A copper-zinc-tin-sulfur / selenium thin film, its preparation method based on alcohol solvents, and its application.

Abstract

This invention relates to the field of battery thin film technology, and more particularly to a copper-zinc-tin-sulfur / selenium thin film and its preparation method and application based on alcohol solvents. The preparation method involves completely dissolving copper nitrate, zinc acetate, and tin tetrachloride in a mixed solvent to obtain a clear precursor solution, followed by high-temperature selenization to obtain the copper-zinc-tin-selenium thin film. The precursor solution is prepared by dissolving a mixture of copper nitrate and zinc acetate in a mixed solvent of ethylene glycol and ethanol, stirring until completely dissolved to obtain a clear mixed solution; adding tin tetrachloride to the obtained mixed solution in an air- and moisture-free environment, and heating at 40–70°C to dissolve, thus obtaining the precursor solution. This invention overcomes the problem of metal salt solutes being difficult to dissolve in mixed alcohol solvents by dissolving copper nitrate, zinc acetate, and tin tetrachloride in a specific order, achieving a clear, transparent, and stable solution in a shorter time, thus enabling the preparation of effective copper-zinc-tin-selenium thin-film solar cells.

Description

Technical Field

[0001] This invention relates to the field of battery thin film technology, and in particular to a copper-zinc-tin-sulfur / selenium thin film and its preparation method and application based on alcohol solvents. Background Technology

[0002] With scientific progress and the rapid development of science and technology, the demand for energy in human production and life has increased dramatically. Traditional fossil fuel energy has required the extensive exploitation of Earth's resources, leading not only to increasing energy scarcity but also causing irreparable pollution to the ecological environment. Therefore, finding sustainable and clean energy sources is urgently needed. Solar energy is the most abundant, inexpensive, and inexhaustible energy source on Earth. Converting solar energy into electricity through solar cells can benefit human society for a long time. Currently, various types of solar cells have been developed, such as commercially mature crystalline silicon solar cells, gallium arsenide, cadmium telluride, and copper indium gallium selenide solar cells, as well as various new types of solar cells still in the research stage, such as perovskite, copper zinc tin sulfide selenide, and organic solar cells. Among them, copper zinc tin sulfide / selenide thin-film solar cells have a wide band gap range (approximately 1.0–1.5 eV) and a high absorption coefficient (>10). 4 cm -1 Cu₂ZnSn(S,Se)₄ (CZTSSe) solar cells contain non-toxic elements abundant in the Earth's crust, making them an ideal material for solar cells. Furthermore, theoretical calculations indicate that the theoretical efficiency of this type of solar cell can reach as high as 32.4%. In conclusion, Cu₂ZnSn(S,Se)₄ (CZTSSe) solar cells have broad application prospects and social value.

[0003] Currently, the preparation methods for CZTSSe thin films can be mainly divided into vacuum methods and non-vacuum methods. Vacuum methods mainly include thermal evaporation and magnetron sputtering. Non-vacuum methods are mainly solution methods, which have been widely used and rapidly developed due to their convenient operation and low preparation cost. The highest efficiency of CZTSSe thin film solar cells to date, 13.0% (Gong, Y., Zhu, Q., Li, B. et al. Nat Energy 7, 966–977 (2022).), was prepared by solution methods.

[0004] Currently, commonly used solvents in solution preparation include dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), ethanolamine, ethylenediamine, etc. These toxic solvents are highly corrosive, and improper operation can cause serious harm to the body. In addition, the waste liquid generated by the experiment causes serious environmental pollution. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a copper-zinc-tin precursor solution prepared by an environmentally friendly mixed solvent of ethylene glycol and ethanol, which has good stability, wettability and permeability;

[0007] Accordingly, the present invention also provides a method for preparing copper-zinc-tin-sulfur / selenium thin films, which overcomes the technical problem of copper, zinc, and tin metal salt solutes being difficult to dissolve in alcohols by limiting the order in which copper, zinc, and tin dissolve in a mixed solvent, and successfully prepares copper-zinc-tin-sulfur / selenium thin films.

[0008] Accordingly, the present invention also provides an application of copper-zinc-tin-sulfur / selenium thin film in solar cells.

[0009] (II) Technical Solution

[0010] To achieve the above objectives, the main technical solutions adopted by the present invention include:

[0011] In a first aspect, the present invention provides a method for preparing copper-zinc-tin-sulfur / selenium thin films based on alcohol solvents, comprising the following steps:

[0012] A clear precursor solution was prepared by completely dissolving copper nitrate, zinc acetate, and tin tetrachloride in a mixed solvent to obtain the copper-zinc-tin-selenium thin film. The mixed solvent included ethylene glycol and ethanol.

[0013] Most alcohol solvents are environmentally friendly, but copper, zinc, and tin metal salts are difficult to fully dissolve in alcohol solvents to obtain clear, transparent, and stable solutions. This invention dissolves copper nitrate, zinc acetate, and tin tetrachloride in a mixed solvent of ethylene glycol and ethanol in that order, which overcomes the technical problem that metal salts are difficult to dissolve in mixed solvents and are unstable. It can also quickly dissolve and produce clear, transparent, and stable solutions.

[0014] The molar ratio of the metals Cu, Zn, and Sn is Zn / Sn = 0.7–2.0, Cu / (Zn+Sn)

[0015] =0.4~1.4.

[0016] The concentrations of copper nitrate, zinc acetate, and tin tetrachloride in the precursor solution were 0.3–4 M.

[0017] Optionally, tin tetrachloride includes: tin tetrachloride pentahydrate

[0018] Optionally, to further improve the stability of dissolution, the volume ratio of ethylene glycol to ethanol is 2-5:1-3.

[0019] Optionally, the preparation of the precursor solution includes the following steps:

[0020] S1 dissolves a mixture of copper nitrate and zinc acetate in a mixed solvent of ethylene glycol and ethanol, stirring until completely dissolved to obtain a clear mixed solution;

[0021] S2 adds tin tetrachloride to the obtained mixed solution in an environment isolated from air and water vapor, and heats it at 40-70°C to dissolve it and obtain the precursor solution.

[0022] In this invention, a mixture of copper nitrate and zinc acetate is first dissolved in a mixed solvent to prepare a clear solution, and then tin tetrachloride is added to obtain a stable and clear solution.

[0023] Heating at 40–70°C can promote the dissolution process, but excessively high temperatures can cause precipitation in the solution, while excessively low temperatures make dissolution difficult.

[0024] The environment, which isolates air and moisture, is achieved by filling a glove box with inert gases such as nitrogen.

[0025] Optionally, in step S1, copper nitrate is first dissolved in a mixed solvent, and then zinc acetate is dissolved.

[0026] Optionally, the method for preparing copper-zinc-tin-selenium thin films further includes the following steps:

[0027] S3. Repeat steps S31-S35 sequentially 11 times until the desired thickness is achieved to obtain the precursor film.

[0028] S31 The obtained precursor solution is added dropwise to cover the surface of the molybdenum glass.

[0029] S32 First spin coating: The first spin coating speed is 1800~2200r / min, and the spin coating time is 45~80s;

[0030] S33 Second spin coating: The second spin coating speed is 3800-4200 r / min, and the spin coating time is 25-35 s;

[0031] S34 is heated at 200℃~500℃ for 1.5~2.5min;

[0032] S35 cooled to room temperature;

[0033] Copper-zinc-tin-sulfur / selenium films were prepared by sulfurizing and / or selenizing the S4 precursor film.

[0034] Optionally, the sulfur / selenization in step S4 is as follows: the precursor film and the sulfur / selenization source are placed in a sealed environment filled with inert gas, heated to 400-800°C, held for 5-200 minutes, and then naturally cooled to complete the selenization to obtain a copper-zinc-tin sulfur / selenium film.

[0035] One possible method is to place a sulfur / selenide source at the center of the bottom of a graphite box, place the precursor thin film graphite box spacer on it, put it into an annealing furnace, evacuate the furnace and introduce nitrogen gas, and heat it to 400-800°C at a heating rate of 100°C / min under a pressure of 0.1-3 MPa.

[0036] Optionally, the sulfur / selenide source includes one or a combination of selenium powder, sulfur powder, and selenium powder.

[0037] Secondly, the present invention provides a copper-zinc-tin-selenium / sulfur / selenium thin film prepared by the preparation method of the copper-zinc-tin-selenium thin film described in any of the above embodiments.

[0038] Thirdly, the present invention provides an application of the copper-zinc-tin-selenium thin film in solar cells.

[0039] Optionally, a copper-zinc-tin-sulfur / selenium thin film is prepared by sequentially preparing a CdS buffer layer by chemical bath deposition, a ZnO window layer and an ITO transparent conductive layer by magnetron sputtering, and an Ag grid top electrode by thermal evaporation to obtain a copper-zinc-tin-sulfur / selenium thin film solar cell.

[0040] The etching treatment of the copper-zinc-tin-sulfur / selenium thin film before the preparation of the CdS buffer layer is as follows: the copper-zinc-tin-sulfur / selenium thin film is immersed in 5 vol% dilute hydrochloric acid for 10 min under 75℃ water bath conditions, rinsed repeatedly with deionized water and dried with nitrogen gas, and then immersed in 20 wt% ammonium sulfide solution for 3 min at room temperature, rinsed repeatedly with deionized water and dried with nitrogen gas.

[0041] The thickness of the CdS buffer layer can be 10–100 nm; the thickness of the ZnO window layer can be 30–120 nm; the thickness of the ITO transparent conductive layer can be 30–900 nm; and the thickness of the Ag gate electrode can be 50–3000 nm.

[0042] The chemical bath deposition method is as follows:

[0043] Add 40 ml of ultrapure water, 3.75 ml of 0.019 M cadmium acetate ammonia solution, and 5 ml of 1 M thiourea solution to a 50 ml volumetric flask in sequence. Finally, add ultrapure water to make up to 50 ml to obtain the soaking solution. Pour out the soaking solution and keep it in a 75°C water bath while stirring at a speed of 100-300 rpm. Under stirring, immerse the copper-zinc-tin-sulfur / selenium film completely in the soaking solution for 7 minutes for deposition. Remove the film, rinse it repeatedly with deionized water, and dry it with nitrogen gas. A CdS film with a thickness of 50-70 nm can be obtained on the surface of the copper-zinc-tin-selenium film.

[0044] (III) Beneficial Effects

[0045] The beneficial effects of this invention are:

[0046] The alcohol solvent used in this invention is environmentally friendly and will not cause serious pollution or damage to the environment. The solution obtained by dissolving the metal salt in the alcohol solvent provided by this invention has good stability and wettability, and is suitable for solution-based preparation of absorbent layers such as spin coating, doctor blade coating, and inkjet printing.

[0047] This invention dissolves copper nitrate, zinc acetate, and tin tetrachloride in a mixed solvent of ethylene glycol and ethanol in that order, overcoming the technical problem that metal salt solutes are difficult to dissolve in mixed solvents and are unstable. It dissolves the solutes in a short time to produce a clear, transparent, and stable solution, and uses this solution to prepare an effective copper-zinc-tin-sulfur / selenium thin-film solar cell. Attached Figure Description

[0048] Figure 1 The X-ray diffraction pattern measured in Experiment 1 of this invention;

[0049] Figure 2 This is a SEM image of the surface of the copper-zinc-tin-selenium thin film measured in Experiment 2 of this invention;

[0050] Figure 3 This is the JV diagram of the CZTSe solar cell sample measured in Experiment 3 of this invention. Detailed Implementation

[0051] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below through specific embodiments.

[0052] Example 1

[0053] This embodiment provides a method for preparing a copper-zinc-tin precursor solution, specifically as follows:

[0054] In a glove box (vacuumed and filled with inert gas to ensure that all embodiments are carried out in an oxygen- and water-free environment), copper nitrate trihydrate and anhydrous zinc acetate are added to an alcohol mixture and magnetically stirred until completely dissolved until a clear blue transparent solution is obtained (a clear solution can be obtained within 10 minutes of magnetic stirring). Then, tin tetrachloride pentahydrate is added and stirring is continued until a clear blue-green transparent solution is obtained (stirring time < 10 minutes), which is the copper-zinc-tin precursor solution.

[0055] The weight-to-volume ratio of copper nitrate trihydrate, anhydrous zinc acetate, tin tetrachloride pentahydrate, and mixed solvent is: 0.7191g: 0.4514g: 0.7188g: 3.75ml.

[0056] The alcohol mixed solvent is a mixture of ethylene glycol and ethanol in a volume ratio of 3:2.

[0057] In the copper-zinc-tin precursor solution obtained in this embodiment, the molar ratio of Zn / Sn is 1.2, the molar ratio of Cu / (Zn+Sn) is 0.66, and the molar concentration of the metal salt in the total solution is 2M.

[0058] The copper-zinc-tin precursor solution obtained in this embodiment remained a clear solution after standing for 7 days, which proves its good stability.

[0059] The preparation method of this embodiment can achieve complete dissolution of each component in a short time to obtain a clear and stable copper-zinc-tin precursor solution.

[0060] In this embodiment, even when tin tetrachloride pentahydrate is tin tetrachloride dihydrate, a clear solution cannot be obtained.

[0061] Comparative Example 1

[0062] In a glove box (vacuumed and filled with inert gas to ensure that all embodiments are carried out in an oxygen- and water-free environment), 0.7191g of copper nitrate trihydrate, 0.4514g of zinc acetate aqueous solution, and 0.7188g of tin tetrachloride pentahydrate were sequentially added to a glass bottle containing a magnetic stir bar. 3.75ml of a mixed solvent of ethylene glycol and ethanol (ethylene glycol:ethanol = 3:2) was added using a pipette. The solution was magnetically stirred at room temperature, and the solution became turbid, producing a large amount of flocculent and lumpy precipitates.

[0063] This indicates that a clear solution of the copper-zinc-tin precursor is difficult to obtain in air by a one-step dissolution method.

[0064] Comparative Example 2

[0065] Preparation of precursor solution: Weigh 0.7191g of copper nitrate trihydrate and 0.4514g of anhydrous zinc acetate in air and add them to a glass bottle equipped with a magnetic stir bar. Use a pipette to add 3.75ml of a mixed solvent of ethylene glycol and ethanol (ethylene glycol:ethanol = 3:2). Stir magnetically at room temperature to obtain a clear, dark green, transparent solution. Then weigh and add 0.4626g of stannous chloride dihydrate, which generates a large amount of flocculent and lumpy precipitates. These precipitates remain in a precipitate state even after stirring or standing for a long time.

[0066] This indicates that when stannous chloride is in the form of stannous chloride dihydrate in air, it is difficult to obtain a copper-zinc-tin solution by a stepwise method.

[0067] Comparative Example 3

[0068] 0.7191 g of copper nitrate trihydrate, 0.4514 g of anhydrous zinc acetate, and 0.4626 g of stannous chloride dihydrate were weighed in air and added to a glass bottle containing a magnetic stir bar. 3.75 ml of a mixed solvent of ethylene glycol and ethanol (ethylene glycol:ethanol = 3:2) was added using a pipette. The solution was stirred magnetically at room temperature. The solution became turbid and a large amount of flocculent and lumpy precipitates were formed.

[0069] This indicates that when stannous chloride is in the form of stannous chloride dihydrate, it is difficult to obtain a clear copper-zinc-tin precursor solution by one-step dissolution in air.

[0070] Comparative Example 4: A copper-zinc-tin precursor solution was prepared in a glove box using tin tetrachloride pentahydrate as a tin salt.

[0071] Weigh 0.7191g of copper nitrate trihydrate and 0.4514g of anhydrous zinc acetate in a glove box and add them to a glass bottle with a magnetic stir bar. Use a pipette to add 3.75ml of a mixed solvent of ethylene glycol and ethanol (ethylene glycol: ethanol = 3:2). Stir magnetically and when the solution gradually becomes clear but not completely dissolved, weigh out 0.7188g of tin tetrachloride pentahydrate. At this point, the solution gradually becomes turbid and flocculent precipitate forms.

[0072] Tin tetrachloride pentahydrate readily hydrolyzes to produce stannic acid and hydrogen chloride, generating white fumes. Therefore, it is necessary to prepare the copper-zinc-tin precursor solution in the absence of oxygen and water.

[0073] This indicates that when copper nitrate trihydrate and zinc acetate are not completely dissolved in the glove box, it is difficult to obtain a copper-zinc-tin solution by adding tin tetrachloride pentahydrate.

[0074] Example 2

[0075] This embodiment provides a method for preparing a copper-zinc-tin precursor solution, specifically as follows:

[0076] In a glove box, copper nitrate trihydrate and anhydrous zinc acetate were added to an alcohol mixture and stirred magnetically for about 10 minutes until completely dissolved, resulting in a clear blue transparent solution. Then, tin tetrachloride pentahydrate was added and stirring continued until the solution returned to a clear blue-green transparent solution, which is the copper-zinc-tin precursor solution. In the copper-zinc-tin precursor solution, the molar ratio of Cu, Zn, and Sn was Zn / Sn = 0.7 and Cu / (Zn+Sn) = 1.4. The concentrations of copper nitrate trihydrate, zinc acetate, and tin tetrachloride pentahydrate in the precursor solution were 0.3 M.

[0077] The alcohol mixed solvent is a mixture of ethylene glycol and ethanol in a volume ratio of 3:2.

[0078] The copper-zinc-tin precursor solution obtained in this embodiment remained a clear solution after standing for 7 days, which proves its good stability.

[0079] The preparation method of this embodiment involves stirring for less than 10 minutes for each step, indicating that this embodiment can achieve complete dissolution of each component in a short time to obtain a clear and stable copper-zinc-tin precursor solution.

[0080] Example 3

[0081] This embodiment provides a method for preparing a copper-zinc-tin precursor solution, specifically as follows:

[0082] In a glove box, copper nitrate trihydrate and anhydrous zinc acetate were added to an alcohol mixture and stirred magnetically for about 10 minutes until completely dissolved, resulting in a clear blue transparent solution. Then, tin tetrachloride pentahydrate was added and stirring continued until a clear blue-green transparent solution was obtained, which is the copper-zinc-tin precursor solution. In the copper-zinc-tin precursor solution, the molar ratio of Cu, Zn, and Sn was Zn / Sn = 2 and Cu / (Zn+Sn) = 0.4. The concentrations of copper nitrate trihydrate, zinc acetate, and tin tetrachloride pentahydrate in the precursor solution were 4M.

[0083] The alcohol mixed solvent is a mixture of ethylene glycol and ethanol in a volume ratio of 3:2.

[0084] The copper-zinc-tin precursor solution obtained in this embodiment remained a clear solution after standing for 7 days, which proves its good stability.

[0085] The preparation method of this embodiment involves stirring for less than 10 minutes for each step, indicating that this embodiment can achieve complete dissolution of each component in a short time to obtain a clear and stable copper-zinc-tin precursor solution.

[0086] The copper-zinc-tin precursor solutions in Examples 1-3 of this invention can be prepared by a one-step dissolution method and can all be successfully applied in solar cells.

[0087] Example 4

[0088] This embodiment provides a method for preparing copper-zinc-tin-selenium thin films from copper-zinc-tin precursor solutions, the steps of which are as follows:

[0089] S1. Repeat the following steps S11-S35 11 times to obtain the precursor film:

[0090] The precursor solution obtained in any one of Examples 1-3 was dropped onto the molybdenum glass surface; after the first spin coating at 2000 r / min for 60 s, a second spin coating at 4000 r / min for 30 s was continued; the glass was placed on a 250°C heating stage and kept for 2 min, then cooled to room temperature.

[0091] S2 Take 350mg of selenium powder, spread it in the center of the bottom of the graphite box, place the obtained precursor film on the graphite box partition, and put it into the annealing furnace;

[0092] Evacuate to below 30 mtorr and close the valve. Then introduce nitrogen gas to raise the vacuum to 500 Torr and close the nitrogen gas valve. Repeat the vacuuming and nitrogen gas introduction steps three times to ensure that the selenization reaction is carried out under oxygen-free nitrogen protection.

[0093] Adjust the inlet and outlet valves to maintain the gas pressure inside the quartz tube of the return furnace at one atmosphere. Heat to 540°C at a heating rate of 100°C / min and hold for 15 minutes to replace oxides with selenides and further generate copper zinc tin selenide (CZTSe) thin films.

[0094] Example 5

[0095] This embodiment provides a method for preparing copper-zinc-tin-sulfur thin films from copper-zinc-tin precursor solutions, the steps of which are as follows:

[0096] S1. Repeat the following steps S11-S35 11 times to obtain the precursor film:

[0097] The precursor solution obtained in any one of Examples 1-3 was dropped onto the molybdenum glass surface; after the first spin coating at 2200 r / min for 48 s, a second spin coating was carried out at 4200 r / min for 25 s; the glass was placed on a 300°C heating stage and kept for 1.5 min, and then cooled to room temperature.

[0098] S2 Take 300mg of selenium powder and 20mg of sulfur powder, spread them in the center of the bottom of the graphite box, place the obtained precursor film on the graphite box partition, and put it into the annealing furnace;

[0099] Evacuate to below 30 mtorr and close the valve. Then introduce nitrogen gas to raise the vacuum to 500 Torr and close the nitrogen gas valve. Repeat the vacuuming and nitrogen gas introduction steps three times to ensure that the selenization reaction is carried out under oxygen-free nitrogen protection.

[0100] Adjust the inlet and outlet valves to maintain the gas pressure inside the quartz tube of the return furnace at one atmosphere. Heat to 650°C at a heating rate of 100°C / min and hold for 5 minutes. Heating causes the oxides to be replaced by sulfur and selenides and further generates a copper-zinc-tin-sulfur film.

[0101] Example 6

[0102] This embodiment provides a method for preparing copper-zinc-tin-sulfur-selenium thin films from copper-zinc-tin precursor solutions, the steps of which are as follows:

[0103] S1. Repeat the following steps S11-S35 11 times to obtain the precursor film:

[0104] The precursor solution obtained in any one of Examples 1-3 was dropped onto the molybdenum glass surface; after the first spin coating at 1800 r / min for 80 s, a second spin coating was carried out at 3800 r / min for 35 s; the glass was then placed on a 350°C heating stage and kept for 2.5 min before cooling to room temperature.

[0105] S2 Take 400mg of selenium powder and 50mg of sulfur powder, spread them in the center of the bottom of the graphite box, place the obtained precursor film on the graphite box partition, and put it into the annealing furnace;

[0106] Evacuate to below 30 mtorr and close the valve. Then introduce nitrogen gas to raise the vacuum to 500 Torr and close the nitrogen gas valve. Repeat the vacuuming and nitrogen gas introduction steps three times to ensure that the selenization reaction is carried out under oxygen-free nitrogen protection.

[0107] Adjust the inlet and outlet valves to maintain the gas pressure inside the quartz tube of the return furnace at one atmosphere. Heat to 480°C at a heating rate of 100°C / min and hold for 20 minutes. Heating causes the oxides to be replaced by sulfur and selenides and further generates a copper zinc tin sulfide selenium (CZTSSe) film.

[0108] Example 7

[0109] This embodiment provides the application of the copper-zinc-tin-sulfur / selenium thin films prepared in Examples 4-6 in solar cells, and the steps are as follows:

[0110] Etching treatment of S1 copper-zinc-tin-sulfur / selenium thin film: The copper-zinc-tin-sulfur / selenium thin film was immersed in 5 vol% dilute hydrochloric acid for 10 min under 75℃ water bath conditions, rinsed repeatedly with deionized water and dried with nitrogen gas. At room temperature, it was immersed in 20 wt% ammonium sulfide solution for 3 min, rinsed repeatedly with deionized water and dried with nitrogen gas.

[0111] S2 Chemical Bath Deposition Method: The etched copper-zinc-tin-sulfur / selenium thin film is placed in a 50ml volumetric flask and 40ml of ultrapure water, 3.75ml of 0.019M cadmium acetate ammonia solution, and 5ml of 1M thiourea solution are added sequentially. Finally, ultrapure water is added to make up to 50ml to prepare the soaking solution. The soaking solution is poured out and kept at 75℃ in a water bath while being stirred at 100-300rpm. Under stirring, the copper-zinc-tin-selenium thin film is completely immersed in the soaking solution for 7min under suspension for deposition. After removal, it is repeatedly rinsed with deionized water and dried with nitrogen gas. A CdS film with a thickness of 50-70nm can be obtained on the surface of the copper-zinc-tin-sulfur / selenium thin film.

[0112] S3 sequentially prepared a 50 nm ZnO layer by radio frequency sputtering of the obtained CdS thin film, prepared a 300 nm ITO window layer by DC sputtering, and finally prepared an Ag grid top electrode by thermal evaporation to obtain a CZTSSe solar cell.

[0113] Experiment 1: The copper-zinc-tin precursor solution obtained in Example 1 of this invention was used to prepare a copper-zinc-tin-selenium thin film using the method in Example 4. The results were obtained by XRD diffraction. Figure 1 The diffraction pattern shown in the figure represents the copper-zinc-tin-selenium thin film obtained in this invention, the vertical line is the CZTSe standard card, and MoSe2 is the reaction product of Mo substrate and Se during selenization. Figure 1 It can be seen that the copper-zinc-tin-selenium thin film obtained by the present invention can match the diffraction peak positions of the CZTSe standard card, indicating that the present invention has successfully prepared a crystalline thin film with CZTSe as the main phase.

[0114] Experiment 2: SEM images of the copper-zinc-tin selenium thin film surface obtained from the copper-zinc-tin precursor solution obtained in Example 1 of this invention, using the method in Example 4, are shown below. Figure 2 As shown, from Figure 2 From this, we can see that the crystal grains of the thin film are obvious;

[0115] Experiment 3: The copper-zinc-tin precursor solution obtained in Example 1 of this invention, the copper-zinc-tin-selenium thin film prepared using the method in Example 4, and the CZTSe thin-film solar cell prepared using the method in Example 7 were used to test the cell performance using a standard solar cell tester; Figure 3 The JV diagram and performance parameters of the battery sample are shown, from which it can be concluded that the present invention can prepare a CZTSe solar cell with a photoelectric conversion efficiency of 0.93%.

[0116] The results above show that the present invention uses green, environmentally friendly, stable, and highly wettable alcohol solvents to prepare solutions that can produce crystalline thin films of CZTSe composition and thus obtain effective CZTSe thin-film solar cells.

[0117] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing copper-zinc-tin-sulfur / selenium thin films based on alcohol solvents, characterized in that, It includes the following steps: A clear precursor solution is prepared by completely dissolving copper nitrate, zinc acetate, and tin tetrachloride in a mixed solvent. The precursor solution is then subjected to high-temperature sulfur / selenization to obtain the copper-zinc-tin-sulfur / selenium film. The mixed solvent includes ethylene glycol and ethanol, and does not include non-alcohol solvents other than water. The volume ratio of ethylene glycol to ethanol is 2~5:1~3; The preparation of the precursor solution includes the following steps: S1 dissolves a mixture of copper nitrate and zinc acetate in a mixed solvent of ethylene glycol and ethanol, stirring until completely dissolved to obtain a clear mixed solution; copper nitrate is dissolved in the mixed solvent first, and then zinc acetate is dissolved. S2 Add tin tetrachloride to the obtained mixed solution in an environment isolated from air and water vapor, and heat at 40~70℃ to dissolve it to obtain a precursor solution; The tin tetrachloride is tin tetrachloride pentahydrate; The precursor solution remained clear after standing at room temperature for 7 days, with no precipitation.

2. The method for preparing copper-zinc-tin-sulfur / selenium thin films based on alcohol solvents as described in claim 1, characterized in that, It also includes the following steps: S3 is repeated 11 times in sequence with steps S31-S35 to obtain the precursor film of the desired thickness: S31 The obtained precursor solution is added dropwise to cover the surface of the molybdenum glass. S32 First spin coating: The first spin coating speed is 1800~2200r / min, and the spin coating time is 45~80s; S33 Second spin coating: The second spin coating speed is 3800~4200r / min, and the spin coating time is 25~35s; S34 is heated at 200℃~500℃ for 1.0~2.5 min; S35 cooled to room temperature; Copper-zinc-tin-sulfur / selenium films were prepared by sulfurizing and / or selenizing the S4 precursor film.

3. The method for preparing copper-zinc-tin-sulfur / selenium thin films based on alcohol solvents as described in claim 2, characterized in that, The selenization in step S4 is as follows: the precursor film and the sulfur / selenization source are placed in a sealed environment filled with inert gas, heated to 400~800℃, held for 5~200min, and naturally cooled to complete the sulfur / selenization and obtain a copper-zinc-tin sulfur / selenium film.

4. The method for preparing copper-zinc-tin-sulfur / selenium thin films based on alcohol solvents as described in claim 3, characterized in that: The sulfur / selenide source is one of selenium powder, sulfur powder, or selenium-sulfurized powder.

5. A copper-zinc-tin-sulfur / selenium thin film prepared by the method according to any one of claims 1-4.

6. The application of the copper-zinc-tin-sulfur / selenium thin film as described in claim 5 in a solar cell.

7. The application of the copper-zinc-tin-sulfur / selenium thin film as described in claim 6 in solar cells, characterized in that: A copper-zinc-tin-sulfur / selenium solar cell was prepared by sequentially preparing a CdS buffer layer by chemical bath deposition, a ZnO window layer and an ITO transparent conductive layer by magnetron sputtering, and then preparing an Ag grid top electrode by thermal evaporation.

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