Breakthrough for Cheaper Lighting and Flexible Solar Cells

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Such processing techniques promise to make light sources and solar cells much cheaper in future, but require flexible and transparent electrodes and water impermeable barriers – which have also been developed by the TREASORES project. The electrodes from the project are technically at least as good as those currently used (made from indium tin oxide, ITO) but will be cheaper to manufacture and do not rely on the import of indium. Tomasz Wanski from the Fraunhofer FEP said that because of the new electrodes, the OLED light source was very homogeneous over a large area, achieving an efficiency of 25 lumens per watt - as good as the much slower sheet to sheet production process for equivalent devices. In the course of the project, new test methods were developed by the National Physical Laboratory in the UK to make sure that the electrodes would still work after being repeatedly bent – a test that may become a standard in the field.

Special foils protect from oxygen

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 vapour from reaching the sensitive organic electronic devices). High performance low-cost barriers were produced and it is expected that the Swiss company Amcor Flexibles Kreuzlingen 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 – as confirmed by a life cycle analysis (LCA) completed during the project, solar cells are only economically or ecologically worthwhile if both their efficiency and lifetime are high enough. By combining the production of barriers with electrodes (instead of using two separate plastic substrates), the project has shown that production costs can be further reduced and devices made thinner and more flexible.

The main challenge the project had to face was to make the barrier and electrode foils extremely flat, smooth and clean. Optoelectronic devices have active layers of only a few hundred nanometres (less than one percent of the width of a human hair), and even small surface irregularities or invisibly tiny dust particles can ruin the device yield or lead to uneven illumination and short lifetimes.

Knowhow form 15 partners in five nations combined

The TREASORES project united nine companies with six research institutes from five countries and was led by Frank Nüesch from the Swiss Federal Laboratories for Materials Science and Technology (Empa). ”I am very much looking forward to seeing the first commercial products made using materials from the project in 2016”, says Nüesch.

Michael Niggemann, Chief Technology Officer for Eight19 Ltd in the United Kingdom 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 photovoltaic based on technology developed and produced in Europe.”

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