U.S. Department of Energy - Energy Efficiency and Renewable Energy
Building Technologies Office – SSL Basics
Like any new technology, solid-state lighting must demonstrate a compelling value to buyers before it begins to win sizeable market share from the incumbent technologies it will replace. Over the past decade, research and development have yielded impressive improvements in the cost, color performance, light output, efficacy, reliability, lifetime, and manufacturability of SSL products. Looking at LED packages specifically, the cost in dollars per kilolumen ($/klm) has been declining rapidly since 2005 and is presently falling at a rate of around 20% per year. As a result, some LED lighting products have become competitive with their conventional counterparts in the marketplace for certain applications.
Despite the rapid pace of its development, solid-state lighting has not yet come close to achieving its full potential. Significant work remains to be done to further improve performance and reduce costs.
Light-Emitting Diodes (LEDs)
LEDs are semi-conducting devices that produce light when an electrical current flows through them, and are based on inorganic (non-carbon-based) materials. Optimizing efficiency in LED lighting will hinge on ongoing improvements to materials and light extraction techniques. The LED package remains a significant cost component for many luminaires, but prices in terms of $/klm are declining rapidly. One direction has been to fit more die area into a given package size to achieve higher lumen output; another has been to use a smaller die area in conjunction with cheaper packaging materials. There are many challenges that still need to be met in order to achieve DOE's efficacy goals. For example, we need better greens and reds, as well as multichip monochromatic sources. And we can't afford to overlook such things as color quality, light distribution, reliability, dimming, thermal management, and driver and power supply performance.
Organic Light-Emitting Diodes (OLEDs)
OLEDs are based on organic (carbon-based) materials. Unlike LEDs, which are small point sources, OLEDs are made in sheets that provide a diffuse-area light source. While developing rapidly, OLED technology is less mature than LED technology and still some years away from becoming a practical general illumination source. Innovations are needed on multiple fronts to increase the efficiency, lifetime, and output of OLED devices, and manufacturing infrastructure investments will be essential to transitioning OLED products from the prototype stage to commercial viability. One of the biggest hurdles is price. Increasing the lumen density of the OLED panels can bring down the cost of OLED panels and luminaires, but this can't be done at the expense of panel lifetime. Developing stable novel materials and device architectures that have even higher efficiency and are suited to low-cost manufacturing are the other main challenges. In addition to increasing the efficacy of devices, OLED materials costs need to be simultaneously reduced.
Industry Input Guides SSL R&D Agenda
Two documents guide the DOE SSL R&D Program: the DOE SSL R&D Multi-Year Program Plan and the SSL Manufacturing Roadmap. All funding opportunity announcements (FOAs) and project selections align with these two documents, which are updated annually in collaboration with industry partners. Learn more about the DOE SSL R&D program, guiding roadmaps, annual solicitations, and current DOE-funded R&D projects.