Gold-silver alloy nanoparticle interface modified copper-zinc-tin-sulfur-selenium film, preparation method thereof and solar cell

Abstract

The invention discloses a gold-silver alloy nanoparticle interface modified copper-zinc-tin-sulfur-selenium film, a preparation method thereof and a solar cell, and belongs to the technical field of photoelectric material new energy. Gold-silver alloy nanoparticles are uniformly distributed on the surface of the copper-zinc-tin-sulfur-selenium film. According to the invention, interface modification is carried out on the CZTSSe film by using the gold-silver alloy nanoparticles, so that the light absorption performance, Raman scattering performance and the like of the CZTSSe film are effectively improved, and then the performance of collection efficiency, open-circuit voltage, short-circuit current density, filling factors and the like of the solar cell is improved by applying the interface-modified CZTSSe to the solar cell. Therefore, the solar cell has more excellent use performance.

Description

Technical Field

[0001] This invention belongs to the field of optoelectronic materials and new energy technology, specifically relating to a copper-zinc-tin-sulfur-selenium thin film with gold-silver alloy nanoparticle interface modification, its preparation method, and a solar cell. Background Technology

[0002] Copper-zinc-tin-sulfur-selenium (CZTSSe) thin-film solar cells possess advantages such as high absorption coefficient, high stability, tunable bandgap, rich constituent elements, and non-toxicity, demonstrating enormous development potential. They primarily provide power by converting light energy into electrical energy through photoelectric conversion.

[0003] Light absorption is the initial step in photoelectric conversion, and its efficiency directly affects the generation and collection efficiency of photogenerated carriers. However, current CZTSSe thin-film solar cells have insufficient absorption capacity for long-wavelength photons, resulting in the ineffective utilization of some solar spectrum energy and limiting their efficiency improvement.

[0004] Therefore, it is necessary to provide a copper-zinc-tin-sulfur-selenium thin film with gold-silver alloy nanoparticle interface modification, its preparation method, and a copper-zinc-tin-sulfur-selenium thin film solar cell, so as to enhance the light absorption capacity of the absorption layer and improve the performance of the solar cell. Summary of the Invention

[0005] To overcome the problems in the prior art, this invention modifies the interface of CZTSSe thin films using gold and silver alloy nanoparticles. The gold and silver alloy nanostructures possess both excellent plasmonic properties and chemical stability, effectively enhancing the light absorption capacity of the absorption layer, thereby improving the external quantum efficiency (EQE) and short-circuit current density of the solar cell.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution: In one aspect, this invention proposes a copper-zinc-tin-sulfur-selenium thin film with gold-silver alloy nanoparticle interface modification, wherein gold-silver alloy nanoparticles are uniformly distributed on the surface of the copper-zinc-tin-sulfur-selenium thin film.

[0007] In another aspect, the present invention provides a method for preparing the above-mentioned thin film, the method comprising the following steps: (1) Au and Ag are deposited onto the surface of a copper-zinc-tin-sulfur-selenium thin film by thermal evaporation to form an Au layer and an Ag layer with nanometer-scale thickness.

[0008] (2) The copper-zinc-tin-sulfur-selenium thin film obtained by hot evaporation in step (1) is annealed to obtain a copper-zinc-tin-sulfur-selenium thin film with gold-silver alloy nanoparticle interface modification.

[0009] The CZTSSe thin film in step (1) is prepared by the following method: Thiourea (Tu) was added to ethylene glycol methyl ether (MOE) solvent and stirred until Tu was completely dissolved, resulting in a colorless solution. Then, SnCl4·5H2O was added and stirring continued until SnCl4·5H2O was completely dissolved, resulting in a pale yellow solution. Next, CuCl was added and stirring continued until CuCl was completely dissolved, resulting in a yellow solution. Finally, zinc acetate dihydrate (Zn(OAC)2·2H2O) was added and stirring continued until Zn(OAC)2·2H2O was completely dissolved, resulting in a pale yellow solution, thus obtaining the Cu-Zn-Sn-S precursor solution.

[0010] The precursor solution was then centrifuged and filtered using a disposable needle filter.

[0011] The Cu-Zn-Sn-S precursor solution was dropped into the center of the Mo glass. After the solution was distributed on the entire Mo glass, spin coating was started. After the spin coating was completed, the sample was removed and baked. After baking, the sample was allowed to cool to room temperature. The above spin coating-baking process was repeated for 10 cycles to obtain the Cu-Zn-Sn-S pre-coated thin film.

[0012] Selenization of Cu-Zn-Sn-S pre-coated thin films yields CZTSSe thin films.

[0013] Preferably, in step (1), the air pressure is 4.8 × 10⁻⁶. -4 ~5.2×10 -4 Pa, evaporation rate is 0.1 Å / s.

[0014] Preferably, in step (1), Au is first deposited onto the surface of a copper-zinc-tin-sulfur-selenium thin film to form an Au layer, and then Ag is deposited onto the surface of the Au layer to form an Ag layer. After that, Au is deposited onto the surface of the Ag layer again to form an Au layer. The thickness ratio between the Au layers is 1:1, and the ratio of the total thickness of the Ag layer to the Au layer is Ag layer:Au layer = 5:2.

[0015] Preferably, the total thickness of the Au layer and the Ag layer is 12~16nm.

[0016] Preferably, in step (2), the copper-zinc-tin-sulfur-selenium film that has been thermally vaporized is heated to 348~352℃ in a nitrogen atmosphere and kept at that temperature for 14~16 minutes. Then, the copper-zinc-tin-sulfur-selenium film is placed on a copper plate for cooling to obtain a copper-zinc-tin-sulfur-selenium film with gold-silver alloy nanoparticle interface modification.

[0017] The present invention also proposes a solar cell using a CZTSSe thin film modified with the above-mentioned gold and silver alloy nanoparticle interface as the absorber layer.

[0018] Preferably, the solar cell is formed by sequentially stacking a soda-lime glass layer (SLG), a molybdenum layer, an absorber layer, a cadmium sulfide (CdS) buffer layer, an intrinsic zinc oxide layer (i-ZnO), a tin-doped indium oxide window layer (ITO), a nickel layer, and an aluminum layer.

[0019] In the preparation process of the CZTSSe thin film, the CZTSSe thin film is already spin-coated onto the Mo glass. The Mo glass has a two-layer structure, which includes an SLG layer and a Mo layer. Therefore, in the process of solar cell fabrication, after the thermal evaporation of Au and Ag and annealing, a CdS buffer layer is deposited on the CZTSSe thin film by chemical bath method. Then, an i-ZnO layer is magnetron sputtered on the CdS buffer layer, followed by an ITO layer magnetron sputtered on the i-ZnO layer. Finally, a Ni layer and an Al layer are sequentially thermally evaporated on the ITO layer. The Ni layer and the Al layer together form the top electrode, thus obtaining the solar cell.

[0020] In solar cells, the thickness of the SLG layer is typically 2 mm, the thickness of the molybdenum layer is typically 1 μm, the thickness of the absorber layer is typically 1.2 μm (in this invention, the thickness of the gold-silver alloy nanoparticle interface modification layer is at the nanometer level, which will not significantly increase the thickness of the absorber layer), the thickness of the CdS buffer layer is typically 50 nm, the thickness of the i-ZnO layer is typically 50 nm, the thickness of the ITO layer is typically 200 nm, the thickness of the Ni layer is typically 50 nm, and the thickness of the Al layer is typically 500 nm.

[0021] The beneficial effects of this invention are: 1. This invention involves thermally evaporating gold and silver alloy nanoparticles onto the surface of a CZTSSe thin film. Silver nanoparticles possess excellent plasmon properties, while gold nanoparticles exhibit good stability. This gold-silver bimetallic nanostructure combines the advantages of both metals. The gold-silver alloy nanoparticles act as an interface modifier on the CZTSSe thin film, effectively enhancing the light-harvesting ability of the absorption layer, improving incident light utilization, and consequently improving the short-circuit current density and fill factor of the CZTSSe thin-film solar cell, thereby increasing the photoelectric conversion efficiency of the solar cell.

[0022] 2. Since a small amount of silver element diffuses into the absorption layer after silver nanoparticles come into contact with the CZTSSe film, which has an adverse effect on the absorption layer, this invention first deposits an Au layer, then deposits an Ag layer, and finally deposits another Au layer. This method uses a gold layer to prevent silver element from diffusing into the CZTSSe film. At the same time, depositing another Au layer on the Ag layer provides a certain degree of protection for the chemically unstable Ag layer and enhances the chemical stability of the gold-silver alloy nanoparticles.

[0023] 3. This invention enhances the light absorption performance of CZTSSe thin films and improves their photoelectric conversion efficiency by modifying the interface on the surface of CZTSSe thin films, thus avoiding changes in the crystal structure of CZTSSe thin films caused by doping. Attached Figure Description

[0024] Figure 1 This is a surface SEM image of the CZTSSe absorber layer film modified with gold-silver alloy nanoparticles prepared in Example 1 of this invention. Figure 2 Here is a surface SEM image of the CZTSSe absorber layer film in Comparative Example 1; Figure 3 This is a cross-sectional SEM image of the CZTSSe absorber layer film modified with gold-silver alloy nanoparticles prepared in Example 1 of this invention. Figure 4 The image shows a cross-sectional SEM image of the CZTSSe absorber layer film in Comparative Example 1. Figure 5 Raman blotting of the CZTSSe absorber layer film modified with gold-silver alloy nanoparticle interface prepared in Example 1 of this invention; Figure 6 Raman plot of the CZTSSe absorber layer film in Comparative Example 1; Figure 7 The UV-Vis-NIR diffuse reflectance spectrum of the CZTSSe absorption layer film modified with gold-silver alloy nanoparticles prepared in Example 1 of this invention. Figure 8 The UV-Vis-NIR diffuse reflectance spectrum of the CZTSSe absorption layer film in Comparative Example 1 is shown. Figure 9 The JV curve of the CZTSSe thin-film solar cell prepared in Example 4 of this invention is shown. Figure 10 The JV curve of the CZTSSe thin-film solar cell in Comparative Example 2 is shown. Figure 11 The EQE curve of the CZTSSe thin-film solar cell prepared in Example 4 of this invention is shown. Figure 12 The EQE curve of the CZTSSe thin-film solar cell in Comparative Example 2 is shown. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited to the content described.

[0026] In the preparation of the CZTSSe thin film and solar cell of this invention, all chemical reagents except those specifically mentioned were commercially available analytical grade reagents.

[0027] The CZTSSe thin films in the embodiments and comparative examples of this invention were prepared by the following method: (1) Preparation of Cu-Zn-Sn-S precursor solution: Add 12 mL of MOE solvent to a clean 18 mL glass bottle with a rotor and cap, weigh 2.2041 g of Tu and add it to the glass bottle. Place it on a stirrer at 60 °C and 1000 r / min and stir for 15 min until completely dissolved. The solution is colorless. Then add 1.4399 g of SnCl4·5H2O and continue stirring for 15 min until completely dissolved. The solution is pale yellow. Then add 0.6465 g of CuCl and continue stirring for 30 min until completely dissolved. The solution is yellow. Finally, add 1.0097 g of Zn(OAC)2·2H2O and continue stirring for 30 min until completely dissolved. The solution is pale yellow.

[0028] The above solution was dispensed into 4 mL centrifuge tubes and centrifuged for 10 min at a speed of 10000 r / min. After centrifugation, the solution was filtered using a disposable needle filter with a pore size of 0.45 μm to obtain the Cu-Zn-Sn-S precursor solution.

[0029] (2) Preparation of Cu-Zn-Sn-S precursor thin film by solution spin coating: First, set aside the clean Mo glass and the prepared Cu-Zn-Sn-S precursor solution. Set the hot plate temperature to 280℃ and the spin coater parameters to 3000rpm / 30s. First, place the Mo glass on the suction cup of the spin coater for vacuum fixation. Use a pipette to drop 0.2mL of precursor solution into the center of the Mo glass. After the solution is distributed across the entire Mo glass, start spin coating. After completion, remove the Mo glass and bake it in the center of the hot plate for 2 minutes. Finally, remove the sample and cool it to room temperature. Repeat the above spin coating-baking process for 10 cycles to obtain the Cu-Zn-Sn-S pre-coated thin film of the required thickness.

[0030] (3) Rapid heating and selenization to prepare CZTSSe absorber film: Before selenization, the graphite box needs to be calcined in the oven. Usually, 240±5mg of selenium particles are placed in the graphite box, and then the graphite box is placed in a tube furnace. The vacuum pump is turned on to evacuate the gas pressure in the furnace to 3.0×10. 4Argon gas was introduced to atmospheric pressure, and the furnace was evacuated and cleaned three times. The parameters were set to heat to 580℃ in 60s and maintain the temperature for 1200s. After the dry-firing, the tube furnace was allowed to cool to room temperature. The graphite box was removed, and the prepared Cu-Zn-Sn-S pre-coated thin film sample and 720±5mg of selenium particles were placed into the graphite box. The graphite box was then placed in the tube furnace and cleaned three times with argon gas at room temperature. The selenization parameters were set to heat to 560℃ in 60s and maintain the temperature for 1200s. Argon gas was purged throughout the process at a flow rate of 80mL / min. Finally, after selenization, the sample was removed after the tube furnace cooled to room temperature. This yielded the CZTSSe thin film.

[0031] Example 1 In this embodiment, CZTSSe thin films modified with gold-silver alloy nanoparticle interfaces were prepared using the following method: (1) Place the CZTSSe thin film prepared above into the chamber of a thermal evaporation coating machine, and place Au and Ag particles on the tungsten boats of the two evaporation sources respectively. Wait until the chamber pressure is evacuated to 5×10 -4 Evaporation begins after Pa, with an evaporation rate of 0.1 Å / s.

[0032] First, Au particles are vapor-deposited to form a 2nm thick Au layer on the surface of the CZTSSe thin film. Then, Ag particles are vapor-deposited to form a 10nm thick Ag layer on the surface of the Au layer. After that, Au particles are vapor-deposited again to form a 2nm thick Au layer on the surface of the Ag layer, thus completing the vapor deposition process.

[0033] (2) After the vapor deposition is completed, the sample is taken out and placed in a glove box filled with nitrogen to heat the sample to 350°C. After holding the temperature for 15 minutes, the sample is taken out and placed on a copper plate for rapid cooling to complete the annealing and obtain a CZTSSe thin film with gold and silver alloy nanoparticle interface modification.

[0034] Example 2 In this embodiment, CZTSSe thin films modified with gold-silver alloy nanoparticle interfaces were prepared using the following method: (1) Place the CZTSSe thin film prepared above into the chamber of a thermal evaporation coating machine, and place Au and Ag particles on the tungsten boats of the two evaporation sources respectively. Wait until the chamber pressure is evacuated to 4.8 × 10⁻⁶. -4 Then, vapor deposition began at a rate of 0.1 Å / s.

[0035] First, Au particles are vapor-deposited to form a 1.7 nm thick Au layer on the surface of the CZTSSe thin film. Then, Ag particles are vapor-deposited to form an 8.5 nm thick Ag layer on the surface of the Au layer. Finally, Au particles are vapor-deposited again to form a 1.7 nm thick Au layer on the surface of the Ag layer, thus completing the vapor deposition process.

[0036] (2) After the vapor deposition is completed, the sample is taken out and placed in a glove box filled with nitrogen to heat the sample to 348°C. After holding the temperature for 16 minutes, the sample is taken out and placed on a copper plate for rapid cooling to complete the annealing and obtain a CZTSSe thin film modified with gold and silver alloy nanoparticle interface.

[0037] The CZTSSe thin film modified with gold-silver alloy nanoparticle interface prepared in this embodiment has similar properties to that in Example 1.

[0038] Example 3 In this embodiment, CZTSSe thin films modified with gold-silver alloy nanoparticle interfaces were prepared using the following method: (1) Place the CZTSSe thin film prepared above into the chamber of a thermal evaporation coating machine, and place Au and Ag particles on the tungsten boats of the two evaporation sources respectively. Wait until the chamber pressure is evacuated to 5.2 × 10⁻⁶. -4 Evaporation begins after Pa, with an evaporation rate of 0.1 Å / s.

[0039] First, Au particles are vapor-deposited to form a 2.28 nm thick Au layer on the surface of the CZTSSe thin film. Then, Ag particles are vapor-deposited to form an 11.4 nm thick Ag layer on the surface of the Au layer. Finally, Au particles are vapor-deposited again to form a 2.28 nm thick Au layer on the surface of the Ag layer, thus completing the vapor deposition process.

[0040] (2) After the vapor deposition is completed, the sample is taken out and placed in a glove box filled with nitrogen. The sample is heated to 352°C and kept at that temperature for 14 minutes. The sample is then taken out and placed on a copper plate for rapid cooling to complete the annealing and obtain a CZTSSe thin film with gold and silver alloy nanoparticle interface modification.

[0041] The CZTSSe thin film modified with gold-silver alloy nanoparticle interface prepared in this embodiment has similar properties to that in Example 1.

[0042] Example 4 In this embodiment, a solar cell was prepared using the CZTSSe thin film obtained in Example 1 according to the following method: (1) A 50 nm thick CdS layer was deposited on a CZTSSe thin film modified with gold-silver alloy nanoparticle interface by chemical water bath method. The water bath temperature was 75 °C and the stirring speed was 450 r / min.

[0043] (2) Place the sample with the deposited CdS buffer layer into the chamber of the magnetron sputtering instrument and evacuate the chamber pressure to 5 × 10⁻⁶. - 4First, the RF power supply was connected to the ZnO target. After ignition, pre-sputtering was performed for 10 minutes, maintaining a sputtering pressure of 0.5 Pa. Sputtering was then performed at a sputtering power of 35 W for 18 minutes, followed by sputtering at a sputtering power of 60 W for 4 minutes. Then, the RF power supply was connected to the ITO target. After ignition, pre-sputtering was performed for 10 minutes, maintaining a sputtering pressure of 0.3 Pa. Sputtering was then performed at a sputtering power of 80 W for 100 minutes. Finally, the sample was removed after the molecular pump stopped. A 50 nm thick i-ZnO layer and a 200 nm thick ITO window layer were obtained.

[0044] (3) A Ni layer with a thickness of 50 nm and an Al layer with a thickness of 500 nm were sequentially deposited on the ITO window layer by thermal evaporation. The CZTSSe thin-film solar cell was thus fabricated.

[0045] Comparative Example 1 The CZTSSe thin film in this comparative example was modified at the interface without gold or silver alloy nanoparticles.

[0046] Comparative Example 2 Using the unmodified CZTSSe thin film from Comparative Example 1, a solar cell was fabricated using the same method as in Example 2.

[0047] Relevant performance tests were conducted on Embodiments 1 and 4 of the present invention, and Comparative Examples 1-2, and the results are as follows: Figure 1-12 As shown.

[0048] pass Figure 1 and Figure 2 The comparison shows that in the CZTSSe thin film modified with gold and silver alloy nanoparticles prepared by the present invention, the gold and silver alloy nanoparticles are evenly distributed and well dispersed. The grains of the CZTSSe absorber layer film are not destroyed and still exhibit a dense and flat morphology of large grains with good grain morphology, which is conducive to carrier transport.

[0049] pass Figure 3 and Figure 4 It can be seen that, regardless of whether there is interface modification, the CZTSSe absorber film exhibits large grains that run through the entire layer and forms good back interface contact with the Mo layer, further proving that the interface modification of the present invention will not damage the grain structure of the CZTSSe absorber film.

[0050] pass Figure 5 and Figure 6 The comparison shows that the CZTSSe absorber layer film modified with gold and silver alloy nanoparticles in this invention has relatively better Raman scattering performance.

[0051] pass Figure 7 and Figure 8The comparison shows that the CZTSSe absorber layer film modified with gold and silver alloy nanoparticles in this invention has relatively better light absorption performance.

[0052] pass Figure 9 and 10 The comparison shows that the solar cell in Example 4 has an efficiency of 12.4%, an open-circuit voltage of 518.2 mV, and a short-circuit current density of 39.08 mA / cm². 2 The fill factor of the solar cell of the present invention is 61.44%, while the efficiency of the solar cell of Comparative Example 2 is 10.4%, the open-circuit voltage is 495.0mV, the short-circuit current density is 38.10 mA / cm2, and the fill factor is 55.09%. This proves that the solar cell of the present invention has higher collection efficiency, and the open-circuit voltage, short-circuit current density and fill factor are all improved.

[0053] pass Figure 11 and Figure 12 The comparison shows that the maximum EQE value in Example 4 is greater than 90%, while the maximum EQE value in Comparative Example 2 is close to 90%, proving that the EQE of the solar cell of the present invention is improved to a certain extent and the EQE response is increased.

[0054] In summary, this invention effectively improves the light absorption and Raman scattering properties of CZTSSe thin films by using gold and silver alloy nanoparticles to modify the CZTSSe film interface. Furthermore, by using the interface-modified CZTSSe in solar cells, the collection efficiency, open-circuit voltage, short-circuit current density, and fill factor of the solar cells are improved, resulting in solar cells with superior performance.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A copper-zinc-tin-sulfur-selenium thin film with gold-silver alloy nanoparticle interface modification, characterized in that: Gold and silver alloy nanoparticles are uniformly distributed on the surface of the copper-zinc-tin-sulfur-selenium thin film.

2. The method for preparing the copper-zinc-tin-sulfur-selenium thin film with gold-silver alloy nanoparticle interface modification according to claim 1, characterized in that: The preparation method includes the following steps: (1) Au and Ag are deposited onto the surface of a copper-zinc-tin-sulfur-selenium thin film by thermal evaporation to form an Au layer and an Ag layer with nanoscale thickness; (2) The copper-zinc-tin-sulfur-selenium thin film obtained by hot evaporation in step (1) is annealed to obtain a copper-zinc-tin-sulfur-selenium thin film with gold-silver alloy nanoparticle interface modification.

3. The preparation method according to claim 2, characterized in that: In step (1), the air pressure is 4.8 × 10⁻⁶. -4 ~5.2×10 -4 Pa, evaporation rate is 0.1 Å / s.

4. The preparation method according to claim 2, characterized in that: In step (1), Au is first deposited onto the surface of a copper-zinc-tin-sulfur-selenium thin film to form an Au layer, and then Ag is deposited onto the surface of the Au layer to form an Ag layer. After that, Au is deposited onto the surface of the Ag layer again to form an Au layer. The thickness ratio between the Au layers is 1:1, and the ratio of the total thickness of the Ag layer to the Au layer is Ag layer:Au layer = 5:

2.

5. The preparation method according to claim 4, characterized in that: The total thickness of the Au and Ag layers is 12-16 nm.

6. The preparation method according to claim 2, characterized in that: In step (2), the copper-zinc-tin-sulfur-selenium film that has been thermally vaporized is heated to 348~352℃ in a nitrogen atmosphere and kept at that temperature for 14~16 minutes. Then, the copper-zinc-tin-sulfur-selenium film is placed on a copper plate for cooling to obtain a copper-zinc-tin-sulfur-selenium film with gold-silver alloy nanoparticle interface modification.

7. A solar cell, characterized in that: The copper-zinc-tin-sulfur-selenium thin film modified with gold-silver alloy nanoparticles as described in claim 1 is used as the absorber layer of a solar cell.

8. The solar cell according to claim 7, characterized in that: The solar cell is formed by stacking a soda-lime glass layer, a molybdenum layer, an absorber layer, a cadmium sulfide buffer layer, an intrinsic zinc oxide layer, a tin-doped indium oxide window layer, a nickel layer, and an aluminum layer in sequence.

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