Impact of structure on exciton physics in organic-inorganic 2D perovskites

Organic-inorganic (hybrid) 2D perovskites is a new class of 2D layer materials that feature unique structural characteristics related to their hybrid nature, which includes soft and dynamic lattice structure and organic-inorganic interfaces. There is still little knowledge of the interplay between, on the one hand, their photo-excited states and electronic properties and, on the other hand, their structural characteristics. Here, using optical spectroscopy and 60-Tesla magneto-absorption, we report the dependence of the formation, dynamics, and recombination of exciton states on the structural and compositional details of hybrid 2D perovskites [Nature Communications 9, 2254, 2018 & Science 355, 1288, 2017]. Our work reveals the changes in the exciton properties due to the tuning of the thickness of the 2D perovskites and the size of the organic molecules in the lattice. The exciton characteristics are explained by an advanced model which includes quantum and dielectric confinement. Moreover, we demonstrate the existence of unique electronic states located at the edges of the 2D perovskite layers, which result from local distortions of the lattice at the edges. Finally, we will provide insight into the hetero-coupling between 2D perovskites and transition metal dichalcogenides.