Seebeck effect of conducting polymers and development of efficient organic thermoelectric devices

2019 Fiscal Year Final Research Report

• Project/Area Number: 17K05965
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Energy-related chemistry
• Research Institution: Hiroshima University
• Principal Investigator: Harima Yutaka 広島大学, 工学研究科, 名誉教授 (20156524)
• Co-Investigator(Kenkyū-buntansha): 今榮 一郎 広島大学, 工学研究科, 准教授 (90293399)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 熱電変換 / ゼーベック効果 / 導電性高分子 / 有機材料 / ドープ率 / 位置規則性 / EDOT:PSS

Outline of Final Research Achievements

Relationship between the Seebeck coefficient (S) and charge density (doping level) in conductive polymers was studied in order to create highly efficient organic thermoelectric materials. In regioregular poly(3-hexylthiophene) (P3HT) films, the relationship between log S and the doping level gave a straight line with a slope of -1 over a wide range of doping level. This was the first reliable result of the correlation between the charge density and S among those observed for inorganic and organic thermoelectric materials so far. The finding had a strong impact on researchers in the field of thermoelectricity. We extended the target to regiorandom P3HT synthesized by polycondensation and electro-oxidation polymerization, and the doping level dependence of S was studied. We extended further our research focus to PEDOT:PSS, which is a promising organic thermoelectric conversion material, and investigated the search for efficient organic thermoelectric materials.

Free Research Field

応用物理化学

Academic Significance and Societal Importance of the Research Achievements

化石燃料に代わる再生可能エネルギーへの関心は強さを増している。太陽光発電や風力発電と並んで排熱の利用技術，特に低温領域での熱電材料の開発が喫緊の課題となっている。本研究課題では有機材料の中でも特に優れた特徴を有する導電性高分子を対象に，熱電変換特性に重要な影響を与えるゼーベック係数（S）に着目した。ドープ率の評価に電気化学的手法を用いることにより，位置規則性を有するP3HT膜ではlog Sとドープ率の間に直線関係が成り立ち，その傾きは－１であることを見出した。金属等に対して理論的に予測される-2/3とわずかに異なる勾配のを解明することは学術的に意義深く，高効率有機熱電変換素子の開発にも資する。