Mass diffusion coefficient and soret coefficient of o-dichlorobenzene solutions of PCBM and [60]fullerene by the soret forced rayleigh scattering method

We measured the binary diffusion coefficient and the Soret coefficient in the fabrication system of organic photovoltaics (OPVs) by the holographic grating technique we call Soret forced Rayleigh scattering (SFRS). To test the validity of the apparatus we built, we here performed measurements on binary benchmark mixtures: three types of binary solutions (50 wt %) composed of n-dodecane, isobutylbenzene, and 1,2,3,4-tetrahydronaphthalene, at 298.2 K. Our experimental results for the diffusion coefficient and the Soret coefficient agree with the benchmark values within ± 10 %. The uncertainties estimated based on the Guide to the Expression of Uncertainty in Measurement (GUM) for the Soret coefficient on the benchmark mixtures are within 16 % with the coverage factor of k = 2. For OPV systems, our measurements were performed on [60]fullerene or [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) solved in o-dichlorobenzene. We evaluated the Soret coefficient and the diffusion coefficient across a wide concentration range ([60]fullerene/o-dichlorobenzene; (5 to 30) mg·mL^-1 and PCBM/o-dichlorobenzene; (10 to 40) mg·mL^-1) at 298.2 K and the temperature range (288.2 to 333.2) K.