Light Bulbs Flattened Into Light Foil

Light bulbs will soon be obsolete, replaced by thin, flexible sheets of organic light-emitting diodes (OLEDs) used for everything from lighting tiles and strips in homes and offices to windows that can simulate sunrise and sunset.

In the November, 2011 edition of Physics World, Paul Blom and Ton van Mol of the Holst Centre in Eindhoven, The Netherlands report that they have developed a way of creating OLEDs using a cheap, newspaper-style "roll-to-roll" printing process.

Blom and Van Mol believe that cost-effective, flexible OLEDs for lighting and signage can be made using the roll-to-roll production process.

Unlike the "inorganic" LEDs currently used in display signs, traffic lights and car indicators, OLEDs can be dissolved in a solvent and sprayed onto a roll of thin, flexible, plastic foil.

The bottom layer of an OLED, which acts as a support, is a flexible material such as a polymer foil that has the electrodes and the light-emitting layer sandwiched on top to make up the complete device. Each layer is between 5 and 200 nanometres thick.

Despite their high efficiency, traditional LEDs have not been a viable alternative to light bulbs because they have to be fabricated in clean rooms and are expensive to make. The spray-on production of OLEDs, on the other hand, makes it possible to produce them en mass. And with about 20 per cent of world electricity consumption spent on lighting, widespread use of OLEDs could greatly reduce global energy consumption.

There are, however, several hurdles that need to be overcome before OLEDs become a commercial commodity, such as depositing the materials onto a thin film sheet with high precision, managing the properties of the different materials and, most importantly, keeping water out of the device – OLEDs have a barrier requirement up to a thousand times more demanding that food packaging.

The first real-world use of OLED on flexible foil occurred at the Le Mans 2010, in which the ORECA01 car from French racing team Oreca was equipped with rear view mirrors with an integrated thin film encapsulated Flexible Organic Light Emitting Diode (OLED) on the back.

With dozens of high-profile venture groups pursuing general illumination applications for OLEDs, the future of the incandescent bulb appears dim.

Holst Centre
Physics World