High-performance n-type thermoelectric composites of acridones with tethered tertiary amines and carbon nanotubes

Abstract

Very recently, amino-substituted perylene diimides (PDINE) and naphthalene diimides (NDINE) have been reported as good n-type thermoelectric (TE) materials; rational design of their derivatives is strongly desired to further enhance their TE performance. In this study, based on the molecular structure of PDINE and NDINE, a series of acridones with different terminal tertiary amine groups (ADTA) at the C2 and/or C7 positions of the acridone ring was designed and synthesised as potential n-type TE materials. Then, single-walled carbon nanotubes (SWCNTs) were combined with the acridones to form flexible SWCNT/ADTA composite films. The composites exhibited excellent n-type TE performance. Furthermore, the terminal tertiary amine and the number of side chains greatly affected the TE properties of the composites. The composite containing an acridone with two terminal diethyl amine groups displayed the highest power factor of 289.4 ± 2.8 μW m⁻¹ K⁻² at 430 K, which is perhaps one of the highest values reported to date for a composite containing n-type small organic molecules and SWCNTs. In addition, the composite with a functionalised piperidine acridone displayed p-type TE behaviour with a high power factor of 211.6 ± 9.9 μW m⁻¹ K⁻² at room temperature. Our results demonstrate that SWCNT/acridone composites with appropriate substituents show promise as TE materials, which opens a new avenue for TE material design.