Atomic Layer Deposition Assisted Encapsulation of Quantum Dot Luminescent Microspheres toward Display Applications

Quantum dots (QDs) are promising for being used in advanced displays due to their outstanding emission properties. Herein, a novel encapsulation method for QDs is reported and ultra-stable QDs@SiO₂@Al₂O₃ luminescent microspheres (QLuMiS) are obtained by combining a sol–gel method for the intermediate SiO₂ layer with a fluidized powder atomic layer deposition (ALD) for the outer Al₂O₃ layer. The rich hydroxyl coverage on the QDs@SiO₂ surface provides abundant chemisorption sites, which are beneficial for the deposition of Al₂O₃ in the ALD process. Simultaneously, the water-oxygen channels in the SiO₂ layer are blocked by the Al₂O₃ layer, which protects the QDs against deterioration. Consequently, the QLuMiS exhibit an excellent stability with 86% of the initial light conversion efficiency after 1000 h of blue light aging under a light power density of 2000 mW cm⁻². Such stability is significantly better than that of QDs@Al₂O₃ and QDs@SiO₂ samples. Moreover, under this strong irradiation aging condition with blue light, the extrapolated lifetime (L50) of QLuMiS is 4969 h, which is ten times longer than that of QDs@SiO₂ and is the best record as far as is known. Finally, a prototype of a QLuMiS-based cellphone screen with a wide color gamut of 115% NTSC is demonstrated.