Exceptionally low thermal conductivity of poly(3-hexylthiophene) single nanowires

Abstract

Electrical and thermal conductivity measurements were conducted by using microfabricated four-point probe and T-type nanosensors in a vacuum on poly(3-hexylthiophene) (P3HT) single nanowires prepared by the whisker method. The nanowires had a cross-section of only 5 nm x 15 nm and a length of 0.5-10 mu m. The electrical conductance of nanowires was 3.3 x 10(-7) 1/Omega and remained stable even after exposing the wires to ambient conditions for a few days. The thermal conductivity of a nanowire was 0.055 +/- 0.003 Wm(-1) K-1 which was approximately an order of magnitude lower than other previously reported P3HT single nanowires with a diameter of 120 nm and embedded in anodic aluminum oxide matrix. This thermal conductivity was also approximately four times smaller than that of P3HT amorphous thin films (similar to 0.2 W m(-1) K-1). The exceptionally low thermal conductivity was attributed to increased interface-phonon scattering because heat propagation was confined to an extreme narrow spatial dimension.