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EETE JANUARY 2013

optoelectronics Lighting out of the printer By Christoph Hammerschmidt As OLEDs ArE approaching industry maturity, lighting com- not require cleanrooms”, Vollkommer said. Only the machine pany Osram announced that it is already conducting research itself needs to be kept clean of particles which can be achieved for another innovation that has the potential to change the world through constantly supplying clean air. of lighting: Light emitting fibres produced in a printing process. The research has been conducted within the European In the long run, this process could enable to manufacture large- research project CELLO. Besides Osram, also Siemens and area luminaires at very low prices. five research institutes participated in the project. So far the The fibres are based on light- emitting electrochemical cells made of organic materials, so- called OLECs (Organic Light-emit- ting electrochemical cells). Closely related to OLEDs, they however do not incorporate a solid material but a viscous one. This active viscous layer as- sumes the task of conducting electric current as well as emitting the light. In the liquid phase, this material contains freely mobile ions. As soon as a voltage is ap- plied, they accumulate at the edge. Only then, electric charges can be injected into the light emitting layer, effectively creating a light emit- ting diode. By combining various materials appropriately, the cells basically can emit light in any desired color. In a pilot production line in Augsburg, Osram researchers led by Dr. Frank Vollkommerwere able to create functioning lighting cells at a size of 14 x 15 centimeters. They used a plastic foil as sub- researchers were able to achieve LECs with an efficiency of 17 strate with a conductive transparent layer on it. On top, they ap- lumens per watt in the green part of the light spectrum - as a plied another conductive polymer layer by means of a precision comparison an incandescent light bulb achieves an efficiency of slotted nozzle. After an infrared drying step, the light-emitting some 10 lm/w. layer has been applied by means of the same method. The next goals for the project are now higher efficiency and Finally, standard metal electrodes have been vapour deposit- longer operating life. Another challenge is the homogeneity of ed. “In contrast to LED and OLED production, this process does the light emission, Vollkommer said. Toshiba starts GaN-on-Si LED production By Peter Clarke TOsHIBA HAs AnnOunCED that it will start production of silicon wafers, which provides a cost advantage. With back- white light emitting diodes intended for use by makers of ing for Bridgelux from Toshiba, that process was brought to general purpose and industrial lighting using Bridgelux tech- Kaga Toshiba Electronics Corporation, a discrete products nology. manufacturing facility in northern Japan. Plessey Semicon- The white LEDs are made using gallium nitride grown on ductors Ltd. (Plymouth, England) has also adopted a GaN- 200-mm diameter wafers of silicon. Toshiba said it plans to on-Si process for LED production but is presently ramping ramp capacity up to 10 million LEDs per month and said it with 6-inch diameter wafers. wants to secure a 10 percent market share by 2016. The first product of the Toshiba GaN-on-Si line is Production of LED chips is typically done on 2- to 4-inch the TL1F1 series of LEDs that produce 112 lumens at sapphire wafers. Bridgelux Inc. (Livermore, Calif.) developed 350-milliamps current. The packaged parts measure 6.4-mm a method of manufacturing gallium nitride LEDs on 200-mm by 5.0-m by 1.35-mm. 14 Electronic Engineering Times Europe January 2013 www.electronics-eetimes.com


EETE JANUARY 2013
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