Application of Cesium on the Restriction of Precursor Crystallization for Highly Reproducible Perovskite Solar Cells Exceeding 20% Efficiency

In this study, we systematically explored the mixed-cation perovskite Cs-x(MA(0.4)FA(0.6))(1-x)PbI3 fabricated via sequential introduction of cations. The details of the effects of Cs on the fabrication and performance of inorganic-organic mixed-cation perovskite solar cells examined in detail in this study are beyond the normal understanding of the adjusting band gap. It is found that a combined intercalation of Cs+ and dimethyl sulfoxide (DMSO) in PbI2-DMSO precursor film formed a strong and steady coordinated intermediate phase to retard PbI2 crystallization, suppress yellow nonperovskite delta-phase, and obtain a highly reproducible perovskite film with less defects and larger grains. The Cs-contained triple-cation-mixed perovskite Cs-0.1(MA(0.4)FA(0.6))(0.9)PbI3 devices yield over 20% reproducible efficiencies, superior stabilities, and fill factors of around 0.8 with a very narrow distribution.