We study exciton radiative decay in a two-dimensional material, taking into
account large thermal population in the non-radiative states, from which
excitons are scattered into the radiative states by acoustic phonons. We find
an analytical solution of the kinetic equation for the non-equilibrium
distribution function of excitons in the radiative states. Our estimates for
bright excitons in transition metal dichalcogenides indicate a strong depletion
of radiative state population due to insufficient exciton-phonon scattering
rate at low temperatures.Comment: 8 pages, 4 figure