title: Enhanced thermoelectric performance of PEDOT:PSS flexible bulky papers by treatment with secondary dopants.
abstract: For inorganic thermoelectric materials, Seebeck coefficient and electrical conductivity are interdependent, and hence optimization of thermoelectric performance is challenging. In this work we show that thermoelectric performance of PEDOT:PSS can be enhanced by greatly improving its electrical conductivity in contrast to inorganic thermoelectric materials. Free-standing flexible and smooth PEDOT:PSS bulky papers were prepared using vacuum-assisted filtration. The electrical conductivity was enhanced to 640, 800, 1300, and 1900 S cm(-1) by treating PEDOT:PSS with ethylene glycol, polyethylene glycol, methanol, and formic acid, respectively. The Seebeck coefficient did not show significant variation with the tremendous conductivity enhancement being 21.4 and 20.6 μV K(-1) for ethylene glycol- and formic acid-treated papers, respectively. This is because secondary dopants, which increase electrical conductivity, do not change oxidation level of PEDOT. A maximum power factor of 80.6 μW m(-1) K(-2) was shown for formic acid-treated samples, while it was only 29.3 μW m(-1) K(-2) for ethylene glycol treatment. Coupled with intrinsically low thermal conductivity of PEDOT:PSS, ZT ≈ 0.32 was measured at room temperature using Harman method. We investigated the reasons behind the greatly enhanced thermoelectric performance.
authors.affiliation: Nanoscience and Technology Program, Taiwan International Graduate Program, ‡Research Center for Applied Sciences, and ∥Institute of Atomic and Molecular Sciences, Academia Sinica , Taipei 115, Taiwan.
authors.forename: Desalegn A
authors.initials: DA
authors.lastname: Mengistie
authors.forename: Chang-Hsiao
authors.initials: CH
authors.lastname: Chen
authors.forename: Karunakara M
authors.initials: KM
authors.lastname: Boopathi
authors.forename: Ferry W
authors.initials: FW
authors.lastname: Pranoto
authors.forename: Lain-Jong
authors.initials: LJ
authors.lastname: Li
authors.forename: Chih-Wei
authors.initials: CW
authors.lastname: Chu
keywords: PEDOT:PSS; Seebeck coefficient; conductive polymer; conductivity enhancement; flexible thermoelectrics; power factor