Room‐Temperature Atomic Layer Deposition of Al2O3: Impact on Efficiency, Stability and Surface Properties in Perovskite Solar Cells

Abstract In this work, solar cells with a freshly made CH 3 NH 3 PbI 3 perovskite film showed a power conversion efficiency (PCE) of 15.4 % whereas the one with 50 days aged perovskite film only 6.1 %. However, when the aged perovskite was covered with a layer of Al 2 O 3 deposited by atomic layer deposition (ALD) at room temperature (RT), the PCE value was clearly enhanced. X‐ray photoelectron spectroscopy study showed that the ALD precursors are chemically active only at the perovskite surface and passivate it. Moreover, the RT‐ALD‐Al 2 O 3 ‐covered perovskite films showed enhanced ambient air stability.