Study of the crystal morphology of perovskite methylammonium lead bromide single-crystals synthesized by the antisolvent diffusion-induced growth method

The versatile properties exhibited by halide perovskite-based systems make them low-cost, attractive alternatives for various technologies. Their variable energy band gap, high charge carrier mobility, and high photoluminescence intensity, which can be achieved by changing the cation or halide component, make them among the most studied in the field of optoelectronics in recent years. Hybrid (organic-inorganic) halide perovskite single-crystals can be grown into millimeter to centimeter sizes by applying different solution based methods. Among the most important features of hybrid perovskites are; their low production processes and, despite their thermal instability issues, they have strong optical absorption properties. Among the different perovskite structures, MAPbBr3 (MA = CH3NH3+ methylammonium) show superior performances in detecting high energy photons with applications in nuclear detection devices. The MAPbBr3 hybrid perovskite structure exhibits no phase transition due to its stability in the range of 20−100°C, which makes it useful for room temperature applications. Single-crystals will exhibit better electronic properties compared to their nano- or polycrystalline counterparts. In addition, single-crystal perovskites are chemically more stable than thin-film perovskites. In this work, the parametric study for the synthesis of MAPbBr3 by the Antisolvent Vapor Crystallization (AVC) method was carried out. Firstly, the MABr precursor was synthesized. The synthesized MABr crystals were then reacted with PbBr2 at a [MABr] to [PbBr2] ratio of 1:1 and a [MABr] + [PbBr2] concentration between 0.4 M and 1.2 M. Experiments were performed under controlled conditions in a sealed glass vessel, away from daylight for a period of one week at room temperature. AVC experiments were carried out with various antisolvents such as methanol, toluene, ethanol, acetonitrile, dichloromethane, chloroform, isopropyl alcohol and certain mixtures thereof. A slow and controlled crystal growth was determined when using antisolvents with low vapor pressure. Slow-growing crystal structures were observed to be more symmetrical, cube-shaped and also relatively larger in size. Results showed that after only one week of reaction time MAPbBr3 single-crystals of 4 − 5 mm with prsimatic, cube-shaped morphology were synthesized. The surface of the single-crystals were predominantly {100} oriented. Elemental analysis showed a Br to Pb ratio close to the theoretical value of 3. Calorimetric measurements showed highly crystalline structures for the produced MAPbBr3 materials. Band gap energies close to literature values of about 2.3 eV were determined with direct allowed electronic transition properties.