Spatial Confinement-Assisted Vapor-Phase Synthesis of Two-Dimensional Cs₃Sb₂I₉ for Photodetection Application

The boom of halide perovskites has provided rich candidates for optoelectronics in the postsilicon era due to their fascinating material properties and facile achievement through a solution method. The different solubilities of precursors in the solvent, however, often make it difficult for them to react in the required proportions, responsible for poor crystallinity in the final products, along with unsatisfactory device performance. This article reports the high-crystallinity Cs3Sb2I9 flakes fabricated via the one-step vapor-phase deposition assisted by a spatial confinement technique. These two-dimensional Cs3Sb2I9 materials exhibit a large Stokes shift value of approximately 270 meV, a high exciton binding energy of around 108 meV, and an extended excited-state lifetime of 290 ns, in favor of an enhanced electron–phonon coupling process. The two-terminal detectors based on Cs3Sb2I9 flakes display a notable photocurrent response to the incident light @470 nm, revealing a responsivity of 178 mA/W and a detectivity of 1.1 × 109 Jones, comparable or superior to those of lead halide perovskites. The stable and reproducible optical switching characteristics were also simultaneously demonstrated with rise/fall times of 36/21 ms, respectively. All of these results support the solvent-free methodology for the fabrication of inorganic lead-free perovskites, with implications for next-generation green optoelectronics.