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Nuclear spins make current in OLED stronger or weaker

Posted: 23 Sep 2014     Print Version  Bookmark and Share

Keywords:OLED  nuclear spin  current 

Boehme says scientists previously have claimed that current in plastic semiconductors known formally as pi-conjugated polymers can be controlled by the nuclear spins in hydrogen. Until the new study, nobody has ever shown it directly at room temperature by turning nuclear spins to change an electrical current, added Boehme.

In the new experiments, the physicists used magnetic resonance to reverse the nuclear spins in hydrogen isotopes embedded in the OLED, and then were able to detect how the reversed spins caused a change in the electrical current through the OLED.

In the first two experiments, Boehme said, the physicists made nuclear spins in a proton and deuterium wiggle in characteristic ways, and were able to read corresponding wiggles in the resulting electrical current. In a third experiment, they flipped the spins back and forth at a rate they wanted instead of at the characteristic frequencies.

It worked, said Boehme. This shows you can turn a nuclear spin when you want, and only then the current turns around. We can control a current by controlling nuclear spins.

The researchers measured the current change directly, but not resulting changes in the OLEDs light output changes so small they aren't detectable with the naked eye.

In both the 2010 and the new studies, the physicists did not read the spins of individual nuclei, but the collective spins of more than 1 million nuclei at a time. The ultimate goal is to be able to read the spins of nuclei individually.

If you want to store information, the highest storage density would be to store information in single nuclear spins, said Boehme. Since the 2010 study, other physicists have achieved that in phosphorus nuclei.

By storing information using both spins and electrical charge, spintronic devices should have greater storage capacity and process data more quickly although researchers still have years to go to figure out how to connect and process spintronically stored information in futuristic computers, conventional and quantum.

We don't know if its five years, 50 years or never, said Boehme.

Yet Boehme said spintronics already resulted in today's terabyte-sized computer hard drives, which use spintronic 'read heads' so small that data can be stored more densely.

In 2012, Boehme and colleagues showed the same spintronic OLED in the new study works as a 'dirt cheap' magnetic field sensor at room temperature without being compromised by degradation. Such sensors may enable more accurate spacecraft navigation systems, said Boehme.

Because nuclear spin-controlled electrical current regulates output of light by the OLED, it provides a way to study how to make OLEDs more efficient. OLEDs convert far more electricity into light than incandescent light bulbs, which turn most incoming electricity into heat. But there is much more room for improved efficiency.

Hopefully, OLEDs will become better use less electricity and produce more light because we learned here how nuclear spins orientation influences how well the OLED works, said Boehme. Any sort of efficiency limitation can only be overcome if the mechanism that imposes this limitation is understood.

- Paul Buckley
  EE Times Europe

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