Estimation of Lifetime of Excitons in Monolayer Transition Metal Dichalcogenides

In this work, we present a mathematical model for estimating the exciton lifetime in monolayer transition metal dichalcogenides (TMDs), including WS₂, WSe₂, MoS₂, and MoSe₂. The effective masses are calculated using density functional theory (DFT) within the local density approximation employing the Perdew-Zunger exchange-correlation functional (LDA-PZ). Anisotropic confinement is considered to evaluate the exciton binding energies, and the Fermi's Golden rule is applied to calculate the oscillator strength. The model is validated against an AlGaAs/GaAs double quantum well heterostructure with Coulomb interaction, and Keldysh-type screened Coulomb interaction is taken into account to evaluate the exciton ground-state properties in TMDs. The predicted binding energies (488-578 meV) and lifetimes (0.146-0.52 ns) obtained from our model for the monolayer TMDs are compared with the DFT-based models, other theoretical approaches, and reported time-resolved photoluminescence measurements.The effective lifetimes estimated by incorporating exciton thermalization effects show a good agreement with the photoluminescence decay measurements at room temperature. The present model relies solely on material parameters, and unlike the computationally intensive Green's-function-based Bethe-Salpeter Equation (GW-BSE) approaches, offers an efficient method for predicting exciton energies and lifetimes in two-dimensional semiconductors.