Tuning thermoelectric performance with N-annulated perylene-based small molecules and single-walled carbon nanotube nanocomposite films

Abstract

Two N-annulated perylene (NP)-based organic small molecules (OSMs) with end groups of di-p-tolylamine (DTA) and phenyl-di-p-tolylamine (PhDTA), namely DDTANP and DPhDTANP, are incorporated into single-walled carbon nanotubes (SWCNTs) to fabricate nanocomposite thin films for thermoelectric (TE) application. The weight ratios of OSMs to SWCNTs range from 1:1 to 1:4. The inherent planar structures of these novel OSMs facilitate strong π-π interactions and charge transfer with SWCNTs. Specifically, the DDTANP/SWCNT nanocomposite films, due to its lower HOMO, induces pronounced energy filtering and, thus, a high Seebeck coefficient (S). At the optimized weight ratio of 1:3, DDTANP/SWCNT nanocomposite thin film exhibits an electrical conductivity (σ) of 214.7 S cm−1, and S of 59.8 μV K−1. The flat structure of DPhDTANP enhances its adhesion to SWCNTs, thereby improving dispersion and increasing σ. Similarly, the DPhDTANP/SWCNT (1:3) nanocomposite thin film achieves 256.4 S cm−1, and an S of 55.8 μV K−1. The DPhDTANP/SWCNT (1:3) nanocomposite film exhibits higher σ, resulting in a power factor (PF) of 79.8 μW m−1 K−2, surpassing the PF of 76.7 μW m−1 K−2 for the DDTANP/SWCNT (1:3) nanocomposite film. These findings offer valuable insights into molecular design for SWCNTs-based composite TE research and contributed to enhancing TE applications.