USA - University of Utah, physicists have moved a step forward in building an organic "spin transistor": a plastic semiconductor switch for future ultrafast computers and electronics.
The researchers Christoph Boehme and John Lupton, assistant and associate professors of physics, respectively, at the University of Utah, reported to have successfully controlled an electrical current using the "spin" within electrons. The experiment merged organic semiconductor electronics and spin electronics, or spintronics, which is part of quantum mechanics - the branch of physics that describes the behavior of molecules, atoms and subatomic particles.
In the study, they showed that information can be carried by spins in an organic polymer, and that a spin transistor is possible because "we can convert the spin information into a current, and manipulate it and change it," says Lupton. "We are manipulating this information and reading it out again. We are writing it and reading it."
Spin transistors and other spin electronics could make possible much smaller computer chips, and computers that are orders of magnitude faster than today's. Even the smallest transistor today consists of hundreds of thousands of atoms. The ultimate goal of miniaturization is to implement electronics on the scale of atoms and electrons say the researchers.
OLED efficiencies bleak?
Unfortunately the studies also suggest that OLEDs will not convert more than 25 percent of electricity into light rather than heat - at least for the organic polymer studied - pure MEH-PPV - and possibly for others, which is disappointing as earlier estimates by other researchers at University of Utah predicted up to 63 percent.
Inorganic LEDs used in traffic signals, building lighting and other electronic devices are more expensive to manufacture than Organic semiconductor or "plastic" LEDs.
"Doping" organic semiconductors with other chemicals someday might lead to OLED efficiencies above 25 percent, but Boehme says he is skeptical.
Even if OLEDs are less efficient and have a shorter lifespan than inorganic LEDs, they still may be more economical because their cost is so much less, he adds.
Boehme says OLEDs' greatest promise is not in lighting, but to replace the LCD (liquid crystal display) technology in modern televisions and computer screens but millions of dollars are being invested in OLED lighting projects and many experts believe OLEDs will have a leading opportunity in the multi-billion dollar lighting market which indicates that although this process has limited opportunities there is still more to come from OLEDs.
However, OLEDs are still some years away from becoming a practical general illumination source. Additional advancements are needed in light output, color, efficiency, cost, and lifetime.
Other current research includes the Tokyo Institute of Technology who have used an amorphous fluoropolymer as a substrate for OLEDs to increase their light-emitting efficiency by 40% and University of Michigan with Princeton University who believe that are close to breaking the OLED-efficiency logjam. They have designed an OLED that boosts illumination by 60 percent using a combination of an organic grid working in tandem with small micro lenses that guide the trapped light out of the device.
For more on OLED lighting read European projects accelerate OLED technology for mainstream lighting and OLEDs - The future of architectural lighting, A major milestone - white OLED technology exceeds 100 lm/W.