We propose the use of a frequency-dependent photothermal measurement as a complement to light-flash, i.e., time-dependent, measurements to determine the through-plane thermal diffusivity of small, thin samples, e.g., semiconducting polymers and small organic molecule crystals. The analysis is extended from its previous use with some opaque conducting polymers to materials with finite absorption coefficients, such as crystals of 6,13-bis(triisopropylsilylethynyl)pentacene. Taking into account the finite absorption coefficients of the latter gives a value of diffusivity, D ≈ 0.10 mm2/s, much smaller than previously estimated and more consistent with its expected value. We also briefly discuss the effects of coating samples for the measurement to improve their optical properties.
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This research was supported by the National Science Foundation (NSF) (Grant No. DMR-1262261).
Shahi, Maryam and Brill, Joseph W., "Frequency-Dependent Photothermal Measurement of Thermal Diffusivity for Opaque and Non-Opaque Materials: Application to Crystals of TIPS-Pentacene" (2018). Physics and Astronomy Faculty Publications. 604.