Percolation-dominated conductivity in a conjugated-polymer-carbon-nanotube composite

TLDR: In this article, a pseudoband gap of 1.5 −2.5 eV was found for conjugated polymers, a form of carbon nanotubes, with a pseudometal conductivity of approximately 10 5 S/m.

Abstract: The discovery two decades ago that polyacetylene could be made extremely conductive on doping with iodine or AsF5 ~Ref. 1! was the initial step that indicated that conjugated polymers may be an important alternative to inorganic semiconductors as optoelectronic materials. However, conventional doping of polymers tends to quench their luminescent properties by introducing nonradiative trapping states such as solitons, polarons, and bipolarons. 2 The key feature of conjugated polymers is the extended p-electron system in their backbone, which, due to Peierls distortion, results in a pseudoband gap. In these polymers conduction proceeds by variable range hopping of polarons. The band gap is approximately 1.5‐2.5 eV, hence conductivity and mobility are generally low. Carbon nanotubes, another form of conjugated carbon system, consist of one or more sheets of graphene wrapped around each other in concentric cylinders. Individually, nanotubes may be metallic or semiconducting, but in bulk they form a pseudometal with conductivity 3 of approximately 10 5 S/m. It is well known that the soot produced in a