Optical evidence for intermolecular coupling in mixed films of pentacene and perfluoropentacene

TL;DR

This study uses optical spectroscopy to demonstrate intermolecular coupling in mixed pentacene and perfluoropentacene films, revealing a new transition at 1.6 eV indicative of molecular interactions.

Contribution

It provides direct optical evidence of intermolecular coupling in mixed organic films, identifying a new spectral transition linked to PEN and PFP interactions.

Findings

Identification of a new 1.6 eV transition due to coupling

Spectral shape influenced by mixing ratios

Distinction between intermolecular and intramolecular transitions

Abstract

We present optical absorption spectra of mixed films of pentacene (PEN) and perfluoropentacene (PFP) grown on SiO2. We investigated the influence of intermolecular coupling between PEN and PFP on the optical spectra by analyzing samples with five different mixing ratios of PFP:PEN with variable angle spectroscopic ellipsometry (VASE) and differential reflectance spectroscopy (DRS). The data show how the spectral shape is influenced by changes in the volume ratio of the two components. By comparison with the pure film spectra an attempt is made to distinguish transitions due to intermolecular coupling between PEN and PFP from transitions caused by interactions of PEN (PFP) with other molecules of the same type. We observe a new transition at 1.6 eV which is not found in the pure film spectra and which we assign to coupling of PFP and PEN.