The requirement of a portable electron is functioning as a driving force for a wearable energy instrument. Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), as one of the most promising organic electron materials, has been widely studied in energy conversion devices. However, the efforts for PEDOT:PSS fibers are insufficient to boost the development of wearable thermoelectric energy harvesting. Here, a highly conductive p-type PEDOT:PSS fiber was produced by gelation process, which was 3 orders of magnitude higher than that of previous hydrogel fibers. Surprisingly, a posttreatment with organic solvents such as ethylene glycol and dimethyl sulfoxide tripled their electrical conductivity with an only 5% decreased Seebeck coefficient, consequently leading to an optimized thermoelectric power factor. Furthermore, we assembled a p−n-type thermoelectric device connecting five pairs of p-type PEDOT:PSS fibers and n-type carbon nanotube fibers. This fiber-based device displayed an acceptable output voltage of 20.7 mV and a power density of 481.2 μW•cm −2 with a temperature difference of ∼60 K, which might pave the way for the development of organic thermoelectric fibers for wearable energy harvesting.
Carbon nanotubes (CNTs) have attracted much attention in developing high-performance, low-cost, flexible thermoelectric (TE) materials because of their great electrical and mechanical properties. Theory predicts that one-dimensional semiconductors have natural advantages in TE fields. During the past few decades, remarkable progress has been achieved in both theory and experiments. What is more important is that CNTs have shown desirable features for either n-type or p-type TE properties through specific strategies. Up to now, CNT‒polymer hybrids have held the record for TE performance in organic materials, which means they can potentially be used in high-performance TE applications and flexible electronic devices. In this review, we intend to focus on the intrinsic TE properties of both n-type and p-type CNTs and effective TE enhanced strategies. Furthermore, the current trends for developing CNT-based and CNT‒polymer-based high TE performance organic materials are discussed, followed by an overview of the relevant electronic structure‒TE property relationship. Finally, models for evaluating the TE properties are provided and a few representative samples of CNT‒polymer composites with high TE performance are highlighted.
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