Nanowire-Based Quantum Dot Sensitized Solar Cells

Keywords:
quantum dots, CdSe, ZnO, Nanowires, solar cells, photovoltaics

Abstract:
While solar energy could provide enough power to satisfy the current worldwide demand, the fabrication of photovoltaic systems that are efficient and competitive with fossil fuels remains a serious challenge. To solve this problem, new strategies for solar-to-electric energy conversion are under development. We combined CdSe semiconductor nanocrystals (or quantum dots) and single-crystal ZnO nanowires to demonstrate a new type of quantum dot-sensitized solar cell. An array of ZnO nanowires were grown vertically on a transparent conducting glass substrate in aqueous solutions of methenamine and zinc nitrate at ~95 oC. Nanometer size CdSe quantum dots, capped with mercaptopropionic acid, were attached to the surface of the nanowires. When illuminated with visible light, the excited CdSe quantum dots injected electrons across the quantum dot-nanowire interface. The morphology of the nanowires then provided the photoinjected electrons with a direct electrical pathway to the photoanode. Using a liquid electrolyte as the hole transport medium, quantum dot-sensitized nanowire solar cells were obtained that exhibited short-circuit currents ranging from 1-2 mA/cm2 and open-circuit voltages of ~0.5 V.

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Nanotech 2007 Conference Program Abstract