Thermal Resistances of Thin-Films of Small Molecule Organic Semiconductors

We have measured the thermal resistances of thin films of the small molecule organic semiconductors bis(triisopropylsilylethynyl) pentacene (TIPS-pn), bis(triethylsilylethynyl) anthradithiophene (TES-ADT) and difluoro bis(triethylsilylethynyl) anthradithiophene (diF-TES-ADT). For each material, several films of different thicknesses have been measured to separate the effects of intrinsic thermal conductivity from interface thermal resistance. For non-crystalline films of all three materials, with thicknesses ranging from < 100 nm to > 4 microns, the thermal conductivities are similar to that of polymers and over an order of magnitude smaller than that of the crystals, reflecting the large reduction in phonon mean-free path in the films. Thin (< 205 nm) crystalline films of TES-ADT, prepared by vapor-annealing spin-cast films, have also been measured, but for these the thermal resistances are dominated by interface scattering.