Synergistic Buried Interface Optimization via Aminothiophenol for Carbon‐Based CsPbI ₃ Perovskite Solar Cells With 19.81% Efficiency

Carbon‐based hole transport layer (HTL)‐free perovskite solar cells (C‐PSCs) show great promise due to simple fabrication and cost‐effectiveness. However, using TiO 2 as the sole carrier transport layer causes defects at the buried interface with perovskite, affecting photogenerated carrier extraction and transfer. This study introduces aminothiophenol (ATP) as a buried interface additive to passivate defects and stabilize CsPbI 3 films. Simulations and experiments confirm ATP anchors on TiO 2 via ─SH to passivate oxygen vacancies, while ─NH 2 and ─SH synergistically passivate lead vacancies and uncoordinated Pb 2+ . Furthermore, this modification improves energy‐level alignment, electron extraction, perovskite crystallinity, and carrier lifetimes. Consequently, the optimized 3‐ATP‐modified device achieves a PCE of 19.81%, among the highest reported for all‐inorganic C‐PSCs and retains over 90% of its initial PCE after 1000 h in ambient air with <20% humidity.