Evidence of thermal transport anisotropy in stable glasses of vapor deposited organic molecules

Joan Ràfols-Ribé, Riccardo Dettori, Pablo Ferrando-Villalba, Marta Gonzalez-Silveira, Llibertat Abad, Aitor F. Lopeandía, Luciano Colombo, Javier Rodríguez-Viejo

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16 Citations (Scopus)


Vapor deposited organic glasses are currently in use in many optoelectronic devices. Their operation temperature is limited by the glass transition temperature of the organic layers and thermal management strategies become increasingly important to improve the lifetime of the device. Here we report the unusual finding that molecular orientation heavily influences heat flow propagation in glassy films of small molecule organic semiconductors. The thermal conductivity of vapor deposited thin-film semiconductor glasses is anisotropic and controlled by the deposition temperature. We compare our data with extensive molecular dynamics simulations to disentangle the role of density and molecular orientation on heat propagation. Simulations do support the view that thermal transport along the backbone of the organic molecule is strongly preferred with respect to the perpendicular direction. This is due to the anisotropy of the molecular interaction strength that limits the transport of atomic vibrations. This approach could be used in future developments to implement small molecule glassy films in thermoelectric or other organic electronic devices.

Original languageEnglish
Article number035603
JournalPhysical review materials
Issue number3
Publication statusPublished - 29 Mar 2018


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