Barrier Energy Engineering Enables Efficient Carrier Transport of Single-Walled Carbon Nanotube–Small Organic Molecules Hybrid Thermoelectrics

Abstract

Understanding the inherent charge carrier transport mechanism within carbon nanotube−organic hybrid thermoelectric (TE) materials is crucial for enhancing their TE performance. Although various carbon nanotube−organic hybrid TE materials have been developed, the influence of the barrier energy on the TE transport mechanism within these hybrids remains elusive. Our study focuses on the engineering of barrier energy between single-walled carbon nanotubes (SWCNTs) and small organic molecules (SOMs) by modulating the mesomeric effects of terminal functional groups on T-shaped SOMs. The minimization of barrier energy in an SWCNTs−BTBIN hybrid to 0.04 eV resulted in a semiconducting-dominant transport character, facilitating the energy filtering of SWCNTs−BTBIN. Consequently, SWCNTs−BTBIN achieved a higher Seebeck coefficient (65 μV K −1 ) than other hybrids (39−54 μV K −1 ) having steeper barrier energies (0.30 and 0.19 eV), enabling the highest power factor (798 μW m −1 K −2 ) and ZT value up to 0.035 at room temperature among SWCNTs−BTBI hybrid series. A TE module consisting of SWCNTs−BTBIN incorporating five-leg TE elements produced an output power exceeding 0.82 μW, suggesting that integrating barrier energy engineering with analyses of TE transport mechanisms can significantly advance the design of high-performance nanocarbon-based organic hybrid TEs.