A composite electrodynamic mechanism to reconcile spatiotemporally resolved exciton transport in quantum dot superlattices

Rongfeng Yuan; Trevor D. Roberts; Rafaela M. Brinn; Alexander A. Choi; Ha H. Park; Chang Yan; Justin C. Ondry; Siamak Khorasani; David J. Masiello; Ke Xu; A. Paul Alivisatos; Naomi S. Ginsberg

doi:10.1126/sciadv.adh2410

arXiv · 2302.10453

A composite electrodynamic mechanism to reconcile spatiotemporally resolved exciton transport in quantum dot superlattices

Rongfeng Yuan·Trevor D. Roberts·Rafaela M. Brinn·Alexander A. Choi·Ha H. Park·Chang Yan·Justin C. Ondry·Siamak Khorasani·David J. Masiello·Ke Xu·A. Paul Alivisatos·Naomi S. Ginsberg

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Abstract

Quantum dot (QD) solids are promising optoelectronic materials; further advancing their device functionality depends on understanding their energy transport mechanisms. The commonly invoked near-field F\"orster resonance energy transfer (FRET) theory often underestimates the exciton hopping rate in QD solids, yet no consensus exists on the underlying cause. In response, we use time-resolved ultrafast stimulated emission depletion (TRUSTED) microscopy, an ultrafast transformation of stimulated emission depletion (STED) microscopy to spatiotemporally resolve exciton diffusion in tellurium-doped CdSe-core/CdS-shell QD superlattices. We measure the concomitant time-resolved exciton energy decay due to excitons sampling a heterogeneous energetic landscape within the superlattice. The heterogeneity is quantified by single-particle emission spectroscopy. This powerful multimodal set of observables provides sufficient constraints on a kinetic Monte Carlo simulation of exciton transport to elucidate a composite transport mechanism that includes both near-field FRET and previously-neglected far-field emission/reabsorption contributions. Uncovering this mechanism offers a much-needed unified framework in which to characterize transport in QD solids and additional principles for device design.

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Rongfeng Yuan, Trevor D. Roberts, Rafaela M. Brinn, Alexander A. Choi, Ha H. Park, Chang Yan, Justin C. Ondry, Siamak Khorasani, David J. Masiello, Ke Xu, A. Paul Alivisatos, Naomi S. Ginsberg. 2023-02-21. A composite electrodynamic mechanism to reconcile spatiotemporally resolved exciton transport in quantum dot superlattices. https://doi.org/10.1126/sciadv.adh2410

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