Thermal Resistances of Thin-Films of Small Molecule Organic Semiconductors

TL;DR

This study measures the thermal resistances of thin films of small molecule organic semiconductors, revealing that non-crystalline films have low thermal conductivities similar to polymers, while crystalline films are interface-limited.

Contribution

It provides detailed measurements of thermal resistances across different film thicknesses and distinguishes between intrinsic and interface effects in organic semiconductor films.

Findings

Non-crystalline films have low thermal conductivities similar to polymers.

Thermal resistance increases with film thickness in non-crystalline films.

Crystalline films show interface-dominated thermal resistance.

Abstract

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.