg / mL. The mixture is stirred at 20℃ to 25℃ for 8h to 12h. 30min to 45min before spin coating, 0.5% to 3% of 1,8-diiodooctane is added to the solution, and then the mixture is spin-coated onto the vanadium bronze electron transport layer. The spin coating speed is 1000rpm to 5000rpm, and the spin coating time is 20s to 60s. After spin coating, the mixture is annealed at 120℃ to 150℃ for 15min to 20min to obtain the organic active layer, the thickness of which is 80nm to 200nm.

8. The method for preparing an organic solar cell with vanadium bronze as the electron transport layer according to any one of claims 2 to 5, characterized in that, In step (2), the hole transport layer and the metal anode are prepared by vacuum evaporation.

9. The method for preparing an organic solar cell with vanadium bronze as the electron transport layer according to claim 8, characterized in that, In step (2), the hole transport layer is a MoO3 hole transport layer, the metal anode is an Al anode, and the vacuum degree of the MoO3 hole transport layer and the Al anode during evaporation is <9×10⁻⁶. -4 Pa, wherein the thickness of the MoO3 hole transport layer is 1 nm to 5 nm, and the thickness of the Al anode is 100 nm to 200 nm.

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