Recent advances in preparation, thermoelectric properties, and applications of organic small molecule/SWCNT composites

Thermoelectric (TE) materials allow for direct conversion between heat and electricity, realizing a facile and effective utilization of waste heat and thermal management. Semiconductive organic small molecules (OSMs) have attracted ever increasing attention in TE devices fabrication due to its simplicity in synthesis, well-defined molecular structure, low toxicity, and low thermal conductivity (κ). As a unique 1D carbon allotrope, single-walled carbon nanotubes (SWCNTs) have excellent structural and electrical properties. Thermoelectric OSM/SWCNT composites with both high conductivity and low thermal conductivity have drawn great attentions among researchers and achieved remarkable progress. However, current research fails to give a clear relationship between the structure of small molecules and their thermoelectric performance, and the microscopic mechanisms governing the formation of OSM/SWCNT composites are not well understood as well. These in all need further investigation to guide future development in preparing high-performance OSM/SWCNT thermoelectric composites. In this review, we introduce recent advancement in thermoelectric OSM/SWCNT composites, providing a detailed overview of optimization strategies for small molecule dopants. Also summarized in this review article is the design of organic small molecules from various aspects, including energy level regulation, side chain modification, selection of substituents, etc. Different preparation methods and applications of OSM/SWCNT composites are introduced in detail. Finally, outlooks on the future development of OSM/SWCNT composite thermoelectric materials are pointed out.