Copper-zinc-tin-sulfur-selenium thin film prepared by variable-temperature sulfur-seleniumization process, method and solar cell

Abstract

The application belongs to the technical field of photoelectric material new energy, and particularly relates to a copper-zinc-tin-sulfur-selenium film prepared by a variable-temperature sulfur-seleniumization process, a method and a solar cell. The application adopts a variable-temperature sulfur-seleniumization mode to prepare a copper-zinc-tin-sulfur-selenium (CZTS) absorption layer film, comprehensively uses the advantages of high temperature and low temperature, optimizes a crystal grain growth process, and prepares the absorption layer film with a smooth surface, fewer holes and dense distribution. The film is used as the absorption layer film of the solar cell, and finally the copper-zinc-tin-sulfur-selenium film solar cell with high efficiency is prepared.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy of optoelectronic materials, and particularly relates to a method for preparing a copper-zinc-tin-sulfur-selenide thin film by a variable temperature sulfur-selenization process and a copper-zinc-tin-sulfur-selenide thin film solar cell containing the same. Background Art

[0002] Copper zinc tin sulfur selenide thin film solar cells have the advantages of rich composition elements, no toxic components, environmental friendliness and low price, and are considered one of the most promising thin film photovoltaic technologies. Currently, the certified efficiency of CZTSSe solar cells has only reached 14.9%. The main reason for the low efficiency is the open circuit voltage loss (V oc，def ) is large, which leads to V oc，def The main factors that affect the efficiency of solar cells are deep level defects, secondary phases, band tail states, and interface recombination. As the core of solar cell devices, the absorber layer is the source of solving efficiency problems. Further optimizing the absorber layer growth process is an effective way to improve efficiency.

[0003] The film was prepared by solution method. The surface morphology and crystal quality of CZTSSe film were determined by the preparation of precursor solution and high temperature sulfur selenization. 4+ The direct phase transition growth mechanism effectively reduces surface defects and reduces the open circuit voltage loss to below 300mV. 4+ As the Sn source in the precursor solution, the precursor solution preparation is essentially stable. For high-temperature sulfur-selenide, most research groups use a constant high temperature to complete the process. High-temperature sulfur-selenide temperatures are generally above 550°C. Prolonged high-temperature treatment can produce a series of adverse effects, such as tin loss, decomposition of CZTSSe into secondary phases, and the formation of excessively thick Mo(S,Se)2. Lowering the sulfur-selenide temperature can reduce grain size, increase the number of grain boundaries, and reduce device performance. The research group led by Researcher Yu Qingbo of the Chinese Academy of Sciences discovered that high temperature accelerates phase transitions, while low temperature promotes the formation of smooth, dense films. By synergistically utilizing constant high and low temperature sulfur-selenide processes, they achieved an efficiency of 12.5%. Experiments have shown that high-temperature sulfur-selenide (570°C) promotes rapid phase transitions and large grains, but continuous high temperatures can lead to film decomposition. Low-temperature sulfur-selenide (510°C) results in a relatively dense film surface, but the grains remain small and porous.

[0004] Therefore, how to prepare a copper-zinc-tin-sulfur-selenide thin film with a smooth surface, fewer holes, and dense distribution and a CZTSSe solar cell with high efficiency is a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention adopts a variable temperature sulfur-selenide method to prepare a CZTSSe absorption layer film, optimizes the grain growth process, and comprehensively utilizes the advantages of high-temperature and low-temperature sulfur-selenide to prepare an absorption layer film with a smooth surface, fewer holes, and dense distribution; and uses this film as the absorption layer film of a solar cell, and finally prepares a copper-zinc-tin-sulfur-selenide thin film solar cell with an efficiency of 10.8%.

[0006] It should be noted that this invention explores a new thin-film growth method based on the conventional high-temperature constant-temperature sulfur-selenization process. This method utilizes a high-temperature, constant-temperature, and low-temperature sulfur-selenization process at 570°C and 510°C to achieve sulfur-selenization, i.e., a high-temperature, low-temperature, cyclic sulfur-selenization method to prepare CZTSSe thin films. Furthermore, this method, based on a dual-solvent system of DMSO and MOE, was used to prepare high-efficiency solar cells.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for preparing a copper-zinc-tin-sulfur-selenide thin film by a variable temperature sulfur-selenide process, the method specifically comprising the following steps:

[0009] (1) Preparing a precursor solution and centrifuging and standing: According to the ratio of elements in the precursor solution to be prepared, weigh thiourea, cuprous chloride, zinc acetate dihydrate, and tin tetrachloride pentahydrate in sequence and add them to a clean transparent glass bottle equipped with a rotor, then add dimethyl sulfoxide and ethylene glycol methyl ether in a volume ratio of 1:1, and then place the mixture in a constant temperature water bath and stir to obtain a precursor solution; centrifuge the precursor solution and stand it for use;

[0010] (2) Repeat spin coating-baking-cooling to prepare a precursor film: fix the cleaned molybdenum glass on the suction cup of the spin coater, absorb the precursor solution after centrifugation and standing in step (1) and drip it on the surface of the molybdenum glass, and spin coat after the precursor solution is completely covered; after the spin coating is completed, take out the sample, bake it, cool it to room temperature, and repeat the three steps of spin coating-baking-cooling for a total of 10 times to obtain a precursor film;

[0011] (3) Preparation of absorption layer film by variable temperature sulfur-selenization: The precursor film, stannous sulfide and selenium pellets obtained in step (2) are placed in a single temperature zone tubular furnace for variable temperature sulfur-selenization. After the sulfur-selenization is completed, it is cooled to room temperature to obtain a copper zinc tin sulfur selenide CZTSSe film.

[0012] Preferably, in step (1), the designed molar ratios of the metal elements Cu / (Zn+Sn) and Zn / Sn in the precursor solution are 0.72 and 1.14 respectively, the designed molar ratio of S / metal element is 1.86, the temperature of the constant temperature water bath is 60°C, the stirring speed is 666r / min, and the stirring time is 3 hours.

[0013] Preferably, in step (2), the molybdenum glass includes 2 mm thick soda-lime glass and 1 μm thick molybdenum layer, the thickness of the precursor film is 1.3 μm; and the spin coating speed is 3000 r / min, the time is 36 s; the baking temperature is 300°C, and the time is 2 min.

[0014] Preferably, in step (3), the specific operation of the variable temperature sulfur-selenization including the soft sulfur-selenization stage and the high temperature sulfur-selenization stage is as follows:

[0015] First, the temperature was raised from room temperature to 280°C over 9 minutes and maintained at 280°C for 10 minutes for soft sulfur-selenization. Then, the temperature was further raised to 510°C for 9 minutes to start high-temperature sulfur-selenization. The temperature was then timed to be raised from 510°C to 570°C for 3.5 minutes, then cooled from 570°C to 510°C for 3.5 minutes, then raised from 510°C to 570°C for 3.5 minutes, then cooled from 570°C to 510°C for 3.5 minutes, thus completing the entire variable-temperature sulfur-selenization process.

[0016] Among them, the heating rate from room temperature to 280℃ for soft sulfur-selenide is 28.3℃ / min, the heating rate from 280℃ to 510℃ for sulfur-selenide is 25.5℃ / min, and the temperature change rate from 510℃ to 570℃ and from 570℃ to 510℃ is 17.1℃ / min.

[0017] Furthermore, the ratio of the quantity of the precursor film, the mass of stannous sulfide and the mass of the selenium pills is 1 piece: 1.25 g: 125 g.

[0018] The second technical purpose of the present invention is to provide a copper-zinc-tin-sulfur-selenium thin film prepared by the above method.

[0019] The third technical purpose of the present invention is to provide a copper-zinc-tin-sulfur-selenium thin film solar cell, which includes the above-mentioned copper-zinc-tin-sulfur-selenium thin film.

[0020] Specifically, the copper-zinc-tin-sulfur-selenide thin-film solar cell has a structure of SLG / Mo / CZTSSe / CdS / i-ZnO / ITO / Ni-A1; and the preparation method of the copper-zinc-tin-sulfur-selenide thin-film solar cell is as follows:

[0021] A 50nm thick cadmium sulfide (CdS) buffer layer was deposited on the CZTSSe film using chemical water bath deposition, followed by magnetron sputtering of a 50nm thick intrinsic zinc oxide (i-ZnO) and a 300nm thick tin-doped indium oxide (ITO) window layer. Finally, nickel-aluminum (Ni-A1) electrodes were deposited using thermal evaporation to complete the preparation of the CZTSSe solar cell.

[0022] Furthermore, the temperature of the chemical water bath deposition was 75°C, the rotation speed was 366 r / min, and the background vacuum of the magnetron sputtering was 5×10 -4 Pa, the working pressure of sputtering i-Zno is 0.5Pa, the power and time are 35W-20min, 60W-5min; the working pressure of sputtering ITO is 0.3Pa, the power is 80W-90min.

[0023] Furthermore, the specific steps for preparing the copper-zinc-tin-sulfur-selenium thin film solar cell are as follows:

[0024] 1) Use processed tweezers to pick up the absorption layer film and soak it in ultrapure water for 15 minutes to remove the oxide on the surface of the CZTSSe film; measure 22mL of ultrapure water respectively and put it into the small beakers with numbers, weigh 1.256gTu and 0847gCdSO4·8 / 3H2O in turn and add them to the above beakers and promote dissolution by ultrasound; set the temperature of the constant temperature water bath to 75℃ and the speed to 366r / min, and move the soaked sample to a sedimentation beaker with 150mL of ultrapure water and a rotor; first pour in the cadmium sulfate aqueous solution, then pour in the ammonia water after 40s, and then pour in the thiourea aqueous solution after 1 minute and 40s. After 8 minutes and 30s, take out the sample and rinse it with ultrapure water three times, and finally dry it on a hot plate.

[0025] 2) Place the sample of the deposited buffer layer into the window layer chamber of the magnetron sputtering, pump the gas pressure from atmospheric pressure to 10 Pa using a mechanical pump, and then pump it to 5×10 -4 When sputtering i-ZnO, the working pressure is 0.5Pa, the high-purity argon flow rate is 13sccm, and the sputtering power is 35W-20min, 60W-5min; when sputtering ITO, the working pressure is 0.3Pa, the high-purity argon flow rate is 6sccm, and the sputtering power is 80W-90min.

[0026] 3) Finally, a Ni-Al electrode is evaporated on the window layer to obtain a copper-zinc-tin-sulfur-selenium thin film solar cell.

[0027] The photoelectric conversion efficiency of the complete copper-zinc-tin-sulfur-selenide thin-film solar cell prepared by the above method is 10.8%, its open circuit voltage is 506.2mV, and its short-circuit current density is 33.04mA / cm 2 , the filling factor is 64.59%.

[0028] Through the above technical solution, compared with the prior art, it can be seen that the copper-zinc-tin-sulfur-selenide thin film, method and solar cell prepared by a temperature-variable sulfur-selenide process provided by the present invention have the following excellent effects:

[0029] 1) Compared to conventional constant-temperature sulfur-selenization, the variable-temperature sulfur-selenization method for preparing CZTSSe absorber films optimizes the grain growth process. By combining the advantages of high- and low-temperature sulfur-selenization, the resulting absorber film exhibits a smooth surface, few pores, and a dense distribution. Using this film as the absorber layer for solar cells, the fill factor and efficiency of the resulting CZTSSe thin-film solar cells increased from 56.29% and 9.37% to 64.59% and 10.8%, respectively.

[0030] 2) The present invention prepares the CZTSSe absorption layer film by temperature-variable sulfur-selenization, optimizes the grain growth process, and can obtain a high-quality absorption layer film and a CZTSSe thin-film solar cell with an efficiency of 10.8%. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. 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 any creative work.

[0032] Figure 1 This is the SEM image of the copper-zinc-tin-sulfur-selenium absorption layer film prepared in Example 1.

[0033] Figure 2 This is the SEM image of the copper-zinc-tin-sulfur-selenium absorption layer film prepared in Comparative Example 1.

[0034] Figure 3 This is the XRD pattern of the copper-zinc-tin-sulfur-selenium absorption layer film prepared in Example 1.

[0035] Figure 4 This is the XRD pattern of the copper-zinc-tin-sulfur-selenium absorption layer film prepared in Comparative Example 1.

[0036] Figure 5 This is the Raman graph of the copper-zinc-tin-sulfur-selenium absorption layer film prepared in Example 1.

[0037] Figure 6 This is the Raman graph of the copper-zinc-tin-sulfur-selenium absorption layer film prepared in Comparative Example 1.

[0038] Figure 7 This is a JV curve of the copper-zinc-tin-sulfur-selenium thin film solar cell prepared in Example.

[0039] Figure 8 This is the JV curve of the copper-zinc-tin-sulfur-selenium thin film solar cell prepared in comparative example.

[0040] Figure 9 This is the EQE curve of the copper-zinc-tin-sulfur-selenium thin film solar cell prepared in Example.

[0041] Figure 10 This is the EQE curve of the copper-zinc-tin-sulfur-selenium thin film solar cell prepared in comparative example. DETAILED DESCRIPTION

[0042] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0043] The term "embodiment" is used herein specifically to describe any embodiment as "exemplary," and should not be construed as superior or preferable to other embodiments. Performance indicators in the embodiments of this application were tested using conventional testing methods in the art, unless otherwise specified. It should be understood that the terms used in this application are intended solely to describe specific implementations and are not intended to limit the disclosure herein.

[0044] In order to better illustrate the content of this application, numerous specific details are provided in the specific examples below. It should be understood by those skilled in the art that this application can be implemented without certain specific details. In the examples, some methods, means, instruments, equipment, etc. well known to those skilled in the art are not described in detail in order to highlight the main purpose of this application.

[0045] Under the premise of no conflict, the technical features disclosed in the embodiments of this application can be combined arbitrarily, and the resulting technical solutions belong to the contents disclosed in the embodiments of this application.

[0046] For a better understanding of the present invention, the present invention is further specifically described below through the following examples, but it should not be understood as limiting the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above invention content are also considered to fall within the scope of protection of the present invention.

[0047] It should be noted that in the following experimental preparation, Tu was purchased from Beijing Inokai Technology Co., Ltd. with a purity of 99%, CuCl with a purity of 99.9%; SnCl4·5H2O was purchased from with a purity of 99.995%; Zn(CH3COOH)2·2H2O was purchased from with a purity of 99.99%; DMSO was purchased from with a purity of 99.9% (Aladdin); MOE with a purity of 99.8%. Except for Tu, all the above drugs were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0048] Example 1

[0049] (1) Prepare the precursor solution and centrifuge it:

[0050] First, according to the desired element ratio of the precursor solution, 1.1327g of thiourea (CH4N2S, Tu), 0.3326g of cuprous chloride (CuCl), 0.5444g of zinc acetate dihydrate (Zn(CH3COOH)2·2H2O), and 0.7608g of tin tetrachloride pentahydrate (SnCl4·5H2O) were weighed and added to a clean, transparent glass bottle equipped with a rotor. Then, 2mL of dimethyl sulfoxide (DMSO) and 2mL of ethylene glycol monomethyl ether (MOE) were added to the glass bottle. The solution was then placed in a constant temperature water bath set at a temperature of 60°C and a speed of 666 rpm and stirred for 3 hours to obtain the precursor solution. The solution was extracted and placed into a centrifuge tube and centrifuged at 10,000 rpm. Finally, the centrifuged solution was placed on a test tube rack and allowed to stand.

[0051] (2) Repeated spin coating-baking-cooling to prepare the precursor film:

[0052] First, the cleaned molybdenum glass (the molybdenum glass includes 2 mm thick soda-lime glass and 1 μm thick molybdenum layer) is fixed on the suction cup of the spin coater, and then the centrifuged solution is sucked with a 2.5 mL syringe and dropped on the surface of the molybdenum glass. Wait until the solution is completely covered before spin coating. The parameters set for the spin coater are 3000 r / min and the time is 36 s. After the spin coating is completed, the sample is taken out and placed on a 300 ° C heating table for 2 minutes. After the sample is removed and cooled to room temperature, the three steps of spin coating-baking-cooling are repeated for a total of 10 times.

[0053] (3) Preparation of absorption layer film by temperature-variable sulfur-selenide treatment:

[0054] Four precursor films with a thickness of 1.3 μm obtained in step (2) were placed in a rectangular graphite box with a lid, along with 5 mg of tin sulfide (SnS) and 500 mg of selenium pellets (Se). The box was then placed in the middle of a quartz tube in a single-temperature zone tube furnace. The quartz tube was sealed and purged three times with nitrogen (N2), and then the temperature was raised. The sulfur selenization process included a soft sulfur selenization stage (maintained at 280°C for 10 min) and a high-temperature variable temperature sulfur selenization stage (after the soft sulfur selenization was completed, the temperature was raised to 510°C and high-temperature sulfur selenization was started and timed, with the temperature being raised from 510°C to 570°C for 3.5 min, then cooled from 570°C to 510°C for 3.5 min, then raised from 510°C to 570°C for 3.5 min, then cooled from 570°C to 510°C for 3.5 min, thereby completing the entire variable temperature sulfur selenization process). After the variable temperature sulfur selenization was completed, the sample was cooled to room temperature and then removed.

[0055] from Figure 1 It can be seen from the SEM image that the copper-zinc-tin-sulfur-selenium absorption layer film prepared in Example 1 has a smooth surface, large and dense grains, and few holes. Figure 3 and Figure 5It can be seen that the film prepared in Example 1 has a clear CZTSSe phase. In the XRD pattern, the (211) crystal plane diffraction peak intensity is much greater than the molybdenum peak, indicating that the film prepared under these conditions has good density and crystal quality. The Raman spectrum test results further verify the regulatory effect of variable temperature sulfur selenization on crystal growth, and no obvious secondary phase appears.

[0056] The specific steps for preparing a copper-zinc-tin-sulfur-selenium thin film solar cell according to the copper-zinc-tin-sulfur-selenium absorber layer thin film described in Example 1 are as follows:

[0057] A 50 nm thick cadmium sulfide (CdS) buffer layer was deposited on the CZTSSe film obtained by temperature-dependent sulfur selenization by chemical bath deposition. The temperature of the chemical bath deposition was 75 °C and the rotation speed was 366 r / min. The background vacuum of the magnetron sputtering window layer was 5×10 -4 Pa, the working pressure of sputtering i-Zno is 0.5Pa, the power and time are 35W-20min, 60W-5min; the working pressure of sputtering ITO is 0.3Pa, the power is 80W-90min; finally, the preparation of CZTSSe solar cells is completed by thermal evaporation of nickel-aluminum (Ni-Al) electrodes (50nm thick Ni, 500nm thick Al).

[0058] The JV curve of the copper-zinc-tin-sulfur-selenium thin film solar cell prepared above is as follows: Figure 7 As shown, the efficiency is 10.8%, the open circuit voltage is 506.2mV, and the short circuit current density is 33.04mA / cm 2 , the filling factor is 64.59%. EQE diagram is as follows Figure 9 As shown, the maximum EQE is greater than 90%, and the light absorption is good in the long-wave range, indicating that the crystal quality of the absorption layer thin film is good.

[0059] In order to further demonstrate the beneficial effects of the present invention and to better understand the present invention, the following comparative examples are provided to further illustrate the technical features disclosed in the present invention, but they should not be construed as limiting the present invention. Other improvements made by those skilled in the art based on the above invention without inventive work are also considered to fall within the scope of protection of the present invention.

[0060] Comparative Example 1

[0061] (1) Prepare the precursor solution and centrifuge it:

[0062] First, according to the desired element ratio of the precursor solution, 1.1327g of thiourea (CH4N2S, Tu), 0.3326g of cuprous chloride (CuCl), 0.5444g of zinc acetate dihydrate (Zn(CH3COOH)2·2H2O), and 0.7608g of tin tetrachloride pentahydrate (SnCl4·5H2O) were weighed and added to a clean, transparent glass bottle equipped with a rotor. Then, 2mL of dimethyl sulfoxide (DMSO) and 2mL of ethylene glycol monomethyl ether (MOE) were added to the glass bottle. The solution was then placed in a constant temperature water bath set at a temperature of 60°C and a speed of 666 rpm and stirred for 3 hours to obtain the precursor solution. The solution was extracted and placed into a centrifuge tube and centrifuged at 10,000 rpm. Finally, the centrifuged solution was placed on a test tube rack and allowed to stand.

[0063] (2) Repeated spin coating-baking-cooling to prepare the precursor film:

[0064] First, the cleaned molybdenum glass (the molybdenum glass includes 2 mm thick soda-lime glass and 1 μm thick molybdenum layer) is fixed on the suction cup of the spin coater, and then the centrifuged solution is sucked with a 2.5 mL syringe and dropped on the surface of the molybdenum glass. Wait until the solution is completely covered before spin coating. The parameters set for the spin coater are 3000 r / min and the time is 36 s. After the spin coating is completed, the sample is taken out and placed on a 300 ° C heating table for 2 minutes. After the sample is removed and cooled to room temperature, the three steps of spin coating-baking-cooling are repeated for a total of 10 times.

[0065] (3) Preparation of absorption layer film by temperature-variable sulfur-selenide treatment:

[0066] Four 1.3 μm thick precursor films obtained in step (2) were placed in a rectangular graphite box with a lid, along with 5 mg of tin sulfide (SnS) and 500 mg of selenium pellets (Se). The box was then placed in the middle of a quartz tube in a single-temperature zone tube furnace. The quartz tube was sealed and purged three times with nitrogen (N2), and then the temperature was raised. The sulfur selenization process included a soft sulfur selenization stage (maintained at 280°C for 10 minutes) and a high-temperature constant-temperature sulfur selenization stage (after the soft sulfur selenization was completed, the temperature was raised to 510°C and the high-temperature constant-temperature sulfur selenization was started and timed for 14 minutes). After the sulfur selenization was completed, the sample was allowed to cool to room temperature before being removed.

[0067] from Figure 2 From the SEM image, it can be seen that the film surface is unevenly distributed, with obvious holes that easily form leakage channels and reduce the open circuit voltage. The large surface undulations are not conducive to the preparation of buffer layer films. Figure 4 XRD patterns and Figure 6 It can be seen from the Raman spectrum that although high-temperature constant-temperature sulfur selenide also has three obvious main peaks, the intensity of the (211) crystal plane diffraction peak is weaker than that of the molybdenum peak, indicating that the crystallinity and distribution of the film are poor.

[0068] The specific steps for preparing a copper-zinc-tin-sulfur-selenium thin film solar cell according to the copper-zinc-tin-sulfur-selenium absorption layer thin film described in the comparative example are:

[0069] A 50 nm thick cadmium sulfide (CdS) buffer layer was prepared on the CZTSSe film obtained by high temperature constant temperature sulfide selenization by chemical water bath deposition. The temperature of chemical water bath deposition was 75 ° C and the rotation speed was 366 r / min. The background vacuum of the magnetron sputtering window layer was 5×10 -4 The i-ZnO sputtering process was performed at a pressure of 0.5 Pa and a power of 35 W for 20 minutes and 60 W for 5 minutes, respectively. The ITO sputtering process was performed at a pressure of 0.3 Pa and a power of 80 W for 90 minutes. Finally, the CZTSSe solar cell was fabricated by thermal evaporation of nickel-aluminum (Ni-Al) electrodes (50 nm thick Ni and 500 nm thick Al).

[0070] The JV curve of the copper-zinc-tin-sulfur-selenium thin film solar cell prepared in the comparative example is as follows: Figure 8 As shown, the efficiency is 9.37%, the open circuit voltage is 494.8mV, and the short circuit current density is 33.63mA / cm 2 , the filling factor is 56.29%. EQE is as Figure 10 As shown, the light absorption in the short-wave range (300nm-60nm) is good, and the light absorption in the long-wave range is poor, indicating that the quality of the thin film crystal prepared under this condition is poor.

[0071] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a copper-zinc-tin-sulfur-selenide thin film by a variable temperature sulfur-selenide process, characterized in that: The method specifically comprises the following steps: (1) Preparing a precursor solution and centrifuging and standing: According to the ratio of elements in the precursor solution to be prepared, weigh thiourea, cuprous chloride, zinc acetate dihydrate, and tin tetrachloride pentahydrate in sequence and add them to a clean transparent glass bottle equipped with a rotor, then add dimethyl sulfoxide and ethylene glycol methyl ether in a volume ratio of 1:1, and then place the mixture in a constant temperature water bath and stir to obtain a precursor solution; centrifuge the precursor solution and stand it for use; (2) Repeat spin coating-baking-cooling to prepare a precursor film: fix the cleaned molybdenum glass on the suction cup of the spin coater, absorb the precursor solution after centrifugation and standing in step (1) and drip it on the surface of the molybdenum glass, and spin coat after the precursor solution is completely covered; after the spin coating is completed, take out the sample, bake it, cool it to room temperature, and repeat the three steps of spin coating-baking-cooling for a total of 10 times to obtain a precursor film; (3) Temperature-variable sulfur-selenide preparation of the absorption layer film: the precursor film obtained in step (2), stannous sulfide and selenium pellets are placed in a single-temperature zone tubular furnace for temperature-variable sulfur-selenide, and after the sulfur-selenide is completed, the film is cooled to room temperature to obtain a copper-zinc-tin-sulfur-selenide (CZTSSe) film; In step (3), the variable temperature sulfur-selenization includes a soft sulfur-selenization stage and a high temperature sulfur-selenization stage, and the specific operation is as follows: First, the temperature was raised from room temperature to 280°C over 9 minutes and maintained at 280°C for 10 minutes for soft sulfur-selenization. Then, the temperature was further raised to 510°C for 9 minutes to start high-temperature sulfur-selenization. The temperature was then timed to be raised from 510°C to 570°C for 3.5 minutes, then cooled from 570°C to 510°C for 3.5 minutes, then raised from 510°C to 570°C for 3.5 minutes, then cooled from 570°C to 510°C for 3.5 minutes, thus completing the entire variable-temperature sulfur-selenization process. The heating rate from room temperature to 280°C for soft sulfur-selenization is 28.3°C / min, the heating rate from 280°C to 510°C for high-temperature variable-temperature sulfur-selenization is 25.5°C / min, and the temperature change rates from 510°C to 570°C and from 570°C to 510°C are both 17.1°C / min. The ratio of the quantity of the precursor film, the mass of stannous sulfide and the mass of the selenium pills is 1 piece: 1.25g: 125g.

2. The method for preparing a copper-zinc-tin-sulfur-selenide thin film by a variable temperature sulfur-selenide process according to claim 1, characterized in that: In step (1), the designed molar ratios of the metal elements Cu / (Zn+Sn) and Zn / Sn in the precursor solution are 0.72 and 1.14, respectively, the designed molar ratio of S / metal element is 1.86, the temperature of the constant temperature water bath is 60°C, the stirring speed is 666 r / min, and the stirring time is 3 hours.

3. The method for preparing a copper-zinc-tin-sulfur-selenide thin film by a variable temperature sulfur-selenide process according to claim 1, characterized in that: In step (2), the molybdenum glass includes 2 mm thick soda-lime glass and 1 μm thick molybdenum layer, and the thickness of the precursor film is 1.3 μm; and the spin coating speed is 3000 r / min, the time is 36 s; the baking temperature is 300 ° C, and the time is 2 min.

4. A copper-zinc-tin-sulfur-selenium thin film prepared by the method according to any one of claims 1 to 3.

5. A copper-zinc-tin-sulfur-selenium thin film solar cell, characterized in that: The copper-zinc-tin-sulfur-selenide thin film solar cell comprises the copper-zinc-tin-sulfur-selenide thin film according to claim 4.

6. The copper-zinc-tin-sulfur-selenium thin film solar cell according to claim 5, characterized in that: The copper-zinc-tin-sulfur-selenide thin-film solar cell has a structure of SLG / Mo / CZTSSe / CdS / i-ZnO / ITO / Ni-Al; and the preparation method of the copper-zinc-tin-sulfur-selenide thin-film solar cell is as follows: A 50nm thick cadmium sulfide (CdS) buffer layer was deposited on the CZTSSe film using chemical bath deposition, followed by a 50nm thick intrinsic zinc oxide (i-ZnO) and a 300nm thick tin-doped indium oxide (ITO) window layer using magnetron sputtering. Finally, nickel-aluminum (Ni-Al) electrodes were deposited using thermal evaporation to complete the CZTSSe solar cell. The efficiency of the copper-zinc-tin-sulfur-selenium thin film solar cell reaches 10.8%.

7. The copper-zinc-tin-sulfur-selenium thin film solar cell according to claim 6, characterized in that: The temperature of the chemical water bath deposition was 75°C and the rotation speed was 366 r / min; the background vacuum of the magnetron sputtering was 5×10 -4 Pa, the working pressure of sputtering i-Zno is 0.5Pa, the power and time are 35W-20min, 60W-5min; the working pressure of sputtering ITO is 0.3Pa, the power is 80W-90min.

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