Article

Improvement in uniformity of emission by ZrO₂ nano-particles for white LEDs.

Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, 1001 Ta-Hsueh Road, Hsinchu 300, Taiwan.
Nanotechnology (impact factor: 3.98). 06/2012; 23(26):265201. DOI:10.1088/0957-4484/23/26/265201 pp.265201
Source: PubMed

ABSTRACT The high luminous efficiency and superior uniformity of angular-dependent correlated color temperature (CCT) white light-emitting diodes have been investigated by ZrO₂ nano-particles in a remote phosphor structure. By adding ZrO₂ nano-particles with silicone onto the surface of the phosphor layer, the capability of light scattering could be enhanced. In particular, the intensity of blue light at large angles was increased and the CCT deviations could be reduced. Besides, the luminous flux was improved due to the ZrO₂ nano-particles with silicone providing a suitable refractive index between air and phosphor layers. This novel structure reduces angular-dependent CCT deviations from 1000 to 420 K in the range of -70° to 70°. Moreover, the enhancement of lumen flux was increased by 2.25% at a driving current 120 mA, compared to a conventional remote phosphor structure without ZrO₂ nano-particles. Consequently, the ZrO₂ nano-particles in a remote phosphor structure could not only improve the uniformity of lighting but also increase the light output.

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Keywords

angular-dependent CCT deviations
 
angular-dependent correlated color temperature
 
CCT
 
CCT deviations
 
conventional remote phosphor structure
 
light output
 
luminous efficiency
 
luminous flux
 
novel structure
 
phosphor layer
 
phosphor layers
 
remote phosphor structure
 
silicone
 
suitable refractive index
 
superior uniformity
 
uniformity
 
ZrO₂ nano-particles