Near unity quantum yield of strongly-confined blue-emitting CsPbBr₃ quantum dots via lewis base phosphide ligand passivation

Light-emitting diodes (LEDs) based on perovskite quantum dots (PQDs) have been actively pursued due to their unique and excellent optoelectronic performances and exceptionally wide emission spectrum covering from ultraviolet to infrared wavelength. However, despite the recent advances, the blue-emitting PQDs are still suffering from substantially lower efficiency and stability than red or green LEDs due to phase separation, halide vacancies, surface defects, and instability of small-size PQD to maintain the strong quantum-confinement. Here, we suggest a strategy to improve the emission efficiency and stability of blue-emitting CsPbBr₃ QDs in a size regime of strong quantum confinement by exchanging the surface ligand with Lewis base trioctylphosphine (TOP). The TOP-passivated small-size CsPbBr₃ QDs showed a near-unity photoluminescence quantum yield of 97.9 %. The phosphine in TOP effectively passivates the surface of the small-size CsPbBr₃ QDs, consequently improving their emission efficiency and long-term stability. Blue LEDs fabricated by the TOP-treated CsPbBr₃ QDs exhibited an improved luminance of 328 cd/m² and exceptional color stability, maintaining longer emission stability than the pristine QDs.