Reversing the Reaction Order Between FA+ and Rb+ Enhances the Photovoltaic Performance of Blade‐Coated Perovskite Solar Cells

Abstract Manipulating the kinetics of the reaction between A‐site cations and Pb‐I frameworks holds paramount importance for achieving high‐quality, phase‐homogeneous FA‐dominant perovskites. It has been observed that when rubidium (Rb) serves as an A‐site cation dopant, it tends to accumulate in the bulk region of the perovskite structure due to its pronounced affinity for Pb‐I frameworks compared to FA + . Consequently, Rb + ions struggle to alleviate the exaggerated tensile strain induced by the bulky FA cations on the perovskite surface. To mitigate this challenge, 5‐hydroperoxy‐1‐methyl‐2‐pyrrolidinone (HMP) is introduced as an additive to invert the sequence between FA + and Rb + in reaction with the Pb‐I frameworks. The introduction of HMP effectively stabilizes Rb + cations within the perovskite lattice, leading to a surface enriched with Rb that exhibits diminished lattice strain and defects. Finally, a record power conversion efficiency (PCE) of 25.8% for 0.09 cm 2 perovskite solar cells and 19.8% for 52 cm 2 mini‐module is achieved, which are fabricated via blade coating under ambient conditions with a relative humidity of ≤55%. Notably, these cells exhibit minimal hysteresis and demonstrate significantly enhanced resilience against illumination, dampness, and heat.