Film Preparation And Performance Research Of Cu-based And Bi-based Ternary Photovoltaic Materials

At present,the energy crisis and environmental pollution have become two major problems in social development.New energy technologies is an effective strategy to solve these two major problems.Solar cells are one of the important sectors of new energy technology.Throughout the development of solar cells,from silicon solar cells to copper-indium-gallium-selenium solar cells,to the more popular perovskite solar cells,which have been studied for decades.Due to the limitation of rare elements,copper indium gallium selenium is difficult to achieve large-scale promotion.Commercial applications of perovskite solar cells have been limited due to instability and toxicity of lead(Pb).Therefore,we believe that the development of new non-toxic and stable photovoltaic materials is the trend of solar cell development.Bi-based and Cu-based materials are the most widely studied non-toxic and stable photovoltaic materials,We studied the photoelectric properties of Ag Bi₃I₁₀ and Cu₂SnS₃.First,the study is Ag-Bi-I ternary system materials.Due to the existence of Bi³⁺,Bi-based materials often have larger absorption coefficients.Iodobismuthate compounds have attracted the attention of researchers in recent years because of their potential electrical and optical properties.Considering that most iodobismuthate compounds are low-dimensional materials and have a wide band gap,incorporating metal ions can help improve their semiconductor characteristics,thereby forming a new Bi-based material with a three-dimensional structure.We used Ag⁺to connect adjacent iodide-bismuthate units to form an AgBi₃I₁₀ material with a three-dimensional structure.Through the analysis of the AgBi₃I₁₀structure,the material is a three-dimensional structural material based on[AgI₆]and[BiI₆]octahedron connected by edge sharing.The crystal structure of AgBi₃I₁₀ belongs to the R3m space group,and its lattice parameters are a=4.3517(?)and c=20.804(?).The light absorption curve of the material shows that the band gap of the material is about 1.8 eV,and the light absorption coefficient of the material itself is about 10⁵ cm^-1.We combined the battery frame structure of TiO₂/Al₂O₃/Ni O/C to explore a solar cell based on Ag Bi₃I₁₀ material as a light absorbing layer.The device efficiency was 1.27%,the short-circuit current of the device was3.34 mAcm^-2,and the open-circuit voltage was 0.63 V,the fill factor is 60%.The Ag Bi₃I₁₀material has good thermal stability and air stability,and the stability of the device is also very ideal.Our research shows the possibility of using a new metal halide structure in solar cells.The photovoltaic performance of the device is still in the development stage.It is believed that in-depth research on materials will improve the efficiency of the device.In addition,Cu-based materials are also a type of non-toxic and stable material systems that have been studied a lot.Currently,the most representative of non-toxic and stable high-efficiency photovoltaic materials is copper indium gallium selenium material.Researchers have used zinc and tin to replace the rare elements of indium and gallium,hoping to develop new materials with high-efficiency photoelectric characteristics similar to copper,indium,gallium,and selenium.Cu₂ZnSnS₄(CZTS)was born based on this research.Because the synthesis process of CZTS is complex and the stable phase region is narrow,the existence of secondary phases is often accompanied by the process of preparing CZTS.There are many types of defects and it is difficult to improve the efficiency of the device.Due to the unfavorable heterogeneous phase of ZnS that often occurs during the preparation of CZTS,the researchers considered removing the Zn component in CZTS to form only three elements of Cu₂SnS₃(CTS).CTS is considered as a potential candidate for non-toxic stable photovoltaic materials.In order to develop sustainable photovoltaic materials in the highly competitive power generation market,multiple parameters should be considered,such as cost,resource availability,material selection,and environmental constraints during processing.Most of the preparation of CTS films requires high vacuum deposition technology.Our research content is to develop a low-cost,high-efficiency non-vacuum deposition process(ball milling method)to prepare the initial film,then the initial film was moved to a tube furnace for sulphurisation to complete the preparation of CTS film.The sulphurisation process is a key stage in the synthesis of CTS films.During the preparation of CTS films,we systematically studied the effects of synthesis conditions(sulphurisation temperature,atmosphere,and time)on CTS films.We use an environmentally friendly ball milling method to grind Cu₂O and SnO,two stable metal oxides.The suspension is 90 wt%deionized water water+10 wt%isopropanol.Through the study of the various synthesis conditions in the sulphurisation process,we found that each condition has a greater impact on the preparation of CTS films.The research shows that the ambient gas conditions of the tube furnace are 400mbar Ar+100mbarH₂/N₂,and the sulphurisation temperature and time are 530^oC and 30minutes,respectively.It is beneficial to prepare a thin film with a dense surface and a single monoclinic phase structure.In view of the poor quality of CTS films,we explored the effect of the Surfynol?^R104PA surfactant added to the precursor solution on the film quality.Studies have shown that the addition of a small amount of surfactant is beneficial to improve the quality of CTS films.