Recently, Duda reported that the fullerene derivative [6,6]-phenyl-C 61-butyric acid methyl ester (PCBM) has the lowest thermal conductivity Λ ever observed in a fully dense solid, Λ ≈ 0.03 W m-1 K-1. We have investigated a variety of phases and microstructures of PCBM and the closely related compound [6,6]-phenyl-C 61-butyric acid n-butyl ester (PCBNB) and find that the thermal conductivities of PCBM and PCBNB films are mostly limited to the range 0.05 < Λ < 0.06 W m-1 K-1 with a few samples having slightly higher Λ. The conductivities we observe are ≈70% larger than reported by Duda but are still "ultralow" in the sense that the thermal conductivity is a factor of ≈3 below the conductivity predicted by the minimum thermal conductivity model using an estimate of the thermally excited modes per molecule.
|Physical Review B - Condensed Matter and Materials Physics
|Published - Aug 21 2013