Electron mobility in the 1:1 charge-transfer crystal phenanthrene-PMDA

Abstract

Electron drift mobilities have been measured in single crystals of the 1:1 charge transfer complex phenanthrene-pyromellitic-acid-dianhydride (PMDA) as a function of temperature and crystal direction. The mobility shows an activated temperature dependence and has a maximum value along the short crystal stack axis of alternating donor and acceptor molecules. The magnitude of the mobility at room temperature, 10-2 cm2/V s, and the measured activation energy of 880 cm-1 is consistent with electron motion which can be described within the framework of small polaron theory. The anisotropy of the mobility suggests that the excess electron wavefunction responsible for electron motion is delocalized over the donor molecules as well as the acceptor molecules. © 1975.