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

Abstract

COMMUNICATION (1 of 7)by designed precursor [10] or via postsynthetic exchange reactions. [11][12][13][14][15] Previous researches mainly focused on the effect of exchanging ions on optical properties tuning and phase stability. Among all the three site ions, A cations may be the most special that not only the optical properties but also the dimensions of perovskite structure are related. By introducing long-chain alkylamines as A cations in the precursor, 2D layered perovskites (R 2 A n-1 Pb n X 3n+1 , R is long-chain ammonium and n is the number of octahedral layers) can be prepared with n being precisely controlled. [16][17][18][19] 2D anisotropic structure, where charge carriers are confined in one dimension and free at the other two, possesses unique merits compared with 3D counterparts such as large light absorption coefficient, fast in-plane charge carrier transport, improved stability, and highly thicknessdependent optical and electronic properties. [20][21][22][23][24][25] However, halide perovskites such as cesium lead halide perovskites fit a 3D crystallographic structure, to obtain highquality 2D perovskites, trivial and delicate control including high temperature, optimization of ligands and inert protection are indispensable. [26][27][28][29][30] For example, Bekenstein et al. prepared highly luminescent cesium lead halide nanoplatelets and their oriented assemblies using modified hot injection method, the synthesis temperature was controlled to be 90-130 °C. Shamsi et al., also using hot injection-like method, synthesized single crystal CsPbBr 3 nanosheets with lateral size up to micrometer range by introducing short ligands together with longer ones, the injection temperature as well as the growing temperature was 150 °C. Similarly, Lv et al. also reported on preparation of high-quality cesium lead halide perovskite nanosheets using novel oleylamine-dissolved precursor, the temperature was set at 150-60 °C. Inert gas environment was used in all these methods. However, the products usually suffer from uncontrolled thickness with strong quantum confinement. [31] The preparation of 2D perovskites can also be carried out at room temperature in open environment, but the ultrafast reaction dynamics easily leads to small lateral size, poor crystallinity and stability. Novel strategies enabling facile preparation and highquality 2D halide perovskites are calling for more efforts.2D structure endows halide perovskites with both excellent optoelectronic properties and remarkable stability. Because halide perovskite such as CsPbBr 3 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 spontane...

Ultrafast Carrier Transfer Promoted by Interlayer Coulomb Coupling in 2D/3D Perovskite Heterostructures

“…According to , Supporting Information, and ref. by Zeng et al., the 2D/3D hybrid perovskite synthesized via a cation exchange process is highly crystalline with a consistent orientation, where different perovskite phases are naturally stacked in one microplatelet.…”

“…We synthesized 2D/3D cesium lead halide perovskites following the recipe described by Zeng et al . Briefly, 2D/3D perovskites can be acquired through cation exchange processes (OA + → Cs + ) originating from monolayer OA 2 PbBr 4 .…”

“…Sample Preparation : The synthesis of 2D cesium lead halide perovskite has been described elsewhere . CsBr (0.2 mmol) and PbBr 2 (1 mmol) precursors were dissolved in dimethyl sulfoxide (DMSO).…”

Edge‐State‐Enhanced Ultrahigh Photoresponsivity of Graphene Nanosheet‐Embedded Carbon Film/Silicon Heterojunction

“…We have summarized the figures of merit (responsivity and response time) for some previously reported 2D material photodetector/phototransistors and our device for detailed comparison (see Figure S7 in the Supporting Information for details). The GNEC film/p‐Si photodetector exhibits both a high responsivity (61.52 A W −1 ) and a fast response (350 ns) compared to conventional graphene heterojunctions, other 2D photodetectors, or perovskite photodetectors . Fiber‐shaped ZnO/graphene photodetectors (PDs) based on a Schottky junction have a responsivity of 2.16 A W −1 .…”

Metal Halide Perovskites: Synthesis, Ion Migration, and Application in Field‐Effect Transistors

“…If the compatibility issue of solution‐processed MHP nanoplatelets could be fully solved, it can significantly facilitate the processability of MHP nanoplatelets in the transistor application with probable scalable fabrication. This may also add the gate tunability to all the existing two‐terminal photodetectors and planar light‐emitting devices based on MHP nanoplatelets for enhanced device performance . As for large‐size single crystals, the main problem is how to compactly laminate the single crystal onto the transistor substrate.…”