An org. chromophore D5 (3-(5-(4-(diphenylamino)styryl)thiophene-2-yl)-2-cyanoacrylic acid) was tested as a sensitizer in photoelectrochem. mesoporous ZnO solar cells. Using thin (∼3 μm) mesoporous ZnO electrodes, high incident photon-to-current conversion efficiencies of up to 70% were obtained, while power conversion efficiencies up to 2.4% were found in simulated sunlight (100 mW cm-2). Long dye adsorption times (16 h) could be used without aggregation or pptn. of the dye. The compn. of the iodide/triiodide-based electrolyte was found to be crucial in optimization of the ZnO-based dye-sensitized solar cell. A high concn. of Li+ ions was found to be shift the ZnO conduction band edge to more neg. potential, whereas opposite behavior is found for mesoporous TiO2 cells. It was also found to be detrimental for solar cell performance and stability. Electrolyte-dependent and photoinduced dye desorption from the ZnO electrode was identified as a major stability problem in D5-sensitized ZnO solar cells.