By using time- and space-resolved laser spectroscopy, we evaluate nonradiative carrier recombination loss, such as bulk recombination, interface and surface recombination, and Auger recombination, in concentrator solar cells consisting of multi-junction heterostructures and nanostructures, and find ways to high efficiencies of light energy conversion. In addition, we study multiexciton generation rate, Auger recombination rate, and carrier extraction rate, which compete in nanostructure solar cells, in order to examine experimentally a long-standing issue whether one-photon to multi-electron conversion processes can be effectively utilized.

In this project, we aim to develop a new optical management technology for solar cells based on photonic nanostructures (or photonic crystals). We will investigate broad-area resonant effects at band-edges of photonic crystals in order to enhance the absorption at the wavelength regime (600-1,000nm) where the magnitude of the absorption in thin film silicon (such as a-Si or micro-crystalline Si) reduces significantly.

Production of solar-grade silicon conventionally requires extremely high reaction temperature with long duration, which causes considerable drawbacks. In this research, we focused upon electrochemical approaches which take place at solid/liquid interfaces to directly reduce silica to silicon, and by detailed analysis and understanding from atomistic viewpoint, we optimize the reactions to develop comprehensive process for producing high-purity silicon material for solar cell applications. We also attempt to utilize diatomaceous earth as reliable source for producing high-purity silica for such an application.