Graphene, a layer of hexagonal carbon lattice, only allows photons, electrons and protons to pass through but impermeable to any other chemical species. The impermeability and atomic thickness make it an ideal candidate for the protective coating of target materials, which could be air sensitive, photo-unstable or volatile. One series of material, which might be benefited from this application is polyaromatic hydrocarbon(PAH) crystals. Due to their appealing electronic structure and photophysical properties, PAHs are one of the most extensively studied organic semiconductors, with a variety of applications in organic light emitting diodes, field effect transistor and photovoltaic devices. However, the properties of PAHs are sensitive to the presence of impurities, like oxygen. Organic molecular crystal can also be dissolved easily in the organic solvent, or sublime at elevated temperature or in the high vacuum, making them unprocessable under many standard device fabricating processes.<br/>  Here we report a method to encapsulate one of the polyaromatic hydrocarbon semiconducting microcrystals, perylene, using CVD single-layer graphene. The conformal coating of graphene layer around the crystal surface offered complete protection from organic solvents and prevents crystals from subliming at elevated temperature. Raman spectroscopy measurement indicated that the graphene is slighted perturbed by the underlying crystal due to the strain effect. The time-resolved photoluminescence measurements show limited excimers quenching of perylene crystal by graphene. This encapsulation strategy can be extended to other 2D materials, and preliminary experiments using hBN nanosheet to protect molecular crystals will also be described. The encapsulation provides new possibilities for the molecular crystals in various electronic and photonic applications.<br/>

Protection of organic molecular microcrystals encapsulated under two-dimensional materials

2019 Fall National Meeting

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