Evidence for Fast Interlayer Energy Transfer in MoSe2/WS2 Heterostructures

TL;DR

This study demonstrates ultrafast (around 1 ps) interlayer energy transfer in MoSe2/WS2 heterostructures, revealing a F"orster-type mechanism that surpasses previously observed charge transfer processes, with implications for optoelectronic applications.

Contribution

The paper provides the first experimental evidence of fast F"orster-type energy transfer in MoSe2/WS2 heterostructures, highlighting a new mechanism for interlayer exciton dynamics in 2D materials.

Findings

Interlayer energy transfer occurs on a timescale of about 1 ps.

The transfer mechanism is F"orster-type involving resonant exciton excitation.

Efficient energy transfer suggests potential for optical and energy harvesting applications.

Abstract

Strongly bound excitons confined in two-dimensional (2D) semiconductors are dipoles with a perfect in-plane orientation. In a vertical stack of semiconducting 2D crystals, such in-plane excitonic dipoles are expected to efficiently couple across van der Waals gap due to strong interlayer Coulomb interaction and exchange their energy. However, previous studies on heterobilayers of group 6 transition metal dichalcogenides (TMDs) found that the exciton decay dynamics is dominated by interlayer charge transfer (CT) processes. Here, we report an experimental observation of fast interlayer energy transfer (ET) in MoSe2/WS2 heterostructures using photoluminescence excitation (PLE) spectroscopy. The temperature dependence of the transfer rates suggests that the ET is F\"orster-type involving excitons in the WS2 layer resonantly exciting higher-order excitons in the MoSe2 layer. The estimated ET time of the order of 1 ps is among the fastest compared to those reported for other nanostructure hybrid systems such as carbon nanotube bundles. Efficient ET in these systems offers prospects for optical amplification and energy harvesting through intelligent layer engineering.