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A1: Low temperature materials

Highly Stable Hybrid Selenophene-3,4-Ethylenedioxythiophene as Electrically Conducting and Thermoelectric Polymers

Baoyang Lu1,2, Shijie Zhen1, Jingkun Xu1,2,*, Guoqun Zhao2,*
1Jiangxi Key Lab of Organic Chemistry, Jiangxi Science and Technology Normal University 2Key Lab for Liquid-Solid Structural Evolution and Processing of Materials, Shandong University

    We have witnessed fascinating breakthroughs in organic thermoelectric materials/composites during the last several years, some of which are even reaching the marketplace. Most recently, our group investigated the thermoelectric performances of different types of polyselenophene (PSE) prepared by different methods/conditions and found that PSE exhibits very high Seebeck coefficient (>180 V K-1) despite its relatively low electrical conductivity (10-5 to 10-2 S cm-1). Based on our previous results, we herein synthesized a family of four novel selenophene-EDOT monomers were using Stille coupling and electropolymerized to form highly stable conducting hybrid polymers. Structure-property relationships of the monomers and hybrid polymers, including electrochemical, electronic and optical properties, quantum chemistry calculations and morphology, etc., were systemetically explored. The monomer precursors with planar structures exhibit blue to orange emission characteristics with quantum yields ranging from 0.6 to 9.0%, which may be used as building blocks for the rational design of fluorescent conjugated systems with enhanced main chain planarity. Cyclic voltammetry shows low oxidation potentials ranging from 0.53 to 0.89 V vs. Ag/AgCl, leading to the facile electrodepostion of uniform hybrid polymer films with outstanding electroactivity and stability at low oxidation potentials. The obtained hybrid polymers featured the advantageous combination of polyselenophene and PEDOT, such as lower band gap and better planarity of polyselenophene, high conductivity, transparency and excellent stability of PEDOT. The hybrid polymers show planar π-conjugated backbones with band gaps ranging from 1.55 to 1.75 eV. Also, the thermoelectric performances of electrosynthesized hybrid polymers were investigated systematically. Compared with polyselenophenes, their electrical conductivity was determined to be in the range of 10-1~101 S cm-1 by applying a conventional four-probe technique, intermediate between electrodeposited polyselenophene (10-4~10-2 S cm-1) and PEDOT (100~102 S cm-1). Post-processing by using strong poalr solvents could improve their conductivity. The detailed information, together with their thermoelectric performances, are reported in detail.