Improving the crystallinity of CH3NH4PbBr3 single crystal thin films via controlling the evaporation of methylamine

Halide perovskite single crystal thin films (SCTFs) have attracted extraordinary attentions due to the promising potential applications as the high-performance optoelectronic devices. However, fabricating the high-quality and large-area perovskite SCTFs is still the main challenge for the future commercialization. In this work, systematical investigations show that the evaporation of methylamine can lead to the precipitation of the PbBr 2 phase, which is one of the major causes of the poor crystallinity and the surface morphology . A simple strategy is demonstrated to improve the crystallinity and properties of MAPbBr 3 SCTFs using the mainstream space-confined method, by controlling the evaporation of the methylamine during the crystal growth, i.e. the growth temperature and the PbBr 2 /MABr molar ratio in precursor. The crystal quality of MAPbBr 3 SCTFs can be improved by lowering the growth temperature and decreasing the PbBr 2 /MABr molar ratio in the precursor. The best MAPbBr 3 SCTF is obtained at 50 °C with the PbBr 2 /MABr molar ratio of 0.85 in precursor solution. The SCTF is in square shape (~2 mm × 2 mm) and with a full width of half-maximum of the rocking curve of (100) crystal plane of 0.051 o . These results will inspire the further explorations in fabricating the high-quality perovskite SCTFs.