Separation Distance Dependence of Luminous Efficiency in Phosphor-Converted White-Light-Emitting Diodes Fabricated Using Open Remote Method

Phosphor-converted white-light-emitting diodes (WLEDs) were fabricated using the open remote method. The separation distance between the blue LED chip and phosphor layer was varied to examine the effects of blue lights penetrating through the annular gaps between the phosphor layer edge and reflector cup walls on the luminous efficiency of the WLED. The WLEDs with a separation distance of 0.55 mm showed the highest luminous efficiency which was close to that of the slurry sample, while the amount of phosphors used was less than 25% of the amount used in the slurry sample. These results suggest that the phosphor quantity used for fabricating the WLEDs can be reduced considerably by the open remote method without any significant loss of luminous efficiency.