Republication of Postings from the U.S. Department of Energy (DOE) Solid-State Lighting Program
by Jim Brodrick, U.S. Department of Energy
Most of the attention given to solid-state lighting these days focuses on LED products, because OLEDs are several years behind their inorganic cousins in terms of development for general illumination. Despite some encouraging progress (e.g., commercially available OLED panels with efficacies of 60 lm/W), OLED lighting is at a crossroads of sorts and faces a number of significant hurdles that will have to be overcome if it’s to become a competitive player in the lighting market.
The OLED industry is very much aware of that, and has been expressing the need for increased collaboration and possibly even a pilot production line to accelerate the development of manufacturing technology for OLED lighting. In response to this, and also seeing an opportunity to bring the OLED community together and create a group with common goals to move the industry forward, the U.S. Department of Energy (DOE) last month convened an open meeting for OLED lighting players, hosted by Trovato Manufacturing in Victor, NY — in what’s turning out to be the primary region for OLED technology in the U.S. A report on the meeting is available at www.ssl.energy.gov/techroadmaps.html.
The meeting was well-attended, and the enthusiasm of the participants was evident in the way they craned forward to hear what others were saying, and in the animated way they shared their own thoughts. Discussions were lively and centered on four main themes. One was the creation of an OLED advocacy and planning coalition — and some initial steps were taken in that direction. Another theme was the need for collaborative OLED R&D, several different models for which were proposed at the meeting. A third focus of discussion was the need for manufacturing and test standards for OLEDs. And the fourth hot topic in Victor was how DOE can best continue to catalyze the U.S. OLED lighting industry.
Although OLED and LED lighting technologies both fall into the category of SSL, and both have the potential to save significant energy, OLEDs have a number of natural advantages for lighting. For one thing, the fact that OLEDs are large-area, diffuse sources (unlike LEDs, which are concentrated sources) could make them more suitable for general ambient lighting, since their soft light can be viewed directly rather than having to be shaded or diffused. And because the diffuse light of OLEDs allows them to be used closer to the task surface, desired illuminance levels can be achieved using less total light. OLED lighting also offers the intriguing possibility of new and even futuristic form factors, because OLEDs can be made to be thin, lightweight, flexible, transparent, and in almost any shape imaginable.
The main barriers facing OLED lighting today are that it’s way too expensive, hasn’t yet been tested in the field, and will have to compete with an ever-growing and rapidly improving range of LED lighting products. The cost question alone is a formidable one. OLEDs intended for general lighting require a large amount of expensive materials, as well as the ability to minutely control the deposition of nanometers-thick layers of material across substrates that could be several meters wide. Even tiny variations in thickness could lead to performance and color variations in the OLED, reducing binned yield and further increasing cost.
One way to address this is to deploy expensive high-throughput manufacturing equipment and rely on economies of scale to bring down material cost and improve yield. This approach is currently being used for the growing OLED display market but may not work for OLED lighting, which has different requirements for both performance and manufacturing — not to mention little if any present demand.
This means that in parallel with increased volume production, there’s a need for fundamentally new technical and manufacturing approaches to OLED lighting that can meet performance and cost requirements. Among the issues that need to be addressed in this regard are improved materials utilization, low-cost light extraction with controlled optical distribution, reduced-cost substrates, and low-cost encapsulation.
The bottom line is that creative approaches are necessary to bring OLED lighting to commercial realization. Technology developers across the value chain need to be encouraged to work together to come up with a commercial manufacturing process that can meet cost and performance targets. Barriers need to be addressed as soon as possible, and the OLED lighting industry can learn a great deal from their LED counterparts in how to overcome these.
The meeting in Victor, NY, was just the beginning. DOE will continue to do what it can to nurture and facilitate the U.S. OLED industry. The conversation started last month will continue in January at DOE’s eleventh annual SSL R&D Workshop. DOE will also continue to support OLED R&D; an upcoming DOE funding opportunity announcement will include priority areas of interest identified in the DOE SSL R&D Multi-Year Program Plan.
OLEDs could serve as an important complementary technology to LEDs for energy-saving lighting design. We expect OLED lighting to be an important part of the lighting conversation — and to create U.S. jobs — but only if the OLED industry works together to advance the technology.
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