A method for improving the efficiency of SnS thin-film solar cells

Abstract

A method for improving the efficiency of SnS thin-film solar cells. In the SnS thin-film solar cells, the SnS thin film is prepared by electrochemcial deposition, and the electroplating solution used is a composite electroplating solution prepared by adding a composite complexing agent. The composite complexing agent consists of sodium citrate (SC), triphenylphosphine oxide (TPPO) and thioacetamide (TAA). By using sodium citrate, triphenylphosphine oxide and thioacetamide as complexing agents in the electrochemcial deposition process, the crystallinity and optoelectronic properties of the SnS thin film are effectively improved through their synergistic effect, which is used to prepare SnS thin-film solar cells, effectively improving the optoelectronic efficiency of the solar cells. Among them, the photoelectric conversion efficiency reaches 1.32%, which is an excellent efficiency for SnS thin-film solar cells prepared by electrochemcial deposition.

Description

Technical Field

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

[0002] In the utilization of solar energy, the solar photovoltaic power generation industry is one of the fastest growing fields. With the emergence of various photovoltaic materials, the research on solar cells is also changing with each passing day. Thin film solar cells have attracted the interest of many researchers due to their advantages such as low cost, scalable production, and high photoelectric conversion efficiency. Among them, tin sulfide (SnS) has received increasing attention because of its non-toxicity, abundant content of tin and sulfur elements on the earth, low cost, high theoretical photoelectric conversion efficiency, and stable performance.

[0003] There are many methods for preparing SnS thin films, such as vacuum evaporation method, chemical bath method, electron beam evaporation method, magnetron sputtering method, chemical vapor deposition method, electrochemical deposition method, etc. Electrochemical deposition method (ECD) is based on chemical methods, and electro-deposition is achieved at the cathode by passing an electric current through the electrolyte. The electrochemical deposition method includes constant current method and constant voltage method. Since the electrode potential is easily affected by the outside world and fluctuates during constant current deposition, it is difficult to control the film uniformity, while the constant voltage method can effectively avoid such problems. Therefore, the constant voltage method is mostly used to deposit SnS thin films.

[0004] At present, the highest device efficiency of SnS thin film solar cells is obtained by spin-coating SnS thin films and then performing secondary treatment on the SnS thin films with stannous chloride. The photoelectric conversion efficiency is only 4.8%, which is far lower than the theoretical photoelectric conversion efficiency of 33% of SnS thin film solar cells. In order to improve the photovoltaic performance of SnS thin film solar cells, the following strategies are mainly adopted in current research for improvement: (1) Post-treatment of SnS thin films, such as annealing in air, vacuum, nitrogen / argon or sulfur-containing atmosphere, so as to improve the quality of the absorption layer and thus improve the photoelectric conversion efficiency of the device. (2) Finding suitable buffer materials to regulate the energy band and light absorption, thereby improving the performance of SnS thin film solar cells.

[0005] Although the photoelectric efficiency of electrochemically deposited thin films is not high, the electrochemical method has significant advantages in preparation, such as precise control over the film deposition process, a wide range of selectable raw materials, high purity, good uniformity, and low cost of the prepared thin films. When electrochemically depositing SnS thin films, complexing agents are often added to regulate the deposition process, thereby improving the flatness and crystallinity of the thin films. For example, in the prior art, some researchers have added EDTA (ethylenediaminetetraacetic acid) as a complexing agent, effectively slowing down the deposition rate of tin ions, controlling the deposition rate and crystallization process of SnS thin films, and obtaining polycrystalline SnS thin films with an orthorhombic crystal structure. The thin films have good uniformity and surface coverage. However, the complexing agent EDTA still has limitations in improving the performance of electrochemically deposited SnS thin film solar cells. Exploring new complexing agents is of great significance for SnS thin film solar cells. Summary of the Invention

[0006] The object of the present invention is to provide a method for improving the efficiency of SnS thin film solar cells.

[0007] Another object of the present invention is to provide a preparation method for the above-mentioned SnS thin film solar cells.

[0008] The object of the present invention is achieved through the following technical solutions:

[0009] A method for improving the efficiency of SnS thin film solar cells, characterized in that: in the SnS thin film solar cell, the SnS thin film is prepared by electrochemical deposition, and the electroplating solution used is a composite electroplating solution prepared by adding a composite complexing agent. The composite complexing agent includes sodium citrate (abbreviated as SC, with the molecular formula Na3C6H5O7), triphenylphosphine oxide (abbreviated as TPPO, with the molecular formula C 18 H 15 OP), and thioacetamide (abbreviated as TAA, with the molecular formula CH3CSNH2).

[0010] During the electrochemical deposition process, since the precipitation potential of Sn 2+ is smaller than that of thiosulfate ions (S2O3 2- ), at the same concentration, when co-deposition occurs at the cathode, the deposition rate of Sn 2+ is relatively fast, and there will be more Sn in the solution that does not combine with S in a 1:1 ratio, resulting in Sn / S > 1 in the thin film, thus affecting the overall performance of the SnS thin film.

[0011] Adding a complexing agent to the electroplating solution inhibits Sn 2+ to obtain e - , but rather the complexing agent combines with Sn 2+First, a complex is formed, and then SnS is co-deposited at the cathode. Therefore, the complexing agent has an inhibitory effect on the precipitation of Sn 2+ The original chemical reactions occurring in the electroplating solution will change, and the complexing agent affects the crystal orientation of the thin film, which is beneficial to obtaining a SnS thin film with more excellent properties. However, if the added complexing agent is not appropriate, such as too fast or too slow reaction rate, the effect of regulating the crystal grains will not meet the expectations.

[0012] During the preparation of the SnS thin film, Sn 2+ is a Lewis acid with empty orbitals that can accept electrons. In the present invention, sodium citrate, triphenyl phosphine oxide, and thioacetamide are used to prepare a composite complexing agent. The composite complexing agent provides different Lewis base electron donors. Sodium citrate contains three -COONa groups, which belong to the O-donor type. Triphenyl phosphine oxide also belongs to the O-donor type, but different from the -COONa group in sodium citrate, the oxygen atom it contains is bonded to the P atom. These two O-donor type Lewis bases will give more regulation space on the basis of the regulation of the crystal by monomer sodium citrate; thioacetamide belongs to both the S-donor type and the N-donor type, and its addition will further regulate the crystallization to a greater extent on the basis of the O-donor type (-COONa group and -PO group).

[0013] Through the regulation of the composite complexing agent, the crystallinity of SnS is effectively regulated, making the grain size of the thin film larger and more uniform, reducing the surface and internal defects, and thus greatly improving the quality of the thin film.

[0014] Furthermore, the molar ratio of sodium citrate, triphenyl phosphine oxide, and thioacetamide is 2:1~2:1~2.

[0015] Further preferably, the molar ratio of sodium citrate, triphenyl phosphine oxide, and thioacetamide is 2:1.5:1.5, 2:2:1, or 2:1:2.

[0016] Further preferably, the molar ratio of sodium citrate, triphenyl phosphine oxide, and thioacetamide is 2:1:2.

[0017] Furthermore, the composite complexing agent is prepared by mixing three powders of sodium citrate, triphenyl phosphine oxide, and thioacetamide, adding deionized water and stirring, and then heating and holding at 80~100 °C for 10~12 h to form a clear light yellow solution, which is the composite complexing agent.

[0018] Furthermore, the ratio of the total amount of the three powders to the amount of deionized water used is 0.064 g:10 mL.

[0019] Furthermore, the SnS thin film is prepared by electrochemical deposition using FTO as the substrate. A composite electroplating solution is prepared, and a three-electrode system is adopted. The Ag / AgCl electrode is used as the reference electrode, the platinum wire is used as the counter electrode, and the working electrode is a conductive substrate. The deposition potential is -0.65V, and the deposition time is 70 minutes.

[0020] Furthermore, to prepare the composite electroplating solution, Na2S2O3 is added to deionized water, and after stirring and complete dissolution, SnSO4 is added. Stirring continues until complete dissolution, and then a composite complexing agent is added to form the composite electroplating solution. The pH of the electroplating solution is adjusted to 2.4 using dilute H2SO4. Finally, the electroplating solution is left standing for 70 minutes before use.

[0021] Furthermore, the dosage ratio of Na2S2O3, SnSO4, the composite complexing agent, and deionized water is 0.5956g:0.1716g:10mL:80mL.

[0022] A preparation method of an SnS thin film solar cell includes, in sequence, cleaning of the substrate, preparation of the buffer layer, preparation of the light absorption layer, and preparation of the electrode layer. It is characterized in that: the preparation of the light absorption layer is to prepare the SnS thin film by electrochemical deposition. The electroplating solution used in the electrochemical deposition is a composite electroplating solution prepared by adding a composite complexing agent. The composite complexing agent is composed of sodium citrate, triphenylphosphine oxide, and thioacetamide.

[0023] Furthermore, the molar ratio of sodium citrate, triphenylphosphine oxide, and thioacetamide is 2:1 to 2:1 to 2.

[0024] More preferably, the molar ratio of sodium citrate, triphenylphosphine oxide, and thioacetamide is 2:1.5:1.5, 2:2:1, or 2:1:2.

[0025] More preferably, the molar ratio of sodium citrate, triphenylphosphine oxide, and thioacetamide is 2:1:2.

[0026] Furthermore, the composite complexing agent is prepared by mixing the three powders of sodium citrate, triphenylphosphine oxide, and thioacetamide, adding them to deionized water and stirring, and then heating and holding at 220 - 250°C for 20 - 24 hours to form a clear light yellow solution, which is the composite complexing agent.

[0027] Furthermore, the dosage ratio of the total amount of the three powders to deionized water is 0.064g:10mL.

[0028] Furthermore, the SnS thin film is prepared by electrochemical deposition using FTO as the substrate. A electroplating solution is prepared, and a three-electrode system is adopted. The Ag / AgCl electrode is used as the reference electrode, the platinum wire is used as the counter electrode, and the working electrode is a conductive substrate. The deposition potential is -0.65V, and the deposition time is 70 minutes.

[0029] Furthermore, the composite electroplating solution is prepared by adding Na2S2O3 to deionized water, stirring and dissolving it completely, then adding SnSO4, continuing to stir and dissolve it completely, and then adding a composite chelating agent to form a composite electroplating solution, and using dilute H2SO4 to adjust the pH of the electroplating solution to 2.4. Finally, the electroplating solution is left to stand for 70 minutes before use.

[0030] Furthermore, the usage ratio of Na2S2O3, SnSO4, composite complexing agent and deionized water is 0.5956g:0.1716g:10mL:80mL.

[0031] Most specifically, a method for preparing a SnS thin film solar cell is characterized by following the steps:

[0032] S1. Substrate cleaning

[0033] Using FTO as the substrate, the substrate surface was first scrubbed with detergent powder, and then ultrasonically cleaned with diluted alkaline detergent, acetone, anhydrous ethanol, and deionized water in sequence. Each cleaning time was 30 minutes. After drying with N2, the substrate was cleaned with a UV ozone analyzer for 20 minutes.

[0034] S2. Preparation of buffer layer

[0035] (1) Preparation of dense TiO2 layer (c-TiO2)

[0036] 0.32M bis(acetylacetonato)diisopropyl titanate was dissolved in n-butanol and stirred thoroughly. The solution was filtered and then dropped onto the substrate. After spin coating at 3000 rpm / min for 30 seconds, the sample was annealed on a hot plate at 125°C for 3 minutes, and then transferred to a muffle furnace and calcined at 500°C for 40 minutes.

[0037] (2) Preparation of porous TiO2 layer (m-TiO2)

[0038] 0.3 g of mesoporous titanium oxide slurry was added to 1.834 ml of n-butanol. The precursor solution was stirred at 50 ° C for 6 h using a magnetic stirrer. After filtering, it was added dropwise to the dense TiO2 layer prepared above using a pipette. After spin coating at 2000 rpm / min for 24 seconds, the sample was transferred to a muffle furnace and calcined at 500 ° C for 60 minutes. The calcined sample was placed in a solution of TiCl4 and deionized water with a volume ratio of 5:11 and soaked at 80 ° C for 20 minutes. The sample was then removed, rinsed with deionized water, and blown dry with N2.

[0039] S3. Preparation of SnS thin film

[0040] (1) Prepare a composite complexing agent

[0041] Mix three powders of sodium citrate, triphenylphosphine oxide and thioacetamide in a molar ratio of 2:1 - 2:1 - 2, add to deionized water, stir, and then heat and keep warm at 80 - 100 °C for 10 - 12 h to form a solution, thus obtaining the composite complexing agent. The ratio of the total amount of the three powders to the amount of deionized water is 0.064 g:10 mL;

[0042] (2) Prepare a composite electroplating solution

[0043] Add Na2S2O3 to deionized water, stir until completely dissolved, then add SnSO4 and continue to stir until completely dissolved. Then add the composite complexing agent to form a composite electroplating solution, and adjust the pH of the electroplating solution to 2.4 with dilute H2SO4. Finally, let the electroplating solution stand for 70 min; the dosage ratio of Na2S2O3, SnSO4, the composite complexing agent and deionized water is 0.5956 g:0.1716 g:10 mL:80 mL;

[0044] (3) Electrochemical deposition

[0045] Adopt a three - electrode system, with an Ag / AgCl electrode as the reference electrode, a platinum wire as the counter electrode, and the working electrode being a conductive substrate. Each electrode is connected to an electrochemical workstation through a signal wire with an alligator clip. Set the deposition potential to - 0.65 V and the deposition time to 70 min through the electrochemical workstation.

[0046] S4. Prepare a metal electrode layer

[0047] Place the sample in a customized mask plate, and place the mask plate in the chamber of a thermal evaporation coater. Use a mechanical pump and a molecular pump to pump the vacuum degree of the coater to below 2×10 -4 Pa, and then evaporate metal Ag onto the sample surface by thermal evaporation. The thickness of the Ag electrode is about 100 nm, and the deposition rate is

[0048] The present invention has the following technical effects:

[0049] By using sodium citrate, triphenylphosphine oxide and thioacetamide as complexing agents in the electrochemical deposition process, the crystallization quality and optoelectronic properties of the SnS thin film are effectively improved through their synergistic effect. When used to prepare SnS thin - film solar cells, the photoelectric conversion efficiency of the solar cells is effectively improved. Among them, the photoelectric conversion efficiency reaches 1.32%, which is a relatively excellent efficiency for SnS thin - film solar cells prepared by electrochemical deposition. Brief description of the drawings

[0050] Figure 1 : The XRD pattern corresponding to the SnS thin film prepared by the present invention. DETAILED DESCRIPTION

[0051] The present invention is described in detail below through examples. It is necessary to point out that the following examples are only used to further illustrate the present invention and are not to be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above-mentioned contents of the present invention.

[0052] Example 1

[0053] A method for preparing a SnS thin film is carried out according to the following steps:

[0054] S1. Substrate cleaning

[0055] Using FTO as the substrate, the substrate surface was first scrubbed with detergent powder, and then ultrasonically cleaned with diluted alkaline detergent, acetone, anhydrous ethanol, and deionized water in sequence. Each cleaning time was 30 minutes. After drying with N2, the substrate was cleaned with a UV ozone analyzer for 20 minutes.

[0056] S2. Preparation of buffer layer

[0057] (1) Preparation of dense TiO2 layer (c-TiO2)

[0058] 0.32M bis(acetylacetonato)diisopropyl titanate was dissolved in n-butanol and stirred thoroughly. The solution was filtered and then dropped onto the substrate. After spin coating at 3000 rpm / min for 30 seconds, the sample was placed on a hot plate for annealing at 125°C for 3 minutes. The sample was then transferred to a muffle furnace and calcined at 500°C for 40 minutes to obtain a c-TiO2 layer with a thickness of 80 nm.

[0059] (2) Preparation of porous TiO2 layer (m-TiO2)

[0060] 0.3 g of mesoporous titanium oxide slurry was added to 1.834 ml of n-butanol, and the precursor solution was stirred at 50 ° C for 6 h using a magnetic stirrer. Then, it was filtered and added dropwise to the dense TiO2 layer prepared above using a pipette. After spin coating at a speed of 2000 rpm / min for 24 seconds, the sample was transferred to a muffle furnace and calcined at 500 ° C for 60 minutes. The calcined sample was placed in a solution of TiCl4 and deionized water with a volume ratio of 5:11 and soaked at 80 ° C for 20 minutes. The sample was then taken out, rinsed with deionized water, and blown dry with N2 to obtain a m-TiO2 layer with a thickness of 200 nm.

[0061] S3. Preparation of SnS thin film

[0062] (1) Preparation of composite complexing agent

[0063] Mix three powders of sodium citrate, triphenylphosphine oxide and thioacetamide in a molar ratio of 2:1 to 2:1 to 2. Add them to deionized water, stir, and then heat and keep warm at 80 - 100 °C for 10 - 12 h to form a clear solution, thus obtaining a composite complexing agent. The ratio of the total amount of the three powders to the amount of deionized water used is 0.064 g:10 mL;

[0064] (2) Prepare a composite electroplating solution

[0065] Add Na2S2O3 to deionized water, stir until completely dissolved, then add SnSO4 and continue to stir until completely dissolved. Then add the composite complexing agent to form a composite electroplating solution, and use dilute H2SO4 to adjust the pH of the electroplating solution to 2.4. Finally, let the electroplating solution stand for 70 min; the usage ratio of Na2S2O3, SnSO4, the composite complexing agent and deionized water is 0.5956 g:0.1716 g:10 mL:80 mL;

[0066] (3) Electrochemical deposition

[0067] Adopt a three - electrode system, with an Ag / AgCl electrode as the reference electrode, a platinum wire as the counter electrode, and the working electrode being a conductive substrate. Each electrode is connected to an electrochemical workstation through a signal wire with an alligator clip. Set the deposition potential to - 0.65 V and the deposition time to 70 min through the electrochemical workstation to obtain a SnS thin film layer with a thickness of 500 nm.

[0068] The complexing agent prepared in this example is a SnS thin film of SC + TPPO + TAA.

[0069] Figure 1 This is the XRD pattern corresponding to the SnS thin film prepared in this example. As shown in the figure, W / O corresponds to the SnS thin film prepared without adding any complexing agent. The diffraction peaks at 2θ = 30.47°, 2θ = 31.53°, and 2θ = 31.97° correspond to the (101), (111), and (040) crystal orientation diffraction peaks. For the SnS thin film prepared with the SC + TPPO + TAA composite complexing agent, the XRD shows that the intensities of the (101) and (040) crystal orientation diffraction peaks basically remain unchanged, while the intensity of the (111) crystal orientation diffraction peak at 2θ = 31.53° increases.

[0070] Comparative example 1

[0071] According to the method of Example 1, single complexing agent-added SnS thin films were prepared by separately adding EDTA, SC, TPPO, and TAA as complexing agents (the addition amounts of each complexing agent were the same as those of the corresponding substances in the composite complexing agent in Example 1, and the addition amount of EDTA was the same as that of SC). Similarly, SnS thin films were prepared by adding TPPO + EDTA (molar ratio 1:2), SC + TAA (molar ratio 1:1), and TPPO + TAA (molar ratio 1:2) as complexing agents respectively. An SnS thin film was prepared using EDTA + TPPO + TAA (molar ratio 2:1:2).

[0072] For the addition of different complexing agents, EDS tests were performed on the SnS thin films prepared according to the above preparation method, and the elemental content statistics in the thin films are shown in Table 1.

[0073] Table 1: EDS data of SnS thin films electrochemically deposited with different complexing agents

[0074]

[0075] As can be seen from the table, the decrease in the Sn / S ratio indicates that the addition of the complexing agent can effectively slow down the deposition of Sn 2+ Among the single complexing agents, SC has a particularly obvious effect on slowing down the deposition of Sn 2+ In the SnS thin films prepared by adding composite complexing agents composed of two single complexing agents, SC + TAA has the best effect on slowing down the deposition of Sn 2+ followed by EDTA + TPPO, and TAA + TPPO is the worst. However, SC + TAA inhibits Sn 2+ excessively, resulting in Sn / S < 1. On this basis, for EDTA + TAA + TPPO and SC + TAA + TPPO composed of three single complexing agents, in the prepared SnS thin films, SC + TAA + TPPO has the best effect on slowing down the deposition of Sn 2+ and Sn / S approaches 1, while EDTA + TAA + TPPO has a relatively poor effect on slowing down the deposition of Sn 2+ and even the ratio of Sn / S is greater than the Sn / S ratio corresponding to EDTA + TPPO.

[0076] UV-visible absorption tests were conducted on SnS films prepared with different complexing agents at optimal addition levels. The results showed that the addition of each complexing agent effectively increased the light absorption capacity of the SnS films. Furthermore, compared with the light absorption performance of SnS films prepared with the EDTA+TPPO+TAA complexing agent, the SC+TPPO+TAA complexing agent significantly improved the light absorption performance of the SnS films. Tauc plots show that the addition of complexing agents increased the optical band gap of the SnS films. The EDTA+TAA+TPPO complex had a smaller effect, increasing the film band gap to 1.25 eV, while the SC+TPPO+TAA complex increased the film band gap to 1.29 eV.

[0077] Example 2

[0078] A method for preparing a SnS thin film solar cell is carried out according to the following steps:

[0079] S1. Substrate cleaning

[0080] Using FTO as the substrate, the substrate surface was first scrubbed with detergent powder, and then ultrasonically cleaned with diluted alkaline detergent, acetone, anhydrous ethanol, and deionized water in sequence. Each cleaning time was 30 minutes. After drying with N2, the substrate was cleaned with a UV ozone analyzer for 20 minutes.

[0081] S2. Preparation of buffer layer

[0082] (1) Preparation of dense TiO2 layer (c-TiO2)

[0083] 0.32M bis(acetylacetonato)diisopropyl titanate was dissolved in n-butanol and stirred thoroughly. The solution was filtered and then dropped onto the substrate. After spin coating at 3000 rpm / min for 30 seconds, the sample was placed on a hot plate for annealing at 125°C for 3 minutes. The sample was then transferred to a muffle furnace and calcined at 500°C for 40 minutes to obtain a c-TiO2 layer with a thickness of 80 nm.

[0084] (2) Preparation of porous TiO2 layer (m-TiO2)

[0085] Add 0.3 g of mesoporous titanium oxide slurry to 1.834 ml of n-butanol. Use a magnetic stirrer to stir the precursor solution at 50 °C for 6 h, then filter and use a pipette to drop it onto the prepared dense TiO2 layer. Spin-coat at a speed of 2000 rpm for 24 s, then transfer the sample to a muffle furnace and calcine it at 500 °C for 60 min. Place the calcined sample in a solution with a volume ratio of TiCl4 to deionized water of 5:11, soak it at 80 °C for 20 min, then take out the sample, rinse it with deionized water and dry it with N2 to obtain an m-TiO2 layer with a thickness of 200 nm;

[0086] S3. Preparation of SnS thin film

[0087] (1) Prepare the composite complexing agent

[0088] Mix three powders of sodium citrate, triphenylphosphine oxide and thioacetamide according to a molar ratio of 2:1~2:1~2, add deionized water and stir, then heat and keep warm at 80~100 °C for 10~12 h to form a clear solution, that is, the composite complexing agent. The ratio of the total amount of the three powders to the amount of deionized water used is 0.064 g:10 mL;

[0089] (2) Prepare the composite electroplating solution

[0090] Add Na2S2O3 to deionized water, stir until completely dissolved, then add SnSO4 and continue to stir until completely dissolved, and then add the composite complexing agent to form a composite electroplating solution. Use dilute H2SO4 to adjust the pH of the electroplating solution to 2.4, and finally place the electroplating solution for 70 min; the usage ratio of Na2S2O3, SnSO4, the composite complexing agent and deionized water is 0.5956 g:0.1716 g:10 mL:80 mL;

[0091] (3) Electrochemical deposition

[0092] Adopt a three-electrode system, with an Ag / AgCl electrode as the reference electrode, a platinum wire as the counter electrode, and the working electrode as the conductive substrate. Each electrode is connected to an electrochemical workstation through a signal wire with an alligator clip. Set the deposition potential to -0.65 V and the deposition time to 70 min through the electrochemical workstation to obtain a SnS thin film layer with a thickness of 500 nm.

[0093] S4. Preparation of the metal electrode layer

[0094] Place the sample in a customized mask plate, and place the mask plate in the chamber of a thermal evaporation coater. Use a mechanical pump and a molecular pump to pump the vacuum of the coater to below 2×10-4 Pa, and then use thermal evaporation to evaporate metal Ag onto the sample surface. The thickness of the Ag electrode is about 100 nm, and the deposition rate is

[0095] Comparative Example 2

[0096] According to the complexing agent addition schemes in Comparative Example 1, the preparation method of Example 2 was adopted to prepare SnS thin-film solar cells prepared with different complexing agents.

[0097] By plotting the photocurrent-voltage (JV) curves of the SnS thin film solar cells prepared with different complexing agents in Example 1 and Comparative Example 2, the corresponding photovoltaic parameters are shown in Table 2.

[0098] Table 2: Photovoltaic parameters of SnS thin film solar cells prepared by different schemes

[0099]

[0100] As can be seen from the above table, the overall performance parameters of SnS thin-film solar cells prepared by using SC+TAA+TPPO composite complexing agent are optimal, which effectively improves the efficiency of solar cells. The photoelectric conversion efficiency reaches 1.32%, which is relatively excellent among the SnS thin-film solar cells currently prepared by electrochemical deposition.

[0101] Example 3

[0102] A method for preparing a SnS thin film solar cell is carried out according to the following steps:

[0103] S1. Substrate cleaning

[0104] Using FTO as the substrate, the substrate surface was first scrubbed with detergent powder, and then ultrasonically cleaned with diluted alkaline detergent, acetone, anhydrous ethanol, and deionized water in sequence. Each cleaning time was 30 minutes. After drying with N2, the substrate was cleaned with a UV ozone analyzer for 20 minutes.

[0105] S2. Preparation of buffer layer

[0106] (1) Preparation of dense TiO2 layer (c-TiO2)

[0107] 0.32M bis(acetylacetonato)diisopropyl titanate was dissolved in n-butanol and stirred thoroughly. The solution was filtered and then dropped onto the substrate. After spin coating at 3000 rpm / min for 30 seconds, the sample was placed on a hot plate for annealing at 125°C for 3 minutes. The sample was then transferred to a muffle furnace and calcined at 500°C for 40 minutes to obtain a c-TiO2 layer with a thickness of 80 nm.

[0108] (2) Preparation of porous TiO2 layer (m-TiO2)

[0109] Add 0.3 g of mesoporous titanium oxide slurry to 1.834 ml of n-butanol. Use a magnetic stirrer to stir the precursor solution at 50 °C for 6 h, then filter and use a pipette to drop it onto the prepared dense TiO2 layer. Spin-coat at a speed of 2000 rpm for 24 s, then transfer the sample to a muffle furnace and calcine it at 500 °C for 60 min. Place the calcined sample in a solution with a volume ratio of TiCl4 to deionized water of 5:11, soak it at 80 °C for 20 min, then take out the sample, rinse it with deionized water and dry it with N2 to obtain an m-TiO2 layer with a thickness of 200 nm;

[0110] S3. Preparation of SnS thin film

[0111] (1) Prepare the composite complexing agent

[0112] Mix the three powders of sodium citrate, triphenylphosphine oxide and thioacetamide according to a molar ratio of 2:1~2:1~2, add them to deionized water and stir, then heat and keep warm at 80~100 °C for 10~12 h to form a clear solution, that is, the composite complexing agent. The dosage ratio of the total amount of the three powders to deionized water is 0.064 g:10 mL;

[0113] (2) Prepare the composite electroplating solution

[0114] Add Na2S2O3 to deionized water, stir and dissolve it completely, then add SnSO4 and continue to stir and dissolve it completely. Then add the composite complexing agent to form a composite electroplating solution, and use dilute H2SO4 to adjust the pH of the electroplating solution to 2.4. Finally, place the electroplating solution for 70 min; the dosage ratio of Na2S2O3, SnSO4, the composite complexing agent and deionized water is 0.5956 g:0.1716 g:10 mL:80 mL;

[0115] (3) Electrochemical deposition

[0116] Adopt a three-electrode system, with an Ag / AgCl electrode as the reference electrode, a platinum wire as the counter electrode, and the working electrode as the conductive substrate. Each electrode is connected to an electrochemical workstation through a signal wire with an alligator clip. Set the deposition potential to -0.65 V and the deposition time to 70 min through the electrochemical workstation to obtain a SnS thin film layer with a thickness of 500 nm.

[0117] S4. Preparation of the metal electrode layer

[0118] Place the sample in a customized mask plate, and place the mask plate in the chamber of a thermal evaporation coater. Use a mechanical pump and a molecular pump to pump the vacuum degree of the coater to below 2×10 -4 Pa, and then evaporate metal Ag onto the sample surface by thermal evaporation. The thickness of the Ag electrode is about 100 nm, and the deposition rate is

[0119] The open circuit voltage V oc is 0.381V, short-circuit current density J sc 6.59 mA / cm 2 , fill factor FF is 50.94%, and photoelectric conversion line efficiency PCE is 1.27%.

[0120] Example 4

[0121] A method for preparing a SnS thin film solar cell is carried out according to the following steps:

[0122] S1. Substrate cleaning

[0123] Using FTO as the substrate, the substrate surface was first scrubbed with detergent powder, and then ultrasonically cleaned with diluted alkaline detergent, acetone, anhydrous ethanol, and deionized water in sequence. Each cleaning time was 30 minutes. After drying with N2, the substrate was cleaned with a UV ozone analyzer for 20 minutes.

[0124] S2. Preparation of buffer layer

[0125] (1) Preparation of dense TiO2 layer (c-TiO2)

[0126] 0.32M bis(acetylacetonato)diisopropyl titanate was dissolved in n-butanol and stirred thoroughly. The solution was filtered and then dropped onto the substrate. After spin coating at 3000 rpm / min for 30 seconds, the sample was placed on a hot plate for annealing at 125°C for 3 minutes. The sample was then transferred to a muffle furnace and calcined at 500°C for 40 minutes to obtain a c-TiO2 layer with a thickness of 80 nm.

[0127] (2) Preparation of porous TiO2 layer (m-TiO2)

[0128] 0.3 g of mesoporous titanium oxide slurry was added to 1.834 ml of n-butanol. The precursor solution was stirred at 50 ° C for 6 h using a magnetic stirrer. After filtering, it was added dropwise to the dense TiO2 layer prepared above using a pipette. After spin coating at 2000 rpm / min for 24 seconds, the sample was transferred to a muffle furnace and calcined at 500 ° C for 60 minutes. The calcined sample was placed in a solution of TiCl4 and deionized water with a volume ratio of 5:11 and soaked at 80 ° C for 20 minutes. The sample was then removed, rinsed with deionized water, and blown dry with N2.

[0129] S3. Preparation of SnS thin film

[0130] (1) Preparation of composite complexing agent

[0131] The composite complexing agent is obtained by mixing three powders of sodium citrate, triphenylphosphine oxide and thioacetamide in a molar ratio of 2:1 to 2:1 to 2, adding them to deionized water and stirring, and heating and keeping them at 80 to 100° C. for 10 to 12 hours to form a clear solution. The ratio of the total amount of the three powders to deionized water is 0.064 g:10 mL;

[0132] (2) Preparation of composite electroplating solution

[0133] Na2S2O3 was added to deionized water, and after stirring and dissolving completely, SnSO4 was added and stirred and dissolved completely. Then, a composite complexing agent was added to form a composite electroplating solution, and the pH of the electroplating solution was adjusted to 2.4 with dilute H2SO4. Finally, the electroplating solution was allowed to stand for 70 minutes. The dosage ratio of the Na2S2O3, SnSO4, composite complexing agent, and deionized water was 0.5956 g:0.1716 g:10 mL:80 mL.

[0134] (3) Electrochemical deposition

[0135] A three-electrode system was adopted, with an Ag / AgCl electrode as the reference electrode, a platinum wire as the counter electrode, and a conductive substrate as the working electrode. Each electrode was connected to an electrochemical workstation via a signal line with an alligator clip. The deposition potential was set to -0.65 V and the deposition time was 70 min via the electrochemical workstation.

[0136] S4. Preparation of metal electrode layer

[0137] The sample was placed in a customized mask plate, and the mask plate was placed in the chamber of the thermal evaporation coating instrument. The vacuum degree of the evaporation coating instrument was pumped to less than 2×10 -4 Pa, and then the metal Ag is evaporated onto the sample surface by thermal evaporation. The thickness of the Ag electrode is about 100nm, and the deposition rate is

[0138] The open circuit voltage V oc is 0.384V, and the short-circuit current density is J sc 6.65 mA / cm 2 , fill factor FF is 51.18%, and photoelectric conversion efficiency PCE is 1.30%.

Claims

1. A method for improving the efficiency of SnS thin film solar cells, characterized in that: In the SnS thin film solar cell, the SnS thin film is prepared by electrochemcial deposition, and the electroplating solution used is a composite electroplating solution prepared by adding a composite complexing agent. The composite complexing agent consists of sodium citrate, triphenylphosphine oxide and thioacetamide in a molar ratio of 2:1~2:1~2.

2. The method for improving the efficiency of a SnS thin-film solar cell according to claim 1, characterized in that: The molar ratio of the sodium citrate, triphenylphosphine oxide and thioacetamide is 2:1.5:1.5, 2:2:1 or 2:1:

2.

3. A method for improving the efficiency of SnS thin-film solar cells according to claim 1 or 2, characterized in that: The composite complexing agent is obtained by mixing three powders of sodium citrate, triphenylphosphine oxide and thioacetamide, adding deionized water and stirring, and then heating and keeping warm at 80~100 °C for 10~12 h to form a clear light yellow solution, which is the composite complexing agent.

4. A method for improving the efficiency of a SnS thin film solar cell according to claim 3, characterized in that: The dosage ratio of the total amount of the three powders to the amount of deionized water is 0.064 g:10 mL.

5. The method for improving the efficiency of a SnS thin film solar cell according to claim 4, characterized in that: The preparation of the SnS thin film by electrochemcial deposition uses FTO as the substrate, prepares a composite electroplating solution, adopts a three-electrode system, uses an Ag / AgCl electrode as the reference electrode, a platinum wire as the counter electrode, and a conductive substrate as the working electrode, with a deposition potential of -0.65 V and a deposition time of 70 min.

6. The method for improving the efficiency of a SnS thin film solar cell according to claim 5, characterized in that: The preparation of the composite electroplating solution is to add Na2S2O3 to deionized water, stir until completely dissolved, then add SnSO4 and continue to stir until completely dissolved, then add the composite complexing agent to form a composite electroplating solution, adjust the pH of the composite electroplating solution to 2.4 with dilute H2SO4, and finally let the composite electroplating solution stand for 70 min before it can be used.

7. A method for improving the efficiency of SnS thin film solar cells as described in claim 6, characterized in that: The dosage ratio of Na2S2O3, SnSO4, the composite complexing agent and deionized water is 0.5956 g:0.1716 g:10 mL:80 mL.

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