Controlling Charge Carrier Lifetime in Defective WSe2 Monolayer through Interface Engineering: a Time-Domain Ab Initio Study

Trap states induced by chalcogenide vacancies in defective transition metal dichalcogenide (TMDs) monolayers are detrimental to both the charge carrier lifetime and device efficiency. To address this, chemically functionalizing the surface of defective TMD monolayers is crucial. Experimental methods such as thiol grafting on chalcogenide vacancies, oxygen passivation, and the physisorption of electroactive molecules have been explored for defect healing. Our study, using ab initio time-domain density functional theory and nonadiabatic molecular dynamics, shows that C₂₀ molecular adsorption and oxygen passivation effectively mitigate nonradiative electron–hole recombination and enhance carrier charge lifetime in defective WSe₂ beyond that of pristine WSe₂ monolayers. These improvements stem from the combined effects of energy gap variations, nonadiabatic coupling, and decoherence time, resulting from either hole-trap-assisted processes or direct interactions between free electrons and holes. Our findings suggest that healing chalcogenide vacancies in defective TMDs enables precise control over charge carrier lifetime, advancing defect engineering in 2D materials.