# Strong Single- and Two-Photon Luminescence Enhancement by Nonradiative Energy Transfer across Layered Heterostructure

## TL;DR

This paper demonstrates significant enhancement of single- and two-photon luminescence in monolayer TMDs by leveraging non-radiative energy transfer from an underlying SnSe2 layer, improving their photonic application potential.

## Contribution

It introduces a layered heterostructure design that uses FRET to boost luminescence in TMD monolayers, a novel approach for enhancing 2D material optoelectronic properties.

## Key findings

- Luminescence enhancement factors of 14 (single-photon) and 7.5 (two-photon) achieved.
- FRET mechanism enables uniform enhancement across the entire heterostructure.
- Design exploits near-resonance and van der Waals coupling for efficient energy transfer.

## Abstract

The strong light-matter interaction in monolayer transition metal dichalcogenides (TMDs) is promising for nanoscale optoelectronics with their direct band gap nature and the ultra-fast radiative decay of the strongly bound excitons these materials host. However, the impeded amount of light absorption imposed by the ultra-thin nature of the monolayers impairs their viability in photonic applications. Using a layered heterostructure of a monolayer TMD stacked on top of strongly absorbing, non-luminescent, multi-layer SnSe2, we show that both single-photon and two-photon luminescence from the TMD monolayer can be enhanced by a factor of 14 and 7.5, respectively. This is enabled through inter-layer dipole-dipole coupling induced non-radiative Forster resonance energy transfer (FRET) from SnSe2 underneath which acts as a scavenger of the light unabsorbed by the monolayer TMD. The design strategy exploits the near-resonance between the direct energy gap of SnSe2 and the excitonic gap of monolayer TMD, the smallest possible separation between donor and acceptor facilitated by van der Waals heterojunction, and the in-plane orientation of dipoles in these layered materials. The FRET driven uniform single- and twophoton luminescence enhancement over the entire junction area is advantageous over the local enhancement in quantum dot or plasmonic structure integrated 2D layers, and is promising for improving quantum efficiency in imaging, optoelectronic, and photonic applications.

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Source: https://tomesphere.com/paper/1905.09875