Cation Exchange-Induced Dimensionality Construction: From Monolayered to Multilayered 2D Single Crystal Halide Perovskites

2D structure endows halide perovskites with both excellent optoelectronic properties and remarkable stability. Because halide perovskite such as CsPbBr3 fits a 3D crystallographic structure, engineering toward 2D structure requires trivial and delicate control. Besides, poor crystallinity and small lateral size are usually accompanied. Here, we report a cation exchange-induced dimensionality construction strategy, based on which high-quality multilayered 2D perovskite single crystals are constructed with monolayered OA(2)PbBr(4) (OA is in short for octadecylamine). Due to the 2D characteristic of OA(2)PbBr(4) structure, it spontaneously grows into several micrometers laterally at room temperature with high crystallinity, the large size as well as the high crystallinity is then handed down to resulted multilayered 2D cesium lead halide perovskites via a cation exchange strategy. Specifically, intended exchange of OA(+) with Cs+ in OA(2)PbBr(4) releases the [PbBr6] sublayers previously sandwiched by OA(+) bilayers. Cs+ suits a 3D perovskite structure and therefore assembles the [PbBr6] sublayers to form single crystal multilayered 2D cesium lead halide perovskites. The superior optoelectronic properties of resulted 2D cesium lead halide perovskites are exhibited by planar photodetectors that achieve ultrahigh external quantum yield and responsivity up to 11 050% and 44 A W-1. Besides, extremely short rise/decay time of 7.1/45 mu s is also obtained.