Organic-cation-mixed (FA,MA)PbI3 through sequential vapor growth for planar perovskite solar cells

A sequential vapor-processing route can reproducibly provide uniform and densely packed perovskite layers. Herein, we introduce organic-cation-mixed (FA,MA)PbI3 thin films formed by a sequential vapor process, based on the vacuum evaporation of PbCl2 and following a chemical reaction with mixture vapor of FAT and MAI. The perovskite layers were prepared with different vaporization ratios of FAI and MAI, and organic-cation mixing inside the perovskite structure was verified by the gradual shift of the optical bandgap and lattice constant. Furthermore, all the perovskite layers fabricated by the sequential vapor process exhibited a dense, uniform morphology over the entire substrate area. The planar n-i-p perovskite solar cells were fabricated using TiO2 and spiro-OMeTAD charge-transporting layers. The optimized cell exhibited a maximum efficiency of 15.8% with suppressed hysteresis.