Abstract
In this study, the Cu2ZnSnS4 (CZTS) films were grown by a two-step process using new ZnSn/Cu stacked precursors that were prepared by sputtering and subsequently annealed at 570 °C under a sulfur atmosphere. By controlling the composition ratio of the CZTS films, we increased the photocurrent of the CZTS thin-film solar cell employing the stacked bi-layer from 13.9 mA/cm2 to 19.5 mA/cm2 and increased the solar cell's efficiency from 3.9% to 5.3%. These increases are attributed to the formation of a Cu-poor CZTS film that resulted in increased formation of copper vacancies that give rise to shallow acceptors in the CZTS.