Exciton dynamics in different aromatic hydrocarbon systems

TL;DR

This paper investigates exciton dispersion in four aromatic hydrocarbons using a Frenkel exciton model fitted to experimental electron scattering data, finding good agreement and suggesting limited charge-transfer exciton influence.

Contribution

It provides a detailed analysis of exciton dispersion in specific organic solids and refines the Hamiltonian model to better match experimental observations.

Findings

Theoretical dispersion curves align well with experimental data.

Charge-transfer excitons have limited impact on exciton dispersion.

Upgraded Hamiltonian improves modeling of Davydov splitting.

Abstract

The exciton dispersion is examined in the case of four selected prototypical molecular solids: pentacene,tetracene,picene,chrysene. The model parameters are determined by fitting to experimental data obtained by inelastic electron scattering. Within the picture that relies on Frenkel-type excitons we obtain that theoretical dispersion curves along different directions in the Brillouin zone are in good agreement with the experimental data, suggesting that the influence of charge-transfer excitons on exciton dispersion of the analyzed organic solids is not as large as proposed. In reciprocal space directions where Davydov splitting is observed we employ the upgraded version of Hamiltonian used in Materials 11, 2219 (2018).