Preparation Of CuInS₂ And ZnS Thin Films Materials For Solar Cells By Chemical Deposition

With the development of economy, energy has become the principle problem which many countries are faced with in the world. Research and development of the clean renewable energy has become the critical concern of international academic circles. Solar energy is inexhaustible and free from pollution. From 1950s, research and application of solar cell is increasingly wide. Chalcopyrite compound copper indium disulfide (CuInS₂) existed at low temperature is one of the most promising candidates as absorber materials for photovoltaic applications due to its' direct band gap of 1.3-1.7eV, high absorption coefficient of 10^-5cm^-1 which makes it only need thin thickness to absorb most of the sunlight. At present, preparation process of CuInS₂ thin film is complicated, which costs too much and badly affects the industrialization of CuInS₂ solar cell.ZnS belongs toâ…¡-â…¥with direct band gap of 3.6-3.8eV, it is almost transparent to visible light and can grow under low temperature. It is a good buffer layer as a substitute of CdS for thin films solar cells. Now ZnS thin film is mainly prepared by Chemical Bath deposition method, but fabrication process is not mature and repeatability is not good.In this thesis, CuInS₂ and ZnS thin films used for solar cell are prepared by chemical method which is low cost and need not vacuum equipment, the structure and property of the films are studied, the growth mechanism of the film is analyzed. Fabrication of CuInS₂ thin film by Chemical Bath deposition in acid conditions and Electroless plating method is mainly studied in this thesis. Fabrication of CuInS₂ thin film by Chemical Bath deposition in acid conditions can restrain the generation of impurities and improve the purity of the film. These two methods both need not vacuum equipment and cost low, which is good to the industrialization of CuInS₂ solar cell. There are some other strongpoints about these two methods, such as process parameters can be easily controlled, the film is uniform and well crystallized. The main creative achievements are showed as follows: 1. Related parameters are optimized and stable process for preparation of CuInS₂ thin film by Chemical Bath deposition is obtained, growth mechanism of thin film prepared by Chemical Bath Deposition is also analyzed; the effect of substrate and complexing agent on the deposition of the film is studied, it is found that deposition on the ITO substrate and with complexing agent can make the film compact; effect of the heat treatment on the crystallization and optoelectrical property of the film is also investigated.2.CuInS₂ thin film is prepared by multi-step Chemical Bath deposition, related parameters are optimized. Effect of substrate on the In₂S₃ film surface morphology and adhesion between In₂S₃ film and the substrate is studied, it is discovered that rough substrate can make the adhesion better, but different substrates have little effect on the In₂S₃ film surface morphology; effect of surface active agent on the deposition of In₂S₃ thin film is investigated, it is found that surface active agent can make the film compact; effect of the heat treatment on the crystallization and optoelectrical property of the film is studied, it is showed that the the anneal effect on the film by multi-step Chemical Bath deposition has similar discipline with the one-step method.3. Effect of reducing agents on the preparation of Cu and In film by Electroless Plating method is studied, related parameters are optimized and stable process for preparation of Cu and In thin film by Electroless Plating method is obtained; effect of different anneal methods on the preparation of CuInS₂ film by Electroless Plating method are studied, it is found that there are many holes on the surface of the CuInS₂ film annealed by one-step sulfuration, but the film annealed by two-step sulfuration is compact.4. The transmisson of the ZnS film prepared by chemical bath deposition is more than 90% at the range of visible light, the film with band gap of 3.8eV is very suitable to be used as the buffer layer of CuInS₂ thin film solar cell.