High efficiency organic LEDs

Chemical group Solvay and the Holst Centre have demonstrated high efficiency flexible organic light emitting diodes (OLED) lighting tiles with a surface area of 69 cm². These large area demonstrators contain several layers deposited by solution processing at the Holst Centre and additional layers applied by conventional vacuum deposition at Solvay.

OLEDs enable flat diffuse lighting sources and are complementary to inorganic LEDs, which are suitable as spotlights. Current OLED devices are made at pilot scale by depositing many layers on glass by vacuum process.

The two organisations deposited several layers of the OLED by solution processing bringing the use of printing technologies, to produce OLEDs, closer.

Use of printing on flexible substrates will enable large scale manufacturing of OLEDs for general lighting and will bring some additional features: thin, flexible, and potentially transparent light sources that could be integrated in ceilings, walls and windows.

The flexible OLED stack was designed and optimised at Solvay. It is based almost entirely on organic functional materials, developed by the company, and integrates Plexcore OC hole injector layer (HIL) from Plextronics, Inc.

The demonstrators include Holst’s thin-film encapsulation and large area transparent anode technologies on plastic substrates from DuPont Teijin Films.

The large area, flexible, white OLEDs have been characterised 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 common incandescent bulbs.

This measured value is on par with results measured on small (7 mm²) equivalent devices made at Solvay on glass substrates, indicating that the device architecture and the materials set used in these demonstrators translate well from small-scale, rigid substrates to large area, flexible plastic substrates.