Investigation of gradient band gap in Cu2ZnSnS4 thin films with residual strain

Abstract

This study investigates the change in the band gap of Cu2ZnSnS4 (CZTS) thin films under a gradual change in the residual strain of the thin films. Two CZTS thin film samples are fabricated at different initial substrate temperatures before annealing. X-ray diffraction results are obtained at various incidence angles, and the residual strains at the incidence angles are obtained from the Williamson–Hall plot. The larger the mean residual strain of the CZTS thin films, the greater are the redshift and full width at half maximum of the main Raman peak position. Results of Tauc plot analysis show that the CZTS thin film samples exhibit a gradient band gap. The sample with a wider distribution of the residual strain shows a greater band gap variation.