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

Abstract

A series of 10 perovskite CH₃NH₃Pb(Br_xI_1−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(Br_xI_1−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 × 10³ under an incident light of ∼7.96 mW cm⁻²), rapid response speed (<4 ms), superior photodetectivity and excellent stability.