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Optoelectronics/Displays??

OLEDs facilitate smart textiles development

Posted: 25 Jul 2013 ?? ?Print Version ?Bookmark and Share

Keywords:smart textiles? OLEDs?

The main problem with smart textiles is the difficulty of applying electronic components or organic semiconductors to 3D structures such as fibres in a reproducible way. Material scientists from the Technische Universit?t Darmstadt addressed this challenge by developing a machine with which electronically active materials can be vacuum deposited onto threads.

"We turned to organic light emitting diodes known as OLEDs because they require the highest standards concerning the substrates. Today, we are able to apply functioning OLEDs to a thread and make it glow. Applying other devices such as transistors or solar cells photovoltaics includes other problems, but is comparatively less complex when it comes to the actual coating," said Tobias K?nyves-Toth, who had the idea for the machine as part of the LUMOLED joint project of the Federal Ministry for Education and Research.

A fibre with 500?ms?m glows over five milimeters

Figure 1: A fibre with 500?ms?m glows over five milimeters. Photo by Tobias K?nyves-Toth.

One problem in small molecule fibre coating is that it has to be carried out under vacuum conditions. "With our rotational coating process we have found a possibility to evenly coat the fibre and then being able to remove it from the vacuum without it coming into contact with air, because OLEDs are highly sensitive to oxygen and water," explains K?nyves-Toth.

The components are applied to the thread by heating the materials in the vacuum until they sublime or evaporate. The materials condensate on the fibre in exactly the same way as water does when it is heated on a cooker, rises as steam and condenses on a window. A total of seven layers have to be applied to the fibre, some of them just a few atoms thick. And this is where another problem arises: textile fibres have a rough surface. However, the electronic components only work on a smooth surface; even scratches of just a few nanometres' thickness can cause problems such as short circuiting.


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