Issue 11, 2020

Charge transfer excitons in a donor–acceptor amphidynamic crystal: the role of dipole orientational order

Abstract

Large amplitude motions in molecular solids are responsible for anomalous electrical characteristics in amphidynamic crystals. We study the effect of orientational dipolar disorder on charge transfer excitons (CTEs) in a donor–acceptor amphidynamic co-crystal of perylene–tetrabromophthalic anhydride (–TBPA). This co-crystal offers long range positional order of alternating donor and acceptor molecular entities arranged in stacks. Further it has a phase transition at 250 K due to progressive freezing of the dipolar orientational motion in the TBPA permanent dipole. The optical absorption band and photoluminescence at the semiconductor gap consists of at least three energetically separated CTE resonances that cover a spectral range of more than 400 meV. As the temperature is lowered below the phase transition the CTE band remains broad, but shows a shift of ∼150 meV to higher energy. On the basis of optical reflectivity, photoluminescence, and model calculations we interpret the room temperature CTE band as a collection of resonances in which at least one the nearest neighbour dipoles to the CTE is flipped from their lowest energy configuration. This first comprehensive optical investigation on an amphidynamic co-crystal demonstrates the importance of understanding the role of permanent dipoles in the CTE photophysics of organic semiconductors.

Graphical abstract: Charge transfer excitons in a donor–acceptor amphidynamic crystal: the role of dipole orientational order

Supplementary files

Article information

Article type
Communication
Submitted
25 jun 2020
Accepted
25 aug 2020
First published
25 aug 2020
This article is Open Access
Creative Commons BY-NC license

Mater. Horiz., 2020,7, 2951-2958

Charge transfer excitons in a donor–acceptor amphidynamic crystal: the role of dipole orientational order

J. W. R. Macdonald, G. Piana, M. Comin, E. von Hauff, G. Kociok-Köhn, C. Bowen, P. Lagoudakis, G. D'Avino and E. Da Como, Mater. Horiz., 2020, 7, 2951 DOI: 10.1039/D0MH01044H

This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence. You can use material from this article in other publications, without requesting further permission from the RSC, provided that the correct acknowledgement is given and it is not used for commercial purposes.

To request permission to reproduce material from this article in a commercial publication, 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 commercial 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