Organic is a term more often associated with vegetables than lighting systems, but some LED manufacturers are now incorporating organic molecules into their products to meet specific application demands. The result is a new type of LED system that provides a broad illumination area and extraordinary color rendering.
Mainstream availability of organic LED (or OLED) systems for commercial and industrial lighting became a reality in late 2011, kicking off first in Japan and then in North America. The primary advantage of OLEDs over traditional LEDs is soft, diffuse lighting that does not throw shadows. In other words, OLEDs are not point light sources but instead are ideal for evenly illuminating objects and spaces.
How An OLED Works
The use of the word “organic” is not a marketing ploy intended to represent the product’s environmentally friendly properties. The light-emitting substance in the LED is, in fact, an organic semiconductor. A cathode is attached to the back of the semiconductor and an anode to the front. An electric current then excites the electrons in the semiconductor into higher energy states. As the electrons return to their ground state, this excess energy is converted to light. The light is projected through the anode and a glass (or plastic) substrate, creating a surface light source that is remarkably thin, highly efficient, and not a significant source of heat.
Light emission by organic compounds was first observed in the early 1950s and incorporated into a light emitting diode in the mid-1980s. Since then, a variety of manufacturers have introduced OLED televisions, smartphone and PDA screens, handheld game consoles, and other display devices.
The primary drawbacks of these OLED products has been a sensitivity to water and a highly reflective surface that works much better in a dark room than outside in sunlight. Naturally, these disadvantages do not apply to indoor lighting applications in a dry environment. However, the manufacturing of energy-efficient white OLED modules for solidstate lighting applications has only recently become cost effective.
OLED In Lighting Systems
An OLED module is typically comprised of two components: an OLED panel and a base unit. The organic light emitting diode described above is part of the OLED panel, which is typically enclosed in a plastic casing to protect it from mechanical stress. The panel is then attached to the base unit, most often with a mechanism that allows easy removal and replacement.
The base unit serves two functions. First, it holds the OLED panel in place. Second, it contains a voltage/current regulator to power the panel. The number of modules per power supply depends on the wattage. Check products for specifications. Note: Because input current and power requirements will increase with operating time (to compensate for lumen depreciation), initial and maximum values should be provided.
A complete OLED module is typically less than 10mm in height and provides a diffuse, uniform white light across the light emitting surface. Arranged together, they can create an entire wall of light without generating significant heat. Always check the product’s minimum spacing requirement to ensure the OLED panel can be removed from the base unit for replacement.
Some products will start flickering to indicate the end of useful operating life (a common panel life is about 10,000 hours). In such a case, the flicker will be eliminated by replacing the OLED panel within the module. Power should be disconnected from the base unit before removing the OLED panel; however, most base units are designed to self-protect by shutting down if the panel is removed while power is on.
Best Practices In Fixture Design
OLED modules provide previously unimagined flexibility in fixture design. Ultra-thin and adjustably bright, these modules provide fixture manufacturers with very few aesthetic limitations. This allows the application to determine the best form, not the technology. The most important technical limitations to consider are temperature and heat dissipation— both of which can have a significant effect on panel life, light output, and electrical interface.
OLED modules are intended for use in luminaires in dry, indoor locations with an ambient temperature near the fixture in the general range of 5° to 35°C (41° to 95°F). There will also be limits for the temperature at dead center on the bottom of the base unit and dead center of the exposed surface of the OLED panel. In general, relative humidity should remain below 85 percent. Higher temperatures and/or humidity will accelerate lumen depreciation and may cause premature device failure. Individual products may vary from the above figures, so it’s always wise to check product specifications.
In most product designs, the base unit enables the OLED module to work with 0-10V Class 2 control devices, and some products allow for other control technologies as well. An OLED module can commonly be dimmed from full brightness to as low as three percent. In addition, OLED fixtures can often be individually “tuned” to the ideal light level during installation to ensure the fixture isn’t drawing more power than is needed (i.e., over-lighting) for the application.
Since OLED models do not produce significant heat, even in great numbers, fixtures can be situated touchably close to the end users. They can even be incorporated into walls and/or furniture. (Flexible OLEDs are even being used in clothing, to give you an idea of just how close they can be to human contact.)
Advantages & Disadvantages
As you might expect, OLED fixtures share a number of advantages with traditional LED fixtures, including low energy operation and extended lifespan. For example, in March 2012 the bustling Jiyugaoka Rail Station in Tokyo installed a mix of LED and OLED fixtures to reduce the power needs of its lighting system by 40 percent.
However, a common complaint about traditional LED fixtures is that reflectors do not adequately transform the point light sources into a diffuse illumination. Even if a light meter under an LED fixture proves that you’re achieving the desired foot-candles, uneven lighting may result in dark spots between fixtures. OLED panels provide diffuse illumination without the need for reflectors in the fixture.
In addition, OLED fixtures provide a very high level of color rendering. With color consistency commonly rated at <3.5 SDCM and a Color Rating Index (CRI) of >90, OLED fixtures can meet the needs of the most demanding applications, such as museums and galleries.
These luminaires also produce minimal UV and infrared rays, which can fade colors and otherwise damage light-sensitive materials. For both color rendering and protection of priceless artwork, the National Museum of Modern Art in Kyoto, Japan, requested a prototype OLED lighting system be installed by mid-2011 in time for a weaving exhibit that featured resplendent — but highly delicate — colors and materials.
The primary disadvantage of OLED lighting, as with most technologies when they are new to market, is price. At this point in time, the energy savings achieved by OLED fixtures are generally only cost effective if the other positive properties of OLED technology — the thinness of the panel, comfort at close range, superior color rendering, etc. — are also required to meet the specific needs of the application.
To see the future of OLED lighting systems in North America, simply look to Japan. Museums, with their uncompromising need for color consistency and non-harmful lighting, are among the earliest adopters and likely to be the most eager customers in the U.S. and Canada, as well. In addition, OLED fixtures will likely be incorporated into specific areas of larger retrofit projects, especially projects involving LED lighting systems, when close lighting is required.
Looking further into the future, fixture manufacturers will develop new niche designs that take advantage of the size and flexibility of OLED panels to make the best use of space in a wide variety of applications, including office and retail facilities. OLED fixtures will allow lighting designers to place small fixtures only where they’re needed, reducing energy waste.
As with most advances in lighting technology today, OLED fixtures allow for human intelligence and ingenuity to play a greater role in the design process. Engineers and lighting professionals are empowered to fine-tune their designs for specific applications rather than painting with a broad brush. With a “right tool for the right job” mentality, these fixtures are ideal for improving functionality and energy efficiency within a larger lighting design.
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