Photoluminescence Study of B-Trions in MoS₂ Monolayers with High Density of Defects

Photoluminescence spectroscopy has been used to investigate the details of B band emission from single-layer MoS₂ samples grown by chemical vapor deposition. The evolution of the peak shape upon variable excitation power is well described by a combination of exciton and trion contributions, from which B trion binding energy of 18 meV has been extracted. It has been suggested that the absence of accompanying A trion emission in our samples, as well as the enhanced intensity of the B band, can be ascribed to a fast non-radiative recombination channel arising from the large defect density in our samples. It has been found that band-selective recombination channels or formation of dark/bright trions are possible microscopic scenarios for our observations.