Quasi-Two-Dimensional Halide Perovskite Single Crystal Photodetector

The robust material stability of the quasi-two-dimensional (quasi-2D) metal halide perovskites has opened the possibility for their usage instead of three-dimensional (3D) perovskites. Further, devices based on large area single crystal membranes have shown increasing promise for photoelectronic applications. However, growing inch-scale quasi-2D perovskite single crystal membranes (quasi-2D PSCMs) has been fundamentally challenging. Here we report a fast synthetic method for synthesizing inch-scale quasi-2D PSCMs, namely (C₄H₉NH₃)_n(CH₃NH₃)_n?1Pb_nI_3n+1 (index n = 1, 2, 3, 4, and ?), and demonstrate their application in a single-crystal photodetector. A quasi-2D PSCM has been grown at the water-air interface where spontaneous alignment of alkylammonium cations and high chemical potentials enable uniform orientation and fast in-plane growth. Structural, optical, and electrical characterizations have been conducted as a function of quantum well thickness, which is determined by the index n. It is shown that the photodetector based on the quasi-2D PSCM with the smallest quantum well thickness (n = 1) exhibits a strikingly low dark current of ∼10^-13 A, higher on/off ratio of ∼10⁴, and faster response time in comparison to those of photodetectors based on quasi-2D PSCMs with larger quantum well thickness (n > 1). Our study paves the way toward the merging the gap between single crystal devices and the emerging quasi-2D perovskite materials.