  Quantum-dot-like WSe$_2$ single-photon emitters have become a promising
platform for future on-chip scalable quantum light sources with unique
advantages over existing technologies, notably the potential for site-specific
engineering. However, the required cryogenic temperatures for the functionality
of these sources have been an inhibitor of their full potential. Existing
strain engineering methods face fundamental challenges in extending the working
temperature while maintaining the emitter's fabrication yield and purity. In
this work, we demonstrate a novel method of designing site-specific
single-photon emitters in atomically thin WSe$_2$ with near-unity yield
utilizing independent and simultaneous strain engineering via nanoscale
stressors and defect engineering via electron-beam irradiation. Many of these
emitters exhibit exciton-biexciton cascaded emission, purities above 95%, and
working temperatures extending up to 150 K, which is the highest observed in
van der Waals semiconductor single-photon emitters without Purcell enhancement.
This methodology, coupled with possible plasmonic or optical micro-cavity
integration, potentially furthers the realization of future scalable,
room-temperature, and high-quality van der Waals quantum light sources.
