Heterostructure Design in Two‐Dimensional Perovskites by Sequential Recrystallization

Low-dimensional metal halide perovskites provide exciting opportunities to fabricate new semiconductor materials. Semiconductor technology relies on electronic heterojunctions, and cost-efficient and flexible approaches to realize functional heterostructures are of fundamental importance. Lateral heterostructures define the energy landscape in the plane of the semiconducting lattice in 2D perovskite materials, representing an ideal platform to tailor energy barriers and to control charge carrier flow. Here, we demonstrate a versatile one-pot synthesis to fabricate a large variety of 2D perovskite heterostructures based on different halides and/or metal cations. Exploiting sequential crystallization of different 2D perovskites and tuning the composition and injection events of the materials, enables the design of diverse heterostructure architectures, including multiple heterojunctions. We obtain heterostructures with high crystalline quality, multicolor emission, and optical coupling between the different heterostructure regions. We foresee that the design freedom of our method will stimulate the development of novel optoelectronic devices where electronic band engineering is crucial.