Perovskite CH3NH3Pb(BrxI1-x)3 single crystals with controlled composition for fine-tuned bandgap towards optimized optoelectronic applications

A series of 10 perovskite CH3NH3Pb(BrxI1-x)(3) (x = 0-1) single crystals have been prepared using a strategy of inverse-temperature reactive crystallization. Using individually optimized precursor solutions of CH3NH3PbBr3 in DMF and CH3NH3PbI3 in GBL, we succeeded in growing single crystals of CH3NH3Pb(BrxI1-x)(3) with [Br] content x regulated in full-range from 0 to 1, which allowed bandgap fine-tuning from 1.53 to 2.24 eV, corresponding to absorption spectrum edge tweaked from green to red. This is considered a significant development because prior literature reports contain only small crystals <6 mm having two discrete compositions, namely Br/I = 15:1 (x = 0.94) and Br/I = 6:1 (x = 0.86). The dual-halide perovskite single crystals have been used to fabricate photodetectors. It is found that crystals with different compositions exhibit a selective optimal response spectrum. The photodetector based on a Br-rich composition (x = 0.78) exhibits optimum light-to-dark response ratio (I-light/I-dark > 1 x 10(3) under an incident light of similar to 7.96 mW cm(-2)), rapid response speed (<4 ms), superior photodetectivity and excellent stability.