Low-cost, flexible lighting foils for next-gen electronics

Scientists have developed rolls of flexible lighting foils that can be produced much like newspapers are printed, paving the way towards cheaper solar cells, LED panels and next generation of flexible electronics.
The TREASORES project (Transparent Electrodes for Large Area Large Scale Production of Organic Optoelectronic Devices), led by Frank Nuesch of Swiss research institute Empa, aims to dramatically reduce the production costs of organic electronic devices such as solar cells and LED lighting panels.
The project 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 fibres or thin silver are already being produced commercially.
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-generation light sources and solar cells.
The roll of OLED light sources was made using roll-to-roll techniques on a thin silver electrode.

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 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, researchers said.
Tomasz Wanski from the Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology (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.
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 which are essential to achieve the long device lifetimes.
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.