Globally, research groups are investigating CZTS thin film via various deposition methods as an absorber layer for solar cells. The challenge lies in understanding the formation of a number of secondary phases during and after the synthesis of Cu2ZnSnS4 (CZTS) and its various different structural and optical defects. The present contribution shows an in-depth review of the works carried out so far by various research groups. This review also highlights the effect of deposition parameters on the optical properties of CZTS absorber.