Polarons in Conjugated Polyelectrolytes: A First-Principles Perspective

Conjugated polyelectrolytes (CPEs) comprised of conjugated backbones and pendant ionic functionalities are versatile organic semiconductors with myriad optoelectronic applications. Although polarons are dominant charge carriers in conducting CPEs owing to strong electron-phonon coupling, their properties are not well understood, especially from a first-principles perspective. In this study, a comprehensive study on the stability, structural deformation, electronic structure, and optical absorption of positive (or hole)/negative (or electron) polarons and bi-polarons in CPEs is conducted. It is explored how these properties depend on the electrostatic interaction between the polarons and ionic functionalities, including alkyl chains, ionic groups, and counterions. It is then examined how the bandgap, polaron binding energy, and optoelectronic structure of CPEs can be tuned by various combinations of the donor and acceptor units in their backbones. Finally, electrochemical stability of CPEs is studied and light is shed on the absence of negative polarons in CPEs. The strategy to improve the electrochemical stability of n-doped CPEs is also discussed.

Automated summary

This study comprehensively investigates the properties of polarons and bi-polarons in CPEs, including their stability, structural deformation, electronic structure, and optical absorption. The research reveals that these properties depend on the electrostatic interaction between the polarons and ionic functionalities, as well as the combinations of donor and acceptor units in the CPEs backbones. Additionally, the study sheds light on the electrochemical stability of CPEs and discusses strategies to improve it.