Abstract
White light produced by blue LEDs with yellow phosphor is the most widely used methods, but it results in poor quality in angular CCT uniformity. In this work, a novel technique was introduced to solve this problem by integrating different ZnO nanostructures into white light-emitting diodes. The experiment of ZnO doped films and the simulation of Finite-Difference Time-Domain (FDTD) were carried out. The result indicated scattering effect of ZnO nanoparticles could improve uniformity of scattering energy effectively. Moreover, the effect of ZnO nanostructures on white light-emitting diodes (wLEDs) devices was also investigated. The CCT deviation of wLEDs devices would decrease from 3455.49 K to 96.30 K, 40.03 K and 60.09 K when the node-like (N-ZnO), sheet-like (S-ZnO) and rod-like ZnO (R-ZnO) respectively applied. The higher CCT uniformity and little luminous flux dropping were achieved when the optimal concentrations of N-ZnO, S-ZnO, and R-ZnO nanostructures were 0.25%, 0.75%, and 0.25%. This low-cost and green manufacturing method has a great impact on development of white light-emitting diodes.
Highlights
Light-emitting diodes (LEDs) are regarded as the generation solid-state lighting source because of their long life, high efficiency, low cost and environmental advantages in comparison to conventional incandescent and fluorescent light sources [1,2,3,4]
The Finite-Difference Time-Domain (FDTD) method simulation confirmed that the morphologies of ZnO nanoparticles have a great effect on optical path and the S-ZnO nanostructure with best scattering ability
The correlated color temperature (CCT) deviations of the white light-emitting diodes (wLEDs) devices reduced from 3455.49 K to 96.30 K, 40.03 K, and 60.09 K (2.5 wt% ZnO doping) for N-ZnO, S-ZnO, and rod-like ZnO (R-ZnO), respectively
Summary
Light-emitting diodes (LEDs) are regarded as the generation solid-state lighting source because of their long life, high efficiency, low cost and environmental advantages in comparison to conventional incandescent and fluorescent light sources [1,2,3,4]. Lee et al [29] reported a controllable way of tuning the light emission pattern of the GaN-based blue LEDs using the shape of ZnO nanorods. All of these researches exhibit a huge potential that ZnO nanostructures can be used to enhance the light extraction enhancement of LEDs. to the best of our knowledge, there are few reports on the different ZnO nanostructures were used as diffusers in LED packaging to enhance the optical properties of wLEDs, especially the ZnO with different morphologies effect on the CCT and light intensity uniformity of wLEDs. there remains scope for research into enhancing the CCT and light intensity uniformity of wLEDs by using ZnO nanostructures. We co-doped different concentrations and morphologies of ZnO nanoparticles with silicone as an encapsulant of wLEDs, greatly enhancing CCT uniformity of the wLEDs devices
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