Republication of Postings from the U.S. Department of Energy (DOE) Solid-State Lighting Program by Jim Brodrick, SSL Program Manager, U.S. Department of Energy
A few months ago, we devoted a Posting to the GATEWAY field study OLED Lighting in the Offices of Aurora Lighting Design, Inc., which — despite several challenges that were encountered — indicated that with continued improvements in efficacy, longevity, size, and flexibility, OLEDs could provide a new tool for creative and effective lighting. Since then, DOE has published two additional reports on OLED lighting: OLED Lighting Products: Capabilities, Challenges, Potential, which describes currently available OLED products as well as promised improvements and major hurdles; and the just-released Photometric Testing, Laboratory Teardowns, and Accelerated Lifetime Testing of OLED Luminaires, the CALiPER program’s first analysis of OLED lighting. Together, these three reports provide a picture of where OLED lighting stands, and what its prospects are.
Several years behind LED lighting technology, OLED lighting is not yet viable in terms of cost, color quality, energy efficiency, dimming and optical performance, and parts standardization. Because of strict energy codes in the architectural market that require the use of more-efficacious luminaires, OLED lighting at present is largely restricted to being used for decoration rather than as the main source of illumination.
In addition, a lack of dedicated OLED drivers on the market has forced manufacturers to use LED drivers, often not well matched for the power requirements of OLEDS, resulting sometimes in low-efficiency operation. And since those drivers are often too bulky to fit discretely into OLED luminaires or mounting canopies, they have to be mounted remotely, which causes extra work and expense.
The color characteristics of OLEDs are better than those of early LEDs, and with improvements in red saturation and overall gamut, OLEDs could meet the color-quality needs of the most demanding interior applications. However, the susceptibility of OLEDs to degradation from air and moisture, and to damage from too much exposure to ultraviolet radiation, makes outdoor lighting a challenge at this point in time.
On the plus side, OLEDs have a number of unique advantages over LEDs — including their large surface area, low luminance, thinness, and diffuse emissions. That’s why OLED panels are already starting to show off their aesthetic attributes in the marketplace in the form of tiles, low-glare panels, and task lights. Those luminaires often take on creative shapes that actually celebrate the light source rather than attempt to conceal it. OLED tiles can be deployed to form words, designs, and artistic patterns; can be incorporated into architectural elements; and can even be used for wayfinding. What’s more, because OLEDs can be mounted near the ceiling, they can be used in low-ceiling settings.
Two especially intriguing potential uses for OLEDs involve making them transparent — so that they could serve as both window and light source — and using flexible substrates, so that the panels could be rolled, curved, or folded. While neither use is commercially available yet, they’re definite possibilities that would significantly increase the value proposition.
Right now, the main competition for OLED lighting is edge-lit LED panels — which, although not as thin as OLED panels, look similar, perform better in several ways, and cost less. Cost is a major barrier for OLED lighting today, and there’s something of a vicious circle in play, with costs currently too high to achieve a level of market adoption that would incentivize investment in high-volume manufacturing, which is needed in order to reduce costs.
The number of OLED lighting products on the market has increased somewhat over the past two years, as the technology continues to evolve at a rapid pace. Improvements in OLED lighting are expected on multiple fronts, which could help OLEDs expand from a niche segment to general lighting applications. Their unique properties and appeal are attracting notice, and if the various barriers that stand in their way are effectively addressed, OLEDs could become an energy-efficient complement to LEDs.
For more details, see the full reports, which are available online.