ELECTROCHEMICAL DOPING PROPERTIES AND ELECTRONIC STATES OF POLY(3-PHENYLTHIOPHENE)

Electrochemical, optical, and magnetic properties in poly(3-phenylthiophene), as a function of doping and electronic states, are discussed in detail. The band gap of poly(3-phenylthiophene) was evaluated to be 2.0 eV, and similar to that of polythiophene. The evolution of localized states is evidenced by the spectral change with electrochemical doping. The spin density evaluated from the susceptibility was consistent with the polaron density assumed to be formed by a very small quantity of dopants. These results are interpreted in terms of the polaron and bipolaron models. The electronic band structure of poly(3-phenylthiophene) was determined. The top of the valence band of poly(3-phenylthiophene) is located at a higher energy state than that of polythiophene by about 0.1 eV and it became clear that the dopant in poly(3-phenylthiophene) is relatively stable compared with that in polythiophene. Successful n-type doping in poly(3-phenylthiophene) was also confirmed.