High-Quality MAPbBr 3 Cuboid Film with Promising Optoelectronic Properties Prepared by a Hot Methylamine Precursor Approach.

Though CH ₃ NH ₃ PbBr ₃ single crystals are frequently applied in various optoelectronic devices due to their favorable cuboid geometry, superior optoelectronic properties, and better stability than CH ₃ NH ₃ PbI ₃ , CH ₃ NH ₃ PbBr ₃ polycrystalline films normally show poorer morphology with scattered crystals than their iodide counterparts, inherently due to their different crystallization habits. In this work, a facile process based on a hot methylamine-based precursor with high viscosity and concentration is demonstrated to counteract rapid ion diffusion. The precursor also has special features including a large colloidal size, a solid form at room temperature, and fast crystallization offered by the easy evacuation of methylamine. CH ₃ NH ₃ PbBr ₃ films composed of tightly aligned CH ₃ NH ₃ PbBr ₃ cuboids on micron scale are obtained. Wide channel (100 μm) photodetectors made from the CH ₃ NH ₃ PbBr ₃ films show promising photoresponse and fast response speeds on par with those based on single crystals, suggesting high film quality and good optoelectronic connections between neighboring cuboids.