Large-Area Bright Emission of Plasmon-Coupled Dark Excitons at Room Temperature

Brightening dark excitons in transition metal dichalcogenide monolayers (MLs) can provide large-area ultrathin devices for applications in quantum information science and optoelectronics. For practical applications of dark excitons, a robust and bright emission over a wide area at room temperature is desirable; however, no reliable approach has been demonstrated thus far. In this study, an efficient approach is presented for brightening dark excitons at room temperature over a large area of a WSe₂ ML via coupling between plasmons and dark excitons. When a WSe₂ ML is placed on gold micropillars (Au MPs), dark excitons are efficiently coupled to strongly localized surface plasmons at the edges of the Au MPs, along with a strong photoluminescence (PL) emission. Room-temperature dark exciton emission is confirmed via energy-, angle-, and time-resolved spectroscopy experiments, as well as confocal PL mapping. This study provides a generalizable method for the practical application of dark exciton.