A facile chemical reduction approach for effectively tuning thermoelectric properties of PEDOT films

Abstract

Poly(3,4-ethylenedioxythiophene)–tosylate–polyethylene glycol–polypropylene glycol–polyethylene glycol (PEDOT–Tos–PPP) films were prepared via a vapor phase polymerization (VPP) method. The films possess good electrical conductivity (1550Scm−1), low Seebeck coefficient (14.9μVK−1) and thermal conductivity (0.501Wm−1K−1), and ZT∼0.02 at room temperature (RT, 295K). Then, the films were treated with NaBH4/DMSO solutions of different NaBH4 concentrations to adjust the redox level. After the NaBH4/DMSO treatment (dedoping), the electrical conductivity of the films continuously decreased from 1550 to 5.7Scm−1, whereas the Seebeck coefficient steeply increased from 14.9 to 143.5μVK−1. A maximum power factor of 98.1μWm−1K−2 has been achieved at an optimum redox level. In addition, the thermal conductivity of the PEDOT–Tos–PPP films decrease from 0.501 to 0.451Wm−1K−1 after treated with 0.04% NaBH4/DMSO solution. A maximum ZT value of 0.064 has been achieved at RT. The electrical conductivity and thermal conductivity (Seebeck coefficient) of the untreated and 0.04% NaBH4/DMSO treated PEDOT–Tos–PPP films decrease (increases) with increasing temperature from 295 to 385K. And the power factor of the films monotonically increases with temperature. The ZT at 385K of the 0.04% NaBH4/DMSO treated film is 0.155.