The charge transfer associated with the presence of photosensitizing dyes (fluorescein, erythrosin B, and rose bengal) was investigated on single‐crystal ZnO surfaces employing surface photovoltage spectroscopy. It was found that the charge transfer takes place via electron transitions from the surfaces to the conduction band. The energy necessary for these transitions is transferred to the surface states from excited states of the photosensitizing dyes. The surface states were found to be related to chemisorbed oxygen and their density is (2–4) ×1010/cm2under atmospheric pressure at room temperature.