A few months ago I spoke of the OLLA project , a consortium of European companies and universities for the development of Orgnic White-LED (WOLED), whose ultimate goal is to be able to improve their technology and thus the luminous efficiency.
Similar groups are also found in other parts of the world, it can be read on site Photonic Nature , a research group of the Michigan Memorial Phoenix Energy Institute and Princeton University has managed to develop a system capable of improving the quantity ' light output, while maintaining the quality of light.
From what we read on the document to be published in Nature Photonics, the problem of reduced efficiency of light emitted by WOLED is mostly due to a constitutive reasons.
In fact, if the issue elettrofosforescente efficiency within the system is equal to 100% due to significant differences in refractive index between the organic layer innermost (ITO-Indium Tin Oxide) n = 1.8 and the layer of glass outer N = 1.45 and between it and the air n = 1 has an internal reflection between each layer that house the trapping of the light flux within the system: only 20% of the luminous flux is issued.
The American research team has thus found a way to remove part of this disadvantage and increase the light output of about 2.3 times (3.7 in simulation).
The solution designed by the researchers consists of a combined carbon grids and micro lenses that "carry" the light out of the layers. The grids in fact guide the trapped light, sending it to a layer of lens-shaped dome that reflects the outside of the device.
here on a chart explaining the operation of the system.
Well, interesting is not it?
soon
James
sources still photonics Galileonet.it
Thu, July 17, 2008
LAMPS , lighting , technology