Spectroscopic ellipsometry of CsPbCl${_3}$ perovskite thin films

TL;DR

This study uses spectroscopic ellipsometry to accurately measure the optical constants of CsPbCl3 thin films, providing essential data for optoelectronic device design and addressing the scarcity of experimental optical data for this material.

Contribution

First application of spectroscopic ellipsometry to CsPbCl3 thin films, developing an optical dispersion model to determine their optical constants and film thicknesses.

Findings

Optical bandgap of ~2.99 eV for CsPbCl3 films

Sharp absorption edge at 411 nm observed

Experimental data agrees with simulation results

Abstract

Designing optoelectronic devices based on cesium lead chloride (CsPbCl${_3}$) perovskites requires accurate values of their optical constants. Unfortunately, experimental data for this material is very limited thus far. Therefore, here, we applied spectroscopic ellipsometry (SE) to measure the complex optical constants of thermally evaporated CsPbCl${_3}$ thin films with different thicknesses on Si/SiO${_2}$ substrates. The data were corroborated with scanning electron microscopy (SEM) images and absorption spectroscopy. An optical dispersion model was developed to derive the complex optical constants and film thicknesses. The Tauc-Lorentz model, in conjunction with two harmonic oscillators, was used to extract the required parameters. The extinction coefficient spectrum exhibited a sharp absorption edge at 411 nm, consistent with the absorption spectrum. In addition, the optical bandgap of the film was calculated from the absorption spectra and SE data. The experimental values agree well with the simulation results, with values of $\sim$ 2.99 eV for different film thicknesses. This work provides fundamental information for designing and modeling CsPbCl3-based optoelectronic devices.