Exciton properties of selected aromatic hydrocarbon systems

TL;DR

This study investigates singlet excitons in acene- and phenacene-type molecular crystals, revealing significant spectral differences and an increasing role of charge-transfer excitons with longer molecules.

Contribution

It provides the first comparative analysis of exciton properties in these two hydrocarbon families using electron energy-loss spectroscopy.

Findings

Spectral differences between acene and phenacene crystals.

Charge-transfer excitons become more prominent in longer molecules.

Excitation spectra vary significantly between the two families.

Abstract

We have examined the singlet excitons in two representatives of acene-type (tetracene and pentacene) and phenacene-type (chrysene and picene) molecular crystals, respectively, using electron energy-loss spectroscopy at low temperatures. We show that the excitation spectra of the two hydrocarbon families significantly differ. Moreover, close inspection of the data indicates that there is an increasing importance of charge-transfer excitons at lowest excitation energy with increasing length of the molecules.