Optimizing the thermoelectric properties of PEDOT:PSS films by combining organic co-solvents with inorganic base

Abstract

A simple optimizing approach that effectively improves the thermoelectric performance of poly (3,4-ethylenedioxylthiophene):poly(styrenesulfonate) (PED-OT:PSS) films is presented in this paper. The optimizing process is performed by over-dropping a mixture of DMSO/NaOH ethanol solution onto the PEDOT:PSS films, achieving the facile combination of co-solvents effect and dedoping effect. Largely varied electrical conductivity from 837.2 to 0.04 S cm -1 and the Seebeck coefficient from 12.6 to 54.8 lV K -1 are observed by changing the ratios between DMSO and NaOH ethanol solution. Due to the precise control of the dedoping level of PEDOT chains, an optimized power factor of 33.04 lW m -1 K -2 is obtained at the ratio of 10:12 in volume, which is four orders of magnitude higher than that of the pristine film and more than twice the value of DMSO-treated one, simultaneously with the corresponding electrical conductivity and Seebeck coefficient being 598.2 S cm -1 and 23.5 lV K -1 , respectively. Based on the measured thermal conductivity of 0.173 W m -1 K -1 , the maximum ZT value is calculated to be 0.057 at room temperature.

Enhanced Electrical Conductivity and Seebeck Coefficient in PEDOT:PSS via a Two-Step Ionic liquid and NaBH4 Treatment for Organic Thermoelectrics

“…This concentration based increment in electrical conductivity is also observed in other PEDOT:PSS ionic liquid composites [22]. The electrical conductivity of pristine PEDOT:PSS at 40 • C was measured as 3.4 S·cm −1 which is in accordance to literature values [10,20]. When EMIM:TFSI was added into PEDOT:PSS solutions at 0.5% and 1%, there were no significant changes to the electrical conductivities of the films.…”

“…Whilst solvent and ionic liquid treatments leave Seebeck coefficient largely unchanged, treatment with base solutions and reducing agents can tune the oxidation state of PEDOT and thus the Seebeck coefficient can be improved [20]. NaOH solution treatment had been used to increase the Seebeck coefficient from 12.6 µV·K −1 to 54 µV·K −1 in pristine PEDOT:PSS, however, the treatment lead to a decrease in electrical conductivity from 837 S·cm −1 to 0.04 S·cm −1 .…”

Significantly Enhanced Thermoelectric Properties of PEDOT:PSS Films through Sequential Post‐Treatments with Common Acids and Bases

“…The impact of the NaOH treatment on PEDOT:PSS films can be more systematically elucidated by the UV–vis‐NIR absorption spectra at the wavelengths above 600 nm. As reported in literature, the PEDOT chains possess three oxidation states, i.e., neutral, polaron, and bipolaron states . Specifically, the PEDOT chains in their neutral, polaron, and bipolaron states show absorption at ≈600, ≈900, and ≈1400 nm, respectively.…”

Effects of additives and post‐treatment on the thermoelectric performance of vapor‐phase polymerized PEDOT films

“…Mixed solutions have been shown to exhibit several unique advantages, because of the formation of hydrogen bonds, variation of the binding energy, and the regulation of dielectric constant. Furthermore, mixed solutions can display a synergetic influence on the performance of materials . Thus, the introduction of mixed solvents during post‐treatment is a promising and useful approach.…”