Absorption of Gaseous Iodine by Polythiophene Films and Powders,

摘要

Further determinations of the reversible absorption isotherms of iodine (vapor) in both polythiophene films and powders are performed. The films exhibit isotherms of iodine uptake vs. iodine pressure which, at low pressures, are concave downward at low temperatures and concave upward at higher temperatures. This behavior is interpreted in terms of hole-electron equilibria. At a pressure of about 0.68 torr all film isotherms exhibit a discontinuous slope to saturation. The powder isotherms followed those for the film up to the discontinuity, do not exhibit the discontinuity, and continue to absorb iodine as the pressure is increased. By mixing helium into the iodine vapor, we demonstrate that the discontinuity occurs when the total gas pressure is in the neighborhood of 0.68 torr. The phenomenon is explained in terms of a electrochemical instability caused by the formation of a Schottky diode at the film-substrate interface. Reprints. (aw)