Abstract
FA(0.95)MA(0.05)Pb(Br0.02I0.98)(3)(CsI)(x) (x = 0, 0.02, 0.05, 0.07) thin films were formed in a dry air atmosphere. The influence of different ratios of CsI-doping on the formed phases, crystallinity, emitted colors and different optical parameters were explored in detail. The spectroscopic ellipsometry (SE) spectra were analyzed using the Kramers-Kronig model. A device based on the film with free Cs has a short-current density (J(SC)) of 20.18 mAcm( - 2), an open-circuit potential (V-OC) of 0.972 V, a fill factor (FF) of 0.67, and a power conversion efficiency (PCE) of 13.04%. V-OC was improved (1.029 V) as the film was doped with 2% Cs, while it was reduced as the films were doped with other higher Cs ratios. The current density (J(SC)) exhibited the highest value (20.18 mA/cm(2)) in the undoped and doped films with 2% Cs and it was reduced with further Cs doping. The FF and PCE were increased slightly (0.67 and 13.83%) as the film was doped with 2% Cs, while these two parameters were reduced as the films were doped with further Cs amounts.