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Temperature Dependent Reflectance and Ellipsometry Studies on a CsPbBr₃ Single Crystal

Chen, Xiaoxuan, Wang, Yue, Song, Jizhong, Li, Xiaoming, Xu, Jiayue, Zeng, Haibo, Sun, Handong
Journal of physical chemistry 2019 v.123 no.16 pp. 10564-10570
absorbance, absorption, energy, nanomaterials, reflectance, refractive index, spectroscopy, temperature, wavelengths
Inorganic halide perovskites have attracted enormous interest in recent years owing to their remarkable properties for next-generation optoelectronics. Yet their basic optical properties have been rarely explored, which failed to meet the demand of accelerating the progress of this emerging field. In this work, temperature dependent reflection spectroscopy and ellipsometry were carried out on a CsPbBr₃ bulk perovskite single crystal. Two discernible optical transitions at around 2.4 and 3.4 eV with opposite temperature dependence are observed, indicating the complexity of the carrier-phonon scattering process in perovskites. The intrinsic transition energy, exciton–phonon interaction, exciton polariton and strong oscillator strength (∼1.3 × 10³⁰ rad²/s²) of the three-dimensional Wannier–Mott excitons are revealed. We have acquired by ellipsometry measurement the wavelength dependent dielectric constants and the complex refractive indices that are vital for informed optical designs to achieve device performance optimization. Furthermore, the essential and elemental optical properties such as absorption coefficient, absorption cross-section, optical conductivity, and dispersion relation of CsPbBr₃ are obtained. These parameters give insights into both fundamental physics and practical applications of CsPbBr₃ perovskites. This work unveils the photophysics of inorganic perovskites as well as offers approaches to identify the optical transitions and extract essential physical parameters, which can be utilized to explore other perovskite materials and nanostructures.