[13a-A405-1~11] 12.2 Characterization and Materials Physics

[13a-A405-3] The origin of thermopower in semicrystalline, pi-conjugated polymers

〇Shunichiro Watanabe^1,2,3, Masahiro Ohno¹, Yu Yamashita^1,4, Tsubasa Terashige^1,2, Hiroshi Okamoto^1,2, Jun Takeya^1,2,4 (1.Univ. of Tokyo, 2.OPERANDO-OIL, 3.PRESTO JST, 4.NIMS)

Keywords:Conductive polymers, Charge and thermoelectric transport

Charge and thermoelectric transport should be correlated closely with each other; however, little is known regarding the origin of thermopower in semicrystalline pi-conjugated polymers, particularly those doped with molecular dopants. It is controversial whether the well-established Mott formula is valid for such conducting polymers, which inevitably have a finite structural disorder. We show that a truly metallic regime that can be realized in a highly crystalline domain gives rise to thermopower, which is demonstrated unambiguously by the observation of a linear temperature dependence of the Seebeck coefficient in semicrystalline polythiophene-based conducting polymers. The presence of onset metallicity is also verified comprehensively by the Hall effect and Drude optical response, which indicates that the Mott formula, which is frequently used for degenerated semiconductors and metals, can be applicable to highly crystalline conjugated polymers. This provides insight into the structure-thermoelectric property relationships in semicrystalline conducting polymers.