Effect of Annealing on Physical Properties of Cu2ZnSnS4 (CZTS) Thin Films for Solar Cell Applications

Cu2ZnSnS4 (CZTS) thin films were prepared by directly sputteringCu (In,Ga)Se2 quaternary target consisting of (Cu: 25%, Zn: 12.5%, Sn; 12.5%and S: 50%). The composition and structure of CZTS layers have beeninvestigated after annealing at 200 0C, 350 0C and 500 0C under vacuum. Theresults show that recrystallization of the CZTS thin film occurs and increasingthe grain size with a preferred orientation in the (112) direction was obtained. TheRaman spectra showed the existence of crystalline CZTS phase after annealing.Optical transmission spectra were recorded within the range 300-900 nm. Theenergy band gap (Eg) of the CZTS thin films was calculated before and afterannealing from the transmittance spectra using Beer-Lambert’s law. Results showthat Eg is dependent on the annealing temperature. The optical band gap of CZTSalso varied from 1.57 eV to 1.31 eV with increase in the annealing temperaturefrom 200 0C min to 500 0C.