Tailoring the Interfacial Termination via Dipole Interlayer for High‐Efficiency Perovskite Solar Cells

Abstract The ionic nature of the organic‐inorganic hybrid perovskite material is prone to react with different functional groups. Here, a series of polar molecules with permanent dipole moments are designed to modify the perovskite surface termination. It is observed that proper interfacial design can significantly reduce trap state density for effective charge transfer. The energy level of the substrate can be adjusted by the magnitude and direction of the dipole moment. As a result, a high 24.54% photo‐electric conversion efficiency is reached by introducing pentafluoride benzene moieties with carboxylic functional groups. In addition, the humidity and heat stability of the perovskite device is obviously improved. This work demonstrates the importance of chemical interactions at perovskite termination and paves the way for further enhancing the performance of perovskite solar cells.