Layered hybrid lead perovskite single crystals: phase transformations and tunable optical properties

Abstract

Based on the disadvantages of crystal processing and device fabrications of 3D halide perovskites, there is a need to introduce aromatic ammonium into CH₃NH₃PbI₃ to address these concerns. Herein, we report the controllable growth of layered perovskite (C₆H₅CH₂CH₂NH₃)₂(CH₃NH₃)_n−1Pb_nI_3n+1 (n = 1–3) single crystals realised by controlling the proper molar ratio of reactants in the ambient atmosphere. Interestingly, two polymorphs of (C₆H₅CH₂CH₂NH₃)₂PbI₄ single crystals coexisted, and their phase transformation were achieved by different strategies. Moreover, the crystal structure determinations, band gap, optical properties, and thermal stability of the (C₆H₅CH₂CH₂NH₃)₂(CH₃NH₃)_n−1Pb_nI_3n+1 (n = 1–3) single crystals were studied in detail. The (C₆H₅CH₂CH₂NH₃)₂(CH₃NH₃)_n−1Pb_nI_3n+1 (n < 3) single crystals with quantum well structures exhibited strong photoluminescent properties. These intriguing features may lay the foundation for optoelectronic applications of the layered perovskite materials.