Ag and Ge dual-cation substitution in Cu2SnS3 induced improvement of power conversion efficiency

In recent years, there is significant interest in Cu 2 SnS 3 (CTS) thin film solar cells owing to the eco-friendly nature and abundant elemental composition. However, the efficiency prepared in laboratory settings for these solar cell remains relatively low, primarily due to serious open-circuit voltage losses. Cation substitution is one of the strategies to alleviate this problem. In this work, Ag and Ge dual-cation substitution in CTS is proposed, which occupy partial Cu and Sn lattice sites respectively. Investigation reveals that substituting Cu with part Ag increases the band gap slightly, promotes grain growth, and improves crystallinity of CTS films. Simultaneously, Ge incorporation shifts the conduction band upwards to some extent, while reducing grain boundaries, due to increasing the grain size. As a result, the incorporation of 6 % Ag resulted in an optimal efficiency (PCE) of 2.78 %. Furthermore, employing dual-cation substitution with 6 % Ag and 6 % Ge is employed, the CTS device achieved an optimal efficiency of 3.15 %. This work develops the synergistic effect of Ag and Ge dual-cation substitution in CTS device and confirms that this approach can improve device performance, thus providing new research ideas for advancing the development of CTS device.