Long-wavelength continuum model for molecular excitonic systems: Spectroscopic and dynamic signatures

Excitonic systems based on organic dye molecules such as molecular crystals and aggregates promise practical advantages in optoelectronic applications. In addition to the tunability of the molecular structure and composition, their packing conditions critically affect the excitonic dispersion through short-range interactions sensitive to atomistic details, making generic understanding of exciton dynamics and spectroscopy difficult and non-transferable. We introduce exciton models based on a long-wavelength, continuum approximation that reliably predict selective spectroscopic and dynamic signatures. We show that these observables are robust against modifications of short-range interactions sensitive to molecular geometry and depend only on coarse-grained parameters that can be independently estimated. Several examples and possible extentions are discussed.