Princeton University

School of Engineering & Applied Science

Origin of the Orientation Dependence of Ionization Energy and Electron Affinity in Organic Molecular Films

Dr. Hiroyuki Yoshida
E-Quad, B-418
Monday, December 1, 2014 - 2:00pm

It has recently been reported that the ionization energy of organic solid depend on the molecular orientations, though the precise reason has not yet been clarified.  We determine the electron affinities of the thin films of pentacene and perfluoropentacene with different molecular orientations using low-energy inverse photoemission spectroscopy.  The values together with the ionization energies in solids as well as the parameters in gas phase taken from the literature, we determined the contribution of the polarization energy, bandwidth, and molecular orientation on the ionization energy and electron affinity in the solid states.  Based on the obtained data, we discuss the origin of the orientation dependence of ionization energy and electron affinity.