Regioisomeric Fluorination in Donor–Acceptor Conjugated Polymers for Organic Thermoelectrics

Abstract Fluorinated donor–acceptor (D–A) conjugated polymers are promising organic thermoelectric (OTE) materials; however, the effects of fluorination pattern on their charge transport and doping behavior remain unclear. Herein, we present a regioisomeric design strategy wherein fluorine atoms were selectively introduced into either the donor or acceptor unit of benzothiadiazole-quaterthiophene polymers to generate F-D and F-A, respectively. This regioselective fluorination induced distinct molecular conformations and electronic distributions, thereby influencing charge transport and charge transfer with molecular dopants. Consequently, the donor-fluorinated polymer F-D exhibited enhanced backbone planarity, higher carrier mobility, and a more favorable balance between carrier concentration and the Seebeck coefficient. Specifically, doped F-D achieved a higher maximum power factor of 43.5 μW m–1 K–2 than F-A (23.0 μW m–1 K–2) and delivered superior thermoelectric performance, with figures of merit of 0.056 for F-D and 0.026 for F-A. Notably, F-D also exhibited greater air stability, retaining 82% of its initial power factor after 7 days under ambient conditions, compared with 39% for F-A. Collectively, these results highlight the critical role of fluorinated regioisomerism in determining the thermoelectric performance and air stability of D–A conjugated polymers, thereby providing valuable guidance for the molecular design of advanced OTE materials.