Investigating the role of dark excitons on electron-hole liquid photoluminescence in monolayer transition-metal dichalcogenides

Enhanced Emission from Defect Levels in Multilayer MoS2

“…Two possible mechanisms have been previously associated with abrupt changes in PL intensity: electron-hole liquid formation [28][29][30][31][32][33] and a thermally driven electronic structure transition. [34] The possibility of electron-hole liquid formation can be ruled out since it requires large exciton binding energies that are only present in monolayer dichalcogenides (see Figure S10 in the Supporting Information for a more detailed discussion).…”

“…Similar defect emission behaviors were observed when the sample temperature is increased. Such an abrupt PL intensity increase under high laser fluence or high temperatures is usually signatures of either electron–hole liquid formation [ 28–33 ] or a thermally driven electronic structure transition. [ 34 ] We rule out the former option and attribute the abrupt PL intensity increase to a thermally driven crossover from indirect exciton emission to stimulated emission from a defect level.…”

“…Similar defect emission behaviors were observed when the sample temperature is increased. Such an abrupt PL intensity increase under high laser fluence or high temperatures is usually signatures of either electronhole liquid formation [28][29][30][31][32][33] or a thermally driven electronic structure transition. [34] We rule out the former option and Realizing stimulated emission from defects in 2D-layered semiconductors has the potential to enhance the sensitivity of characterizing their defects.…”