Interlayer Excitons and Radiative Lifetimes in MoSe₂/SeWS Bilayers: Implications for Light-Emitting Diodes

High Resolution Image Download MS PowerPoint Slide Interlayer excitons, formed by electrical charge transfer between layers of 2D van der Waals heterostructures, are of the utmost importance for light-detection and light-harvesting applications. In particular, Janus-based heterostructures are promising platforms to observe robust interlayer exciton dynamics due to their intrinsic electric field. Here, we carry out ground- and excited-state first-principles calculations, based on the G 0 W 0 approach and the solution of the Bethe–Salpeter equation, to investigate the energetic, electronic, and excitonic properties of MoSe 2 /WSSe van der Waals heterobilayers. Our results show that the heterojunction presents features of type-II band alignment and tightly bound, long-lived interlayer excitons. Indeed, the lowest dipole-allowed excitonic state possesses an interlayer character and a slight deviation of 12% in its binding energy compared to the lowest-energy intralayer exciton. Furthermore, the interlayer excitons have transition rates ∼55 times smaller than the intralayer ones, which translates into a longer radiative lifetime of dozens of nanoseconds at room temperature. This is up to 2 orders of magnitude greater than that of the lowest-energy intralayer exciton. The findings emphasize the critical role of Janus-based heterojunctions in influencing interlayer exciton radiative lifetimes, indicating that the system possesses considerable potential for application in optoelectronic devices such as a light-emitting diode (LED) or photodetector.