A color design model for tunable white light LEDs

May 04, 2017 // By Julien Happich
In a study backed by Taiwan's Ministry of Science and Technology (MOST), Taiwanese researchers have measured the spectrum of custom multi-die (blue and red LEDs) multi-phosphor white LED packages with incremental changes in their phosphors' compositions and densities and derived a matching color design model established from Beer’s law and linear light conversion.

Their paper "Color design model of high color rendering index white-light LED module" published in Applied Optics details the fabrication of white-light LED modules using yttrium aluminium garnet (YAG) and nitride-based phosphors in blue and red LEDs built into 12x13mm arrays. Each module, a 5x5 LED array was made of 5 series of 4 blue and 1 red LED and fabricated with various proportions of phosphors and various densities of phosphors in silicone, with two types of red LEDs.

Moving away for the cheapest white LED solutions with a single blue chip and single yellow phosphor, or the one red and one blue chip combination with a single yellow phosphor, the 5x5 blue-red arrays with two phosphors exhibited a high color rendering index (CRI) and luminous efficacy, while the different proportions in phosphors could be tuned to achieve a precise correlated color temperature (CCT).