Fabrication And Doping Modification Of Cu₂ZnSnS₄ Thin Films

Copper-zinc-tin-sulfur(Cu₂ZnSnS₄,abbreviated as CZTS)thin film has good photoelectric properties,and its forbidden band width is very close to the optimal forbidden band width(1.5eV)required for semiconductor solar cells,and has a large light absorption coefficient(>10⁴cm^-1),the theoretical conversion efficiency is as high as32.4%.At the same time,the elements in the CZTS are rich,and they are safe,non-toxic and non-polluting,and have good market prospects.At present,CZTS has become one of the candidate materials for replacing the Copper-indium-gallium-selenide(CIGS)solar cell absorber layer.Research shows that CZTS and silicon-based solar cells combine to form a laminated battery to compensate for the current stagnant efficiency of silicon-based batteries.It may be an ideal material for future silicon-based stacked photovoltaic cells.In this paper,a CZTO precursor film was prepared on a molybdenum glass substrate by a sulfide nano-ink coating and vulcanization method.The CZTS film was optimized by studying the post-vulcanization process parameters,and a CZTS thin film solar cell with 2.08%photoelectric conversion efficiency was obtained by device characterization.Then,the CZTSSe film was prepared by studying the process parameters of selenization doping using standard sulfide samples,and the CZTS film was doped and modified.Finally,a CZTSSe thin film solar cell with 4.11%photoelectric conversion efficiency was obtained by preparing the device.The results of this paper are as follows:(1)The coprecipitation parameters for the preparation of CZTO precursors were studied.The effects and particle size of Cu-Zn-Sn hydroxide of pH,coprecipitation temperature and PVP content were studied.The optimal conditions are:pH is 9.5,coprecipitation temperature is 40?,PVP content is 0.5%;the influence and particle size of composite oxide of calcination temperature and holding time of CZTO precursor were studied,and the calcination temperature was 550?,the holding time was 2h.(2)Cu-Zn-Sn composite oxide nanoparticles were prepared by co-precipitation method.Oxide nano-ink was prepared by spheroidal method.CZTS thin film was prepared by spraying on molybdenum glass substrate.Vulcanization annealing temperature,vulcanization insulation time and sulfur source temperature were studied.The influence of vulcanization annealing temperature,vulcanization insulation time and sulfur source temperature on the composition,morphology and phase structure of CZTS thin film obtained the optimum vulcanization annealing temperature of 580?,the optimum holding time of 60min and the optimum sulfur source temperature of 200?;On this basis,a CZTS thin film solar cell with a photoelectric conversion efficiency of2.08%was prepared.(3)Based on the above-mentioned standard sulfide samples,the process parameters of selenization doping were studied.The composition,phase structure and morphology of CZTSSe thin film were studied by selenization doping process(selenization doping temperature,selenization doping insulation time and selenium source temperature).The experimental results show that the optimal selenization doping process is:the temperature of the selenization sample side is 550?,the holding time is 60 min,and the selenium source temperature is 400?.Finally,a CZTSSe thin-film solar cell with a photoelectric conversion efficiency of 4.11%was prepared by optimized process.The open circuit voltage,short-circuit current and fill factor were 623mV,16.02mA/cm2 and 41.2%,respectively.