Electronic coupling and ground-state charge transfer at the C-60/ZnO hybrid interface is shown to localize carriers in the C-60 phase. This effect, revealed by resonant X-ray photoemission, arises from interfacial hybridization between C-60 and ZnO. Such localization at carrier-selective electrodes and interlayers may lead to severely reduced carrier harvesting efficiencies and increased recombination rates in organic electronic devices.