Organic LED could improve efficiency of LCD screens

Scientists at Imperial College London are developing a new kind of organic LED that could hugely improve the efficiency of LCD screens.

The team hopes to create OLEDs that emit circularly polarised electroluminescence (CPEL) – light waves that effectively travel in a spiral motion – as opposed to the non-polarised light that comes from typical LEDs.

This would remove the need for the polarising filters used in LCD screens that cut out up to 75 per cent of normal backlighting, as well as providing the high contrast levels seen on LED-backlit screens. Organic LEDs also have the advantage of being much thinner than inorganic ones.

‘At the moment, to generate circularly polarised light you take unpolarised light and use polarising filters, whereas we specifically want to generate circularly polarised light,’ principal investigator Dr Matthew Fuchter told The Engineeer.

‘It’s intrinsically more efficient to directly generate it, rather than use filters that cut out energy.’

Because circularly polarised light can travel in a clockwise or anti-clockwise direction, it could also be used in photonic technology.

‘In optical communication where light is the signal, if you can have left- and right-handed polarised light you can effectively double your channel capacity,’ said Fuchter.

His colleague, Dr Alasdair Campbell, added: ‘There might well be potential applications in terms of very fast switching, telecommunications and possibly even quantum computing.’

To create the OLEDs, the team will need to design and prepare suitable organic materials and get them to align suitably within the device to generate sufficient amounts of light.

‘People have tried previously to do this using polymeric organic materials,’ said Fuchter. ‘We’ve got a substantially different approach.

‘Rather than having a big chain that is a single molecule, we’re looking at individual small molecules that will spontaneously self-assemble into a well-structured aggregate.’

The team has received a £240,000 ESPRC grant to prove the concept over the next 18 months. Fuchter pointed out that, while other organic LED devices have taken as long as 20 years to develop, a commercial product based on his work would be able to use existing technology and so could potentially be available much quicker.

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