OLEDs enable flat diffuse lighting sources and are complementary to inorganic LEDs, which are by nature well suited as spotlights. Current OLED devices are made at pilot scale by depositing many layers on glass by vacuum process. Solvay and Holst Centre were able to deposit several layers of the OLED by solution processing, which brings the use of printing technologies to produce OLEDs closer.
Use of printing technologies on flexible substrates will enable large scale manufacturing of OLEDs for general lighting applications, and will bring some additional features: thin, flexible, and potentially transparent light sources that could be integrated in ceiling, walls, windows and many other innovative application segments.
The highly efficient flexible OLED stack was designed and optimized at Solvay. It is based almost entirely on organic functional materials developed at Solvay and integrates Plexcore OC Hole Injector Layer (HIL) from Plextronics, Inc. The demonstrators include Holst Centre's own thin-film encapsulation and large-area transparent anode technologies on plastic substrates from DuPont Teijin Films.
These large-area, flexible, white OLEDs have been characterized at Philips Research Laboratories and found to have an energy efficiency of 30 lm/W at 1000 cd/m2, which is two to three times higher than incandescent bulbs.
This measured value is on par with results measured on small (7mm2) equivalent devices made at Solvay on glass substrates, indicating that the device architecture and the unique materials set used in these demonstrators translate very well from small scale, rigid substrates to large area, flexible plastic substrates.
Capitalizing on these results, the partners are already working on a second generation of demonstrators encompassing more solution-processed layers. According to Holst Centre, this achievement demonstrates the potential for high efficacy OLEDs on flexible plastic foils, opening ways to a production of low-cost, solution-processed OLED lighting tiles.