Thermoelasticity in Organic Semiconductors Determined with Terahertz Spectroscopy and Quantum Quasi-Harmonic Simulations

03 April 2020, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

The thermomechanical response of organic semiconducting solids is an essential aspect to consider in the design of materials for advanced applications, and in particular, flexible electronics. The non-covalent intermolecular forces that exist in organic solids not only result in a diverse set of mechanical properties, but also a critical dependence of those same properties on temperature. However, studying the thermoelastic response of solids is experimentally challenging, often requiring large single-crystals and sensitive experimental apparatus. An alternative contactless approach involves using low-frequency vibrational spectroscopy to characterize the underlying intermolecular forces, and then combining this information with solid-state density functional theory simulations to retrieve the mechanical response of materials. This methodology leverages recent advances in the quasi-harmonic approximation to predict the temperature evolution of crystalline structures, dynamics, and associated forces, and then utilizes this information to determine the elastic tensor as a function of temperature. Here, this methodology is illustrated for two prototypical organic semiconducting crystals, rubrene and BTBT, and suggests a new alternative means to characterizing the thermoelastic response of organic materials.

Keywords

terahertz
dft
QHA
Vibrational Spectroscopy
Organic Electronics
organic semiconductors

Supplementary materials

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BTBT mode1
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BTBT mode2
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BTBT mode3
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BTBT mode4
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Rubrene mode1
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Rubrene mode2
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Rubrene mode3
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Thermoelastics ESI
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