In the November edition of LD+A, James Brodrick offers a status report on where the industry is in terms of OLED adoption. An excerpt follows:
The OLED lighting industry today is grappling with a set of difficulties similar to those faced by LED lighting in its early years, but OLED manufacturers have the advantage of being able to see how the LED industry worked through those problems. To assist in the process, the U.S Department of Energy recently conducted three studies to offer insight on the performance of today’s OLED lighting products and the technology improvements needed for commercial viability. OLED Lighting in the Offices of Aurora Lighting Design, Inc., is the first Gateway demonstration involving OLEDs. OLED Lighting Products: Capabilities, Challenges, Potential describes currently available OLED products as well as promised improvements and major hurdles. The third study, Photometric Testing, Laboratory Teardowns, and Accelerated Lifetime Testing of OLED Luminaires, is the first CALiPER analysis of OLED lighting.
While OLED lighting systems are steadily increasing in efficacy (23-45 lumen per watt in the latest CALiPER study), they’re not yet within the range of cost, energy efficiency, color quality, dimming and optical performance, and parts standardization that would make them viable. For one thing, the efficacy of OLED panels (between 42-55 lm/W, according to manufacturer data) is still too low for most architectural applications—restricting their use to decorative elements rather than as the principal light source—because their energy performance is still half or less of the equivalent fluorescent or LED lighting system, and the pressure to meet energy codes in the architectural market is so high.
On top of that, there are few dedicated OLED drivers on the market, because driver manufacturers don’t yet see a growing potential OLED luminaire market. This means that manufacturers have had to work with LED drivers, customizing them as best they can to deliver the current and voltages needed, often outside the optimized efficiency range of the driver. As a result, the driver is a weak point in OLED lighting system efficacy, although the wider availability of dedicated OLED drivers should improve efficacies in the near future.
In addition to driver losses, the driver’s dimming method may introduce performance issues, such as photometric flicker in dimmed conditions. And while OLED panels themselves are thin and light, the drivers are still relatively large and brick-like. Because they may not fit gracefully into the OLED luminaires or mounting canopies, they must be mounted remotely, which poses extra work for the designer and contractor to find an accessible location hidden from normal view, where drivers (and in some cases, transformers) can be located in compliance with the electrical code. For OLEDs to fulfill their promise, driver elements will need to be integrated sleekly and discreetly into the luminaire or mounting elements.
In terms of color characteristics, OLEDs are superior to early LEDs. With further efforts to improve red saturation and overall gamut, OLEDs could meet color-quality needs even for demanding hospitality interior spaces. Outdoor lighting is currently a challenge for OLEDs, because they’re susceptible to degradation from air and moisture, as well as to damage from excessive exposure to ultraviolet radiation,
UNIQUE ADVANTAGES
The plus side for OLED lighting is considerable. OLEDs are dramatically different from LEDs in appearance and lighting performance, which gives them a number of unique advantages. OLED panels are large in surface area, low in luminance, thinner than edge-lit LED panels and usually diffuse in appearance. As such, OLED panels are already showing great aesthetic potential–as tiles, as soft glare-free panels and as task lights. The luminaires that incorporate them often take surprising shapes that celebrate the luminous panel rather than concealing it as a mere light source. As tiles, OLEDs can be used to compose patterns, linear or arrayed; circular arrangements; or random patterns that lead or entertain the eye. They can be incorporated into architectural elements, arranged to produce words or playful patterns, or support wayfinding in buildings. In addition, OLEDs can be mounted near the ceiling, which gives them opportunities in low-ceiling applications.
While transparent OLEDs are not yet commercially available, they represent a unique opportunity in applications where a combination window and light source is desired. Another opportunity is the potential to use thin, flexible substrates to provide OLED lighting products that can be curved, rolled or even folded. At present, OLEDs’ main competition is edge-lit LED panels, which offer similar appearance and superior performance in several respects including cost, but at the sacrifice of panel thinness. It’s rumored that microLEDs may offer competition in the near future.
MAJOR BARRIERS
Cost is the proverbial elephant in the room for OLED lighting. Economies of scale are needed to reduce the cost of manufacturing OLED panels, but the costs are currently too high to achieve the widespread adoption that would incentivize investment in higher-capacity manufacturing. OLED systems, manufactured in small quantities, are far more costly than fluorescent or LED luminaire equivalents, without the energy-efficiency advantages that might balance the equation. When OLEDs can be produced on flexible substrates or printed continuously using a roll-to-roll manufacturing process–or when a similar mass-production method emerges–costs may decrease dramatically. Until then, economic viability is constrained, especially compared to LED technology.
While there are few OLED architectural luminaires on the market, there’s been a modest expansion of products in 2015 and 2016, with more luminaire manufacturers designing and marketing dedicated OLED luminaires. OLED panels and their drivers are rapidly evolving, and improvement in panel efficiency and life, ease of connection and dimming, and stability in light output and color are expected. Although OLEDs represent a niche market segment today, they may expand into general lighting applications as the issues of cost and durability are overcome. At this point, it’s important to understand the tradeoffs, limitations, and issues, so that the industry can work together to maximize the rate of product maturation.
OLEDs are in their infancy compared to LEDs, but the architectural market is taking notice of a lighting product with an entirely different look and function. The potential for using OLEDs as a luminous and dynamic building material is exciting, and if OLEDs increase in efficacy, longevity, size, and flexibility, they’ll give designers and engineers a new tool for creative and effective lighting, and OLED technology could become a complementary solid-state counterpart to LEDs.
DOE’s reports on OLED lighting are available at https://energy.gov/eere/ssl/oled-studies.
November 2016