Effect of the Purity of the Precursor SnI2 on the Optical Properties of CsSnI3 Perovskite Thin Films

Abstract

Abstract The optical properties of CsSnI3 perovskite thin films were investigated. The thin films were obtained from CsI and SnI2 precursors (special-purity grade, 99.999%, 5N), and also SnI2 (99%) by spin-coating from the corresponding solutions. The films were studied by X-ray powder diffraction analysis, scanning electron microscopy, and optical spectroscopy. It was shown that impurities in the initial components affect the optical properties of the obtained material: the absorption coefficient of the perovskite films synthesized from the special-purity grade SnI2 is higher than those of the films produced from 99% SnI2: 4 × 105 cm–1 and 6 × 105 cm–1, respectively. The optical band gap was estimated using the Tauc and Kubelka–Munk models.