Complex Exciton Dynamics in Materials: a First-Principles Computational Approach

Understanding the energetics and dynamics of excited states formed by light-matter interactions is essential for applications across optoelectronics and photophysics. In systems of reduced dimensionality, strongly-bound excitons serve as the main energy carriers, with long diffusion and relaxation lifetimes. As exciton dynamics are coupled to optical selection rules that stem from the atomic structure, enhanced exciton transport efficiency can be achieved through local structural modifications, such as atomic impurities and interface design, as well as crystal fluctuations. Yet current theories lack a predictive description of the underlying interactions due to such structural modifications, highlighting the need for new tools that can capture these complex exciton dynamics.Taking advantage of ever-growing computational frontiers, in this ERC project, we will derive and apply a new theoretical approach, based on the predictive many-body perturbation theory, to compute exciton dynamics as a function of structural complexity in emerging materials. We will derive and examine our approach on three emerging excitonic systems of reduced dimensionality: organic molecular crystals, layered transition metal dichalcogenides, and two-dimensional hybrid perovskites [Obj.I]. As proof-of-concept, we will use our theory to study the effect of atomic defects and heterostructure compositions [Obj.II], as well as lattice fluctuations [Obj.III], on the mechanisms dominating exciton relaxation and diffusion and their resulting mobility and lifetime.Our research will thus allow for a comprehensive and predictive understanding of the underlying physics dominating exciton decay processes in materials of emerging interest via front-line computations, offering novel and tunable design principles for optimized functionality.