Category: LTM News
March 23, 2016

One of the main drawbacks of OLEDs is the limited amount of functional colours available owing to the small number of organic molecules which are able to undergo electroluminescence. The Wolfson Centre in Brunel University has a dedicated research team, within the LTM project to investigate means by which to overcome this limitation.

Since the emission of OLEDs is composed of a single wavelength (i.e. monochromatic light) the use of filters to modify the output colour is not possible and ultimately leads to a reduction in the intensity. There is, however, a solution represented by light down-conversion based on the principle of fluorescence. Fluorescent materials are able to absorb specific wavelengths of the light and convert them in different colours via an internal excitation-relaxation process of the electrons.

The research team at Brunel University have developed different layers for the colour conversion of blue and green OLEDs. These are silicone based layers which have been functionalised with hybrid organic-inorganic fluorescent materials and have been produced and tested demonstrating outstanding colour conversion efficiency, optical stability and allow for the dispersion of wide range of organic compounds in an otherwise, non-miscible environment. More recently, thin, transparent and flexible coatings based on fluorescent molecules embedded in polymer matrices have been developed. Their chemical-physical properties allow for easy application directly on the top layers of OLEDs by screen printing technology.

During the course of the last meeting in Milan [LTM Workshop nr. 10] these colour conversion layers (CCLs) were showcased to the designer panels and are currently available for them to be implemented in their design concept demonstrators.

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