Additive Engineering-Assisted Perovskite Crystallization Modulation and In Situ Buried Interface Healing for Stable and Efficient Planar CsPbI 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 perovskite precursor to simultaneously reduce perovskite defects through modulating CsPbI perovskite crystallization and heal the buried interface through in situ forming a ABSA dipolar interlayer. The interaction of the ABSA molecule with CsPbI precursor components hinders CsPbI perovskite crystallization, resulting in forming a compact and smooth CsPbI perovskite film with reduced defects and enhanced crystallinity. Meanwhile, ABSA molecules are excluded from the CsPbI perovskite crystal and pushed downward during the perovskite crystallization process. Consequently, ABSA molecules accumulate at the bottom surface of the CsPbI 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 cell with the ABSA additive demonstrates a largely improved performance with a power conversion efficiency up to 17.89%. In particular, the unencapsulated CsPbI cell maintains over 90% of the original efficiency in ambient air after 480 h of storage, indicating superior long-term stability.