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OLED chemists have a bright idea


23 November 2007

Organic light-emitting diodes (OLEDs) can be made more cheaply and easily thanks to a new molecule made by Chinese chemists. OLEDs use less power than liquid crystal displays (LCDs) and can be made much thinner, so making them cheaper and longer-lasting is important for the electronics industry. 

OLED
A pixel made from the new material, which can emit red, green and blue light, allows OLED devices to comprise only two layers

© Yunqi Liu
Most OLED materials need several layers to provide a flow of electrons and 'holes', or spaces where electrons can move into, and other layers to stop the flow of electrons or holes in the right places. But the new molecule improves on current OLED designs by performing several necessary electronic functions in just one layer. It can also be treated to emit all the colours required for laptop and mobile phone displays. 

The new molecule comprises a quinoxaline group, which accepts electrons very readily, and bulky polyphenyl groups, which stop the molecules sticking together and losing energy by nonradiative pathways - this means it can take the place of several layers in the OLED. 

The work provides 'a simple and effective approach to construct[ing] highly efficient and multicoloured OLEDs,' the researchers say. One of the authors of the paper, Yunqi Liu of the Beijing National Laboratory for Molecular Sciences, Beijing, told Chemistry World: 'Our research opens a way for designing and applying multifunctional materials in OLEDs to simplify the fabrication process.' 

But John de Mello, senior lecturer in nanomaterials at Imperial College London, UK, suggests the material isn't ready to use on a commercial basis. 'This is a very interesting approach to colour tuning in organic light-emitting diodes, although one that may require further optimisation for practical use,' he said. 'The devices appear to have rather high current and voltage demands, which suggests alternative materials systems may be needed to achieve adequate power efficiencies.' 

Jonathan Edwards 

 

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References

X Xu et alJ. Mater. Chem., 2007, DOI: 10.1039/b710139b

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