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The LED manufacturing industry has been focusing on achieving higher light output and increased efficacy of monochrome and white LEDs for a wide range of markets, including backlighting, communication, automotive and general illumination. Improving the lumens/watt performance of LED components and managing light output and thermal properties are ongoing challenges. A successful strategy has been the development and introduction of III/V thin film chip technology, which has been combined with white light conversion and low thermal resistance power packages. The recent progress in cost-effective and efficient LED components open the field for new solid state lighting applications, providing both energy savings and environmentally sustainable solutions.
High Brightness Light-Emitting Diodes (HB-LEDs) are key devices for the solid state lighting applications, for instance in general lighting lamps, backlighting devices of flat Liquid Crystal Displays and automotive headlamps. Their compactness and variety of colors enable design solutions that can not be reached with common lighting lamps, in particular in remote and portable electronic devices.
The efficiency is rapidly going well beyond the incandescent and even fluorescent lamps allowing enormous energy savings. However, at that time and in the best case, the Wall Plug Efficiency of white LEDs is no more than 25 % and is not expected to be higher than 50 % in the next decade. Most of the non-radiative energy, i.e., heat, should be dissipated efficiently to keep the junction temperature as low as possible and maintain in particular a good efficiency, a minimal color shift and an extended lifetime. The light output of single chip packaged HB-LED reach now values of several watts making leading to very demanding requirements for the packaging in terms of thermal management, colorimetry, light extraction.
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