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 TiO 2 and CsPbI 3 simultaneously by reacting with dangling hydroxyl groups on TiO 2 surfaces and passivating the defects of CsPbI 3 films. In addition, the introduction of ATPA results in cascade energy‐level alignment between the perovskite and TiO 2 electron‐transporting layer (ETL) to improve the electron extraction property. Based on the ATPA‐modified TiO 2 substrates, optimized CsPbI 3 perovskite solar cells (PVSCs) deliver the highest power conversion efficiency (PCE) of over 18% with suppressed hysteresis. Moreover, the unencapsulated TiO 2 /ATPA‐based devices exhibit much better long‐term stability and photostability than the only TiO 2 ‐based devices.