Preparation of 4.8% efficiency Cu2ZnSnSe4 based solar cell by a two step process

Zn-rich Cu
₂
ZnSnSe
₄
(CZTSe) films were prepared by a two step process. We have varied the Zn/Sn ratio from 1.24 to 1.73 and analyzed the effects of precursor composition and annealing temperature (between 425° C and 550° C) on the morphological, structural, and optoelectronic properties of the films. Raman scattering measurements show the presence of ZnSe as the main secondary phase in the films, as well as SnSe at the back region of the films processed with lower Zn-excess values and annealed at lower temperatures. The effect of the different secondary phases on the optoelectronic properties is discussed. In a first optimization we obtain as a preliminary result a 4.8% efficiency solar cell.