Planar Lighting System Using Array of Blue LEDs to Excite Yellow Remote Phosphor Film

Abstract

This investigation demonstrates a novel light-emitting system with an array of blue light-emitting diodes (LEDs). Unlike a conventional lighting system that is constructed from white LEDs, the proposed planar lighting system uses blue LEDs to excite a YAG : Ce(3+) yellow phosphor film remotely, yielding a high lumen efficiency with uniform and planar light-emission. The phosphor film herein acts as a wavelength converter and a light diffuser simultaneously. The optical properties of the proposed lighting system, angular color deviation and light-emitting uniformity, are studied. Eventually, a high lumen efficiency (73.0 lm/W) and thin lighting module (7.5 mm-thick) was demonstrated without the use of any conventional diffuser plate or light guiding plate (LGP). A low color deviation (Delta u'v' = 0.025) and a high light-emitting uniformity (U(niformity) = 82%) were achieved. Hence, the proposed lighting system exhibited superior optical performance using a compact module.