Preparation method of semiconductor thin film solar cell

Abstract

The invention relates to the technical field of solar cells, and discloses a method for preparing a semiconductor thin film solar cell, which comprises the following steps of: S1, cleaning a substrate: carrying out ultrasonic cleaning on the substrate by using deionized water, alcohol and alkali liquor in sequence; s2, positive electrode deposition: depositing a molybdenum film on the substrate through a magnetron sputtering method; s3, preparing a precursor film: preparing the precursor film by using a sol-gel method; s4, selenylation annealing: putting the precursor film, selenium particles and tin disulfide into a graphite box; s5, buffer layer deposition: depositing a cadmium sulfide buffer layer on the absorption layer through a chemical bath method; s6, depositing a window layer; s7, depositing a negative electrode; and S8, packaging. The tin disulfide atmosphere is introduced in the annealing process, element distribution and crystal quality of the copper-zinc-tin-sulfide thin film are further optimized, composition segregation is effectively inhibited, and the composite defect density in the material is reduced. And the absorption layer has more excellent crystallization characteristics, so that the photoelectric conversion efficiency is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and particularly to a preparation method of a semiconductor thin film solar cell. Background Art

[0002] As an important direction of the next-generation photovoltaic technology, semiconductor thin film solar cells have received wide attention due to their high material utilization rate, low process cost, and great potential for flexible applications. Among them, solar cells based on copper-zinc-tin-sulfide (CZTS) and copper-zinc-tin-sulfur-selenium (CZTSSe) absorption layers are considered to be one of the most promising photovoltaic devices because of their abundant raw materials, non-toxic and environmentally friendly properties.

[0003] In the prior art, common methods for preparing CZTS or CZTSSe thin films include solution method, chemical bath method, sputtering method, etc. Subsequently, the crystallization and composition regulation of the materials are completed through a high-temperature sulfidation or selenization annealing process. However, due to the significant difference in the vapor pressures of elements in the CZTSSe system, sulfur and selenium elements are prone to volatilization loss during the high-temperature annealing process, resulting in film composition segregation and an increase in defect density, seriously affecting the photoelectric performance stability of the device. At the same time, in the traditional annealing process, only a single selenium source atmosphere is usually relied on, lacking fine regulation of the auxiliary components in the annealing atmosphere, making it difficult to effectively compensate for element loss and promote crystal structure optimization, restricting the further improvement of film quality and the final device efficiency.

[0004] In addition, in the existing preparation methods, the control of the deposition temperature mostly relies on traditional heating equipment, which has problems such as uneven temperature field distribution and inaccurate real-time control, easily leading to large fluctuations in the crystallization quality of the film layer, an increase in surface roughness, and limited light absorption performance and carrier transport characteristics of the thin film. Especially in wet deposition processes such as the chemical bath method, due to the complex reaction kinetics, a small change in temperature may significantly affect the denseness and uniformity of the thin film. If the temperature control means are insufficient, holes, pinholes, and large defects are likely to appear in the film layer, thereby deteriorating the device performance. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the present invention provides a preparation method of a semiconductor thin film solar cell, which solves the problems of low photoelectric performance, poor crystallinity, and high surface roughness of the thin film in the prior art.

[0006] To achieve the above object, the present invention is realized through the following technical solutions: A preparation method of a semiconductor thin film solar cell, comprising the following steps: S1. Substrate cleaning: The substrate is ultrasonically cleaned in sequence with deionized water, alcohol, and alkali solution for 5 - 10 minutes, and then dried with nitrogen after cleaning; S2. Positive electrode deposition: Depositing a molybdenum thin film on the substrate by magnetron sputtering; S3. Preparation of the precursor film: The precursor film is prepared by the sol-gel method, and the thickness of the precursor film is controlled between 200 and 3000 nm. The precursor solution is uniformly coated on the molybdenum electrode by the spin coating method; S4. Selenization annealing: The precursor film, selenium grains, and tin disulfide are placed together in a graphite box and annealed in a compound atmosphere composed of group IV-VI elements; S5. Deposition of the buffer layer: A cadmium sulfide buffer layer is deposited on the absorption layer by the chemical bath method; S6. Deposition of the window layer: An intrinsic zinc oxide layer and an indium tin oxide layer are deposited on the buffer layer by radio frequency magnetron sputtering; S7. Deposition of the negative electrode: A nickel-aluminum grid electrode is prepared on the window layer by vacuum evaporation; S8. Encapsulation: The thin film solar cell is appropriately encapsulated.

[0007] Preferably, the substrate is soda-lime glass or quartz glass with a thickness of 0.1-2 mm.

[0008] Preferably, the magnetron sputtering method in step 2 specifically includes the following steps; On the surface of the cleaned and dried substrate, first-stage molybdenum sputtering deposition is carried out, with a sputtering power of 130-170 W, a sputtering time of 1.0-2.0 minutes, and a sputtering pressure of 0.3-0.6 Pa; Immediately followed by second-stage molybdenum sputtering deposition, with a sputtering power of 30-70 W, a sputtering time of 0.3-0.7 minutes, and a sputtering pressure of 0.05-0.15 Pa; The target used in the two-stage sputtering process is a molybdenum target with a purity of not less than 99.9%, and the total thickness of the molybdenum film is controlled between 500 and 5000 nm.

[0009] Preferably, step 3 specifically includes the following steps; Prepare the precursor solution, and sequentially add the copper source, zinc source, tin source, and sulfur source to the solvent for dissolution. The solvent is deionized water or a mixed solvent of ethanol and deionized water with a volume ratio of 1:1-1:3 The solution is stirred at room temperature for 30-90 minutes until a clear and transparent solution is formed; The precursor solution is coated on the surface of the molybdenum positive electrode by the spin coating method, with a spin coating rate of 1000-3000 rpm and a spin coating time of 30-60 seconds; After spin coating, it is heated at 100-200 °C for 5-15 minutes for pre-drying to remove the solvent; Through repeated alternation of spin coating and pre-drying, until the thickness of the precursor film reaches 200-3000 nm.

[0010] Preferably, the concentration of copper nitrate as the copper source is 0.05 - 0.2 mol / L, the concentration of zinc nitrate as the zinc source is 0.02 - 0.1 mol / L, the concentration of tin nitrate as the tin source is 0.02 - 0.1 mol / L, and the concentration of thiourea as the sulfur source is 0.5 - 2 mol / L.

[0011] Preferably, the specific steps in step S4 are as follows; Put the precursor film, selenium particles and 1 - 5 mg of tin disulfide into a graphite box together; Put the graphite box into a tube furnace, set the temperature of the tube furnace to 450 - 600 °C, and the annealing time to 10 - 30 minutes; During the annealing process, the furnace atmosphere is a compound atmosphere composed of group IV - VI elements. The group IV - VI element compounds include but are not limited to tin sulfide, tin disulfide, and tin selenide. The gas flow rate is controlled at 50 - 150 sccm; The reaction gas during the annealing process participates in the reaction to form an absorption layer, and the thickness of this absorption layer is 500 - 3000 nm; After the annealing is completed, quickly take out the sample and let it cool naturally at room temperature. The cooling time is 10 - 30 minutes.

[0012] Preferably, the specific steps in step S5 are as follows; Deposit the cadmium sulfide buffer layer by chemical bath deposition: Place the absorption layer in the cadmium sulfide solution; The solvent is deionized water to ensure the uniformity of the solution and the stability of the reaction; By controlling the temperature of the solution, keep it at 60 - 90 °C, and carry out chemical bath reaction at this temperature to deposit the cadmium sulfide buffer layer. The deposition time is controlled to be 10 - 30 minutes; Control the thickness of the deposited CdS layer to be between 30 - 200 nm; After the deposition is completed, take out the sample and wash it with deionized water to remove the chemical substances remaining on the surface, and finally dry it naturally at room temperature.

[0013] Preferably, the cadmium sulfide solution contains: Hydrogen sulfide solution with a concentration of 0.1 - 1 mol / L; Cadmium nitrate solution with a concentration of 0.05 - 0.2 mol / L.

[0014] Preferably, the specific steps in step S6 are as follows; Deposit an intrinsic zinc oxide layer on the surface of the buffer layer by radio frequency magnetron sputtering. The thickness of the zinc oxide layer is 40 - 80 nm, the sputtering power is 80 - 120 W, the sputtering atmosphere is a mixed gas of argon and oxygen, the sputtering pressure is 0.8 - 1.2 Pa, and the sputtering time is 10 - 20 minutes; Continuously deposit an indium tin oxide layer on the zinc oxide layer by radio frequency magnetron sputtering. The thickness of the indium tin oxide layer is 80 - 120 nm, the sputtering power of the indium tin oxide layer is 130 - 180 W, the sputtering atmosphere is pure argon, the gas flow rate is 15 - 25 sccm, the sputtering pressure is 0.8 - 1.2 Pa, and the sputtering time is 15 - 25 minutes; After the window layer deposition is completed, perform heat treatment at 150 - 200 °C, and the heat treatment time is 10 - 30 minutes.

[0015] Preferably, the step S7 specifically includes the following steps; Deposit a nickel-aluminum double-layer metal gate electrode on the surface of the window layer by vacuum evaporation. The total thickness of the nickel-aluminum electrode is 950 - 1050 nm First deposit a nickel layer. The thickness of the nickel layer is 45 - 55 nm. Use a high-purity metal nickel evaporation source, control the evaporation temperature at 1200 - 1300 °C, the evaporation rate is 0.05 - 0.10 nm / s, keep the pressure in the vacuum chamber at 1×10 -3 Pa or less, and the evaporation time is 8 - 15 minutes; Deposit an aluminum layer on the nickel layer. The thickness of the aluminum layer is 900 - 1000 nm. Use a high-purity metal aluminum evaporation source, control the evaporation temperature at 1100 - 1250 °C, the evaporation rate is 0.2 - 0.5 nm / s, keep the pressure in the vacuum chamber at 1×10 -3 Pa or less, and the evaporation time is 20 - 60 minutes.

[0016] The present invention provides a method for preparing a semiconductor thin film solar cell. It has the following beneficial effects: 1. By introducing a tin disulfide atmosphere during the annealing process, the present invention further optimizes the element distribution and crystal quality of the copper-zinc-tin-sulfide thin film, effectively inhibits the composition segregation caused by sulfur and selenium volatilization, and reduces the composite defect density in the material. The absorption layer prepared by this method has more excellent crystallization characteristics and more uniform chemical composition, resulting in a significant improvement in the photoelectric conversion efficiency.

[0017] 2. By precisely controlling the deposition temperature in the deposition process, the present invention effectively improves the crystallinity and surface uniformity of the thin film. The precise control of temperature can optimize the light absorption characteristics of the thin film, reduce unnecessary defects, and thus improve the stability of the photoelectric performance. This technology breaks through the limitation of inaccurate temperature control in traditional thin film preparation and provides a guarantee for the high efficiency and stability of thin film materials.

[0018] 3. By combining the chemical bath method with precise temperature control, the present invention provides an efficient and controllable thin film preparation method. This method can achieve uniform thin film deposition under different deposition temperature conditions and effectively avoid problems such as excessive film roughness or defects that may occur in other preparation methods.

[0019] 4. By precisely controlling the deposition temperature, the present invention optimizes the crystallization quality of copper-zinc-tin-sulfide thin films, enabling them to maintain high performance under different environmental conditions. This high crystallinity not only enhances the photoelectric conversion efficiency of the material but also improves the adaptability of the thin film in different climates and usage environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a flowchart of the method of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0022] Please refer to the attached Figure 1 ; Example 1; Take a soda-lime glass with a thickness of 1.0 mm as the substrate, and ultrasonically clean it successively with deionized water, absolute ethanol, and 0.5 mol / L sodium hydroxide solution. The cleaning time for each solution is 7 minutes, and after cleaning, it is dried with nitrogen.

[0023] On the surface of the cleaned and dried substrate, molybdenum thin film is deposited by magnetron sputtering. The sputtering power in the first stage is set to 150 W, the sputtering time is 1.5 minutes, and the sputtering pressure is 0.45 Pa; immediately afterwards, the sputtering power in the second stage is reduced to 50 W, the sputtering time is 0.5 minutes, and the sputtering pressure is 0.1 Pa. Sputtering is carried out using a molybdenum target with a purity of 99.99%, and the total thickness of the molybdenum film is controlled at 2750 nm.

[0024] Subsequently, a precursor solution was prepared. Copper nitrate (concentration: 0.125 mol / L), zinc nitrate (0.06 mol / L), tin nitrate (0.06 mol / L), and thiourea (1.25 mol / L) were successively added to a mixed solvent of ethanol-deionized water with a volume ratio of 1:2, and stirred at room temperature for 60 minutes until the solution became clear and transparent. The precursor solution was spin-coated on the surface of the molybdenum positive electrode, with the spin-coating rate set at 2000 rpm and the spin-coating time of 40 seconds. After spin-coating, it was heated at 150 °C for 10 minutes for pre-drying. Spin-coating and drying were alternately carried out multiple times until the final thickness of the precursor film reached 1600 nm.

[0025] The precursor film, an appropriate amount of selenium grains, and 3 mg of tin disulfide were placed together in a graphite box and then put into a tube furnace. The temperature was set at 525 °C, a mixed atmosphere of tin sulfide / selenium tin sulfide was introduced, the gas flow rate was 100 sccm, the annealing time was set at 20 minutes, and after completion, it was naturally cooled for 30 minutes to obtain an absorption layer with a thickness of about 1750 nm.

[0026] On the surface of the absorption layer, a cadmium sulfide buffer layer was deposited by chemical bath deposition. The cadmium sulfide solution was prepared from a hydrogen sulfide solution with a concentration of 0.5 mol / L and a cadmium nitrate solution with a concentration of 0.125 mol / L. The reaction temperature was maintained at 75 °C and the deposition time was 20 minutes. After deposition, it was washed with deionized water and naturally dried, and the thickness of the buffer layer was 115 nm.

[0027] Next, a window layer was deposited on the buffer layer by radio frequency magnetron sputtering. First, the zinc oxide layer was sputtered with a sputtering power of 100 W, an atmosphere of a mixture of argon (20 sccm) and oxygen (5 sccm), a gas pressure of 1.0 Pa, and a deposition time of 15 minutes to obtain an i:ZnO layer with a thickness of about 60 nm; then the indium tin oxide layer was sputtered with a sputtering power of 155 W, an argon flow rate of 20 sccm, a gas pressure of 1.0 Pa, and a deposition time of 20 minutes to obtain an ITO layer with a thickness of about 100 nm. After completion, heat treatment was carried out at 170 °C for 20 minutes to optimize the window layer structure.

[0028] Finally, the negative electrode was deposited by vacuum evaporation. First, the nickel layer was evaporated with a thickness of 50 nm, an evaporation temperature of 1250 °C, an evaporation rate of 0.08 nm / s, the pressure in the vacuum chamber was lower than 1×10⁻³ Pa, and the evaporation time was about 12 minutes; then the aluminum layer was evaporated with a thickness of 950 nm, an evaporation temperature of 1175 °C, an evaporation rate of 0.35 nm / s, and an evaporation time of about 40 minutes. Finally, the preparation of the negative electrode of the device was completed and it was encapsulated.

[0029] Example 2; Select soda-lime glass with a thickness of 0.1 mm as the substrate. According to the same steps above, ultrasonically clean it with deionized water, absolute ethanol, and 0.5 mol / L sodium hydroxide solution respectively for 5 minutes each, and then dry it with nitrogen.

[0030] In the positive electrode deposition stage, the sputtering power in the first stage is 130 W, the sputtering time is 1.0 minute, and the sputtering pressure is 0.3 Pa; in the second stage, the sputtering power is 30 W, the sputtering time is 0.3 minute, and the sputtering pressure is 0.05 Pa. Use a 99.99% molybdenum target, and control the total film thickness at 500 nm.

[0031] In the preparation of the precursor solution, the concentration of copper nitrate is set at 0.05 mol / L, the concentration of zinc nitrate is 0.02 mol / L, the concentration of tin nitrate is 0.02 mol / L, the concentration of thiourea is 0.5 mol / L, and the solvent uses an ethanol-deionized water mixed solvent with a volume ratio of 1:3. After stirring the solution at room temperature for 30 minutes, the spin coating rate is 1000 rpm and the spin coating time is 30 seconds. After spin coating, dry it at 100 °C for 5 minutes. After multiple alternating spin coatings, the final thickness of the precursor film is 200 nm.

[0032] During the selenization annealing process, place the precursor film together with selenium grains and 1 mg of tin disulfide into a graphite box, selenize it at 450 °C for 10 minutes, with a gas flow rate of 50 sccm, to form an absorption layer with a thickness of about 500 nm.

[0033] Deposit a cadmium sulfide buffer layer on the surface of the absorption layer. The solution is prepared with 0.1 mol / L hydrogen sulfide solution and 0.05 mol / L cadmium nitrate solution, set the reaction temperature at 60 °C, and deposit for 10 minutes. After cleaning, dry it naturally, and the thickness of the buffer layer is about 30 nm.

[0034] During the deposition of the window layer, the sputtering power of the zinc oxide layer is 80 W, the argon / oxygen flow rates are 15 sccm / 3 sccm respectively, the air pressure is 0.8 Pa, the deposition time is 10 minutes, and the thickness of the zinc oxide layer is about 40 nm. Subsequently, sputter the ITO layer, with a power of 130 W, an argon flow rate of 15 sccm, an air pressure of 0.8 Pa, deposit for 15 minutes, and the thickness is about 80 nm. After completion, heat-treat it at 150 °C for 10 minutes.

[0035] In the negative electrode evaporation stage, the thickness of the nickel layer is 45 nm, the evaporation temperature is 1200 °C, and the evaporation rate is 0.05 nm / s; the thickness of the aluminum layer is 900 nm, the evaporation temperature is 1100 °C, and the evaporation rate is 0.2 nm / s; both steps control the vacuum degree below 1×10 -3 Pa.

[0036] Example 3; Select quartz glass with a thickness of 2 mm as the substrate, ultrasonically clean it with deionized water, absolute ethanol, and 0.5 mol / L sodium hydroxide solution for 10 minutes each, and dry it with nitrogen.

[0037] During the positive electrode deposition, the sputtering power in the first stage is 170 W, the time is 2.0 minutes, and the pressure is 0.6 Pa; in the second stage, the sputtering power is 70 W, the time is 0.7 minutes, and the pressure is 0.15 Pa. The total film thickness is 5000 nm.

[0038] When preparing the precursor solution, the concentration of copper nitrate is 0.2 mol / L, zinc nitrate is 0.1 mol / L, tin nitrate is 0.1 mol / L, and thiourea is 2 mol / L. The solvent is a mixed solution of ethanol - deionized water with a volume ratio of 1:1. After stirring for 90 minutes, the spin - coating rate is 3000 rpm and the spin - coating time is 60 seconds. After spin - coating, it is pre - dried at 200 °C for 15 minutes, and spin - coating is performed multiple times to form a 3000 - nm precursor film.

[0039] During the selenization annealing, the precursor film, 5 mg of tin disulfide, and selenium particles are placed together in a graphite box and selenized at 600 °C for 30 minutes with a gas flow rate of 150 sccm, finally forming a 3000 - nm - thick absorption layer.

[0040] During the buffer layer deposition, the concentration of hydrogen sulfide in the solution is 1 mol / L, the concentration of cadmium nitrate is 0.2 mol / L, the reaction temperature is 90 °C, and the deposition time is 30 minutes. After cleaning, the thickness of the CdS layer reaches 200 nm.

[0041] During the window layer deposition, for the zinc oxide layer, the sputtering power is 120 W, the argon / oxygen flow rate is 25 sccm / 7 sccm, the pressure is 1.2 Pa, and the deposition time is 20 minutes with a thickness of about 80 nm. Subsequently, for the ITO layer, the sputtering power is 180 W, the argon flow rate is 25 sccm, the pressure is 1.2 Pa, and the deposition time is 25 minutes with a thickness of about 120 nm. After completion, it is heat - treated at 200 °C for 30 minutes.

[0042] During the negative electrode evaporation, the thickness of the nickel layer is 55 nm, the evaporation temperature is 1300 °C, and the evaporation rate is 0.1 nm / s; the thickness of the aluminum layer is 1000 nm, the evaporation temperature is 1250 °C, and the evaporation rate is 0.5 nm / s. The vacuum degree is controlled below 1×10 -3 Pa.

[0043] Comparative example 1: Compared with Example 1, the difference is that tin disulfide is not added during the annealing process, and the rest are the same.

[0044] Comparative example 2: Compared with Example 2, the difference is that the deposition process of the absorption layer is replaced from the chemical bath method to the traditional sputtering method, and the rest are the same.

[0045] Comparative example 3: Compared with Example 3, the difference is that the selenization annealing temperature of the absorption layer is set to 600 °C, but the gas flow rate and annealing time are not precisely controlled, and the rest are the same.

[0046] Experiment 1: Photovoltaic Conversion Efficiency Test Experiment Experiment Purpose Test and compare the difference in photovoltaic conversion efficiency between Example 1 and Comparative Example 1 under standard solar illumination conditions, and verify the effect of tin disulfide participation in annealing on device performance improvement.

[0047] Experiment Steps Preliminarily encapsulate the solar cell devices prepared in Example 1 and Comparative Example 1, and seal them with a transparent glass cover plate and epoxy resin to ensure the cleanliness of the device surface during testing and avoid external interference.

[0048] Before testing, place the device in a drying oven with an environmental humidity of less than 40% for 12 hours of pretreatment to remove adsorbed water vapor on the surface and ensure the accuracy of the test results.

[0049] Use a solar simulator (AM1.5G spectrum, irradiation intensity 100mW / cm 2 ) to preheat the simulator light source for 30 minutes to ensure stable light intensity.

[0050] Place the sample on the probe station and use four-probe contact electrodes; Sweep the voltage in the range of 0 - 1V through a source meter (such as Keithley 2400 type), and record the current-voltage (I-V) characteristic curve of the device; Each sample is tested 5 times, and the average value is taken. At the same time, record the open-circuit voltage (Voc), short-circuit current density (Jsc), fill factor (FF), and photovoltaic conversion efficiency (PCE).

[0051] Record the test results of each time in a table. After removing obvious outliers, statistically analyze the average efficiency of each group of samples and conduct a comparative analysis.

[0052] Keep the surface of the sample clean during the test without dust pollution; Minimize the contact time of the test head during testing to avoid performance changes of the device due to heating; Control the detection frequency of light source stability at once per hour.

[0053] Table Name: Comparative Data of Photovoltaic Conversion Efficiency Performance Summary: From the above comparative experiments, it can be seen that in Example 1 with tin disulfide participating in annealing, the open-circuit voltage, short-circuit current density, and photoelectric conversion efficiency of the device are all better than those in Comparative Example 1 without adding tin disulfide. Tin disulfide plays an important auxiliary role in the annealing atmosphere, which can effectively regulate the element migration and equilibrium reaction of the absorption layer during the high-temperature selenization process, inhibit the component segregation phenomenon caused by the volatilization of sulfur and selenium during the film formation process, thereby forming an absorption layer structure with a more uniform composition and a lower defect density, and significantly improving the overall performance of the device.

[0054] Further analysis shows that introducing a tin disulfide atmosphere during annealing can release an appropriate amount of sulfur and tin elements, participate in the reconstruction reaction of the surface and grain boundaries, reduce the density of non-radiative recombination centers inside the device, and at the same time promote the grain growth and orientation optimization of the absorption layer. By optimizing the microstructure through atmosphere regulation, the carrier transport characteristics and interface energy band matching are significantly improved, thereby achieving a coordinated improvement in the open-circuit voltage, short-circuit current density, and fill factor.

[0055] The experimental results fully verify the key role played by the tin disulfide-assisted atmosphere during the annealing of the absorption layer, indicating that the quality of the thin film material and the optoelectronic performance of the device can be effectively improved by regulating the atmosphere components.

[0056] Experiment 2: Comparative test of deposition processes Experimental purpose: To compare the effects of the chemical bath method and the sputtering method in the deposition of the absorption layer, and focus on testing the uniformity, thickness control, and optoelectronic performance of the film layer.

[0057] Experimental steps: Use the chemical bath method and the sputtering method to prepare copper-zinc-tin-sulfide absorption layer and CIGS absorption layer thin films respectively.

[0058] Use a surface roughness meter (AFM) to measure the film layer thickness and evaluate the film layer uniformity.

[0059] Perform multi-point thickness measurements on each sample to ensure the uniformity of the deposited film layer.

[0060] Use an ultraviolet-visible spectrometer (UV-Vis) to perform light absorption tests on the prepared thin films and measure the changes in absorbance (Abs) at different wavelengths.

[0061] Mainly focus on the performance of the absorbance in the range of 300 nm to 800 nm.

[0062] Use a scanning electron microscope (SEM) to observe the surface morphology of the thin films, and analyze the grain size, distribution, and surface defects of the thin films.

[0063] Use a solar simulator to perform optoelectronic performance tests on the thin films and obtain the photoelectric conversion efficiency (PCE).

[0064] Measure the current-voltage characteristics (J-V curve) of the measuring device and extract key electrical performance parameters such as open-circuit voltage (Voc) and short-circuit current density (Jsc) from it.

[0065] Analyze the crystallization quality of the film layer by X-ray diffraction (XRD), determine the main crystal phases and their intensities, and evaluate the influence of different deposition processes on the crystallization of the film layer.

[0066] Data recording and analysis: Record the differences in light absorption, electrical properties, and crystal quality of the thin films prepared under each deposition process.

[0067] Provide guidance for further optimizing the preparation process by comparing and analyzing the advantages and disadvantages of the chemical bath method and the sputtering method.

[0068] Table name: Comparative test data of deposition processes Summary; In this experiment, the comparative experiment between the chemical bath method and the sputtering method revealed the significant influence of the two deposition processes on the film properties, especially in terms of light absorption ability, film layer uniformity, and optoelectronic properties. Due to its mild deposition environment and the synergistic effect of solution chemical reactions, the chemical bath method can more uniformly control the thickness and crystallinity of the thin film, making the surface of the prepared thin film smoother and reducing the generation of interface defects. This uniformity and lower roughness directly contribute to the improvement of optoelectronic properties, especially the advantages in light absorption and carrier transport, thus making the thin film prepared by the chemical bath method perform better in terms of photoelectric conversion efficiency.

[0069] Compared with the chemical bath method, due to its higher deposition energy, the sputtering method is prone to produce a rougher surface and larger particles, resulting in poorer film layer uniformity. The larger roughness of the film surface increases the interface defects, and photo-generated carriers are easily recombined at the defects, thus losing a part of the optoelectronic energy. These defects in surface morphology and crystallinity not only affect the stability of optoelectronic properties but also limit the improvement of short-circuit current density and photoelectric conversion efficiency. Therefore, although the sputtering method can obtain a thicker film layer in some cases, its optoelectronic properties are relatively poor and fail to reach the performance level of the chemical bath method.

[0070] Combining experimental data with theoretical mechanism analysis, the chemical bath method can achieve a better crystal structure and reduce the formation of defects by precisely controlling the film deposition process. This mechanism significantly improves the light absorption efficiency, and the uniformity of the film layer provides a smoother path for carrier transport, thus effectively enhancing the photoelectric conversion efficiency.

[0071] Experiment 3: Influence of different temperatures on optoelectronic properties Experimental Purpose: To study the effects of different deposition temperatures on the optoelectronic properties and crystallization quality of copper-zinc-tin-sulfide (CZTS) absorber layer thin films, and to analyze the influence of temperature on the film layer uniformity and photoelectric conversion efficiency.

[0072] Experimental Procedures: At different deposition temperatures, copper-zinc-tin-sulfide (CZTS) absorber layer thin films were prepared using the chemical bath deposition method. The temperature range was selected from 300 °C to 600 °C, and different temperature conditions were set in sequence.

[0073] The film thickness of each sample was measured using an atomic force microscope (AFM), and the average thickness and its uniformity of each sample were recorded.

[0074] The absorbance of each thin film sample was measured using a UV-visible spectrometer (UV-Vis), mainly focusing on the wavelength range from 400 nm to 800 nm.

[0075] The absorbance changes of the thin films deposited at different temperatures were recorded.

[0076] The surface morphology of the thin films was observed using a scanning electron microscope (SEM), and the film layer uniformity, grain size, and surface defects under different temperature conditions were analyzed.

[0077] The optoelectronic properties of each sample were tested using a solar simulator, and the photoelectric conversion efficiency (PCE) and current-voltage (J-V) characteristic curves were obtained.

[0078] Parameters such as open-circuit voltage (Voc), short-circuit current density (Jsc), and fill factor (FF) were recorded.

[0079] X-ray diffraction (XRD) analysis was performed on the thin films deposited at different temperatures to determine the crystallization quality, crystal phase formation, and crystallinity of the thin films.

[0080] The optoelectronic property and surface morphology data at different deposition temperatures were recorded, and the influence of temperature on the thin film properties was analyzed, especially the changes in light absorption, film layer uniformity, and electrical properties.

[0081] Table Name: Experimental Data on the Influence of Deposition Temperature on Optoelectronic Properties Summary; In this experiment, we studied the effect of deposition temperature on the properties of copper-zinc-tin-sulfide (CZTS) absorber layer thin films by adjusting the deposition temperature. As the temperature increased, the crystallinity and optoelectronic properties of the thin films were significantly improved. Especially under the condition of 500 °C, the power conversion efficiency of the thin films reached the optimal value. This phenomenon is closely related to the influence of deposition temperature on the crystal structure of the thin films. At lower temperatures, the crystallinity of the thin films is poor, the grain size is small and uneven, which will limit the light absorption ability and the generation of current. At higher temperatures, although the growth of grains is enhanced, too high a temperature may also cause overheating of the film layer, resulting in more defects, which will instead affect the optoelectronic properties. Therefore, precise control of the temperature is crucial to achieve optimal crystallization and optoelectronic properties.

[0082] When further analyzing the influence of temperature on the light absorption ability of the thin films, we found that as the deposition temperature increased, the absorbance of the thin films in the short-wavelength region increased, indicating that the light absorption ability was optimized with the increase of temperature. Behind this mechanism is the regulatory effect of temperature on the energy band structure and light absorption characteristics of the material. Higher deposition temperatures contribute to more complete chemical reactions and ordered crystal arrangements, enhancing the absorbance and the generation efficiency of photo-generated carriers. However, when the temperature is too high, the increase in surface roughness may lead to more defects, suppressing the further improvement of optoelectronic properties, which is also the reason why the thin films at 600 °C have a decrease in power conversion efficiency.

[0083] From the surface morphology of the thin films and the X-ray diffraction results, a moderate deposition temperature can achieve better thin film uniformity and crystal arrangement, thereby reducing defects and improving the carrier transport efficiency. The thin films at 500 °C showed the most uniform grain distribution and lower surface roughness, which directly promoted the generation of photocurrent and the improvement of power conversion efficiency.

[0084] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A preparation method of a semiconductor thin film solar cell, characterized in that, It includes the following steps: S1. Substrate cleaning: Ultrasonically clean the substrate successively with deionized water, alcohol and lye for 5 - 10 minutes, and then dry the substrate with nitrogen after cleaning; S2. Positive electrode deposition: Deposit a molybdenum thin film on the substrate by magnetron sputtering; S3. Preparation of precursor film: Prepare the precursor film by sol - gel method, control the thickness of the precursor film between 200 - 3000 nm, and uniformly coat the precursor solution on the molybdenum electrode by spin - coating method; S4. Selenization annealing: Put the precursor film, selenium grains and tin disulfide into a graphite box and anneal in the atmosphere of a compound composed of IV - VI group elements; S5. Buffer layer deposition: Deposit a cadmium sulfide buffer layer on the absorption layer by chemical bath deposition method; S6. Window layer deposition: Deposit an intrinsic zinc oxide layer and an indium tin oxide layer on the buffer layer by radio frequency magnetron sputtering method; S7. Negative electrode deposition: Prepare a nickel - aluminum grid electrode on the window layer by vacuum evaporation method; S8. Encapsulation: Appropriately encapsulate the thin - film solar cell.

2. The preparation method of a semiconductor thin film solar cell according to claim 1, characterized in that The substrate is soda - lime glass or quartz glass with a thickness of 0.1 - 2 mm.

3. The preparation method of a semiconductor thin-film solar cell according to claim 1, characterized in that, The magnetron sputtering method in step 2 specifically includes the following steps; On the surface of the cleaned and dried substrate, first carry out the first - stage molybdenum sputtering deposition with a sputtering power of 130 - 170 W, a sputtering time of 1.0 - 2.0 minutes, and a sputtering pressure of 0.3 - 0.6 Pa; Immediately followed by the second - stage molybdenum sputtering deposition with a sputtering power of 30 - 70 W, a sputtering time of 0.3 - 0.7 minutes, and a sputtering pressure of 0.05 - 0.15 Pa; The target used in the two - stage sputtering process is a molybdenum target with a purity of not less than 99.9%, and the total thickness of the molybdenum film is controlled between 500 - 5000 nm.

4. The preparation method of a semiconductor thin-film solar cell according to claim 1, characterized in that, Step 3 specifically includes the following steps; Prepare the precursor solution, and dissolve it by adding copper source, zinc source, tin source and sulfur source into the solvent in sequence. The solvent is deionized water or ethanol - deionized water mixed solvent with a volume ratio of 1:1 - 1:3 Stir the solution at room temperature for 30 - 90 minutes until a clear and transparent solution is formed; Coat the precursor solution on the surface of the molybdenum positive electrode by spin - coating method with a spin - coating rate of 1000 - 3000 rpm and a spin - coating time of 30 - 60 seconds; After spin - coating, heat it at 100 - 200 °C for 5 - 15 minutes for pre - drying to remove the solvent; Through multiple alternations of spin - coating and pre - drying until the thickness of the precursor film reaches 200 - 3000 nm.

5. The preparation method of a semiconductor thin film solar cell according to claim 4, characterized in that, The concentration of the copper source as copper nitrate is 0.05 - 0.2 mol / L, the concentration of the zinc source as zinc nitrate is 0.02 - 0.1 mol / L, the concentration of the tin source as tin nitrate is 0.02 - 0.1 mol / L, and the concentration of the sulfur source as thiourea is 0.5 - 2 mol / L.

6. The preparation method of a semiconductor thin-film solar cell according to claim 1, characterized in that, Step S4 specifically includes the following steps; Put the precursor film, selenium grains and 1 - 5 mg of tin disulfide into a graphite box together; Put the graphite box into a tube furnace, set the temperature of the tube furnace to 450 - 600 °C, and the annealing time to 10 - 30 minutes; During the annealing process, the furnace atmosphere is a compound atmosphere composed of IV-VI group elements. The IV-VI group element compounds include, but are not limited to, tin sulfide, tin disulfide, and tin selenide. The gas flow rate is controlled at 50-150 sccm; The reaction gas during the annealing process participates in the reaction to form an absorption layer, and the thickness of this absorption layer is 500-3000 nm; After the annealing is completed, quickly take out the sample and let it cool naturally at room temperature. The cooling time is 10-30 minutes.

7. The preparation method of a semiconductor thin film solar cell according to claim 1, characterized in that, The specific steps in step S5 include the following steps; Deposit a cadmium sulfide buffer layer by chemical bath deposition: Place the absorption layer in a cadmium sulfide solution; The solvent is deionized water to ensure the uniformity of the solution and the stability of the reaction; By controlling the temperature of the solution, keep it at 60-90 °C, and carry out chemical bath reaction at this temperature to deposit the cadmium sulfide buffer layer. The deposition time is controlled at 10-30 minutes; Control the thickness of the deposited CdS layer to be between 30-200 nm; After the deposition is completed, take out the sample and wash it with deionized water to remove the chemical substances remaining on the surface, and finally dry it naturally at room temperature.

8. The preparation method of a semiconductor thin film solar cell according to claim 7, characterized in that, The cadmium sulfide solution contains: Hydrogen sulfide solution with a concentration of 0.1-1 mol / L; Cadmium nitrate solution with a concentration of 0.05-0.2 mol / L.

9. The preparation method of a semiconductor thin film solar cell according to claim 1, characterized in that, The specific steps in step S6 include the following steps; Deposit an intrinsic zinc oxide layer on the surface of the buffer layer by radio frequency magnetron sputtering. The thickness of the zinc oxide layer is 40-80 nm, the sputtering power is 80-120 W, the sputtering atmosphere is a mixed gas of argon and oxygen, the sputtering pressure is 0.8-1.2 Pa, and the sputtering time is 10-20 minutes; Continue to deposit an indium tin oxide layer on the zinc oxide layer by radio frequency magnetron sputtering. The thickness of the indium tin oxide layer is 80-120 nm, the sputtering power of the indium tin oxide layer is 130-180 W, the sputtering atmosphere is pure argon, the gas flow rate is 15-25 sccm, the sputtering pressure is 0.8-1.2 Pa, and the sputtering time is 15-25 minutes; After the window layer deposition is completed, perform heat treatment at 150-200 °C. The heat treatment time is 10-30 minutes.

10. The preparation method of a semiconductor thin film solar cell according to claim 1, characterized in that, The specific steps in step S7 include the following steps; Deposit a nickel-aluminum double-layer metal grid electrode on the surface of the window layer by vacuum evaporation. The total thickness of the nickel-aluminum electrode is 950-1050 nm First, deposit a nickel layer with a thickness of 45 - 55 nm. Use a high-purity metal nickel evaporation source, control the evaporation temperature at 1200 - 1300 °C, the evaporation rate is 0.05 - 0.10 nm / s, keep the pressure in the vacuum chamber below 1×10 -3 Pa, and the evaporation time is 8 - 15 minutes; Deposit an aluminum layer on the nickel layer. The thickness of the aluminum layer is 900 - 1000 nm. Use a high-purity metal aluminum evaporation source, control the evaporation temperature at 1100 - 1250 °C, the evaporation rate is 0.2 - 0.5 nm / s, keep the pressure in the vacuum chamber below 1×10 -3 Pa, and the evaporation time is 20 - 60 minutes.

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