Spectroscopic ellipsometry study of CsPbBr3 perovskite thin films prepared by vacuum evaporation

摘要

CsPbX3 (X = Cl, Br, or I) perovskite thin films can be fabricated by vacuum evaporation (VE) with high reproducibility and good film-forming ability. To design optical devices based on CsPbX3 thin films, precise optical constants are required. As only a few optical and dielectric properties of perovskites obtained by VE have been reported, we have comprehensively studied the complex reflective index and complex dielectric function of CsPbBr3 perovskite VE films. Spectroscopic ellipsometry combined with x-ray diffraction and scanning electron microscopy revealed that the three-oscillator model precisely describes the optical constants. Therefore, the wavelength-dependent optical constants of a material can be empirically determined. Time-resolved photoluminescence of a designed CsPbBr3-light-emitting device with a Fabry-Perot cavity and agreement of its dielectric properties with reported data confirmed the existence of a microcavity effect and accurately predicted the electric field intensity distribution and cavity length. This methodology also enables the composition of perovskite to be monitored, which contains a fraction that is desirable for optimizing the performance of optical electronics.