Frequency-dependent photothermal measurement of transverse thermal diffusivity of organic semiconductors
2015 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 118, no 23, 235501- p.Article in journal (Refereed) PublishedText
We have used a photothermal technique, in which chopped light heats the front surface of a small (similar to 1 mm(2)) sample and the chopping frequency dependence of thermal radiation from the back surface is measured with a liquid-nitrogen-cooled infrared detector. In our system, the sample is placed directly in front of the detector within its dewar. Because the detector is also sensitive to some of the incident light, which leaks around or through the sample, measurements are made for the detector signal that is in quadrature with the chopped light. Results are presented for layered crystals of semiconducting 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-pn) and for papers of cellulose nanofibrils coated with semiconducting poly(3,4-ethylene-dioxythiophene): poly (styrene-sulfonate) (NFC-PEDOT). For NFC-PEDOT, we have found that the transverse diffusivity, smaller than the in-plane value, varies inversely with thickness, suggesting that texturing of the papers varies with thickness. For TIPS-pn, we have found that the interlayer diffusivity is an order of magnitude larger than the in-plane value, consistent with previous estimates, suggesting that low-frequency optical phonons, presumably associated with librations in the TIPS side groups, carry most of the heat. (C) 2015 AIP Publishing LLC.
Place, publisher, year, edition, pages
AMER INST PHYSICS , 2015. Vol. 118, no 23, 235501- p.
Electrical Engineering, Electronic Engineering, Information Engineering
IdentifiersURN: urn:nbn:se:liu:diva-124495DOI: 10.1063/1.4937565ISI: 000367376600058OAI: oai:DiVA.org:liu-124495DiVA: diva2:899664
Funding Agencies|National Science Foundation [DMR-1262261]; Office of Naval Research [N00014-11-0328]; Knut and Alice Wallenberg foundation (Power Paper project) [KAW 2011.0050]2016-02-022016-02-012016-03-03