Effect of potassium doping for ultrasonic sprayed Cu₂SnS₃ thin films for solar cell application

In this work, potassium-containing Cu₂SnS₃ thin films (K_xCu_2−xSnS₃) were fabricated by a simple and low-cost ultrasonic spray pyrolysis method on glass substrates with different potassium doping concentration. Effects of various potassium concentrations on the structural, morphological and optical properties of the films were systematically investigated. The results indicate that potassium doping can well enhance the growth of particle size and decrease the band gap of the film from to 1.55 to 1.26 eV. Solar cell devices with a structure of glass/FTO/K_2−xCu₂SnS₃/CdS/ZnO/AZO have been prepared and obvious solar cell device performance improvement has been observed by 2 at% potassium doping. This potassium-containing Cu₂SnS₃ thin films could be a promising absorber material for high efficiency solar cell.