Facet-dependent exfoliation of two-dimensional halide perovskites

Halide perovskites have emerged as cornerstone materials in the field of optoelectronics due to their exceptional light-harvesting capabilities. Beyond bulk structures, the emergence of 2D hybrid perovskites has opened a new frontier in materials science. These ultra-thin layers are of profound significance because they offer unique opportunities to harness quantum confinement effects, structural flexibility, and high surface-to-volume ratios. Such characteristics allow for precise tuning of electronic and optical properties, making them ideal candidates for the next generation of flexible, transparent, and high-performance optoelectronic devices that surpass the limitations of conventional 3D frameworks.

Inspired by the potential of these low-dimensional structures, researchers led by Shuai Zhao at Chongqing University of Technology, China, focused on the theoretical prediction of all-inorganic 2D perovskites. Using density functional theory, the team addressed a critical question: how does the choice of crystal facet, specifically (100) vs. (111), affect the ease of obtaining these layers and their resulting performance? Their findings demonstrate that the (111) facet generally offers a more feasible exfoliation route in certain configurations, and that the dimensional reduction from 3D to 2D can trigger a transition from direct to indirect bandgaps in many cases due to weakened interlayer electronic coupling. A standout discovery in their work is the monolayer Rb₂SnBr₄, which maintains a direct bandgap, with an effective electron mass of 0.089 m₀ and a hole mass of 0.122 m₀, and superior visible-light absorption. Device simulations using SCAPS-1D further confirm that this material can achieve a theoretical power conversion efficiency exceeding 30% at optimized thicknesses. This work provides a crucial theoretical roadmap for the design of high-performance, Pb-free 2D perovskite devices. The research, entitled “Facet-dependent exfoliation feasibility and optoelectronic properties of two-dimensional all-inorganic halide perovskites”, was published in Frontiers of Optoelectronics (published on Mar. 11, 2026).