OLED Lighting Hits the Market
Performance and design freedom are advancing organic light-emitting diode (OLED) lighting, providing differentiation from general lighting to transportation and more. OLED is the first naturally diffuse lighting, with pure qualities highly prized by designers. Razor thin with superb color characteristics and uniformity, OLED offers an alternative to high-glare lighting sources and allows a variety of innovative applications and attractive designs.
by Giana M. Phelan
AS a solid-state lighting (SSL) technology, OLED has many of the attributes of its elder cousin, LED. It is mercury free, compatible with standard control and dimming solutions, and requires direct current (DC) power. The promise of OLED has been heralded for some time, but recent technology gains have been achieved at a relatively breakneck speed. For example, LEDs were demonstrated as a practical component in 1962, while OLEDs were first demonstrated in 1987. With OLED light engines now at 60 to 80 lumens per watt (LPW), OLED has arrived for many applications.
Furthermore, as shown in Fig. 1, the price of OLED lighting continues to fall as performance increases. This combination of affordability and performance is moving OLED lighting into mainstream applications. The ability to efficiently integrate controls into SSL systems is a significant contributor to energy savings for lighting. In 2016, lighting accounted for 11 percent of energy consumption in the commercial sector, down substantially from 25 percent in 2006, and directly attributable to SSL lighting products combined with controls.1,2
Fig. 1: Pricing, in terms of $/klm, will decrease for OLED solid-state lighting through at least 2025, according to the Department of Energy’s 2014 SSL R&D Manufacturing Roadmap.3 klm = kilolumens or thousands of lumens.
OLED lighting has benefited from the investment in OLED displays, particularly with regard to new materials and supply scale. In addition, OLED awareness has exploded – everyone knows that the latest iPhone (iPhone X) has an OLED display. However, OLED lighting has several performance and cost challenges that are surprisingly more demanding than for displays. These challenges range from higher luminance levels (8× to 20× that of information displays) to longer lifetime requirements (10 years) and markedly different cost points. It is difficult to imagine people spending $110 on a 4-in. OLED light the way they do for the display on an iPhone.4
Displays operate primarily in video mode with subpixels on the micron range; a missing subpixel due to a short is generally not detected by the human eye. For lighting, a short will cause a large, noticeable dark spot and may ultimately cause the entire light panel, a single large pixel, to fail. The reliability demands are not just for hard fails; lighting panels are usually used in clusters and must accurately match on white color point when installed and as they age. These challenges are rarely constraints for displays.
Industry Overview<
OLED Light-Panel Manufacturers: A summary of the primary participants in the OLED panel-production industry appears in Fig. 2. This snapshot captures several strategic elements from the past two years. In 2015, New York-based OLEDWorks (the author’s company) acquired Philips’ key OLED assets, effectively merging expertise from Philips and the Eastman Kodak company while establishing complementary manufacturing in two regions. That same year, LG OLED lighting was acquired by LG Display from LG Chem. This was followed shortly by an announcement that LG lighting panels would be mass produced on fifth-generation manufacturing technology. Earlier in 2017, Konica Minolta, which had been focusing on solution-based OLED on plastic substrates, announced a new joint venture company with Pioneer. Osram’s singular focus on the automotive market has been rewarded with industry-leading products, beginning with tail lights in the Audi TT.5
Fig. 2: An OLED lighting industry snapshot for white light shows technical advances for six companies.
While lagging LED on efficacy, OLED panels now meet the performance threshold for many applications. OLEDWorks produces panels with high luminance capability, opening the application space for this technology. Even at the high-luminance output, about 3× to 4× that of competitive panels, the panels are low glare and provide a very comfortable and welcoming light experience. LG Display’s catalog features 90 LPW (3,000K) panels in a large variety of shapes.6 Three types of flexible panels with efficacies of 52 to 55 LPW are included in the catalog of products as well. Cost-effective flexible lighting panels with high performance will be critical for differentiating OLED from LED and further acceleration of the OLED lighting market.
Lighting Market Segments: The OLED light panel, with its simplicity of integration, blurs the line between light engine and fixture. This duality is reflected in the broad range of applications. With 24V DC wiring, the panels can be mounted directly onto ceilings, walls, and shelving (Fig. 3). With their low profile, the panels are almost flush to the surface, while simultaneously not requiring a deep plenum for hiding heat sinks or other packaging required by LEDs.
Fig. 3: OLED panels can serve as slim and flexible building materials.
Architectural and large-scale projects were among the initial applications for OLED. When first commercially viable, OLEDs were still limited in light output but commanded a premium. However, the beauty of the light quality positioned OLED to make a statement and to create a unique ambience.
Astron-Fiamm, a Swiss lighting company, sells its Paris-based Blackbody I.RAIN platform in both commercial and residential markets, with products that create a wash of soft light. In Europe, grand installations by iart (a Swiss company that specializes in lighting and media architecture) and the German industrial firm Hatec (Fig. 4) use the brighter OLEDs from OLEDWorks. Generally, these installations feature programmable patterns that create movement and are designed to invite people into a space.
Fig. 4: An OLED installation by Hatec can be seen on Neue Mainzer Strasse in Frankfurt, Germany. Image courtesy Hatec.
With increasing panel performance and declining costs, OLED has gained traction in more traditional general lighting applications. Fixtures range from single-panel desk lamps and sconces to multi-panel suspensions with utility in residential, commercial, retail, and hospitality settings. High-luminance panels break the paradigm that OLED soft lighting is also dim lighting – users see the light as soft, yet bright and functional. A comprehensive study of high-luminance OLED in a commercial application was completed by the US Department of Energy (DOE). This study will be discussed later.
The transportation industry, including automotive, aero, and railroad segments, is exploring how the combination of extreme light weight, thin profile, and light uniformity can provide benefits. This includes interior as well as exterior (tail lights, etc.) lighting. At InnoTrans, a European international transportation trade show, architect and designer Andreas Vogler recently debuted a passenger railroad car design, AeroLiner3000 (Fig. 5).7
Fig. 5: This interior for an AeroLiner3000 railroad car features OLED lighting in a design by Andreas Vogler. Image courtesy A. Vogler.
Design Differentiation
OLEDs eliminate many components essential for other lighting technologies. Heat sinks are not needed, yet the OLED remains relatively cool to the touch (due primarily to the very large relative surface area of the emitter). Light output is full spectrum and uniform without light guiding, mixing, diffusing, or reflecting. With little to no glare, OLEDs do not require shades or a way to hide the panel – the light source can be embraced in direct view.
Efficiency: The efficiency of OLED light panels continues to improve, with new products at 80 and 90 LPW entering the market. Over 100 LPW is within sight, just a few years down the road.
These gains are achieved through progress made with OLED materials and device formulation. The increased efficiency is also realized through novel technology for light extraction, reducing the loss of light trapped in the system. Harvesting the light generated into usable light lifts panel efficiency on the order of 40 percent or more. The light-extraction technology also manages the wavelength consistency as measured off angle from normal. It is important to ensure that the light trapped does not result in poor color uniformity.
When designing a space with OLED lighting panels, application efficiency can make OLED solutions very competitive. Application efficiency deploys design elements that allow the light to be close to users and more intimate with the space being lit so that the light falls where it is wanted. The direct-view nature of OLED allows, even promotes, designs with high efficiency. They don’t require designers to keep hot elements from users, or to hide large, bulky heat sinks, or to keep a light source remote due to glare. Application efficiency analysis has been reported by Acuity Brands Lighting suggesting that OLED solutions can be even more efficient than LED.8
Thin and Cool: The thin profile of the OLED is certainly eye-catching. The fact that it can remain thin, without the baggage of heat sinks, encourages creative thinking. Moreover, the low temperature of OLEDs, which is less than 40C even at high luminance levels, creates a canvas for a broad swath of materials ranging from wood to textiles to plastics. Marrying light with unique materials enriches the brand opportunity for many designers as well as the experience of the end user.
Drivers and Power: OLED driver-panel simplicity does have some design challenges. In many cases, the driver needs to be small, not adding bulk to an otherwise streamlined presentation. LED drivers are not typically designed for the low-current demand of OLEDs – 100 mA to 300 mA is common – and therefore tend to be inefficient contributors, often cutting efficiency as much as 30 percent. Also, LED drivers do not have short-circuit protection, which shuts off power should an electrical short be detected in the OLED. Both limitations are overcome by using drivers specifically designed for OLEDs; efficiency >90 percent is available.
OLEDs are low-voltage (DC) components, either 12 VDC or 24 VDC. Low voltage allows for several options for integration into a structure. One option that is growing in popularity is having the AC/DC power conversion done remotely and running 24 VDC cables to the fixtures, usually with integrated drivers. This is an inexpensive and safe way to power the OLEDs. Other solutions include using direct-to-wall power drivers that convert the AC input to the 24 VDC needed.
Standard dimming controls are used with the OLEDs, including 0 to 10 V protocol and pulse-width modulation (PWM). The former is more common.
When specifying power demands for OLEDs, it is important to note that the device voltage changes with temperature and operating time. As depicted in Fig. 6, over the life of an OLED, there is an increase in voltage that occurs due to aging. So as the voltage naturally increases (at constant current), the overall efficiency is somewhat reduced and fewer lumens are generated. These results are reported by each manufacturer as the L70 lifetime (Fig. 6), with voltage increasing 0.5 V to 1.5 V depending on the panel and usage. At lower temperatures, the panels also show a small voltage increase; this is relevant for applications such as refrigerators.
Fig. 6: Voltage rises with aging.9
Well-Being: White OLEDs are broad spectrum lights. They emit the wavelengths required and as determined by the choice of OLED emitters. Unlike LEDs, OLEDs do not need phosphor coatings – wavelengths are not down-converted through phosphors to try to capture a wider color gamut.
The DOE’s Pacific Northwest National Laboratory (PNNL) has published a new way to look at the color rendering of light sources.10 This tool, TM-30-15, depicts a more complete color space and does not rely on discrete color patches as used in the standard Color Rendering Index (CRI). The TM-30 is useful for seeing how well a light source captures colors between the CRI reference patches. Not all CRI > 90 light sources will do more than recreate the color of the reference patches, losing color fidelity where not typically measured. Figure 7 shows the TM-30-15 output for the OLEDWorks Lumiblade Brite 2 panel, with CRI > 90.
Fig. 7: The TM-30-15 OLEDWorks Brite 2 3,000 K is a warm white OLED. Above is a sample TM-30 analysis that shows the color properties of the source vs. the reference for the 3,000 K white point. The overlapping of the source and reference clearly shows where the reference is saturated or desaturated as compared to the source. Image courtesy OLEDWorks.
The Seoul National Library has adopted LG OLED for table lights, stating that they were taking advantage of spectral output that does not harm the eyes or the skin.11 OLEDs, including the high-luminance panels from OLEDWorks, consistently measure in the exempt, or no-risk, category for IES 62471 testing on photobiological risks. Combined with excellent color rendering and low glare, OLEDs offer significant features for architects and building owners considering occupant well-being as a priority.
Amber OLEDs have a unique niche in the health segment. Because OLEDs are not a phosphor conversion system, there is no need for any blue in the amber spectrum. Therefore, amber provides a light that is not only high efficiency but promotes healthy sleeping patterns and safeguards circadian rhythms.
DOE Gateway Study – OLEDs in Practice
In September 2016, the accounting firm of DeJoy, Knauf & Blood (DKB) relocated its offices in Rochester, New York. The firm had been housed in a 100-year-old building with a 1970s “rabbit warren” cubicle layout with low ceilings and fluorescent T8 lighting. In the new location, DKB wanted a modern office layout with solid-state lighting solutions – a combination of OLED and LED lighting. The OLED fixtures are predominantly in shared spaces with limited natural lighting. The LEDs run across an open work area that is complemented by large windows on three sides.
This space was studied as a DOE Gateway project, with a report authored by Naomi Miller of PNNL.12 Gateway studies are a third-party, nonbiased activity in which the lighting quality, performance, and overall experience are reported. The DOE has issued numerous LED Gateway reports to educate end users, decision makers, municipalities, and others about new lighting technology and progress. The DOE does not pay for any of the fixtures or installations. It only reports on the implementation experience.
The DKB site is the second Gateway OLED study and considerably larger in scale than its predecessor. All lighting fixtures used at DKB are commercially available. The report concludes very favorably on the OLED experience, both quantitatively and qualitatively. Quantitatively, the OLED fixtures ranged from 27 LPW to 80 LPW. The former has the first generation of Lumiblade Brite panels combined with a low-efficiency driver solution – it is a very elegant fixture. The latter is from Acuity Brands and combines the higher performing second-generation Lumiblade Brite 2 panels for down lighting, with LED up lighting in a hybrid package. Selected commercially available fixtures are shown in Fig. 8.
Fig. 8: Lighting technology from Visa Lighting Petal, Acuity Brands Olessence, and Amber Marker was used in the DKB installation. Image courtesy DeJoy, Knauf & Blood, LLP.
Other products used extensively in the DKB site include the Visa Lighting Petal and Limit suspension fixtures, as well as Acuity Brands’ Lighting Trilia. The OLED panels operate between 5500 cd/m2 and 8300 cd/m2, which is significantly higher than the standard OLED panels previously available with a maximum output of 3000 cd/m2. At high luminance, a concern was glare. However, the study concluded that glare was not a factor for the OLEDs but did continue to be an issue for the LED downlights used in the DKB space.
Amber lighting is uniquely featured in the “mother’s room” at DKB. Although LED downlights are also available, occupants use only the amber to avoid glare and discomfort. It has been reported that people with migraines also use this room to relax and manage their condition. Since the Gateway report was released, DKB has replaced one hallway of LED downlights with surface-mount OLED tiles to eliminate glare in that space.
The Spread of OLED Lighting
OLED lighting has made great progress in a short amount of time and is now a viable solution for illuminating spaces. Its low glare, natural diffusion, and high light quality allow for an excellent user experience. As costs continue to drop and performance continues to rise, OLED’s unique properties will increasingly illuminate your space.
References
1US Energy Information Administration, https://www.eia.gov/tools/faqs/faq.php?id=99&t=3
2National Academy of Sciences, National Academy of Engineering, and National Research Council. 2010. Real Prospects for Energy Efficiency in the United States. Chapter 2: Energy efficiency in residential and commercial buildings. Washington, DC: The National Academies Press. https://doi.org/10.17226/12621.
3US Department of Energy. Manufacturing roadmap, Solid State Lighting Research and Development, 2014. Prepared by Bardsley consulting, Navigant consulting, SB consulting and SSLS Inc., https://www1.eere.energy.gov/buildings/publications/pdfs/ssl/ssl_mfg_roadmap_aug2014.pdf
4M. Gurman, “Apple’s iPhone X parts cost $115 more than iPhone 8, IHS says,” https://www.bloomberg.com/news/articles/2017-11-08/apple-s-iphone-x-parts-cost-115-more-than-iphone-8-ihs-says
5https://www.osram.com/am/services/news/oled-technology-in-the-new-audi-tt-rs/index.jsp
6LG OLED Light, http://www.lgoledlight.com/portfolio_page/100x100mm/
7A. Vogler, J. Winter, Aeroliner 3000, a double-deck train concept for the British loading gauge, Modern Railways, p. 48–51, 2017.
8Jeannine Fisher, Peter Ngai, and Min-Hao Michael Lu, “Application Efficiency of Indoor OLED Lighting,” International Display Manufacturing Conference, Paper S 23-01, Taipei, Taiwan, Apr 18–21, 2011.
9https://www.osram-oled.com/knowledge/05-microsite-oled-knowledge/index.jsp
10IES Technical Memorandum (TM) 30-15: IES Method for evaluating light source color rendition, https://www.techstreet.com/ies/standards/ies-tm-30-15?product_id=1900892
11https://www.prnewswire.com/news-releases/lg-chem-leads-worlds-biggest-building-installation-of-oled-lighting-at-snu-300031318.html
12PNNL, OLED Lighting in the offices of DeJoy, Knauf & Blood (DKB), LLP. July 2017, https://energy.gov/sites/prod/files/2017/08/f35/2017_gateway_dkb-oled.pdf •
Giana Phelan is currently director of business development at OLEDWorks LLC, an OLED lighting technology and manufacturing company, where she leverages her extensive experience in microelectronic systems, collaborating with luminaire designers, furniture makers, automobile manufacturers, contractors, and architects, to accelerate OLED lighting adoption. She can be reached at GPhelan@oledworks.com