Unraveling energy and charge transfer in type-II van der Waals heterostructures

Junyi Liu,Zi Li,Gang Lu,Xu Zhang

doi:10.1038/s41524-021-00663-w

Abstract

Recent experiments observed significant energy transfer in type-II van der Waals (vdW) heterostructures, such as WS2/MoSe2, which is surprising due to their staggered band alignment and weak spectral overlap. In this work, we carry out first-principles calculations to shed light on energy and charge transfer in WS2/MoSe2 heterostructure. Incorporating excitonic effect in nonadiabatic electronic dynamics, our first-principles calculations uncover a two-step process in competing energy and charge transfer, unravel their relative efficiencies and explore the means to control their competition. While both Dexter and Förster mechanisms can be responsible for energy transfer, they are shown to operate at different conditions. The excitonic effect is revealed to drive ultrafast energy and charge transfer in type-II WS2/MoSe2 heterostructure. Our work provides a comprehensive picture of exciton dynamics in vdW heterostructures and paves the way for rational design of novel vdW heterostructures for optoelectronic and photovoltaic applications.

Highlights

Van der Waals heterostructures composed of vertically stacked two-dimensional (2D) layers are attracting enormous attention[1,2,3], as they provide a fascinating playground to explore both fundamental physics[4,5,6] and novel applications[7,8]
Materials, transition metal dichalcogenides (TMDs) are of particular interest owing to their strong light–matter interactions[9,10] and strong spin–orbit coupling (SOC)[11,12]
The accessibility to valley degrees of freedom coupled with rich exciton physics render TMD heterostructures an ideal platform for exploiting charge and exciton dynamics at nanoscales

Summary

Introduction

Van der Waals (vdW) heterostructures composed of vertically stacked two-dimensional (2D) layers are attracting enormous attention[1,2,3], as they provide a fascinating playground to explore both fundamental physics[4,5,6] and novel applications[7,8]. The accessibility to valley degrees of freedom coupled with rich exciton physics render TMD heterostructures an ideal platform for exploiting charge and exciton dynamics at nanoscales. In vdW heterostructures, both charge and energy transfer can take place and compete with each other[3,23]. As charge and energy transfer compete with each other, one of them has to be promoted while the other suppressed for a given application

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