Rational tuning of SnO2 electron transport layer grown by atomic layer deposition for performance improvement of perovskite solar cells

The electron transport layer (ETL) of a perovskite solar cell (PSC) plays a pivotal role in determining cell performance. In this work, an atomic layer deposition (ALD) technique was employed to grow high-quality SnO2 thin films, and those ALD-grown SnO2 films were used as ETLs of PSCs. The properties of films and the performance of PSCs were closely examined depending on the SnO2 growth conditions. The SnO2 films grown at higher temperatures showed a very small surface roughness (≤0.6 nm) though grown faster. The relative oxygen content of the film was inclined to decrease with increasing the growth temperature. Consequently, the carrier concentration and the Fermi level of the film became higher at elevated temperatures. PSCs with ALD-grown SnO2 ETLs also revealed a clear correlation between cell performance and the film growth temperature. The results of this work may offer practical guidelines for enhancing the performace of a PSC that employs a metal oxide as an ETL.