Researchers develop ‘real’ OLEDs

Researchers have developed a group of phosphorescent materials that can emit light in different colors. The organic materials could be used in OLEDs for display screens and as a lighting source.

The organic materials used in OLEDs, or organic light emitting diodes, are not completely organic; a small amount of metal is required to enable the luminescence of the OLEDs. Without metals, the luminescent materials showed only a very low degree of phosphorescence. The organometallic components are used in, among other things, OLED screens and can serve as a light source. The phosphorescent materials used by employees of the University of Michigan developedare metal-free and could lead to cheaper OLED screens and other OLED applications.

The phosphorescence of the organic ‘phosphors’, as the crystals are called, has a quantum yield of 55 percent, according to the researchers. This high yield is possible because little light energy is lost as heat or vibration within the chemical structure. The light emitted by the materials depends on the chemical composition of their aromatic carbonyl groups. The addition of halogens to the material makes the phosphorescence effective and by changing the composition the color can be controlled.

One of the main advantages of the organic phosphors is the production of blue OLEDs; these are traditionally difficult to produce and degrade fairly quickly. However, with the new method, blue phosphors can be made relatively easily and, moreover, the organic materials are cheaper than the traditional OLED materials, which require rare metals in their production. According to the researchers, it would be “not long” for the organic phosphors to make their way onto production lines, but a forecast was not given. In addition to being a light source, they could also be used in displays that may or may not be flexible.