| With the accelerated industrialization and the growing population,the demand for energy is increasing.In order to avoid the overuse of fossil fuels,mankind urgently needs to find a new energy source that can replace fossil fuels.Solar energy is a clean,environmentally friendly and widely distributed renewable energy source.In recent years,the development and utilization of solar energy has been of great significance in promoting the development of renewable energy worldwide.Solar cell has also become an important way to utilize solar energy,among which,copper-zinc-tin-sulphide(CZTS)solar cells are of great interest due to their simple preparation method,low cost and high light absorption coefficient.The highest photoelectric conversion efficiency of the cell can reach 32.8%,is a very promising new thin film solar cells.The main factors limiting the industrialization of CZTS solar cells are the complicated preparation process,expensive production cost,toxicity of the buffer layer material and the energy band shift between the absorber layer,etc.There are various methods for the preparation of CZTS absorber layer,which can be divided into two main types,one is the vacuum method and the other is the non-vacuum method.The vacuum method requires expensive equipment and high requirements for experimental conditions,so the solution method,which is simple to operate,inexpensive and has high raw material utilization,has rapidly gained the attention of researchers and developed rapidly.At present,the highest certified efficiency of CZTS solar cells 13%,the method of the absorbing layer preparation is the solution method.Therefore,the solution method in the development of CZTS solar cells has a broad prospect.Meanwhile,for the buffer layer,researchers are also trying various cadmium-free or cadmium less materials to replace the traditional cadmium sulfide buffer layer.Accordingly,this thesis will use the solution method to prepare the absorbing layer and buffer layer of CZTS solar cells,then examine the relationship between materials and device performance.(1)CZTS sol was prepared by using Cupric oxide,zinc oxide and stannous oxide as metal sources,thioglycolic acid and ethanolamine solution system,and the optimal pretreatment temperature of 320 ℃ was obtained by TG analysis.Then,the precursor solution was annealed and selenized for several times to prepare CZTSSe thin film,and then XRD analysis was conducted.The crystal structure is zincite structure,along the preferred orientation of(112)crystal face.The optical band gap of the film is 1.03 e V,and the film is compact without holes.(2)The complexes of cadmium ethylxanthate and zinc butylxanthate were prepared by the solution method.The optimum thermal decomposition temperature was investigated by thermogravimetric analysis and the products were characterised in terms of their basic structure.After doping them in different proportions,the solid solution of Znx Cd1-x S was prepared by the method of thermal decomposition of xanthate complex.Then,Znx Cd1-x S was applied to the buffer layer of copper-zinc-tinsulfuide solar cells and its properties were characterized.The results showed that Zn0.3Cd0.7S was the most efficient buffer layer,with the highest efficiency of 2.21%.(3)The indium ethyl xanthate complex was prepared by solution method.The crystal structure of In2S3 product at thermal decomposition temperature was investigated by thermogravimetric analysis,and the morphology of the product was characterized.Then,the In2S3 prepared by thermal decomposition xanthic acid complex was applied to the buffer layer of CZTS solar cell,and the influence of In2S3 prepared at different thermal decomposition temperatures as buffer layer on the performance of the battery device was explored.The results showed that the efficiency of the battery device was the highest at 250 ℃,and the highest efficiency was 1.71%. |
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