Method for preparing copper-zinc-tin-sulfur thin film solar cell through full-magnetron sputtering

Abstract

The invention belongs to the technical field of photoelectric material new energy, and particularly relates to a method for preparing a CZTS thin film solar cell through full magnetron sputtering, and the method comprises the steps: preparing a Cu-Zn-Sn metal prefabricated layer thin film through magnetron sputtering, and then preparing a CZTS thin film absorption layer through high-temperature vulcanization; preparing a CdS buffer layer film with the thickness of 50nm above the absorption layer through magnetron sputtering, and carrying out heterojunction annealing treatment on the device; and then preparing intrinsic zinc oxide and indium-doped tin oxide as a window layer of the device through magnetron sputtering, and after the window layer of the device is prepared, preparing an Ag top electrode by adopting electron beam evaporation. The CdS thin film is prepared through the magnetron sputtering method, so that a waste solution containing a Cd element can be avoided, it can be ensured that the chemical component proportion of the CdS buffer layer thin film is stable, most importantly, the whole preparation process of the CZTS thin film battery is carried out in a vacuum environment, the pollution probability of foreign impurities to the thin film is very small, repeatability is high, and the CZTS thin film battery is suitable for large-scale production. And the method is very suitable for large-scale industrial production.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of photoelectric materials and new energy, and relates to a method for preparing a thin-film solar cell. BACKGROUND

[0002] Although copper indium gallium selenide (CIGS) and cadmium telluride (CdTe) solar cells have high photoelectric conversion efficiency and are commercialized, indium and gallium in the CIGS thin-film cell are rare elements with low content in nature, so the prices of the elements are high and the large-scale production of the elements is limited. In addition, Cd in the CdTe is a heavy metal element, which can cause serious damage to the environment. Therefore, quaternary compound semiconductor materials: Cu2ZnSnS4 (CZTS), Cu2ZnSnSe4 (CZTSe) and Cu2ZnSn(S 1-x Se x )4 based on I2-II-IV-VI4 have the advantages of rich reserves of constituent elements in nature, environmental friendliness, large-scale production demand and low production cost. In addition, CZTS is a direct band gap P-type semiconductor with a high absorption coefficient (10 4 cm -1 ~10 5 cm -1 ), a band gap width of 1.5 eV close to the ideal band gap width 1.34 eV of a single-junction solar cell, and a theoretical efficiency of 32.2 %, so it is a thin-film solar cell with broad development prospects.

[0003] At present, the mainstream method for preparing a CZTS thin-film solar cell buffer layer is a chemical water bath method. However, the chemical water bath method produces a large amount of waste liquid containing Cd elements in the process of preparing a CdS thin film, and improper treatment can cause environmental pollution. In addition, the volatilization of ammonia in the deposition solution also changes the chemical component ratio of the solution, thereby affecting the component ratio of the CdS buffer layer and the film quality. In addition, the deposition thickness of the CdS thin film prepared by the chemical water bath method cannot be accurately controlled, and the repeatability is poor.

[0004] Therefore, how to provide a method for preparing a CZTS thin-film solar cell with high repeatability, suitable for large-scale industrial production and excellent performance is a technical problem to be solved by those skilled in the art. SUMMARY

[0005] Therefore, the application discloses a method for preparing a CZTS thin-film solar cell by full magnetron sputtering.

[0006] It should be noted that the present application prepares the absorption layer and the buffer layer of the CZTS thin film cell by the magnetron sputtering method to replace the current mainstream chemical water bath method (CBD) for preparing the CZTS and CdS thin film, and finally realizes the magnetron sputtering method for preparing the complete CZTS thin film cell. In the process of preparing the device by the method, not only the waste liquid polluting the environment is not generated, but also the material is saved, the deposition thickness of the CZTS and CdS thin film is accurately controlled, the experiment has high repeatability, and the entire device is prepared in a vacuum environment, so that the thin film is prevented from being polluted by the outside world, and the purity of each layer of the thin film is increased.

[0007] In order to achieve the above object, the present application adopts the following technical scheme: A method for preparing a copper-zinc-tin-sulfur thin film solar cell by full magnetron sputtering, which is implemented in the following steps: (1) Substrate cleaning: the soda-lime glass is sequentially cleaned by ultrasonic cleaning with acetone, alcohol and deionized water, and dried with nitrogen, and is ready for use; (2) The cleaned soda-lime glass is placed in a magnetron sputtering chamber and heated to 100-150 DEG C and baked for 30-60 min, and then a 1 micron molybdenum back electrode thin film is deposited on the soda-lime glass, and then heated to 400 DEG C and baked for 30 min, so that more sodium atoms diffuse into the molybdenum layer, which is beneficial to the growth of CZTS crystal grains later; (3) Preparation of Cu-Zn-Sn metal pre-layer thin film: Zn, Sn and Cu layers are sputtered in the order of Zn-Sn-Cu-Sn-Cu by a magnetron sputtering device to deposit high-purity Zn, Sn and Cu targets on the molybdenum layer, and the thickness of the pre-layer thin film is 750 nm. After sputtering, the Cu-Zn-Sn metal pre-layer thin film is obtained. The sputtering pressure of the high-purity metal Zn, Sn and Cu targets is 0.5 Pa, the sputtering power of the Cu target is 100 W, and the sputtering power of the Sn and Zn targets is 50 W; (4) Preparation of CZTS film absorption layer: the prepared Cu-Zn-Sn metal pre-layer thin film is placed in a graphite boat and sulfur powder and sulfur particles are added, 15 mg of sulfur powder and 40 mg of sulfur particles are added for each Cu-Zn-Sn metal pre-layer, and finally 1.25 mg of stannous sulfide (SnS) is added as a Sn source, the graphite boat is placed in a tube furnace, nitrogen is introduced to remove air in the tube, and the graphite boat is placed in a tube furnace under nitrogen protection, and is treated at 585 DEG C for 22 min, and is naturally cooled to obtain a copper-zinc-tin-sulfur absorption layer thin film; (5) A CdS buffer layer was prepared on the CZTS absorber layer film by magnetron sputtering. The buffer layer was deposited with a thickness of 50 nm. After sputtering, the device was placed in a high-temperature annealing furnace. Under a nitrogen atmosphere, the CZTS / CdS heterojunction was annealed at a temperature of 280 °C for 25 min. Then, the annealed CZTS / CdS heterojunction sample was sent into the sputtering chamber to prepare the window layer of the CZTS thin film battery by magnetron sputtering. i-ZnO and ITO were sputtered in sequence to prepare the window layer. The power of i-ZnO sputtering was 35 W, the sputtering pressure was 0.3 Pa, and the i-ZnO deposition thickness was 50 nm. The power of ITO sputtering was 100 W, the sputtering pressure was 0.5 Pa, and the ITO deposition thickness was 250 nm. (6) The top electrode of the CZTS thin film battery was prepared by electron beam evaporation. The Ag top electrode was formed by hot evaporation of high-purity Ag particles with a thickness of 200 nm. After the evaporation was completed, the battery device was placed in a rapid annealing furnace and annealed at 250 °C for 20 min.

[0008] It should be noted that this invention prepares the CdS buffer layer via magnetron sputtering. With increasing sputtering power (30W-80W), the carrier concentration in the n-type CdS film significantly increases, leading to an increase in the short-circuit current density of the battery to 25.21 mA / cm². -2 When the sputtering power is too low (30W), the CdS buffer layer will adhere unevenly to the absorber layer, while when the sputtering power is too high (80W), it will damage the surface of the CZTS absorber layer. Therefore, the CZTS thin-film solar cell constructed with a CdS buffer layer at a sputtering power of 50W under this invention has the best characteristics, with a corresponding photoelectric power conversion efficiency of 9.88%, which is higher than the efficiency of CZTS thin-film solar cells constructed with CdS thin films using the traditional CBD method (8.7%).

[0009] Compared with the prior art, the beneficial effects of the present invention are: This invention prepares a Cu-Zn-Sn metal pre-layer thin film by magnetron sputtering, followed by high-temperature sulfurization to prepare a CZTS thin film absorption layer. A 50 nm thick CdS buffer layer thin film is prepared on top of the absorption layer by magnetron sputtering, and the device is subjected to heterojunction annealing. Subsequently, intrinsic zinc oxide and indium-doped tin oxide are prepared as window layers of the device by magnetron sputtering. After the window layer of the device is prepared, an Ag top electrode is prepared by electron beam evaporation.

[0010] This invention uses magnetron sputtering to prepare CdS thin films, which avoids the generation of waste solutions containing Cd elements and ensures the stability of the chemical composition ratio of the CdS buffer layer film. Most importantly, the entire CZTS thin film battery preparation process is carried out in a vacuum environment, so the probability of foreign impurities contaminating the film is very small, and the repeatability is high, making it very suitable for large-scale industrial production. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0012] Figure 1 The images show the XRD patterns of the copper-zinc-tin-sulfur thin film absorber layers prepared in Examples 1, 2, and 3, and Comparative Example 1.

[0013] Figure 2 Raman diagrams of the copper-zinc-tin-sulfur thin film absorber layers prepared in Examples 1, 2, and 3, and Comparative Example 1.

[0014] Figure 3 SEM images of the copper-zinc-tin-sulfur thin film absorber layers prepared in Examples 1, 2, and 3 and Comparative Example 1.

[0015] Figure 4 The images show the XRD patterns of the CdS thin films prepared in Examples 1, 2, and 3, and Comparative Example 1.

[0016] Figure 5 The UV-Vis-NIR diffuse reflectance absorption spectra of the CdS thin films prepared in Examples 1, 2, and 3 and Comparative Example 1 are shown.

[0017] Figure 6 SEM images of the CdS films prepared in Examples 1, 2 and 3 and Comparative Example 1.

[0018] Figure 7 The complete battery efficiency IV plots and EQEs prepared in Examples 1, 2, and 3 and Comparative Example 1 are shown. Detailed Implementation

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] The term "embodiment" used herein, as an example, is not necessarily to be construed as superior to or better than other embodiments. Performance testing in the embodiments of this application, unless otherwise specified, employs conventional testing methods in the art. It should be understood that the terminology used in this application is merely for describing particular implementations and is not intended to limit the scope of this disclosure.

[0021] Unless otherwise stated, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; other experimental methods and technical means not specifically mentioned herein refer to experimental methods and technical means commonly used by one of ordinary skill in the art.

[0022] To better illustrate the content of this application, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that this application can be implemented even without certain specific details. In the embodiments, some methods, means, instruments, and devices well-known to those skilled in the art are not described in detail in order to highlight the main points of this application.

[0023] Without conflict, the technical features disclosed in the embodiments of this application can be combined arbitrarily, and the resulting technical solution belongs to the content disclosed in the embodiments of this application.

[0024] This invention discloses a method for preparing copper-zinc-tin-sulfur thin-film solar cells by all-magnetron sputtering.

[0025] To better understand the present invention, the following embodiments are provided for further detailed description of the present invention, but they should not be construed as limiting the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above-described invention are also considered to fall within the protection scope of the present invention.

[0026] Example 1 (1) Substrate cleaning: Sodium-calcium glass is ultrasonically cleaned in sequence with acetone, alcohol and deionized water, and then dried with nitrogen gas for later use; (2) The cleaned soda-lime glass was placed in a magnetron sputtering system and heated to 150°C for 30 minutes. A molybdenum target with dimensions of 76.2 mm * 3 mm was used as the sputtering target for DC sputtering. The background vacuum was 5.0 * 10 -4 Pa, substrate temperature 160℃, ignition pressure 1.6Pa, power 150W, sputtering for 15min at argon pressure 1.6Pa, then sputtering for 105min at argon pressure 0.3Pa, and then obtaining a 1μm molybdenum back electrode film on soda-lime glass according to the above requirements, and then heating to 400℃ for 30min. (3) Preparation of Cu-Zn-Sn metal pre-layer: High-purity Zn, Sn and Cu targets were sputtered by magnetron sputtering equipment and deposited on the molybdenum layer in the order of Zn-Sn-Cu-Sn-Cu. The sputtering power of Zn and Sn was 50W and the sputtering power of Cu was 100W. The sputtering pressure was 0.5Pa and the sputtering thickness of the pre-layer was 750nm. After sputtering, Cu-Zn-Sn precursor film can be obtained. (4) Preparation of copper-zinc-tin-sulfur absorber film: The prepared Cu-Zn-Sn pre-coated film was placed in a graphite boat and sulfur powder and sulfur particles were added. Each pre-coated film was added with 15 mg of sulfur powder and 40 mg of sulfur particles. Finally, 1.25 mg of tin sulfide (SnS) was added as a supplementary Sn source. After the graphite boat was placed in a tube furnace, nitrogen gas was introduced to remove the air in the tube. Under nitrogen protection, the film was sulfurized at 585℃ for 22 min. After natural cooling, the copper-zinc-tin-sulfur absorber film was obtained. (5) A CdS buffer layer was prepared on the CZTS absorber layer film by magnetron sputtering. The sputtering power of the buffer layer was 30W, the sputtering pressure was 0.5Pa, and the deposition thickness was 50nm. After sputtering, the sample was placed in a high-temperature annealing furnace to anneal the CZTS / CdS heterojunction. Then, intrinsic zinc oxide (i-ZnO) and indium-doped tin oxide (ITO) were prepared as the window layer of the device by magnetron sputtering. The sputtering power of i-ZnO was 35W, the sputtering pressure was 0.3Pa, and the i-ZnO deposition thickness was 50nm. The sputtering power of ITO was 100W, the sputtering pressure was 0.5Pa, and the ITO deposition thickness was 250nm. (6) The top electrode of the CZTS thin film battery was prepared by electron beam evaporation. The Ag top electrode was formed by evaporating high-purity Ag particles with a thickness of 200 nm. After the evaporation was completed, the complete CZTS thin film battery was placed in a rapid annealing furnace and annealed at 250 °C for 20 min.

[0027] Example 2 (1) Substrate cleaning: Sodium-calcium glass is ultrasonically cleaned in sequence with acetone, alcohol and deionized water, and then dried with nitrogen gas for later use; (2) The cleaned soda-lime glass was placed in a magnetron sputtering system and heated to 150°C for 30 minutes. A molybdenum target with dimensions of 76.2 mm * 3 mm was used as the sputtering target for DC sputtering. The background vacuum was 5.0 * 10 -4 The substrate temperature was 160℃, the start-up pressure was 1.6pa, the power was 150W, and sputtering was performed at argon pressure of 1.6pa for 15min. Then, the argon pressure was adjusted to 0.3pa and sputtering was performed for 105min. Following the above requirements, a 1μm molybdenum back electrode film was obtained on soda-lime glass. Then, the temperature was raised to 400℃ and baked for 30min. (3) Preparation of Cu-Zn-Sn metal pre-layer thin film: High-purity Zn, Sn and Cu targets were sputtered by magnetron sputtering equipment and deposited on the molybdenum layer in the order of Zn-Sn-Cu-Sn-Cu. The sputtering power of Zn and Sn was 50W and the sputtering power of Cu was 100W. The sputtering pressure was 0.5Pa and the film sputtering thickness was 750nm. After sputtering, Cu-Zn-Sn metal pre-layer thin film can be obtained. (4) Preparation of copper-zinc-tin-sulfur absorber film: The prepared Cu-Zn-Sn metal pre-layer film was placed in a graphite boat and sulfur powder and sulfur particles were added. Each pre-layer was added with 15mg of sulfur powder and 40mg of sulfur particles. Finally, 1.25mg of tin sulfide (SnS) was added as a supplementary Sn source. After the graphite boat was placed in a tube furnace, nitrogen gas was introduced to remove the air in the tube. Under nitrogen protection, the film was sulfurized at 585℃ for 22min. After natural cooling, the copper-zinc-tin-sulfur absorber film was obtained. (5) A CdS buffer layer was prepared on the CZTS absorber layer film by magnetron sputtering. The sputtering power of the buffer layer was 50W, the sputtering pressure was 0.5Pa, and the deposition thickness was 50nm. After sputtering, the sample was placed in a high-temperature annealing furnace to anneal the CZTS / CdS heterojunction. Then, intrinsic zinc oxide (i-ZnO) and indium tin oxide (ITO) were prepared as window layers of the battery by magnetron sputtering. The sputtering power of i-ZnO was 35W, the sputtering pressure was 0.3Pa, and the i-ZnO deposition thickness was 50nm. The sputtering power of ITO was 100W, the sputtering pressure was 0.5Pa, and the ITO deposition thickness was 250nm. (6) The top electrode of the CZTS thin film battery was prepared by electron beam evaporation. The Ag top electrode was formed by evaporating high-purity Ag particles with a thickness of 200 nm. After the evaporation was completed, the complete battery was placed in a rapid annealing furnace and annealed at 250 °C for 20 min.

[0028] Example 3 (1) Substrate cleaning: Sodium-calcium glass is ultrasonically cleaned in sequence with acetone, alcohol and deionized water, and then dried with nitrogen gas for later use; (2) The cleaned soda-lime glass was placed in a magnetron sputtering system and heated to 150°C for 30 minutes. A molybdenum target with dimensions of 76.2 mm * 3 mm was used as the sputtering target for DC sputtering. The background vacuum was 5.0 * 10 -4 The substrate temperature was 160℃, the start-up pressure was 1.6pa, the power was 150W, and sputtering was performed at argon pressure of 1.6pa for 15min. Then, the argon pressure was adjusted to 0.3pa and sputtering was performed for 105min. Following the above requirements, a 1μm molybdenum back electrode film was obtained on soda-lime glass. Then, the temperature was raised to 400℃ and baked for 30min. (3) Preparation of Cu-Zn-Sn metal pre-layer thin film: High-purity Zn, Sn and Cu targets were sputtered by magnetron sputtering equipment and deposited on the molybdenum layer in the order of Zn-Sn-Cu-Sn-Cu. The sputtering power of Zn and Sn was 50W, the sputtering power of Cu was 100W, the sputtering pressure was 0.5Pa, and the film sputtering thickness was 750nm. After sputtering, Cu-Zn-Sn metal pre-layer thin film can be obtained. (4) Preparation of copper-zinc-tin-sulfur absorber film: The prepared Cu-Zn-Sn metal pre-layer film was placed in a graphite boat and sulfur powder and sulfur particles were added. Each pre-layer was added with 15mg of sulfur powder and 40mg of sulfur particles. Finally, 1.25mg of tin sulfide (SnS) was added as a supplementary Sn source. After the graphite boat was placed in a tube furnace, nitrogen gas was introduced to remove the air in the tube. Under nitrogen protection, the copper-zinc-tin-sulfur absorber film was obtained after high temperature sulfurization treatment at 585℃ for 22min and natural cooling. (5) A CdS buffer layer was prepared on the CZTS absorber layer film by magnetron sputtering. The sputtering power of the buffer layer was 80W, the sputtering pressure was 0.5Pa, and the deposition thickness was 50nm. After sputtering, the device was placed in a high-temperature annealing furnace to anneal the CZTS / CdS heterojunction. Then, intrinsic zinc oxide (i-ZnO) and indium-doped tin oxide (ITO) were prepared as the window layer of the device by magnetron sputtering. The sputtering power of i-ZnO was 35W, the sputtering pressure was 0.3Pa, and the i-ZnO deposition thickness was 50nm. The sputtering power of ITO was 100W, the sputtering pressure was 0.5Pa, and the ITO deposition thickness was 250nm. (6) The top electrode of the CZTS thin film battery was prepared by electron beam evaporation. The Ag top electrode was formed by evaporating high-purity Ag particles with a thickness of 200 nm. After the evaporation was completed, the device was placed in a rapid annealing furnace and annealed at 250 °C for 20 min.

[0029] To further demonstrate the beneficial effects of the present invention and to better understand it, the technical features disclosed in the present invention are further illustrated by the following comparative examples, but these should not be construed as limiting the present invention. Other improvements made by those skilled in the art based on the above description of the invention, without inventive effort, are also considered to fall within the protection scope of the present invention.

[0030] Comparative Example 1 (1) Substrate cleaning: Sodium-calcium glass is ultrasonically cleaned in sequence with acetone, alcohol and deionized water, and then dried with nitrogen gas for later use; (2) The cleaned soda-lime glass was placed in a magnetron sputtering system and heated to 150°C for 30 minutes. A molybdenum target with dimensions of 76.2 mm * 3 mm was used as the sputtering target for DC sputtering. The background vacuum was 5.0 * 10 -4The substrate temperature was 160℃, the start-up pressure was 1.6pa, the power was 150W, and sputtering was performed at argon pressure of 1.6pa for 15min. Then, the argon pressure was adjusted to 0.3pa and sputtering was performed for 105min. Following the above requirements, a 1μm molybdenum back electrode film was obtained on soda-lime glass. Then, the temperature was raised to 400℃ and baked for 30min. (3) Preparation of Cu-Zn-Sn metal pre-layer thin film: High-purity Zn, Sn and Cu targets were sputtered by magnetron sputtering equipment and deposited on molybdenum layer in the order of Zn-Sn-Cu-Sn-Cu. The sputtering power of Zn and Sn was 50W and the sputtering power of Cu was 100W. The sputtering pressure was 0.5Pa and the film sputtering thickness was 750nm. After sputtering, Cu-Zn-Sn precursor thin film can be obtained. (4) Preparation of copper-zinc-tin-sulfur absorber film: The prepared Cu-Zn-Sn pre-coated film was placed in a graphite boat and sulfur powder and sulfur particles were added. Each pre-coated film was added with 15 mg of sulfur powder and 40 mg of sulfur particles. Finally, 1.25 mg of tin sulfide (SnS) was added as a supplementary Sn source. After the graphite boat was placed in a tube furnace, nitrogen gas was introduced to remove the air in the tube. Under nitrogen protection, the film was sulfurized at 585℃ for 22 min. After natural cooling, the copper-zinc-tin-sulfur absorber film was obtained. (5) A CdS buffer layer was prepared on the CZTS absorber layer film by conventional chemical bath method (CBD) with a deposition time of 8 minutes and 30 seconds and a deposition thickness of 50 nm. After deposition, the sample was placed in a high-temperature annealing furnace to anneal the CZTS / CdS heterojunction. Then, intrinsic zinc oxide (i-ZnO) and indium-doped tin oxide (ITO) were prepared as window layers of the battery by magnetron sputtering. The sputtering power of i-ZnO was 35 W, the sputtering pressure was 0.3 Pa, and the i-ZnO deposition thickness was 50 nm. The sputtering power of ITO was 100 W, the sputtering pressure was 0.5 Pa, and the ITO deposition thickness was 250 nm. (6) The top electrode of the CZTS thin film battery was prepared by electron beam evaporation. The Ag top electrode was formed by evaporating high-purity Ag particles with a thickness of 200 nm. After the evaporation was completed, the entire device was placed in a rapid annealing furnace and annealed at 250 °C for 20 min.

[0031] Table 1 shows the parameters of the complete battery devices prepared in Examples 1, 2, and 3, as well as Comparative Example 1.

[0032] As shown in Table 1, the short-circuit current density and fill factor of Example 2 were significantly improved, achieving a maximum conversion efficiency of 9.88%, indicating that a high-efficiency device can be fabricated with a sputtering power of 50W. Example 1 had a lower short-circuit current density because the sputtering power of the thin film was only 30W, resulting in a low deposition rate and an inability to form a uniform and dense thin film covering the surface of the absorption layer. Consequently, an unevenly distributed built-in electric field and an uneven CZTS / CdS interface were formed inside the device. This hindered the collection of photogenerated carriers by the built-in electric field and increased recombination in the space charge region, limiting the improvement of the short-circuit current density and fill factor, resulting in an efficiency of only 8.40% for the device. In Example 3, the open-circuit voltage was improved, but the short-circuit current density and fill factor were not significantly improved. This is because high sputtering power increases the energy loss of sputtered particles, which is not conducive to the formation of a smooth film surface. A rough surface increases light scattering, and the large number of grain boundaries on the film surface increases the probability of recombination during carrier transport. These defects limit the improvement of the device's short-circuit current density and fill factor, resulting in a final efficiency of only 8.62%. Comparative Example 1 is a sample prepared by a chemical bath method. This deposition method is relatively mild, and the CZTS absorber layer as the substrate is not damaged by sputtering during CdS deposition. However, the deposition effect is easily affected by solution molecular dynamics and thermodynamics, resulting in uneven CdS grain distribution and the generation of polluting waste liquid. The efficiency of this sample reached 8.70%.

[0033] Figure 1 The images show the XRD diffraction pattern of the CZTS thin film and a magnified view of the CZTS thin film in the (112) crystal orientation, respectively. The test results show that the CZTS phase was formed in all four CZTS absorber film samples, and no other secondary phases were observed. Figure 1 As shown in the magnified view of the main peak of the crystal orientation in Figure (112) on the right, the crystal quality and phase purity of the sample are both high.

[0034] Figure 2 These are the Raman spectra of the CZTS absorber layer films. In the Raman tests, all four samples showed the dominant Raman peak at 253 cm⁻¹, characteristic of CZTS. -1 287cm -1 338cm -1 and 365cm -1 The Raman peaks associated with ZnS and Cu2SnS3 were not observed; therefore, the absorber film prepared in this experiment has good crystal quality, smooth surface morphology and no obvious secondary phase.

[0035] Figure 3 The image shows the surface morphology of the CZTS absorber layer. The test results indicate that the four CZTS absorber layer samples have compact and orderly grain arrangement, with no other obvious secondary phases present and a small number of grain boundaries.

[0036] Figure 4 This is the XRD pattern after CdS film deposition. The XRD results show that all four samples exhibited CdS diffraction peaks with diffraction angles of 26.4° and 43.9°, corresponding to the (111) and (220) main peaks of CdS. The (111) diffraction peak intensity of sample 1 was weaker, indicating poor crystal quality. Therefore, a lower sputtering pressure is not conducive to growing high-quality crystals, as it reduces the argon ions required for sputtering, thus decreasing the deposition rate and the growth quality of CdS grains. The (111) diffraction peak intensity of samples 2 and 3 increased, indicating... The crystallinity of the thin film increased with increasing sputtering pressure. However, the full width at half maximum (FWHM) of the sample in Example 2 was narrower than that in Example 3, indicating that the crystal quality and crystallinity of Sample 2 were superior to those of Sample 3. This suggests that higher sputtering pressure can actually reduce the crystallinity of the film. This is because high sputtering pressure causes CdS particles to collide during sputtering, reducing their migration ability on the substrate. Consequently, CdS grains are difficult to grow orderly on the substrate, thus reducing the crystallinity of the film. Furthermore, low migration also increases the surface roughness of the film, thereby reducing the overall quality of the film. The crystallinity of the sample film in Comparative Example 1 was between that of Examples 2 and 3, indicating that the film prepared by the chemical bath method had relatively better crystallinity. Figure 6 The morphology images show that the CdS grains are unevenly distributed on the substrate and overlap, which is detrimental to the collection and transport of photogenerated carriers and the absorption of short-wavelength photons during device operation. Therefore, magnetron sputtering can also prepare CdS thin films with better crystallinity and higher crystallinity.

[0037] Figure 5 The image shows the UVS characterization of the CdS thin film. The test results show that the sample of Example 2, prepared by sputtering at 50W, has a higher light absorption capacity within the absorbable wavelength range than Comparative Example 1. This indicates that the CdS thin film prepared by magnetron sputtering has a higher light absorption capacity than the CdS thin film prepared by the chemical water bath method. The thin films prepared under 30W and 80W conditions have lower photon absorption capacity than Comparative Example 1, indicating that the CdS thin film prepared under non-ideal sputtering power has lower light absorption capacity than the chemical water bath method. This is because lower sputtering power reduces the CdS deposition rate, resulting in incomplete CdS coverage of the substrate film surface, thus forming larger gaps and weakening the film's light absorption capacity. Higher sputtering power, on the other hand, is not conducive to the formation of high-quality CdS crystals. Therefore, both high and low sputtering power are unfavorable for preparing thin films with high light absorption performance.

[0038] Figure 6The image shows the surface morphology of the CdS thin film. Although the surface morphology of Example 1 (30W) is similar to that of Comparative Example 1 (CBD), characterized by relatively disordered cadmium sulfide grain growth and partial grain coverage, the surface coverage of the film in Comparative Example 1 is worse and the grains are smaller. This is likely due to the fluctuation in the cadmium sulfide deposition rate caused by the rotor rotation within the reaction beaker in Comparative Example 1. Fluctuations in rotor speed cause changes in the deposition rate, resulting in uneven distribution of cadmium sulfide on the substrate. Furthermore, fluctuations in rotor speed disrupt the uniformity of solute distribution in the solution, further leading to uneven cadmium sulfide deposition and overlapping cadmium sulfide grains. However, when the sputtering power is increased from 30W to 50W, the cadmium sulfide film exhibits a denser, flatter surface and larger grains. This is likely because sputtering power is positively correlated with the ionization saturation of argon ions: the higher the power, the greater the degree of ionization. Since the higher power of 80W caused damage to the film surface, more voids and gaps were obviously observed in Example 3. Therefore, the CdS buffer layer prepared by using 50W sputtering power showed a superior film surface morphology.

[0039] Figure 7 These are the JV curve and EQE test curve of the complete CZTS thin-film battery, respectively. The electrical parameters in the JV curve on the left correspond to η (%) in Table 1. V oc (V) and J sc (mA / cm 2 As shown in the EQE test spectrum on the right, the sample of Example 2 prepared with a sputtering power of 50W exhibits the highest photoelectric response in the 550nm wavelength range, indicating that the CdS buffer layer film prepared with this sputtering power has the best photoelectric performance. A higher response in the short wavelength range can improve the short-circuit current density of the device, which is consistent with the results shown in Table 1 above. When the sputtering power is 80W, the response in the corresponding short wavelength range is weakened, indicating that higher sputtering power is not conducive to forming CdS buffer layer films with superior crystal quality. The buffer layer films prepared by the chemical bath method have very low photoelectric responses in the short wavelength range, indicating that although the films prepared by the chemical bath method do not suffer from sputtering damage, the solution flow has a significant impact on film deposition. Therefore, the CdS buffer layer prepared using a sputtering power of 50W exhibits better photoelectric conversion and absorption capabilities.

[0040] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for fabricating a copper zinc tin sulfide thin film solar cell by full magnetron sputtering, characterized in that, The CZTS thin film absorption layer and CdS buffer layer are prepared by magnetron sputtering, and the specific preparation steps are as follows: 1) Substrate cleaning: the soda lime glass is sequentially cleaned by ultrasonic cleaning with acetone, alcohol and deionized water, and dried with nitrogen, ready for use; 2) A molybdenum layer is deposited on the soda lime glass by magnetron sputtering of a high-purity molybdenum target as the back electrode of the CZTS thin film solar cell, and then baked to allow more sodium atoms in the soda lime glass to diffuse into the molybdenum layer; 3) Preparation of Cu-Zn-Sn metal preformed layer film: high-purity metal Zn, Sn and Cu targets are sputtered by magnetron sputtering equipment, and sputtered in the order of Zn-Sn-Cu-Sn-Cu on the molybdenum layer, and the Cu-Zn-Sn metal preformed layer film is obtained after sputtering; 4) Preparation of copper zinc tin sulfide thin film absorption layer: the prepared Cu-Zn-Sn metal preformed layer film is placed in a graphite boat and sulfur powder and sulfur particles are added, and stannous sulfide is added as a supplemental Sn source, then the graphite boat is placed in a tube furnace and nitrogen is introduced to remove air in the tube, and then high-temperature sulfidation treatment is carried out under nitrogen protection, and the CZTS absorption layer film is obtained after natural cooling; 5) CdS buffer layer is prepared on the CZTS absorption layer film by magnetron sputtering method, and after sputtering, the device is placed in an annealing furnace for CTS / CdS heterojunction annealing treatment under nitrogen atmosphere; Then the annealed CTS / CdS heterojunction sample is sent into the sputtering cavity to prepare the window layer of the CZTS thin film battery by magnetron sputtering method, and the window layer is prepared by sputtering i-ZnO and ITO in turn; 6) The top electrode of the CZTS thin film battery is prepared by electron beam evaporation method, and the Ag top electrode with a thickness of 200 nm is formed by thermal evaporation of high-purity Ag particles, and the CZTS thin film battery is annealed after evaporation is completed.

2. The method for preparing copper zinc tin sulfide thin film solar cell by full magnetron sputtering according to claim 1, wherein, The Cu-Zn-Sn metal preformed layer film is deposited by multi-period sputtering in the order of Zn / Sn / Cu / Sn / Cu, and the total sputtering thickness is 750 nm. The sputtering pressure of high-purity metal Zn, Sn and Cu targets is 0.5 Pa, the sputtering power of Cu target is 100 W, and the sputtering power of Sn and Zn targets is 50 W.

3. The method for preparing copper zinc tin sulfide thin film solar cell by full magnetron sputtering according to claim 1, wherein, The thickness of the molybdenum layer is 1 μm, and after the molybdenum layer is sputtered, the molybdenum layer is heated to 400℃ and baked for 30 min.

4. The method for preparing copper zinc tin sulfide thin film solar cell by full magnetron sputtering according to claim 1, wherein, Each Cu-Zn-Sn preformed layer sulfidation requires the addition of 15 mg of sulfur powder and 40 mg of sulfur particles as a sulfur source, and 1.25 mg of stannous sulfide as a supplemental tin source.

5. The method for fabricating copper zinc tin sulfide thin film solar cell by full magnetron sputtering according to claim 1, wherein, In step 4), the high-temperature sulfidation treatment temperature is 585℃, and the time is 22 min.

6. The method for fabricating copper zinc tin sulfide thin film solar cell by full magnetron sputtering according to claim 1, wherein, In step 5), the CdS buffer layer deposition thickness is 50 nm, the annealing temperature is 280℃, and the annealing time is 25 min.

7. The method for preparing copper zinc tin sulfide thin film solar cell by full magnetron sputtering according to claim 1 or 6, characterized in that, The sputtering power of i-ZnO is 35 W, the sputtering pressure is 0.3 Pa, and the i-ZnO deposition thickness is 50 nm; the sputtering power of ITO is 100 W, the sputtering pressure is 0.5 Pa, and the ITO deposition thickness is 250 nm.

8. The method for fabricating copper zinc tin sulfide thin film solar cell by full magnetron sputtering according to claim 1, wherein, In step 6), the annealing temperature is 250℃, and the time is 20 min.

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