Excitons in organic semiconductors

In this article, excitonic effects in organic semiconductors investigated within the framework of many-body perturbation theory are reviewed. As an example for this technologically relevant class of materials the oligoacene series is studied. The electron-hole interaction is included by solving the Bethe-Salpeter equation for the electron-hole Green's function. This approach allows for the evaluation of the exciton binding energies, which are of major interest concerning the application in organic opto-electronic devices. We start the discussion with a comparison of the Kohn-Sham band structure with recent angular resolved photo-emission data. Starting from this one-electron band structure we focus on the impact of the electron-hole interactions on the optical properties by solving the Bethe-Salpeter equation. We demonstrate the dependence of the exciton binding energy on the molecular size and emphasize the effect of the intermolecular interaction on the exciton binding energies by means of pressure investigations. To cite this article: P. Puschnig, C Ambrosch-Draxi, C R. Physique 10 (2009). (C) 2008 Acade mie des sciences. Published by Elsevier Masson SAS. All rights reserved.