Additive Engineering-Assisted Perovskite Crystallization Modulation and In Situ Buried Interface Healing for Stable and Efficient Planar CsPbI 3 Perovskite Solar Cells

The charge recombination resulting from the numerous perovskite defects and the inferior buried interface remarkably deteriorates the performance of inorganic perovskite solar cells. Here, we introduce 4-aminobenzenesulfonic acid (ABSA) into the CsPbI 3 perovskite precursor to simultaneously reduce perovskite defects through modulating CsPbI 3 perovskite crystallization and heal the buried interface through in situ forming a ABSA dipolar interlayer. The interaction of the ABSA molecule with CsPbI 3 precursor components hinders CsPbI 3 perovskite crystallization, resulting in forming a compact and smooth CsPbI 3 perovskite film with reduced defects and enhanced crystallinity. Meanwhile, ABSA molecules are excluded from the CsPbI 3 perovskite crystal and pushed downward during the perovskite crystallization process. Consequently, ABSA molecules accumulate at the bottom surface of the CsPbI 3 perovskite and in situ form an ABSA dipolar interlayer, which effectively heals the buried interface and promotes interfacial charge transfer. As a consequence, the planar carbon-based CsPbI 3 cell with the ABSA additive demonstrates a largely improved performance with a power conversion efficiency up to 17.89%. In particular, the unencapsulated CsPbI 3 cell maintains over 90% of the original efficiency in ambient air after 480 h of storage, indicating superior long-term stability.