Ultrahigh-Purity Single-Photon Emission from 2D WSe₂ via Effective Suppression of Classical Emission

Single-photon emitters (SPEs) in two-dimensional WSe₂ offer high extraction efficiency and on-chip compatibility, but achieving high purity remains challenging. We present two strategies to suppress classical emission and enhance purity in WSe₂-based SPEs. In monolayer WSe₂, we exploited the presence and absence of valley-spin locking in free and bound excitons, respectively, to achieve purity of 98.3% via polarization control and 99.0% combined with near-resonant excitation. In bilayer WSe₂, we obtained 97.0% purity without polarization filtering, enabled by the indirect band gap and inversion symmetry. These values represent some of the highest as-measured purities reported for 2D TMD SPEs. Our methods do not require complex fabrication or instrumentation and are supported by first-principles calculations of the vacancy state of Se and spin degeneracy. This work offers practical pathways for realizing high-quality single-photon sources for emerging quantum technologies.