Anion- and Cation-Codoped All-Inorganic Blue-Emitting Perovskite Quantum Dots for Light-Emitting Diodes

Despite the high green photoluminescent quantum yield (PLQY) of CsPbBr3 quantum dots (QDs), achieving high blue photoluminescence with fully inorganic perovskite QDs via a simple synthesis method is still challenging. Herein, a facile ligand-assisted reprecipitation (LARP) method at room temperature was used to incorporate Rb, Cl, and mixed Rb–Cl ions into CsPbBr3 QDs, resulting in blue emission. Both undoped and doped CsPbBr3 QDs exhibited the typical rectangular shape of perovskite QDs with a similar size of about 12 nm. Codoping resulted in a widening of the band gap energy (from 2.42 eV in CsPbBr3 QDs to 2.62 eV in Rb0.5Cs0.5PbBr2Cl1 QDs) and a blue shift of the PL emission peak (from 510 to 468 nm). Cl doping reduced the photoluminescence decay time, while 50% Rb doping slightly increased the decay time from 2.44 ns in CsPbBr3 to 2.50 ns in Rb0.5Cs0.5PbBr3 QDs. Thus, Rb mitigated the deleterious effects of Cl, while enhancing the blue shift of the emission line. Rb and Cl codoping enabled the achievement of highly luminescent blue emission from room-temperature-synthesized perovskite quantum dots. Those bright blue-emitting quantum dots are a critical building block toward the fabrication of highly efficient blue perovskite quantum dot light-emitting diodes.