Achieving High Open-Circuit Voltage on Planar Perovskite Solar Cells via Chlorine-Doped Tin Oxide Electron Transport Layers

The open-circuit voltage deficit is one of the main limiting factors for the further performance improvement in planar structured perovskite solar cells. In this work, we elaborately develop chlorine binding on the surface of tin oxide electron transport layer for a high open-circuit voltage device (1.195 V). The chlorine passivation on SnO₂ not only effectively mitigates the interfacial charge recombination between SnO₂ and perovskite but also enhances the binding of chlorine with lead at the SnO₂/perovskite interface. The chlorine-passivated SnO₂ electron transport layer exhibits a better energy alignment with the perovskite layer and an improved electron mobility, which will promote efficient electron transfer at the interface. In addition, the elevated Fermi level of SnO₂ electron transport layer increases carrier extraction and suppresses interfacial recombination, which is responsible for the open-circuit voltage enhancement. Planar perovskite solar cells with chlorine-passivated SnO₂ exhibit a higher open-circuit voltage of 1.195 V than that of reference ones (1.135 V) for a lower band gap of 1.58 eV perovskite absorbers, which achieve a power conversion efficiency of 20% with negligible hysteresis.