Functionalized semiconductor nanocrystal quantum dots for patterned, multilayered photovoltaic devices

We report an approach for nanostructured photovoltaic devices using functionalized semiconductor nanocrystal quantum dots (NQDs) by incorporation of the functional ligand t-butoxycarbonyl (t-BOC) which has an acid-labile moiety. This change in the surface chemistry results in the ability to photo-pattern the NQDs, where desired, for a number of optoelectronic device geometries with sub-micron patterning capability. This also enables the fabrication of multi-layered nanostructure photovoltaic devices. We demonstrate an improved photoconducting device, using the patterning and ligand modification process, as well as a bi-layered solar cell using CdTe and CdSe NQDs. The photoconductor has the metal semiconductor metal structure and it shows at least 3 times higher conductivity and photo-response at an electric field of 300kV/cm when using the t-BOC modified QDs. Moreover, the functionalized NQDs enable all solution processed multilayered and patterned structures without high temperature sintering or additional chemical treatment. By using this method, a bi-layered solar cell was fabricated. The preliminary result shows 0.05% solar conversion efficiency and an open circuit voltage of 0.72V under AM1.5G 1 sun illumination.