CZTSSe absorption layer film and preparation method and application thereof

Abstract

The invention relates to the technical field of solar cells, in particular to a CZTSSe absorption layer film and a preparation method and application thereof, and the preparation method comprises the following steps: S1, preparing a CZTS precursor solution of a DMF solution system; s2, preparing a CZTS precursor film by adopting a sol-gel method; and S3, coating the CZTS precursor thin film with a NaF solution with the concentration of 0-0.2 mol / L, and then carrying out drying and selenylation treatment to obtain the CZTSSe absorption layer thin film. According to the invention, the CZTS precursor film prepared by using the green and environment-friendly solvent DMF is used for carrying out a NaF solution spin-coating annealing process, so that the improvement of the battery efficiency is successfully realized. The change of CZTSSe film element redistribution, defect chemical environment and grain boundary potential difference after the Na element is doped is avoided.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, and in particular to a CZTSSe absorber layer thin film, its preparation method, and its application. Background Technology

[0002] Among numerous thin-film solar cells, CZTSSe stands out due to its high abundance of constituent elements, non-toxicity, and excellent light absorption coefficient (>10). 4 cm -1 CZTSSe is considered an ideal material to replace CIGS and CdTe cells. Although the theoretical photoelectric conversion efficiency of CZTSSe can reach 32%, and its highest certified efficiency is currently 15.1%, it is far lower than that of CIGS (23.6%) and perovskite single-junction cells. The main reason for the low efficiency is that during the growth of CZTSSe thin films, problems such as Cu-Zn cation disorder, Sn-related deep-level defects, and lattice mismatch caused by S / Se composition gradient lead to severe nonradiative recombination of charge carriers, which reduces the transport efficiency of charge carriers in the bulk phase and at the interface.

[0003] In CIGS systems, the diffusion of Na from soda-lime glass (SLG) into the absorber layer has been shown to significantly improve grain size, passivate grain boundary defects, and optimize carrier transport capabilities. This phenomenon inspired researchers to introduce Na into CZTSSe systems and gradually reveal its multidimensional mechanism for regulating the optoelectronic properties of the material structure. There are many methods for introducing Na. Liu Fangyang's team dissolved NaCl solution into the precursor solution and found that Na ions not only promote grain growth at the top and bottom but also improve the quality of the CdS buffer layer, reducing non-radiative recombination of charge carriers. Wu Sixin's team used the AM-PDT method, evaporating NaF onto the prepared CZTSSe absorber film and then heat-treating it. They found that Na ions dispersed within the grains and grain boundaries, significantly increasing the acceptor concentration and passivating deep-level defects. Li Dongshan's team used an electron beam evaporator to deposit NaF layers onto a metal precursor. After selenization, they found that Na-doped batteries resulted in a high potential difference between the grain interior and grain boundaries, which was more conducive to carrier transport. William Jo's team deposited NaF layers at different locations on stacked precursors using thermal evaporation and found that the introduction of Na could reduce the grain boundary barrier and promote lateral grain growth. Applications of Na treatment in precursors are widespread, but they are mainly concentrated in the sputtering preparation of CZTSSe thin films, and the Na source is mostly obtained by thermally evaporating NaF. Therefore, it is worthwhile to study the strategy of using NaF solution for Na treatment based on the preparation of precursor films by the sol-gel method. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a CZTSSe absorber layer thin film, its preparation method and application, which can achieve the incorporation of Na element without sputtering, and at the same time improve the photoelectric conversion efficiency of the battery.

[0005] To achieve the above objectives, the present invention provides a method for preparing a CZTSSe absorber layer thin film, comprising the following steps: S1. Prepare CZTS precursor solution for DMF solution system; S2. CZTS precursor films were prepared using the sol-gel method; S3. A NaF solution with a concentration between 0 and 0.2 mol / L was coated onto the CZTS precursor film, and then dried and selenized to obtain the CZTSSe absorber film.

[0006] The method for preparing the CZTS precursor solution described in S1 is to dissolve thiourea and CuCl in DMF solution to form solution A, mix SnCl4, Zn(OAc)2 and DMF solution to form solution B, and stir and mix solution A and solution B to obtain a light yellow CZTS precursor solution; wherein, the molar ratio of Cu / (Zn+Sn) is 0.72 and the molar ratio of Zn / Sn is 1.04.

[0007] The method for preparing the CZTS precursor film described in S2 is to purify the CZTS precursor solution and then coat it onto a Mo substrate. After annealing at 420°C for 2 minutes and cooling, the spin coating is repeated 7 times to obtain the CZTS precursor film. The spin coating speed is 2800-3200 rpm and the spin coating time is 60 s.

[0008] The concentration of the NaF solution is 0.08-0.12 mol / L.

[0009] The thickness of the NaF coating is 1.5-2 μm.

[0010] The drying temperature described in S3 is 320℃, and the time is 2 minutes.

[0011] The selenization process in S3 is carried out in a square graphite box containing Se particles under an N2 atmosphere with a gas flow rate of 80 sccm. The selenization process is programmed as follows: the temperature is raised from room temperature to 350°C within 90 seconds and held at that temperature for 5 minutes; then the temperature is raised from 350°C to 540°C within 150 seconds and held at this temperature for 20 minutes, and then the furnace is allowed to cool naturally to room temperature.

[0012] The present invention also provides a CZTSSe absorber layer film, which is prepared by the aforementioned preparation method.

[0013] The present invention also provides the application of the CZTSSe absorber layer film in CZTSSe batteries.

[0014] This invention utilizes the environmentally friendly solvent DMF to prepare CZTS precursor films, followed by NaF solution spin-coating annealing, successfully improving battery efficiency. The invention explores changes in element redistribution, defect chemical environment, and grain boundary potential difference in the CZTSSe film after Na incorporation. Increased Na content within the CZTSSe absorber promotes crystal growth and effectively suppresses the formation of harmful secondary phases by regulating the distribution of Cu, S, and Se, thereby reducing back contact resistance. Defect passivation reduces carrier recombination losses and significantly improves minority carrier lifetime. Na incorporation also enhances the grain boundary contact potential difference and strengthens carrier separation capabilities.

[0015] The beneficial effects of this invention are: 1. In this invention, the optimization of the absorber layer by Na is due to the fluxing effect of Na₂Se. This effect enables rapid growth of CZTSSe grains, resulting in a dense surface and better interlayer contact. Simultaneously, the addition of Na reduces the bulk defect concentration, thus yielding a CZTSSe absorber layer with high crystal quality and low defect density. Furthermore, Na enrichment on the surface can passivate grain boundary defects and reduce the interfacial recombination rate.

[0016] 2. The main reason for the improved battery efficiency in this invention is the significant increase in FF (fat-free) which is closely related to the improved quality of the CZTSSe thin film. The enhanced EQE spectral response in the long wavelength range improves light utilization, and the reduction of the bulk defect density by an order of magnitude indicates that photogenerated carriers transport more rapidly within the CZTSSe absorber. The M-TPC and M-TPV test results show that the increased carrier lifetime and significant improvement in carrier collection and extraction efficiency of the NaF-0.12 battery also led to the improved FF. The battery's PCE ultimately increased from 11.08% to 12.50%, and the NaF-0.12 battery had a VOC of 502.41 mV, JSC of 36.32 mA / cm², and an FF of 68.51%. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only for this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a flowchart illustrating the preparation process of CZTS precursor films with different NaF concentrations according to the present invention. Figure 2(a) XRD patterns of CZTSSe absorption layers after selenization of precursor films with different NaF concentrations; Figure 2 (b) is a magnified view of the CZTSSe(112) diffraction peaks; Figure 3 (a) Normalized Raman spectra of CZTSSe films at different NaF concentrations; Figure 3 (b) FWHM of the characteristic peak of mode A under different NaF concentrations; Figure 3 (c) shows the B-mode characteristic peaks of CZTSSe films with different NaF concentrations; Figure 3 (d) is a magnified spectrum of the characteristic peaks of the E mode; Figure 4 (ac) are depth profiles of NaF-0, NaF-0.12, and NaF-0.16 thin films and Na element, respectively; Figure 5 The surface and cross-sectional morphologies of NaF-0 (a, b), NaF-0.08 (c, d), NaF-0.12 (e, f) and NaF-0.16 (g, h) films are shown. Figure 6 for Figure 6 (ad) represents the PCE of CZTSSe solar cells with different NaF concentrations. V OC , J SC And the statistical trend chart of FF; Figure 7 J–V curves for NaF-0 and NaF-0.12 batteries. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0020] It should be noted that, unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0021] Preparation of precursor solution

[0022] Immerse the screw-cap glass bottles, caps, gaskets, and rotors in aqua regia for more than 24 hours. Prepare two sets of immersed reagent bottles and rotors, rinse them thoroughly with deionized water, then rinse with anhydrous ethanol, and finally dry them in an oven. Add 21.05 mmol of thiourea (Tu) to reagent bottle 1 containing 4 mL of DMF solvent and stir magnetically until completely dissolved. Then add 5.88 mmol of CuCl to the above solution and continue stirring until completely dissolved. Add 4.00 mmol of SnCl4 to reagent bottle 2 and immediately inject 3 mL of DMF using a syringe. After reagent bottle 2 cools, add 4.16 mmol of Zn(OAc)2 and stir until a clear solution is formed. Finally, mix the solution from bottle 2 with the solution from bottle 1 and stir magnetically for one hour to obtain a light yellow CZTS precursor solution. Then immediately spin-coat or store in a low-temperature environment (0-10℃). All the above processes are carried out in a glove box filled with N2.

[0023] Preparation of NaF solutions of different concentrations

[0024] Four clean screw-top bottles were rinsed with deionized water and dried in a drying oven. 0 g, 0.0336 g, 0.0504 g, and 0.0672 g of NaF were added to each bottle, respectively. Then, 10 mL of deionized water was measured using a syringe, and the solution was stirred for 10 min to ensure complete dissolution of the NaF particles. Different concentrations of NaF solutions were prepared by varying the amount of NaF added, resulting in molar concentrations of 0, 0.08, 0.12, and 0.16 mol / L. The dissolved NaF solutions were colorless and transparent liquids.

[0025] Preparation of CZTSSe thin films

[0026] The precursor film was prepared in two steps: sol-gel method and selenization. Mo-coated soda-lime glass and other experimental materials were placed in an N2-filled glove box, where both oxygen and water concentrations were less than 20 ppm. Two 2 mm filters were installed between the syringe barrel and needle to filter the prepared precursor solution. The spin coater was set to 3000 rpm with a spin coating time of 60 s. Using the adjusted syringe, the precursor solution was uniformly drop-coated onto the Mo substrate. The instrument was turned on, and after the spin coater stopped, the sample was immediately placed on a heating stage for annealing (temperature set to 420℃) for 2 min. After the sample cooled naturally, spin coating was continued. This process was repeated 7 times to obtain the CZTS precursor film.

[0027] Subsequently, keeping the spin-coating parameters (spin speed and time) constant, NaF solutions of different concentrations were sequentially coated onto the surfaces of four precursor films and dried on a hot stage at 300°C for 2 min. The preparation process is as follows: Figure 1As shown. The above precursor films were subjected to selenization treatment to obtain CZTSSe films. The specific method was as follows: the prepared CZTS precursor films were placed in a square graphite box containing Se particles and annealed in a rapid thermal treatment furnace. Under an N2 atmosphere with a gas flow rate of 80 sccm, the selenization process was programmed as follows: the temperature was rapidly increased from room temperature to 350°C within 90 s and held at this temperature for 5 min; subsequently, the temperature was increased from 350°C to 540°C within 150 s and held at this temperature for 20 min. Then, the furnace was allowed to cool naturally to room temperature. This completed the preparation of the CZTSSe films, which were named NaF-0, NaF-0.08, NaF-0.12, and NaF-0.16 films, respectively.

[0028] Characterization and analysis of CZTSSe thin films after NaF coating

[0029] Figure 2 (a) shows the XRD patterns of CZTSSe absorber layers after selenization with precursor films of different NaF concentrations. The diffraction peaks marked with ☀ represent Mo, and those marked with ★ represent Kesterite-structured CZTSSe. Comparison revealed that the diffraction peaks are consistent with those of #CZTSJCPDS6-0575 and #CZTSeJCPDS52-0868, and no obvious secondary phase was observed. To further investigate the effect of NaF coating on the crystallinity of the absorber layer, Figure 2 (b) is a magnified image of the CZTSSe (112) diffraction peak. The results show that the position shift of the (112) peak is not significant, fluctuating only within a very small range, which may be due to testing errors during instrument use. The full width at half maximum (FWHM) of the (112) peak was fitted using Origin software. The FWHM showed a trend of first decreasing and then increasing with increasing NaF concentration, according to the Scherrer formula: in D Grain size, λ For wavelength, β The half-width at half maximum (WHM) of the diffraction peak. θ It is half the diffraction angle. θ The smaller the concentration, the larger the grain size. Calculations from the test results show that with increasing NaF concentration, the NaF-0.12 (112) peak has the smallest FWHM, indicating the best crystallinity and the largest grain size. This suggests that coating with NaF promotes increased crystallinity of the absorption layer, but the grain size of the NaF-0.16 film decreases, indicating that the quality of the absorption layer grains deteriorates when the NaF concentration is too high.

[0030] To characterize the microstructure of the thin film sample based on XRD and to further detect the presence of a secondary phase, Raman scattering spectroscopy was performed at an excitation wavelength of 532 nm. Figure 3 (a). Located at 172 cm -1 192 cm -1 and 234 cm -1 The main characteristic peaks at this location correspond to the B, A, and E modes of CZTSSe, respectively, and are located at 245 cm⁻¹. -1 The weak Raman peak at the point indicates that the ZnSe phase is present, suggesting that the film surface is mainly composed of CZTSSe and a small amount of secondary phase. Figure 3 (b) The FWHM of the A-mode characteristic peaks were summarized. It can be found that with the increase of NaF concentration, the FWHM of the A-mode characteristic peaks first decreases and then increases. The FWHM of the A-mode characteristic peaks of the NaF-0.12 film is the smallest, which indicates that the grain size of the NaF-0.12 film is the largest, which is consistent with the XRD test results. The results of Dimitrievska et al. show that the changes in the intensity of certain modes in the Raman spectrum are related to the most important charge-compensating defect clusters in the CZTSSe film (i.e., [V Cu +Zn Cu ] and [2Cu Zn +Sn Zn This relates to changes in [ ]). In such cases... Figure 3 (c) The characteristic peak of the B mode gradually decreases, which means that the favorable defect clusters [V Cu +Zn Cu The density of ] increases. Figure 3 The results in (d) show that the E-mode characteristic peak gradually decreases with increasing NaF concentration, indicating that [2Cu] Zn +Sn Zn The density of harmful defect clusters decreases.

[0031] In summary, the results indicate that the strategy of treating the precursor with NaF solution can not only promote the crystallinity of CZTSSe crystals, but also significantly reduce the density of harmful defects, and to a certain extent suppress the band gap fluctuations and electrostatic potential fluctuations caused by Cu-Zn cation disorder.

[0032] To investigate the effect of the NaF coating on the elemental distribution in the absorber layer, GDOES tests were performed on the CZTSSe thin film. The CZTSSe / Mo back interface was approximately located at 140 s etching time. Figure 4 (ac) shows a comparison of the elemental composition of NaF-0, NaF-0.12, and NaF-0.16 films. Observation reveals that, apart from variations in the distribution range and content of Na, the contents of other elements show no significant differences. To more intuitively observe the changes in Na content, the Na distribution curves of the three samples are compared side-by-side, as shown below. Figure 4 (d) After coating with a NaF layer, Na in the absorber layer is enriched at both the front and back interfaces, and the total Na content increases due to the additional NaF coating. The peak Na content of both NaF-0 and NaF-0.12 films is around 80 s at the etching time, but the Na peak of NaF-0.12 is significantly higher. The higher Na content in the precursor facilitates the formation of the low-melting-point Na-Se phase during selenization, thereby promoting grain growth. However, when the NaF coating concentration is further increased, the Na peak of the Na-0.16 film moves closer to the back interface, and the Na distribution range within the absorber layer is wider than that of NaF-0 and NaF-0.12. Excessive Na enrichment at the back interface leads to an increase in local defect concentration, while excessive accumulation of the Na-Se phase in the later stages of selenization can cause pores at grain boundaries, forming carrier recombination centers. Excessive Na will accumulate excessively at the grain boundaries of CZTSSe thin films, forming an excessively thick passivation layer that hinders the effective migration of charge carriers between grain boundaries, resulting in longer transport paths and increased scattering probability. On the other hand, high concentrations of NaF will reduce crystal quality and crystallinity, weakening the long-range transport capability of charge carriers.

[0033] Figure 5 (a), (c), (e), and (g) are surface morphology images of NaF-0, NaF-0.08, NaF-0.12, and NaF-0.16 films, respectively. All surface morphology images show surfaces with bulky grains. Unlike NaF-0 and NaF-0.08, which have smaller grain sizes and more surface voids, the NaF-0.12 film surface is quite dense with more large grains. Combined with GDOES analysis, the increased crystallinity is found to be related to the fluxing effect of the Na-Se phase introduced by Na. Cross-sectional morphology images are shown below. Figure 5As shown in (b), (d), (f), and (h), observation reveals that the absorption layer of each sample is a sandwich structure consisting of large upper and lower grains interspersed with finer grains in the middle. With increasing NaF concentration, the large upper and lower grains grow bidirectionally, while the thickness of the middle grain layer gradually decreases. Sample NaF-0.12 exhibits the best grain contact in the depth direction. In contrast, sample NaF-0.16 shows obvious voids on its surface and cross-section. Excessive Na content in the CZTSSe absorption layer creates a strong fluxing effect, which, while promoting grain growth, leads to void formation during annealing and cooling due to thermal expansion and contraction. GDOES analysis shows an enhanced Na peak signal in sample NaF-0.12, corresponding to the growth and densification of the small grain layer in the absorption layer cross-section. In contrast, the Na peak signal in sample NaF-0.16 shifts and is widely distributed in the depth direction, resulting in poor contact between the large and small grain layers. This is because high NaF concentration reduces crystal quality and crystallinity, weakening the long-range transport capability of charge carriers. The average particle size of sample NaF-0.12 was 1.75 μm, slightly larger than the other three samples. The above analysis indicates that after coating with a NaF layer, Na, within a certain range, can promote the growth of CZTSSe thin films and significantly improve the contact between grains of different sizes within the absorption layer. However, excessive Na will accumulate excessively at the grain boundaries of the CZTSSe thin film, forming an overly thick passivation layer that hinders the effective migration of charge carriers between grain boundaries, resulting in a longer transport path and increased scattering probability.

[0034] Fabrication of CZTSSe thin-film solar cells

[0035] Preparation of CdS buffer layer

[0036] A CdS buffer layer of approximately 50 nm thickness was deposited on the surface of a CZTSSe film using a chemical bath deposition method. The chemical reaction formula for this process is as follows:

[0037] The specific preparation process is as follows: Pour 250 mL of deionized water into a clean beaker and place it on a stirring table with a rotation speed of 500 r / min; weigh 0.0768 g of cadmium sulfate (CdSO4·8 / 3H2O) powder and add it to the beaker, stirring for 5 min until the powder is completely dissolved; then add 13 mL of ammonia water to the beaker and stir for 5 min; place the CZTSSe sample in a PTFE sample holder in a clockwise direction and suspend it in the beaker while stirring; then add 0.11 g of thiourea and stir for 5 min, then place the beaker in a water bath at 70℃ for stirring. Observe the color change of the film surface; it first changes from grayish-white to light purple, and when it continues to turn bluish-purple, immediately remove the sample. Rinse the sample surface with deionized water and anhydrous ethanol, and finally dry it in a drying oven at 60℃.

[0038] Fabrication of window layer and top electrode The window layer of CZTSSe solar cells was prepared by radio frequency magnetron sputtering. The SLG / Mo / CZTSSe / CdS sample was placed on a photomask, and the dust on the film surface was cleaned with a syringe. The sample was then placed inside the magnetron sputtering chamber, and the processes of vacuuming, pre-sputtering, and sputtering were performed sequentially. The specific fabrication parameters obtained through experiments are shown in Table 1 below. Table 1. Window layer fabrication process parameters

[0039] The top electrode was prepared using a thermal evaporation method. The prepared sample was fixed on a mask and placed in a chamber for vacuum deposition of an Ag electrode approximately 120 nm thick. Finally, mechanical scribing was used to divide the sample into nine sections with an effective area of ​​0.19 cm². 2 Independent battery.

[0040] Characterization and analysis of CZTSSe cells after NaF coating Figure 6 (ad) represents the PCE of CZTSSe solar cells with different NaF concentrations. V OC , J SC The statistical trend of FF. The average PCE increased from 11.00% (NaF-0) to 12.25% (NaF-0.12). However, the average PCE of NaF-0.16 cells decreased sharply, which is related to... Figure 5 The deterioration in crystal quality, as shown in the SEM cross-sectional images, is related to the excess Na. With increasing NaF concentration, V OC and J SC The change was not significant, only a slight increase, but the NaF-0.16 battery... V OC and J SC However, it decreased rapidly. The change in FF was exactly the opposite; as the NaF concentration increased, FF first rose continuously and then decreased slightly. Therefore, it can be concluded that the improvement in PCE of the NaF-0.12 cell mainly comes from the significant increase in FF, while the decrease in PCE of the NaF-0.16 cell is due to... V OC and J SCThe sharp decrease in [unclear - possibly related to a specific characteristic or parameter]. Analysis of SEM cross-sectional images reveals that the improvement in FF is related to the optimization of the CZTSSe fine-grained layer. The addition of Na thins the fine-grained layer and improves the contact between the large and fine grain layers, reducing carrier recombination at grain boundaries. Meanwhile, the NaF-0.16 battery... V OC and J SC The decrease may be due to defects caused by the imbalance of elemental ratio in the absorber layer caused by excessive Na and the secondary ZnSe phase, which is consistent with the results of Raman testing.

[0041] In order to investigate the fundamental reasons and possible mechanisms by which Na improves the efficiency of CZTSSe, Figure 7 For batteries NaF-0 and NaF-0.12 JV The curves were studied in detail. Coating with NaF significantly improved the PCE of the battery. J SC , V OC The values ​​for FF are 502.41 mV and 36.32 mA / cm. 2 With a PCE of 68.51%, the NaF-0.12 battery achieved a champion PCE of 12.50% without any antireflective layer. The efficiency improvement of NaF-0.12 compared to NaF-0 is mainly attributed to the increase in FF from 63.00% to 68.51%.

[0042] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity. Any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. A method for preparing a CZTSSe absorber layer thin film, characterized in that, Includes the following steps: S1. Prepare CZTS precursor solution for DMF solution system; S2. CZTS precursor films were prepared using the sol-gel method; S3. A NaF solution with a concentration between 0 and 0.2 mol / L was coated onto the CZTS precursor film, and then dried and selenized to obtain the CZTSSe absorber film.

2. The method for preparing the CZTSSe absorber layer film according to claim 1, characterized in that, The method for preparing the CZTS precursor solution described in S1 is to dissolve thiourea and CuCl in DMF solution to form solution A, mix SnCl4, Zn(OAc)2 and DMF solution to form solution B, and stir and mix solution A and solution B to obtain a light yellow CZTS precursor solution; wherein, the molar ratio of Cu / (Zn+Sn) is 0.72 and the molar ratio of Zn / Sn is 1.

04.

3. The method for preparing the CZTSSe absorber layer thin film according to claim 1, characterized in that, The method for preparing the CZTS precursor film described in S2 is to purify the CZTS precursor solution and then coat it onto a Mo substrate. After annealing at 420°C for 2 minutes and cooling, the spin coating is repeated 7 times to obtain the CZTS precursor film. The spin coating speed is 2800-3200 rpm and the spin coating time is 60 s.

4. The method for preparing the CZTSSe absorber layer film according to claim 1, characterized in that, The concentration of the NaF solution is 0.08-0.12 mol / L.

5. The method for preparing the CZTSSe absorber layer thin film according to claim 1, characterized in that, The thickness of the NaF coating is 1.5-2 μm.

6. The method for preparing the CZTSSe absorber layer film according to claim 1, characterized in that, The drying temperature described in S3 is 320℃, and the time is 2 minutes.

7. The method for preparing the CZTSSe absorber layer film according to claim 1, characterized in that, The selenization process in S3 is carried out in a square graphite box containing Se particles under an N2 atmosphere with a gas flow rate of 80 sccm. The selenization process is programmed as follows: the temperature is raised from room temperature to 350°C within 90 seconds and held at that temperature for 5 minutes; then the temperature is raised from 350°C to 540°C within 150 seconds and held at this temperature for 20 minutes, and then the furnace is allowed to cool naturally to room temperature.

8. A CZTSSe absorber layer film, characterized in that, It is prepared by the preparation method described in any one of claims 1-7.

9. The application of the CZTSSe absorber layer film according to claim 8 in a CZTSSe battery.

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