Correlational study of halogen tuning effect in hybrid perovskite single crystals with Raman scattering, X-ray diffraction, and absorption spectroscopy

Organic-inorganic hybrid halide perovskite single crystals have been noted to highly efficient photo-voltaics with high absorption coefficients, a tunable band gap in the visible range, low trap-state density, and long carrier diffusion length. In this work, the intrinsic properties of halogen tuned mixed halide perovskite crystals were characterized using Raman scattering, which was recorded at excitation wavelengths of 785 and 1064 nm with photo-degradation taken into consideration. The Raman spectra showed that the Raman shifts associated with the perovskites were directly correlated with their lattice parameters measured by X-ray diffraction, which demonstrates that the vibrations of the organic compounds were affected by the inorganic cage of the halide components. In addition, the absorption edges of the samples varied linearly with lattice constant, which showed a strong correlation between the Raman shifts and optical band gaps. These correlations indicate that non-invasive Raman scattering is available to identify the halide derivatives without further characterization. (C) 2017 Elsevier B.V. All rights reserved.