A recent report compiled by the U.S. Department of Energy (DOE) indicates that progress is being made in the OLED field and, even though there are currently some products on the market, the OLED technology still has a pretty steep development curve to overcome in order to meet the product goals of OLED luminaires. Included in those goals are; longer life, higher efficacy, more and better color quality options and greater CCT options, better lumen maintenance over periods of time, drivers of higher efficiency, greater durability in high temperature and high humidity environments and in rough handling during installation and shipping. As the proposed development path continues, this solid-state lighting technology (SSL) will do as the LED technology has done and is doing, and will become a trusted and accepted product in the marketplace. In fact, at this point in time, even the DOE admits that the field is advancing at such a pace that the current state of the technology may be beyond test results spoken of in the report. However, the report accurately depicts the performance of the particular products at the time of testing. The test products were only tested and compared with other similar products available during the same period of time. The report does not specifically set forth any product recommendations or application suitability claims for any particular product or manufacturer. Instead it seeks to make performance comparisons to benchmark metrics and examine market trends. Since OLEDs emit light in a soft overall glow, instead of a point source light as LEDs exhibit, and even though they both are SSL technology, there are not yet fully standardized testing protocols for determining numerous metrics of OLED luminaries. The standard design of being produced in panel arrangements and the overall even light output does not have another technology to directly compare with so there are no directly comparable benchmarks.
The OLED products used in these series of tests, when compared to LED sources, exhibited an overall lower efficacy. The results from the tests indicate the range was between 23 lm/W and 45 lm/W. The panel manufacturer’s information indicated that the ranges were between 42 lm/W and 55 lm/W. It was determined that the lower efficacy performance was due to the inefficiency of the selections and combinations of transformers and drivers used. The efficacy ratings will improve in the near future, as driver development is moving at a very rapid pace. Depending on the panel tested, the color quality of the light produced differed. The general CCT of the tested products was in the 2900 K range, although the manufacturer data called out a nominal CCT of 3000K. There was a consistent, comparable, soft distribution of light exhibited by all the test products and the light cast very soft shadows. Moderation of the light produced by the test products was only affected by the physical design of the luminaire hardware itself. One product that was of a multi-panel design was tested in two different orientations – ceiling mounted and wall mounted – and it was found that the efficacy, lumen output, color characteristics, power factor and other metrics were within a 1% variation. Despite some slight differences in published technical data, all test OLED products exhibited parameters which were quite closely to all manufacturers’ technical data listings.
The testing also involved teardown procedures to examine various aspects of construction. There was one panel which was damaged during testing and the subsequent teardown revealed that a slight compromise in the seal of the OLED along one edge of the glass allowed air and moisture to enter and that interacted with the organic layers and discolored the light output. The drivers for all test products were of different design, some using multiple components to accomplish the transformation of the incoming AC power to DC power, and one luminaire using only one component for the transformation. The efficiency of the driver system of a couple of the products ranged from 80% for one task light to a fairly respectable 85% for a large 5-panel OLED luminary. While a couple of lower efficiency driver systems in two tested wall sconces operated at an estimated efficiency of 47-58%. That inefficiency in the drivers is a concern, as the lower the efficiency of the drivers, the lower the system efficacy becomes.
Panels which were subjected to long exposure of elevated ambient temperatures suffered from electrical short failure but in multi-panel luminaries the remaining un-shorted panels continued to operate. Testing indicated the bad panels had a lower impedance and a simple visual inspection showed the presence of a dark spot, indicating the short which had caused the panel to fail. The increased ambient temperatures also causded a higher than expected decay in the light output. At 45° C (113° F), lumen output maintenance averaged only 87% after only 4250 hours of operation.
This is a small thumbnail of some of the test results of the OLED testing supported by the DOE, and just as the current class of LED luminaries had to go through development stumbles and setbacks before becoming the product they are today, the OLED technology will be seeing the same sort of hurdles. However, the lessons learned from the development of today’s LED technology will help usher in the OLED technology in a much more effective way than the LED predecessors.
As always, if you have questions in regard to any of your lighting projects, please feel free to call Polar-Ray at 303-494-5773 to speak with a lighting consultant. Thank you for perusing our web site.