The relationship between the exciton binding energies of several pure organic dyes and their chemical structures is explored using density functional theory calculations in order to optimize the molecular design in terms of the light-to-electric energy-conversion efficiency in dye-sensitized solar cell devices. Comparing calculations with measurements reveals that the exciton binding energy and quantum yield are inversely correlated, implying that dyes with lower exciton binding energy produce electric current from the absorbed photons more efficiently. When a strong electron-accepting moiety is inserted in the middle of the dye framework, the light-to-electric energy-conversion behavior significantly deteriorates. As verified by electronic-structure calculations, this is likely due to electron localization near the electron-deficient group. The combined computational and experimental design approach provides insight into the functioning of organic photosensitizing dyes for solar-cell applications. This is exemplified by the development of a novel, all-organic dye (EB-01) exhibiting a power conversion efficiency of over 9%.