N-Type Organic Thermoelectrics: Improved Power Factor by Tailoring Host-Dopant Miscibility

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Abstract

In this contribution, for the first time, the polarity of fullerene derivatives is tailored to enhance the miscibility between the host and dopant molecules. A fullerene derivative with a hydrophilic triethylene glycol type side chain (PTEG-1) is used as the host and (4-(1,3-dimethyl-2,3-dihydro-1H-benzoimidazol-2-yl)phenyl)dimethylamine n-DMBI) as the dopant. Thereby, the doping efficiency can be greatly improved to around 18% (<1% for a nonpolar reference sample) with optimized electrical conductivity of 2.05 S cm(-1) , which represents the best result for solution-processed fullerene derivatives. An in-depth microstructural study indicates that the PTEG-1 molecules readily form layered structures parallel to the substrate after solution processing. The fullerene cage plane is alternated by the triethylene glycol side chain plane; the n-DMBI dopants are mainly incorporated in the side chain plane without disturbing the π-π packing of PTEG-1. This new microstructure, which is rarely observed for codeposited thin films from solution, formed by PTEG-1 and n-DMBI molecules explains the increased miscibility of the host/dopant system at a nanoscale level and the high electrical conductivity. Finally, a power factor of 16.7 µW m(-1) K(-2) is achieved at 40% dopant concentration. This work introduces a new strategy for improving the conductivity of solution-processed n-type organic thermoelectrics.

Original languageEnglish
Article number1701641
JournalAdvanced materials
Volume29
Issue number36
Early online date19-Jul-2017
DOIs
Publication statusPublished - 27-Sep-2017

Keywords

  • FULLERENES
  • SOLUBILITY
  • CONDUCTING POLYMERS
  • CHARGE-TRANSPORT
  • SOLAR-CELLS
  • THIN-FILMS
  • SEMICONDUCTORS
  • DESIGN
  • DERIVATIVES
  • TRANSISTORS

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