Exciton–Phonon Coupling and Transport Pathways in Complex Semiconductors from First Principles

Exciton dynamics in solids arise from the interplay of electronic structure, lattice vibrations, and electron–hole correlations, and play a central role in determining the functionality of materials used in energy conversion, optoelectronics, and quantum technologies. Here, I will present recent developments in first-principles Green’s function frameworks based on the ab initio Bethe–Salpeter equation that enable predictive calculations of exciton–phonon interactions and their consequences for excitonic properties across complex inorganic semiconductors, 2D materials, and organic molecular crystals. In novel semiconductors such as halide perovskites and transition metal oxides, we predict that dynamical phonon screening reshapes exciton character and can drive ultrafast exciton dissociation, generating free carriers on sub-100-fs timescales across a broad temperature range. In monolayer and bilayer van der Waals heterostructures, we compute that exciton–phonon scattering governs picosecond thermalization and enables sub-100-fs intralayer-to-interlayer exciton transfer. For organic crystals, maximally localized exciton Wannier functions provide access to both phonon-driven band-like transport and polaronic hopping regimes, revealing how local and nonlocal exciton–phonon coupling dictate temperature-dependent diffusion. I will discuss how these studies offer new insight into electron-hole interactions, highlight how lattice-driven processes influence nonequilibrium carrier and exciton dynamics, and explain experiments involving excitonic processes in complex materials.