Issue 47, 2018

Polarized absorbance and Davydov splitting in bulk and thin-film pentacene polymorphs

Abstract

Pentacene is one of the most studied organic materials and in particular its optical properties have been the subject of intense research during the last two decades. In spite of such a widespread interest and of the extensive knowledge achieved so far, a number of issues are still debated. One of the most relevant questions concerns the role of polymorphism and how it affects the lowest-energy exciton, which appears in the visible region and is subject to a sizable Davydov splitting. We address this problem in a combined theoretical and experimental work, where the optical absorption properties of three pentacene polymorphs are investigated within the whole energy range of visible light. Optical spectra computed from first principles in the framework of many-body perturbation theory are directly compared with the polarization-resolved absorbance, measured for three different pentacene phases (the two bulk polymorphs and the thin-film phase). In this way, we unambiguously identify the two Davydov components of the first exciton and the optical fingerprints of each considered phase. With very good agreement between theory and experiment, we show that all polymorphs exhibit common features at the absorption onset, while phase-dependent characteristics appear only above 2 eV. We discuss the character of the lowest-lying singlet and triplet excitons, including dark ones, highlighting the contributions from the electronic bands and the role of the electron–hole interaction and of the local-field effects.

Graphical abstract: Polarized absorbance and Davydov splitting in bulk and thin-film pentacene polymorphs

Article information

Article type
Paper
Submitted
13 Oct 2018
Accepted
14 Nov 2018
First published
14 Nov 2018

Phys. Chem. Chem. Phys., 2018,20, 29724-29736

Polarized absorbance and Davydov splitting in bulk and thin-film pentacene polymorphs

C. Cocchi, T. Breuer, G. Witte and C. Draxl, Phys. Chem. Chem. Phys., 2018, 20, 29724 DOI: 10.1039/C8CP06384B

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements