Enhancement of p-type thermoelectric power factor by low-temperature calcination in carbon nanotube thermoelectric films containing cyclodextrin polymer and Pd

The p-type properties of carbon nanotubes (CNTs) in organic thermoelectric devices need urgent improvement for large-scale, low-grade thermal energy applications. Here, we present a suitable approach to significantly enhance the power factor (PF) by increasing the electrical conductivity through the low-temperature calcination-induced pyrolysis of the insulating gamma-cyclodextrin polymer (P gamma CyD), which is used as a solubilizer of film-like CNTs. The low-temperature calcination method, which can be used to realize good electrical contact between CNT bundles, shows enhancement behavior as a universal phenomenon for not only P gamma CyD but also other commonly used polymers for CNT films. To moderate the calcination temperature, the Pd catalyst was added, and the optimal temperature was reduced from 340 degrees C to 250 degrees C. Consequently, the PF value of the CNT film was 570 mu Wm(-1)K(-2), which was found to be more than twice that of the original CNT film. In addition, we demonstrated the energy harvesting capability of a thermoelectric generator based on this p-type CNT film; a thermoelectric generator with 10 p-type thermoelectric elements showed a maximum power output of 10.3 mu W with a temperature difference of 75 degrees C, which is comparable to the maximum power output of some of the best single-component organic thermoelectric devices demonstrated to date. This outstanding output power shows that easy-to-handle CNT films with low-temperature heat treatment can open new avenues for the development of thermoelectric generators. (C) 2021 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

Automated summary

In this study, the electrical conductivity of carbon nanotube films was significantly enhanced by low-temperature calcination-induced pyrolysis, leading to a substantial improvement in the power factor. Additionally, the addition of a Pd catalyst reduced the optimal calcination temperature, further enhancing the performance of the carbon nanotube film.