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Crystals 2017, 7(10), 292;

Solvent-Dependent Thermoelectric Properties of PTB7 and Effect of 1,8-Diiodooctane Additive

Department of Electrical and Computer Engineering, Inter-University Semiconductor Research Center, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Korea
Materials Science Consulting and Management, 22113 Oststeinbek, Moellner Landst. 97B, Germany
Authors to whom correspondence should be addressed.
Academic Editor: George S. Nolas
Received: 19 August 2017 / Revised: 17 September 2017 / Accepted: 26 September 2017 / Published: 29 September 2017
(This article belongs to the Special Issue Materials Processing and Crystal Growth for Thermoelectrics)
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Conjugated polymers are considered for application in thermoelectric energy conversion due to their low thermal conductivity, low weight, non-toxicity, and ease of fabrication, which promises low manufacturing costs. Here, an investigation of the thermoelectric properties of poly({4,8-bis[(2-ethylhexyl)oxy]benzo [1,2-b:4,5-b′] dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl) carbonyl]thieno[3,4-b] thiophenediyl}), commonly known as PTB7 conjugated polymer, is reported. Samples were prepared from solutions of PTB7 in three different solvents: chlorobenzene, 1,2-dichlorobenzene, and 1,2,4-trichlorobenzene, with and without 1,8-diiodooctane (DIO) additive. In order to characterize their thermoelectric properties, the electrical conductivity and the Seebeck coefficient were measured. We found that, by increasing the boiling point of the solvent, both the electrical conductivity and the Seebeck coefficient of the PTB7 samples were simultaneously improved. We believe that the increase in mobility is responsible for solvent-dependent thermoelectric properties of the PTB7 samples. However, the addition of DIO changes the observed trend. Only the sample prepared from 1,2,4-trichlorobenzene showed a higher electrical conductivity and Seebeck coefficient and, as a consequence, improved power factor in comparison to the samples prepared from chlorobenzene and 1,2-dichlorobenzene. View Full-Text
Keywords: electrical conductivity; Seebeck coefficient; power factor; PTB7 polymer electrical conductivity; Seebeck coefficient; power factor; PTB7 polymer

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Rastegaralam, M.; Lee, C.; Dettlaff-Weglikowska, U. Solvent-Dependent Thermoelectric Properties of PTB7 and Effect of 1,8-Diiodooctane Additive. Crystals 2017, 7, 292.

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