Fraunhofer FEP presents OLEDs applied to paper-thin stainless steel
The Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP (Dresden, Germany) will be presenting OLEDs on gauzy stainless steel foil during AIMCAL 2017 in Tampa, Florida from 15-18 October. The novel application was developed in cooperation with Nippon Steel & Sumikin Materials Co., Ltd. (NSMAT) and Nippon Steel & Sumitomo Metal Corporation (NSSMC).
Stainless steel is normally associated with kitchenware and chemical plant pipe. However, stainless steel foil has also been utilised for several years in thin-film photovoltaics and batteries. Now stainless steel can also serve as a substrate for flexible electronic components. In comparison to the conventional substrate materials like glass or plastic web the material possesses special properties for this purpose and is well-suited as a substrate for organic light-emitting diodes (OLEDs), for example. Thanks to the planarisation layer developed by NSSMC as well as the comparatively good thermal conductivity of stainless steel, homogenous large-area lighting surfaces with current densities of more than 10 mA/cm² have become better applicable.
Moreover, OLEDs need to be protected from water vapour and oxygen in order that the organic layers remain fully functional. Stainless steel provides excellent barrier properties against environmental influences and is therefore suitable as a substrate for OLEDs from this standpoint as well.
Jun Nakatsuka, manager of business development at NSMAT, is looking to the future: “Thanks to the smoothness and high thermal conductivity of the stainless steel foil we obtain extremely homogenous OLED light. We see OLEDs on stainless steel in perhaps three years from now being used in automobiles as turn indicator and back-up lights, as cladding for fascia, and as advertising displays.”
There is some ways to go before reaching that juncture. Following the expensive development of stainless steel foil, it still needs to be made suitable for production purposes. Fraunhofer FEP has at its disposal roll-to-roll processing lines for manufacturing OLEDs on flexible materials and an OLED process that has high reproducibility. This is what has made possible the development of stainless steel foil with a clean and smooth planarisation layer.
Michael Stanel, project manager within the R2R Organic Technology department at Fraunhofer FEP explains: “In addition to machinery design and construction, we also possess comprehensive know-how in handling sensitive substrates. To be certain the stainless steel is suitable for the nanometre-thick organic layers, an R2R-compatible smoothing planarisation layer was developed that is easy to integrate into the process.”
It was also important during the collaboration with NSMAT and NSSMC to work out quality standards for the future OLED fabrication. In particular, the surface properties of the substrate were specified and are being continuously improved in cooperation with NSMAT and NSSMC.
Caption: OLEDs applied to paper-thin stainless steel (photo: Fraunhofer FEP)