Professor Kelley's research group uses ultrafast optical spectroscopy to examine the optical and electronic properties of semiconductor nanoparticles. He focuses on layered semiconductors — specifically gallium selenide and indium selenide — which have layered crystal structures and form two-dimensional, disk-like nanoparticles. The optical properties of indium selenide are very well suited for the absorption of sunlight; therefore, its nanoparticles hold considerable promise as the active media in photovoltaics.
Professor Kelley's group synthesizes nanoparticles that have diameters from 2 nm to tens of nanometers — all of which are four atoms thick — as the properties of such nanoparticles are strongly size dependent, due to quantum size effects. He is primarily interested controlling and optimizing the properties of the nanoparticles for solar energy conversion.