Charge Transfer Excitons at van der Waals Interface
Frontiers of CMP Lecture: October 1, Thursday
Rice: 3:10 PM, SST 106, simulcast from Columbia
Speaker: Prof. Xiao Yang Zhu (Columbia, Chemistry)
Title: Charge Transfer Excitons at van der Waals Interface
The van der Waals interfaces of molecular donor/acceptor or graphene-like two-dimensional (2D) semiconductors are central to concepts and emerging technologies of light-electricity inter-conversion. Examples include, among others, solar cells, photo-detectors, and light emitting diodes. A salient feature in both types of van der Waals interfaces is the poorly screened Coulomb potential that can give rise to bound electron-hole pairs across the interface, i.e., charge transfer (CT) or inter-layer excitons. Here we address common features of CT excitons at both types of interfaces. We emphasize the competition between localization and delocalization in ensuring efficient charge separation. At the molecular donor/acceptor interface, electronic delocalization in real space can dictate charge carrier separation. In contrast, at the 2D semiconductor heterojunction, delocalization in momentum space due to strong exciton binding may assist in parallel momentum conservation in CT exciton formation.