One of the most amazing photovoltaic technologies for the future is the organic–inorganic lead halide perovskite solar cell, which exhibits excellent power conversion efficiency (PCE) and can be produced using a straightforward solution technique. Toxic lead in perovskite can be replaced by non-toxic alkaline earth metal cations because they keep the charge balance in the material and some of them match the Goldschmidt rule’s tolerance factor. Therefore, thin films of MAPbI3, 1% Bi and 0%, 0.5%, 1% and 1.5% Sn co-doped MAPbI3 were deposited on FTO-glass substrates by sol-gel spin-coating technique. XRD confirmed the co-doping of Bi–Sn in MAPbI3. The 1% Bi and 1% Sn co-doped film had a large grain size. The optical properties were calculated by UV-Vis spectroscopy. The 1% Bi and 1% Sn co-doped film had small Eg, which make it a good material for perovskite solar cells. These films were made into perovskite solar cells. The pure MAPbI3 film-based solar cell had a current density (Jsc) of 9.71 MA-cm−2, its open-circuit voltage (Voc) was 1.18 V, its fill factor (FF) was 0.609 and its efficiency (η) was 6.98%. All of these parameters were improved by the co-doping of Bi–Sn. The cell made from a co-doped MAPbI3 film with 1% Bi and 1% Sn had a high efficiency (10.03%).
