Effect of post-sulfurization on the composition, structure and optical properties of Cu2ZnSnS4 thin films deposited by sputtering from a single quaternary target

► CZTS films were deposited directly from a CZTS target by sputtering process. ► The internal compressive stress relaxes in post-annealed CZTS films. ► The band gaps of post-annealed CZTS films are smaller than those of as-deposited.