Research On Properties Of Solution Method Based Cu₂SnS₃ Thin Films For Solar Cells Application

Cu₂SnS₃?CTS?ternary semiconductor has attracted considerable research attention as a promising absorber material for thin film solar cells,due to the non-toxic and earth abundant component elements,a direct band gap in the range of 0.92 to 1.35 eV,and a light absorption coefficient of over 10⁵ cm^-1.The development of low cost preparation technology for achieving high conversion efficiency is the key prerequisite towards large-scale commercial applications of CTS solar cells.Considering the current problems in the preparation of CTS thin film solar cell devices,this dissertation proposes the preparation of CTS absorber film through a low cost,safety and environmental friendly chemical solution method basing on metal salt and thiourea precursors.The effects of preparation conditions on the composition,structure and properties of CTS film were studied systematically.Furthermore,basing on the prepared CTS thin films,CTS thin film solar cell was successfully fabricated.The main contents and results are presented as follows:1.CTS thin films were successfully fabricated based the metal salt and thiourea aqua.The effect of sulfurization conditions?sulfurization temperature,sulfur power dosage and sulfurization time?on the quality and photoelectric properties of CTS film were investigated systematically.The results indicate that increase of the sulfurization temperature can improve the crystallinity of CTS film and induce the transformation of CTS crystal structure;excess sulfur powder supply promotes the growth of CTS grains effectively;the prolonged sulfurization time decreases the carrier concentration and enhances the mobility of CTS.The CTS thin film solar cell with photoelectric conversion efficiency of 2.61%was prepared under the optimized condition with a sulfurization temperature of 580 ^oC,sulfur powder supply of 200 mg and sulfurization time of 20 min.2.In order to further simplify the preparation process of CTS thin film,the CTS films were prepared without sulfurization.The effects of sulfur to metal cations ratios?S/M?in precursor solution and annealing temperatures on Cu₂SnS₃ thin films have been studied in detail.The results indicate that increasing S/M ration is helpful to reduce the voids and secondary phase in the CTS film,while decreasing the annealing temperature is found effective to reduce the over loss of Sn element and S element.A pure-phase CTS thin film with large grain size and smooth surface can be obtained under 540?with S/M=6.The obtained pure-phase CTS exhibits a band gap of¹.02eV.