Molecular and Supramolecular Parameters Dictating the Thermoelectric Performance of Conducting Polymers: A Case Study Using Poly(3-alkylthiophene)s

Abstract

In this study, we investigated the impact of molecular and supramolecular structure of conducting polymers (CPs) on their thermoelectric properties. As a model system, poly­(3-alkylthiophene)­s (P3ATs) with different side-chain lengths were prepared through oxidative chemical polymerization and were recrystallized to a well-ordered lamellar structure, resulting in one-dimensional self-assembled nanofibers (evidenced by transmission electron microscopy, X-ray diffraction, and UV–vis spectroscopic measurements). Thermoelectric characterization was performed at different doping levels (precisely tuned by doping in the redox reaction with Ag+ and Fe3+ cations), and the highly doped samples exhibited the best performance for all studied polymers. By varying the length of the alkyl side chain, the supramolecular structure and consequently the electronic properties were varied. The highest electrical conductivity was measured for poly­(3-butylthiophene), rooted in its densely packed structure. The established structure–property relationships, concerning the monotonous decrease of the electrical conductivity with the alkyl side chain length, highlight the importance of the supramolecular structure (interchain distance in this case). These findings may contribute to the rational design of organic thermoelectric materials.

Challenges and rewards of the electrosynthesis of macroscopic aligned carbon nanotube array/conducting polymer hybrid assemblies

“…On the MWCNTA spectrum, the characteristic D and G bands are located at ν D = 1333 cm −1 and ν G = 1577 cm −1 , respectively, which is in good correspondence with literature data . The bending vibration mode of CH 3 at 1380 cm −1 , together with the symmetric CC stretch (the most intense peak) at 1447 cm −1 are characteristic for the reduced form of P3HT . At this point we note that similar assignment was performed for the MWCNTA/PANI hybrid as well (Supporting Information Fig.…”

“…Voltage and temperature differences were recorded by a computer driven FES24 data acquisition device . Seebeck coefficient was determined from the slope of the voltage difference vs. temperature difference plot.…”

Conductive, Solution‐Processed Dioxythiophene Copolymers for Thermoelectric and Transparent Electrode Applications

“…Specifically, two roll-to-roll compatible methods, spray coating and blade coating, were compared along with spin coating. [40,41] Ferric triflate (Fe(OTf) 3 ), ferric perchlorate (Fe(ClO 4 ) 3 ), and ferric tosylate (Fe(Tos) 3 ) yielded increased conductivity values of 49 ± 4, 76 ± 17, and 91 ± 14 S cm −1 , respectively. Spin-coated films yield higher conductivity values of 3.8 ± 0.8 S cm −1 , while blade-coated films yield the highest values of 4.7 ± 0.7 S cm −1 .…”

“…Iron(III) and Ag(I) based dopants were then investigated due to their relatively low cost, commercial availability, and previous use in doping conjugated polymer films to achieve high σ values. [40,41] Ferric triflate (Fe(OTf) 3 ), ferric perchlorate (Fe(ClO 4 ) 3 ), and ferric tosylate (Fe(Tos) 3 ) yielded increased conductivity values of 49 ± 4, 76 ± 17, and 91 ± 14 S cm −1 , respectively. Similar to the iron dopants, silver(I) bis(trifluoromethylsulfonyl)imide (AgBTI) and silver(I) triflate (AgOTf) demonstrated high σ values of 30 ± 9 and 98 ± 13 S cm −1 , respectively, while PE 2 films doped with silver(I) hexafluorophosphate (AgPF 6 ) yielded higher conductivities of 255 ± 48 S cm −1 .…”

Electrochemical synthesis and characterization of poly(3-hexylthiophene)/single-walled carbon nanotube array hybrid materials

“…The C-C stretching vibration mode at 1377 cm −1 , together with the symmetric C=C stretching (the most intense peak) at 1447 cm −1 are both characteristic for the reduced form of P3HT [37][38][39].…”