Transformation of polarons to bipolarons in disordered matter

TL;DR

This paper investigates how broadband ac electric fields induce a transition from polarons to bipolarons in disordered media, confirmed by impedance measurements and conductivity analysis, revealing new insights into charge carrier transformations.

Contribution

It introduces a novel mechanism for polaron to bipolaron transition driven by ac fields and disorder, supported by experimental impedance and conductivity data.

Findings

AC conductivity increases with frequency during transition

Magnetic inductivity decreases as bipolarons form

Disorder enhances polaron-bipolaron transformation

Abstract

The polaron to bipolaron transition in disordered media under the influence of a broadband ac electric field is suggested: ac conductivity vs. frequency measurements in disordered media with inhomogeneous disorder induce spatio-temporal fluctuations of the density of polarons yielding polaron to bipolaron transformation. The external field results in the transition, alternatively to an increasing doping level. The assertion is confirmed by performing successive complex impedance measurements in disordered media. A systematic increase of the real part of the ac conductivity in the frequency domain, followed by mutual reduction of the magnetic inductivity of conducting polypyrrole, are explained.