Direct evidence for delocalization of charge carriers at the Fermi level in a doped conducting polymer.
The infrared absorption spectrum of the polaron charges at the Fermi level EF in a heavily p-doped conducting poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) film has been measured using interferogram-modulated Fourier-transform charge-modulation spectroscopy. The spectrum indicates softer phonons and weaker electron-phonon coupling riding on a strongly redshifted Drude-like electronic transition, different from the population-averaged "bulk" spectrum. This provides direct evidence that the EF holes are sufficiently delocalized even in such disordered materials to reside in an energy continuum (band states) while the rest of the hole population resides in self-localized gap states.
Department of Chemistry, National University of Singapore, Lower Kent Ridge Road, Singapore 117543.
Jing-Mei
JM
Zhuo
Li-Hong
LH
Zhao
Perq-Jon
PJ
Chia
Wee-Sun
WS
Sim
Richard H
RH
Friend
Peter K H
PK
Ho