Observation of anomalously large Nernst effects in conducting polymers

As a fundamental thermoelectric phenomenon in many solid-state materials, the Nernst effect has yet to be observed in conducting polymers. This knowledge could provide important insight into their elusive mechanism, which are crucial for flexible optoelectronic and thermoelectric applications. However, within the Landau's Fermi-liquid picture, the Nernst coefficient has demonstrated to be proportional to the charge mobility, and thus should be negligible in less ordered polymers with inherent low mobility. Here, we challenge this notion by observing an anomalously large Nernst effect in a range of conducting polymers. Specially, the Nernst coefficients in these doped polymers exceed the Fermi-liquid predictions by 2-3 orders of magnitudes with negative mobility dependence. These intriguing observations are attributed to the intrinsic quasi-one-dimensional transport nature in conjugated polymers and their unique chemical doping mechanism. Our research not only provides experimental insights into the non-Fermi-liquid charge transport nature of polymers, but also suggests its universality for other quasi-one-dimensional materials and/or less ordered systems, and opens up exciting possibilities for developing transverse organic thermoelectric applications. The Nernst effect of transverse thermoelectric flow is usually small in less ordered systems with low charge mobility. Here, the authors show that conjugated polymers defy this expectation with Nernst effects orders of magnitude larger than predicted.