Understanding excited state phenomena is at the heart of many important materials problems, such as photovoltaics, photocatalysis, plasmonics and solid-state lighting, to name but a few. In the realm of modeling and simulations, time-dependent density functional theory (TDDFT) has become one of the most powerful, versatile and popular tools for probing electronic structure and excitations in molecular and solid-state materials. Unfortunately, TDDFT is computationally demanding and as a result, its application to realistic materials remains exceedingly difficult. In this talk, I will outline our recent progress in developing accurate and efficient TDDFT methods that would allow us to start addressing these challenges. Among them, a subspace TDDFT method is developed which can calculate both excitation energy and excited state forces accurately for systems containing up to a few thousand electrons. We have also proposed a time-dependent orbital-free DFT (TD-OFDFT) method with which tens of thousands of electrons can be treated accurately in metals. Combining these TDDFT methods with non-adiabatic molecular dynamics, one can perform coupled electron-ion and exciton-ion dynamics where phonons are important in electron transitions and excitations. I’ll show how these first-principles methods can be brought to bear on critical scientific problems that are of broad practical interests, including spontaneous electron-hole separation in perovskite solar cells upon photon adsorption, exciton diffusion and dynamics in disordered semiconductors for organic photovoltaics and plasmonic responses of metallic nanostructures.
The work was supported by the US Army, Navy and the National Science Foundation.
Prof. Lu received his Ph. D from Chinese Academy of Sciences while most of his Ph. D work was carried out in his current institution - California State University Northridge (CSUN). After a postdoc appointment at Harvard, Prof. Lu returned to CSUN as a faculty member in 2004 and was promoted to a full professor in 2009. He is the director of NSF-funded PREM center and the founding director of the Center of Excellence in Materials Innovation, both at CSUN. Prof. Lu spends significant research effort in developing first-principles based multiscale computational methods and has applied these methods to various important materials problems. Some of the problems relevant to energy applications will be highlighted in the talk. His recent publications (since 2010) can be found at http://www.csun.edu/nsfprem/recent-publications-dr-lu.