Thermally Robust Room‐Temperature Interlayer Excitons in a Hybrid van der Waals Heterostructure

Having long lifetimes and intrinsic electric dipole moments, interlayer excitons in van der Waals heterostructures are promising quasiparticles for excitonic optoelectronics. However, their practical implementation has been largely hindered by the fact that most interlayer excitons suffer from strongly suppressed radiative recombination and are stable only under cryogenic conditions. Here, we identify a distinct class of interlayer excitons that are simultaneously optically active and robust at room temperature in an atypical van der Waals heterostructure formed by a two‐dimensional layered perovskite (PEA) 2 PbBr 4 and monolayer MoS 2 . These interlayer excitons appear as a distinct photoluminescence feature and exhibit a polarization‐anisotropic response in a tilted sample geometry, consistent with an out‐of‐plane component of the optical transition dipole moment. Remarkably, the interlayer exciton emission persists up to 400 K, indicating exceptional thermal robustness. Time‐resolved measurements reveal a moderate lifetime enhancement compared to intralayer excitons, indicating a hybrid state that balances partial spatial charge separation with retained electron‐hole wavefunction overlap. First‐principles calculations support a type‐II electronic structure with spatially displaced band‐edge states, finite interfacial coupling, and charge redistribution across the interface. Our findings establish (PEA) 2 PbBr 4 /MoS 2 as a promising platform for optically active interlayer excitons under ambient and elevated‐temperature conditions.