Abstract
The d.c. conductivity σ dc and the thermopower S of a number of polyacene quinone radical polymers obey the relationship σ dc = σ o exp (− T o / T) 1 3 and S/T = a+bT − 1 3 , typical for two-dimensional variable-range hopping. The results can be explained by Mott's model modified, however, by allowing for a linearly varying density of states near the Fermi level, and by taking into account the form of the wave function of the localized states. Special attention is paid to the prefactor σ o which contains important hopping parameters, such as a frequency factor ν o, usually assumed to be not higher than a typical phonon frequency (∼ 10 13 s −1). The original calculation of Miller and Abrahams (MA) of the hopping rate, however, gives ν o values ranging from 10 16 to 10 21 s −1. For the PAQR polymers reasonable estimates of the parameters are obtained when using MA expressions adapted for two-dimensional systems.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.