Bottom Anchoring Enables Uniform Cations and Strain‐Free Crystallization for Efficient and Stable Inverted Perovskite Solar Cells

ABSTRACT Cs x FA 1‐x PbI 3 –based perovskite solar cells inevitably exhibit uneven Cs–FA cation distribution, leading to crystallization defects that degrade device performance. Here, we design a highly electronegative hexafluorocyclotriphosphazene (HFPN) ligand to regulate perovskite film formation. Multifluorinated functional groups precisely control crystallization kinetics, producing high‐quality perovskite films with high carrier mobility. Critically, HFPN anchors FA + at the film bottom, achieving a uniform out‐of‐plane cation distribution and eliminating residual tensile stress within the perovskite layer. The resultant MA/Br free devices accomplish a power conversion efficiency of 26.55% and 24.67% at a larger area (1 cm 2 ) with negligible hysteresis. The devices retain >95% of the initial efficiency after 1251 h of continuous maximum power point tracking under simulated AM 1.5 illumination and after 1046 h under damp‐heat conditions (85°C and 85% RH), respectively.