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Investigation of the thermoelectric power factor of KOH-treated PEDOT:PSS dispersions for printing applications

: Stepien, Lukas; Roch, Aljoscha; Schlaier, Sarah; Dani, Ines; Kiriy, Anton; Simon, Frank; Lukowicz, Marian v.; Leyens, Christoph


Energy harvesting and systems 3 (2016), Nr.1, S.101-111
ISSN: 2329-8774
ISSN: 2329-8766
European Commission EC
FP7; 604647
Fraunhofer IWS ()
flexible; intrinsically conducting polymer; PEDOT-PSS; power factor; printing; de-doping; thermoelectric generator; pH value

This work studies the modification of commercially available dispersions of intrinsically conductive polymer PEDOT:PSS with a strong base, KOH. It is concluded that addition of base derives a dedoping of the PEDOT chain and increase Seebeck coefficient from 15 µV/K to 90 µV/K. Supportive UV-Vis-NIR spectroscopy was used for tracking the doping level of the polymer. A surface morphology study of the dedoped PEDOT:PSS films was monitored by SEM. It was shown that if KOH is used in excess with respect to the acid component of PEDOT:PSS dispersions, it segregates at the surface forming crystallites. They, however could be easily removed by methanol rinsing without destroying the sample integrity. After material modification, a dispenser-printed polymer unileg-TEG with 61 unicouples was fabricated by printing. The TEG in form of 253 mm-long stripe shows a flexible behavior. At 90 K temperature difference a resulting power output of ~ 100 nW could be measured. We suggest that the low power output is due to a high internal generator resistance.