In situ and General Multidentate Ligand Passivation Achieves Efficient and Ultra-Stable CsPbX3 Perovskite Quantum Dots for White Light-Emitting Diodes.

Inorganic CsPbX3 perovskite quantum dots (PeQDs) show great potential in white light-emitting diodes (WLEDs) due to excellent optoelectronic properties, but their practical application is hampered by low photoluminescence quantum yield (PLQY) and especially poor stability. Herein,  we developed an in-situ and general multidentate ligand passivation strategy that allows for CsPbX3 PeQDs not only near-unit PLQY, but significantly improved stability against storage, heat, and polar solvent. The enhanced optical property arises from high effectiveness of the multidentate ligand, diethylenetriaminepentaacetic acid (DTPA) with five carboxyl groups, in passivating uncoordinated Pb2+ defects and suppressing nonradiative recombination. First-principles calculations reveal that the excellent stability is attributed to tridentate binding mode of DTPA that remarkably boosts the adsorption capacity to PeQD core. Finally, combining the green and red PeQDs with blue chip,  we demonstrated highly luminous WLEDs with distinctly enhanced operation stability, a wide color gamut of 121.3% of national television system committee, standard white light of (0.33,0.33) in CIE 1931, and tunable color temperatures from warm to cold white light readily by emitters' ratio. This study provides an operando yet general approach to achieve efficient and stable PeQDs for WLEDs and accelerates their progress to commercialization.

Capping Ligand Engineering Enables Stable CsPbBr3 Perovskite Quantum Dots toward White-Light-Emitting Diodes.

All-inorganic perovskite quantum dots (PeQDs) have sparked extensive research focus on white-light-emitting diodes (WLEDs), but stability and photoluminescence efficiency issues are still remain obstacles impeding their practical application. Here, we reported a facile one-step method to synthesize CsPbBr3 PeQDs at room temperature using branched didodecyldimethylammonium fluoride (DDAF) and short-chain-length octanoic acid as capping ligands. The obtained CsPbBr3 PeQDs have a near-unity photoluminescence quantum yield of 97% due to the effective passivation of DDAF. More importantly, they exhibit much improved stability against air, heat, and polar solvents, maintaining >70% of initial PL intensity. Making use of these excellent optoelectronic properties, WLEDs based on CsPbBr3 PeQDs, CsPbBr1.2I1.8 PeQDs, and blue LEDs were fabricated, which show a color gamut of 122.7% of the National Television System Committee standard, a luminous efficacy of 17.1 lm/W, with a color temperature of 5890 K, and CIE coordinates of (0.32, 0.35). These results indicate that the CsPbBr3 PeQDs have great practical potential in wide-color-gamut displays.