UC Berkeley

The interaction between excitons and phonons is fundamental to the nature and fate of photoexcitatons in solids, with important implications for spectroscopy and transport measurements, and for applications in optoelectronics and clean energy. In this dissertation, we present recent advances in computing exciton-phonon interactions from first principles. We implement a recently proposed linear-response reciprocal space-based framework which involves contracting electron-phonon matrix elements computed from density functional perturbation theory (DFPT) with exciton expansion coefficients obtained after building and diagonalizing the ab initio Bethe-Salpeter Hamiltonian, which is built on density functional theory and the GW approximation. We apply this formalism in unique ways to study phenomena related to exciton-phonon interactions, namely the nature of exciton diffusion in acene crystals, the dynamical screening of excitons in halide perovskites due to lattice vibrations, and the asymmetric lineshapes in MoS2 stemming from off-diagonal exciton-phonon coupling.