Electrochemical Treatment for Effectively Tuning Thermoelectric Properties of Free‐Standing Poly(3‐methylthiophene) Films

Abstract

The degree of oxidation of conducting polymers has great influence on their thermoelectric properties. Free-standing poly(3-methylthiophene) (P3MeT) films were prepared by electrochemical polymerization in boron trifluoride diethyl etherate, and the fresh films were treated electrochemically with a solution of propylene carbonate/lithium perchlorate as mediator. The conductivity of the resultant P3MeT films depends on the doping level, which is controlled by a constant potential from -0.5 to 1.4 V. The optimum electrical conductivity (78.9 S cm(-1) at 0.5 V) and a significant increase in the Seebeck coefficient (64.3 μV K(-1) at -0.5 V) are important for achieving an optimum power factor at an optimal potential. The power factor of electrochemically treated P3MeT films reached its maximum value of 4.03 μW m(-1) K(-2) at 0.5 V. Moreover, after two months, it still exhibited a value of 3.75 μW m(-1) K(-2) , and thus was more stable than pristine P3MeT due to exchange of doping ions in films under ambient conditions. This electrochemical treatment is a significant alternative method for optimizing the thermoelectric power factor of conducting polymer films.

Recent Advances in Organic Thermoelectric Materials: Principle Mechanisms and Emerging Carbon-Based Green Energy Materials

“…Polymers employed in organic thermoelectric materials are categorized into conducting polymers and non-conducting polymers. The commonly investigated conducting polymers include poly(3,4-ethylenedioxythiophene) [36,37,38,39], polyacetylene [40,41], poly(aniline) [42,43], polythiophenes [44,45], polypyrrole [46,47], polyphenylenevinylene [48], and poly(3-methylthiophene) [49,50], while the non-conducting polymers include poly(3-octylthiophene) [51], poly(3-hexylthiophene) (P3HT) [52], and polyvinylidene fluoride [53,54,55]. Their chemical structures are presented in Table 1.…”

Flexible Organic Thermoelectric Materials and Devices for Wearable Green Energy Harvesting

“…Non-conducting polymers and conducting polymers are both used to prepare organic thermoelectric devices, but conducting polymers play the dominant role. Poly(3-hexylthiophene) (P3HT) [60], poly(3-octylthiophene) [61], and polyvinylidene fluoride [62,63] are three commonly used non-conducting polymers, while conducting polymers include poly(3-methylthiophene) [64,65], polyacetylene [66,67], poly(aniline) [68,69], polypyrrole [34,70], polythiophenes [58,71], polyphenylenevinylene [72], and poly(3,4-ethylenedioxythiophene) [73,74,75,76], and their chemical structures are shown in Table 1.…”

Investigation of organic thermoelectric materials using potential‐step chronocoulometry: Effect of polymerization methods on thermoelectric properties of poly(3‐hexylthiophene)

“…[10] Xu and Jiang successfully tuned thermoelectric properties of poly(3-methylthiophene) by using the electrochemical treatment, but still could not evaluate the charge density. [11] We have accurately quantified the doping level of conducting polymers, which is similar to the charge density, using potential-step chronocoulometry (PSC), and controlled the doping levels of conducting polymers by the applied potential. And using this technique, we succeeded in establishing in-situ measurement of electrical conductivity at each doping level.…”

“…[ 10 ] Xu and Jiang successfully tuned thermoelectric properties of poly(3‐methylthiophene) by using the electrochemical treatment, but still could not evaluate the charge density. [ 11 ]…”