We present a new approach to fabricate n-type organic thermoelectric nanocomposites through a layer-by-layer (LbL) method. An alternate deposition of double walled carbon nanotube (DWNT)-dispersed in polyethyleneimine (PEI) and graphene-dispersed in polyvinylpyrrolidone (PVP) solutions generated a highly layered nanocomposite in which DWNT with diameter in the range of 15-20 nm and graphenes (1.5 µm in diameter) formed an interconnected network between upper and lower layers. This unique combination exhibits that the electrical conductivity and Seebeck coefficient of 80 DWNT-PEI/graphene-PVP bilayer films (~ 320 nm in thickness) are very high (300 S/cm and -80 µV/K, respectively). In this first ever investigation of the n-type TE behavior of an LbL-assembled film, the resulting nanocomposites exhibit a remarkable PF of 190 W/mK<sup>2</sup> at room temperature, which is one of the highest values reported among organic n-type TE materials. A continuous 3-dimensional conjugated network, where DWNT bridges gaps between graphene sheets, provides more efficient electron transport and increases Seebeck coefficient due to improved carrier mobility. Furthermore, the graphene platelets aligned in the multilayers in the direction parallel to the substrate act as a barrier to permeating oxygen, imparting high stability in air over time. This novel n-type nanocomposite has the potential to open the way to low-cost and efficient thermoelectric materials, as well as to demonstrate the possibility of designing high performance p/n thermoelectric devices.

Stable n-type thermoelectric multilayer thin films with high power factor from carbonaceous nanofillers

253rd National Meeting (2017)

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