Interfacial Energy Barrier Tuning for Enhanced Thermoelectric Performance of PEDOT Nanowire/SWNT/PEDOT:PSS Ternary Composites

Abstract

Ternary composites based on single-walled carbon nanotube (SWNT), poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), and PEDOT nanowire (NW) were prepared by solution mixing methods. Studies show that Seebeck coefficient of the composites with SWNT and PEDOT:PSS could be further enhanced by addition of PEDOT NW to form ternary hybrids, which is attributable to interfacial carrier energy filtering effect which selectively filters the low-energy carriers and overpasses the high-energy carriers at NW/PEDOT:PSS interfaces. The addition of SWNT into the system leads to high electrical conductivity of the resulting ternary composites. The combination of high Seebeck coefficient and high conductivity results in the ternary composite with high power factor (PF), and an optimized PF of ∼352 μW m-1 K-2 at room temperature is obtained. The mechanism behind the enhancement of the Seebeck coefficient is also elucidated by studying the carrier transport phenomena through PEDOT NW/PEDOT:PSS interfaces via tuning of the interfacial energy barriers that resulted from different doping levels of PEDOT NWs. Thermoelectric generators assembled by five optimized composite films exhibit a maximum output power of 414 nW when ΔT = 40 K, which demonstrates the potential capability for practical thermal energy harvesting.