Nonconventional ways to modify phosphor structures have been reported to enhance the overall luminous efficacy of white light-emitting diodes (LED). Here, a nanoscale texturing technique of a glass substrate with the simple printing process of yellow (Ba,Sr,Ca)2SiO4:Eu+2 silicate phosphor paste is combined to achieve enhanced white luminescence performance. It is demonstrated that the luminous efficacy of the resulting printed phosphor layer can be enhanced by ≈16% as a result of controlling surface roughness of the substrate up to 151 nm. The substantial improvement obtained by texturing both sides of the substrate is attributed to the reduction of total internal reflection of rays at the glass–air interface, combined with reduction of specular reflection at the phosphor–glass interface. For the surface-textured configuration, 3D ray tracing simulations reveal that more rays can be extracted with a widely scattered radiation pattern on the surface. Far-field luminance uniformity is also found to be significantly improved as a result of the texturing technique.
Bibliographical noteFunding Information:
J.S.K. and S.K.E. contributed equally to this work. This work was financially supported by a grant from the National Research Foundation of Korea (NRF-2013R1A2A2A01016711).
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All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Atomic and Molecular Physics, and Optics