Achieving highly uniform two-dimensional PbI₂ flakes for photodetectors via space confined physical vapor deposition

Two-dimensional (2D) PbI₂ flakes have been attracting intensive attention as one potential candidate for the modern optoelectronics. However, suffered from the instability of kinetics-driven growth, the fabricated 2D PbI₂ flakes have a wide dimensional distribution even under the same conditions. Herein, a novel facile space confined physical vapor deposition (PVD) process is provided to synthesize uniform triangle PbI₂ flakes with high quality. The confined space provides a relatively stable growth environment that renders more control on the growth kinetics, leading to highly uniform triangle PbI₂ flakes with the average size of 5 µm and thickness of 17 nm. Moreover, as-fabricated PbI₂-based photodetectors show promising stable and flexible optoelectronic performances to 470 nm light, including high responsivity (0.72 A W^-1), large on/off ratio up to 900, fast photoresponse speed (rise time of 13.5 ms and decay time of 20 ms) and high detectivity (1.04 × 10¹⁰ Jones). The well-controllable growth of the uniform triangle PbI₂ flakes and the detailed exploration of their optoelectronic properties are particularly valuable for their further practical applications.