Nanoparticle display

Cambridge Display Technology has joined forces with Ilford Imaging Switzerland in a project that promises to pave the way for more optically efficient display devices in the future.

All displays produce more light than is actually seen by the user, due to internal losses in the display itself. By increasing the proportion of observed light, (the ‘optical efficiency’), display devices can be made brighter for a given energy input, or energy consumption can be reduced for a given brightness. This is especially valuable where power efficiency is critical such as in mobile devices such as phones and PDAs.

Ilford, a manufacturer of precision coated, ink jet printing consumables, has discovered that the structure of certain nanoporous materials have potentially valuable properties when applied to polymer light emitting diode (PLED) displays. When integrated into a display device, for example, they have optical properties which help to transmit light which would otherwise be trapped and lost.

The project – which will complete its initial proof-of-principle phase by the end of the first quarter of 2005 – is designed to evaluate and quantify the performance advantages that may be available from using the materials in displays.

Work is ongoing and centred at CDT’s Technology Development Centre near Cambridge, UK, where much of the work is carried out in developing and preparing PLED technology for commercialisation.

The announcement follows the news that an EU-funded two-year programme to understand the science which controls the spin states of polymer-based LEDs (P-OLEDs), critical to developing more power efficient displays, has concluded successfully.

The so-called STEPLED project – carried out with partners Philips, Covion and the Universities of Cambridge, Bologna and Mons – focussed on establishing high efficiency materials using high singlet-ratio fluorescent polymers, but also worked on solution processable phosphorescent emitters, and made significant progress in both areas.

Notably, the project achieved the production of a standard two-layer device structure with an external quantum efficiency (EQE) of 6%. This is almost twice the efficiency of previous materials. The impressive performance was achieved using red emitting polymers, typically the lowest efficiency colour in RGB displays.