Title: Conical Intersections in Semiconductor Nanocrystals—How is Electronic Energy Converted to Heat?
Host: Cyrus Dreyer
Non-radiative recombination limits the efficiencies of semiconductor-based optoelectronic devices and photocatalysts by converting useful electronic energy into heat. It has been known for more than half a century that such recombination is facilitated by defects, but theoretical prediction of exactly which defects promote non-radiative recombination remains a challenge. In order to develop a predictive understanding of the role specific defects play in semiconductor photophysics, we are investigating the hypothesis that conical intersections between potential energy surfaces introduced by defects form pathways for recombination. We will present recent developments in the computational identification of such defect-induced conical intersections. Fast and stable graphics processing unit accelerated multireference electronic structure codes enable the identification of these defects, and new nonadiabatic molecular dynamics methods allow us to model dynamics in their vicinities. These tools have enabled us to identify defect-induced conical intersections in silicon nanomaterials, lead-halide perovskites, and chalcogenide nanomaterials. Through analysis of these intersections, we can understand how the structures of these materials determine their photophysical properties.