Holes, Electrons, Polarons, and Bipolarons and the Thermodynamics of Electrically Active Dopants in Conducting Polymers

Abstract

This paper describes how measurements of the reversible (equilibrium) distribution of an electrically active dopant, between an external phase and a conducting polymer, can be used to investigate both electronic species and electron energy level structures in such polymers. Examples are presented, involving conventional inorganic semiconductors, and it is shown how complications anticipated with conducting polymers have occurred and been overcome in these systems. Following this, experiments on both absorption isotherms and conductivity for vapor phase iodine in both polythiophene and azite are described and analyzed for the determination of relevant species. The formations of triiodide and pentaiodide ions are indicated, and bipolarons appear to form in polythiophene.