Abstract
Excitonics, an alternative to romising for processing information since semiconductor electronics is rapidly approaching the end of Moore’s law. Currently, the development of excitonic devices, where exciton flow is controlled, is mainly focused on electric-field modulation or exciton polaritons in high-Q cavities. Here, we show an all-optical strategy to manipulate the exciton flow in a binary colloidal quantum well complex through mediation of the Förster resonance energy transfer (FRET) by stimulated emission. In the spontaneous emission regime, FRET naturally occurs between a donor and an acceptor. In contrast, upon stronger excitation, the ultrafast consumption of excitons by stimulated emission effectively engineers the excitonic flow from the donors to the acceptors. Specifically, the acceptors’ stimulated emission significantly accelerates the exciton flow, while the donors’ stimulated emission almost stops this process. On this basis, a FRET-coupled rate equation model is derived to understand the controllable exciton flow using the density of the excited donors and the unexcited acceptors. The results will provide an effective all-optical route for realizing excitonic devices under room temperature operation.
Highlights
Exciton-based solid-state devices have the potential to be essential building blocks[1,2] for modern information technology to surpass the performance of conventional electronic devices since excitonics combines an ultrafast operation speed[3] with a highly compact footprint[4]
We propose a strategy to control the exciton flow based on mediation of the Förster resonance energy transfer (FRET) process by stimulated emission in a binary nanomaterial complex consisting of 4 monolayer (ML) core-only CdSe Colloidal quantum wells (CQWs) and 8 ML core-shell CdS/CdSe/CdS CQWs
The spatial overlap is satisfied in the CQW complex due to the extended plate geometry and large absorption crosssection (>10−14 cm2), as detailed previously[10,22]
Summary
Exciton-based solid-state devices have the potential to be essential building blocks[1,2] for modern information technology to surpass the performance of conventional electronic devices since excitonics combines an ultrafast operation speed[3] with a highly compact footprint[4]. Because of the direct interaction with photons, excitonic devices effectively eliminate the interconnection delay between photon-based information communication and electronbased information processing. Unlike photonic devices with a diffraction limit of the footprint, the exciton thermal de Broglie wavelength is extremely small (~10 nm) at room temperature. Exploiting excitonic devices requires the factor microcavities, engineered electron/hole wavefunction overlap, or nanometer-scale precision DNA scaffolds. Förster resonance energy transfer (FRET) is a promising mechanism for excitonics, as dipolar coupling between a donor and an acceptor permits efficient and directed exciton flow in a simple solid mixture[10,11,12,13]. On the other hand, stimulated emission, in which the exciton recombination dynamics dramatically differs from that in spontaneous emission, is a possible
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