Synergistic effects of charge transfer, energy transfer and cavity interference on the exciton emission in WS/hBN/WS heterostructures.

Charge transfer (CT) and energy transfer (ET) are prevalent in various van der Waals (vdW) structures. They act on both the donor and acceptor at the nanometer scale to control the carrier behavior and modulate the device performance, which is an important research direction in the field of photonics and optoelectronics. Here, we report that the carrier behavior in a WS/hBN/WS heterostructure is equally modulated by the cavity interference effect in addition to the common CT and ET effects, which results from the cavity-like structure formed by the multilayer material stack. Time-resolved photoluminescence measurements demonstrate that the exciton decay rate undergoes a three-stage change, namely acceleration-deceleration-acceleration, when the hBN thickness changes from 3.0 to 26.1 nanometers. By modeling the carrier dynamics, including cavity interference, CT and ET processes, we perfectly reproduce the decay trend. Understanding the regulation of carrier dynamics by the electrodynamic environment in vdW structures lays the scientific foundation for the development of relevant photoluminescent devices through smart layer engineering.