A Universal Perovskite/C60 Interface Modification via Atomic Layer Deposited Aluminum Oxide for Perovskite Solar Cells and Perovskite–Silicon Tandems

Abstract The primary performance limitation in inverted perovskite‐based solar cells is the interface between the fullerene‐based electron transport layers and the perovskite. Atomic layer deposited thin aluminum oxide (AlO X ) interlayers that reduce nonradiative recombination at the perovskite/C 60 interface are developed, resulting in >60 millivolts improvement in open‐circuit voltage and 1% absolute improvement in power conversion efficiency. Surface‐sensitive characterizations indicate the presence of a thin, conformally deposited AlO x layer, functioning as a passivating contact. These interlayers work universally using different lead‐halide–based absorbers with different compositions where the 1.55 electron volts bandgap single junction devices reach >23% power conversion efficiency. A reduction of metallic Pb 0 is found and the compact layer prevents in‐ and egress of volatile species, synergistically improving the stability. AlO X ‐modified wide‐bandgap perovskite absorbers as a top cell in a monolithic perovskite–silicon tandem enable a certified power conversion efficiency of 29.9% and open‐circuit voltages above 1.92 volts for 1.17 square centimeters device area.