High Open Circuit Voltage Quantum Dot Sensitized Solar Cells Manufactured with ZnO Nanowire Arrays and Si/ZnO Branched Hierarchical Structures

Inorganic semiconductors are currently receiving increasinginterest as light sensitizers for low-cost photovoltaic devices.14 In the standard sensitized solar cell configuration,5 a dye mono-layer is used as a light-harvestingmaterial fromwhich electrons are injected into a nanostructured wide bang gap semiconductor (i.e., TiO2, ZnO, SnO2). The oxidized dye is regenerated by the donor species of a redox couple solved in an electrolyte, allowing an excellent wetting of the whole effective area of the nanostructured electrode. Finally, the electrolyte is regenerated in turn at the counter electrode by the complementary redox reaction. In this configuration, the nanostructured nature of the active electrode plays a key role in obtaining high efficiency devices because the increase in the effective surface allows higher dye loading amount and consequently an increase in the light harvesting. Efficiencies>11 % have been obtained for dye-sensitized solar cells (DSCs).6,7 Semiconductor quantum dots (QDs) as a light absorbing material in QD-sensitized solar cells (QDSCs) also awake great interest b