Unraveling photo-induced charge transfer properties at 3D/2D perovskite interfaces via in-situ surface photovoltage spectroscopy

As a non-destructive and contactless characterization technique, the surface photovoltage (SPV) method based on a lock-in amplifier was applied to characterize charge transfer at the nanoscale of 3D/2D perovskite interface. The SPV response of the 3D/2D perovskite was found to be stronger than that of the 3D perovskite, suggesting improved separation and transfer of photo-induced electron-hole pairs by the 2D overlayer. The photovoltaic process can be presented as a vector diagram with the magnitude and the phase angles to unravel charge transfer direction. The magnitude of the overall photovoltaic vector increases with an anticlockwise rotation and confirms the hole transfer at 3D/2D perovskite interfaces. Moreover, light-chopping-frequency dependent measurements were performed to study photogenerated electron transfer kinetics at the 3D/2D interface. The frequency of peak SPV for 3D/2D MAPbI₃ perovskite was higher than that of 3D MAPbI₃ demonstrated a faster charge separation in 3D/2D interface. The results provide valuable information about the in-situ charge transfer properties of photogenerated charge carriers at the 3D/2D perovskite interfaces.