Colloquium: Zhigang Wu

ABSTRACT:  Dynamics of electronically excited states including exciton generation and relaxation, exciton-exciton interaction, and charge/energy transfer and transport, are critical to understanding and optimizing nanoscale materials assemblies for optoelectronic applications, especially photovoltaic cells. Although considerable progress has been made, accurate experimental characterization of such crucial dynamics in nanostructures remains extremely challenging. In this talk, I will discuss the latest advance in quantum mechanical simulations of electronic excitations. I will present our recent works on electronic structures of various extended nanostructures including one-dimensional (1-D) silicon nanowires and 2-D periodically patterned graphene, and the charge transfer dynamics for a variety of organic-organic, organic-inorganic, and inorganic-inorganic interfaces between 0-D materials. I will also talk about the great challenges current first-principles electronic-structure calculations are facing, and our computational method development. Finally, I will propose a full-spectrum-light-absorption scheme for making highly efficient photovoltaic cells, taking advantage of complexity and flexibility of nanscale material assemblies consisting of different characteristics and dimensions.