3-dimensional anisotropic thermal transport in microscale poly(3-hexylthiophene) thin films

Anisotropy in material structure leads to distinct anisotropy in mechanical and thermal properties for polymer materials. In this work, poly(3-hexylthiophene) (P3HT) thin films are fabricated using the spin coating technique for investigation of anisotropic thermal transport. Raman spectroscopy study of spin-coated P3HT films confirms the partially aligned molecular structure. Based on the main orientation of molecular chains, 3-dimensional thermal characterization is performed to understand the anisotropic thermal transport. The thermal conductivity varies from 0.1 to 3.18 W/m K and presents strong orientation-dependent feature. The anisotropy factor for in-plane thermal conductivity spans in the range of 2-4, lower than the factor for perfectly aligned structure. For thermal diffusivity, strong anisotropy is also observed. Particularly, for the out-of-plane direction, the thermal diffusivity is found almost one order of magnitude lower than that in the in-plane direction.