Molecular Doping-Driven Modulation of Domain Charge Transport Elevates Thermoelectric Performance in Polar Polythiophene

Unlocking outstanding thermoelectric performance in conjugated polymers (CPs) hinges on overcoming their intrinsically low charge mobility, resulting from their mixed crystalline–amorphous nature. Central to this challenge is to achieve synergistic intra- and interdomain charge transport in doped CPs. Taking polar polythiophene p(g32T-T) as a model system, we demonstrate that ion exchange doping synergistically improves charge transport across both ordered and disordered regions, establishing a power factor of 63 μW m–1 K–2, a considerable leap forward for polar polythiophenes. We highlight that excess doping induced a solid-state molecular reorientation from edge-on to face-on, initiating a decline in charge mobility within crystalline domains, despite improvements in interdomain charge transport. Furthermore, we showcase a quantitative methodology to probe interdomain transport efficiency, taking activation energy Wγ derived from weighted mobility as a key indicator. This study delineates a sophisticated framework for examining charge transport, underscoring the importance of fine-tuning both the amorphous and the crystalline regions.