Multiple Cations Enhanced Defect Passivation of Blue Perovskite Quantum Dots Enabling Efficient Light‐Emitting Diodes

Abstract All inorganic perovskite quantum dots (ABX 3 , A = Cs, B = Pb, X = Cl, Br, or I) are potential candidates for wide‐color‐gamut display applications. High‐efficiency green and red perovskite quantum dot (PeQD) light‐emitting diodes (LEDs) have been achieved, however, development of blue‐emitting devices, especially those with the relatively short wavelengths (<470 nm) meeting National Television System Committee blue standard, lag largely behind, mainly due to poor film quality, low photoluminescence quantum yield (PLQY) of PeQDs, and unfavorable device structure. Here, a strategy of co‐doping Rb + and Ni 2+ in (Cs 0.8 Rb 0.2 )(Pb 0.95 Ni 0.05 )(Br 1.8 Cl 1.2 ) PeQDs is reported to improve the film quality and PLQY of PeQDs by realizing multiple passivations and modifying the energy band of PeQDs to reduce the hole injection barrier. With further engineering the device structure to facilitate the hole transport, PeQDLEDs based on multiple‐cation PeQDs show the maximum EQE of 2.14% and the emission peak at 467 nm with a full width at half maximum of 16 nm. This work would open up a new avenue to design and develop efficient blue‐emitting materials for high‐performance blue PeQDLEDs.