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

Abstract

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 conductivity because of a reduced deep-level trap density. We also found that Rb substitution enhances the diode characteristics of the PSC, as evidenced by the reduced reverse saturation current ( J 0 ). The optimized (Rb x MA 1– x )PbI 3 PSCs exhibited a PCE of 18.8% with negligible hysteresis in the photocurrent–voltage curve. The results from this work enhance the understanding of the effect of Rb incorporation into organic–inorganic hybrid halide perovskites and enable the exploration of Rb-incorporated mixed perovskites for various applications, such as solar cells, photodetectors, and light-emitting diodes.