Solvothermal Synthesis of Ultrathin Cesium Lead Halide Perovskite Nanoplatelets with Tunable Lateral Sizes and Their Reversible Transformation into Cs4PbBr6 Nanocrystals

The versatility of perovskite crystal structure has become the great advantage of lead halide perovskite nanocrystals (NCs) during their functional applications. Here we report an effective solvothermal method for the controllable synthesis of CsPbBr3 nanoplatelets (NPLs) and their transformation to Cs4PbBr6 NCs. Through solvothermal reaction of a mixture of Cs-oleate and PbBr2 precursors, CsPbBr3 NPLs can be synthesized in mass production. The lateral sizes of CsPbBr3 NPLs can be precisely tuned by varying the solvothermal reaction temperatures and times, while the thickness of NPLs remains constant at ∼4.2 nm, which is in the quantum confinement regime. The fine-tuning of lateral NPL sizes results in precise modulation of their photoluminescence emission. Moreover, an interesting phase transformation from cubic CsPbBr3 NPLs to rhombohedral Cs4PbBr6 NCs, and the reversible transformation from Cs4PbBr6 NCs to CsPbBr3 NPLs can be readily achieved by changing the solvothermal reaction sources. The present solvothermal approach is simple, convenient, controllable, and can be easily extended to preparation of other perovskite NCs with different halide compositions.