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 (AP-SALD) system operated in atmospheric-pressure spatial chemical vapor deposition (AP-SCVD) conditions is employed to deposit alumina (AlOx) thin films using trimethylaluminum and different oxidants, including water (H2O), hydrogen peroxide (H2O2), and ozone (O3). The impact of the oxygen precursor on the structural properties of the films and their moisture-barrier performance is investigated. The O3-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 ºC 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 (65ºC and 85% relative humidity) is significantly enhanced by the encapsulation layers. Specifically, the O3-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.