The Preparation Of CZTS Thin Films And CZTS Thin Film Solar Cells Based On Flexible Molybdenum Foils

Copper-zinc-tin-sulfur(Cu2ZnSnS4,CZTS)is considered to be one of the most promising solar cell materials because of its high absorption coefficient(>104 cm-1),ideal direct band gap(1.4-1.5 eV)and environmental friendliness.Thin film solar cells based on flexible substrates have the advantages of low cost,soft material,safety and environmental protection,which meet the market demand for flexible solar cells.Among them,the molybdenum foils,due to the advantages of high temperature resistance,good mechanical strength,compatibility with the thermal expansion coefficient of CZTS thin films,become one of the best choices of the substrates of flexible solar cells.In this thesis,CZTS thin films were prepared on flexible molybdenum substrates by sol-gel method and subsequent sulfurization method.The effects of sulfurization on the phase structure,morphology,composition and photoelectric properties of CZTS thin films were studied.The J-V characteristics of CZTS thin film solar cells were studied.The main results are as follows:1.The influences of sulfurization temperature,sulfurization ramping rate and thickness on the properties of CZTS thin films were studied.Study shows that,with the increase of sulfurization temperature,phase structure of CZTS thin films changes greatly.Density and smoothness of the films show better first and then worse.The optical band gap and resistivity of the CZTS thin films decrease first and then increase trend.With the increase of sulfurization ramping rate,the crystallinity and grain uniformity of CZTS thin films show better first and then worse.The band gap and resistivity of the films first decrease and then increase.As the thickness increases,the smoothness and density of the films become better.When the thickness is 1.5 ?m,the sulfurization temperature is 500 ? and the sulfurization ramping rate is 10 ?/min,the band gap of CZTS thin film is 1.42 eV and the resistivity is 4.31 ?·cm,whose photoelectric performance is suitable for the demand of absorber of solar cells.2.The influences of sulfurization temperature,sulfurization ramping rate and thickness of CZTS absorber layer on the J-V characteristics of CZTS thin film solar cells were investigated.The results show that,when thickness,sulfurization temperature,sulfurization ramping rate of CZTS thin films are 1.5 ?m,500 ?,10 ?/min,respectively,the CZTS thin film solar cell has the best optical response,and its efficiency is 2.25%.3.The Cd-free and environmentally friendly CZTS thin film solar cells based on the flexible molybdenum substrates were explored,and the buffer layer was In2S3 thin film.The results show that the prepared solar cell has light response,but the efficiency is only 0.37%.