Mapping Concurrent Charge Carrier Dynamics at Semiconductor Surfaces Using Frequency-Domain Surface Photovoltage...

Quantitative understanding of concurrent charge carrier dynamics at semiconductor surfaces remains challenging due to limited spatial and temporal resolution. Here, we introduce frequency-domain inversion for surface photovoltage microscopy (FI-SPVM), combining Kelvin probe force microscopy with periodic illumination and lock-in detection to capture complex surface photovoltage spectra across a broad frequency range. By modeling the system as linear time-invariant and applying a convex-inversion framework with sparsity and total variation regularization, FI-SPVM resolves signed distributions of relaxation times spanning nanoseconds to seconds. This approach disentangles overlapping carrier pathways, reveals their characteristic lifetimes and polarities, and generates spatially resolved maps linking nanoscale structures to dynamics. Validation on synthetic and experimental data from various semiconductor films confirms accurate recovery and robustness under practical constraints. This approach provides a general framework for mapping concurrent charge carrier dynamics and offers broad applicability to complex semiconductor systems, including photocatalysis, perovskite photovoltaics, and optoelectronic devices, where nonequilibrium carrier processes critically determine performance.