Spectroscopic ellipsometry and solar cell performance of Cs-doped MA0.05FA0.95Pb(I0.98Br0.02)3 triple cation perovskite thin films for solar cell applications

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.

Automated summary

The influence of CsI doping on thin films was explored, showing that 2% Cs doping can improve short-circuit current density and open-circuit potential, while further Cs doping reduces these parameters. Fill factor and power conversion efficiency slightly increase with 2% Cs doping but decrease with higher Cs amounts.