A kind of CIGS thin film and its preparation method and application for high-stable self-driven CIGS photoelectric detector

Abstract

This invention discloses a CIGS thin film, its preparation method, and its application in a high-stability self-powered CIGS photodetector, belonging to the fields of materials preparation technology and photoelectric detection. First, soda-lime glass is selected as the substrate, cut, cleaned, and dried. Then, a Mo back electrode is sputtered onto the treated substrate to obtain Mo-plated soda-lime glass. A precursor solution is spin-coated and then heated and dried to prepare a CIG precursor. Finally, a high-temperature selenization treatment is performed to obtain the CIGS thin film. The CIGS thin film prepared by this invention solves the problems of excessively porous structure and small grain size in CIGS thin films prepared by the precursor solution method. It effectively reduces the internal defect density of the film and reduces carrier recombination, resulting in a CIGS absorber layer film with large grains, excellent photoelectric performance, low internal defect density, and low carrier recombination. This allows for application in a self-powered CIGS photodetector with excellent photoelectric response performance and high signal stability.

Description

Technical Field

[0001] This invention belongs to the fields of materials preparation technology and photoelectric detection, specifically relating to a CIGS thin film, its preparation method, and its application in a highly stable self-driven CIGS photodetector. Background Technology

[0002] In the field of photoelectric detection technology, with the rapid development of emerging fields such as artificial intelligence, the Internet of Things, and wearable devices, the demand for low power consumption, high signal sensitivity and stability, and wide spectral response in detection devices is becoming increasingly urgent, becoming the core indicators driving the continuous development of photoelectric detectors. Currently, mainstream traditional photoelectric detectors generally suffer from three bottlenecks: first, the fixed bandgap of the material itself leads to a limited spectral response range; second, insufficient light absorption efficiency prevents efficient light capture, directly affecting the device's response speed; and third, reliance on external bias power supply makes it difficult to meet the needs of self-driven applications such as IoT sensing nodes and wearable devices. These problems hinder the widespread application of photoelectric detectors.

[0003] Copper indium gallium selenide (CIGS) thin films, as a multi-element direct bandgap semiconductor material, have previously been primarily studied in the field of solar cells, with their application in photoelectric detection lacking systematic research and development. It is particularly noteworthy that the working principle of photovoltaic photodetectors is the same as that of thin-film solar cells, both based on the photovoltaic effect of pn junctions. This provides a theoretical possibility for extending CIGS heterojunctions into the field of photoelectric detection. From the intrinsic properties of CIGS materials, they possess a high absorption coefficient (>10). 5 cm -1 CIGS thin films possess adjustable band gaps and high environmental stability, and their pn junction-based photovoltaic effect characteristics are naturally compatible with the self-driving principle. Therefore, using CIGS thin films as photodetectors has significant potential advantages in addressing the bottlenecks of mainstream detectors.

[0004] The precursor solution method is one of the mainstream technologies for preparing CIGS thin films, with advantages such as low cost, simple process, and flexible component control. The crystallinity of CIGS crystals is the main factor affecting their photoelectric detection performance, and the selenization process is the core step in this method that determines the crystallinity of CIGS thin films. The higher the selenization temperature, the lower the defect density of CIGS crystals and the narrower the band gap; however, if the selenization temperature is too high, it leads to more internal defects and pores in the film, and the band gap actually widens. Thin films prepared by the precursor solution method still have the problem of uneven distribution of Se element after selenization, which means that the film density still needs to be optimized. Therefore, the problem of how to make the Se element more thoroughly bonded to the precursor film still needs to be solved. In view of the above-mentioned shortcomings in optimizing the selenization process, this invention explores the optimal selenization temperature and proposes a layered selenization method to solve the problem of selenization process optimization.

[0005] Besides the selenization process, the concentration and distribution of Cu on the performance of CIGS thin films also pose a challenge for the application of CIGS thin-film photodetectors in the field of photoelectric detection. During the recrystallization process of CIGS thin films, a significant amount of Cu is generated at the interface between copper-rich and copper-poor regions. x Se phase, and this liquid phase Cu x Se promotes the growth of CIGS grains, but at the same time, residual Cu... x Se will cause a shunting effect, affecting the electrical properties of CIGS films. Therefore, controlling Cu... x The formation and decomposition of the Se phase are key factors in regulating the influence of Cu on thin film properties. This invention regulates Cu content by constructing a Cu gradient to obtain a copper-poor-copper-rich-copper-poor thin film structure. x The formation and decomposition of the Se phase were compared and found to have a synergistic effect of Cu gradient and layered selenization on the photoelectric detection performance of CIGS thin films. Summary of the Invention

[0006] To address the key issues of existing photodetectors in self-powered scenarios, such as slow response speed, poor signal stability, and insufficient detection sensitivity, this invention aims to further optimize their low power consumption and signal stability, achieving low-cost fabrication of high-performance CIGS-based photodetectors. This invention focuses on the selenization process and Cu gradient in the CIGS thin film fabrication process to modulate its band structure and thus optimize its photodetector performance. This invention provides a CIGS thin film, its fabrication method, and its application in a highly stable self-driven CIGS photodetector.

[0007] A method for preparing a CIGS thin film includes the following steps: First, soda-lime glass is selected as a substrate, cut, cleaned and dried; then, a Mo back electrode is sputtered onto the treated substrate to obtain Mo-plated soda-lime glass; a precursor solution is spin-coated and heated and dried to prepare a CIG precursor; finally, the CIG precursor film is subjected to high-temperature selenization treatment to obtain a CIGS thin film.

[0008] Further, the soda-lime glass is cut into 2cm×2cm pieces; the cleaning process involves wiping the surface of the soda-lime glass with an alcohol swab, followed by ultrasonic cleaning with deionized water and anhydrous ethanol for 3 minutes each, with the ethanol cleaning being repeated twice; after cleaning, the substrate is placed in an electric thermostatic drying oven for drying and later use.

[0009] Furthermore, the sputtering process parameters are: base vacuum 8×10⁻⁶ -4 Pa-8×10 -5 Pa, sputtering power 100W-200W, working gas pressure 1Pa-2Pa, argon flow rate 10sccm-30sccm, sputtering time 3min-10min, forming a Mo back electrode with a thickness of 300nm-450nm.

[0010] Further, the preparation steps of the precursor solution are as follows: In a glove box, firstly, 0.500g-1.500g of thiourea is mixed and dissolved with 1mL-10mL of DMF, then 0.200g-1.00g of CuCl is added and stirred until completely dissolved to obtain solution A; then, 0.500g-1.500g of thiourea is mixed and dissolved with 1mL-10mL of DMF, then 1.000g-1.500g of InCl3·4H2O and 0.10g-0.50g of GaCl3 are added and stirred until clear to obtain solution B; solutions A and B are mixed and stirred for 4-6 hours, aged for 10-12 hours, and filtered through a 0.22μm filter membrane for later use. The water and oxygen content in the glove box is <5ppm, and the environment is at room temperature.

[0011] Further, the spin coating process involves fixing the Mo-coated soda-lime glass onto a spin coater, rotating it at a low speed of 450 r / min-550 r / min for 30-50 seconds, then rotating it at a high speed of 1100 r / min-1250 r / min for 55-70 seconds, and adding a precursor solution to form a wet film. The heating and drying process involves heating the spin-coated glass at 150℃-200℃ for 20-40 seconds and drying it. The spin coating-drying process is repeated 5-6 times, and finally, the glass is pre-annealed at 270℃-350℃ for 25-40 minutes.

[0012] Furthermore, the high-temperature selenization treatment is as follows: using solid Se powder as the Se source, 40mg-60mg of Se powder and the CIG precursor membrane are placed face-to-face in a graphite box with a spacing of about 0.7cm-1.5cm, and a quartz tube is placed in. Then, the process of introducing argon gas, evacuating the vacuum, and introducing argon gas again is repeated 4-6 times, and the air in the tube is purged. After setting the argon gas flow rate to 5sccm-10sccm, the tube furnace is started to heat up to 540℃-570℃. Then, the graphite box is pushed into the furnace for selenization. After the process is completed, it is removed and allowed to cool naturally to room temperature.

[0013] A CIGS thin film prepared by the above method.

[0014] An application of CIGS thin film in a highly stable self-driven photodetector.

[0015] Further, the preparation method of the highly stable self-driven CIGS photodetector is as follows: First, a CdS buffer layer is deposited by chemical bath deposition. Specifically, 0.400g-0.430g of thiourea is weighed and dissolved in 6mL-7mL of deionized water, stirred and preheated to 60℃-70℃ for later use; 0.025g-0.030g of CdSO4 is weighed and dissolved in 6mL-7mL of deionized water, and then the CdSO4 solution is mixed with 9mL-10mL of ammonia water into a beaker containing 50mL of deionized water, placed in a water bath preheated to 65℃ and stirred, and then the preheated thiourea solution is poured in and stirred slowly to obtain a mixed solution; the CIGS thin film sample is immersed in the mixed solution and deposited in a water bath for 7min-10min, and then taken out to obtain the deposited CIGS thin film; then, i-ZnO and ITO layers are prepared on the deposited CIGS thin film by magnetron sputtering, wherein the sputtering parameters of i-ZnO are a base vacuum of 5×10⁻⁶. -4 Pa-8×10 -4 Pa, sputtering power 90W-120W, argon-oxygen ratio (20-25):(10-15), working pressure 1Pa-2Pa, deposition 3min-5min; ITO sputtering parameters are local vacuum 5×10 -4 Pa-8×10 -4 Pa, sputtering power 90W-120W, argon-oxygen ratio (35-40):(0.5-1.5), working pressure 0.3Pa-1Pa, deposition time 7min-12min; finally, Al top electrode was prepared by vacuum evaporation. Before evaporation, a mask was used to cover the sample surface, exposing only the electrode position. When the local vacuum reached 3.00×10 -3 Turn on the power supply of the vapor deposition instrument at Pa, quickly adjust the vapor deposition current to 120A, hold for 3s~5s, and then quickly adjust the reading to 0. After the vapor deposition is completed, turn off the vapor deposition power supply and the molecular pump. After the instrument stabilizes, take out the sample to obtain a highly stable self-driven photodetector.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] This invention employs a simple, widely applicable, and easily controllable precursor solution method, combined with a simplified monoselenide selenization process, to prepare a self-powered CIGS photodetector with rapid photoelectric response and high signal stability. In principle, the precursor solution mainly consists of a solvent and a precursor compound. Various parameters of the solvent, such as viscosity, surface tension, saturated vapor pressure, boiling point, and its interaction with the precursor compound, significantly influence the formation of the CIGS film's light-absorbing layer. Finding a suitable non-hydrazine solvent is crucial. This invention uses DMF as the solvent for the precursor solution. The crystallinity of the CIGS film is optimized through selenization process optimization and reasonable control of the Cu gradient. A layered selenization method is employed to solve the problems of overly porous structure and small grain size in CIGS films prepared by the precursor solution method. This effectively reduces the internal defect density of the film and carrier recombination, resulting in a CIGS absorber film with large grains, excellent photoelectric performance, low internal defect density, and low carrier recombination. This leads to a self-powered CIGS photodetector with excellent photoelectric response and high signal stability. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the photodetector device prepared according to an embodiment of the present invention.

[0019] Figure 2 The XRD spectra are those of samples prepared after selenization treatment at different pre-annealing temperatures in Example 4 of this invention.

[0020] Figure 3 The images shown are SEM images of samples prepared at different pre-annealing temperatures in Example 4 of the present invention. Figures (a)-(f) are SEM images of cross-sections of samples prepared at pre-annealing temperatures of 270℃, 290℃, 310℃, 330℃, and 350℃, respectively.

[0021] Figure 4 The XRD spectra are those of samples prepared with different amounts of thiourea in Examples 1-5 of this invention.

[0022] Figure 5 The images shown are SEM images of samples prepared with different amounts of thiourea in Examples 1-5 of the present invention. Figures (a)-(f) are SEM images of cross-sections of the samples prepared in Examples 1-5 of the present invention, respectively.

[0023] Figure 6 The XRD spectra are those of samples prepared by different selenization processes in Example 6 of this invention.

[0024] Figure 7These are SEM images of samples prepared under different selenization processes in Example 6 of the present invention, wherein (a) is a single selenization, (b) is a layered selenization, and (c) is a cross-sectional image of the layered selenization sample.

[0025] Figure 8 These are the XRD spectra of different Cu gradients in Example 7 of the present invention.

[0026] Figure 9 These are Raman spectra of different Cu gradients in Example 7 of the present invention.

[0027] Figure 10 These are SEM images of different Cu gradients in Example 7 of the present invention, where Figures (a)-(f) are SEM images of N sample, Cu1 sample, Cu2 sample, N sample, Cu1 sample, and Cu2 sample, respectively.

[0028] Figure 11 This is the EDS line scan element concentration variation curve in the optimal Cu gradient cross section direction of Embodiment 7 of the present invention.

[0029] Figure 12 This is a schematic diagram illustrating the changes in resistivity, carrier mobility, and carrier concentration at different Cu gradients in Embodiment 7 of the present invention.

[0030] Figure 13 This is the It response curve of the optimal Cu gradient within 20000s in Example 7 of the present invention.

[0031] Figure 14 The optimal Cu gradient in Example 7 of this invention is the photocurrent (I) within 20000s. light ) and dark current (I dark ) Change curve. Detailed Implementation

[0032] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0033] A method for preparing a CIGS thin film includes the following steps: using a 2×2cm soda-lime glass substrate, wiping with an alcohol swab, ultrasonically cleaning with deionized water and anhydrous ethanol (repeated twice) for 3 minutes each, and then drying for later use; the Na element in the soda-lime glass can passivate defects in the CIGS thin film and is resistant to high-temperature selenization without deformation; and using a JGP-450A magnetron sputtering deposition system at a base vacuum of 8×10⁻⁶ cm⁻¹. -4 Pa-8×10 -5Under the conditions of Pa, sputtering power of 100W-200W, working gas pressure of 1Pa-2Pa, argon flow rate of 10sccm-30sccm, and sputtering time of 3min-10min, a low resistivity Mo back electrode with a thickness of 300nm-450nm that can form good ohmic contact with the CIGS layer is formed; in a glove box with a water oxygen content of <5ppm, 1.100g-1.200g of thiourea is first mixed and dissolved with 1mL-10mL of DMF, and then 0.200g-1.000g of CuCl is added and stirred until completely dissolved to obtain solution A; then 1.100g-1.200g of thiourea is mixed and dissolved with 1mL-10mL of DMF, and then 1.000g-1.500g of CuCl is added. InCl3·4H2O and 0.10g-0.50g GaCl3 were stirred until clear to obtain solution B. Solution A and solution B were mixed and stirred for 4-6 hours, aged for 10-12 hours, and then filtered through a 0.22μm filter membrane to obtain a stable, residue-free CIG precursor solution. DMF, as a non-hydrazine solvent, ensured solution stability and no residual effects. The Mo-plated substrate was fixed on a spin coater and spin-coated with the precursor solution by low-speed rotation at 450-550r / min for 30-50s and high-speed rotation at 1100-1250r / min for 55-70s. The solution was then dried on a hot table at 150-200℃ for 20-40s. This spin-coating-drying process was repeated 5-6 times, followed by holding at a hot table at 270-350℃ for 25 seconds. Pre-annealing was performed for 1 to 40 minutes to promote complex formation and remove solvent. Finally, 40-60 mg of solid Se powder was used as the selenium source and placed face-to-face with the CIG precursor film in a graphite box with a spacing of 0.7-1.5 cm. A quartz tube that had been repeatedly purged with argon gas was placed in the box. After the tube furnace was heated, the film was pushed into the graphite box for high-temperature selenization. After the process was completed, the film was removed and allowed to cool naturally to room temperature, so that Cu, In, Ga and Se could react to form a chalcopyrite-structured CIGS film.

[0034] An application of CIGS thin films in highly stable self-driven photodetectors, such as... Figure 1As shown, the preparation method of the highly stable self-driven CIGS photodetector is as follows: First, a CdS buffer layer is deposited by chemical bath deposition. Specifically, 0.400g-0.430g of thiourea is weighed and dissolved in 6mL-7mL of deionized water, stirred and dissolved, and preheated to 60℃-70℃ for later use; 0.025g-0.030g of CdSO4 is weighed and dissolved in 6mL-7mL of deionized water, and then the CdSO4 solution is mixed with 9mL-10mL of ammonia water into a beaker containing 50mL of deionized water, placed in a water bath preheated to 65℃ and stirred, and then the preheated thiourea solution is poured in and stirred slowly to obtain a mixed solution; the CIGS thin film sample is immersed in the mixed solution and deposited in a water bath for 7min-10min, and then taken out to obtain the deposited CIGS thin film; then, i-ZnO and ITO layers are prepared sequentially on the deposited CIGS thin film by magnetron sputtering, wherein the sputtering parameters of i-ZnO are a base vacuum of 5×10⁻⁶. -4 Pa-8×10 -4 Pa, sputtering power 90W-120W, argon-oxygen ratio (20-25):(10-15), working pressure 1Pa-2Pa, deposition 3min-5min; ITO sputtering parameters are local vacuum 5×10 - 4 Pa-8×10 -4 Pa, sputtering power 90W-120W, argon-oxygen ratio (35-40):(0.5-1.5), working pressure 0.3Pa-1Pa, deposition time 7min-12min; finally, Al top electrode was prepared by vacuum evaporation. Before evaporation, the electrode position was defined using a mask. When the local vacuum reached 3.00×10 -3 Turn on the power of the vapor deposition instrument at Pa, quickly adjust the vapor deposition current to 120A, hold for 3s-5s, and then quickly adjust the reading to 0. After the vapor deposition is completed, turn off the vapor deposition power supply and the molecular pump. After the instrument stabilizes, take out the sample to obtain a highly stable self-driven photodetector.

[0035] Through the above process steps and parameter control, the final CIGS thin film has a micro-particle size of 4μm, thus producing a CIGS photodetector thin film with good cross-sectional density, uniform selenium distribution, excellent crystallinity and photoelectric properties.

[0036] Example 1

[0037] A method for preparing a CIGS thin film includes the following steps:

[0038] (1) Cleaning of the substrate

[0039] Sodium-calcium glass was selected as the substrate and cut into 2cm×2cm sizes. After wiping the surface stains with alcohol cotton balls, it was rinsed repeatedly with deionized water, ultrasonically cleaned with deionized water for 3 minutes, and then ultrasonically cleaned with anhydrous ethanol for 3 minutes (repeated twice). Finally, it was placed in an electric heating constant temperature drying oven to dry for later use.

[0040] (2) Sputtering Mo back electrode

[0041] The process employs DC magnetron sputtering with a base vacuum of 8×10⁻⁶. -4 Pa, sputtering power 150W, working pressure 1.4Pa, argon flow rate 10sccm, sputtering time 8min, to prepare a Mo back electrode with a thickness of about 300nm;

[0042] (3) Prepare CIG precursor solution (TU / M=1.5)

[0043] In a glove box at room temperature with a water oxygen content of <5ppm, add 0.571g thiourea and 3mL DMF to sample vial 1, dissolve, then add 0.495g CuCl and stir until completely dissolved; add 0.571g thiourea and 3mL DMF to sample vial 2, dissolve, then add 1.300g InCl3·4H2O and 0.20g GaCl3 sequentially, stirring until the solution is clear each time; mix the two solutions and stir for 5h, age for more than 10h, then filter through a 0.22μm filter membrane for later use;

[0044] (4) Spin coating to prepare CIG precursor films

[0045] Mo-coated sodium-calcium glass was fixed on the suction cup of a spin coater. After removing surface dust, the precursor solution was added, and the film was spin-coated by rotating at a low speed of 520 r / min for 40 s and then at a high speed of 1200 r / min for 55 s. The film was then dried by heating on a hot table at 150℃ for 30 s, and after cooling for 1 min-2 min, the spin-coating-drying process was repeated 5-6 times. Finally, the film was pre-annealed at 330℃ for 25 min to obtain the CIG precursor film.

[0046] (5) Selenization treatment

[0047] 50 mg of solid Se powder and CIG precursor film (face down) were placed in a graphite box with a spacing of about 1 cm. After the graphite box was placed in a quartz tube, it was evacuated and filled with argon gas three times. After the tube furnace was heated to the set temperature, the graphite box was pushed in for rapid heating and selenization. After selenization was completed, the graphite box was removed and allowed to cool naturally to room temperature, so that the precursor decomposed and generated chalcopyrite-structured CIGS.

[0048] A method for fabricating a highly stable self-driven CIGS photodetector includes the following steps:

[0049] ① Chemical bath deposition of CdS buffer layer: At 65℃, the film was immersed in a mixed solution containing 0.430g thiourea, 0.030g CdSO4, 9.3mL ammonia and 50mL deionized water, and deposited for 8min; ② Magnetron sputtering preparation of i-ZnO and ITO layers: i-ZnO (base vacuum 8×10 -4 Pa, sputtering power 110W, argon-oxygen ratio 23:13, working pressure 1.8Pa, deposition time 5min), ITO (baseline vacuum 8×10 -4 Pa, sputtering power 110W, argon-oxygen ratio 38:0.5, working pressure 0.3Pa, deposition time 7min); ③ Vacuum evaporation of Al top electrode: after masking, the base vacuum reaches 3.00×10 -3 At Pa, the sample was deposited at 120A for 4 seconds, and then removed after cooling.

[0050] Example 2

[0051] A method for preparing a CIGS thin film includes the following steps:

[0052] (1) Cleaning of the substrate

[0053] Sodium-calcium glass was selected as the substrate and cut into 2cm×2cm sizes. After wiping the surface stains with alcohol cotton balls, it was rinsed repeatedly with deionized water, ultrasonically cleaned with deionized water for 3 minutes, and then ultrasonically cleaned with anhydrous ethanol for 3 minutes (repeated twice). Finally, it was placed in an electric heating constant temperature drying oven to dry for later use.

[0054] (2) Sputtering Mo back electrode

[0055] The process employs DC magnetron sputtering with a base vacuum of 5×10⁻⁶. -4 Pa, sputtering power 100W, working gas pressure 1Pa, argon flow rate 30sccm, sputtering time 3min, to prepare a Mo back electrode with a thickness of about 450nm;

[0056] (3) Prepare CIG precursor solution (TU / M=2.0)

[0057] In a glove box at room temperature with a water oxygen content of <5ppm, add 0.761g of thiourea and 3ml of LDMF to sample vial 1, dissolve, and then add 0.495g of CuCl and stir until completely dissolved; add 0.761g of thiourea and 3ml of LDMF to sample vial 2, dissolve, and then add 1.300g of InCl3·4H2O and 0.20g of GaCl3 sequentially, stirring until the solution is clear each time; mix the two solutions and stir for 5h, age for more than 11h, and then filter through a 0.22μm filter membrane for later use;

[0058] (4) Spin coating to prepare CIG precursor films

[0059] Mo-coated sodium-calcium glass was fixed on the suction cup of a spin coater. After removing surface dust, the precursor solution was added, and the film was spin-coated by rotating at a low speed of 550 r / min for 40 s and then at a high speed of 1100 r / min for 55 s. The film was then dried by heating on a hot table at 180℃ for 30 s, and after cooling for 1 min-2 min, the spin-coating-drying process was repeated 5-6 times. Finally, the film was pre-annealed at 330℃ for 30 min to obtain the CIG precursor film.

[0060] (5) Selenization treatment

[0061] 45 mg of solid Se powder and CIG precursor film (face down) were placed in a graphite box with a spacing of about 1.5 cm. After the graphite box was placed in a quartz tube, it was evacuated and filled with argon gas three times. After the tube furnace was heated to the set temperature, the graphite box was pushed in for rapid heating and selenization. After selenization was completed, the graphite box was removed and allowed to cool naturally to room temperature, so that the precursor decomposed and generated chalcopyrite-structured CIGS.

[0062] A method for fabricating a highly stable self-driven CIGS photodetector includes the following steps:

[0063] ① Chemical bath deposition of CdS buffer layer: At 65℃, the film was immersed in a mixed solution containing 0.430 g thiourea, 0.030 g CdSO4, 9.3 mL ammonia and 50 mL deionized water, and deposited for 8 min; ② Magnetron sputtering preparation of i-ZnO and ITO layers: i-ZnO (base vacuum 6×10⁻⁶) -4 Pa, sputtering power 100W, argon-oxygen ratio 23:10, working pressure 2Pa, deposition 5 min), ITO (baseline vacuum 6×10 -4 Pa, sputtering power 100W, argon-oxygen ratio 40:0.5, working pressure 0.5 Pa, deposition 9 min); ③ Vacuum evaporation of Al top electrode: after masking, the base vacuum reaches 3.00×10 -3 At Pa, the sample was deposited at 120A for 4 seconds, and then removed after cooling.

[0064] Example 3

[0065] A method for preparing a CIGS thin film includes the following steps:

[0066] (1) Cleaning of the substrate

[0067] Sodium-calcium glass was selected as the substrate and cut into 2cm×2cm sizes. After wiping the surface stains with alcohol cotton balls, it was rinsed repeatedly with deionized water, ultrasonically cleaned with deionized water for 3 minutes, and then ultrasonically cleaned with anhydrous ethanol for 3 minutes (repeated twice). Finally, it was placed in an electric heating constant temperature drying oven to dry for later use.

[0068] (2) Sputtering Mo back electrode

[0069] The process employs DC magnetron sputtering with a base vacuum of 8×10⁻⁶. -5 Pa, sputtering power 130W, working pressure 2Pa, argon flow rate 20sccm, sputtering time 10min, to prepare a Mo back electrode with a thickness of about 350nm;

[0070] (3) Prepare CIG precursor solution (TU / M=2.5)

[0071] In a glove box at room temperature with a water oxygen content of <5ppm, add 0.952g of thiourea and 3ml of LDMF to sample vial 1, dissolve, then add 0.495g of CuCl and stir until completely dissolved; add 0.952g of thiourea and 3ml of LDMF to sample vial 2, dissolve, then add 1.300g of InCl3·4H2O and 0.20g of GaCl3 sequentially, stirring until the solution is clear each time; mix the two solutions and stir for 5h, age for more than 10h, then filter through a 0.22μm filter membrane for later use;

[0072] (4) Spin coating to prepare CIG precursor films

[0073] Mo-coated sodium-calcium glass was fixed on the suction cup of a spin coater. After removing surface dust, the precursor solution was added, and the film was spin-coated by rotating at a low speed of 500 r / min for 50 s and then at a high speed of 1250 r / min for 70 s. The film was then dried by heating on a hot table at 200℃ for 40 s, and after cooling for 1 min-2 min, the spin-coating-drying process was repeated 5-6 times. Finally, the film was pre-annealed at 330℃ for 35 min to obtain the CIG precursor film.

[0074] (5) Selenization treatment

[0075] 40 mg of solid Se powder and CIG precursor film (face down) were placed in a graphite box with a spacing of about 0.7 cm. After the graphite box was placed in a quartz tube, it was evacuated and filled with argon gas three times. After the tube furnace was heated to the set temperature, the graphite box was pushed in for rapid heating and selenization. After selenization was completed, the graphite box was removed and allowed to cool naturally to room temperature, so that the precursor decomposed and generated chalcopyrite-structured CIGS.

[0076] A method for fabricating a highly stable self-driven CIGS photodetector includes the following steps:

[0077] ① Chemical bath deposition of CdS buffer layer: At 65℃, the film was immersed in a mixed solution containing 0.430 g thiourea, 0.030 g CdSO4, 9.3 mL ammonia and 50 mL deionized water, and deposited for 8 min; ② Magnetron sputtering preparation of i-ZnO and ITO layers: i-ZnO (base vacuum 8×10- 4 Pa, sputtering power 90W, argon-oxygen ratio 23:15, working pressure 1.5Pa, deposition time 3min), ITO (baseline vacuum 5×10 -4Pa(Sputtering power 100W, argon-oxygen ratio 38:1.5, working pressure 1Pa, deposition 12min); ③ Vacuum evaporation of Al top electrode: After masking, the base vacuum reaches 3.00×10⁻⁶. -3 At Pa, the sample was deposited at 120A for 4 seconds, and then removed after cooling.

[0078] Example 4

[0079] A method for preparing a CIGS thin film includes the following steps:

[0080] (1) Cleaning of the substrate

[0081] Sodium-calcium glass was selected as the substrate and cut into 2cm×2cm sizes. After wiping the surface stains with alcohol cotton balls, it was rinsed repeatedly with deionized water, ultrasonically cleaned with deionized water for 3 minutes, and then ultrasonically cleaned with anhydrous ethanol for 3 minutes (repeated twice). Finally, it was placed in an electric heating constant temperature drying oven to dry for later use.

[0082] (2) Sputtering Mo back electrode

[0083] The process employs DC magnetron sputtering with a base vacuum of 2×10⁻⁶. -4 Pa, sputtering power 200W, working gas pressure 1.5Pa, argon flow rate 15sccm, sputtering time 7min, to prepare a Mo back electrode with a thickness of about 400nm;

[0084] (3) Prepare CIG precursor solution (TU / M=3.0)

[0085] In a glove box at room temperature with a water oxygen content of <5ppm, add 1.142g of thiourea and 3ml of LDMF to sample vial 1, dissolve, then add 0.495g of CuCl and stir until completely dissolved; add 1.142g of thiourea and 3ml of LDMF to sample vial 2, dissolve, then add 1.300g of InCl3・4H2O and 0.20g of GaCl3 sequentially, stirring until the solution is clear each time; mix the two solutions and stir for 5h, age for more than 10h, then filter through a 0.22μm filter membrane for later use;

[0086] (4) Spin coating to prepare CIG precursor films

[0087] Mo-coated sodium-calcium glass was fixed on the suction cup of a spin coater. After removing surface dust, a precursor solution was added, and the film was spin-coated by rotating at a low speed of 450 r / min for 30 s and then at a high speed of 1150 r / min for 70 s. The film was then dried by heating on a hot table at 160℃ for 25 s, and after cooling for 1 min-2 min, the spin-coating-drying process was repeated 5 to 6 times. Finally, a control group experiment was set up for the pre-annealing temperature. The pre-annealing temperatures were 270℃, 290℃, 310℃, 330℃, and 350℃, and the temperature was held for 30 min to obtain different CIG precursor films.

[0088] (5) Selenization treatment

[0089] 60 mg of solid Se powder and CIG precursor film (face down) were placed in a graphite box with a spacing of about 1.2 cm. After the graphite box was placed in a quartz tube, it was evacuated and filled with argon gas three times. After the tube furnace was heated to the set temperature, the graphite box was pushed in for rapid heating and selenization. After selenization was completed, the graphite box was removed and allowed to cool naturally to room temperature, so that the precursor decomposed and generated chalcopyrite-structured CIGS.

[0090] A method for fabricating a highly stable self-driven CIGS photodetector includes the following steps:

[0091] ① Chemical bath deposition of CdS buffer layer: At 65℃, the film was immersed in a mixed solution containing 0.430g thiourea, 0.030g CdSO4, 9.3mL ammonia and 50mL deionized water, and deposited for 8min; ② Magnetron sputtering preparation of i-ZnO and ITO layers: i-ZnO (base vacuum 7×10 -4 Pa, sputtering power 120W, argon-oxygen ratio 25:11, working pressure 2Pa, deposition 5 min), ITO (baseline vacuum 7×10 -4 Pa, sputtering power 90W, argon-oxygen ratio 35:1, working pressure 1Pa, deposition 9 min); ③ Vacuum evaporation of Al top electrode: after masking, the base vacuum reaches 3.00×10 -3 At Pa, the sample was deposited at 120A for 4 seconds, and then removed after cooling.

[0092] Figure 2 The XRD spectra of samples prepared at different pre-annealing temperatures in this embodiment are shown. Figure 3 These are SEM images of samples prepared at different pre-annealing temperatures in this embodiment. Figure 3 It can be seen that as the pre-annealing temperature increases from 270℃ to 330℃, the peak intensity of the (112) main peak gradually increases, while the full width at half maximum (FWHM) decreases, indicating that the grain size of the CIGS film gradually increases with the increase of the pre-annealing temperature. When the pre-annealing temperature continues to increase to 350℃, the peak intensity of the (112) diffraction peak decreases. This is because when the pre-annealing temperature is too high, CIGS grains are prone to agglomeration and accumulation during growth, affecting grain growth and reducing the grain size of the film. Figure 3As can be seen, the particle size of the sample gradually increases with increasing pre-annealing temperature. This is because a higher pre-annealing temperature leads to more thorough decomposition of impurities in the precursor film, which is beneficial for the growth of precursor film grains during high-temperature selenization. The figure shows that the particle size is largest at 330℃, approaching 1 μm, indicating that the CIGS film prepared at a pre-annealing temperature of 330℃ has optimal crystallinity. When the pre-annealing temperature continues to increase to 350℃, the CIGS particle size decreases, and agglomeration occurs between particles, increasing the porosity inside the film and making the film surface rougher.

[0093] Example 5

[0094] A method for preparing a CIGS thin film includes the following steps:

[0095] (1) Cleaning of the substrate

[0096] Sodium-calcium glass was selected as the substrate and cut into 2cm×2cm sizes. After wiping the surface stains with alcohol cotton balls, it was rinsed repeatedly with deionized water, ultrasonically cleaned with deionized water for 3 minutes, and then ultrasonically cleaned with anhydrous ethanol for 3 minutes (repeated twice). Finally, it was placed in an electric heating constant temperature drying oven to dry for later use.

[0097] (2) Sputtering Mo back electrode

[0098] The process employs DC magnetron sputtering with a base vacuum of 8×10⁻⁶. -5 Pa, sputtering power 200W, working pressure 1.4Pa, argon flow rate 30sccm, sputtering time 3min, to prepare a Mo back electrode with a thickness of about 300nm;

[0099] (3) Prepare CIG precursor solution (TU / M=3.5)

[0100] In a glove box at room temperature with a water oxygen content of <5ppm, 1.332g of thiourea and 3ml of LDMF were added to sample vial 1 and dissolved. Then, 0.600g of CuCl was added and stirred until completely dissolved. In sample vial 2, 1.332g of thiourea and 3ml of LDMF were added and dissolved. Then, 1.1211g of InCl3·4H2O and 0.20g of GaCl3 were added sequentially, stirring until the solution was clear each time. The two solutions were mixed and stirred for 5 hours, aged for more than 11 hours, and then filtered through a 0.22μm filter membrane for later use.

[0101] (4) Spin coating to prepare CIG precursor films

[0102] Mo-coated sodium-calcium glass was fixed on the suction cup of a spin coater. After removing surface dust, the precursor solution was added, and the film was spin-coated by rotating at a low speed of 500 r / min for 35 s and then at a high speed of 1200 r / min for 60 s. The film was then heated to 190℃ for 30 s and dried. After cooling for 1 min-2 min, the spin-coating-drying process was repeated 5-6 times. Finally, the film was pre-annealed at 330℃ for 40 min to obtain the CIG precursor film.

[0103] (5) Selenization treatment

[0104] 55 mg of solid Se powder and CIG precursor film (face down) were placed in a graphite box with a spacing of about 1.3 cm. After the graphite box was placed in a quartz tube, it was evacuated and filled with argon gas three times. After the tube furnace was heated to the set temperature, the graphite box was pushed in for rapid heating and selenization. After selenization was completed, the graphite box was removed and allowed to cool naturally to room temperature, so that the precursor decomposed and generated chalcopyrite-structured CIGS.

[0105] A method for fabricating a highly stable self-driven CIGS photodetector includes the following steps:

[0106] ① Chemical bath deposition of CdS buffer layer: At 65℃, the film was immersed in a mixed solution containing 0.430 g thiourea, 0.030 g CdSO4, 9.3 mL ammonia and 50 mL deionized water, and deposited for 8 min; ② Magnetron sputtering preparation of i-ZnO and ITO layers: i-ZnO (base vacuum 6×10⁻⁶) -4 Pa, sputtering power 90W, argon-oxygen ratio 20:12, working pressure 1.6Pa, deposition time 5min), ITO (baseline vacuum 7×10 -4 Pa, sputtering power 110W, argon-oxygen ratio 40:0.5, working pressure 0.5Pa, deposition time 9min); ③ Vacuum evaporation of Al top electrode: after masking, the base vacuum reaches 3.00×10 -3 At Pa, the sample was vapor-deposited at 120A for the set time, and then removed after cooling.

[0107] Figure 4 The XRD spectra are those of samples prepared with different amounts of thiourea in Examples 1-5 of this invention.

[0108] Figure 5 The images shown are SEM images of samples prepared with different amounts of thiourea in Examples 1-5 of the present invention. Figures (a)-(f) are SEM images of cross-sections of the samples prepared in Examples 1-5 of the present invention, respectively.

[0109] pass Figure 4 As can be seen, the peak intensity is strongest and the full width at half maximum (FWHM) is smallest when TU / M = 3.0, indicating that the CIGS film prepared under this condition has the best crystallinity. Figure 5As can be seen, the TU3.0 sample has the largest crystal grain size, the clearest grain boundary outline, and the best crystal quality.

[0110] Example 6

[0111] A method for preparing a CIGS thin film includes the following steps:

[0112] (1) Cleaning of the substrate

[0113] Sodium-calcium glass was selected as the substrate and cut into 2cm×2cm sizes. After wiping the surface stains with alcohol cotton balls, it was rinsed repeatedly with deionized water, ultrasonically cleaned with deionized water for 3 minutes, and then ultrasonically cleaned with anhydrous ethanol for 3 minutes (repeated twice). Finally, it was placed in an electric heating constant temperature drying oven to dry for later use.

[0114] (2) Sputtering Mo back electrode

[0115] The process employs DC magnetron sputtering with a base vacuum of 2×10⁻⁶. -4 Pa, sputtering power 200W, working gas pressure 1.5Pa, argon flow rate 15sccm, sputtering time 7min, to prepare a Mo back electrode with a thickness of about 400nm;

[0116] (3) Prepare CIG precursor solution (TU / M=3.0)

[0117] In a glove box at room temperature with a water oxygen content of <5ppm, add 1.142g of thiourea and 3ml of LDMF to sample vial 1, dissolve, then add 0.495g of CuCl and stir until completely dissolved; add 1.142g of thiourea and 3ml of LDMF to sample vial 2, dissolve, then add 1.300g of InCl3・4H2O and 0.20g of GaCl3 sequentially, stirring until the solution is clear each time; mix the two solutions and stir for 5h, age for more than 10h, then filter through a 0.22μm filter membrane for later use;

[0118] (4) Spin coating to prepare CIG precursor films

[0119] Mo-coated sodium-calcium glass was fixed on the suction cup of a spin coater. After removing surface dust, the precursor solution was added, and the film was spin-coated by rotating at a low speed of 450 r / min for 30 s and then at a high speed of 1150 r / min for 70 s. The film was then dried by heating on a hot table at 160℃ for 25 s, and after cooling for 1 min-2 min, the spin-coating-drying process was repeated 5-6 times. Finally, the film was pre-annealed at 330℃ for 40 min to obtain the CIG precursor film.

[0120] (5) Layered selenization treatment

[0121] 60 mg of solid Se powder and a CIG precursor film (face down) were placed in a graphite box with a spacing of about 1.2 cm. After the graphite box was placed in a quartz tube, it was evacuated and filled with argon gas three times. After spin-coating 2-3 layers and pre-annealing, the lower precursor film was obtained. Then, it was selenized for 20 min to obtain the lower CIGS film. A precursor film was spin-coated and annealed on the lower CIGS film, and then placed in a tube furnace for selenization for 30 min to achieve the layered selenization of the CIGS film.

[0122] A method for fabricating a highly stable self-driven CIGS photodetector includes the following steps:

[0123] ① Chemical bath deposition of CdS buffer layer: At 65℃, the film was immersed in a mixed solution containing 0.430g thiourea, 0.030g CdSO4, 9.3mL ammonia and 50mL deionized water, and deposited for 8min; ② Magnetron sputtering preparation of i-ZnO and ITO layers: i-ZnO (base vacuum 7×10 -4 Pa, sputtering power 120W, argon-oxygen ratio 25:11, working pressure 2Pa, deposition 5min), ITO (baseline vacuum 7×10 -4 Pa, sputtering power 90W, argon-oxygen ratio 35:1, working pressure 1Pa, deposition 9min); ③ Vacuum evaporation of Al top electrode: after masking, the base vacuum reaches 3.00×10 -3 At Pa, the sample was deposited at 120A for 4 seconds, and then removed after cooling.

[0124] Figure 6 The XRD spectra of samples prepared by different selenization processes in Example 6 of this invention; Figure 6 The XRD spectra of samples prepared by single selenization (N) and layered selenization (Se) are shown in the figure. As shown in the figure, the characteristic peaks of N and Se samples at 26.8°, 44.5°, and 52.7° correspond to the (112), (204 / 220), and (116 / 312) crystal orientations of the CIGS chalcopyrite structure, respectively. The peak positions are not significantly shifted and there are no other impurity peaks, indicating that a pure CIGS chalcopyrite phase has been successfully prepared.

[0125] Figure 7 These are SEM images of samples prepared under different selenization processes in Example 6 of the present invention.

[0126] As can be seen from the figure, compared to a single selenization ( Figure 7 (a) and layered selenization ( Figure 7 (b) Surface morphology photographs of the samples show that the layered selenization film particles are larger, approximately 2 μm in size; and the interparticle connectivity of the layered selenization film is better, with fewer interparticle pores, resulting in enhanced film density. This indicates that layered selenization significantly improves the crystallinity of the CIGS film; Figure 7(c) is a cross-sectional photograph of the layered selenized sample. It can be seen that the film is relatively dense with few internal pores, and the thickness of the film is about 2 μm.

[0127] Example 7

[0128] A method for preparing a CIGS thin film includes the following steps:

[0129] (1) Cleaning of the substrate

[0130] Sodium-calcium glass was selected as the substrate and cut into 2cm×2cm sizes. After wiping the surface stains with alcohol cotton balls, it was rinsed repeatedly with deionized water, ultrasonically cleaned with deionized water for 3 minutes, and then ultrasonically cleaned with anhydrous ethanol for 3 minutes (repeated twice). Finally, it was placed in an electric heating constant temperature drying oven to dry for later use.

[0131] (2) Sputtering Mo back electrode

[0132] The process employs DC magnetron sputtering with a base vacuum of 2×10⁻⁶. -4 Pa, sputtering power 200W, working gas pressure 1.5Pa, argon flow rate 15sccm, sputtering time 7min, to prepare a Mo back electrode with a thickness of about 400nm;

[0133] (3) Preparation of CIG precursor solution

[0134] In a glove box at room temperature with a water oxygen content of <5ppm, add 1.150g of thiourea and 3ml of LDMF to sample vial 1, dissolve, then add 0.495g of CuCl and stir until completely dissolved; add 1.150g of thiourea and 3ml of LDMF to sample vial 2, dissolve, then add 1.300g of InCl3・4H2O and 0.20g of GaCl3 sequentially, stirring until the solution is clear each time; mix the two solutions and stir for 5h, age for more than 10h, then filter through a 0.22μm filter membrane for later use;

[0135] (4) Spin-coating to prepare CIG precursor films with Cu gradient

[0136] Mo-plated sodium-calcium glass was fixed on the suction cup of a spin coater. After removing surface dust, a precursor solution was added, and spin-coated to obtain a lower copper-poor precursor film. Then, it was selenized at 540℃ for 20 min. Then, the middle copper-rich layer and the upper copper-poor layer were spin-coated, and selenized at 540℃ for 30 min to obtain a CIGS thin film. Finally, it was pre-annealed at 330℃ to obtain a precursor film with a Cu gradient.

[0137] (5) Selenization treatment

[0138] 60 mg of solid Se powder and CIG precursor film (face down) were placed in a graphite box with a spacing of about 1.2 cm. After the graphite box was placed in a quartz tube, it was evacuated and filled with argon gas three times. After the tube furnace was heated to the set temperature, the graphite box was pushed in for rapid heating and selenization. After selenization was completed, the graphite box was removed and allowed to cool naturally to room temperature, so that the precursor decomposed and generated chalcopyrite-structured CIGS.

[0139] A method for fabricating a highly stable self-driven CIGS photodetector includes the following steps:

[0140] ① Chemical bath deposition of CdS buffer layer: At 65℃, the film was immersed in a mixed solution containing 0.430 g thiourea, 0.030 g CdSO4, 9.3 mL ammonia and 50 mL deionized water, and deposited for 8 min; ② Magnetron sputtering preparation of i-ZnO and ITO layers: i-ZnO (base vacuum 7×10⁻⁶) -4 Pa, sputtering power 120W, argon-oxygen ratio 25:11, working pressure 2Pa, deposition 5 min), ITO (baseline vacuum 7×10 -4 Pa, sputtering power 90W, argon-oxygen ratio 35:1, working pressure 1Pa, deposition 9 min); ③ Vacuum evaporation of Al top electrode: after masking, the base vacuum reaches 3.00×10 -3 At Pa, the sample was deposited at 120A for 4 seconds, and then removed after cooling.

[0141] Figure 8 The XRD spectra of different Cu gradients in this embodiment are shown. As can be seen from the spectra, all samples show obvious diffraction peaks at 27.1°, 45.1°, and 53.5°, which are consistent with the three strong peaks (112), (204 / 220), and (116 / 312) of chalcopyrite CIGS (JCP-DS card number: 35-1102). There are no other obvious impurity peaks, and the peak positions are not shifted, indicating that CIGS grains with a single chalcopyrite phase were obtained. The three strong peaks (112), (204 / 220), and (116 / 312) of the Cu1 sample with Cu gradient are stronger than those of the N sample without Cu gradient, indicating that the construction of Cu gradient does significantly increase the grain size of CIGS and improve the crystal quality.

[0142] Figure 9The Raman spectra of different Cu gradients in this embodiment are shown. The Cu1 sample exhibits a characteristic peak corresponding to the CuxSe phase at 262 cm⁻¹, indicating that the introduction of the copper-rich layer caused the formation of the CuxSe phase in the film, with a small amount remaining after high-temperature selenization. In contrast, the characteristic peak of the CuxSe phase disappears in the Cu2 sample, suggesting that the selenization process resulted in a more complete reaction between Se and Cu, In, and Ga, and a more uniform elemental diffusion in the CIGS film. The full width at half maximum (FWHM) of the Cu1 sample is smaller than that of N, while the FWHM of the Cu2 sample is smaller than that of Cu1. This demonstrates that the introduction of the copper-rich layer can optimize the structure of the CIGS film, and further introduction of layered selenization can further improve the crystallinity of the CIGS film.

[0143] Figure 10 These are SEM images of different Cu gradients in this embodiment, where (a) and (d) are SEM images of the N sample; (b) and (e) are SEM images of the Cu1 sample; and (c) and (f) are SEM images of the Cu2 sample.

[0144] Figure 11 The figure shows the EDS line scan element concentration variation curves along the optimal Cu gradient cross-section in this embodiment. As shown, the four elements Cu, In, Ga, and Se contained in the film are uniformly distributed along the thickness direction, indicating that the Cu gradient constructed in the precursor film has disappeared after selenization due to element diffusion.

[0145] Figure 12 This diagram illustrates the variations in resistivity, carrier mobility, and carrier concentration at different Cu gradients in this embodiment. The resistivity of the N, Cu1, and Cu2 samples is 0.9348 × 10⁻⁶. -2 Ω·cm, 2.2038×10 -2 Ω·cm, 1.2472×10 -2 Ω·cm, all within 10 -2 The resistivity of the Cu1 sample initially increased and then decreased. The higher resistivity was due to the introduction of a copper-rich layer in the film; after selenization, a small amount of CuxSe phase remained, leading to the increased resistivity. In contrast, the resistivity of the Cu2 sample decreased significantly compared to Cu1. This is because the Cu2 sample underwent layered selenization, which improved the crystallization of the CIGS phase and the elemental distribution within the film, preventing CuxSe phase residue in the CIGS film. The carrier concentrations of N, Cu1, and Cu2 samples were 1.4007 × 10⁻⁶. 17 cm -3 3.2062×10 16 cm -3 3.7379×10 16 cm -3 All are at their best 10 16 ~10 17scope.

[0146] Figure 13 This is the It response curve for the optimal Cu gradient within 20000 s in this embodiment. From... Figure 13 It can be seen that the Idark value of the Cu₂T photodetector with the optimal Cu gradient remains approximately 0 during the 20,000 s test period. The Ilight value of the detector fluctuates within a very small range, calculated to be approximately 5%.

[0147] Figure 14 In this embodiment, the optimal Cu gradient is the photocurrent (I) within 20000s. light ) and dark current (I dark ) Change curve.

[0148] from Figure 14 It can be seen that the Ilight of the Cu2T detector was 3.773mA at the beginning of the test and 3.717mA at the end of the test. The attenuation of the photocurrent did not exceed 1.5%, indicating that the detector has excellent signal stability.

Claims

1. A method for preparing a CIGS thin film, characterized in that, Includes the following steps: First, soda-lime glass is selected as the substrate, cut, cleaned and dried; then, a Mo back electrode is sputtered onto the treated substrate to obtain Mo-plated soda-lime glass, a precursor solution is spin-coated and heated and dried to prepare a CIG precursor, and finally the CIG precursor film is subjected to high-temperature selenization treatment to obtain a CIGS thin film.

2. The method for preparing a CIGS thin film according to claim 1, characterized in that, The soda-lime glass is cut to a size of 2cm×2cm; the cleaning process involves wiping the surface of the soda-lime glass with an alcohol swab, followed by ultrasonic cleaning with deionized water and anhydrous ethanol for 3 minutes each, with the ethanol cleaning being repeated twice; after cleaning, the substrate is placed in an electric heating constant temperature drying oven for drying and later use.

3. The method for preparing a CIGS thin film according to claim 1, characterized in that, The sputtering process parameters are: base vacuum 8×10 -4 Pa-8×10 -5 Pa, sputtering power 100W-200W, working gas pressure 1Pa-2Pa, argon flow rate 10sccm-30sccm, sputtering time 3min-10min, forming a Mo back electrode with a thickness of 300nm-450nm.

4. The method for preparing a CIGS thin film according to claim 1, characterized in that, The preparation steps of the precursor solution are as follows: In a glove box, first, 0.500g-1.500g of thiourea is mixed and dissolved with 1mL-10mL of DMF, then 0.200g-1.00g of CuCl is added and stirred until completely dissolved to obtain solution A; then, 0.500g-1.500g of thiourea is mixed and dissolved with 1mL-10mL of DMF, then 1.000g-1.500g of InCl3·4H2O and 0.10g-0.50g of GaCl3 are added and stirred until clear to obtain solution B; solutions A and B are mixed and stirred for 4-6 hours, aged for 10-12 hours, and then filtered through a 0.22μm filter membrane for later use. The water oxygen content in the glove box is <5ppm, and the environment is at room temperature.

5. The method for preparing a CIGS thin film according to claim 1, characterized in that, The spin coating process involves fixing the Mo-coated soda-lime glass onto a spin coater, rotating it at a low speed of 450 r / min-550 r / min for 30-50 seconds, then rotating it at a high speed of 1100 r / min-1250 r / min for 55-70 seconds, and adding a precursor solution to form a wet film. The heating and drying process involves heating the spin-coated glass at 150℃-200℃ for 20-40 seconds and drying it. The spin coating-drying process is repeated 5-6 times, and finally, the glass is pre-annealed at 270℃-350℃ for 25-40 minutes.

6. The method for preparing a CIGS thin film according to claim 1, characterized in that, The high-temperature selenization process is as follows: using solid Se powder as the Se source, 40mg-60mg of Se powder and the CIG precursor membrane are placed face-to-face in a graphite box with a spacing of about 0.7cm-1.5cm, and a quartz tube is placed in it. Then, the process of introducing argon gas, evacuating the vacuum, and introducing argon gas again is repeated 4-6 times, and the air in the tube is then purged. After setting the argon gas flow rate to 5sccm-10sccm, the tube furnace is started to heat up to 540℃-570℃. The graphite box is then pushed into the furnace for selenization, and after the process is completed, it is removed and allowed to cool naturally to room temperature.

7. A CIGS thin film, characterized in that... Prepared using any one of the methods described in claims 1-6.

8. An application of a CIGS thin film, characterized in that, It is used in highly stable self-driven photodetectors.

9. The application of a CIGS thin film according to claim 8, characterized in that, The fabrication method of the highly stable self-driven CIGS photodetector is as follows: First, a CdS buffer layer is deposited by chemical bath deposition. Specifically, 0.400g-0.430g of thiourea is weighed and dissolved in 6mL-7mL of deionized water, stirred and preheated to 60℃-70℃ for later use. 0.025g-0.030g of CdSO4 is weighed and dissolved in 6mL-7mL of deionized water. This CdSO4 solution is then mixed with 9mL-10mL of ammonia water in a beaker containing 50mL of deionized water. The beaker is placed in a water bath preheated to 65℃ and stirred. Then, the preheated thiourea solution is poured in and stirred slowly to obtain a mixed solution. The CIGS thin film sample is immersed in the mixed solution and deposited in a water bath for 7min-10min, then removed to obtain the deposited CIGS thin film. Next, i-ZnO and ITO layers are prepared on the deposited CIGS thin film using magnetron sputtering. The sputtering parameters for i-ZnO are a base vacuum of 5×10⁻⁶. -4 Pa-8×10 -4 Pa, sputtering power 90W-120W, argon-oxygen ratio (20-25):(10-15), working pressure 1Pa-2Pa, deposition 3min-5min; ITO sputtering parameters are local vacuum 5×10 -4 Pa-8×10 -4 Pa, sputtering power 90W-120W, argon-oxygen ratio (35-40):(0.5-1.5), working pressure 0.3Pa-1Pa, deposition time 7min-12min; finally, Al top electrode was prepared by vacuum evaporation. Before evaporation, a mask was used to cover the sample surface, exposing only the electrode position. When the local vacuum reached 3.00×10 -3 Turn on the power supply of the vapor deposition instrument at Pa, quickly adjust the vapor deposition current to 120A, hold for 3s~5s, and then quickly adjust the reading to 0. After the vapor deposition is completed, turn off the vapor deposition power supply and the molecular pump. After the instrument stabilizes, take out the sample to obtain a highly stable self-driven photodetector.

Images