Materials for Solid State Lighting
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Materials for Solid State Lighting S.G. Johnson1 and J. A. Simmons2, 1 2
Lawrence Berkeley National Laboratory, 1 Cyclotron Rd, Berkeley, CA 94720 Sandia National Laboratory, P.O. Box 5800, Albuquerque, NM 87185
ABSTRACT Dramatic improvement in the efficiency of inorganic and organic light emitting diodes (LEDs and OLEDs) within the last decade has made these devices viable future energy efficient replacements for current light sources. However, both technologies must overcome major technical barriers, requiring significant advances in material science, before this goal can be achieved. Attention will be given to each technology associated with the following major areas of material research: 1) material synthesis, 2) process development, 3) device and defect physics, and 4) packaging. The discussion on material synthesis will emphasize the need for further development of component materials, including substrates and electrodes, necessary for improving device performance. The process technology associated with the LEDs and OLEDs is very different, but in both cases it is one factor limiting device performance. Improvements in process control and methodology are expected to lead to additional benefits of higher yield, greater reliability and lower costs. Since reliability and performance are critical to these devices, an understanding of the basic physics of the devices and device failure mechanisms is necessary to effectively improve the product. The discussion will highlight some of the more basic material science problems remaining to be solved. In addition, consideration will be given to packaging technology and the need for the development of novel materials and geometries to increase the efficiencies and reliability of the devices. The discussion will emphasize the performance criteria necessary to meet lighting applications, in order to illustrate the gap between current status and market expectations for future product.
INTRODUCTION Light sources used in general illumination have specific optical attributes, which include distribution, intensity, spectral properties and controllability. Other important product attributes include efficacy, lumen maintenance, product life and cost. Understanding these performance attributes and product requirements is necessary for an appreciation of the potential of solid-state light sources to provide energy efficient products with improved product attributes. At this time, however, realizing this goal still requires significant advancements in materials related to this emerging technology. Lighting systems are designed to distribute light to meet a myriad of different lighting applications we experience in our environment. The light sources used in these systems K2.1.1 Downloaded from https:/www.cambridge.org/core. University of Arizona, on 09 Apr 2017 at 14:04:11, subject to the Cambridge Core terms of use, available at https:/www.cambridge.org/core/terms. https://doi.org/10.1557/PROC-722-K2.1
are typically characterized as either point sources or diffused sources. The
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