Two‐Dimensional Halide Perovskites: Approaches to Improve Optoelectronic Properties

Three‐dimensional (3D) halide perovskites (HPs) are in the spotlight of materials science research due to their excellent photonic and electronic properties suitable for functional device applications. However, the intrinsic instability of these materials stands as a hurdle in the way to their commercialization. Recently, two‐dimensional (2D) HPs have emerged as an alternative to 3D perovskites, thanks to their excellent stability and tunable optoelectronic properties. Unlike 3D HPs, a library of 2D perovskites could be prepared by utilizing the unlimited number of organic cations since their formation is not within the boundary of the Goldschmidt tolerance factor. These materials have already proved their potential for applications such as solar cells, light‐emitting diodes, transistors, photodetectors, photocatalysis, etc. However, poor charge carrier separation and transport efficiencies of 2D HPs are the bottlenecks resulting in inferior device performances compared to their 3D analogs. This minireview focuses on how to address these issues through the adoption of different strategies and improve the optoelectronic properties of 2D perovskites. The current review focuses on various strategies adopted so far in 2D perovskites to reduce the exciton binding energy and enhance the charge‐carrier dissociation efficiency. Improved optoelectronic properties were realized by tuning the quantum and dielectric confinements, crystallographic orientation, interlayer distance, and introducing functional organic cations, charge transfer complexes, and conducting polymers into the perovskite structure.