While Light-emitting diode (LED) general lighting continues to rapidly develop and transform the lighting industry, the organic LED light source, or OLED, offers equally dramatic possibilities. Let’s look at the current status of this remarkable technology.
An OLED consists of a stack of thin, organic films sandwiched between two current-carrying electrodes and typically enclosed in plastic or glass. The resulting material is thin but can have a large area. While LEDs are inherently directional point sources, OLED devices are perfectly diffuse area sources, so it is possible to view the light source directly for extended periods without glare.
Today’s OLED devices are typically configured as panels that can be mounted individually or in assemblies together with optics, housings and drivers that supply low-voltage power and control. Optics used to direct the light emission may be built directly into the light source. OLED fixtures install very similarly to LED fixtures, although OLEDs offer the potential to integrate with architectural materials and surfaces such as walls and ceilings, windows, furniture, even clothing. It also offers potential to be manufactured or field-cut in custom shapes and patterns.
While LED sources used for ambient lighting are applied like conventional lighting—with a regular pattern of fixtures designed to promote visual comfort, which can be supplemented by local and accent sources—OLEDs offer exciting potential for new lighting approaches while revolutionizing traditional design.
“In the case of OLED, we can break away from regimented lighting patterns, adding creativity and design flair without sacrificing visual comfort,” said Jeannine Fisher, P.E., L.C., director of OLED business development for Acuity Brands Lighting. “In fact, well-designed OLED luminaires are inherently visually comfortable without the use of louvers, shades or other optical devices typically necessary to control glare. The unique shapes we can craft, and the idea that a luminaire can be designed using sheets of light tiled in patterns, enable free-form motifs for designers to creatively apply in the context of an entire architectural lighting design.”
The lighting industry has made significant investments in research and development and manufacturing capacity to support OLEDs. Today, OLED devices are available primarily in square, rectangular and round shapes in sizes up to 275 cm2, and they produce up to 185 lumens of 2,800–5,000K, 80–90-plus color rendering index light with an efficacy of up to 60 lumens per watt (LPW). Typical panels are about 4-by-4 inches and produce about 75 lumens. The light may be monochromatic or color-tunable using a red, blue and green source mix. OLEDs generate low heat compared to the technology’s LED cousin, resulting in less concern about heat sinking. Rated life is currently 10,000–15,000 hours at L70. Some off-the-shelf LED drivers are compatible with OLEDs.
A number of lighting fixture manufacturers—such as Blackbody, Lumiotec, Modular, Osram, Philips, WAC and Winona (Acuity Brands)—now offer OLED lighting products using panels supplied by LG Chem, Mitsubishi, Osram, Philips and other companies. Due to a high cost of up to $1 to $2 per lumen, these products are typically decorative. Stephen Blackman, principal of Blackman Design Associates, identified three applications well suited to the current mix of performance and cost, including low-brightness outdoor entryway lights, task lights and high-end decorative lighting.
“Exterior lighting at a residential entryway needs only limited intensity to illuminate the immediate area at night,” he said. “The common mounting height at eye level requires the fixture to have less glare so as not to blind visitors at night. Lower exterior illumination levels and low-glare applications are a perfect match for OLEDs.”
As low-voltage devices, OLED fixtures do not have to be installed in front of a recessed junction box as in the case of most conventional fixtures, which allows for flush-mounting even for retrofit in this application. They can be mounted on many surfaces in existing applications using low-voltage wiring and a remote driver.
Blackman said lower brightness general task applications also are well-suited to today’s OLED products.
“These panels can be placed in routed recesses in a cabinet shelving material to make an invisible flush-faced undercabinet light or attached on the underside of a display shelf to illuminate a display case,” he said. “Portable table lamps are the next place that we will be seeing this light source being used.”
A third major application is decorative lighting, with the potential for creating exciting architectural focal points.
“Many consumers and lighting specifiers will pay a higher cost for that which is considered unique and different,” Blackman said. “The thin OLED light source delivers this wow factor.”
These applications will expand as the technology continues to develop. Peter Ngai, P.E., L.C., FIES, vice president of research and development for Acuity Brands, predicts OLED technology will achieve efficacies as high as 150 LPW and rated life of 40,000 hours at L85 by 2016, with cost falling dramatically to as low as $0.05 per lumen by 2014–2015.
“Ultimately, OLED will enable lighting systems that will become less costly, more efficient and, most important, more in tune with the user,” he said.