Significant enhancement of exciton emission in monolayer WS2 treated by oleylamine ligands

Abstarct We report a significant enhancement in photoluminescence (PL) of the monolayer WS 2 treated by oleylamine ligands. After oleylamine treatment, the dominant component of the PL is converted from negative trions to excitons, indicating that the majority of excitons can recombine without forming trions. This treatment enhances exciton emission by passivating surface defects, thus reducing nonradiative recombination through surface trap states. The femtosecond transient absorption spectra further confirm that defect passivation by oleylamine ligands results in a much slower recovery of exciton resonance, reflecting suppression of early-time nonradiative recombination accompanied by a significant enhancement of exciton emission.