Robust Interlayer Exciton Interplay in a Twisted van der Waals Heterotrilayer on a Broadband Bragg Reflector up to Room Temperature

We report robust room temperature (RT) interlayer excitons in transition metal dichalcogenide (TMD) heterostructures engineered via precise stacking orientation and twist‐angle control. We integrate a 2H‐stacked // heterotrilayer (HTL) onto a chirped distributed Bragg reflector (cDBR) that acts as a backside mirror. This way, we fabricate a platform that hosts distinct HTL, heterobilayer (HBL), and homobilayer (HoBL) regions with enhanced excitonic features at elevated temperatures. Although the HBL supports temperature‐tunable singlet and triplet interlayer excitons, it exhibits low emission yield at 4 K. In comparison, the HTL shows remarkable excitonic properties, including pronounced band modulation, intervalley interlayer exciton transitions, and a 10‐fold photoluminescence (PL) enhancement along with a sevenfold increase in exciton decay time at cryogenic temperatures compared to the HBL system. Temperature‐dependent studies reveal intriguing interlayer exciton dynamics in the HTL, including the emergence of valley‐polarized interlayer excitons, and the ability to maintain optical stability up to RT. Our results establish a clear strategy for engineering excitonic states across multilayer van der Waals heterostructures (VdWHSs) from 4 K to RT, providing a versatile platform for excitonic optoelectronics, quantum photonics, and tunable long‐lived interlayer exciton states in scalable TMD heterostructures.