CSEM and Sefar develop low-cost technology for large-area OLEDs

The fabric substrate SEFAR TCS Planar

Developing a low-cost, efficient method of increasing the attractiveness of OLEDs for lighting poses a significant challenge. Thanks to a CTI project, the micro- and nanotechnology R&D centre CSEM and Sefar AG (both from Switzerland) have succeeded in designing a promising state-of-the-art way of achieving this aim. This technology is reported to open up new opportunities for applications in residential, professional lighting segments, as well as consumer electronics.

OLEDs have long been deemed to be the lighting technology of the future. However, their market penetration remains minute due to their high production costs and moderate light output compared to, for example, inorganic LEDs. Considerable resources have been applied, unsuccessfully, to overcoming these barriers. Thanks to a project supported by the Swiss Confederation (CTI project), CSEM and Sefar are now able to propose a promising solution featuring interesting production costs, high efficiency, and compatibility with the fabrication of large-area OLEDS.

Together, the partners have developed low-cost, flexible, transparent, highly conductive electrodes made of fabric substrates comprising flexible metallic wires and polymeric fibres woven together in a highly transparent and flexible polymer. These fabric substrates (SEFAR TCS Planar) are manufactured using low-cost, high-throughput processes under standard ambient clean room conditions.

The OLEDs are finalised by coating the substrate with a thin-film (tens of nanometres) layer of a solution-process conductive polymer. The high electrical conductivity of the metal wires in the fabric substrate ensures that the electrode displays high conductivity over large distances, even with an ultra-thin, and hence highly transparent, layer of the conductive polymer.

“The wet deposition of the different ultra-thin OLED layers with excellent thickness uniformity and minimum leakage current was the main challenge faced by CSEM,” explains Rolando Ferrini, head of CSEM’s Integrated Light Management section.

“The use of Sefar fabric-based electrodes significantly simplifies the production of large-area OLEDs by eliminating the evaporation, photolithography, and electrical insulation of the supporting metal tacks,” continues Peter Chabrecek, R&D manager at Sefar. “With this achievement, our company aspires to reach 20% of the flexible transparent electrodes market by 2020 for all types of optoelectronic devices.” The groundbreaking solution can be applied for OLEDs, as well as for many other products, including solar cells, EL devices, touchscreens, electrochromic glasses, transparent heating elements, sensors, photo-detectors, and transparent shielding elements.

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