Metal oxide semiconductors are an appealing class of material, extensively used as photoanodes in excitonic solar cells such as dye- and quantum dot-sensitized solar cells. On page 1744, I. Concina and A. Vomiero describe how proper tailoring of the shape, composition, and crystalline structure of these materials can significantly boost the performances of these solar energy converting devices by ameliorating the processes of exciton separation, charge transport, and collection, while reducing charge losses due to recombination and back reactions.