Two-dimensional metal halides

Two-dimensional (2D) metal halide materials have recently attracted much attention due to their layered structures, direct bandgap, and high absorption coefficient, rendering them promising applications for electronics and optoelectronics. In addition, they have shown remarkable tunable magnetic properties depending on layer thickness and stacking order. In this letter, recent studies on 2D metal halides and their structural and optical properties, synthesis methods, and applications are reviewed. First, their layered crystal and electronic band structures are presented. Next, synthesis methods, such as mechanical exfoliation, liquid phase method, and vapor phase deposition, are summarized. Additionally, their device performance in field-effect transistors, photodetectors, spintronics, and 2D van der Waals heterostructures are presented. Finally, some conclusions and an outlook for future research are stated.