Effect of different oxygen precursors on alumina deposited using a spatial atomic layer deposition system for thin-film encapsulation of perovskite solar cells

An atmospheric-pressure spatial atomic layer deposition system operated in atmospheric-pressure spatial chemical vapor deposition conditions is employed to deposit alumina (AlOx) thin films using trimethylaluminum and different oxidants, including water (H2O), hydrogen peroxide (H2O2), and ozone (O-3). The impact of the oxygen precursor on the structural properties of the films and their moisture-barrier performance is investigated. The O-3-AlOx films, followed by H2O2-AlOx, exhibit higher refractive indexes, lower concentrations of OH- groups, and lower water-vapor-transmission rates compared to the films deposited using water (H2O-AlOx). The AlOx films are then rapidly deposited as thin-film-encapsulation layers on perovskite solar cells at 130 degrees C without damaging the temperature-sensitive perovskite and organic materials. The stability of the p-i-n formamidinium methylammonium lead iodide solar cells under standard ISOS-D-3 testing conditions (65 degrees C and 85% relative humidity) is significantly enhanced by the encapsulation layers. Specifically, the O-3-AlOx and H2O2-AlOx layers result in a six-fold increase in the time required for the cells to degrade to 80% of their original efficiency compared to un-encapsulated cells.