Effect of Rubidium Incorporation on the Structural, Electrical, and Photovoltaic Properties of Methylammonium Lead Iodide-Based Perovskite Solar Cells

We report the electrical properties of rubidium-incorporated methylammonium lead iodide ((Rb x MA 1– x )PbI 3 ) films and the photovoltaic performance of (Rb x MA 1– x )PbI 3 film-based p–i–n-type perovskite solar cells (PSCs). The incorporation of a small amount of Rb + ( x = 0.05) increases both the open circuit voltage ( V oc ) and the short circuit photocurrent density ( J sc ) of the PSCs, leading to an improved power conversion efficiency (PCE). However, a high fraction of Rb + incorporation ( x = 0.1 and 0.2) decreases the J sc and thus the PCE, which is attributed to the phase segregation of the single tetragonal perovskite phase to a MA-rich tetragonal perovskite phase and a RbPbI 3 orthorhombic phase at high Rb fractions. Conductive atomic force microscopic and admittance spectroscopic analyses reveal that the single-phase (Rb 0.05 MA 0.95 )PbI 3 film has a high electrical cond…