Surfaces facilitate chemical reactions occurring in biological and synthetic systems with wide-ranging applications from energy conversion to catalysis and sensing. Microscopic understanding of the structure and dynamics that underpin these reactions is keenly pursued with novel experimental techniques such as sum frequency generation and laser-assisted photoemission spectroscopy. Herein, we demonstrate a method for interpreting the time-resolved observation of the Stark effect to provide an in situ optical probe of the charge dynamics during an interfacial reaction. The analysis holds broad potential for investigating charge migration in surface-bound catalysts and sensors, as well as photocenter and retinal proteins, even when the Stark parameters of the material are unknown. We demonstrate the analysis with respect to the energy conversion reaction in solid-state dye-sensitized solar cells.