Ionic Seebeck Effect in Conducting Polymers

Abstract

have been reported in inorganic ionic solids [ 15 ] and electrolytes, [ 16,17 ] where ions are the only charge carriers. But to the best of our knowledge, the ionic thermoelectric effect in conducting polymers has not been studied and reported before.Here, we investigate the role of ions in the thermoelectric response of different PEDOT derivatives. We observe surprisingly large increases in the thermo-induced voltage at high humidity levels, of up to several hundreds of µV/K, which is identifi ed as an ionic Seebeck effect. The ionic thermovoltage and its potential for improving the thermoelectric effi ciency in conducting polymers are discussed.Five different PEDOT derivatives of different electrical conductivities (measured at 10% RH, 300 K) are deposited on glass substrates including two gold electrode patterns separated by 1 mm: (i) PEDOT-Tos (thickness = 627 nm, σ = 15 200 S m −1 ) synthesized by using solution oxidative in situ polymerization, [ 18 ] (ii) PEDOT-PSS-DEG (4.75 µm, σ = 530 S m −1 ) obtained by the addition of 2 wt% of the secondary dopant diethylene glycol (DEG) [ 19 ] into the PEDOT-PSS dispersion, (iii) PEDOT-PSS (5.68 µm, σ = 14 S m −1 ) as the commercial water dispersion called Baytron P by H. C. Starck, (iv) PEDOT-PSSPSSNa (3.43 µm, σ = 0.08 S m −1 ) obtained by the addition of 2 wt% of PSSNa to the PEDOT-PSS dispersion, and (v) selfdoped PEDOT-S (116 nm, σ = 75 S m −1 ), in which the sulfonate dopant groups are covalently linked to the PEDOT chains. PEDOT-S has been synthesized in the lab. [ 20 ] PEDOT-Tos exhibits the highest electrical conductivity. PEDOT-Tos possesses a high density of conducting PEDOT chains (EDOT/sulfonate molar ratio is 2.7) packed in a paracrystalline structure. [ 18 ] In PEDOT-Tos, the tosylate moieties are the anions and balance the positive charges carried along the conducting polymer chains. The included ions are effectively immobile in the polymer; it is an electronic (hole) conductor. In PEDOT-S, the EDOT/sulfonate ratio is 1.

Inkjet-Printed Graphene/PEDOT:PSS Temperature Sensors on a Skin-Conformable Polyurethane Substrate

“…fabricated a humidity sensor using PEDOT:PSS, and they expressed that the change in impedance is based on the dissociation of OH groups in PSS chain and the formation of free charge carriers in PEDOT chain43. In fact, it was recently shown that PEDOT:PSS films act as a mixed ionic-electronic conductor and exhibit a variation in its charge transport property as the humidity level is altered4445. Furthermore, Nardes et al .…”

Flexible and Cellulose-based Organic Electronics

“…Conductive polymers are ionically conductive which means ions can easily move in and out of the electrode. [96][97][98] Carbon and metal oxides lack ionic conductivity and instead rely on porous structures and how well the electrolyte can penetrate these pores. Porous structures can be fabricated by pressing particles together or by nanostructuring, such as nanopillars.…”

Measurement of in-plane thermal conductivity in polymer films

“…This material is commercially available and has attracted considerable recent attention within the realm of thermoelectric applications. [15][16][17][18][19][20][21] There are two principal justifications for the choice of PEDOT/PSS in support of this study: (1) the in-plane electrical conductivity of free-standing PEDOT/PSS film remains essentially constant even in cases where the thickness varies from several micrometers to ∼100 µm (thus, suggesting that the morphology of the film is relatively stable); 22 and (2) the in-plane thermal conductivity can be independently confirmed by using flash analysis methods 14 or time-domain thermoreflectance methods, 12 with both methods ultimately generating comparable values.…”