Organic Light Emitting Diode (“OLED”) lighting panels are thin planar area light sources that are naturally diffuse, low glare, high color rendering, cool to the touch, highly energy efficient and highly controllable. Together with LED light sources, they compose the solid state lighting technologies that are replacing over 100 years of bulb and tube lighting technologies, just as solid state electronics have replaced the bulbs and tubes used in electronic devices such as radios, computers and displays.
OLED-Info reported in May 20151 that “UBI Research says that while LEDs are currently the most prominent next-gen lighting devices, OLED panel shipments will grow quickly in coming years, and they see the market growing from around $100 million in 2016 to over $2.7 billion in 2020”. As a naturally diffuse area light source OLED general lighting applications will include architectural, commercial and healthcare lighting as well as residential and consumer lighting. In addition, its unique form factor of extreme thinness and lightness will enable applications in adjacent markets, such as transportation, furniture, appliances, wearables, and more. All of these solutions are embracing the unique pure light quality — the first attribute that grabs a designer’s attention and respect.
Commercially available white OLED lighting panels currently deliver 45-85 lm/W with lifetimes of 30,000-50,000 hr and color rendering indices over 85%. Colored OLED lighting panels, such as red or amber, are also highly efficient and long-lived and are being adopted in the automotive and healthcare industries. The efficiency and lifetime of OLED lighting panels continues to improve rapidly with laboratory reported results in the 100-140 lm/W range and CRIs over 95%2. It is predicted that the ultimate delivered efficiency from OLED luminaires will approach 160 lm/W2.
Today’s highest performing OLED lighting panels are manufactured by coating thin transparent substrates (currently predominantly thin rigid glass less than 1mm thick) with a transparent conductor (typically the anode) followed by vacuum evaporation of multiple functional carbon-based organic layers and finally vacuum deposition of a reflective metal cathode. Additional manufacturing steps include encapsulation of the OLED to protect it from moisture, internal and/or external light extraction layers to reduce light trapped inside the OLED and increase efficiency, and attachment of electrical connectors to the anode and cathode. The electrical connectors are typically 2 wires with or without a commercially available connector. The final OLED lighting panel is nominally less than 2mm thick with active layers less than 1 micron thick.
OLED lighting panels coated on ultrathin flexible glass (less than 150 microns thick) or barrier coated plastic are just entering the market and enable applications using bent and/or flexible OLED lighting panels. Cost of these flexible panels is still very high and reliability is challenging. But like the LED before and the OLED of today, flexible OLEDs will open new markets as technology improves and volumes grow, and the cost of these panels decreases while performance increases.
OLEDs function the same as LEDs. They are diodes that convert electrons to photons directly in the solid state with extremely high efficiency. Like LEDs, OLED lighting panels are direct current (DC) driven devices. Operating voltages typically range from 3V to 20V and current levels are typically less than 400 mA for overall power consumption ranging from less than 1W to about 8W.
In an OLED the current used to inject the electrons is applied over the entire area of the OLED and the light generated from those electrons is, therefore, produced over the entire area of the OLED. In this way OLEDs are the analog of solar cells which absorb light over the entire area of the solar cell and generate a current over that entire surface area. This surface area light generation in OLEDs makes OLEDs the world’s first true area light source and eliminates the need for the heavy and bulky heat sinks found in LED light engines. In addition this naturally diffuse light generation also eliminates the need for the optical elements, shades and/or indirect light reflection constructions required in most LED luminaires, making OLED luminaire product design cycle faster, easier and less complex. The resulting luminaires are extremely light and elegant.
Despite the availability of high quality, high performance OLED lighting panels, the market adoption of these panels has been fairly slow. Some reasons for this slow market growth rate include LED fatigue, design paradigm shift, technical challenges, and cost.
Prior to LED lighting, luminaire manufacturers were not responsible for providing the light engine as part of their product. The luminaire manufacturers made the fixture typically using metal, glass and plastic and used standardized sockets, ballasts, cords, switches, dimmers and plugs to provide the final customer with the means to install the light source themselves. The beauty of the luminaire was in the fixture, and the light source was meant to be hidden from view to avoid glare. The luminaire manufacturer was primarily an expert in design, metal fabrication and optics, and the supply and sales channels were well developed.
With the switch from short lived incandescent and fluorescent light sources to long lived LED light engines, the luminaire manufacturer’s responsibilities changed significantly. Now the luminaire manufacturer must also be an expert in electrical engineering, heat management, drivers, waveguides, and color science. The supply chains have also changed dramatically, and the rapid improvements in LED light sources means constant change for the luminaire manufacturer. This environment makes it difficult to find luminaire manufacturers who have the bandwidth to also add OLED luminaires to their portfolios. Despite this challenge, the OLED market is beginning to show growth as leading edge luminaire manufacturers and lighting designers see OLED as a way to differentiate themselves from the masses of LED fixture designers and take advantage of the faster design cycle and shorter supply chain.
Another obstacle to OLED adoption is the significant design paradigm shift that results from moving from extremely high brightness, concentrated point and line light sources like bulbs, tubes and LED light engines that must be hidden behind shades or optics or reflected off diffuse surfaces while hidden from direct view, to the diffuse area light source of OLEDs. With point sources, shades were a necessity and designers learned how to manage the high intensity concentrated light to create diffuse lighting fixtures or fixtures that used few light sources with multiple reflections to create fixtures with less concentrated glare-producing points of light. The techniques to manage and redirect LED light result in efficiency losses.
With OLED lighting panels the shade becomes obsolete as hiding the lighting panel negates the natural diffuse beauty of the light. Luminaires with many visible OLED lighting panels are preferred as they generate a beautiful diffuse high-color rendering space. This design approach eliminates the losses that are seen in LED or traditional fixtures; the overall efficiency is based simply on the OLED and the driver.
Technical challenges have also hindered the growth of the OLED luminaire market. The efficacy, size, color rendering index, and reliability of OLED lighting panels continues to improve and surpass the requirements for many applications. Beyond performance, the system architecture is evolving including low cost OLEDspecific drivers and building installation control of OLED luminaires. These solutions lag LED due simply to the size of the LED portfolio of products compared to OLED. These technical challenges will diminish over time, but currently they add to the resistance in market adoption.
Perhaps the biggest challenge to OLED market growth is cost. Like any new technology, cost is relatively high while the volumes remain small. Current OLED panels are estimated to be selling at over $100/klm. Cost projections over the next 5 years predict significant reductions in the $/klm for OLED lighting panels, with some of this reduction coming from volume growth, some from improvements in manufacturing and some from development of lower cost alternatives in the products and processes.
The Department of Energy predicts OLED panel costs will reach $10/klm by 20253. It is very important, however, to understand that $/klm is not the only measure of cost. It is not just the number of lumens but also how the lumens are used. In addition, the total cost of the luminaire includes heat sinks, optics, and product development time and costs. With OLED panels all of these costs are significantly lower. In addition, the low heat density of the OLED fixture allows for using less light closer to the user, increasing the use efficiency of the light. This, too, can result in lower total cost.
- OLED-Info website: http://www.oledinfo.com/ubi-sees-25-billion-oledl-ighting-market-2020-oled-lighting-may-eventually-get-cheaper-leds, May 15, 2015.
- U.S. Department of Energy, “Solid-State Lighting R&D Plan, May 2015.
- Lumiblade OLED Lighting, Lumiblade Insider, Issue 01/2015
- U.S. Department of Energy, “Manufacturing Roadmap: Solid State Lighting Research and Development, August 2014.