Photovoltage Behavior in Perovskite Solar Cells under Light-Soaking Showing Photoinduced Interfacial Changes

The photovoltage of perovskite solar cells (PSCs) was studied over a wide range of light intensities, showing changes from pristine to light-soaking (LS) conditions, explained using a specific model of spatial charge distribution. Migration of ions and vacancies under photovoltage conditions results in localized charge redistribution manifested as positive charge accumulation at the TiO₂ or TiO₂–MgO interlayer–perovskite interface, signifying photoinduced interfacial upward band bending. Consequentially, generation of an electrostatic potential (V_elec) and an increase in interfacial recombination rate are confirmed. The magnitude and effect of V_elec and interfacial recombination on the photovoltage depend on the illumination intensity and on the LS duration. PSCs with mesoporous Al₂O₃ showed similar changes, validating the role of the compact TiO₂. Faster generation and a gradual increase of V_elec are apparent under LS, which expresses the constant migration of ions and vacancies toward the interface. The nonrigid TiO₂–perovskite interface calls for a vital perspective change of PSCs.