(253e) Quantification of Halide Inter-Diffusion in Epitaxially Grown Two-Dimensional Perovskite Lateral Heterostructures

Lateral heterostructures of graphene, hexagonal boron nitride (h-BN), transition metal dichalcogenides (TMDs), and oxides have been extensively explored for unravelling novel opto-electronic properties and device physics unattainable by pristine materials. Despite the research advancements made in the field of perovskites, atomically sharp epitaxial lateral heterostructures of two-dimensional (2D) halide perovskites have only been recently reported. Here, we utilized the lateral heterostructure platform to conduct fundamental research on anionic diffusion in 2D perovskites which governs intrinsic material stability and poses one of the greatest challenges in their widespread application. We employed confocal photoluminescence (PL) laser scanning microscopy to visualize the anionic migration across different 2D halide perovskite lateral heterostructures. The calculated diffusion coefficients were found to be 1 ~ 2 orders of magnitude slower in lateral heterostructures based on π – conjugated organic cations compared to short chain aliphatic organic cations revealing their inhibitory effect in Br-I inter-diffusion. These experimental observations are found to be consistent with molecular dynamics (MD) simulation predictions of vacancy assisted inter-diffusion coefficients in compositionally varying halide perovskite lateral heterostructures. The insights gained from this study about the inhibiting role of conjugated organic cations in halide diffusion across 2D perovskites lateral heterostructures will help in guiding future research on smart material design and nanoelectronics fabrication.