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Issue 16, 2019
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Neutral and defect-induced exciton annihilation in defective monolayer WS2

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Abstract

As defects and exciton–exciton annihilation (EEA) frequently govern the properties of nanoscale optoelectronic devices based on monolayer transition metal dichalcogenides (TMDCs), understanding the interaction between defects and EEA is of fundamental importance. Here we perform a systematic investigation of the effect of defects on EEA of neutral excitons and defect-bound excitons in monolayer WS2, using fluorescence lifetime imaging technology. Scanning transmission electron microscopy confirms the creation of atomic-scale defects introduced by argon plasma treatment in defective WS2. Defects can bind neutral excitons or trions to form defect-bound excitons. And defects have a slight effect on the lifetime of neutral excitons. However, owing to the impeded exciton diffusion caused by defects, the EEA rate of neutral excitons reduces from 0.26 cm2 s−1 in the pristine monolayer to 0.16 cm2 s−1 in the defective monolayer. For defect-bound excitons, the EEA rate of 0.068 cm2 s−1 is obtained, which results from the localized nature of defect-bound excitons and suppressed exciton diffusion. Our results reveal the important role of defect–EEA interactions in tailoring the properties of monolayer TMDCs.

Graphical abstract: Neutral and defect-induced exciton annihilation in defective monolayer WS2

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Publication details

The article was received on 30 Jan 2019, accepted on 22 Mar 2019 and first published on 27 Mar 2019


Article type: Paper
DOI: 10.1039/C9NR00967A
Citation: Nanoscale, 2019,11, 7913-7920

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    Neutral and defect-induced exciton annihilation in defective monolayer WS2

    H. Liu, C. Wang, D. Liu and J. Luo, Nanoscale, 2019, 11, 7913
    DOI: 10.1039/C9NR00967A

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