Preparation method of copper-indium-gallium-selenium absorption layer and solar cell

Abstract

The invention provides a preparation method of a copper-indium-gallium-selenium absorption layer and a solar cell. The method comprises the following steps: preparing a CIGSe precursor in a hydrogen plasma environment by adopting a magnetron sputtering method, then depositing a layer of CIGSe film on the surface of the CIGSe precursor, and finally preparing the CIGSe gradient absorption layer through high-temperature annealing. According to the method, surface copper indium gallium sulfur is used as a cover layer to delay crystallization and promote transverse growth of crystal grains, meanwhile, hydrogen is used for reducing oxide to reduce surface sodium accumulation and defects, deep diffusion of the sulfur element is effectively inhibited, and the sulfur element is locked on the surface of the thin film. Through cooperative regulation and control, a compact and hole-free absorption layer with a steep surface sulfur gradient can be obtained, the carrier recombination loss is remarkably reduced, and the conversion efficiency of a CIGSe thin film solar cell prepared based on a sputtering method is greatly improved. The CIGSe gradient absorption layer is prepared by adopting the magnetron sputtering method, so that the method has the advantages of simple process, good consistency, high efficiency of the prepared solar cell and the like, and has a huge market application prospect.

Description

Technical Field

[0001] This invention relates to the field of thin-film solar cell technology, specifically to a method for preparing a copper indium gallium selenide (CIGS) absorber layer and a solar cell. Background Technology

[0002] With the rapid development of photovoltaic technology, chalcopyrite-based copper indium gallium selenide (CIGSe) thin films have become a highly anticipated candidate photovoltaic material due to their excellent stability, superior photovoltaic properties, and potential for multifunctional applications. Magnetron sputtering, as a crucial process for preparing CIGSe cells, has achieved a photoelectric conversion efficiency of 23.35%, approaching the highest record set by co-evaporation methods. However, for large-scale industrial application of magnetron sputtering technology, in addition to overcoming limitations such as the use of corrosive gases and equipment complexity, further improvements in photovoltaic performance are still constrained by two major bottlenecks: poor absorber crystal quality and insufficient carrier extraction at the heterojunction interface.

[0003] In recent years, cation doping and gradient bandgap engineering have become research hotspots to address crystal quality and interfacial recombination issues. While doping with alkali metals or silver can passivate defects or improve microstructure to some extent, it suffers from poor conductivity or the easy formation of secondary phases. On the other hand, gradient bandgap engineering is an effective means to enhance carrier extraction; however, in magnetron sputtering, the classic gallium gradient is difficult to control, while the silver gradient easily generates impurity phases. Although sulfur (S) gradients have been shown to significantly improve cell efficiency, the rapid diffusion of sulfur during annealing makes it difficult to achieve compatibility with sputtering processes and precise control of the sulfur gradient structure a technical challenge. Traditional methods typically control the sulfur gradient by changing the annealing method or altering the content and position of S, but these methods are not ideal in practice. Therefore, providing a CIGSe absorber layer preparation method that simultaneously optimizes absorber layer quality and provides controllable sulfur-grade gradient bandgap technology is crucial for suppressing bulk nonradiative recombination, optimizing interfacial band structure, and improving the efficiency of CIGSe thin-film solar cells. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing a copper indium gallium selenide (CIGS) absorber layer and a solar cell. This invention is based on hydrogen-assisted and surface sulfidation to form a CIGS absorber layer, thereby solving the problems of poor crystal quality, easy formation of internal pores, and difficulty in accurately controlling the sulfur gradient distribution of CIGSe thin films prepared by existing magnetron sputtering methods.

[0005] This invention is implemented as follows: A method for preparing a copper indium gallium selenide (CIGS) absorber layer includes the following steps: S1. Prepare a molybdenum electrode layer on the substrate; S2. An amorphous copper indium gallium selenide (CIGS) layer is deposited on a molybdenum electrode layer in an argon atmosphere using magnetron sputtering. S3. A crystalline copper indium gallium selenide (CIGS) precursor is deposited on an amorphous CIGS layer using magnetron sputtering in an argon and hydrogen plasma environment. Then, a wide-bandgap CIGS sulfide (CGS) layer is deposited on the surface of the crystalline CIGS precursor using magnetron sputtering in an argon environment. Finally, a CIGS gradient absorption layer is obtained by high-temperature annealing.

[0006] Preferably, in step S3, the conditions for depositing the crystalline copper indium gallium selenide precursor by magnetron sputtering are: a vacuum chamber ambient pressure of 0.2 Pa-1.0 Pa, a hydrogen concentration of 0-10%, and a sputtering power of 0.1 W / cm². 2 -8 W / cm 2 The substrate temperature is 350°C-650°C. More preferably, the hydrogen concentration is 3%-9%. Even more preferably, the hydrogen concentration is 5%-7%.

[0007] Preferably, in step S3, the conditions for depositing a wide-bandgap copper indium gallium sulfide layer using magnetron sputtering are: argon gas pressure in the vacuum chamber is 0.2 Pa-1.0 Pa, and sputtering power is 0.1 W / cm². 2 -8 W / cm 2 The substrate temperature is 350℃-650℃.

[0008] Preferably, in step S3, the thickness of the wide-bandgap copper indium gallium sulfide layer is 0.3%-15% of the thickness of the copper indium gallium selenide gradient absorption layer.

[0009] Preferably, in step S3, the thickness of the copper indium gallium selenide gradient absorption layer is 1000 nm-3000 nm.

[0010] Preferably, in step S2, an amorphous copper indium gallium selenide layer with a thickness of 40 nm to 100 nm is deposited at 10-30°C.

[0011] In the preparation of crystalline copper indium gallium selenide (CIGS) precursors, this invention introduces a mixed gas of argon and hydrogen, and applies DC power to excite and maintain a plasma environment containing active particles such as H radicals and ions within a chamber. By adjusting the hydrogen concentration of the hydrogen plasma and the thickness of the CIGS layer, the surface sulfur content can be controlled, avoiding charge barriers caused by inappropriate sulfur gradient initiation positions and undesirable band gaps.

[0012] To improve the photoelectric conversion efficiency of copper indium gallium selenide (CIGSe) thin-film solar cells prepared by selenide-free magnetron sputtering, this invention provides a method for preparing CIGSe thin-film solar cells based on the above-mentioned hydrogen-assisted and surface-sulfided process, comprising the following steps: S1. Prepare a molybdenum electrode layer on the substrate; S2. An amorphous copper indium gallium selenide (CIGS) layer is deposited on a molybdenum electrode layer in an argon atmosphere using magnetron sputtering. S3. A crystalline copper indium gallium selenide precursor is deposited on an amorphous copper indium gallium selenide layer by magnetron sputtering in an argon and hydrogen plasma environment. Then, a copper indium gallium sulfide layer is deposited on the surface of the crystalline copper indium gallium selenide precursor by magnetron sputtering in an argon environment. Finally, a copper indium gallium selenide gradient absorption layer is obtained by high-temperature annealing. S4. A buffer layer is prepared on the copper indium gallium selenide gradient absorption layer by chemical bath method or magnetron sputtering method. S5. A high-resistivity layer is prepared on the buffer layer by magnetron sputtering, and then a transparent conductive layer is prepared on the high-resistivity layer. S6. Patterned metal grid electrodes are prepared by vacuum evaporation.

[0013] Preferably, in step S1, the substrate is a soda-lime glass sheet, a thin stainless steel sheet, or a polyimide sheet.

[0014] For stainless steel or polyimide sheets, before depositing the molybdenum electrode layer in step S1 above, a barrier layer with a thickness of 50-400 nm is first deposited on the pretreated substrate using magnetron sputtering or PECVD. The barrier layer is preferably a silicon oxide film, titanium nitride film, or silicon nitride film. Then, a sodium-doped molybdenum layer is deposited on the barrier layer using magnetron sputtering. The target material used for depositing the sodium-doped molybdenum layer is a mixture of sodium molybdate and molybdenum (the sodium molybdate content in the target material is 0.5%-10%). The sputtering pressure is 0.2-1 Pa, and the sputtering power is 0.2-4 W / cm². 2 Then, a pure molybdenum electrode layer is deposited.

[0015] For soda-lime glass substrates, when depositing a pure molybdenum electrode layer using DC magnetron sputtering, a layer of molybdenum with a thickness of 400 nm–700 nm is first deposited under a relatively high Ar gas pressure of 1.5–3 Pa, followed by a layer of molybdenum with a thickness of 100 nm–400 nm under a relatively low Ar gas pressure of 0.2–1 Pa. The molybdenum film deposited under high Ar gas pressure exhibits tensile stress, resulting in good adhesion to the substrate but higher resistivity; the molybdenum film deposited under low Ar gas pressure exhibits tensile stress, resulting in poor adhesion to the substrate but lower resistivity. By sputtering molybdenum layers under both Ar gas pressure conditions, it is helpful to obtain a molybdenum electrode layer with excellent adhesion and conductivity.

[0016] The buffer layer mentioned in step S4 can be a cadmium sulfide film, a zinc sulfide film, an indium sulfide film, or a composite film of cadmium sulfide and zinc sulfide. The thickness of the buffer layer is 40~200 nm.

[0017] The high-resistivity layer mentioned in step S5 can be an intrinsic zinc oxide (i-ZnO) layer with a thickness of 80-200 nm. A transparent conductive layer with a thickness of 100-400 nm is then prepared on the high-resistivity layer using magnetron sputtering. The transparent conductive layer can be aluminum-doped zinc oxide (AZO), ITO, boron-doped zinc oxide, molybdenum-doped indium oxide (IMO), zinc-doped indium oxide (IZO), or titanium-doped indium oxide (ITiO).

[0018] The metal gate electrode mentioned in step S6 can be one or more of gold, silver, aluminum, copper, and nickel. Considering both cost and performance, the metal gate electrode is preferably an Al / Ni bilayer structure, wherein the Al layer thickness is 70-200 nm and the Ni layer thickness is 3-20 nm.

[0019] The present invention has the following beneficial effects: (1) In this invention, a copper indium gallium sulfide (CIGS) layer is formed on the surface of the absorber layer. As a capping layer, it effectively delays the rapid reaction at high temperatures and inhibits the evaporation of selenium and the formation of internal pores. At the same time, hydrogen is used to reduce oxides to reduce surface sodium accumulation and defects, and effectively prevents the deep diffusion of sulfur into the absorber layer, locking it on the surface of the film. This synergistic effect of hydrogen and the surface CIGS layer inhibits the deep diffusion of sulfur and eliminates oxide impurities, realizing a dense, pore-free absorber layer structure with a steep and controllable surface sulfur gradient, solving the problem of difficulty in maintaining the gradient in traditional sulfurization processes.

[0020] (2) The CIGSe absorber layer prepared by the method of the present invention eliminates thin film pores, significantly reducing bulk defect density and interfacial carrier recombination loss. Solar cells prepared based on this absorber layer have significantly improved photoelectric conversion efficiency due to their excellent crystal quality and optimized surface band structure, providing an effective approach for the preparation of high-efficiency sputtering CIGSe cells.

[0021] (3) The present invention uses magnetron sputtering process to prepare the absorber layer of CIGSe thin film solar cell, which does not require subsequent sulfurization annealing, has low equipment requirements, and the resulting product has controllable performance and good consistency, making it suitable for industrial production. Attached Figure Description

[0022] Figure 1 is a SEM image of the CIGSe absorption layer prepared in Example 1, Comparative Example 1 and Comparative Example 2 of the present invention; wherein, (a) is a SEM image of the CIGSe absorption layer in Comparative Example 1, (b) is a SEM image of the CIGSe absorption layer in Comparative Example 2, and (c) is a SEM image of the CIGSe absorption layer in Example 1.

[0023] Figure 2The images are XRD test diagrams of the CIGSe absorption layers prepared in Examples 1, 1, and 2 of this invention, and the fitting results of the corresponding (112) full width at half maximum (FWHM). Among them, (a) is the XRD test diagram of the CIGSe absorption layers prepared in Examples 1, 1, and 2, and (b) is the fitting result of the FWHM of the corresponding (112) crystal plane diffraction peak in (a).

[0024] Figure 3 The results are XPS depth profiles of the S element in the CIGSe absorber layer of the samples in Comparative Example 2 and Example 2; where (a) is the XPS profile of the S element in the CIGSe absorber layer of the sample in Comparative Example 2, and (b) is the XPS profile of the S element in the CIGSe absorber layer of the sample in Example 2. Detailed Implementation

[0025] The present invention will be further described below with reference to embodiments. It should be noted that the description of these specific embodiments is only for the purpose of helping to understand the present invention and does not constitute a limitation of the present invention.

[0026] Example 1: Method for preparing CIGSe thin-film solar cells.

[0027] S1. Clean the soda-lime glass substrate and deposit a pure molybdenum electrode layer on the substrate using DC magnetron sputtering. Specifically, first deposit a 600 nm thick molybdenum layer under an Ar gas pressure of 2 Pa, and then deposit a 200 nm thick molybdenum layer under an Ar gas pressure of 0.5 Pa to obtain a molybdenum electrode with a total thickness of 0.8 μm.

[0028] S2. A low-temperature amorphous CIGSe layer was deposited on a molybdenum electrode layer using a copper indium gallium selenide (CIGSe) quaternary target via magnetron sputtering. The substrate temperature during fabrication was room temperature, and argon gas was introduced during fabrication at a flow rate of 10 sccm. The sputtering power density was controlled at 0.12 W / cm². 2 The sputtering pressure was 0.5 Pa, and the sputtering time was 150 s, resulting in an amorphous CIGSe layer with a thickness of 80 nm.

[0029] S3. The substrate temperature is raised to 350 °C, and a high-temperature crystalline CIGSe layer is further deposited using a copper indium gallium selenide (CIGSe) quaternary target via magnetron sputtering. During deposition, a mixture of hydrogen and argon gas is introduced, with an argon flow rate of 10 sccm and a hydrogen concentration (i.e., the hydrogen-to-argon flow rate ratio) of 3%. The sputtering power density is controlled at 2.4 W / cm². 2 The sputtering pressure was 0.8 Pa, and the sputtering time was controlled at 448 s to obtain a crystalline CIGSe layer with a thickness of 1990 nm.

[0030] S4. Transfer the sample with the deposited crystalline CIGSe layer to a sputtering chamber containing a copper indium gallium sulfide (CIGS) target, introduce argon gas, control the argon gas flow rate at 10 sccm, set the sputtering pressure to 0.5 Pa, and the sputtering power to 0.8 W / cm². 2 A copper indium gallium sulfide thin film with a thickness of 10 nm was obtained by sputtering for 10 s.

[0031] After sputtering, the sample was annealed in a selenium-free environment at 580 °C for 60 min in an annealing furnace to complete the preparation of a gradient CIGSe absorber layer with a total thickness of 2000 nm.

[0032] S5. Preparation of the buffer layer: The CdS buffer layer was prepared using a chemical water bath method. Cadmium acetate, sodium citrate, thiourea, and ammonia were mixed in a specific order and proportion. The thickness of the buffer layer was controlled by adjusting the temperature of the water bath and the immersion time of the absorbent layer in the solution. The thickness of the prepared CdS buffer layer was 50 nm.

[0033] S6. Preparation of the window layer: A 100 nm thick intrinsic ZnO layer was first sputtered onto the CdS buffer layer using magnetron sputtering, and then a 400 nm thick aluminum-doped zinc oxide (AZO) layer was sputtered.

[0034] S7. Fabrication of metal grid electrodes: Patterned nickel (Ni) and aluminum (Al) grid electrodes were fabricated using a mask via vacuum evaporation.

[0035] The CIGSe thin-film solar cell is obtained by following the above steps. Example 2

[0036] Compared with Example 1, in step S3 of this example, the hydrogen concentration is changed to 5%, while the rest is the same as in Example 1. Example 3

[0037] Compared with Example 1, in this example, the sputtering time is controlled to be 443 s in step S3 to obtain a crystalline CIGSe layer with a thickness of 1970 nm, and the sputtering time is controlled to be 30 s in step S4 to obtain a copper indium gallium sulfide thin film with a thickness of 30 nm. The rest are the same as in Example 1. Example 4

[0038] Compared with Example 1, in this example, the sputtering time is controlled to be 437 s in step S3 to obtain a crystalline CIGSe layer with a thickness of 1940 nm, and the sputtering time is controlled to be 60 s in step S4 to obtain a copper indium gallium sulfide thin film with a thickness of 60 nm. The rest are the same as in Example 1. Example 5

[0039] Compared with Example 1, in this example, the sputtering time is controlled to be 428 s in step S3 to obtain a crystalline CIGSe layer with a thickness of 1900 nm, and the sputtering time is controlled to be 100 s in step S4 to obtain a copper indium gallium sulfide thin film with a thickness of 100 nm. The rest are the same as in Example 1. Example 6

[0040] Compared with Example 1, in step S3 of this example, the hydrogen concentration is changed to 7%, and the rest is the same as in Example 1. Example 7

[0041] Compared with Example 1, in step S3 of this example, the hydrogen concentration is changed to 9%, and the rest is the same as in Example 1.

[0042] Comparative Example 1 S1. Clean the soda-lime glass substrate and deposit a pure molybdenum electrode layer on the substrate using DC magnetron sputtering. Specifically, first deposit a 600 nm thick molybdenum layer under an Ar gas pressure of 2 Pa, and then deposit a 200 nm thick molybdenum layer under an Ar gas pressure of 0.5 Pa to obtain a molybdenum electrode with a total thickness of 0.8 μm.

[0043] S2. A low-temperature amorphous CIGSe layer was deposited on a molybdenum electrode layer using a copper indium gallium selenide (CIGSe) quaternary target via magnetron sputtering. The substrate temperature during fabrication was room temperature, and argon gas was introduced during fabrication at a flow rate of 10 sccm. The sputtering power density was controlled at 0.12 W / cm². 2 The sputtering pressure was 0.5 Pa, and the sputtering time was 150 s, resulting in an amorphous CIGSe layer with a thickness of 80 nm.

[0044] S3. Raise the substrate temperature to 350 ℃, and further deposit a high-temperature crystalline CIGSe layer using a copper indium gallium selenide (CIGSe) quaternary target via magnetron sputtering. Argon gas is introduced during deposition, with the argon gas flow rate controlled at 10 sccm and the sputtering power density controlled at 2.4 W / cm². 2 The sputtering pressure was 0.8 Pa, and the sputtering time was controlled at 450 s to obtain a crystalline CIGSe layer with a thickness of 2000 nm.

[0045] After sputtering, the sample was annealed in a selenium-free environment at 580 °C for 60 min in an annealing furnace to complete the preparation of a CIGSe absorber layer with a thickness of 2000 nm.

[0046] S4. Preparation of the buffer layer: The CdS buffer layer was prepared using a chemical water bath method. Cadmium acetate, sodium citrate, thiourea, and ammonia were mixed in a specific order and proportion. The thickness of the buffer layer was controlled by adjusting the temperature of the water bath and the immersion time of the absorbent layer in the solution. The thickness of the prepared CdS buffer layer was 50 nm.

[0047] S5. Preparation of the window layer: A 100 nm thick intrinsic ZnO layer was first sputtered onto the CdS buffer layer using magnetron sputtering, and then a 400 nm thick aluminum-doped zinc oxide (AZO) layer was sputtered.

[0048] S6. Fabrication of metal grid electrodes: Patterned nickel (Ni) and aluminum (Al) grid electrodes were fabricated using a mask via vacuum evaporation.

[0049] The CIGSe thin-film solar cell is obtained by following the above steps.

[0050] Comparative Example 2 S1. Clean the soda-lime glass substrate and deposit a pure molybdenum electrode layer on the substrate using DC magnetron sputtering. Specifically, first deposit a 600 nm thick molybdenum layer under an Ar gas pressure of 2 Pa, and then deposit a 200 nm thick molybdenum layer under an Ar gas pressure of 0.5 Pa to obtain a molybdenum electrode with a total thickness of 0.8 μm.

[0051] S2. A low-temperature amorphous CIGSe layer was deposited on a molybdenum electrode layer using a copper indium gallium selenide (CIGSe) quaternary target via magnetron sputtering. The substrate temperature during fabrication was room temperature, and argon gas was introduced during fabrication at a flow rate of 10 sccm. The sputtering power density was controlled at 0.12 W / cm². 2 The sputtering pressure was 0.5 Pa, and the sputtering time was 150 s, resulting in an amorphous CIGSe layer with a thickness of 80 nm.

[0052] S3. Raise the substrate temperature to 350 ℃, and further deposit a high-temperature crystalline CIGSe layer using a copper indium gallium selenide (CIGSe) quaternary target via magnetron sputtering. Argon gas is introduced during deposition, with the argon gas flow rate controlled at 10 sccm and the sputtering power density controlled at 2.4 W / cm². 2 The sputtering pressure was 0.8 Pa, and the sputtering time was controlled at 448 s to obtain a crystalline CIGSe layer with a thickness of 1990 nm.

[0053] S4. Transfer the sample with the deposited crystalline CIGSe layer to a sputtering chamber containing a copper indium gallium sulfide (CIGS) target, introduce argon gas, control the argon gas flow rate at 10 sccm, set the sputtering pressure to 0.5 Pa, and the sputtering power to 0.8 W / cm². 2 A copper indium gallium sulfide thin film with a thickness of 10 nm was obtained by sputtering for 10 s.

[0054] After sputtering, the sample was annealed in a selenium-free environment at 580 °C for 60 min in an annealing furnace to complete the preparation of a gradient CIGSe absorber layer with a total thickness of 2000 nm.

[0055] S5. Preparation of the buffer layer: The CdS buffer layer was prepared using a chemical water bath method. Cadmium acetate, sodium citrate, thiourea, and ammonia were mixed in a specific order and proportion. The thickness of the buffer layer was controlled by adjusting the temperature of the water bath and the immersion time of the absorbent layer in the solution. The thickness of the prepared CdS buffer layer was 50 nm.

[0056] S6. Preparation of the window layer: A 100 nm thick intrinsic ZnO layer was first sputtered onto the CdS buffer layer using magnetron sputtering, and then a 400 nm thick aluminum-doped zinc oxide (AZO) layer was sputtered.

[0057] S7. Fabrication of metal grid electrodes: Patterned nickel (Ni) and aluminum (Al) grid electrodes were fabricated using a mask via vacuum evaporation.

[0058] The CIGSe thin-film solar cell is obtained by following the above steps.

[0059] Performance testing The microstructure and battery performance parameters of the samples prepared above were characterized, and the results are as follows: Figure 1 , Figure 2 , Figure 3 As shown in Tables 1 and 2.

[0060] Figure 1 These are SEM cross-sectional images of the CIGSe absorber layers prepared in Example 1, Comparative Example 1, and Comparative Example 2. Figure 2 The images show the XRD patterns of the CIGSe absorption layers prepared in Examples 1, 1, and 2, and the fitting results of the full width at half maximum (FWHM) of the corresponding (112) crystal plane diffraction peaks. Figure 1 and Figure 2 It can be seen that, compared with Comparative Example 1, after adding a copper indium gallium sulfide wide bandgap deposition layer to the absorption layer in Comparative Example 2, the grain size of the obtained CIGSe absorption layer is significantly larger, but the film still has pores; while in Example 1, after hydrogen plasma treatment, the grain size continues to increase and the pores disappear, and the (112) crystal plane diffraction peak of the sample increases and the half-peak width decreases.

[0061] Table 1 shows a comparison of the battery efficiency parameters for Examples 1, 3-5, and Comparative Example 1. As shown in Table 1, the device efficiency was highest in Example 3 when the copper indium gallium sulfide thin film thickness was 60 nm, reaching 16.80%.

[0062] Table 1 Performance parameters of CIGSe thin-film solar cells prepared in Examples 1, 3-5 and Comparative Example 1

[0063] Table 2 shows a comparison of battery efficiency parameters for Examples 1, 2, 6, and 7. As shown in Table 2, Example 2 achieved the highest efficiency of 18.81% when the hydrogen plasma treatment concentration was 5%. This is because the H plasma treatment reduced the density of bulk defects, which is beneficial for reducing bulk recombination and improving Vg. OC However, the H plasma concentration must be moderate; too high a concentration may introduce new defects.

[0064] Table 2 Performance parameters of CIGSe thin-film solar cells prepared in Examples 1-2 and 6-7

[0065] Figure 3 The figures show the XPS depth etching results of S elements in the samples of Example 2 and Example 2. As can be seen from the figures, a significantly high S content can be observed at the top of the absorption layer, indicating that the S content in the absorption layer is mainly concentrated on the surface of the absorption layer. The addition of hydrogen in Example 2 can effectively suppress the diffusion of S into the interior of the absorption layer.

Claims

1. A method for preparing a copper indium gallium selenide (CIGS) absorber layer, characterized in that, Includes the following steps: S1. Prepare a molybdenum electrode layer on the substrate; S2. An amorphous copper indium gallium selenide (CIGS) layer is deposited on a molybdenum electrode layer in an argon atmosphere using magnetron sputtering. S3. A crystalline copper indium gallium selenide (CIGS) precursor is deposited on an amorphous CIGS layer using magnetron sputtering in an argon and hydrogen plasma environment. Then, a copper indium gallium sulfide (CIGS) layer is deposited on the surface of the crystalline CIGS precursor using magnetron sputtering in an argon environment. Finally, a CIGS gradient absorption layer is obtained by high-temperature annealing.

2. The method for preparing the copper indium gallium selenide absorber layer according to claim 1, characterized in that, In step S3, the conditions for depositing the crystalline copper indium gallium selenide precursor by magnetron sputtering are as follows: vacuum chamber ambient pressure of 0.2 Pa-1.0 Pa, hydrogen concentration of 0-10%, and sputtering power of 0.1 W / cm². 2 -8 W / cm 2 The substrate temperature is 350℃-650℃.

3. The method for preparing the copper indium gallium selenide absorber layer according to claim 1, characterized in that, In step S3, the conditions for depositing a copper indium gallium sulfide layer using magnetron sputtering are: argon gas pressure in the vacuum chamber is 0.2 Pa–1.0 Pa, and sputtering power is 0.1 W / cm². 2 -8 W / cm 2 The substrate temperature is 350℃-650℃.

4. The method for preparing the copper indium gallium selenide absorber layer according to claim 1, characterized in that, In step S3, the thickness of the copper indium gallium sulfide layer is 0.3%-15% of the thickness of the copper indium gallium selenide gradient absorption layer.

5. The method for preparing the copper indium gallium selenide absorber layer according to claim 1, characterized in that, In step S3, the thickness of the copper indium gallium selenide gradient absorption layer is 1000 nm-3000 nm.

6. The method for preparing the copper indium gallium selenide absorber layer according to claim 1, characterized in that, In step S2, an amorphous copper indium gallium selenide layer with a thickness of 40 nm to 100 nm is deposited at room temperature.

7. A solar cell, characterized in that, sequentially include: Substrate, molybdenum electrode layer, copper indium gallium selenide absorber layer, buffer layer, window layer, metal gate electrode; The copper indium gallium selenide absorber layer is prepared by the method according to any one of claims 1 to 6.

8. The method for preparing the solar cell according to claim 7, characterized in that, Includes the following steps: S1. Prepare a molybdenum electrode layer on the substrate; S2. An amorphous copper indium gallium selenide (CIGS) layer is deposited on a molybdenum electrode layer in an argon atmosphere using magnetron sputtering. S3. A crystalline copper indium gallium selenide precursor is deposited on an amorphous copper indium gallium selenide layer by magnetron sputtering in an argon and hydrogen plasma environment. Then, a copper indium gallium sulfide layer is deposited on the surface of the crystalline copper indium gallium selenide precursor by magnetron sputtering in an argon environment. Finally, a copper indium gallium selenide gradient absorption layer is obtained by high-temperature annealing. S4. A buffer layer is prepared on the copper indium gallium selenide gradient absorption layer by chemical bath method or magnetron sputtering method. S5. A high-resistivity layer is prepared on the buffer layer by magnetron sputtering, and then a transparent conductive layer is prepared on the high-resistivity layer. S6. Patterned metal grid electrodes are prepared by vacuum evaporation.

9. The method for preparing a solar cell according to claim 8, characterized in that, In step S1, the substrate is a soda-lime glass sheet. Step S1 is as follows: First, a layer of molybdenum with a thickness of 400 nm-700 nm is deposited under Ar gas pressure of 1.5~3 Pa. Then, a layer of molybdenum with a thickness of 100 nm-400 nm is deposited under Ar gas pressure of 0.2~1 Pa.

10. The method for preparing a solar cell according to claim 8, characterized in that, In step S1, the substrate is stainless steel or polyimide sheet; and before depositing the molybdenum electrode layer on the substrate, a barrier layer is first deposited on the substrate, and then a molybdenum layer doped with sodium metal is deposited on the barrier layer; then the molybdenum electrode layer is deposited on the molybdenum layer doped with sodium metal.

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