Molecular Doping of a Naphthalene Diimide-Bithiophene Copolymer and SWCNTs for n-Type Thermoelectric Composites

Ye Liu; Diego Rosas Villalva; Anirudh Sharma; Md Azimul Haque; Derya Baran

doi:10.1021/acsami.0c16740

Molecular Doping of a Naphthalene Diimide-Bithiophene Copolymer and SWCNTs for n-Type Thermoelectric Composites

ACS Appl Mater Interfaces. 2021 Jan 13;13(1):411-418. doi: 10.1021/acsami.0c16740. Epub 2020 Dec 29.

Authors

Ye Liu¹, Diego Rosas Villalva¹, Anirudh Sharma¹, Md Azimul Haque¹, Derya Baran¹

Affiliation

¹ Physical Science and Engineering Division, KAUST Solar Center (KSC), King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia.

PMID: 33373201
DOI: 10.1021/acsami.0c16740

Abstract

Molecular doping is a powerful tool to tune the thermoelectric (TE) properties of solution-processed semiconductors. In this work, we prepared a binary composite and effectively doped both of its constituents, that is, naphthalene diimide-bithiophene copolymers (PNDI2OD-T2) and single-walled carbon nanotubes (SWCNTs), by a 1H-benzimidazole derivative (N-DMBI). The doped composites show an n-type character and an in-plane TE figure of merit (ZT), exceeding the values obtained with the doped polymers. The use of SWCNTs consistently results in a higher σ with a maximum value above 10² S/cm, resulting in the highest power factor of 18.1 μW/mK² for an SWCNT loading of 45.5 wt %. Furthermore, an SWCNT content up to 9 wt % does not compromise the low thermal conductivity of the polymer matrices, leading to a ZT value of 0.0045. The n-type composites show good solution processability and relatively stable Seebeck coefficients upon air exposure for 8 months.

Keywords: D−A copolymer; SWCNTs; flexible thermoelectrics; molecular doping; n-type; solution-processing.