Simultaneously Enhancing the Angular-Color Uniformity, Luminous Efficiency, and Reliability of White Light-Emitting Diodes by ZnO@SiO2 Modified Silicones

In this paper, we demonstrate that through normal dispenser machines, white light-emitting diodes (wLEDs) with good angular-color uniformity can be obtained with the use of ZnO nanoparticles (NPs). A ΔCCT of 148 K at a correlated color temperature (CCT) level of 6000 K in the angle range of -90° to 90° can be realized by mixing ZnO-QD₂ NPs (r = 5 nm) at a concentration of 3 wt% with the luminous efficiency loss being less than 5%. If modifying the surface of ZnO by SiO₂ shell, i.e., ZnO@SiO₂, at a concentration of 1 wt%, wLEDs with good comprehensive performances, i.e., angular CCT uniformity, luminous efficiency, and reliabilities are achieved. The ΔCCT is less than 850 K in the angle range of -65° to 65° at a CCT level of around 7000 K. The normalized luminous efficiency is enhanced by a ratio of 8.5%. A SiO₂ shell of ZnO cores can benefit compatibility between inorganic fillers and organic matrix. Reasons for the existence of an optimized concentration of ZnO@SiO₂ in silicone are discussed.