Alloy Perovskite via Dual‐Functional Additive Engineering for Efficient Deep Blue Light‐Emitting Diodes

Abstract Mixed halide perovskites are widely investigated as emitters for efficient light‐emitting diodes owing to their excellent optoelectronic properties. Compared with red and green emissions, encouraging progress in efficiency for blue emission has only been achieved in sky‐blue region. A high Cl/Br ratio is indispensable to achieve deep‐blue emission, which often leads to pronounced halogen migration in perovskite light‐emitting diodes (PeLEDs) and thus diminished efficacy. To avoid the negative effects of excessive chloride necessary to achieve deep‐blue emission, alloyed perovskite quantum dotes (QDs) passivated by dual‐functional guanidine sulfamate are synthesized, where S═O of sulfamate coordinates with Pb, and guanidine can form N‐H‐X (Cl/Br) with halogen ions to complete passivation. As a result, deep‐blue emission is achieved for the alloyed perovskite QDs. Owing to the suppressed defects and the reduced surface electrostatic potential of the perovskite QDs film, the carrier recombination region in the PeLEDs is regulated. Finally, deep‐blue PeLEDs with a spectrally stable electroluminescence peak at 458 nm, peak external quantum efficiency of 3.65% and maximum brightness of 223 cd m⁻² are realized.