Charge transport and extraction in polycrystalline perovskite films are often hindered by inefficient carrier transfer across grain domain boundaries (GDBs). Herein, we present a universal post-treatment strategy leveraging supramolecular crown ether-assisted slow release and precise delivery of Rb⁺ cations to GDBs, achieving in-situ GDB bridging. The solid-state nuclear magnetic resonance (NMR), transmission electron microscopic (TEM), and time-of-flight secondary ion mass spectrometry (ToF-SIMS) analyses confirm that Rb+ forms a non-perovskite phase, primarily localized at the surface and GDBs. Ultrafast time-resolved photoluminescence mapping revealed accelerated carrier diffusion across the grain boundaries for the Rb+-treated perovskite thin films which enables photo-generated charge carriers to travels over two grain domain boundaries before recombination. As a result, perovskite solar cells treated with this strategy achieved a champion efficiency of 26.02% (certified as 25.77%) and demonstrated remarkable stability, retaining 99.2% of their initial efficiency after 1300 h of continuous one-sun illumination under maximum power point tracking (ISOS-L-1I). Charge transport and extraction in polycrystalline perovskite films are often hindered by inefficient carrier transfer across grain domain boundaries (GDBs). Here, authors employ supramolecular assisted Rb+ delivery for in-situ GDB bridging, achieving efficiency of 26.02% for perovskite solar cells.