Twist Angle Effects on the Absorbance, Carrier Lifetime, and Diffusion Properties in Low Dimension Type-II MoS2/WS2 Heterobilayers

Abstract

Atomically thin two-dimensional (2D) transition metal dichalcogenides (TMDs) are promising materials for photovoltaic (PV) applications. Their self-terminated nature and strong absorption characteristics introduce an unprecedented possibility for high voltages to bandgap ratios, with secondary benefits including the potential for high internal quantum efficiencies/low recombination and strong absorption coefficients coupled with stability in a range of environments. However, despite the promise of such material systems, their PV performances still lag behind the conventional 3D materials. In principle, one possible way to manipulate the behavior of a 2D heterobilayer structure is to change its interlayer twist angle. In this study, the effects of twist angle between vertically stacked type-II MoS2/WS2 heterobilayers on fundamental optical properties such as light absorbance, excess carrier lifetime, and diffusion are reported. These properties can have a direct effect on the final PV performance of these heterobilayers. It is found that the interlayer twist in MoS2/WS2 heterobilayers does not affect their absorbance. However, the carrier lifetime and photon emission across the heterobilayers are modulated with the interlayer twist. These findings could be useful to facilitate the optimization of monolayer TMD-based optoelectronic devices.