Bringing Conducting Polymers to High Order: Toward Conductivities beyond 105 S cm−1 and Thermoelectric Power Factors of 2 mW m−1 K−2

作者：Vishnu Vijayakumar, Yuhan Zhong, Viktoriia Untilova, Mounib Bahri, Laurent Herrmann, Laure Biniek, Nicolas Leclerc, Martin Brinkmann · 发表于：Advanced Energy Materials · 年份：2019 · DOI：10.1002/aenm.201900266 · 被引用次数：202 · 研究领域：Conducting polymers and applications、Organic Electronics and Photovoltaics、Advanced Thermoelectric Materials and Devices

Abstract Here, an effective design strategy of polymer thermoelectric materials based on structural control in doped polymer semiconductors is presented. The strategy is illustrated for two archetypical polythiophenes, e.g., poly(2,5‐bis(3‐dodecyl‐2‐thienyl)thieno[3,2‐b]thiophene) (C12‐PBTTT) and regioregular poly(3‐hexylthiophene) (P3HT). FeCl3 doping of aligned films results in charge conductivities up to 2 × 105 S cm−1 and metallic‐like thermopowers similar to iodine‐doped polyacetylene. The films are almost optically transparent and show strongly polarized near‐infrared polaronic bands (dichroic ratio >10). The comparative study of structure–property correlations in P3HT and C12‐PBTTT identifies three conditions to obtain conductivities beyond 105 S cm−1: i) achieve high in‐plane orientation of conjugated polymers with high persistence length; ii) ensure uniform chain oxidation of the polymer backbones by regular intercalation of dopant molecules in the polymer structure without disrupting alignment of π‐stacked layers; and iii) maintain a percolating nanomorphology along the chain direction. The highly anisotropic conducting polymer films are ideal model systems to investigate the correlations between thermopower S and charge conductivity σ. A scaling law S ∝ σ−1/4 prevails along the chain direction, but a different S ∝ −ln(σ) relation is observed perpendicular to the chains, suggesting different charge transport mechanisms. The simultaneous increase of charge conductivi...