014_EETE

EETE SEPTEMBER 2012

NEWS & TECHNOLOGY LED LIGHTING Innovative LED geometry could increase light output by factor of ten By Christoph Hammerschmidt New tHree-dimeNsioNal assembly of leds could dra- leads to a higher matically multiply the light output compared to today’s planar light output. devices, european scientists hope. the eU research project thus, the manu- GECCO aims at vertically oriented LEDs with much higher effi- facturing of an led ciency. already now, modern high-performance leds provide a becomes much bright light output at high efficiency and are meanwhile applied more cost-effective for automobile headlights, for example. at present, the produc- and as a result replacing ancient electric bulbs, halogen lamps tion process for these kinds of LEDs is still not cost efficient as well as energy saving bulbs to LEDs is getting significantly enough and also the efficiency of these LEDs needs further more profitable. Considering the fact that currently 20% of improvement. electrical energy worldwide is being utilized for illumination, this the international team of the GeCCo project with their part- innovation provides an enormous potential as far as cost-effec- ners from madrid, Bristol, lodz, as well as led manufacturer tiveness is concerned. in addition, led lighting is particularly osram is working on achieving their ambitious objectives. important for future electric mobility. energy saving is of utmost Up to now, leds are being constructed in a planar way, importance in electric cars. meaning in layers and completely flat. The more light is being the dimensions of the ‘light emitting towers’ are within the required, the more wafer area has to be produced - an expen- micrometer range. this means approximately one million leds sive and laborious approach. the idea of the GeCCo project is fit on an area of one square millimeter. This process requires to assemble leds in a three-dimensional way so that actually utmost precision which can only be achieved by applying nano- every led consists of a ‘light emitting tower’ from which the en- technology manufacturing techniques. tire vertical surface is emitting light. obviously the surface of the the GeCCo project is coordinated by Prof. andreas waag tower is much larger compared to the ground area of a planar from the institute of semiconductor technology of the Braun- led. and in fact, it is exactly the gain of light emitting area that schweig technical University. Light-emitting foils could offer cost-effective OLED alternative By Christoph Hammerschmidt researCHers from tHe UNiversity of Umea (sweden) make leCs useful for signage applications. have produced organic light-emitting electrochemical cells the next step in the development was to ensure that the (leCs) using a roll-to-roll compatible process under ambient manufacturing costs can be attractive for commercial applica- conditions. the manufacturing technology developed by the tions. according to a report of the team, published in Nature swedish team opens the perspective on producing extremely Communications, the team managed to deposit a light-emitting thin light emitting foils in an inexpensive layer and a Pedot-Pss anode on top of a process. flexible cathode-coated substrate mounted on applications for the leC foils could a roll by means of a slot-die head, using solely be informative displays. at a later stage air-stable materials in a roll-coater apparatus. of development, the foils could also be the layers in the produced leC device were used for lighting applications, offering a found to be highly uneven, and the layer thick- cheaper alternative to today’s oleds, said ness, for both active layer and anode, was Physics Professor ludvig edman from the very thick at approximately 1µm. However, Umea university. edman’s group at Umea due to the unique self-doping operation of the University is focusing on novel organic LEC, the light emitted did not suffer from the compounds (such as light-emitting and rough interfaces, and was in fact found to be conducting polymers and graphene) and very uniform. this feature is ideal for roll-to- develops leCs based on such materials. the researchers say roll processes, as the demands of the coating quality can be they have dramatically improved the energy efficiency and life- relaxed thus lowering the costs substantially. the researchers time of leCs. they have demonstrated the unique physics and point out that all the steps involved, i.e. preparation of inks, chemistry behind their operation and recently they enhanced the subsequent coating of the constituent layers, and the final the performance of LECs to a point where lifetime and efficiency device operation all could be carried out under ambient air. 14 Electronic Engineering Times Europe September 2012 www.electronics-eetimes.com


EETE SEPTEMBER 2012
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