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

Introduction

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.

Exciton Dynamics

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
• Interface design
• 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.

Theoretical Approach

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.

Emerging Systems

We will derive and examine our approach on three emerging excitonic systems of reduced dimensionality:

1. Organic molecular crystals
2. Layered transition metal dichalcogenides
3. Two-dimensional hybrid perovskites [Obj.I]

Proof-of-Concept Studies

As proof-of-concept, we will use our theory to study the effect of:

• Atomic defects and heterostructure compositions [Obj.II]
• Lattice fluctuations [Obj.III]

These studies will focus on the mechanisms dominating exciton relaxation and diffusion, as well as their resulting mobility and lifetime.

Conclusion

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.