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Nanowires for solid state lighting (NWs4LIGHT)
Date du début: 1 juin 2012, Date de fin: 31 mai 2015 PROJET  TERMINÉ 

The suggested project aims at developing a nanowire (NW) technology applied to III-nitride and III-V materials to improve the present Solid State Lighting (SSL) solutions. Present white light emitting diode (LED) emitters are based on thin film III-nitride technology, and a combination of violet-blue LEDs and suitable phosphor coatings has yielded a light emission efficacy of > 100 lm/W with an operating lifetime > 50000 hrs in commercial white LEDs. The color rendering is generally unsatisfactory, however, and the cost is so far prohibitive for general market penetration.Our NW approach is based on combining three (blue-green-red) or four (blue-green-yellow-red) single NW LEDs into one white LED package, thereby avoiding the loss in the phosphor downconversion process. Using NW LEDs we also expect to increase the radiative efficiency due to a drastic reduction of the defect density in the active quantum well (QW) regions of the LEDs, and also improve the extraction efficiency of the emitted light. Our suggested employment of large size silicon or sapphire wafers as substrates is predicted to reduce the future fabrication cost by at least a factor 3. To increase the efficiency of white emitters it is necessary to drastically improve the LEDs emitting in the green-yellow part of the spectrum. We suggest to reach the green LED range by the ability to increase the In composition in the radial QWs of the presently grown nitride NW LEDs, and by using AlGaInP materials. The latter material system will also be explored for yellow and red NW LED emission. To realize yellow-red emission quantum dot media will also be employed, either by the SK growth mechanism on the m-plane facets of the NWs, or by separate application of InP/ZnS core-shell dots with red emission. To realize this work a consortium of five partners is suggested, comprising excellent expertise in growth of NWs and in sophisticated studies of structural, electronic and optical properties of the NWs, and also processing into efficient LED structures having long life-times. The safety issues in the growth and handling of NWs are secured in collaboration with the Nano-Safety project at ULUND. The materials used are favorable from the environmental point of view.



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