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 Rb_0.5Cs_0.5PbBr₂Cl₁ 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 Rb_0.5Cs_0.5PbBr₃ 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.