LAUSR

Without sacrificing the intrinsic softness and flexibility of conducting polymers, their blends have been demonstrated to be promising to improve thermoelectric properties of conducting polymers. However, the underlying mechanism for the thermoelectric enhancement is hitherto far from clear and is worthy of being explored deeply. In this work, we report novel conducting polymer nanowires blends by physically mixing poly(3,4-ethylenedioxythiophene) (PEDOT) nanowires and polypyrrole (PPy) nanowires. By carefully tuning the energetic structure of PPy nanowires (nanofillers), the Seebeck coefficients and power factors of nanowire blends are surprisingly increased by ~20% and ~32% (compared to PEDOT nanowires), respectively. By means of first-principle calculations and experimental characterizations, we qualitatively confirm that the improved thermoelectric property is a consequence of built-in energy barrier at nanowire interfaces rather than the commonly-used doping/de-doping effect. Subsequently, we further employ the Kang-Snyder transport model and quantitively demonstrate that the energy barrier involves energy-dependent carrier scattering (thus a change of total relaxation time) at nanowire heterojunctions, which contributes to the enhanced the Seebeck coefficients and thus power factors. Our work sheds light on the mechanism that can be adopted to design soft but high-performance thermoelectric materials with conducting polymer blends.