MASCN Surface Treatment to Reduce Phase Transition Temperature and Regulate Strain for Efficient and Stable α-FAPbI3 Perovskite Solar Cells

The fabrication of & alpha;-FAPbI(3) perovskitefilms usuallyrequires high temperature annealing above 150 & DEG;C, and the residualtensile strain in the films seriously affects the stability of & alpha;-FAPbI(3) by converting to & delta;-phase FAPbI(3). Here, weuse MASCN surface treatment of FAPbI(3) films to induce arotation of the coplanar octahedron [PbI6](4-) to the metric octahedron for the strong interaction of SCN- with Pb2+, converting & delta;-FAPbI(3) into & alpha;-FAPbI(3) highly crystalline films at room temperature.The optimized FAPbI(3) films have high stability due to releasingresidual tensile strains after MASCN treatment. The efficiency ofthe MASCN-treated unannealed FAPbI(3) PSC is 19.03%, whilethe optimized FAPbI(3) annealed at 100 & DEG;C shows a maximumPCE of 21.95% on a small area. The solar cell stability for humidity,light, and thermal stability are significantly improved. The MASCNtreated FAPbI(3) achieves a PCE of 15.32% on a PSC modulewith an effective area of 9.6 cm(2) and maintains an initialefficiency of 94.1% after 100 days of ageing at 85 & DEG;C and 85%humidity.