Localization Effects in Asymmetrically Substituted Polythiophenes: Controlled Generation of Polarons, Dimerized Polarons, and Bipolarons

The attachment to polythiophenes of substituents with different electronic properties produces polymeric materials with unusual electrical and optical properties. Controlled generation of polarons, dimerized polarons, and bipolarons was achieved through the formation of moieties of high and low band gap energy along the polythiophene backbone. The occurrence of such quantum, wells decreased the recombination of the polarons in bipolarons as would be observed in symmetrically substituted polythiophenes. One of the most interesting consequences of this band-gap engineering is the ability of tuning the transport properties of these polymers. These novel characteristics make possible the formation of paramagnetic and diamagnetic conducting states through the control of the redox state. They may also enhance the polaron population available for singlet exciton conversion in electroluminescent devices. © 1995, American Chemical Society. All rights reserved.