Date/Time: 04-04-2018 - Wednesday - 05:00 PM - 07:00 PM
Maryam Shahi1 Joseph Brill1

1, University of Kentucky, Lexington, Kentucky, United States

Knowledge of the thermal conductivity (k) of new materials is essential for their application in both electronic (high k desired) and thermoelectric (low k desired) devices. We have developed a simplified ac-photothermal apparatus [1] for measurement of the transverse (i.e. through-plane for partly aligned polymers and interlayer for layered crystals) thermal diffusivity, D = k/c, where c is the specific heat per volume, of small samples. Our technique is essentially the Fourier transform of the laser flash method. The sample, with a typical area of 5 mm^2 and heated on its front side with chopped light, is placed in the dewar of an MCT detector close to the detector, which measures the thermal radiation from the back of the sample. For optically opaque samples, an analysis of the complex frequency dependence of the detector signal gives the transverse diffusivity; results will be presented for free-standing PEDOT:PSS films and samples of cellulose nanofibrils coated with PEDOT:PSS (samples provided by X. Crispin, Linkoping U.) For samples which are not opaque, the same analysis, overlooking the finite optical absorption length, can lead to a very large overestimate of the diffusivity. On the other hand, including the effect of finite absorption in the analyses can make their results less definitive. Here we show how the technique and analysis can be adapted for less absorbing samples and present our results for TIPS-pentacene (provided by J. Anthony, U. Kentucky), correcting the value we previously presented [1]. Research supported by NSF Grant # DMR-1262261

[1] J. W. Brill, et al, J. Appl. Phys. 118, 235501 (2015)

Meeting Program

5:00 PM–7:00 PM Apr 4, 2018 (America - Denver)

PCC North, 300 Level, Exhibit Hall C-E