Engineering optoelectronic properties of the Pb-free perovskite FASiBr3 − XIX (X = 0, 1, 2 or 3) for photovoltaic applications: first principle analysisYoussef El Arfaoui, Mohammed Khenfouch, Nabil Habiballah and Simone GiusepponiEur. Phys. J. B, 98 4 (2025) 61DOI: https://doi.org/10.1140/epjb/s10051-025-00909-2