When polymers conduct electricity

The OLED revolution
OLEDs (Organic Light-Emitting Diodes) have been causing a bit of a buzz in recent years and have set lots of people dreaming! And the reason is that one of their very latest applications is about to enter many homes in extra-flat television screens, which are even flexible and can be rolled up.

Once again, without plastics this technology would never have seen the light of day. In effect, these innovative screens consist of layers of conductive organic polymers (or to be more precise, semi-conductive) through which an electric field is passed. The thickness of the whole thing is only a few nanometres.

Already, numerous industrial groups have filed patents (mainly Eastman Kodak). This technology is young, however, and there is still room for perfection. One of the major challenges now concerns the lifespan of these OLEDs. At the moment, this is around 14,000 hours as opposed to 50,000 for liquid crystal (LCD) or plasma screens. Research into this is ongoing, however, and Mitsubishi announced a few months ago that it had developed a screen of four metres (diagonally) with a lifespan of 20,000 hours. LCD, plasma… their days are already numbered.

But for lighting too
The screen industry is not the only one to be looking very closely at OLEDs; lighting manufacturers are also taking an interest. In 2009, for instance, Philips placed its Lumiblades on the market: a new type of lighting using OLED technology.

Imagine a flexible light source which can take the shape you fancy, comes in different colours and above all, thanks to its uniform diffusion, does not dazzle. Could this already be the end of low-consumption bulbs?

There is a good chance that it is, because this innovation is aimed at both lighting professionals who need to illuminate entire buildings and ordinary consumers who see it as an original way of brightening up their homes.

OLED, PLED, PHOLED… A tidal wave on its way
We wager that this technology which, it will be recalled, is developing very quickly, is certainly going to lead to a good many objects, which we still regard as modern, being left by the wayside, so promising are its applications.

OLEDs have hardly left the laboratory and we are already talking about PLEDs (Polymer Light-Emitting Diodes, also known as LEPs: Light-Emitting Polymers). To emit light, PLEDs use liquid polymers placed between two flexible sheets. Polymers of this type lend themselves to quick and cheaper industrialisation.
The manufacturing principle is based on active molecules being deposited on the substrate (the sheet) through the same process as with inkjet printers.

Technological revolution under way
Another derivative of OLEDs is PHOLEDs (Phosphorescent Organic Light-Emitting Diodes), which are beginning to emerge from research laboratories. The latest generation of OLEDs, are very similar technologically. However, PHOLEDs have far superior energy efficiency compared to OLEDs since they allow 100% of the electrical energy to be converted into light, whereas with OLED technology only 25% is converted. More clearly, this means that for the same output these new devices will consume four times less energy. The next generations of screens for smart phones, MP4 players and portable games consoles will be fitted with them. So make way for modern devices with greater autosomy.

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PlasticsEurope is the European plastics trade association