Angularly Uniform White Light-Emitting Diodes Using an Integrated Reflector Cup

– L Zhu, XH Wang, PT Lai, and HW Choi

Schematic diagram showing cross-sectional views of LED coating using three different methods: (a) phosphor-slurry coating; (b) conformal coating; (c) remote phosphor coating; (d) 3-D schematic diagram of a Truncated Conical-LED (not to scale).

IEEE Photonics Technology Letters, vol. 22, 7, pp. 513-515 (2010)

We report on white light-emitting diodes (LEDs) with a truncated-conical (TC) geometry produced by laser micromachining. A blue LED was shaped into a circular disc with 50°-inclined sidewall using a modified laser micromachining setup. A layer of Al was coated onto the inclined sidewall and the bottom surface to form an integrated reflector. Due to the highly reflective mirror, laterally propagating photons are redirected into the upward direction, contributing to an increase of 21.7% of light intensity in the normal direction. With quantum dots applied to the surface, white light emission from this TC-LED structure demonstrated a 37% enhancement in color uniformity, compared with a conventional device.

DOI: 10.1109/LPT.2010.2041651