The complex refractive indices of formamidinium cesium lead mixed-halide [FA0.83Cs0.17Pb(I1– xBrx)3] perovskite thin films of compositions ranging from x = 0 to 0.4, with both flat and wrinkle-textured surface topographies, are reported. The films are characterized using a combination of variable angle spectroscopic ellipsometry and spectral transmittance in the wavelength range of 190 nm to 850 nm. Optical constants, film thicknesses and roughness layers are obtained point-by-point by minimizing a global error function, without using optical dispersion models, and including topographical information supplied by a laser confocal microscope.

The complex refractive indices of formamidinium cesium lead mixed-halide [FA0.83Cs0.17Pb(I1– xBrx)3] perovskite thin films of compositions ranging from x = 0 to 0.4, with both flat and wrinkle-textured surface topographies, are reported. The films are characterized using a combination of variable angle spectroscopic ellipsometry and spectral transmittance in the wavelength range of 190 nm to 850 nm.

We report the complex refractive index of methylammonium lead iodide (CH3NH3PbI3) perovskite thin films obtained by means of variable angle spectroscopic ellipsometry and transmittance/reflectance spectrophotometry in the wavelength range of 190 nm to 2500 nm. The film thickness and roughness layer thickness are determined by minimizing a global unbiased estimator in the region where the spectrophotometry and ellipsometry spectra overlap. We then determine the optical bandgap and Urbach energy from the absorption coefficient, by means of a fundamental absorption model based on band fluctuations in direct semiconductors. This model merges both the Urbach tail and the absorption edge regions in a single equation. In this way, we increase the fitting region and extend the conventional (αℏω)2-plot method to obtain accurate bandgap values. © 2017 Author(s).

The authors acknowledge funding from the Federal Ministry of Education and Research (BMBF) for funding of the Young Investigator Group Perovskite Tandem Solar Cells within the program “Materialforschung für die Energiewende” (grant no. 03SF0540), the Helmholtz Association within the HySPRINT Innovation lab project, and the HyPerCells joint Graduate School. This research was supported by the joint agreement between the DAAD (German Academic Exchange Service) and FONDECYT (National Fund for Scientific, Technological Development and Technological Innovation) under the agreements 57508544 DAAD and 423-2019-FONDECYT. Further support has been provided by the PUCP vice chancellorship for research (VRI, project no. CAP-2019-3-0041/702). The authors thank Thomas Lußky for technical support, Bor Li for part of the sample preparation, and Norbert Koch, David Cahen, Isaac Balberg and Norbert N...