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

Abstract The low toxicity and a near‐ideal bandgap endow tin (Sn)‐based perovskite solar cells (TPSCs) promising future in photovoltaic technologies. However, general the Sn‐based perovskites suffer from poor resistance to oxidation fast crystallization dynamics, resulting fill factors (FFs) power conversion efficiencies (PCEs). Herein, strategy improve performance of TPSCs by incorporating 2‐(2‐aminoethyl)–2‐thiopseudourea dihydrobromide (AET) into is proposed. AET interacts strongly with perovskites, thus effectively inhibits Sn 2+ 4+ slows down process. As result, achieve high FF 80.26% PCE 13.55%. Notably, this value represents highest reported field narrow bandgaps. Furthermore, encapsulated demonstrate good stability, maintaining 80% their initial over course 700 h.