Mercurochrome showed efficient performance as an organic dye photosensitizer for a solar cell based on nanoporous ZnO thin film electrodes. A 2.5% solar energy conversion efficiency was accomplished under AM 1.5 (99 mW cm(-2)) with a short-circuit photocurrent density (Jsc) of 7.44 mA cm(-2), an open-circuit photovoltage (Voc) of 0.52 V, and a fill factor of 0.64. A monochromatic incident photon-to-current efficiency (IPCE) reached 69% at 510 nm.