Halide Exchange via Halogenated Hydrocarbons Toward Bright Deep‐Blue Perovskite Light‐Emitting Diodes

Abstract Halide exchange, achieved by post‐treating perovskite film with a chloride ion solution, has been demonstrated as an effective strategy for achieving deep‐blue perovskites. However, the exchange solution usually utilizes high‐polarity solvents, which can potentially damage the perovskite films, resulting in numerous defects. Here, an effective approach to achieving high‐quality deep‐blue perovskite films through in situ halide exchange using a nondestructive halogenated hydrocarbon solution (BC, benzyl chloride) is presented. It is found that BC, doped with a nucleophile tripropyl phosphine, can release chloride ions through a nucleophilic substitution reaction. Based on this exchange solution, deep‐blue perovskite light‐emitting diodes (LEDs) with color coordinates of (0.137, 0.045), are achieved fully meeting the Rec. 2020 standard. These devices achieve an external quantum efficiency of ≈5% at a high luminance of 1000 cd cm⁻². Moreover, the devices exhibit a half‐lifetime of 42 min at an initial luminance of 100 cd m⁻², representing the most stable deep‐blue perovskite LEDs.