Diffuse Reflectance Spectroscopy with Dilution: A Powerful Method for Halide Perovskites Study.

Halide perovskites and their low-dimensional analogs are promising semiconductor materials for solar cells, LEDs, lasers, detectors and other applications in the area of photonics. The most informative optical property of semiconductor photonics materials is the absorption spectrum enabling observation of the fundamental absorption edge, exciton structure, defect-related bands, etc. Traditionally, in the study of halide perovskites, this spectrum is obtained by absorption spectroscopy of thin films or diffuse reflectance spectroscopy of powders. The first method is applicable only to compounds with the developed thin film deposition technology, and in the second case, a large absorption coefficient narrows the observations down to the sample transparency region. In this paper, we suggest the diffuse reflectance spectroscopy with dilution as a method for obtaining the full-range absorption spectrum from halide perovskite powders, and demonstrate its application to practically important cases.

Cathodoluminescence of MAPbCl3 Halide Perovskite Single Crystal.

Chloride perovskites are semiconductors with a near-ultraviolet bandgap that are promising for applications in optoelectronics and photonics. One of the most studied representatives of this family is the methylammonium lead chloride MAPbCl3 (MA+ = CH3NH3+). Low-temperature luminescence spectroscopy of this material demonstrates a complex emission structure. In this work, we have studied the cathodoluminescecne of the MAPbCl3 halide perovskite single crystal at 70 K. Excitation by an electron beam was used to localize different emitters: excitons, defect-related states, and inclusions, previously assigned to the material itself. Exciton luminescence is observed from an undamaged sample, while the defect band is emitted from regions with dislocations, growth defects, and crystal damage. Defect formation under electron beam irradiation was studied. It was found that MAPbCl3 is resistant to irradiation, which supports the defect tolerance of halide perovskites and paves the way for their electron-beam modification for applications.