Simultaneous Interfacial Defect Passivation and Bottom-Up Excess PbI₂ Management via Rubidium Chloride in Highly Efficient Perovskite Solar Cells with Suppressed Hysteresis

In halide perovskite solar cells (PSCs), moderate lead iodide (PbI 2 ) can enhance device efficiency by providing some passivation effects, but extremely active PbI 2 leads to the current density–voltage hysteresis effect and device instability. In addition, defects distributed on the buried interface of tin oxide (SnO 2 )/perovskite will lead to the photogenerated carrier recombination. Here, rubidium chloride (RbCl) is introduced at the buried SnO 2 /perovskite interface, which not only acts as an interfacial passivator to interact with the uncoordinated tin ions (Sn 4+ ) and fill the oxygen vacancy on the SnO 2 surface but also converts PbI 2 into an inactive (PbI 2 ) 2 RbCl compound to stabilize the perovskite phase via a bottom-up evolution effect. These synergistic effects deliver a champion PCE of 22.13% with suppressed hysteresis for the W RbCl PSCs, in combination with enhanced environmental and thermal stability. This work demonstrates that the interfacial defect passivation and bottom-up excess PbI 2 management using RbCl modifiers are promising strategies to address the outstanding challenges associated with PSCs.