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 cm² perovskite solar cells and 19.8% for 52 cm² 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.