Light emitting wallpaper a step closer

Agfa Materials, Philips Research, and Holst Centre, an open-innovation initiative by IMEC (Belgium) and TNO (The Netherlands) demonstrate the world’s first large-area flexible OLED tile that does not require ITO as transparent electrode and has printed shunting lines. The result, partly funded by the EU FP7 Fast2Light project, eliminates costly material and lithography process steps. It is therefore a significant improvement towards low-cost, high volume and large-area manufacturing of flexible OLED lighting.

For OLED lighting to become producible at low cost, simple system design and compatibility with roll-to-roll processing are a must. To achieve low cost, elimination of transparent conductive oxides as the high-conductive and transparent anode layer is the preferred way to go. Up till now, ITO was needed as supporting layer for the PEDOT/PSS* anode layer with lower conductivity. Thanks to Agfa’s high-conductive transparent polymer OrgaconTM, a PEDOT/PSS-based solution with six orders better conductivity than its predecessor, the use of ITO can now be avoided. Proof is the latest OLED lighting demonstrator of Holst Centre’s shared programs: a homogeneous white OLED tile of 12x12cm2 without the use of ITO.

However, to obtain homogeneous light distribution over large surfaces like this, some kind of additional current distribution is still needed. Even in the presence of ITO, a grid of metallic shunting lines is needed. In conventional designs, ITO, shunting lines, and insulation lines covering the shunting lines are patterned using photolithography steps. Holst Centre and its partners have succeeded in direct patterned deposition of these shunting lines by inkjet printing, and combining it with PEDOT/PSS without the need for any photolithography steps. To our knowledge, this is the first time that ITO-free flexible OLEDs are demonstrated in combination with printed shunting lines, which is an important step towards low-cost manufacturing. According to recent reporting, OLED lighting is expected to hit the market already in the course of 2011.

The demonstrator was displayed at the Printed Electronics Conference in Dresden (April 7-8) and the technical details will be presented during the SPIE Optics and Photonics Conference in San Diego (August 2009). The results were obtained thanks to the combined expertise in the Holst Centre program on Flexible Organic Lighting and Signage and in the EU FP7 Fast2Light project. In these programs, Holst Centre researchers collaborate in mixed teams with academics and resident researchers from industrial partners, like Agfa and Philips Research.

* ITO= IndiumTinOxide / PEDOT(/PSS)= Poly(3,4-ethylenedioxythiophene) (/poly(styrenesulfonate))