A pedot:pss / nafion composite film, a gallium arsenide-based heterojunction solar cell and a preparation method thereof

Abstract

The application belongs to the technical field of solar cells, and discloses a PEDOT:PSS / Nafion composite film, a gallium arsenide-based heterojunction solar cell and a preparation method. The solar cell comprises a back electrode, a gallium arsenide substrate, a composite layer, a window layer and a front electrode. The product is obtained by spin coating PEDOT:PSS and Nafion on the gallium arsenide substrate through a spin coating process to form the composite layer composed of the PEDOT:PSS / Nafion composite film, which can reduce the series resistance of the device, accelerate the separation and transportation of carriers, significantly improve the photoelectric conversion efficiency of the device, has high light transmittance and excellent conductivity, and the solar cell combined with the gallium arsenide substrate has higher open-circuit voltage and excellent conversion efficiency. Meanwhile, the product also has a passivation effect, improves the interface properties between the product and the substrate, reduces the recombination of carriers at the interface, and then improves the performance of the semiconductor device.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, and more specifically, to a PEDOT:PSS / Nafion composite thin film, a gallium arsenide-based heterojunction solar cell thereof, and a method for its preparation. Background Technology

[0002] The development of solar cell technology has significantly reduced the consumption of fossil fuels, contributing to environmental protection and carbon emission reduction. As one of the most mature technologies, silicon-based solar cells have been widely used in civilian applications due to their abundant resources and mature manufacturing processes. Continuous advancements in materials have led to a proliferation of solar cell devices, such as perovskite solar cells, organic solar cells, and thin-film solar cells. Among these, III-V semiconductor compounds, represented by gallium arsenide, have attracted widespread attention as battery materials. This is due to their large bandgap, which allows for good matching with the solar spectrum. Furthermore, their excellent high-temperature resistance and resistance to high-energy particle radiation make them suitable for use in concentrating photovoltaic cells and space batteries.

[0003] Even though gallium arsenide (GaAs)-based solar cells theoretically have relatively high photoelectric conversion efficiencies, their fabrication technology and high cost severely limit their widespread application. Furthermore, the fabrication of GaAs-based semiconductor solar cells faces challenges such as severe lattice mismatch between epitaxial layers, complex processes, and easy recombination of charge carriers at the interface. In summary, there is still significant room for improvement in the device performance of GaAs-based solar cells. To address this, researchers have proposed using heteromaterials such as carbon materials, polymers, and inorganic compounds as charge carrier transport layers to achieve the fabrication of high-performance heterojunction solar cells. PEDOT:PSS is a commonly used hole transport material, but it still suffers from low conductivity. Researchers typically improve its conductivity and other properties by doping PEDOT:PSS with various substances.

[0004] For example, existing technology discloses an organic solar cell with an In2Se3-doped PEDOT:PSS composite layer and its preparation method. This organic solar cell includes an anode substrate, a composite layer, an active layer, an electron transport layer, and a cathode layer stacked sequentially; the composite layer is In2Se3-doped PEDOT:PSS. The organic solar cell of this invention uses In2Se3 with high conductivity and high transmittance. First, In2Se3 has high conductivity, which can effectively improve the charge transport efficiency of PEDOT:PSS and reduce the sensitivity to film thickness. Second, In2Se3 has high transmittance, allowing the active layer to effectively utilize incident light. Finally, in this invention, In2Se3 powder is mixed with deionized water and isopropanol to form a solution, which is not only environmentally friendly but also allows it to be doped into PEDOT:PSS.

[0005] Existing technology discloses a tin-containing perovskite solar cell with AuNCs-doped PEDOT:PSS as a composite layer and its fabrication method. The invention includes an anode base, a composite layer, a tin-containing perovskite active layer, an electron transport layer, a hole blocking layer, and a cathode layer stacked sequentially. The composite layer is fabricated from AuNCs-doped PEDOT:PSS material. The introduction of AuNCs can improve the conductivity of PEDOT:PSS, thereby effectively promoting the hole extraction, transport, and collection efficiency of the device. Secondly, AuNCs-doped PEDOT:PSS can improve the interfacial interaction with the active layer, thereby reducing interfacial charge recombination. Finally, plasmonic light scattering and some near-field coupling effects of AuNCs can promote more light capture and enhance the light absorption of the perovskite. Summary of the Invention

[0006] To overcome the problems of easy recombination of charge carriers at the interface and low conductivity, resulting in low photoelectric conversion efficiency in gallium arsenide-based semiconductor solar cells described in the prior art, this invention provides a PEDOT:PSS / Nafion composite thin film.

[0007] Meanwhile, a PEDOT:PSS / Nafion composite thin film / gallium arsenide-based heterojunction solar cell is also provided.

[0008] Meanwhile, a method for preparing a PEDOT:PSS / Nafion composite thin film / gallium arsenide-based heterojunction solar cell is provided.

[0009] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0010] A PEDOT:PSS / Nafion composite film includes the following preparation steps:

[0011] Step 1: Mix PEDOT:PSS aqueous solution, ethylene glycol solution and isopropanol solution to obtain a mixed spin-coating solution;

[0012] Step 2: Spin-coat the mixed spin-coating solution onto one side of the cleaned substrate, then anneal and dry to form a film. Next, spin-coat the Nafion aqueous solution and anneal to obtain a composite layer of PEDOT:PSS / Nafion composite film.

[0013] Preferably, the thickness of the PEDOT:PSS / Nafion composite film is 85-125 nm. As a composite layer of a solar cell, within this thickness range, it can ensure that if the composite layer is too thin, it is easy to form pinholes and cause leakage current, while if the thickness is too thick, it is difficult for holes to be transmitted to the electrodes, resulting in a large resistance in the series connection of the cells. At the same time, it also has excellent light transmittance.

[0014] More preferably, the thickness of the PEDOT:PSS / Nafion composite film is 105 nm.

[0015] In step 2 of this invention, after spin coating is completed, annealing is performed, which can accelerate the evaporation of solvent and enhance the contact between the film and the substrate.

[0016] Preferably, the mass fraction of the PEDOT:PSS aqueous solution in step 1 is 1.3% to 1.7%.

[0017] Preferably, the mass fraction of the ethylene glycol solution in step 1 is 5% to 9%.

[0018] Preferably, the isopropanol solution in step 1 has a mass fraction of 0.1% to 0.3%.

[0019] Preferably, the volume ratio of the PEDOT:PSS aqueous solution, ethylene glycol solution and isopropanol solution in step 1 is 1-3:1-3:1-3.

[0020] More preferably, in step 1, the PEDOT:PSS aqueous solution has a mass fraction of 1.5%, the ethylene glycol solution has a mass fraction of 7%, the isopropanol solution has a mass fraction of 0.2%, and the volume ratio of the PEDOT:PSS aqueous solution, ethylene glycol solution, and isopropanol solution is 1:1:1.

[0021] Preferably, the mass fraction of the Nafion aqueous solution in step 2 is 3% to 7%.

[0022] More preferably, the Nafion aqueous solution in step 2 has a mass fraction of 5%.

[0023] Preferably, in step 2, the mixed spin-coating solution is first centrifuged, and then the supernatant is taken for spin-coating. The centrifugation speed is 1500-3000 rpm and the centrifugation time is 1-20 min.

[0024] More preferably, in step 2, the mixed spin-coating solution is first centrifuged, and then the supernatant is taken for spin-coating. The centrifugation speed is 2000 rpm and the centrifugation time is 15 min.

[0025] Preferably, the spin coating liquid in step 2 has a rotation speed of 1500-3000 rpm and a spin coating time of 5-25 s.

[0026] More preferably, the spin coating liquid in step 2 has a rotation speed of 2000 rpm and a spin coating time of 15 s.

[0027] Preferably, the spin coating speed of the Nafion aqueous solution in step 2 is 2000-4000 rpm, and the spin coating time is 10-60 s.

[0028] More preferably, the spin coating speed of the Nafion aqueous solution in step 2 is 3500 rpm, and the spin coating time is 40 s.

[0029] A PEDOT:PSS / Nafion composite thin film / gallium arsenide-based heterojunction solar cell includes, from bottom to top, a back electrode, a gallium arsenide substrate, a composite layer, a window layer, and a front electrode; the composite layer is a PEDOT:PSS / Nafion composite thin film prepared by the present invention, the window layer is formed around the perimeter of the surface of the composite layer, the front electrode is formed in the middle of the surface of the composite layer, and the front electrode is in partial contact with the window layer.

[0030] Preferably, the window layer is ZnO or SiN. x Any one of SiO2 or Al2O3.

[0031] Preferably, the back electrode is any single electrode or a composite electrode composed of two or more of the following: gold, silver, titanium, copper, nickel, platinum, tin oxide, antimony oxide, and aluminum doped with zinc oxide.

[0032] Preferably, the front electrode is any single electrode or a composite electrode composed of two or more of the following: gold, silver, titanium, copper, nickel, platinum, tin oxide, antimony oxide, and aluminum doped with zinc oxide.

[0033] More preferably, the front electrode is a silver front electrode. When the front electrode is a silver front electrode, the Nafion in the PEDOT:PSS / Nafion composite thin film / gallium arsenide-based heterojunction solar cell can react with silver to make the composite layer and the electrode in close contact, thereby improving the carrier transport efficiency.

[0034] A method for fabricating a PEDOT:PSS / Nafion composite thin film / gallium arsenide-based heterojunction solar cell includes the following steps:

[0035] Step 1: Deposit a back electrode on one side of the gallium arsenide substrate by vapor deposition, and anneal to obtain the back electrode / gallium arsenide substrate.

[0036] Step 2: Mix PEDOT:PSS aqueous solution, ethylene glycol solution and isopropanol solution to obtain a mixed spin-coating solution. Spin-coat the mixed spin-coating solution onto the other side of the gallium arsenide substrate from Step 1, then anneal, dry to form a film, and then spin-coat Nafion aqueous solution, anneal to obtain a composite layer of PEDOT:PSS / Nafion composite film.

[0037] Step 3: Prepare a window layer around the surface of the composite layer from Step 2;

[0038] Step four: Prepare a front electrode in the middle of the composite layer surface in step three. The front electrode is also in contact with the window layer, thus obtaining a PEDOT:PSS / Nafion composite thin film / gallium arsenide-based heterojunction solar cell.

[0039] Preferably, in step one, the gallium arsenide substrate is cleaned before and after fabricating the back electrode on the gallium arsenide substrate. The cleaning process is as follows: ultrasonic cleaning is performed sequentially with organic solvent and water, followed by drying with nitrogen gas.

[0040] More preferably, the organic solvent used in the cleaning process is acetone or ethanol.

[0041] Preferably, the mass fraction of the PEDOT:PSS aqueous solution in step two is 1.3% to 1.7%.

[0042] Preferably, the mass fraction of the ethylene glycol solution in step two is 5% to 9%.

[0043] Preferably, the isopropanol solution in step two has a mass fraction of 0.1% to 0.3%.

[0044] Preferably, the volume ratio of the PEDOT:PSS aqueous solution, ethylene glycol solution, and isopropanol solution in step two is 1-3:1-3:1-3.

[0045] Preferably, the mass fraction of the Nafion aqueous solution in step two is 3% to 7%.

[0046] Preferably, in step two, the mixed spin-coating solution is first centrifuged, and then the supernatant is taken for spin-coating. The centrifugation speed is 1500-3000 rpm, and the centrifugation time is 1-20 min.

[0047] Preferably, the spin coating liquid in step two is rotated at 1500-3000 rpm and the spin coating time is 5-25 s.

[0048] Preferably, the spin coating speed of the Nafion aqueous solution in step two is 2000-4000 rpm, and the spin coating time is 10-60 s.

[0049] Compared with the prior art, the beneficial effects of the technical solution of the present invention are:

[0050] The PEDOT:PSS / Nafion composite thin film / gallium arsenide-based heterojunction solar cell of the present invention contains a composite layer prepared from a PEDOT:PSS / Nafion composite thin film, which can reduce the series resistance of the device, accelerate the carrier separation and transport at the interface between the PEDOT:PSS thin film and the semiconductor light absorption layer, and significantly improve the photoelectric conversion efficiency of the device.

[0051] The PEDOT:PSS / Nafion composite thin film prepared by this invention has high light transmittance and excellent conductivity. When combined with a gallium arsenide substrate with a direct bandgap and wide bandgap, the resulting solar cell exhibits higher open-circuit voltage and superior conversion efficiency compared to PEDOT:PSS / gallium arsenide-based or PEDOT:PSS / silicon-based solar cells. The photoelectric conversion efficiency is improved by 27.1% to 37.5%.

[0052] The PEDOT:PSS / Nafion composite film in the solar cell prepared by this invention not only functions as a composite layer but also acts as a passivation layer for the gallium arsenide substrate, improving the interface characteristics between the gallium arsenide substrate and the composite layer, reducing carrier recombination at the interface, and thus improving the performance of the semiconductor device.

[0053] When the front electrode in a solar cell is a silver front electrode, the Nafion in the PEDOT:PSS / Nafion composite film reacts with the silver, making the composite layer in close contact with the electrode, improving the carrier transport efficiency, and thus improving the performance of the semiconductor device. Attached Figure Description

[0054] Figure 1 This is a schematic diagram of the structure of the PEDOT:PSS / Nafion composite thin film / gallium arsenide-based heterojunction solar cell of the present invention, wherein 1 is the back electrode; 2 is the gallium arsenide substrate; 3 is the composite layer; 4 is the window layer; and 5 is the front electrode.

[0055] Figure 2 The current density-voltage curve of the PEDOT:PSS / Nafion composite thin film / gallium arsenide-based heterojunction solar cell in Example 1 is shown. Detailed Implementation

[0056] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field.

[0057] Unless otherwise specified, all reagents and materials used in the following examples are commercially available.

[0058] A method for fabricating a PEDOT:PSS / Nafion composite thin film / gallium arsenide-based heterojunction solar cell includes the following steps:

[0059] Step 1: The gallium arsenide substrate 2 is ultrasonically cleaned with organic solvent and water in sequence, and then dried with nitrogen. Then, the back electrode 1 is prepared on one side of the gallium arsenide substrate 2 by vapor deposition and annealing. The back electrode 1 is then ultrasonically cleaned with organic solvent and water in sequence, and dried with nitrogen for later use.

[0060] Step two: Mix a 5%–9% (w / w) ethylene glycol solution with a 0.1%–0.3% (w / w) isopropanol solution to obtain a mixed solution. Then, dissolve a 1.3%–1.7% (w / w) PEDOT:PSS aqueous solution into this mixed solution to obtain a spin-coating mixture. The volume ratio of the PEDOT:PSS aqueous solution, ethylene glycol solution, and isopropanol solution is 1–3:1–3:1–3. Spin-coat the mixture at 1500–3000 rpm. Centrifuge at a speed of 1-20 min, take the supernatant and spin-coat it on the other side of the gallium arsenide substrate 2 in step 1 at a speed of 1500-3000 rpm for 5-25 s, then anneal, dry to form a film, and then spin-coat a Nafion aqueous solution with a mass fraction of 3%-7% at a speed of 2000-4000 rpm for 10-60 s to obtain a PEDOT:PSS / Nafion composite film with a thickness of 85-125 nm, namely composite layer 3;

[0061] Step 3: Prepare a window layer 4 around the surface of the composite layer 3 in step 2;

[0062] Step four: Prepare a front electrode 5 in the middle of the surface of the composite layer 3 in step three. The front electrode 5 is also in partial contact with the window layer 4, thus obtaining a PEDOT:PSS / Nafion composite thin film / gallium arsenide-based heterojunction solar cell.

[0063] Specifically, window layer 4 is ZnO or SiN. x One of SiO2 or Al2O3.

[0064] Specifically, the front electrode 5 is any single electrode or a composite electrode composed of two or more of the following: gold, silver, titanium, copper, nickel, platinum, tin oxide, antimony oxide, and aluminum doped with zinc oxide.

[0065] Specifically, the back electrode 1 is any single electrode or a composite electrode composed of two or more of the following: gold, silver, titanium, copper, nickel, platinum, tin oxide, antimony oxide, and aluminum doped with zinc oxide.

[0066] Example 1

[0067] A method for fabricating a PEDOT:PSS / Nafion composite thin film / gallium arsenide-based heterojunction solar cell includes the following steps:

[0068] Step 1: The gallium arsenide substrate 2 is ultrasonically cleaned with acetone and deionized water in sequence and dried with nitrogen. Then, a silver back electrode 1 is prepared on one side of the gallium arsenide substrate 2 by vapor deposition and annealing process to obtain a silver back electrode / gallium arsenide substrate. The substrate is then ultrasonically cleaned with acetone and deionized water in sequence and dried with nitrogen for later use.

[0069] Step 2: A 7% (w / w) ethylene glycol solution and a 0.2% (w / w) isopropanol solution are mixed to obtain a mixed solution. Then, a 1.5% (w / w) PEDOT:PSS aqueous solution is dissolved in the mixed solution to obtain a spin-coating mixture. The volume ratio of the PEDOT:PSS aqueous solution, ethylene glycol solution, and isopropanol solution is 1:1:1. The spin-coating mixture is centrifuged at 2000 rpm for 15 min. The supernatant is taken and spin-coated on the other side of the gallium arsenide substrate 2 from Step 1 at 2000 rpm for 15 s. After annealing and drying to form a film, a 5% (w / w) Nafion aqueous solution is spin-coated at 3500 rpm for 40 s. After annealing, a PEDOT:PSS / Nafion composite film with a thickness of 105 nm is obtained, which constitutes the composite layer 3.

[0070] Step 3: Prepare a ZnO window layer 4 around the surface of the composite layer 3 from step 2;

[0071] Step four: A silver front electrode 5 is prepared in the middle of the surface of the composite layer 3 in step three by vapor deposition and annealing. The silver front electrode 5 is also in partial contact with the ZnO window layer 4.

[0072] The PEDOT:PSS / Nafion composite thin film / gallium arsenide heterojunction solar cell prepared by the above process steps is shown in the schematic diagram below. Figure 1 As shown.

[0073] The electrical performance of the PEDOT:PSS / Nafion composite thin film / gallium arsenide heterojunction solar cell obtained in Example 1 was tested, and the results are as follows: Figure 2 As shown, the short-circuit current density of the solar cell reaches 9.55 mA / cm². 2 The open-circuit voltage reached 0.54V.

[0074] Example 2

[0075] A method for fabricating a PEDOT:PSS / Nafion composite thin film / gallium arsenide-based heterojunction solar cell includes the following steps:

[0076] Step 1: The gallium arsenide substrate is ultrasonically cleaned with acetone and deionized water in sequence and dried with nitrogen. Then, a gold back electrode 1 is prepared on one side of the gallium arsenide substrate 2 by vapor deposition and annealing process to obtain a gold back electrode / gallium arsenide substrate. The substrate is then ultrasonically cleaned with acetone and deionized water in sequence and dried with nitrogen for later use.

[0077] Step 2: A 5% (w / w) ethylene glycol solution and a 0.3% (w / w) isopropanol solution are mixed to obtain a mixed solution. Then, a 1.3% (w / w) PEDOT:PSS aqueous solution is dissolved in the mixed solution to obtain a spin-coating mixture. The volume ratio of the PEDOT:PSS aqueous solution, ethylene glycol solution, and isopropanol solution is 3:1:2. The spin-coating mixture is centrifuged at 1500 rpm for 20 min. The supernatant is taken and spin-coated on the other side of the gallium arsenide substrate 2 from Step 1 at 1500 rpm for 25 s. After annealing and drying to form a film, a 7% (w / w) Nafion aqueous solution is spin-coated at 2000 rpm for 60 s. After annealing, a PEDOT:PSS / Nafion composite film with a thickness of 85 nm is obtained, which constitutes the composite layer 3.

[0078] Step 3: Prepare SiN around the surface of composite layer 3 from step 2. x Window layer 4;

[0079] Step four: In the middle of the surface of the composite layer 3 from step three, a copper front electrode 5 is prepared by vapor deposition and annealing. The copper front electrode 5 is also combined with SiN x The window layer has four contact points.

[0080] The PEDOT:PSS / Nafion composite thin film / gallium arsenide heterojunction solar cell prepared by the above process steps is shown in the schematic diagram below. Figure 1 As shown.

[0081] Example 3

[0082] A method for fabricating a PEDOT:PSS / Nafion composite thin film / gallium arsenide-based heterojunction solar cell includes the following steps:

[0083] Step 1: The gallium arsenide substrate is ultrasonically cleaned with acetone and deionized water in sequence and dried with nitrogen. Then, a platinum back electrode 1 is prepared on one side of the gallium arsenide substrate 2 by vapor deposition and annealing process to obtain a platinum back electrode / gallium arsenide substrate. The substrate is then ultrasonically cleaned with acetone and deionized water in sequence and dried with nitrogen for later use.

[0084] Step 2: A 9% (w / w) ethylene glycol solution and a 0.1% (w / w) isopropanol solution are mixed to obtain a mixed solution. Then, a 1.7% (w / w) PEDOT:PSS aqueous solution is dissolved in the mixed solution to obtain a spin-coating mixture. The volume ratio of the PEDOT:PSS aqueous solution, ethylene glycol solution, and isopropanol solution is 2:2:3. The spin-coating mixture is centrifuged at 3000 rpm for 1 min. The supernatant is taken and spin-coated on the other side of the gallium arsenide substrate 2 from Step 1 at 3000 rpm for 5 s. After annealing and drying to form a film, a 3% (w / w) Nafion aqueous solution is spin-coated at 4000 rpm for 10 s. After annealing, a PEDOT:PSS / Nafion composite film with a thickness of 125 nm is obtained, which constitutes the composite layer 3.

[0085] Step 3: Prepare an Al2O3 window layer 4 around the surface of the composite layer 3 from step 2;

[0086] Step four: In the middle of the surface of the composite layer 3 in step three, a titanium front electrode 5 is prepared by vapor deposition and annealing. The titanium front electrode 5 is also in partial contact with the Al2O3 window layer 4.

[0087] The PEDOT:PSS / Nafion composite thin film / gallium arsenide heterojunction solar cell prepared by the above process steps is shown in the schematic diagram below. Figure 1 As shown.

[0088] Comparative Example 1

[0089] The preparation conditions of Comparative Example 1 were similar to those of Example 1, except that the composite layer 3 was PEDOT:PSS.

[0090] Comparative Example 2

[0091] The preparation conditions of Comparative Example 2 were similar to those of Example 1, except that the gallium arsenide substrate 2 was replaced with a silicon substrate.

[0092] Comparative Examples 3-6

[0093] The preparation conditions of Comparative Examples 3 to 6 were similar to those of Example 1, except that the spin coating speed and spin coating time of the spin coating mixture and Nafion aqueous solution in step two were controlled to obtain composite layers with thicknesses of 53 nm, 68 nm, 145 nm and 162 nm, respectively.

[0094] Performance testing

[0095] The electrical performance of the solar cells obtained in Examples 1-3 and Comparative Examples 1-6 was tested, and the results are shown in Table 1.

[0096] Table 1. Electrical performance of solar cells in Examples 1-3 and Comparative Examples 1-6

[0097]

[0098] As can be seen from Table 1:

[0099] The solar cells obtained in Examples 1-3 have higher open-circuit voltage and short-circuit current density, and their photoelectric conversion efficiency is improved by 27.1% to 37.5% compared with the solar cells in Comparative Examples 1-2.

[0100] Comparative Examples 3-6, by adjusting the spin coating speed and spin coating time in step two, resulted in PEDOT:PSS / Nafion composite film layers with thicknesses of 53 nm, 68 nm, 145 nm, and 162 nm, respectively. The resulting solar cells exhibited poor photoelectric conversion efficiencies, all below 6%. This indicates that the thickness of the PEDOT:PSS / Nafion composite film layer is one of the important factors affecting solar cells, and its thickness is influenced by process conditions such as the spin coating speed and spin coating time of the mixed spin coating solution and Nafion aqueous solution.

[0101] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A PEDOT:PSS / Nafion composite thin film / gallium arsenide-based heterojunction solar cell, characterized in that, The device comprises, from bottom to top, a back electrode (1), a gallium arsenide substrate (2), a composite layer (3), a window layer (4), and a front electrode (5); the composite layer (3) is a PEDOT:PSS / Nafion composite film, the window layer (4) is formed around the surface of the composite layer (3), the front electrode (5) is formed in the middle of the surface of the composite layer (3), and the front electrode (5) is in partial contact with the window layer (4); The PEDOT:PSS / Nafion composite film is prepared by the following steps: Step 1, mixing PEDOT:PSS aqueous solution, ethylene glycol solution and isopropanol solution to obtain a mixed spin-coating solution; Step 2, spin-coating the mixed spin-coating solution onto one side of a cleaned substrate, then annealing, drying to form a film, then spin-coating Nafion aqueous solution, annealing, to obtain a composite layer of PEDOT:PSS / Nafion composite film; The PEDOT:PSS aqueous solution has a mass fraction of 1.3% to 1.7%, the ethylene glycol solution has a mass fraction of 5% to 9%, the isopropanol solution has a mass fraction of 0.1% to 0.3%, and the volume ratio of the PEDOT:PSS aqueous solution, ethylene glycol solution, and isopropanol solution is 1 to 3: 1 to 3: 1 to 3. The Nafion aqueous solution in step 2 has a mass fraction of 3% to 7%. The thickness of the PEDOT:PSS / Nafion composite film is 85 nm.

2. The PEDOT:PSS / Nafion composite thin film / gallium arsenide-based heterojunction solar cell according to claim 1, characterized in that, Step 2: Centrifuge the mixed spin-coating solution, and take the supernatant for spin-coating. The centrifugation speed is 1500-3000 rpm, and the centrifugation time is 1-20 min.

3. The PEDOT:PSS / Nafion composite thin film / gallium arsenide-based heterojunction solar cell according to claim 1, characterized in that, In step 2, the spin coating speed of the mixed spin coating solution is 1500-3000 rpm, and the spin coating time is 5-25 s; the spin coating speed of the Nafion aqueous solution is 2000-4000 rpm, and the spin coating time is 10-60 s.

4. The PEDOT:PSS / Nafion composite thin film / gallium arsenide-based heterojunction solar cell according to claim 1, characterized in that, The window layer (4) is ZnO or SiN. x Any one of SiO2 or Al2O3.

5. The PEDOT:PSS / Nafion composite thin film / gallium arsenide-based heterojunction solar cell according to claim 1, characterized in that, The back electrode (1) and the front electrode (5) are any single electrode or a composite electrode composed of two or more of the following: gold, silver, titanium, copper, nickel, platinum, tin oxide, antimony oxide, and aluminum doped with zinc oxide.

6. The PEDOT:PSS / Nafion composite thin film / gallium arsenide-based heterojunction solar cell according to claim 5, characterized in that, The front electrode (5) is a silver front electrode.

7. The method for preparing the PEDOT:PSS / Nafion composite thin film / gallium arsenide-based heterojunction solar cell according to any one of claims 1 to 6, characterized in that, Includes the following steps: Step 1: Deposit back electrode (1) on one side of gallium arsenide substrate (2), anneal, and obtain back electrode / gallium arsenide substrate; Step 2: Mix PEDOT:PSS aqueous solution, ethylene glycol solution and isopropanol solution to obtain a mixed spin coating solution. Spin coat the mixed spin coating solution on the other side of the gallium arsenide substrate (2) in Step 1, then anneal, dry to form a film, and then spin coat Nafion aqueous solution, anneal to obtain a composite layer (3) of PEDOT:PSS / Nafion composite film. Step 3: Prepare a window layer (4) around the surface of the composite layer (3) in step 2; Step four: Prepare a front electrode (5) in the middle of the surface of the composite layer (3) in step three. The front electrode (5) is also in partial contact with the window layer (4) to obtain a PEDOT:PSS / Nafion composite thin film / gallium arsenide-based heterojunction solar cell.

8. The method for preparing a PEDOT:PSS / Nafion composite thin film / gallium arsenide-based heterojunction solar cell according to claim 7, characterized in that, In step two, the PEDOT:PSS aqueous solution has a mass fraction of 1.3% to 1.7%, the ethylene glycol solution has a mass fraction of 5% to 9%, and the isopropanol solution has a mass fraction of 0.1% to 0.3%. The volume ratio of the PEDOT:PSS aqueous solution, ethylene glycol solution, and isopropanol solution is 1 to 3: 1 to 3: 1 to 3. The Nafion aqueous solution has a mass fraction of 3% to 7%.

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