Aromatic Molecular Emitters in a Hexagonal Boron Nitride Stack.

Single polycyclic aromatic hydrocarbon molecules embedded in organic matrices are excellent narrow line width quantum emitters. Extending this host-guest setting to van der Waals materials offers the opportunity to combine the preeminent properties of molecular emitters with access to the versatility of two-dimensional heterostructures. In this work, we incorporate perylene molecules into multilayered hexagonal boron nitride (hBN) stacks and observe gigahertz-narrow zero-phonon-line transitions at cryogenic temperatures. We unambiguously verify the origins of photon emission through vibronic spectra analysis. By combining hyperspectral localization measurements with quantum chemistry calculations, we examine the insertion mechanisms of perylene molecules in the stacks and conclude that pristine hBN layers tend to expel molecules from the stacks, while extended morphological defects, hydroxyl groups, and unpassivated boron and nitrogen atoms can assist to stabilize molecular bindings to hBN. Our work provides valuable insight for future work to deterministically integrate narrow line width molecular emitters into van der Waals devices.