Due to its ability to transmit energy and information through space, light plays a central role in nearly all aspects of human society. Research in the Roberts group focuses on developing materials that can transduce light into readily usable forms of energy. Most of our research revolves around the fact that light delivers its energy in the form of photons, discrete particles whose energy must be ideally matched to their intended application. Our group works to develop materials that reshape light, by either combining the energy of multiple low-energy photons to generate high-energy photons or using individual high-energy photons to produce multiple lower energy ones. Such transformations can enable new light-driven technologies, such as high-efficiency solar cells, infrared light detectors, and photocatalysts. To optimize the function of these materials, we employ and develop ultrafast spectroscopy techniques that can track the behavior of photoexcited electrons with femtosecond time resolution and a spatial resolution of a few tens of nanometers.