Light induced phase change in Cu{sub 2−x}Zn{sub 1.3}SnS{sub 4} thin films

Cu{sub 2}ZnSnS{sub 4} and its alloy based thin film solar cells have shown better photovoltaic performance under Cu-poor and Zn-rich conditions. However, the effect of Cu-stoichiometry on the coexistence of kesterite (KS), stannite and/or partially disordered kesterite (PD-KS) phases and their influence on photovoltaic performance is not clearly understood. Raman studies were carried out on Cu{sub 2−x}Zn{sub 1.3}SnS{sub 4} (x = 0, 0.3, and 0.5) thin films by changing the intensity of the incident laser beam. It was observed that both Cu-stoichiometry and incident laser beam intensity induce a disorder in the system. Disorder induced transformation of KS (I4{sup ¯}) to PD-KS (I4{sup ¯}2m) is explained by Raman studies.