Large-scale synthesis of CH3NH3BF4 crystal and its application on CH3NH3PbBrx(BF4)(3-x) perovskite thin films

A simple and environment friendly method for the synthesization of CH3NH3BF4, which exhibits high purity and yield. With close ionic radius, BF4− was doped into CH3NH3PbBr3 perovskite as substitution of Br− to improve the chemical stability of lead halide perovskite. The results show that the doped-BF4− can increase the charge carrier lifetime of CH3NH3PbBrx(BF4)(3-x) perovskite thin films, meanwhile decrease the rate of recombination. This is mainly due to the larger ionic radius of BF4−, which brings about a lower degree X-ray diffraction angle shift, wider ultraviolet visible spectrophotometer absorbance band, red-shift photoluminescence emission peak, and longer fluorescence lifetime.