ALD-grown SnO$_2$ as an electron selective layer for perovskite/silicon tandem cells

International audienceThis work presents a comparative study between tin(IV) oxide (SnO2) thin films deposited either by solution process or by Atomic Layer Deposition (ALD) for an application as an electron selective layer in perovskite/silicon tandem solar cells. This study is motivated by the usually lower performances of electron selective layers made of ALD-grown SnO2 compared to ones made via solution processes. Chemical, electrical, optical and topographical properties of each type of film were investigated. In an attempt to link thin film properties to device characteristics single-junction perovskite solar cells and perovskite/silicon tandem solar cells were fabricated. Despite the high-quality electronic and optical properties of ALD-grown SnO2, perovskite-based solar cells employing such film showed limited performances. Characterization of perovskite films properties grown on both type of SnO2 did not rise significant differences and tend to indicate some hindering factors at the ALD-grown SnO2 interface with perovskite. Specifically, Kelvin force probe microscopy characterisation unveiled a larger workfunction for ALD-grown SnO2, which may create a potential barrier for electron extraction from the perovskite