Smoothing the Way for Flexible OLEDs

Two Fraunhofer Institutes have manufactured a flexible OLED in a roll-to-roll production and encapsulated the device in a subsequent inline-process for the first time. This process design would allow the production in a single plant.

The Fraunhofer Institute for Photonic Microsystems (IPMS) and the Fraunhofer Institute for Electron Beam and Plasma Technology (FEP) assembled flexible, large-area organic light-emitting diodes with barrier layer systems which are necessary for long device lifetimes.

While existing OLEDs convert electricity very efficiently into high quality light, they are costly to manufacture and are mostly deposited on rigid materials like glass. The development of flexible, organic light-emitting diodes, which can be manufactured on an industrial scale, promises economies of scale and accordingly broader marketing of the environmentally sound and highly efficient devices.

The steps were developed in the frame of the project Rollex (roll-to-roll production of highly efficient light-emitting diodes on flexible substrates, support codes 13N8858 and 13N8857), funded by the German federal ministry of education and research (BMBF).

“The successful assembly of an OLED in a roll-to-roll process means a breakthrough on the way to highly efficient and competitive devices,” said Professor Karl Leo, director of the Fraunhofer IPMS. “The achievement of this project proves the capacity of Dresden as a focal point for research in organic electronics.”

A major component of flexible OLEDs is the homogenous encapsulation of luminescent layers with transparent barrier layer systems. Permeation of only small amounts of humidity or oxygen shortens the lifetime of the devices drastically, which explains the strong need for barrier systems protecting the luminescent materials on a large area without defects. However, the barrier layers should not absorb the emitted light and should not interfere with the colors of the light.

The researchers of the Fraunhofer Institutes deposited OLED materials on a cheap aluminum foil in a roll-to-roll pilot plant, further encapsulated the luminescent foil with a barrier layer system, patented by the Fraunhofer FEP, without compromising its luminosity.

“Developing the flexible OLED, experience from both institutes have been united in an optimal way,” said Dr. Christian May, head of the Organic Materials and Systems business unit at the Fraunhofer IPMS. “I am avid that we integrated the effective barrier layer systems developed from the Fraunhofer FEP into the OLED-technology of the Fraunhofer IPMS."

“The coating processes are all done in a roll-to-roll modus with a continuously moved substrate which opens up strong potential to reduce costs,” Dr. Nicolas Schiller, head of the Coating of flexible products business unit at the Fraunhofer FEP

The technology developed by the two Fraunhofer Institutes marks a milestone on the way towards an industrial manufacturing of flexible OLEDs. Besides OLEDs, also other devices, such as organic solar cells or memory systems, could be realized in intermediate terms.

The work is going to be continued by the Dresden Institutes in a bigger consortium.

For more information, visit: www.ipms.fraunhofer.de or www.rollex-projekt.de