| Solar energy is a kind of clean and renewable energy. It belongs to the environmentally friendly energy and is also the most abundant energy on the earth. Therefore, the study of the application of solar energy has become the main development direction of human energy in the future. And the solar cell is one of the important ways to realize the application of solar energy. Compared to the traditional energy, such as thermal power generation, solar energy has the disadvantages of higher cost. The key to solve this problem is to improve the photoelectric conversion efficiency of solar cells and reduce the production cost of solar cells.The tin sulfur compounds belong to IV-VI group semiconductors and the materials have the excellent semiconductor performance. Among the Ⅳ-Ⅵ group semiconductors, SnS has attracted significant attention due to its layer property and being a much more cost-effective and low-toxicity compound compared with other similar compounds such as GeS, PbS. SnS is a narrow band gap compound in IV-VI group semiconductors and its band gap varies with the preparation techniques and deposition parameters. It has both p-type and n-type conductivity depending on the atomic ratio of Sn to S and possesses high absorption coefficient (a>104cm-1). The theoretical conversion efficiency of the solar cells fabricated with SnS thin film can reach25%. At present, tin sulphide is easy to be films and thus canbe reduce the cost. In addition, its constituent element S and Sn is abundant on the earth and also has a good environmental compatibility. So it has advantage in solar cell materials, especially for the use of abaorption material in solar cells.To realize the controllable preparation of films and industrialized production, this thesis is mainly focus on the reduction of preparation cost of tin sulfur films and optimizes the preparation process.(1) In this work, a modified PECVD method is proposed for the deposition of films with solid material as source materials. The use of solid source materials can greatly expand the application of PECVD, especially for films prepared with unavailable gas sources, and it also can be used to deposit films of higher complexity with a single system.(2) In the present work, SnS films are deposited from cost-effective and low-toxicity solid source materials by a modified version of the PECVD technique. Through studying the effect of radio-frequency power, sulfur source materials and substrates, the optimal conditions for the preparation were attained. The results show that the SnS films deposited at the radio-frequency power of150W, deposition temperature of400℃, annealing temperature of450℃shows high adsorption coefficient (a>105cm-1) and suitable band gap(1.5eV) and is very well-suited as absorption material.(3) By changing the deposition parameters, such as the molar ratio of S/Sn in source material, deposition temperature and the different kinds of sulfur source materials, SnS2films with nano-flower and nano-wall structures can be deposited without using any additives. The results show that the SnS2film deposited at the radio-frequency power of200W, deposition temperature of250℃, annealing temperature of350℃shows well optical performance and is suitable for use as window layers.(4) The method was used to optimize the conver efficiency was also studied in this thesis. In the experiment, the open circuit voltage, short circuit current, current density and fill-factor (FF) of FTO/n-SnS2/p-SnS/Ag are0.35V,7.54μA,0.1508mA/cm2and0.55, respectively. And the open circuit voltage, short circuit current, current density and fill-factor (FF) of FTO/n-SnS2(TiO2)/p-SnS/Ag are0.484V,7.52μA,0.1503mA/cm2and0.57, respectively. The results show that thin films solar cells based on SnS as absorber have been prepared successfully.In this thesis, the high quality SnS2and SnS films have been deposited by PECVD method and the optimum parameters also have been investigated. All the above work laid a good foundation for the preparation of the solar cells with high efficiency. |
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