Color-Stable Deep-Blue Light-Emitting Diodes Based on Perovskite Nanosheet Films Passivated with Zwitterionic Choline Chloride and Rubidium Bromide

Incorporating a chlorine ion into a bromine-based perovskite is a straightforward strategy to achieve blue perovskite light-emitting diodes (PeLEDs). However, efficient deep-blue PeLEDs suffer from ineffective chlorine ion supplementation due to the low solubility of chloride and high deep-level defects in perovskite. Here, we propose multifunctional zwitterion choline chloride (ChCl) and rubidium bromide (RbBr) molecules, which not only provide free chlorine ion to fill the halide vacancies but also serve as passivating agents to eliminate Pb⁰ defects in perovskite nanosheets. Consequently, deep-blue PeLEDs were achieved with peak external quantum efficiencies of 3.58%, 2.41%, and 1.10%, which coordinate at (0.134, 0.063), (0.139, 0.052), and (0.141, 0.041), respectively.