Materials design and preparation of ultrathin two-dimensional metal halide perovskites

Metal halide perovskites (MHPs) have emerged as highly promising candidates for the next generation of photonics and optoelectronic devices, owing to their prominent optical and excitonic properties, as well as the convenience of fabrication. Particularly, ultrathin two-dimensional (2D) MHPs, which are generally prepared by exfoliation, solution growth, and chemical vapor deposition method, have attracted dramatically increasing attentions owing to their combined features of ultrathin 2D morphology and superior performance of MHPs. Despite the growing interest in ultrathin 2D MHPs, there is currently a lack of a comprehensive and systematic overview of the distinct advantages offered by each growth method for producing these materials. This review critically assesses the preliminary studies on the materials design and preparation of ultrathin MHPs. Furthermore, it explores heterostructures based on ultrathin MHPs and offers insights into the challenges and opportunities that lie ahead for this enticing class of 2D materials.