Estimation of Exciton Binding Energy and lifetime for Mono-layer Transition Metal Dichalcogenides

Abstract

In this work, we present a mathematical model for the Wannier-Mott exciton in monolayers of transition metal dichalcogenides such as $WS_2$, $WSe_2$, $MoS_2$, $MoSe_2$ that estimates the radiation lifetime in the effective mass approximation. We calculate exciton energy, and binding energy by solving the Schrodinger wave equation with open boundary conditions to obtain quasi-bound states in the confined direction in the monolayer and decay rates by the Fermi-Golden rule. The proposed model uses only the physical parameters such as band offsets, effective mass, and dielectric constants for the monolayers of $WS_2$, $WSe_2$, $MoS_2$, and $MoSe_2$. The model is validated against III-V material quantum well heterostructure, and the estimated effective lifetime considering the thermalization of the exciton has been compared with photoluminescence decay for the TMD heterostructure. Our calculated values show good agreement with the time-resolved photoluminescence spectroscopy measurements and DFT estimations.