Backbone Asymmetry Modification in Amphipathic Conjugated Polymers Enables Record n-Type Organic Thermoelectrics

Achieving high-performance n-type organic thermoelectrics (OTEs) has lagged behind p-type counterparts due to limited electrical conductivity and power factor (PF). Here, we report two n-type amphipathic conjugated polymers, Pg₅DPP-BBTz and Pg₅DPP-TBZ, based on glycolated thiophene-diketopyrrolopyrrole units, engineered via backbone modification to enhance charge transport. Replacing a symmetric sp²-sulfur atom in Pg₅DPP-BBTz with an sp²-nitrogen atom yields the asymmetric Pg₅DPP-TBZ, which exhibits stronger π-π stacking, a more favorable density of states distribution, and extended charge delocalization. When sequentially doped with N-DMBI, Pg₅DPP-TBZ achieves an electrical conductivity of 145.6 ± 1.5 S cm^-1 and a record-high PF of 385 ± 16 µW m^-1 K^-2-surpassing previous n-type OTEs and rivalling top p-type materials. This performance stems from high charge mobility, large delocalization, and mitigated carrier-carrier repulsion. Combined with a low thermal conductivity (0.37 W m^-1 K^-1), a ZT of 0.30 ± 0.02 is realized. Our work demonstrates that subtle backbone modification in amphipathic polymers is a powerful strategy to advance n-type thermoelectrics.