Dimension and Thickness Control Synthesis of Strongly Confined Cesium Lead Iodide Perovskites with Excellent Two-Photon Absorption Properties

Due to narrow emission peaks, high absorption cross section, and exciton binding energies, CsPbX3 perovskite-based nonlinear optical (NLO) materials are promising for next-generation quantum photonic technologies. Herein, we report dimension and thickness control synthesis of strongly confined cesium lead iodide perovskite materials, which exhibit excellent two-photon absorption (TPA) properties. Our finding reveals that the synthesis of red-emissive zero-dimensional (0D) Cs4PbI6 perovskite nanocrystals (NCs), one-dimensional (1D) CsPbI3 nanowires (NWs), and two-dimensional (2D) CsPbI3 nanoplatelets (NPLs) can be controlled by varying the temperature. Moreover, NPLs with different thicknesses can be obtained by varying the ratio of the Pb–I precursor and Cs–oleate. Furthermore, we report that the zero-dimensional (0D) Cs4PbI6 exhibits a very high two-photon absorption cross section (σ2 ∼ 12.8 × 106 GM), which is several orders of magnitude higher than the two-photon absorption cross sections reported for organic chromophores (>100 GM). Interestingly, experimentally obtained σ2 for 0D Cs4PbI6 is an order of magnitude higher than 3D CsPbI3 NCs and varies with dimensions in the following order: 0D Cs4PbI6 NCs > 1D CsPbI3 NWs > 2D CsPbI3 NPL > 3D CsPbI3. Although experimentally observed σ1 variations correlate with the volume of perovskites, σ2 does not correlate with the volume of the material. Notably, volume-normalized σ2 (VN) is highest for 2D CsPbI3 NPLs with 1.6 nm thickness, and it decreases with the increase of thickness for NPLs, which is due to the quantum confinement effect. Overall, this work provides how dimension, volume, and quantum confinement engineering can be used to design the TPA material for possible device applications.