Ga-doped Zn (O, S) thin film and preparation method and application thereof

Abstract

The invention discloses a Ga-doped Zn (O, S) thin film and a preparation method and application thereof, and relates to the technical field of thin film solar cells, the preparation method comprises the following steps: adding a gallium source into a zinc source solution to obtain a Ga: Zn solution; then uniformly mixing with a thioacetamide solution, ammonia water and ultrapure water to obtain a precursor solution; immersing a substrate into the precursor solution, and forming a film by adopting a chemical bath deposition method to obtain a Ga: Zn (O, S) precursor film; and annealing the Ga: Zn (O, S) precursor film to obtain the Ga-doped Zn (O, S) film. By doping Ga into the Zn (O, S) thin film, the electrical property and the thin film quality are remarkably improved, and when the Zn (O, S) thin film is used as a solar cell buffer layer, the width of a depletion region can be effectively widened, effective separation of photon-generated carriers in a junction region is promoted, interface recombination is reduced, and the photoelectric conversion efficiency of a device is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of thin-film solar cells, and in particular to a Ga-doped Zn(O, S) thin film and a preparation method and application thereof. Background Art

[0002] Copper indium gallium selenide (CuInGaSe2, CIGSe) thin-film solar cells have become a research hotspot in the photovoltaic field due to their excellent light absorption properties and high conversion efficiency. Currently, high-efficiency CIGSe solar cells typically have a bandgap of approximately 1.12 eV. While this bandgap has enabled cell efficiencies of up to 23.6%, it still does not fully meet the high open-circuit voltage and low short-circuit current requirements of solar cell modules. The rapid development of tandem cell technology has placed higher demands on top cell materials, particularly the need for a wider bandgap to increase voltage output and optimize spectral absorption matching. Therefore, widening the bandgap is crucial for improving the performance of CIGSe solar cells and expanding their applications.

[0003] Currently, the development of wide-bandgap CIGSe cells faces challenges. High Ga content causes the conduction band to shift upward. When the Ga / (Ga+In) ratio exceeds 0.5 (Eg=1.3 eV), the interface band step change causes the open-circuit voltage to saturate. Studies have shown that replacing the CdS buffer layer with a wide-bandgap n-type semiconductor can improve the energy band matching. The Zn(O,S) / CdS double buffer layer structure developed by our research group in the early stage successfully achieved the optimized matching of the interface energy band gradient before and after the wide-bandgap buffer layer. Although it alleviated the interface recombination to a certain extent, the V oc The theoretical value has not yet been reached. Moreover, compared with the traditional CdS buffer layer, the material properties of Zn(O,S) are significantly limited. The lower carrier concentration leads to a smaller depletion region width, which limits the effective separation of photogenerated carriers in the junction region. In addition, the low mobility leads to an increase in device series resistance, further exacerbating the interface recombination. Especially when the wide-bandgap CIGSe absorption layer and the buffer layer form a heterojunction, the lower conductivity of the buffer layer and the shorter carrier lifetime of the absorption layer jointly exacerbate the non-radiative recombination of photogenerated carriers during transmission, significantly suppressing the short-circuit current density (J sc ) and fill factor (FF) improvement.

[0004] Therefore, how to improve the carrier concentration and film quality of the buffer layer, reduce interfacial recombination, and promote effective carrier separation and transmission on the basis of optimizing the band matching of the wide-bandgap CIGSe absorber layer and the Zn(O,S) buffer layer is an urgent task to achieve high-efficiency photoelectric conversion efficiency of wide-bandgap CIGSe devices. Summary of the Invention

[0005] In order to solve the above technical problems, the purpose of the present invention is to provide a Ga-doped Zn(O,S) thin film and its preparation method and application. By doping Ga into the Zn(O,S) thin film, the present invention significantly improves the electrical properties and film quality. When it is used as a buffer layer of a solar cell, it can effectively widen the depletion region width, promote the effective separation of photogenerated carriers in the junction region, reduce interface recombination, and significantly improve the photoelectric conversion efficiency of the device.

[0006] The technical solution of the present invention to solve the above technical problems is as follows: providing a Ga-doped Zn(O,S) film (Ga:Zn(O,S) film), in which 0.001-5 wt% gallium (Ga) is doped into the Zn(O,S) film.

[0007] Furthermore, the gallium doping amount is 1-3 wt%.

[0008] The present invention also provides a method for preparing the Ga-doped Zn(O,S) thin film, comprising the following steps: (1) Adding a gallium source into an aqueous solution of a zinc source to dissolve the solution to obtain a Ga:Zn solution; (2) uniformly mixing the Ga:Zn solution obtained in step (1), thioacetamide (TAA) solution, ammonia water and ultrapure water to obtain a precursor solution; (3) immersing the substrate in the precursor solution obtained in step (2), and forming a film on the surface of the substrate by chemical bath deposition to obtain a Ga:Zn(O,S) precursor film; (4) Under an O2 / N2 mixed atmosphere, the Ga:Zn(O,S) precursor film obtained in step (3) is annealed to obtain a Ga-doped Zn(O,S) film.

[0009] Furthermore, in step (1), the gallium source is at least one of gallium sulfate, gallium acetate, gallium nitrate and gallium chloride.

[0010] Furthermore, in step (1), the zinc source is at least one of zinc sulfate, zinc acetate, zinc nitrate and zinc chloride.

[0011] Furthermore, in step (2), the concentration of the gallium source in the precursor solution is 0.001-0.05 M, the concentration of the zinc source is 0.05-0.5 M, the concentration of thioacetamide is 0.02-0.2 M, and the concentration of ammonia water is 2-8 M.

[0012] Furthermore, in step (3), the chemical bath deposition method is: treating at 40-90° C. and stirring at 100-800 r / min for 1-10 min.

[0013] Furthermore, in step (4), the annealing process is: heating to 50-300°C at a rate of 2-10°C / min and keeping the temperature for 5-30 min, and then cooling to room temperature at a rate of 5-15°C / min.

[0014] Furthermore, in step (4), the proportion of O2 in the O2 / N2 mixed atmosphere is 10%-40%.

[0015] The present invention also provides application of the Ga-doped Zn(O, S) film in solar cells.

[0016] The present invention also provides a wide bandgap CIGSe battery, comprising a soda-lime glass substrate, a molybdenum back electrode, a CIGSe absorption layer, the above-mentioned Ga-doped Zn(O,S) film, a CdS buffer layer, an i-ZnO / Al:ZnO window layer and a Ni:Al gate.

[0017] Furthermore, the thickness of the molybdenum back electrode is 400-1000 nm; the thickness of the CIGSe film is 1-3 μm; the thickness of the Ga-doped Zn(O,S) film is 40-80 nm; the thickness of the CdS buffer layer is 10-50 nm; the thickness of the i-ZnO is 40-110 nm; the thickness of the Al:ZnO is 200-600 nm; the thickness of the Ni gate line is 0.1-0.3 nm; and the thickness of the Al gate line is 40-100 nm.

[0018] The present invention has the following beneficial effects: 1. This invention provides a Ga-doped Zn(O,S) thin film with significantly improved electrical properties and film quality. When used as a buffer layer in CIGSe cells, it can effectively widen the depletion region, promote the effective separation of photogenerated carriers within the junction region, significantly reduce interfacial recombination, and thus improve the device's photoelectric conversion efficiency.

[0019] 2. The preparation method of the present invention uses chemical bath deposition and controlled atmosphere annealing to produce Ga:Zn(O,S) thin films with excellent crystal quality, density and surface smoothness. This method is simple and efficient and has good prospects for industrial application. 3. The Ga:Zn(O,S) thin film of the present invention serves as a buffer layer, effectively promoting the separation and transmission of carriers, and significantly improving the photoelectric conversion efficiency of the battery, with an improvement of up to 4%. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 1 is a comparison diagram of the JV curves of the solar cells of Example 4 and Comparative Example 1; Figure 2 EQE curve comparison of the solar cells of Example 4 and Comparative Example 1; Figure 3Comparison of CV curves of the solar cells of Example 4 and Comparative Example 1. DETAILED DESCRIPTION

[0021] The principles and features of the present invention are described below. The examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. In the examples, where specific conditions are not specified, conventional conditions or manufacturer-recommended conditions were used. Reagents or instruments used where the manufacturer is not specified are conventional products that can be purchased commercially.

[0022] Example 1 A Ga-doped Zn(O,S) thin film, the preparation method of which comprises the following steps: (1) Add gallium acetate to an aqueous solution of zinc sulfate and dissolve it to obtain a Ga:Zn solution; (2) The Ga:Zn solution obtained in step (1), thioacetamide (TAA) solution, ammonia water and ultrapure water are uniformly mixed to obtain a precursor solution; the concentration of the gallium source in the precursor solution is 0.033 M, the concentration of the zinc source is 0.475 M, the concentration of thioacetamide is 0.05 M, and the concentration of ammonia water is 5 M; (3) Immersing the substrate in the precursor solution obtained in step (2), and depositing the Ga:Zn(O,S) precursor thin film on the substrate surface at 60°C and 200 r / min stirring for 6 min using a chemical bath deposition method; (4) In an O2 / N2 mixed atmosphere (O2 ratio of 15%), the Ga:Zn(O,S) precursor film obtained in step (3) was annealed (heated to 200°C at a rate of 5°C / min and kept at this temperature for 12 min, and then cooled to room temperature at a rate of 10°C / min) to obtain a Ga-doped Zn(O,S) film.

[0023] Example 2 A Ga-doped Zn(O,S) thin film, the preparation method of which comprises the following steps: (1) Add gallium sulfate to an aqueous solution of zinc acetate and dissolve it to obtain a Ga:Zn solution; (2) The Ga:Zn solution obtained in step (1), thioacetamide (TAA) solution, ammonia water and ultrapure water are uniformly mixed to obtain a precursor solution; the concentration of the gallium source in the precursor solution is 0.001 M, the concentration of the zinc source is 0.05 M, the concentration of thioacetamide is 0.02 M, and the concentration of ammonia water is 2 M; (3) Immersing the substrate in the precursor solution obtained in step (2), forming a film on the substrate surface by chemical bath deposition at 40°C and 100 r / min stirring for 10 min to obtain a Ga:Zn(O,S) precursor film; (4) In an O2 / N2 mixed atmosphere (O2 ratio of 10%), the Ga:Zn(O,S) precursor film obtained in step (3) was annealed (heated to 50°C at a rate of 2°C / min and kept warm for 30 min, and then cooled to room temperature at a rate of 5°C / min) to obtain a Ga-doped Zn(O,S) film.

[0024] Example 3 A Ga-doped Zn(O,S) thin film, the preparation method of which comprises the following steps: (1) Adding a gallium source into an aqueous solution of a zinc source to dissolve the solution to obtain a Ga:Zn solution; (2) The Ga:Zn solution obtained in step (1), thioacetamide (TAA) solution, ammonia water and ultrapure water are uniformly mixed to obtain a precursor solution; the concentration of the gallium source in the precursor solution is 0.05 M, the concentration of the zinc source is 0.5 M, the concentration of thioacetamide is 0.2 M, and the concentration of ammonia water is 8 M; (3) Immersing the substrate in the precursor solution obtained in step (2), forming a film on the substrate surface by chemical bath deposition at 90°C and 800 r / min stirring for 1 min, to obtain a Ga:Zn(O,S) precursor film; (4) In an O2 / N2 mixed atmosphere (O2 ratio of 40%), the Ga:Zn(O,S) precursor film obtained in step (3) was annealed (heated to 300°C at a rate of 10°C / min and kept at this temperature for 5 min, and then cooled to room temperature at a rate of 15°C / min) to obtain a Ga-doped Zn(O,S) film.

[0025] Example 4 A wide bandgap CIGSe cell comprising a soda-lime glass substrate, a molybdenum back electrode, a CIGSe absorption layer, a Ga-doped Zn(O,S) thin film prepared according to the method of Example 1, a CdS buffer layer, an i-ZnO / Al:ZnO window layer, and a Ni:Al gate; The preparation process of the wide bandgap CIGSe solar cell is as follows: (1) After cleaning the soda-lime glass substrate, vacuum dry it at 80°C for 30 min to ensure that the surface is clean and free of contamination; (2) A double-layer Mo back electrode was deposited on a pretreated soda-lime glass substrate using a DC magnetron sputtering method. The thickness of the first Mo layer was 400 nm (deposition conditions: sputtering pressure 0.1 Pa, sputtering current 1.5 A), and the thickness of the second Mo layer was 600 nm (deposition conditions: sputtering pressure 0.2 Pa, sputtering current 1.5 A). (3) A CIGSe absorption layer was deposited on the Mo back electrode using a three-step co-evaporation method (the specific process parameters were: the substrate temperature was set to 400°C, 550°C, and 550°C in sequence, Ga was pre-evaporated for 2 min, In and Ga were co-evaporated in the first step, Ga and Cu were co-evaporated in the second step, and In and Ga were co-evaporated in the third step. The film thickness was controlled at 1.5 μm. E g is 1.43 eV); (4) Prepare a Ga:Zn(O,S) thin film as a buffer layer using the method of Example 1; (5) The CdS buffer layer was prepared in sequence by chemical bath deposition. 0.03 M Cd source, 1.5 M thiourea, and 3.2 M ammonia were added to 500 mL of deionized water. The deposition temperature was controlled at 70 °C, the deposition time was 6 min, and the stirring speed was 600 r / min. A CdS buffer layer with a thickness of 30 nm was obtained. (6) Magnetron sputtering was used to sequentially deposit i-ZnO (deposition conditions: sputtering pressure 0.75 Pa, sputtering power 70 W, deposition thickness 50 nm) and Al:ZnO window layer (Al:ZnO deposition conditions: sputtering pressure 0.4 Pa, sputtering power 250 W, deposition thickness 350 nm); (7) Electron beam evaporation was used to deposit Ni:Al gate electrodes with a Ni electrode thickness of 0.4 nm, followed by an Al electrode with a thickness of 60 nm.

[0026] Comparative Example 1 A wide bandgap CIGSe battery, which differs from Example 4 in that the Zn(O,S) film is not doped with Ga.

[0027] Test Example 1 (1) Comparison of JV curves of solar cells of Example 4 and Comparative Example 1 Figure 1 As shown, the comparison of various parameters of the solar cells of Example 4 and Comparative Example 1 is shown in Table 1.

[0028] Table 1 Comparison of parameters of solar cells of Example 4 and Comparative Example 1

[0029] Depend on Figure 1 It can be seen that the Ga-doped Zn(O,S) buffer layer significantly improves the photoelectric performance of the wide-bandgap CIGSe device, and the photoelectric conversion efficiency is increased from 11.13% to 14.64%. According to the analysis in Table 1, Ga doping improves all photovoltaic parameters, especially J sc (from 18.12 mA / cm 2 Increased to 21.54 mA / cm 2) and FF (from 72.5% to 76.2%). This change is attributed to Ga doping, which optimizes the electrical properties of the buffer layer, thereby promoting carrier separation and transport. This effective increase in carrier mobility reduces the series resistance of the film and slows down heterojunction interface recombination.

[0030] (2) Comparison of EQE curves of solar cells of Example 4 and Comparative Example 1 Figure 2 The results show that after Ga doping the Zn(O,S) buffer layer, the EQE response of the CIGSe device in the entire band is improved, indicating that doping improves the heterojunction interface contact and promotes carrier collection.

[0031] (3) Comparison of CV curves of solar cells of Example 4 and Comparative Example 1 Figure 3 The results show that after Ga doping, the depletion region width of the Zn(O,S) buffer layer increases significantly, which is conducive to the effective separation of photogenerated carriers in the junction region, thereby improving the device efficiency.

[0032] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements or improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A Ga-doped Zn(O,S) thin film, characterized in that: 0.001-5wt% gallium was doped into the Zn(O,S) film.

2. The method for preparing the Ga-doped Zn(O,S) thin film according to claim 1, characterized in that: The following steps are involved: (1) Adding a gallium source into an aqueous solution of a zinc source to dissolve the solution to obtain a Ga:Zn solution; (2) uniformly mixing the Ga:Zn solution, thioacetamide solution, ammonia water and ultrapure water obtained in step (1) to obtain a precursor solution; (3) immersing the substrate in the precursor solution obtained in step (2), and forming a film on the surface of the substrate by chemical bath deposition to obtain a Ga:Zn(O,S) precursor film; (4) Under an O2 / N2 mixed atmosphere, the Ga:Zn(O,S) precursor film obtained in step (3) is annealed to obtain a Ga-doped Zn(O,S) film.

3. The method for preparing a Ga-doped Zn(O,S) thin film according to claim 2, wherein: In step (1), the gallium source is at least one of gallium sulfate, gallium acetate, gallium nitrate and gallium chloride.

4. The method for preparing a Ga-doped Zn(O,S) thin film according to claim 2, wherein: In step (1), the zinc source is at least one of zinc sulfate, zinc acetate, zinc nitrate and zinc chloride.

5. The method for preparing a Ga-doped Zn(O,S) thin film according to claim 2, wherein: In step (2), the concentration of the gallium source in the precursor solution is 0.001-0.05 M, the concentration of the zinc source is 0.05-0.5 M, the concentration of thioacetamide is 0.02-0.2 M, and the concentration of ammonia water is 2-8 M.

6. The method for preparing a Ga-doped Zn(O,S) thin film according to claim 2, wherein: In step (3), the chemical bath deposition method is: treating at 40-90° C. and stirring at 100-800 r / min for 1-10 min.

7. The method for preparing a Ga-doped Zn(O,S) thin film according to claim 2, wherein: In step (4), the annealing process is: heating to 50-300°C at a rate of 2-10°C / min and keeping the temperature for 5-30 min, and then cooling to room temperature at a rate of 5-15°C / min.

8. The method for preparing a Ga-doped Zn(O,S) thin film according to claim 2, wherein: In step (4), the proportion of O2 in the O2 / N2 mixed atmosphere is 10%-40%.

9. Use of the Ga-doped Zn(O,S) thin film according to claim 1 in solar cells.

10. A wide bandgap CIGSe battery, characterized in that: The invention comprises a soda-lime glass substrate, a molybdenum back electrode, a CIGSe absorption layer, the Ga-doped Zn(O, S) film according to claim 1, a CdS buffer layer, an i-ZnO / Al:ZnO window layer and a Ni:Al gate.

Images