3. Nanomaterials for solar energy conversion.

Nanotechnology offers new approaches to solar energy conversion that promise higher efficiencies and lower costs. The complex hierarchical nanowire structures we have demonstrated are promising candidates for effectively harvesting solar energy because the scattering improves light absorption and the dendritic structure optimizes carrier collection, yet their actual applications can be challenging due to the dramatic departure from the conventional paradigm of planar p-n junction solar cells. We are exploring various approaches to utilize such branching nanostructures for solar energy conversion. We are also interesting in exploiting such structures for photoelectrocatalysis because solar fuel production does not require electrical contact and but benefits from high surface area therefore can better takes advantages of chemically synthesized nanostructures.

More fundamentally, in collaboration with Prof. John Wright and Robert Hamers, we are interested in investigating coherent charge transport across quantum confined nanoscale heterostructures mimicking the coherent processes in photosynthesis and dye-sensitizer solar cells. Our collaboration hopes to provide the fundamental understandings required to make coherent transport a ubiquitous feature of solar energy conversion nanostructures with arbitrarily complex shapes, compositions, and dimensionalities.

In all of these studies, we will specifically utilize our understanding of the screw-dislocation driven NW growth to develop the NW synthesis of more abundant and stable semiconductor materials that can be carried out on a large scale in an economical manner, possibly in aqueous solutions. These materials were previously considered to be “poor” semiconductors whose carrier density, mobility, and exciton diffusion length are unsuitable for solar energy applications, but are now potentially quite interesting because the new device design concepts based on NW structures may circumvent the problems.