Study of ALD-grown Tin Oxide as an Electron Selective Layer for NIP Perovskite-Based Solar Cells

This work presents a comparative study between tin(IV) oxide $(\mathbf{SnO_{2}})$ 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 solar cells using electron selective layer (ESL) made of ALD-grown $\mathbf{SnO_{2}}$ compared to ones using a solution-processed ESL. 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 conductivity and optical properties of ALD-grown $\mathbf{SnO_{2}}$ , perovskite-based solar cells employing such film showed limited performances. Characterization of perovskite films properties grown on both type of $\mathbf{SnO_{2}}$ did not rise significant differences and tend to indicate some hindering factors at the ALD-grown $\mathbf{SnO_{2}}$ interface with perovskite. Specifically, a larger workfunction for ALD-grown $\mathbf{SnO_{2}}$ may create a potential barrier for electron extraction at perovskite interface