‘Spintronic’ oled promises brighter displays

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Physicists at the University of Utah have invented a new 'spintronic' oled which they say promises to be brighter, cheaper and more environmentally friendly than current leds.

"It's a completely different technology," said distinguished professor of physics Z Valy Vardeny. The team created a prototype of the new kind of led – known as a spin polarised organic led or spin oled – that produces an orange colour. They expect it will be possible to produce red and blue within two years and eventually white as well. The spintronic device uses an organic semiconductor and stores information using the spins of the electrons. This was enabled by the team's previous creation of an organic spin valve which they modified to emit light as well as regulate current flow. Organic spin valves are comprised of three layers: an organic layer that acts as a semiconductor and is sandwiched between two metal electrodes which are ferromagnets. In the new spin oled, one of the ferromagnets is made of cobalt and the other is made of a compound called lanthanum strontium manganese oxide. The organic layer is a polymer known as deuterated-DOO-PPV, which is the semiconductor that emits the orange coloured light. According to the researchers, using deuterium instead of hydrogen made the device more efficient. The team also deposited a thin layer of lithium fluoride on the cobalt electrode which they say allows negatively charged electrons to be injected through one side of the spin valve at the same time as positively charged electron holes are injected through the opposite side. "When they meet each other, they form 'excitons,' and these give you light," said Vardeny. This also means that the spintronic oleds can be controlled with a magnetic field rather than requiring more electrical current to boost light intensity. At the moment, oleds produce a particular colour of light based on the semiconductor used. The researchers say that the new spin oleds could be a step towards creating a device which can produce different colours when controlled by changes in magnetic field.