  The rich optical properties of transition metal dichalcogenide monolayers
(TMD-MLs) render these materials promising candidates for the design of new
optoelectronic devices. Despite the large number of excitonic complexes in
TMD-MLs, the main focus has been put on optically bright neutral excitons.
Spin-forbidden dark excitonic complexes have been addressed for basic science
purposes, but not for applications. We report on spin-forbidden dark excitonic
complexes in ML WSe$_2$ as an ideal system for the facile generation of
radially polarized light beams. Furthermore, the spatially resolved
polarization of photoluminescence beams can be exploited for basic research on
excitons in two-dimensional materials.
