High performance n-type thermoelectric material based on naphthalenediimide radical anions

Abstract

Abstract An ideal organic thermoelectric (TE) material should possesses features including low-cost, high performance, easy to process, and non-toxic, but it’s rare to find materials that meets these requirements. Naphthalenediimide (NDI), as a common and cheap industrial pigment, displays strong intermolecular inaction and good n-type semiconductor character. However, due to the strong interaction of π-π and hydrogen bond interaction, NDI usually exhibited poor solubility, making it difficult to process in solution. Herein, we demonstrated that the unsubstituted NDI could form a suspension mixed with NDI radical anion state by phenyl lithium doping, which consequently can be used to prepare dense film by drop casting for TE application. More importantly, by optimizing doping ratio, the TE film reached electrical conductivity of 0.11 S cm-1 and Seebeck coefficient of -1289 μV K-1. Eventually, high power factor up to 18.8 μW m−1 K−2 and ZT value of 0.053 was obtained, which is one of the best TE performance achieved in n-type NDI-based TE materials. This work suggests the simple strategy of utilizing commercially mature molecules to develop the organic TE materials with high performance.