Rubidium Fluoride Modified SnO2 for Planar n‐i‐p Perovskite Solar Cells

Abstract Regulating the electron transport layer (ETL) has been an effective way to promote the power conversion efficiency (PCE) of perovskite solar cells (PSCs) as well as suppress their hysteresis. Herein, the SnO 2 ETL using a cost‐effective modification material rubidium fluoride (RbF) is modified in two methods: 1) adding RbF into SnO 2 colloidal dispersion, F and Sn have a strong interaction, confirmed via X‐ray photoelectron spectra and density functional theory results, contributing to the improved electron mobility of SnO 2 ; 2) depositing RbF at the SnO 2 /perovskite interface, Rb + cations actively escape into the interstitial sites of the perovskite lattice to inhibit ions migration and reduce non‐radiative recombination, which dedicates to the improved open‐circuit voltage ( V oc ) for the PSCs with suppressed hysteresis. In addition, double‐sided passivated PSCs, RbF on the SnO 2 surface, and p‐methoxyphenethylammonium iodide on the perovskite surface, produces an outstanding PCE of 23.38% with a V oc of 1.213 V, corresponding to an extremely small V oc deficit of 0.347 V.