Sustained robust exciton emission in suspended monolayer WSe₂ within the low carrier density regime for quantum emitter applications

The development of semiconductor optoelectronic devices is moving toward low power consumption and miniaturization, especially for high-efficiency quantum emitters. However, most of these quantum sources work at low carrier density regions, where the Shockley-Read-Hall (SRH) recombination may be dominant and seriously reduce the emission efficiency. In order to reduce the effect of carrier trapping and sustain a strong photoluminescence (PL) emission under low power pumping conditions, we investigated the influence of "suspending" a monolayer of tungsten diselenide (WSe2), a novel two-dimensional quantum material. Not only the PL intensity but also the fundamental photoluminescence quantum yield (PLQY) has exhibited a huge, order-scale enhancement through suspending; even surprisingly, we found the PLQY improvement to be far significant under small pumping powers and observed an exponential increase in tendency toward an even lower carrier density region. With its strong excitonic effect, suspended WSe2 offers a solution to reduce carrier trapping and participate in non-radiative processes. Moreover, in the low-power range, where SRH recombination dominates, suspended WSe2 exhibited a remarkably higher percentage of excitonic radiation compared to contacted WSe2. Herein, we quantitatively demonstrate the significance of the suspended WSe2 monolayer in a low carrier density region, highlighting its potential for developing compact, low-power quantum emitters in the future.