The impact of high pressure on the vibrational spectrum of molecular organic semiconductors

The van der Waals nature of organic semiconductors (OSCs) offers low cost processing while intermolecular vibrations affect their charge transport properties. By using inelastic neutron scattering and terahertz spectroscopy, combined with quantum mechanical simulations, we have characterized for the first time the full-spectrum of low-frequency motions in several OSCs, identifying the long axis sliding motion as the killer phonon mode. Within this framework, the aim of this proposal is to push our study further and investigate the impact of pressure on the vibrational spectrum present in these soft materials. This will allow us to 1) understand the impact of pressure on the thermal disorder in OSCs, 2) elucidate how the killer phonon modes are hampered as a function of molecular design and packing, 3) test if there is a critical pressure value at which killer phonon modes are affected and, 4) develop potential pressure/strain strategies to improve transport properties in these soft materials.