Facile Sb2Se3 and Se co-selenization process improves the performance of Cu2ZnSnSe4 solar cells

Selenization is effective to fabricate high-efficiency kesterite Cu2ZnSnSe4 (CZTSe) solar cells that facilitates the composition modification, crystallization enhancement, and bandgap adjustment. The incorporation of Sb into CZTSe absorbers can further boost the device efficiency mainly due to promoting the grain growth of CZTSe absorber. Here we report a Sb2Se3 and Se co-selenization process that significantly improves the quality of CZTSe absorber layers. This strategy enables the increase of CZTSe grain size and elimination of pinholes. We find that Sb is uniformly distributed in the absorber layer. When the Sb/(Cu + Zn + Sn) ratio is tuned to 6.67‰, the CZTSe solar cell exhibits the best device performance with an efficiency up to 9.64%, over 40% higher than the traditional selenization process. Our work provides a new route for enhancing the device efficiency of CZTSe solar cells.