Reducing Agents for Improving the Stability of Sn-based Perovskite Solar Cells.

Organic-inorganic hybrid perovskite solar cells (PSCs) have aroused tremendous research interest for their high efficiency, low cost and solution processability. However, the involvement of toxic lead in state-of-art perovskites hinders their market prospects. As an alternative, Sn-based perovskites exhibit similar semiconductor characteristics and can potentially achieve comparable photovoltaic performance in comparison with their lead-based counterparts. The main challenge of developing Sn-based PCSs lies in the intrinsic poor stability of Sn2+ , which could be oxidized and converted to Sn4+ . Notably, introduction of SnX2 (X=Cl, Br, I) additive becomes indispensable in the fabrication process, which highlights the importance of incorporating a reducing agent to improve the device stability. Additionally, efforts are made to utilize other reducing agents with different functions for the further enhancement of device performance. Currently, Sn-based PSCs could attain a record efficiency over 10% with great stability. In this review, we present the recent progress on reducing agents for improving the stability of Sn-based PSCs, and we hope to shed light on the challenges and opportunities of this research field.