Effects of energy correlations and superexchange on charge transport and exciton formation in amorphous molecular semiconductors: An ab initio study

Andrea Massé, Pascal Friederich, Franz Symalla, Feilong Liu, Velimir Meded, Reinder Coehoorn, Wolfgang Wenzel, and Peter A. Bobbert
Phys. Rev. B 95, 115204 – Published 31 March 2017

Abstract

In this study, we investigate on the basis of ab initio calculations how the morphology, molecular on-site energies, reorganization energies, and charge transfer integral distribution affect the hopping charge transport and the exciton formation process in disordered organic semiconductors. We focus on three materials applied frequently in organic light-emitting diodes: αNPD, TCTA, and Spiro-DPVBi. Spatially correlated disorder and, more importantly, superexchange contributions to the transfer integrals, are found to give rise to a significant increase of the electric field dependence of the electron and hole mobility. Furthermore, a material-specific correlation is found between the HOMO and LUMO energy on each specific molecular site. For αNPD and TCTA, we find a positive correlation between the HOMO and LUMO energies, dominated by a Coulombic contribution to the energies. In contrast, Spiro-DPVBi shows a negative correlation, dominated by a conformational contribution. The size and sign of this correlation have a strong influence on the exciton formation rate.

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  • Received 9 January 2017

DOI:https://doi.org/10.1103/PhysRevB.95.115204

©2017 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Andrea Massé1, Pascal Friederich2, Franz Symalla2, Feilong Liu1, Velimir Meded2, Reinder Coehoorn1,3, Wolfgang Wenzel2, and Peter A. Bobbert1,*

  • 1Department of Applied Physics, Technische Universiteit Eindhoven, P.O. Box 513, NL-5600 MB Eindhoven, The Netherlands
  • 2Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), D-76344 Eggenstein-Leopoldshafen, Germany
  • 3Institute for Complex Molecular Systems, Technische Universiteit Eindhoven, P.O. Box 513, NL-5600 MB Eindhoven, The Netherlands

  • *p.a.bobbert@tue.nl

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Issue

Vol. 95, Iss. 11 — 15 March 2017

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