Opto-Electronic Properties of Cu2ZnSnS4 Thin Films Grown by Ultrasonic Spray Pyrolysis

Cu 2 ZnSnS 4 (CZTS) films are deposited by ultrasonic spray pyrolysis technique for photovoltaic applications. The optoelectronic properties are studied by varying Zn and Sn compositions in the film. Films showed a tetragonal kesterite structure with preferential orientation along the (112) plane. The sample with the highest Cu concentration showed the lowest band gap of 1.46 eV. The grain size of the films is greater than 1 μ m. Temperature-dependent conductivity studies revealed the presence of defects such as V Cu , V S , V Sn , Cu Zn , Zn Cu , Zn Sn and Sn Zn in the films. The sample with a Cu/(Zn + Sn) ratio of 0.75 showed Cu-poor and Zn-rich composition and better opto-electronic properties. The sample has p -type conductivity with a resistivity of 12 Ω cm. A [V Cu –Zn Cu ] defect complex is identified in this sample along with a Zn Sn acceptor level which is favorable for solar cells.