A Droplet Method for Synthesis of Multiclass Ultrathin Metal Halides

2D metal halides have attracted increasing research attention in recent years; however, it is still challenging to synthesize them via liquid-phase methods. Here it is demonstrated that a droplet method is simple and efficient for the synthesis of multiclass 2D metal halides, including trivalent (BiI₃ , SbI₃ ), divalent (SnI₂ , GeI₂ ), and monovalent (CuI) ones. In particular, 2D SbI₃ is first experimentally achieved, of which the thinnest thickness is ≈6 nm. The nucleation and growth of these metal halide nanosheets are mainly determined by the supersaturation of precursor solutions that are dynamically varying during the solution evaporation. After solution drying, the nanosheets can fall on the surface of many different substrates, which further enables the feasible fabrication of related heterostructures and devices. With SbI₃ /WSe₂ being a good demonstration, the photoluminescence intensity and photo responsivity of WSe₂ is obviously enhanced after interfacing with SbI₃ . The work opens a new pathway for 2D metal halides toward widespread investigation and applications.