Stainless steel is normally associated with kitchenware and chemical Plant pipe. However, stainless-steel foil has also been used 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 planarization 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 vapor 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 planarization 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 nanometer-thick organic layers, an R2R-compatible smoothing planarization layer was developed that is easy to integrate into the process.”