Effect of Li-salt additives on the optical features and solar cell performance of Cs0.05FA0.85MA0.10Pb(I0.90Br0.10)3 perovskite solar cells

Abstract

Glass substrate/FTO/Compact TiO2/Mesoporous TiO2 layers/x mg LiTFSI/Cs0.05FA0.85MA0.10Pb(I0.90Br0.10)3 films were prepared. The effect of bis(trifluoromethane)sulfonimide lithium (LiTFSI) salt on the phases formation, crystal structure and crystallinity of pervoskite Cs0.05FA0.85MA0.10Pb(I0.90Br0.10)3 layer was investigated using X-ray diffraction technique. The influence of the LiTFSI additives with different ratios on the optical features of Glass substrate/FTO/Compact TiO2/Mesoporous TiO2 layers/x mg LiTFSI/Cs0.05FA0.85MA0.10Pb(I0.90Br0.10)3 films was studied using UV spectrophotometric technique. The optical bandgap energies for all films were found to be 1.58 eV. The maximum value of refractive index (n = 2.6) for the film without LiTFSI was observed in the IR range, while in the visible range, the film with 21 mg of LiTFSI has a maximum n value (∼2.3). In the UV and visible regions, the film with 21 mg LiTFSI has the highest nonlinear optical parameters (NLO) values, while in the IR range, the film without LiTFSI salt has the highest NLO values. The effect of LiTFSI salt on the photoluminescence emitted spectra was also examined. The power conversion efficiency (PCE) and fill factor (FF) were enhanced to 18.85 and 76.6%, respectively, as the amount of LiTFSI additive became 21 mg.