Thermoelectric Performance Improvement of Polymer Nanocomposites by Selective Thermal Degradation

Thermoelectric films composed of poly(diallyldimethylammonium chloride) (PDDA), graphene, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), and double-walled carbon nanotubes (DWNT) were prepared by using layer-by-layer assembly, followed by heating in an inert atmosphere to selectively degrade film constituents to varying degrees. PEDOT:PSS was used to stabilize graphene and DWNT in water for deposition. A 20 quadlayer PDDA/PEDOT:PSS-graphene/PDDA/PEDOT:PSS-DWNT thin film heated to 425 °C for 60 min (∼20 nm thick) exhibits a simultaneous increase in electrical conductivity and Seebeck coefficient, resulting in a power factor of 168 μW m–1 K–2, which is an order of magnitude larger than that of the unheated control. This dramatic improvement in thermoelectric performance is due to degradation of the insulating poly(diallyldimethylammonium chloride):poly(styrenesulfonate) complex within the film, while maintaining the highly ordered conductive network formed during deposition. This study reveals a simple strategy for preparing high performance organic thermoelectric materials by selectively thermally degrading the insulating material required for film deposition.