Thermophysical properties of free-standing micrometer-thick Poly(3-hexylthiophene) films

The solution of Poly(3-hexylthiophene) (P3HT) in chloroform is generally adopted for fabricating P3HT thin films or nanofibers. In this work, 4 regular P3HT solution weight percentages, 2, 3, 5 and 7 wt.%, are compounded to fabricate P3HT thin films by using spin-coating technique. Raman spectrum study suggests that the density of the P3HT thin films varies with different P3HT solution weight percentages while X-ray diffraction analysis reveals that the crystal structures are identical for all P3HT thin films. The transient electrothermal technique is employed to measure the thermal diffusivity of the P3HT thin films and an efficient temperature-resistance calibration is performed to cooperatively study the thermal conductivity. When the P3HT weight percentage changes from 2% to 7%, the thermal conductivity varies from 1.29 W/m·K to 1.67 W/m·K and the thermal diffusivity goes down from around 10− 6 m2/s to 5 × 10− 7 m2/s. The density of P3HT thin films is also determined from the experimental data. The relationship between the density and thermophysical properties clearly demonstrates that the thermal conductivity increases with density while the thermal diffusivity decreases.