Exciton dynamics in tungsten dichalcogenide monolayers

Abstract

The strong photoluminescence from monolayer WS₂ and WSe₂ paves the way for a range of optoelectronic applications and opens up the door for ultrafast carrier dynamics study. In this work, we observed that monolayer WS₂ and WSe₂ exhibited giant absorption in the visible frequency range. This phenomenon has been ascribed to the band nesting effect. We used time-resolved photoluminescence spectroscopy to study the absorption and recombination dynamics of the photocarriers in monolayer WS₂ and WSe₂. We found that some of the electron–hole pairs excited in the band nesting region initially relaxed to the K/K′ point and then underwent radiative decay. The decay and recombination of the photocarriers occurred rapidly and terminated within the sub-nanosecond timescale. The observed experimental results indicate the great potential of these materials in optoelectronic devices.