Iodine migration in lead halide perovskite solar cells investigated by X-ray photoelectron spectroscopy

Abstract We investigate iodine migration in lead halide perovskite solar cells using X-ray photoelectron spectroscopy. We observe iodine migration to the surface direction at both the solar cell’s electrode and non-electrode regions. Our findings suggest that diffusion can drive iodine migration even without an electric field. We also detected iodine accumulation near the Ag electrode, probably related to increased series resistance and reduced efficiency. Present results highlight the need for a dense interfacial layer to suppress iodine migration.