Concentric ring phosphor geometry on the luminous efficiency of white-light-emitting diodes with excellent color rendering property.

ABSTRACT

This study presents a novel remote phosphor design involving a concentric ring remote phosphor layer in which green and red phosphors are separated. The green and red phosphor rings were separately illuminated by blue light emitted from the light-emitting diode (LED), causing low reabsorption in phosphor-converted LEDs (pcLEDs) using green and red phosphors. The experimental results revealed that the pcLEDs with green and red phosphors showed high color rendering, indicating that the LEDs are suitable for certain medical applications and architectural lighting. Moreover, for given green/red phosphor ratio and weights of the green and red phosphors, the output power and luminous flux of the pcLED with a concentric ring remote phosphor layer were greater than those of the pcLED with a mixed remote phosphor layer. The reduction in the reabsorption of green emission by red phosphor in pcLED with a concentric ring remote phosphor layer was responsible for the high luminous flux and indicated a high correlated color temperature of pcLED.