Complete description of ionization energy and electron affinity in organic solids: Determining contributions from electronic polarization, energy band dispersion, and molecular orientation

Hiroyuki Yoshida, Kazuto Yamada, Jun'ya Tsutsumi, and Naoki Sato
Phys. Rev. B 92, 075145 – Published 31 August 2015
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Abstract

Ionization energy and electron affinity in organic solids are understood in terms of a single molecule perturbed by solid-state effects such as polarization energy, band dispersion, and molecular orientation as primary factors. However, no work has been done to determine the individual contributions experimentally. In this work, the electron affinities of thin films of pentacene and perfluoropentacene with different molecular orientations are determined to a precision of 0.1 eV using low-energy inverse photoemission spectroscopy. Based on the precisely determined electron affinities in the solid state together with the corresponding data of the ionization energies and other energy parameters, we quantitatively evaluate the contribution of these effects. It turns out that the bandwidth as well as the polarization energy contributes to the ionization energy and electron affinity in the solid state while the effect of the surface dipole is at most a few eV and does not vary with the molecular orientation. As a result, we conclude that the molecular orientation dependence of the ionization energy and electron affinity of organic solids originates from the orientation-dependent polarization energy in the film.

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  • Received 25 February 2015
  • Revised 16 July 2015

DOI:https://doi.org/10.1103/PhysRevB.92.075145

©2015 American Physical Society

Authors & Affiliations

Hiroyuki Yoshida1,*, Kazuto Yamada1, Jun'ya Tsutsumi2, and Naoki Sato1

  • 1Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-001, Japan
  • 2Flexible Electronics Research Center, National Institute of Advanced Industrial Science and Technology, 1-1-1 Higashi, Tsukuba 305-8562, Japan

  • *Corresponding author: hyoshida@chiba-u.jp; Present address: Graduate School of Advanced Integrated Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba-shi 263-8522, Japan.

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Issue

Vol. 92, Iss. 7 — 15 August 2015

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