Modulating Residual Lead Iodide via Functionalized Buried Interface for Efficient and Stable Perovskite Solar Cells

Sufficient lead iodide (PbI2) in perovskite films effectively passivates defects and enhances device performance. However, excess large-grained PbI2 clusters tend to be randomly distributed in the perovskite layer, which mitigate the positive effect of the PbI2. Here, we first modulated the distribution and size of PbI2 clusters by functionalizing the buried interface of 4,4′-diaminodiphenyl sulfone hydroiodide (DDSI2). As a multifunctional modifier, DDSI2 can optimize the energy level of tin oxide (SnO2) and passivate the buried interface defects via −NH3+ and S═O functional groups. Moreover, the hydrogen bonding and coordination between DDSI2 and perovskite retard the crystal growth rate and alleviate the lattice stress, thereby improving the quality of the perovskite and modulating the distribution of PbI2. Consequently, the DDSI2-modified device displays a power conversion efficiency of 24.10% and a storage stability of 1800 h. We demonstrate a unique strategy for the rational control of PbI2 for efficient and stable perovskite solar cells.