n‑Type Polymer Thermoelectric Materials Based on Benzodifurandione and F‐Substituted Thiophene Derivatives Synthesized via Direct Arylation and Aldol Polycondensation

Abstract The preparation of n‐type conjugated polymers (CPs) with low‐lying lowest unoccupied molecular orbital (LUMO) energy levels is crucial for developing n‐type organic electronics. However, limited strategies have been demonstrated to significantly lower the LUMO of CPs. Herein, BDOPV is incorporated with strong electron affinity as the acceptor unit and the F‐substituted thiophene derivatives 4F2T and 4FTVT as the donor into the polymer chain, and two CPs PB4F2T and PB4FTVT are synthesized via an atom‐economic direct arylation monomer‐aldol polycondensation polymer procedure. The two polymers display LUMO below −4.0 eV to enable unipolar n‐type charge transport characteristics in organic thin‐film transistors (OTFTs) and facilitate the efficient n‐doping by N ‐DMBI in organic thermoelectric devices (OTEs). The OTEs fabricated using PB4F2T demonstrated enhanced thermoelectric performance, with a conductivity (σ) of 0.90 S cm⁻¹ and a power factor (PF) reaching up to 0.50 µW m⁻¹ K⁻ 2 . This work enriches the pool of unipolar electron transport polymer semiconductors by combining strong electron withdrawing unit with fluorinated donor comonomer via effective synthetic protocol.