Solution‐Processed SnO_<i>x</i> as a Hole‐Transporting Material for Stable Sn‐Based Perovskite Solar Cell

Sn‐perovskites are considered a suitable alternative to toxic Pb‐perovskites due to their low toxicity and optimum optoelectronic properties. However, high‐efficiency Sn‐based perovskite solar cells (Sn‐PSCs) typically use poly (3,4‐ethylenedioxythiophene):polystyrene sulfonic acid (PEDOT:PSS) as a hole‐transporting material (HTM), which limits their stability due to its acidic nature. This study introduces SnO X nanocrystals, synthesized through a synproportionation reaction of Sn 4+ with Sn 0 under mild conditions, as a replacement for PEDOT:PSS. X‐ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy analyses revealed that the Sn 0 reduces Sn 4+ by 38% and elevates the highest occupied molecular orbital to –5.70 eV, close to PEDOT:PSS, enabling HTM behavior. The perovskite films on SnO X exhibit improved grain size and crystallinity compared to PEDOT:PSS. The resulting SnO X ‐based Sn‐PSCs achieved a power conversion efficiency of 11.11%. They retained 90% of their efficiency after 1000 h of maximum power point tracking, indicating superior stability over PEDOT:PSS‐based devices.