Defect-Type-Dependent Carrier Lifetimes in Monolayer WS₂ Films

Abstract

The band-edge carrier recombination rate determines the internal quantum efficiency of light-emitting diodes (LEDs), which is predominantly determined by the carrier lifetime. Point defects in transition metal dichalcogenides (TMDs) as dominant nonradiative recombinations affect the carrier lifetimes, hindering photon emission. Uncovering the mechanism of different defect types on carrier lifetimes in TMDs is still controversial and challenging. Here, we combine time-resolved photoluminescence measurement with nonadiabatic molecular dynamics calculation to explore the band-edge carrier lifetime in monolayer WS2 with three typical kinds of defects. We have found that vacancy defects and compensatory doping defects in TMDs lead to decreased band-edge carrier lifetimes by 2 or 1 order of magnitude compared with pristine WS2, respectively. We attribute the difference to the phonon modes involved in electron–phonon coupling caused by defect types. Such an insight into the carrier lifetime can help modulate the defects in TMDs, so as to improve the performance of LEDs in the future.