Uncover far-field electronic energy transfer in quantum dot superlattices by simultaneous tracking of exciton energy and diffusivity
Quantum dot (QD) solids are promising materials for future light harvesting devices and general energy transport applications. Further progress towards a QD-based electronics technology is dependent on the understanding of energy transport mechanism in the QD solids. The commonly invoked near-field Förster resonance energy transfer (FRET) theory often underestimates the exciton hopping rate in QD solids. There’s not a consensus yet on the exact cause. Towards better understanding the underlying energy transport mechanisms, we use an ultrafast transformation of STED microscopy (time-resolved ultrafast STED, or TRUSTED) to spatiotemporally resolve exciton diffusion in tellurium doped CdSe/CdS QD superlattices. We measured the concomitant time-resolved decay of mean exciton energy due to excitons sampling a heterogeneous energetic landscape. Together with Monte Carlo simulation, we demonstrated that, complementary to FRET, a far-field energy transfer mechanism is likely a significant energy transport pathway.
Rongfeng Yuan is a postdoctoral researcher in the group of Professor Naomi S. Ginsberg at UC Berkeley. Rongfeng's research has focused on uncovering the electronic energy transport mechanisms in semiconducting materials by ultrafast optical microscopies. He received his Ph.D. in Chemistry from Stanford University, where he studied aqueous hydrogen bond network dynamics with ultrafast 2D infrared spectroscopy in Professor Michael D. Fayer’s group.