Achieving highly efficient kesterite solar cells using simultaneous surface Ge substitution and rear interface engineering strategies

The progress in the device performance of kesterite-based thin-film solar cells (TFSCs) have been stagnant due to unstable rear contact properties and large open circuit voltage (Voc)-deficit characteristics. Several individual strategies have been developed to solve these issues. In this work, we investigate the simultaneous impact of Ge substitution and rear interface engineering with a MoOx intermediate layer on Mo back contact. The simulta-neous application of both strategies delivers a synergetic effect, improving microstructure, Voc-deficit, band-tailing states, and device parameters and reducing Sn-related deep-level defects, resulting in enhanced power conversion efficiency (from 8.1 to 11.55%). This effective strategy offers new insight and a way to solve unstable rear contact properties and large Voc-deficit, further improving the device performances of kesterite-based TFSCs.