Dominant Role of Sulphur divacancy in Charge Trapping Dynamics in MoS$_2$

TL;DR

This study reveals that Sulphur divacancies in monolayer MoS$_2$ have a dominant role in charge trapping due to their high capture coefficients, significantly impacting nonradiative recombination and quantum yield.

Contribution

First-principles calculations demonstrate the dominant charge trapping role of Sulphur divacancies over other defects in MoS$_2$.

Findings

Sulphur divacancies have capture coefficients about 10^{-9} cm^3/s.

Single Sulphur vacancies have much smaller capture coefficients (~10^{-16} cm^3/s).

Sulphur divacancies significantly enhance nonradiative recombination.

Abstract

Intrinsic defects govern carrier trapping and recombination in two-dimensional semiconductors, yet the microscopic origin of defect-dependent capture dynamics remains unclear. Here, we compute carrier capture coefficients of vacancy defects, treating monolayer MoS$_2$ as a prototype, from first principles. We find that the single Sulphur vacancy forms a shallow defect with a small capture coefficient of $\sim 10^{-16}\ \mathrm{cm}^3/\mathrm{s}$, whereas the Sulphur divacancy exhibits a capture coefficient larger by seven orders of magnitude, $\sim 10^{-9}\ \mathrm{cm}^3/\mathrm{s}$, despite being only moderately deeper in energy. This enhancement originates from strong lattice relaxation enabling efficient multiphonon capture. Consequently, single vacancies contribute weakly to trapping, while Sulphur divacancies dominate nonradiative recombination and reduce quantum yield. In contrast, molybdenum vacancies and Sulphur antisites, although deep, show much smaller capture coefficients, indicating a limited role in carrier trapping in n-type devices.