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

Though CHNHPbBr single crystals are frequently applied in various optoelectronic devices due to their favorable cuboid geometry, superior optoelectronic properties, and better stability than CHNHPbI, CHNHPbBr 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. CHNHPbBr films composed of tightly aligned CHNHPbBr cuboids on micron scale are obtained. Wide channel (100 μm) photodetectors made from the CHNHPbBr 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.