Soy protein enables stable perovskite solar cells by defect passivation and ion migration suppression

Passivating agents have been explored for enhancing the stability of perovskite solar cells (PSCs). However, previous investigations have been limited to high purity agents, resulting in high costs and restricted material availability. In this study, we investigate abundant and naturally occurring soy protein, which offers abundant functional groups, making it an ideal candidate. Soy protein facilitates the passivation of perovskite via coordination with Pb²⁺ and hydrogen bonding with I⁻, fostering high-quality perovskite films with reduced defect density and suppressed ion migration, further preventing phase transition and crystal structure collapse of the perovskite in high humidity and thermal stress environments. Consequently, enhanced photovoltaic response and significantly improved stability are exhibited, and thus this study provides a new passivation approach using natural materials toward efficient and stable PSCs. © The Royal Society of Chemistry 2025.