A roll-to-roll production technique, similar to the way newspapers are printed, could offer a future of cheap, flexible solar cells and LED lighting panels. The breakthrough, the result of three years of research, is now “ready to market”, according to the project participants.
The Treasores project was led by scientist Frank Nüesch from Empa, the Swiss federal laboratories for material science and technology, with the combined expertise of nine commercial companies and six research institutes in five countries.
Treasores (an acronym for Transparent Electrodes for Large Area Large Scale Production of Organic Optoelectronic Devices) began in November 2012 with the aim of developing technologies to reduce the production cost of organic electronic devices such as solar cells and LED lighting. The project was funded with 9 million euros ($10.2 million) from the European Commission and an additional 6 million euros ($6.8 million) from the project partners.
The research has yielded seven patent applications, papers in a dozen peer-reviewed journals and provided inputs to international standards organizations.
The project has developed and scaled-up production processes for several new transparent electrode and barrier materials for use in the next generation of flexible electronics.
Already under commercial production – or due for production this year – are electrodes-on-flexible substrates that use either carbon nanotubes, metal fibers or thin silver. The new electrodes have been tested with several types of optoelectronic devices using rolls of over 100 meters in length.
The roll of OLED light sources pictured, showing the project logo, was made using roll-to-roll techniques at Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology (Fraunhofer FEP) in Germany on a thin silver electrode developed within the project by the German firm Rowo Coating.
The electrodes on the new films are technically at least as good as those currently made from indium tin oxide (ITO) but will be cheaper to manufacture and will not require the importation of indium.
Fraunhofer FEP's Tomasz Wanski said that the new electrodes create an OLED light source that is very homogenous over a large area, achieving an efficiency of 25 lumens per watt. This level of efficiency is as good as the much slower sheet-to-sheet production process for equivalent devices.
New test methods developed by the United Kingdom's National Physical Laboratory, in the course of the project, made sure that the electrodes would still work after being repeatedly bent – a test that may become standard in the field.
A further outcome of the project has been the development, testing and production scale-up of new approaches to transparent barrier foils (plastic layers that prevent oxygen and water vapor from reaching the sensitive organic electronic devices).
High performance low-cost barriers were produced by the Swiss company Amcor Flexibles Kreuzlingen and it is expected that the company will adopt this technology after further development. Such high performance barriers are essential to achieve the long device lifetimes that are necessary for commercial success.
U.K.-based solar power firm, Eight19, was one of the project's technology partners. Michael Niggeman, Eight19's chief technology officer, said: “The Treasores project was a success for Eight19 as it made a significant contribution to the reduction in manufacturing cost of Eight19's plastic solar cells.
“This was achieved through the customized development and up-scaling of low-cost barriers and electrodes in the project consortium. It is an essential step towards the commercialization of Eight19's organic photovoltaics based on technology developed and produced in Europe.”
