Abstract
► CZTS thin films were deposited by ultrasonic spray pyrolysis technique. ► The deposition rate shows two thermal activation energies. ► Films have a kesterite hexagonal structure with (112) preferential orientation. ► Stannate ZnSnO3 is present as a secondary phase.
Cu2ZnSnS4 (CZTS) thin films were deposited by ultrasonic spray pyrolysis technique. The substrate temperature was varied from 280 to 360°C in order to investigate its influence on CZTS films properties. The deposition rate shows two activation energies 0.16 and 0.53eV, respectively at low and high substrate temperatures. This indicates that CZTS deposition by spray pyrolysis passes by two different processes with increasing temperature substrate. The temperature 320°C corresponds to the transition between these two processes. The X rays diffraction (XRD) analysis indicated that the deposited films have a kesterite hexagonal structure with (112) preferential orientation and a crystalline size, ranged from 30 to 52nm with increasing substrate temperature. Stannate ZnSnO3 is present as a secondary phase. The presence of this secondary phase causes films optical band broadening. Broad emissions at around 1.27eV was observed in the photoluminescence spectrum measured at 77K, it is accompanied with a small peak located at 1.75eV due the presence of zinc stannate phase ZnSnO3.