A Sputtered Gig-Lox TiO₂ Sponge Integrated with CsPbI₃:EuI₂ for Semitransparent Perovskite Solar Cells

In this study, we propose a novel approach where in an innovative porous grazing incidence atomic flux coupled with local oxidation (gig-lox) TiO₂ electron transport layer (ETL), deposited by sputtering, is integrated with a fully inorganic CsPbI₃:EuI₂ perovskite. This combination is used as a photoactive layer in semitransparent perovskite solar cells (ST-PSC). The solvent-free, scalable porous oxide sponge-like in structure, is produced via a grazing-incidence Ti flux that undergoes localized progressive oxidation. The sponge offers ≈50% volume porosity that is available for perovskite infiltration. The result of the oxide-perovskite integration is a double-layer struc made of a perovskite-filled sponge covered by a cap of pure perovskite. The material has unique optical properties and structure as attested by spectroscopic ellipsometry and X-ray diffraction analyses. The double-layer structure exhibits semitransparency, and its reduced photoluminescence (PL) intensity relative to that of a single perovskite layer indicates efficient charge carrier injection into the porous TiO₂. In perspective, the layer can be used in PSC as demonstrated by simulations.