Layer-by-layer anionic diffusion in two-dimensional halide perovskite vertical heterostructures

Anionic diffusion in a soft crystal lattice of hybrid halide perovskites affects their stability, optoelectronic properties and the resulting device performance. The use of two-dimensional (2D) halide perovskites improves the chemical stability of perovskites and suppresses the intrinsic anionic diffusion in solid-state devices. Based on this strategy, devices with an enhanced stability and reduced hysteresis have been achieved. However, a fundamental understanding of the role of organic cations in inhibiting anionic diffusion across the perovskite-ligand interface is missing. Here we demonstrate the first quantitative investigation of the anionic interdiffusion across atomically flat 2D vertical heterojunctions. Interestingly, the halide diffusion does not follow the classical diffusion process. Instead, a 'quantized' layer-by-layer diffusion model is proposed to describe the behaviour of the anionic migration in 2D halide perovskites. Our results provide important insights into the mechanism of anionic diffusion in 2D perovskites and provide a new materials platform with an enhanced stability for heterostructure integration. The realization of atomically flat vertical 2D perovskite heterojunctions offers a novel materials platform that reveals the mechanism of anionic diffusion in 2D perovskites.

Automated summary

The use of two-dimensional halide perovskites improves chemical stability and suppresses anionic diffusion in solid-state devices, leading to enhanced device performance. However, the role of organic cations in inhibiting anionic diffusion is not yet fully understood. Our quantitative investigation of anionic interdiffusion in atomically flat 2D vertical heterojunctions reveals a 'quantized' layer-by-layer diffusion model that provides important insights into the mechanism of anionic diffusion in 2D perovskites.