Dual-Polarity Thermoelectric Generation from a Single Polymer-Dopant System

Abstract

Seebeck coefficient sign inversion in highly doped organic semiconductors provides an unconventional route to dual-polarity thermoelectric generation without relying on unstable n-type materials, yet its physical origins remain poorly understood. Here, we demonstrate that systematic chemical doping can induce multiple Seebeck coefficient inversions, enabling access to both p-type and n-type thermoelectric regimes within a single material system. Kinetic Monte Carlo simulations quantitatively reproduce both our experiments and literature data and show that the polarity transitions arise from the interplay between density of states filling and the opening of a Coulomb gap near the Fermi energy. These results establish a unified framework for polarity inversion and identify the conditions required to achieve dual polarity through doping. Guided by this framework, we realize a conductivity-matched dual polarity thermoelectric generator based on a single polymer-dopant system, illustrating the broader potential of polarity control in organic thermoelectrics.