Preparation and Thermoelectric Properties of Semiconducting Single-Walled Carbon Nanotubes/Regioregular Poly(3-dodecylthiophene) Composite Films.

Mengdi Wang,Qin Yao,Hui Li,Yanling Chen,Sanyin Qu,Lidong Chen

doi:10.3390/polym12112720

Abstract

Single-walled carbon nanotubes (SWNTs) have been widely used as leading additives for improving the thermoelectric properties of organic materials, due to their unique structure and excellent electronic transport properties. However, the as-synthesized SWNTs are mixtures (mix-SWNT) of semiconducting (sc-SWNT) and metallic (met-SWNT) carbon nanotubes. The significantly different surface character and transport behavior of sc-SWNT and met-SWNT frequently raise the difficulty of modifying microstructures, and tuning transport properties of SWNTs/organic composites, when using mix-SWNTs as dispersion phase. Herein, we prepared high quality sc-SWNTs/rr-P3DDT composite film by presorting pure sc-SWNT from the raw mix-SWNTs using regioregular poly(3-dodecylthiophene) (rr-P3DDT). Both the smoothness and compactness of sc-SWNTs/rr-P3DDT are great improved, as compared with the mix-SWNTs/rr-P3DDT films, and the sc-SWNTs are well-dispersed and uniformly wrapped by rr-P3DDT with diameter less than 50 nm. The significantly enhanced Seebeck coefficients and power factors are obtained in the sc-SWNT/rr-P3DDT samples. As the result, the maximum power factor of 60 μW/mK2 in 50 wt% sc-SWNTs sample is 70% higher than that of mix-SWNTs/P3DDT sample. This work reveals the effectiveness of pure semiconductor SWNTs as fillers to optimize the thermoelectric properties of CNT/polymer nano-composites.

Highlights

Organic thermoelectric materials, such as polyaniline [1,2], poly(3-hexylthiophene) (P3HT) [3]and poly(3,4-ethylenedioxythiophene) (PEDOT) [4,5,6], have attracted extensive attention as promising thermoelectric materials due to their low cost, flexibility and inherently low thermal conductivity
The high purity sc-single-walled carbon nanotubes (SWNTs) were successfully sorted from raw mixSWNTs through a simple solution centrifugation process using P3DDT as the dispersant, and the scSWNTs/P3DDT composite films were fabricated by directly casting the mixed solution of sc-SWNTs at which the conductivity starts to increase; u is the value of the critical exponent
The high purity sc-SWNTs were successfully sorted from raw mix-SWNTs through a simple solution centrifugation process using P3DDT as the dispersant, and the sc-SWNTs/P3DDT composite films were fabricated by directly casting the mixed solution of sc-SWNTs and P3DDT on the glass substrate

Summary

Introduction

Organic thermoelectric materials, such as polyaniline [1,2], poly(3-hexylthiophene) (P3HT) [3]and poly(3,4-ethylenedioxythiophene) (PEDOT) [4,5,6], have attracted extensive attention as promising thermoelectric materials due to their low cost, flexibility and inherently low thermal conductivity. The nanocomposite approach has been utilized to tune the thermoelectric properties of conducting polymers based on the expectation of combining unique characters of individual nano-inclusions and/or introducing possible synergistic effects. It has been proven by quite a few studies that filling single-walled carbon nanotubes (SWNTs) into the polymer matrix is an effective way to enhance the thermoelectric power factor. This is generally due to the introduction of one-dimensional structures, with excellent electrical conductivity and hybrid structures, formed on the interfaces between SWNTs and polymer molecules [7,8]. Few studies have been reported on the TE properties of sc-SWNT/polymer composites due to the arduous sorting of sc-SWNTs out of as-grown mix-SWNTs

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Results

Conclusion