Understanding the relationship of photoexcited carrier lifetimes, mobilities, and recombination to structure and processing of photovoltaic absorber materials is critical to designing efficient solar cells. Using three complementary techniques, the authors elucidate photoexcited carrier dynamics in a high-quality kesterite crystal. These dynamics help to explain limitations in charge-carrier collection observed in a device's $J\ensuremath{-}V$ relation and external quantum efficiency. Combining ultrafast spectroscopy and device measurements in this way can lead to a more detailed understanding of the performance-limiting photophysical processes, accelerating the improvement of solar cells.