20.02.2018 11:56

Physical Chemistry: Cover story in CHEMPHYSCHEM

HHU researchers develop new concept for efficient OLEDs

In collaboration with British colleagues, chemists at Heinrich Heine University Düsseldorf (HHU) have discovered that simple organic carbonyls are potential emitters for organic light-emitting diodes (OLEDs). These molecules are much cheaper and easier to produce than the compounds used today. The research results were presented as a cover story in the scientific journal CHEMPHYSCHEM.

Cover story in CHEMPHYSCHEM. The picture symbolises the transformation of energy from electron-hole pairs (violet) into light through emitters in OLEDs. The illuminated glass vessel shows the colour of the emission. The chimera-like emitter studied here unites apparently contradicting features. (Image: Chimera drawing: Eliza Wiszniewska; Design: Christian Torres Ziegenbein)

OLEDs are being used more and more frequently in smartphone screens and televisions. They are also a very promising alternative for lighting purposes, for example flat panels where the colour of the light can be varied.

The main components of OLEDs are emitter molecules that are intermixed in organic semiconductors. These emitters “harvest” energy from the recombination of electron-hole pairs in the semiconductors and transform this energy into light. Two different pair states (singlets and triplets) can occur in the process. Good emitters are able to transform both types into light. At present, compounds of iridium, a rare and expensive metal, are used for this purpose.

Together with colleagues from Durham University in the UK headed by Professor Andrew Monkman, the Femtosecond Spectroscopy Working Group led by Professor Peter Gilch at the Department of Physical Chemistry of Heinrich Heine University Düsseldorf set out to identify simple organic molecules as alternatives to today’s emitters – and they found some very promising candidates. Their discovery is so important that the scientific journal CHEMPHYSCHEM dedicated a cover story to it.

Professor Gilch and his colleagues identified simple aromatic carbonyls as emitters. These are also able to “harvest” the two types of electron-hole pairs without the need for a metal ion. A carbonyl’s basic structure comprises a carbon atom that is bonded to an oxygen atom via a double bond. This basic structure is also found in many natural products.

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