The inclusion of EuCl₃ in CsPbI₃ serves to stabilize the photoactive γ-phase with a bandgap of 1.75 eV, making it suitable for solar energy conversion in tandem solar cells. The study applies X-ray-based techniques to investigate the structural properties and interfacial behavior within this blended material, in comparison with a reference perovskite layer deposited on glass. In addition, Spectroscopic ellipsometry is complemented with density functional theory calculations and photoluminescence measurements to elucidate the absorption and radiative emission properties of the blend.