Effects of copper content on properties of CZTS thin films grown on flexible substrate

Abstract

In this work, Cu2ZnSnS4 (CZTS) thin films on the flexible molybdenum foils were fabricated by vacuum-based magnetron sputtering and followed by annealing in the sulfur vapor. The effects of copper content on CZTS films’ structures and properties were studied using X-ray diffraction (XRD), Raman scattering, energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), and UV–Vis spectroscopy techniques. According to the experimental results, the strong peak in XRD pattern along (112) plane confirms the kesterite crystal structure of CZTS thin films. A suitable increase of the copper content can improve the crystallinity of the CZTS thin films. However, the continued increase in copper content can lead to the presence of Cu2S and Cu3SnS4 phases in sulfurized CZTS thin films. Furthermore, the performances of flexible CZTS thin films after repeated bending were also explored. In our case, no cracks were observed by SEM, but a fold appeared in the surface. Also, increasing copper content makes the fold less obvious.