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White and white in the green and yellow difference saved? Saudi scientists use nanowires to do the LED

May 10, 2017

Researchers at the King Abdullah University of Science and Technology (KAUST) and King Abdulaziz City for Science and Technology (KACST) have proposed a novel approach that can be used to Multi-phosphor white LED applications are common due to poor conversion efficiency caused by the "green-yellow gap" (green-yellow gap).

 20161101 LED NT01P3 SEM image of the assembly structure using two temperature step growth methods

In a "True Yellow Light-Emitting Diodes as Phosphor for Tunable Color-Rendering Index Laser-based White Light" published in the journal "ACS Photonics", a nanowire LED (NW LED ), Capable of growing on low cost titanium (Ti) thin film / silicon (Si) substrate platforms compatible with CMOS processes. Its tight nanowire layer can grow to a surface density of 9x109 cm ^ 2 with a fill factor of 88%.


The LED NT01P2 component structure shows multiple nanowires grown side by side.

Each nanowire p-i-n LED structure is embedded in a 5-layer 3nm thick InGaN Quantum Disc (Qdisk) stack of active areas, between the layers and 10nm quantum barrier layer separated.

When the yellow light nanowires were operated alone, the researchers observed a peak emission of 588 nm and a low on-voltage of about 2.5 V at 29.5 A / cm ^ 2 (about 75 mA on a 0.5 x 0.5 mm ^ 2 assembly) Quantum efficiency of about 39%, and reached 29.5A / cm ^ 2 before the injection density, and will not appear "efficiency reduction" situation.

Then, the researchers demonstrated the benefits of mixing this yellow and red, green, and blue laser diodes. In the actual setting, the use of RGB light beam irradiation yellow light nanowires LED, like fluorescent, and in the reflective configuration using light scattering layer, in the white light mixture to add its yellow light emission.

The result is a correlated color temperature of about 6000K, and a color rendering index of 87.7


LED NT01P1 yellow light nanowires LED

KoonST Solid State Lighting Technology Innovation Center Director and Electronic Engineering Professor Boon S. Ooi said that the goal of this method is to reduce the white light in the blue light intensity, thus creating a more friendly for the human eye warm white light, while based on the laser The solid state lighting (SSL) provides a new way to tune the color temperature. "At present, we have patented this technology," and this also implies some of the future business opportunities.



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