Excitonic performance and ultrafast dynamics in defective WSe2

Abstract

Understanding and facilitating defects in two-dimensional transition metal dichalcogenides (TMDCs) are of fundamental importance for their application in optoelectronic devices and valleytronic devices. In this study, swift heavy ion (SHI) irradiation was applied to introduce defects in monolayer WSe2 in a controlled manner. Temperature-dependent photoluminescence and transient absorption spectroscopy are employed to investigate the excitonic performances in defective WSe2. It is observed that the trion emission rises up alongside exciton emission for WSe2 irradiated with elevated ion fluences. Defects introduced by SHI irradiation can strongly localize carriers and weaken the exciton-phonon coupling and further affect the optical signatures of the excitons. Photoexcited electron-hole pairs were suppressed to form excitons due to the weaken phonon scattering, and the population of exciton was reduced for the irradiated WSe2. These results reveal that SHI irradiation is an effective technique to explore defect dependence of exciton formation and evolution dynamics in TMDCs, which have important implications for various optoelectronic applications.