Abstract
The synthesis and application of photonic materials have enjoyed much attention in recent years. However, many fundamental properties of such materials are still unexplored, especially for organic meso- and nanostructured materials. We propose to study the response of the optical and electronic properties of organic meso- and nanostructured materials to high pressure. The orbital overlap in organic materials is a very important factor for their optical and electronic properties. Pressure allows to tune intermolecular distances – and thus the orbital overlap – without changing the chemical composition of a material, and can be seen as an alternative to the more laborious approach of chemical modification. This provides the means to tune the photophysics, e.g., exciton states and exciton-phonon coupling in a material. In addition, solid-to-solid phase transitions between different polymorphs can make different morphologies accessible. In nano- and mesoscale materials, the necessary pressures of such phase transitions depend upon the size of the particles. We will prepare nano- and mesoscale crystals of polycyclic aromatic hydrocarbons (e.g., perylene, rubrene) and subject them to pressures up to 10 GPa in a diamond anvil cell. We will measure absorption, photoluminescence and (where possible) Raman spectra of these materials to determine phase transition pressures as a function of size and polymorph, obtain information on their electronic structure as a function of pressure, and characterize their pressure response as a function on crystallite size.