Interfacial Modification through a Multifunctional Molecule for Inorganic Perovskite Solar Cells with over 18% Efficiency

A highly effective interface engineering approach uses a multifunctional molecule, 5‐amino‐2,4,6‐triiodoisophthalic acid (ATPA), to anchor on TiO2 and CsPbI3 simultaneously by reacting with dangling hydroxyl groups on TiO2 surfaces and passivating the defects of CsPbI3 films. In addition, the introduction of ATPA results in cascade energy‐level alignment between the perovskite and TiO2 electron‐transporting layer (ETL) to improve the electron extraction property. Based on the ATPA‐modified TiO2 substrates, optimized CsPbI3 perovskite solar cells (PVSCs) deliver the highest power conversion efficiency (PCE) of over 18% with suppressed hysteresis. Moreover, the unencapsulated TiO2/ATPA‐based devices exhibit much better long‐term stability and photostability than the only TiO2‐based devices.