Design of vertically-stacked polychromatic light-emitting diodes

– KN Hui, XH Wang, ZL Li, PT Lai, and HW Choi

SEM image showing an LED stack assembled with LED chips of inverted-pyramidal geometry.

Optics Express, vol. 17, 12, pp. 9873-9878 (2009)

A new design for a polychromatic light-emitting diode (LED) is proposed and demonstrated. LED chips of the primary colors are physically stacked on top of each other. Light emitted from each layer of the stack passes through each other, and thus is mixed naturally without additional optics. As a color-tunable device, a wide range of colors can be generated, making it suitable for display purposes. As a phosphor-free white light LED, luminous efficacy of 30 lm/watt was achieved.

DOI: 10.1364/OE.17.009873