Molecular\nDoping-Driven Modulation of Domain Charge\nTransport Elevates Thermoelectric Performance in Polar Polythiophene

Unlocking outstanding thermoelectric performance in conjugated\npolymers (CPs) hinges on overcoming their intrinsically low charge\nmobility, resulting from their mixed crystalline–amorphous\nnature. Central to this challenge is to achieve synergistic intra-\nand interdomain charge transport in doped CPs. Taking polar polythiophene\np­(g<sub>3</sub>2T-T) as a model system, we demonstrate that ion exchange\ndoping synergistically improves charge transport across both ordered\nand disordered regions, establishing a power factor of 63 μW\nm<sup>–1</sup> K<sup>–2</sup>, a considerable leap forward\nfor polar polythiophenes. We highlight that excess doping induced\na solid-state molecular reorientation from edge-on to face-on, initiating\na decline in charge mobility within crystalline domains, despite improvements\nin interdomain charge transport. Furthermore, we showcase a quantitative\nmethodology to probe interdomain transport efficiency, taking activation\nenergy <i>W</i><sub><i>γ</i></sub> derived\nfrom weighted mobility as a key indicator. This study delineates a\nsophisticated framework for examining charge transport, underscoring\nthe importance of fine-tuning both the amorphous and the crystalline\nregions.