By Anthony Capkun
March 10, 2016 – According to stakeholders, technological breakthroughs in the TREASORES project will lead to cheaper lighting and flexible solar cells.
In November 2012, the Transparent Electrodes for Large Area Large Scale Production of Organic Optoelectronic Devices (TREASORES) project started with the aim of developing technologies to dramatically reduce the production costs of organic electronic devices, such as solar cells and LED lighting panels.
Funded with 9 million Euro from the European Commission and an additional 6 million Euro from project partners, TREASORES has produced seven patent applications, a dozen peer-reviewed publications and provided input to international standards organizations.
Most importantly, they say, 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 optoelectronics.
Three of these electrodes-on-flexible substrates that use either carbon nanotubes, metal fibers or thin silver are either already being produced commercially, or expected to be so as of this year. The new electrodes have been tested with several types of optoelectronic devices using rolls of over 100 metres in length, and found to be especially suitable for next-gen light sources and solar cells.
The roll of OLED light sources with the project logo was made using roll-to-roll techniques at Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP on a thin silver electrode developed within the project by Rowo Coating GmbH. 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), say participants, 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/W—as good as the 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 United Kingdom to ensure the electrodes would continue to work after being bent repeatedly.
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 sensitive organic electronic devices). By combining the production of barriers with electrodes (instead of using two separate plastic substrates), the project has shown production costs can be further reduced and devices made thinner and more flexible.
The main challenge facing the project 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 1% 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.
The TREASORES project united nine companies with six research institutes from five countries and was led by Frank Nuesch from the Swiss Federal Laboratories for Materials Science & Technology (Empa). The partners in the TREASORES project include:
• Empa (Swiss Federal Laboratories for Materials Science and Technology), Switzerland
• Technical University of Dresden, Germany
• Fraunhofer FEP, Fraunhofer ISC, Fraunhofer IVV and Fraunhofer ISE, Germany
• The University of Valencia, Spain
• Aalto University, Finland
• CIC Nanogune, Spain
• NPL Management Ltd., United Kingdom
• Osram GmbH, Germany
• Canatu Oy, Finland
• Amanuensis GmbH, Switzerland
• Sefar AG, Switzerland
• Amcor Flexibles, Switzerland and Germany
• Rowo Coating GmbH, Germany
• Eight19 Ltd., United Kingdom
• Quantis Sarl, Switzerland
— Photos © Fraunhofer FEP