Amphiphilic Zwitterion‐Induced Dual Passivation for High‐Performance Sky‐Blue Perovskite Light‐Emitting Diodes

The development of efficient and spectrally stable sky‐blue metal‐halide perovskite light‐emitting diodes (PeLEDs) remains a substantial challenge, primarily due to high‐density defect states and halide ion migration in mixed‐halide quasi‐2D perovskite systems. Here, we introduce an amphiphilic zwitterionic molecule, sulfobetaine 10 (SFB10), as a multifunctional additive to address these limitations in bromine/chlorine mixed quasi‐2D perovskite films. SFB10 enables simultaneous defect passivation and structural stabilization through its complementary functional groups: the sulfonate and quaternary ammonium moieties effectively passivate uncoordinated Pb 2+ ions and cesium vacancies, respectively, while the hydrophobic alkyl chains form a protective layer that enhances environmental stability and suppresses halide migration. This synergistic effect significantly improves the optoelectronic properties of the perovskite films, yielding a notable increase in photoluminescence intensity, an extended fluorescence lifetime, and optimized crystalline morphology with dense, smooth surfaces. As a result, the fabricated sky‐blue PeLEDs (emitting at 485 nm) achieve a significantly improved external quantum efficiency of 2.65% (nearly 70% improvement) and luminance of 1651.1 cd/m 2 , together with exceptional spectral stability under high electric fields. This work highlights the promise of molecularly designed zwitterionic additives in enabling high‐performance and operationally stable perovskite optoelectronic devices.