Residue-Free Liquid-Crystal Molecular Additive Enables the Significant Improvement of Power Factor for Simple Quinoid Thermoelectric Polymer

초록

Quinoid polymers featured with high-spin ground states hold great potential for applications in organic thermoelectrics (OTE) since the radicals are liable to regulate the molecular electronic structure and carrier transfer ability. Whereas, only a few fused quinoid polymers are explored with low power factor (PF) currently. Herein, a liquid-crystal molecule-assisted strategy is proposed to promote a PF breakthrough of quinoid polymers. By introducing liquid-crystal molecule 5CB into the simple non-fused quinoidal polymer PAQM-3T which exhibits stable high-spin characters, a tighter molecular assembly can be readily induced without any residue upon thermal annealing, leading to nearly doubled carrier mobility and conductivity. Moreover, 5CB-treatment causes few impacts on the high-spin character and the Seebeck coefficient (S) can keep a high value under heavy p-type doping conditions. Ultimately, the optimal PF of PAQM-3T reaches 198.4 mu W center dot m-1 center dot K-2, higher than those of the traditional simple non-fused aromatic polymers. Notably, 10% wt 5CB-treated film boosts the PF up to 309.55 mu W center dot m-1 center dot K-2 with enhanced conductivity of 145.27 S center dot cm-1 and well-balanced S of 146.6 mu V center dot K-1, which is the highest value among quinoid materials and even approaching to those of the state-of-the-art aromatic polymers. The breakthrough efficiency highlights the promising prospect of liquid-crystal molecular-assisted simple quinoid polymers for high-performance OTE.

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