Phonon-assisted Photoluminescence and Exciton Lifetime in Solids from First Principles

Time-resolved photoluminescence spectroscopy (TRPL) reveals many important dynamical many-body phenomena including phonon-assisted recombination of indirect excitons. However, such signatures in the PL spectrum and their dynamical processes are not yet been fully understood at an atomistic level. We present a universal first-principles methodology based on Heisenberg equation of motion to calculate the phonon-assisted photoluminescence spectrum and exciton lifetime at finite temperature. In particular, this approach can describe the exciton lifetime including both radiative recombination and exciton-phonon scattering simultaneously from first-principles. We further analyze the phonon mode contribution and emphasize the relaxation pathway and dephasing lifetime through each scattering channel to explain the experimental measurements in vdW layered materials. We emphasize that first-principles phonon-assisted transitions are crucial for an in-depth understanding of exciton dynamics in solids.