Fully Organic Nanocomposites with High Thermoelectric Power Factors by using a Dual-Stabilizer Preparation

The thermoelectric properties of fully organic nanocomposites were investigated, for which meso-tetra(4-carboxyphenyl) porphine (TCPP) and poly(3,4-ethylenedioxythiophene):poly( styrene sulfonate) (PEDOT: PSS) were used as instrinically conductive and semiconducting stabilizers, respectively. The electrical conductivity (sigma) of these dual-stabilizer organic composites increased to approximately 9500 Sm-1 as the concentrations of both the multiwalled carbon nanotubes (MWNTs) and PEDOT: PSS were increased. The thermopower (or Seebeck coefficient, S) and thermal conductivity, however, remained relatively unaffected by the increase in concentration (approximate to 40 mu VK-1 and approximate to 0.12 Wm(-1)K(-1), respectively). Replacing MWNTs with double-walled carbon nanotubes (DWNTs) increased sigma and S to approximately 96 000 Sm-1 and 70 mu VK-1, respectively, at 40 wt% DWNTs. This study suggests that s and S can be simultaneously tailored by using multiple stabilizing agents to affect the transport properties of the junctions between nanotubes. Combining semiconducting and intrinsically conductive molecules as CNT-stabilizers has led to a power factor that is among the best for a completely organic, free-standing film (approximate to 500 mu Wm(-1)K(-2)). These flexible, segregated-network nanocomposites now exhibit properties that rival the more conventional inorganic semiconductors, particularly when normalized by the mass.