Frequency Domain Thermal Reflectance

Although TE generation has been a mainstay of space missions since the 1950’s, the high cost of traditional semi-conducting TEs has severely limited their presence in the private sector.  The cost of a state-of-the-art TE system exceeds $10/W and must be reduced nearly two orders of magnitude to be commercially viable.  Polymer thermoelectrics are a promising alternative to traditional TEs due to their low cost, high scalability, and ability to wrap around heat sources (e.g. a hot pipe).  Although current polymer TEs have a lower efficiency than the best performing inorganic TEs, the significant reduction in price makes them a more cost-effective option.  Higher efficiency polymer TEs can be realized by better control of in-plane electrical and thermal transport properties.

FDTR Setup

Figure 2: Modified FDTR Setup (Adapted from [3]).

The goal of this work is to develop a non-contact technique that can probe in-plane thermal conductivity in highly anisotropic films.  Frequency domain thermoreflectance (FDTR) is a widely used thermal conductivity measurement technique.  The drawback of FDTR is that it relies on a metal transducer, deposited on the surface of the sample, to generate a thermal signal.  The transducer introduces additional unknown fitting parameters, namely the thermal conductivity of the transducer itself and the thermal conductance of the interface between the transducer and the sample.  These additional parameters introduce measurement uncertainty and may obfuscate physical insights.

  1. Yee, S.K., LeBlanc, S., Goodson, K.E. and Dames, C., 2013. $ per W metrics for thermoelectric power generation: beyond ZT. Energy & Environmental Science, 6(9), pp.2561-2571.
  2. Rodin, D. and Yee, S.K., 2017. Simultaneous measurement of in-plane and through-plane thermal conductivity using beam-offset frequency domain thermoreflectance. Review of Scientific Instruments, 88(1), p.014902.