Position-dependent selenium substitution in conjugated polymers for enhanced doping efficiency and thermoelectric performance

초록

Organic thermoelectric materials have gained significant attention as sustainable energy solutions due to their flexibility, low-cost processing, and potential for near-room-temperature applications. However, achieving a high power factor through balancing electrical conductivity and the Seebeck coefficient in conjugated polymers (CPs) remains a key challenge. To address this challenge, we systematically investigated the position-dependent effects of selenium substitution in p-type donor–acceptor CPs. Three CPs of PDFD-Se, PSeDFD-T, and PSeDFD-Se were synthesized as derivatives of PDFD-T(L), incorporating selenium in place of sulfur inside the thiophene and/or benzothiadiazole units. In-depth analysis was conducted to reveal the impact of selenium substitution on HOMO energy levels, interactions with dopants, and molecular packing orientation of CPs, which collectively enhance doping efficiency and electrical conductivity. Notably, PSeDFD-Se exhibited a high conductivity of 239.5 S cm−1 at 0.1 wt% FeCl3, achieving the highest power factor of 59.7 μW m−1 K−2 among the series. This study highlights that the introduction of beneficial heteroatoms in appropriate positions inside CPs is critical in achieving high-performance organic thermoelectric materials.

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