Facile optimization of thermoelectric properties in PEDOT:PSS thin films through acido-base and redox dedoping using readily available salts

Authors: Saxena, N., Keilhofer, J., Maurya, A. K., Fortunato, G., Overbeck, J., & Müller-Buschbaum, P. ;

ACS Applied Energy Materials; 

https://doi.org/10.1021/acsaem.7b00334

Abstract
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Poly(ethylene dioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) has emerged as a promising candidate for renewable, clean, and reliable energy generation from waste heat due to its thermoelectric properties. This largely stems from its tunable and potentially high electrical conductivity. However, the resulting small Seebeck coefficients diminish the thermoelectric efficiency. We employ dedoping methods making use of acido-base and redox dedoping in order to optimize its properties. In order to tune the charge carrier concentration in PEDOT:PSS thin films, aqueous solutions of readily available inorganic salts, namely, sodium hydrogen carbonate (NaHCO
3), sodium sulfite (Na2SO3), and sodium borohydride (NaBH4), are introduced in different concentrations into PEDOT:PSS solutions before thin film fabrication. This yields optimized thermoelectric properties in terms of power factors up to 100 μW/K2 m. Changes in the electronic structure are characterized using UV–vis spectroscopy and XPS, while changes in the conformation are investigated using Raman spectroscopy. The thermoelectric quantities are compared for the redox dedopants regarding the absolute number of reducing equivalents.