Scalable Fabrication of Efficient Sky-Blue Perovskite Light-Emitting Diodes with Dual Salts

Bromide (Br)-chloride (Cl) mixing in three-dimensional (3D) perovskites provides an effective method for band gap engineering for blue emission. However, their low formation energy and poor solubility trigger rapid crystallization at room temperature, leading to extensive defect formation. Here, we introduce dual organic salts into the perovskite precursor solution to suppress crystallization and defect formation. Specifically, the tetraphenylphosphonium salt forms multiple weak interactions with lead halide octahedra, slowing 3D perovskite growth, while simultaneously directing the guanidinium slat to passivate A-site vacancies instead of forming low-dimensional perovskite. This strategy eliminates the need for antisolvent or post-treatment processes, enabling scalable device fabrication without compromising performance. As a result, sky-blue light-emitting diodes (LEDs) with active areas of 3 and 900 mm² exhibit peak external quantum efficiencies of 13.5% and 11.2% and maximum luminance values of 5493 and 843 cd m^-2, respectively. This work provides a useful route toward large-area blue perovskite LEDs.