Sustainable Framework for Thermoelectric Inorganic-In-Organic Superlattices With High Power Factor and Selective P- or N-Type Doping

Abstract

Contemporary thermoelectric devices are typically made from inorganic chalogenides, which are expensive, inflexible, toxic, brittle, and difficult to recycle. These limitations have hindered their widespread application as energy scavengers in heat engines. By contrast, organic semiconductor polymers such as poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) are inexpensive, nontoxic, flexible, easy to process, and sustainable. However, their thermopower is around three orders of magnitude lower than that of the inorganic tellurides. Here, we report a facile fabrication framework based on producing metal/polymer superlattice structures. These form extended 2-dimensional delocalized systems that exhibit enhanced thermoelectric performance. Within this framework, we report a power factor of 2800 µW m−1 K−2, two orders of magnitude greater than that of pristine PEDOT:PSS and only around 1.5 times lower than that of the telluride materials. This represents a significant improvement. We also report that using Fe and Cr in the superlattice results in changing the semiconductor doping type from P-type to N-type. Structural, spectroscopic, and electrical analysis reveal modifications to the band structure resulting from these doping changes. These observations were corroborated using density functional modeling. The results also show the metal layers introduce solid–solid dedoping effects to the PEDOT:PSS via a carrier transfer mechanism, resulting in significantly improved thermoelectric performance.