Zinc Aluminum Oxide Encapsulation Layers for Perovskite Solar Cells Deposited Using Spatial Atomic Layer Deposition

Abstract An atmospheric‐pressure spatial atomic layer deposition system is used to rapidly deposit 60 nm zinc–aluminum oxide (Zn–AlO x ) thin‐film‐encapsulation layers directly on perovskite solar cells at 130 °C without damaging the temperature‐sensitive perovskite and organic materials. Varying the Zn/Al ratio has a significant impact on the structural properties of the films and their moisture barrier performance. The Zn–AlO x films have higher refractive indexes, lower concentrations of OH─ groups, and lower water–vapor transmission rates (WVTR) than AlO x films without zinc. However, as the Zn/Al ratio increases beyond 0.21, excess Zn atoms segregate, leading to an increase in the number of available hydroxyl groups on the surface of the deposited film and a slight increase in the WVTR. The stability of the p–i–n formamidinium methylammonium lead iodide solar cells under standard ISOS‐D‐3 testing conditions (65 °C and 85% relative humidity) is significantly enhanced by the thin encapsulation layers. The layers with a Zn/Al ratio of 0.21 result in a seven‐fold increase the time required for the cells to degrade to 80% of their original efficiency.