Unraveling the Effect of Halogen Ion Substitution on the Noise of Perovskite Single-Crystal Photodetectors.

Halide mixing in perovskites has been an efficient way to engineer the bandgap, stability, and charge carrier mobility of lead halide perovskites, while its effect on the noise of lead halide perovskite photodetectors is still unknown. We present the preparation of mixed halide methylammonium lead perovskite single crystals by the solution temperature-decreasing method. Planar-structured photodetectors were constructed on the basis of these mixed halide perovskite single crystals. The effect of halogen ion substitution on the noise of devices was investigated by analyzing their dark current spectra. It is shown that the single-crystal photodetectors with higher levels of chloride suffer from larger noise thus have lower detectivity. Density functional theory calculations have also been proposed to reveal the effect of halogens on band structure. These results provide a comprehensive understanding of mixed halide perovskites and may help in the design and preparation of higher-performance devices.