Alleviating the Crystallization Dynamics and Suppressing the Oxidation Process for Tin-Based Perovskite Solar Cells with Fill Factors Exceeding 80 Percent

The low toxicity and a near-ideal bandgap endow tin (Sn)-based perovskite solar cells (TPSCs) a promising future in photovoltaic technologies. However, in general the Sn-based perovskites suffer from poor resistance to oxidation and fast crystallization dynamics, resulting in low fill factors (FFs) and power conversion efficiencies (PCEs). Herein, a strategy to improve the performance of TPSCs by incorporating 2-(2-aminoethyl)-2-thiopseudourea dihydrobromide (AET) into the Sn-based perovskites is proposed. AET interacts strongly with the Sn-based perovskites, and thus effectively inhibits the oxidation from Sn2+ to Sn4+ and slows down the crystallization process. As a result, the TPSCs with AET achieve a high FF of 80.26% and a high PCE of 13.55%. Notably, this FF value represents the highest reported in the field of TPSCs with narrow bandgaps. Furthermore, encapsulated TPSCs demonstrate good stability, maintaining 80% of their initial performance over the course of 700 h. In this work, 2-(2-aminoethyl)-2-thiopseudourea dihydrobromide (AET) is introduced into the tin (Sn)-based perovskite to suppress its oxidation process from Sn2+ to Sn4+ and alleviate its crystallization dynamics. As a result, an impressive fill factor of 80.26% is achieved for the Sn-based perovskite solar cells (TPSCs) with AET. Moreover, encapsulated TPSCs maintain 80% of their initial performance over 1 month.image