Method for preparing gradient band gap CIGS (copper indium gallium sulfur selenium) solar cell by solution method

Abstract

The invention provides a method for preparing a gradient band gap copper-indium-gallium-sulfur-selenium solar cell by a solution method. The method comprises the following steps: preparing a copper-indium-gallium-sulfur precursor solution; preparing a silver-indium-sulfur precursor solution; preparing a copper-indium-gallium-selenium precursor film containing a silver-indium-sulfur layer; carrying out selenylation treatment to obtain a copper indium gallium selenium sulfur absorption layer; and depositing a buffer layer, a window layer and an electrode to prepare the CIGS thin film solar cell with the gradient band gap. According to the method for preparing the gradient band gap CIGS solar cell through the solution method, the AIS intermediate layer is inserted in the precursor film spin-coating process, so that the absorption layer with the gradient band gap is obtained through selenylation, the gradient band gap is constructed while the crystal quality is improved, the long-wavelength absorption of the cell is improved, and the service life of the cell is prolonged. And finally, the device performance is improved.

Description

Technical Field

[0001] The present invention belongs to the field of application of optoelectronic device technology, and is particularly directed to preparing copper-based thin-film solar cells with high-quality gradient band gaps by a solution method, and laying a foundation for their further application and development in related optoelectronic devices. Specifically, it relates to a method for preparing gradient band gap copper indium gallium sulfur selenide solar cells by using a simple solution method intermediate intercalation layer. Background Art

[0002] With the increasing global concern about climate change, reducing carbon emissions has become a common mission for all countries. Against this grand background, the photovoltaic industry stands out with its unique advantages and becomes a key force in achieving sustainable development. Polycrystalline chalcopyrite copper indium gallium selenide (CIGS) material has excellent optoelectronic properties, including adjustable band gap, high absorption coefficient, and high stability, making it an ideal photovoltaic material in photovoltaic applications.

[0003] When preparing copper indium gallium selenide cells based on traditional vacuum technology methods, it is often necessary to construct a gradient band gap in three-step evaporation. The construction of the gradient band gap can form a built-in electric field in the copper indium gallium selenide cell absorption layer, promote the separation and transmission of carriers, and reduce the probability of carrier recombination. At the same time, it can broaden the absorption band of the absorption layer to the incident light and enhance the light utilization rate. Hydrazine is used as a solvent to prepare copper indium gallium selenide cells. Since the absorption layer is obtained directly through a one-step hot stage annealing in the process, a gradient band gap can be easily constructed in the absorption layer. However, considering the high toxicity of hydrazine solution and its extreme instability in the air, this undoubtedly limits the further large-scale development of the solution system. The use of non-hydrazine green solvent systems to prepare copper indium gallium selenide cells often requires a high-temperature selenization process. The diffusion of elements under high temperature conditions is relatively random, so the copper indium gallium selenide absorption layer obtained by high-temperature selenization is generally a flat band structure. The use of non-hydrazine solution methods to prepare copper indium gallium selenide cells has the problem of difficulty in obtaining CIGSSe films with gradient band gaps, thereby limiting the further improvement of its efficiency. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing gradient band gap copper indium gallium sulfur selenide solar cells by a solution method, aiming to solve the technical problem in the prior art that it is difficult to obtain a CIGSSe film with a gradient band gap when preparing copper indium gallium selenide cells by a non-hydrazine solution method.

[0005] To achieve the above object, the technical solution adopted by the present invention is: to provide a method for preparing a gradient bandgap copper indium gallium sulfur selenide solar cell by a solution method, comprising the following steps:

[0006] Prepare copper indium gallium sulfide precursor solution;

[0007] Prepare a silver indium sulfur precursor solution;

[0008] Preparation of a copper indium gallium selenide precursor film containing a silver indium sulfide layer;

[0009] After selenization treatment, a copper indium gallium selenide sulfur absorption layer is obtained;

[0010] A buffer layer, a window layer and an electrode are deposited to prepare a copper indium gallium selenide sulfur thin film solar cell.

[0011] Preferably, the preparation of the copper indium gallium sulfide precursor solution comprises the following steps:

[0012] Thiourea, copper acetate, indium trichloride tetrahydrate and anhydrous gallium chloride are sequentially added to a dimethylformamide solvent and stirred to dissolve, thereby obtaining a CIGS precursor solution. The molar ratio of thiourea to the sum of all metal salts is 2.5-3.

[0013] Preferably, preparing the silver indium sulfur precursor solution comprises the following steps:

[0014] Thiourea, silver chloride and indium trichloride tetrahydrate are sequentially added into dimethylformamide solvent, stirred and dissolved to obtain an AIS precursor solution, wherein the molar ratio of thiourea to the sum of all metal salts is 2.5-3.

[0015] Preferably, preparing a copper indium gallium sulfide precursor film containing a silver indium sulfide layer comprises the following steps:

[0016] First, spin-coat the copper indium gallium selenide precursor solution on the molybdenum-coated glass substrate, then anneal and dry on a hot stage, and repeat 7-9 times;

[0017] Then, the silver indium sulfide layer precursor solution is spin-coated, and hot-stage annealing and drying are performed, which is repeated twice;

[0018] Finally, the copper indium gallium selenide precursor solution is spin-coated, annealed and dried for 1-3 times to obtain a copper indium gallium selenide precursor film containing a silver indium sulfide layer.

[0019] Preferably, the precursor solution is spin-coated and annealed, with a spin-coating speed of 3000-3500 rpm and an annealing temperature of 260-290°C.

[0020] Preferably, a copper indium gallium sulfur selenide absorption layer with a gradient band gap is prepared, and a precursor film obtained by spin coating is subjected to high-temperature selenization in a rapid annealing furnace, the selenization temperature is 540-580° C., and the time is 10-15 min.

[0021] Preferably, a 50-80 nm cadmium sulfide buffer layer is deposited on the copper indium gallium selenide absorption layer with a gradient band gap by a chemical water bath method, an 80-100 nm intrinsic zinc oxide and a 200-400 nm aluminum-doped zinc oxide window layer are grown by a DC magnetron sputtering method, and a 1-1.5 μm silver top electrode is prepared by a thermal evaporation method, thereby obtaining the final copper indium gallium selenide sulfur thin film solar cell with a gradient band gap.

[0022] A copper indium gallium sulphide selenide solar cell, characterized in that it is prepared based on the steps of a method for preparing a gradient bandgap copper indium gallium sulphide selenide solar cell by a solution method as described in any one of the above items.

[0023] The method for preparing a gradient bandgap copper indium gallium sulfur selenide solar cell by a solution method provided by the present invention has the beneficial effect that: compared with the prior art, the present invention is a method for preparing a gradient bandgap copper indium gallium sulfur selenide solar cell by a solution method, using dimethylformamide as a solvent, copper acetate, silver chloride, indium trichloride tetrahydrate, anhydrous gallium chloride and thiourea as solutes to prepare CIGS and AIS precursor solutions, adjusting the AIS spin coating position to obtain a precursor film with different indium gallium gradients, and then preparing a CIGSSe thin film solar cell with a gradient bandgap through subsequent steps such as selenization. The method of inserting an AIS intermediate layer during the spin coating process of the precursor film is adopted, so as to obtain an absorption layer with a gradient bandgap by selenization, constructing a gradient bandgap while improving the crystal quality, increasing the long-wavelength absorption of the battery, and finally improving the device performance, thus opening up a simple and feasible method for preparing a high-efficiency CIGSSe battery with a gradient bandgap based on a solution method. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 : Schematic diagram of the process of preparing high-efficiency CIGSSe thin-film solar cells with gradient band gap by introducing silver indium sulfur (AIS) at different positions to prepare a precursor film, and then obtaining a CIGSSe absorption layer with a gradient band gap through selenization annealing.

[0026] Figure 2 : External quantum efficiency QE diagram of the reference cell and the CIGSSe thin-film solar cell with the optimal gradient bandgap obtained by adjusting the insertion position of silver indium sulfur (AIS) in the precursor film (a); bandgap diagram obtained based on QE fitting (b); QE ratio under negative bias and without bias (c).

[0027] Figure 3 : Capacitance-voltage curves CV graph of the reference cell and the CIGSSe thin-film solar cell with the optimal gradient bandgap obtained by adjusting the insertion position of silver indium sulfur (AIS) in the precursor film (a), the cell built-in voltage obtained by fitting the CV curve (b), and the cell depletion zone width and interface defect density obtained by the CV and DLCP curves (c). DETAILED DESCRIPTION

[0028] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0029] Please also read Figures 1 to 3 , now the method for preparing a gradient bandgap copper indium gallium sulfide selenide solar cell by a solution method provided by the present invention is described. The structure is SLG / Mo / CIGSSe / CdS / i-ZnO / ZnO:Al / Ag, which is a method for preparing a gradient bandgap copper indium gallium sulfide selenide solar cell based on a solution method. During the spin coating of the copper indium gallium selenide (CIGS) precursor solution, appropriate layers of silver indium sulfide (AIS) are introduced at different positions to prepare a precursor film, and then the precursor film is prepared by selenization annealing to obtain a high-quality CIGSSe absorption layer with a gradient bandgap, and then a CIGSSe thin film solar cell with a gradient bandgap is prepared. Specifically, the method includes the following steps:

[0030] S1. Prepare copper indium gallium sulfide precursor solution.

[0031] 2-3M thiourea (99.0%), 0.4-0.5M copper acetate (99.95%), 0.3-0.4M indium trichloride tetrahydrate (99.99%), and 0.1-0.2M anhydrous gallium chloride (99.99%) are sequentially added to a dimethylformamide solvent and stirred to dissolve, thereby obtaining a CIGS precursor solution. The molar ratio of thiourea to the sum of all metal salts is 2.5-3.

[0032] Specifically, the implementation of step 1 includes:

[0033] S1.1, add 2-3M thiourea (99.0%) into dimethylformamide solvent;

[0034] S1.2, after thiourea is completely dissolved in dimethylformamide solvent, add 0.4-0.5M copper acetate (99.95%) to the above clear solution;

[0035] S1.3, after the copper acetate is further dissolved, add 0.3-0.4M indium trichloride tetrahydrate (99.99%) to the above reaction solution;

[0036] S1.4, after the indium chloride tetrahydrate is dissolved, anhydrous gallium chloride having a concentration of 0.1-0.2M is further added to the above solution;

[0037] S1.5. After the anhydrous gallium chloride is further completely dissolved, a uniform and stable CIGS precursor solution is obtained.

[0038] S2. Prepare a silver indium sulfur precursor solution.

[0039] Sequentially add 2-3M thiourea (99.0%), 0.4-0.5M silver chloride (99.95%), and 0.4-0.5M indium trichloride tetrahydrate (99.99%) to dimethylformamide solvent, stir and dissolve, thereby obtaining an AIS precursor solution. The molar ratio of thiourea to the sum of all metal salts is 2.5-3. Specifically, the implementation of step 2 includes:

[0040] S2.1, adding 2-3M thiourea (99.0%) into dimethylformamide solvent;

[0041] S2.2, after thiourea is completely dissolved in dimethylformamide solvent, add 0.4-0.5M (99.95%) silver chloride to the above clear solution;

[0042] S2.3, after the silver chloride is further dissolved, 0.4-0.5M indium trichloride tetrahydrate (99.99%) is added to the above reaction solution;

[0043] S2.4. After the indium chloride tetrahydrate is completely dissolved, a uniform, stable and clear AIS precursor solution is obtained.

[0044] The drug to be added later needs to react after the previous raw material has reacted, and the molar ratio of thiourea to the sum of all metal salts is 3.

[0045] S3. Prepare a copper indium gallium sulfide precursor film containing a silver indium sulfide layer.

[0046] The precursor solution is spin-coated on the substrate, and then repeatedly heated and dried multiple times to obtain a copper indium gallium selenide precursor film with a silver indium sulfide layer, wherein the type of the precursor solution spin-coated each time is a copper indium gallium selenide precursor solution or a silver indium sulfide precursor solution.

[0047] Specifically, the precursor solution is spin-coated on a molybdenum-coated glass substrate (or a molybdenum film), and then placed on a hot stage for repeated heating and drying, and the process is repeated 12 times to achieve the required film thickness.

[0048] In this step, the film is repeatedly spin-coated with the precursor solution for multiple times, so that the final prepared battery can fully absorb sunlight.

[0049] The preparation steps of the copper indium gallium sulfide precursor film with a silver indium sulfide layer include: spin coating a copper indium gallium sulfide or silver indium sulfide precursor solution on a molybdenum-coated glass substrate, then heating and drying it on a hot stage, and repeating the process 12 times in total to achieve the required film thickness.

[0050] The first preparation step of the copper indium gallium sulfide precursor film including a silver indium sulfide layer comprises: spin coating a copper indium gallium sulfide precursor solution on a molybdenum-coated glass substrate, and then hot-stage annealing and drying, which is repeated 7 times, and then spin coating a silver indium sulfide precursor solution, and also hot-stage annealing and drying, which is repeated 2 times, and finally spin coating, annealing and drying a copper indium gallium selenide precursor solution 3 times;

[0051] The second preparation step of the copper indium gallium sulfide precursor film including the silver indium sulfide layer includes: spin coating a copper indium gallium selenide precursor solution on a molybdenum-coated glass substrate, and then hot-stage annealing and drying, which is repeated 8 times, and then spin coating a silver indium sulfide layer precursor solution, and also hot-stage annealing and drying, which is repeated 2 times, and finally spin coating and annealing and drying the copper indium gallium selenide precursor solution 2 times;

[0052] The third preparation step of the copper indium gallium sulfide precursor film including a silver indium sulfide layer includes: spin coating a copper indium gallium selenide precursor solution on a molybdenum-coated glass substrate, and then hot-stage annealing and drying, which is repeated 9 times; then spin coating a silver indium sulfide layer precursor solution, and also hot-stage annealing and drying, which is repeated 2 times; and finally, spin coating, annealing and drying the copper indium gallium selenide precursor solution once more.

[0053] S4. Selenization is performed in a rapid annealing furnace to obtain a copper indium gallium selenide sulfur (CIGSSe) absorption layer with a gradient band gap.

[0054] Specifically, the absorption layer is obtained by selenization in a high-temperature annealing furnace, the selenization temperature is 540-580° C., and the time is 10-15 minutes.

[0055] S5, depositing a buffer layer, a window layer and an electrode to prepare a copper indium gallium selenide sulfur thin film solar cell with a gradient band gap.

[0056] Specifically, a 50-80nm cadmium sulfide buffer layer is deposited on the copper indium gallium selenide absorption layer with a gradient band gap using a chemical water bath method, an 80-100nm intrinsic zinc oxide and a 200-400nm aluminum-doped zinc oxide window layer are grown using a DC magnetron sputtering method, and a 1-1.5μm silver top electrode is prepared using a thermal evaporation method, thereby obtaining the final copper indium gallium selenide sulfur thin film solar cell with a gradient band gap.

[0057] The present invention provides a method for preparing a gradient bandgap copper indium gallium sulfur selenide solar cell by a solution method. Compared with the prior art, the present invention uses dimethylformamide as a solvent, copper acetate, silver chloride, indium trichloride tetrahydrate, anhydrous gallium chloride and thiourea as solutes to prepare a copper indium gallium sulfur precursor solution and a silver indium sulfur precursor solution, and then obtains a copper indium gallium selenide precursor film with a silver indium sulfur layer, and then prepares a CIGSSe thin film solar cell with a gradient bandgap through subsequent steps such as selenization. The method of inserting a silver indium sulfur intermediate layer during the spin coating process of the precursor film is adopted, so as to obtain an absorption layer with a gradient bandgap by selenization, and construct a gradient bandgap while improving the crystal quality, increase the long wavelength absorption of the battery, and finally improve the device performance. The device efficiency of CIGSSe can reach 17.03%. It should be pointed out that the present invention can obtain the highest efficiency based on the dimethylformamide solvent system at present, and has opened up a simple and feasible method for preparing high-efficiency CIGSSe cells with gradient bandgap based on the solution method.

[0058] Embodiment 1,

[0059] A method for preparing a gradient bandgap copper indium gallium sulfur selenide solar cell by a solution process comprises the following steps:

[0060] S1. Prepare copper indium gallium sulfide precursor solution.

[0061] 2.486 g thiourea (CH4N2S, 99.0%); 1.047 g copper acetate (Cu(CH3COO)2·H2O, 99.95%); 1.161 g indium chloride tetrahydrate (InCl3·4H2O, 99.99%) and 0.296 g anhydrous gallium chloride (GaCl3, 99.99%) were added to 12 mL dimethylformamide solvent (C3H7NO, 98%) to prepare a stable and uniform CIGS precursor solution.

[0062] In this step, the drug to be added later needs to have reacted before the previous raw material. The molar ratio of thiourea to the sum of all metal salts is 3, so that thiourea can form complete coordination with all metals.

[0063] S2, preparing a copper indium gallium sulfide precursor film;

[0064] The preparation steps of the copper indium gallium sulfide precursor film include: spin coating the copper indium gallium selenide precursor solution on a molybdenum-coated glass substrate, and then repeatedly heating and drying it on a hot stage, repeating the process 12 times to achieve the required film thickness.

[0065] S3. After selenization treatment at a temperature of 570°C for 20 min, a copper indium gallium sulfur selenide (CIGSSe) absorption layer was obtained, which is the sample Control.

[0066] S4. Deposit a 50nm cadmium sulfide buffer layer, grow an 80nm intrinsic zinc oxide and a 300nm aluminum-doped zinc oxide window layer using a DC magnetron sputtering method, and use a thermal evaporation method to prepare a 1μm silver top electrode, thereby preparing a copper indium gallium selenide sulfur thin film solar cell, which is sample C-Control.

[0067] Example 2

[0068] A method for preparing a gradient bandgap copper indium gallium sulfur selenide solar cell by a solution process comprises the following steps:

[0069] S1. Prepare precursor solution.

[0070] 2.486 g thiourea (CH4N2S, 99.0%); 1.047 g copper acetate (Cu(CH3COO)2·H2O, 99.95%); 1.161 g indium chloride tetrahydrate (InCl3·4H2O, 99.99%) and 0.296 g anhydrous gallium chloride (GaCl3, 99.99%) were added to 12 mL dimethylformamide solvent (C3H7NO, 98%) to prepare a stable and uniform CIGS precursor solution.

[0071] In this step, the drug to be added later needs to have reacted before the previous raw material. The molar ratio of thiourea to the sum of all metal salts is 3, so that thiourea can form complete coordination with all metals.

[0072] S2. Prepare a silver indium sulfur precursor solution.

[0073] 2.486 g of thiourea (CH4N2S, 99.0%), 0.75 g of silver chloride (AgCl, 99.95%), and 1.654 g of indium chloride tetrahydrate (InCl3·4H2O, 99.99%) were sequentially added into 12 mL of dimethylformamide solvent (C3H7NO, 98%) to prepare a stable and uniform AIS precursor solution.

[0074] The chemical to be added later needs to be reacted before the previous raw material. The molar ratio of thiourea to the sum of all metal salts is 3, thereby obtaining an AIS precursor solution.

[0075] S3, preparing a copper indium gallium selenide precursor film containing two silver indium sulfide layers;

[0076] The first preparation steps of a copper indium gallium sulfide precursor film including a silver indium sulfide layer include: spin coating a copper indium gallium selenide (CIGS) precursor solution on a molybdenum-coated glass substrate, and then hot-stage annealing and drying, which is repeated 7 times, and then spin coating a silver indium sulfide precursor solution, and also hot-stage annealing and drying, which is repeated 2 times, and finally spin coating, annealing and drying the copper indium gallium selenide precursor solution 3 times.

[0077] S4, after selenization treatment, the selenization temperature is 550° C., and the time is 15 min. Thus, a copper indium gallium selenide sulfur (CIGSSe) absorption layer with a gradient band gap is obtained, which is sample Ch-EN.

[0078] S5. Deposit a 50nm cadmium sulfide buffer layer, grow an 80nm intrinsic zinc oxide and a 300nm aluminum-doped zinc oxide window layer using a DC magnetron sputtering method, and use a thermal evaporation method to prepare a 1μm silver top electrode to prepare a copper indium gallium selenide sulfur thin film solar cell, thereby preparing the final copper indium gallium selenide sulfur thin film solar cell, which is sample C-Ch-EN.

[0079] Embodiment 3,

[0080] A method for preparing a gradient bandgap copper indium gallium sulfur selenide solar cell by a solution process comprises the following steps:

[0081] S1. Prepare precursor solution.

[0082] 2.486 g thiourea (CH4N2S, 99.0%); 1.047 g copper acetate (Cu(CH3COO)2·H2O, 99.95%); 1.161 g indium chloride tetrahydrate (InCl3·4H2O, 99.99%) and 0.296 g anhydrous gallium chloride (GaCl3, 99.99%) were added to 12 mL dimethylformamide solvent (C3H7NO, 98%) to prepare a stable and uniform CIGS precursor solution.

[0083] In this step, the drug to be added later needs to have reacted before the previous raw material. The molar ratio of thiourea to the sum of all metal salts is 3, so that thiourea can form complete coordination with all metals.

[0084] S2. Prepare a silver indium sulfur precursor solution.

[0085] 2.486 g of thiourea (CH4N2S, 99.0%), 0.75 g of silver chloride (AgCl, 99.95%), and 1.654 g of indium chloride tetrahydrate (InCl3·4H2O, 99.99%) were sequentially added into 12 mL of dimethylformamide solvent (C3H7NO, 98%) to prepare a stable and uniform AIS precursor solution.

[0086] The chemical to be added later needs to be reacted before the previous raw material. The molar ratio of thiourea to the sum of all metal salts is 3, thereby obtaining an AIS precursor solution.

[0087] S3, preparing a copper indium gallium selenide precursor film containing two silver indium sulfide layers;

[0088] The second preparation steps of the copper indium gallium sulfide precursor film including a silver indium sulfide layer include: spin coating a copper indium gallium selenide precursor solution on a molybdenum-coated glass substrate, and then hot-stage annealing and drying, which is repeated 8 times; then spin coating a silver indium sulfide layer precursor solution, and also hot-stage annealing and drying, which is repeated 2 times; and finally, spin coating, annealing and drying the copper indium gallium selenide precursor solution 2 more times.

[0089] S4, after selenization treatment, the selenization temperature is 550° C., and the time is 15 min. Thus, a copper indium gallium selenide sulfur (CIGSSe) absorption layer with a gradient band gap is obtained, which is the sample Ch-NT.

[0090] S5. Deposit a 50nm cadmium sulfide buffer layer, grow an 80nm intrinsic zinc oxide and a 300nm aluminum-doped zinc oxide window layer using a DC magnetron sputtering method, and use a thermal evaporation method to prepare a 1μm silver top electrode to prepare a copper indium gallium selenide sulfur thin film solar cell, thereby preparing the final copper indium gallium selenide sulfur thin film solar cell, which is sample C-Ch-NT.

[0091] Example 4

[0092] A method for preparing a gradient bandgap copper indium gallium sulfur selenide solar cell by a solution process comprises the following steps:

[0093] S1. Prepare precursor solution.

[0094] 2.486 g thiourea (CH4N2S, 99.0%); 1.047 g copper acetate (Cu(CH3COO)2·H2O, 99.95%); 1.161 g indium chloride tetrahydrate (InCl3·4H2O, 99.99%) and 0.296 g anhydrous gallium chloride (GaCl3, 99.99%) were added to 12 mL dimethylformamide solvent (C3H7NO, 98%) to prepare a stable and uniform CIGS precursor solution.

[0095] In this step, the drug to be added later needs to have reacted before the previous raw material. The molar ratio of thiourea to the sum of all metal salts is 3, so that thiourea can form complete coordination with all metals.

[0096] S2. Prepare a silver indium sulfur precursor solution.

[0097] 2.486 g of thiourea (CH4N2S, 99.0%), 0.75 g of silver chloride (AgCl, 99.95%), and 1.654 g of indium chloride tetrahydrate (InCl3·4H2O, 99.99%) were sequentially added into 12 mL of dimethylformamide solvent (C3H7NO, 98%) to prepare a stable and uniform AIS precursor solution.

[0098] The chemical to be added later needs to be reacted before the previous raw material. The molar ratio of thiourea to the sum of all metal salts is 3, thereby obtaining an AIS precursor solution.

[0099] S3, preparing a copper indium gallium selenide precursor film containing two silver indium sulfide layers;

[0100] The second preparation steps of the copper indium gallium sulfide precursor film including a silver indium sulfide layer include: spin coating a copper indium gallium selenide precursor solution on a molybdenum-coated glass substrate, and then hot-stage annealing and drying, which is repeated 9 times; then spin coating a silver indium sulfide layer precursor solution, and also hot-stage annealing and drying, which is repeated 2 times; and finally, spin coating, annealing and drying the copper indium gallium selenide precursor solution once more.

[0101] S4, after selenization treatment at a temperature of 550° C. for 15 min, a copper indium gallium selenide sulfur (CIGSSe) absorption layer with a gradient band gap is obtained, which is sample Ch-TE.

[0102] S5. Deposit a 50nm cadmium sulfide buffer layer, grow an 80nm intrinsic zinc oxide and a 300nm aluminum-doped zinc oxide window layer using a DC magnetron sputtering method, and use a thermal evaporation method to prepare a 1μm silver top electrode to prepare a copper indium gallium selenide sulfur thin film solar cell, thereby preparing the final copper indium gallium selenide sulfur thin film solar cell, which is sample C-Ch-TE.

[0103] Data Analysis:

[0104] IV tests were performed on C-Control, C-Ch-EN, C-Ch-NT and C-Ch-TE, respectively. As shown in Table 1, compared with the reference sample, the parameters of the CIGSSe battery device with gradient band gap are improved. For the C-Ch-NT battery, the optimal device efficiency can reach 17.03%.

[0105] Table 1. Performance statistics of CIGSSe devices with different gradient band gaps

[0106]

[0107] The external quantum efficiency QE test was conducted on the reference cell (C-Control) and the CIGSSe thin film solar cell (C-Ch-NT) with the optimal gradient band gap obtained by adjusting the insertion position of silver indium sulfur (AIS) in the precursor film, and their average band gap was obtained by fitting, as shown in Figure 2. Figure 2 (a) and (b), compared with the reference sample battery C-Control, the C-Ch-NT with gradient bandgap broadens the long-wavelength absorption band, and the overall absorption is enhanced, and the average bandgap is reduced from 1.18eV to 1.15eV. At the same time, the reference battery (C-Control) and the C-Ch-NT with gradient bandgap are tested under negative bias QE. Figure 2 (c), With the increase of wavelength, the QE(-1V) / QE(0V) value is smaller for C-Ch-NT with gradient band gap.

[0108] The capacitance-voltage CV test was performed on the reference cell (C-Control) and the CIGSSe thin-film solar cell (C-Ch-NT) with the optimal gradient bandgap obtained by adjusting the insertion position of silver indium sulfur (AIS) in the precursor film, and their built-in voltage Vbi was obtained by fitting. Figure 3 With the introduction of gradient band gap, the built-in voltage of C-Ch-NT increases from 638mV to 847mV. As shown in Table 2, the depletion region width increases from 279nm to 400nm, and the interface defect state density increases from 7.91×10 15 / cm 3 Reduced to 3.9×10 15 / cm 3 .

[0109] Table 2. CV and DLCP test results of reference battery (C-Control) and C-Ch-NT battery with gradient band gap

[0110]

[0111] The present invention provides a method for preparing a copper indium gallium selenide sulfur thin film solar cell with a gradient band gap based on a solution method, wherein dimethylformamide is used as a solvent, and copper acetate, silver chloride, indium trichloride tetrahydrate, anhydrous gallium chloride and thiourea are used as solutes to prepare CIGS and AIS precursor solutions, and a precursor film with different indium gallium gradients is obtained by adjusting the AIS spin coating position, and then a CIGSSe thin film solar cell with a gradient band gap is prepared through subsequent steps such as selenization. A method of inserting an AIS intermediate layer during the spin coating process of the precursor film is adopted, so that an absorption layer with a gradient band gap is obtained by selenization, and a gradient band gap is constructed while improving the crystal quality, increasing the long-wavelength absorption of the battery, and finally improving the device performance, thereby opening up a simple and feasible method for preparing a high-efficiency CIGSSe battery with a gradient band gap based on a solution method.

[0112] Through research and development, the present invention introduces appropriate layers of silver indium sulfur (AIS) at different positions to prepare a precursor film during the spin coating of the copper indium gallium selenide precursor solution, and then obtains a high-quality CIGSSe absorption layer with a gradient band gap through selenization annealing, so that the corresponding cell performance of the CIGSSe thin film solar cell prepared based on this method is significantly improved. The present invention effectively solves the problem that it is difficult to obtain a CIGSSe film with a gradient band gap using a non-hydrazine solution method, thereby limiting the further improvement of its efficiency. At the same time, based on the solution method, the method of directly introducing a silver indium sulfur layer into the precursor film has a simple preparation process, which can further give play to the preparation advantages of the solution method and increase the possibility of large-scale solution method preparation of CIGSSe photovoltaic modules. It also has the characteristics of obtaining a CIGS absorption layer with a gradient band gap even after high-temperature selenization, thereby obtaining a higher device efficiency.

[0113] The technical solutions disclosed and proposed by the present invention can be realized by those skilled in the art by referring to the contents of this article and appropriately changing the conditions, routes and other links. Although the methods and preparation techniques of the present invention have been described by preferred embodiments, relevant technical personnel can obviously modify or re-combine the methods and technical routes described herein without departing from the content, spirit and scope of the present invention to realize the final preparation technology. It should be particularly pointed out that all similar substitutions and changes are obvious to those skilled in the art, and they are all considered to be included in the spirit, scope and content of the present invention. That is, the above is only a preferred embodiment of the present invention, and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing gradient bandgap copper indium gallium sulfur selenide solar cells by solution method, characterized in that: The following steps are involved: Prepare copper indium gallium sulfide precursor solution; Prepare a silver indium sulfur precursor solution; Preparation of a copper indium gallium selenide precursor film containing a silver indium sulfide layer; After selenization treatment, a copper indium gallium selenide sulfur absorption layer is obtained; A buffer layer, a window layer and an electrode are deposited to prepare a copper indium gallium selenide sulfur thin film solar cell.

2. The method for preparing gradient bandgap copper indium gallium sulfur selenide solar cells by solution method according to claim 1, characterized in that: The copper indium gallium sulfide precursor solution is prepared, comprising the following steps: Thiourea, copper acetate, indium trichloride tetrahydrate and anhydrous gallium chloride are sequentially added into dimethylformamide solvent and stirred to dissolve, thereby obtaining a CIGS precursor solution, wherein the molar ratio of thiourea to the sum of all metal salts is 2.5-3.

3. The method for preparing gradient bandgap copper indium gallium sulfur selenide solar cells by solution method according to claim 1, characterized in that: The preparation of the silver indium sulfur precursor solution comprises the following steps: Thiourea, silver chloride and indium trichloride tetrahydrate are sequentially added into a dimethylformamide solvent and stirred to dissolve, thereby obtaining an AIS precursor solution, wherein the molar ratio of thiourea to the sum of all metal salts is 2.5-3.

4. The method for preparing gradient bandgap copper indium gallium sulfur selenide solar cells by solution method according to claim 1, characterized in that: The method for preparing a copper indium gallium sulfide precursor film containing a silver indium sulfide layer comprises the following steps: The precursor solution is spin-coated on a molybdenum-coated glass substrate, and then placed on a hot stage for heating and drying, and the process is repeated 8-12 times; A silver indium sulfide intermediate layer is inserted during the spin coating process of the precursor film, thereby obtaining a copper indium gallium sulfide precursor film containing a silver indium sulfide layer. The precursor solution is spin coated and annealed at a spin coating speed of 3000-3500 rpm and an annealing temperature of 260-290°C.

5. The method for preparing gradient bandgap copper indium gallium sulfur selenide solar cells by solution method according to claim 2, characterized in that: The method for preparing a copper indium gallium sulfide precursor film containing a silver indium sulfide layer comprises the following steps: First, spin-coat the copper indium gallium selenide precursor solution on the molybdenum-coated glass substrate, then anneal and dry on a hot stage, and repeat 7-9 times; Then, the silver indium sulfide layer precursor solution is spin-coated, and hot-stage annealing and drying are performed, which is repeated twice; Finally, the copper indium gallium selenide precursor solution is spin-coated, annealed and dried for 1-3 times to obtain a copper indium gallium selenide precursor film containing a silver indium sulfide layer.

6. The method for preparing gradient bandgap copper indium gallium sulfur selenide solar cells by solution method according to claim 2, characterized in that: The method comprises the following steps: For the precursor film obtained by spin coating, a rapid annealing furnace is used for high-temperature selenization, the selenization temperature is 540-580°C, and the time is 10-15 minutes.

7. The method for preparing a copper indium gallium sulfur selenide solar cell with a gradient band gap by a solution method according to claim 6, characterized in that: A buffer layer, a window layer and a top electrode are deposited on the copper indium gallium selenide absorbing layer with a gradient band gap to prepare a copper indium gallium selenide sulfide thin film solar cell with a gradient band gap, comprising the following steps: A 50-80nm cadmium sulfide buffer layer is deposited on the absorption layer using a chemical water bath method, an 80-100nm intrinsic zinc oxide and a 200-400nm aluminum-doped zinc oxide window layer are grown using a DC magnetron sputtering method, and a 1-1.5μm silver top electrode is prepared using a thermal evaporation method, thereby obtaining the final copper indium gallium selenide sulfur thin film solar cell with a gradient band gap.

8. A copper indium gallium sulfur selenide solar cell, characterized in that: The method is prepared based on the steps of a solution method for preparing gradient band gap copper indium gallium sulfur selenide solar cells as described in any one of claims 1 to 7.

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