"Shadow state" discovery could dramatically boost solar power efficiency

Researchers at the University of Texas say it is possible to hike the energy yield of solar cells by exploiting what they call a photon's "shadow state", doubling the number of electrons that may be harvested in the process. They claim the discovery could up the theoretical maximum efficiency of silicon solar cells from 31 to 44 percent.

Prior research led by chemist Xiaoyang Zhu demonstrated that a theoretical increase in efficiency to as high as 66 percent would be possible if solar cells could be made to additionally harvest so-called "hot electrons", residual heat energy that is lost within about a picosecond after a cell absorbs a photon. Zhu then found that this was possible, but only when harvesting photons from "highly focused" sunlight, impractical in real-world applications.

But the team's latest findings point to an alternative means of boosting efficiency. The organic plastic semiconductor pentacene, when absorbing a photon, creates an exciton (an electron paired with an electron hole) which is quantum mechanically coupled to a dark "shadow state" multiexciton from which an additional electron can be harvested. This way, a photon provides double the electrons. Zhu says that the process could see solar cell efficiency increase to 44 percent without the need for a focused solar beam.

"Plastic semiconductor solar cell production has great advantages, one of which is low cost," said Zhu. "Combined with the vast capabilities for molecular design and synthesis, our discovery opens the door to an exciting new approach for solar energy conversion, leading to much higher efficiencies."

The latest University of Texas findings were published on December 16 inScience.

Speaking, interactive dashboard avatar could replace owner's manuals

At one time not all that long ago, cars had a warning light on the dashboard that simply said "ENGINE." That's pretty vague. Really, it might just as well have said "CAR." Some newer automobiles now have codes that appear on the console, which the driver must then look up in an index in the vehicle's owner's manual. Working with Audi, Germany's Technische Universitaet Muenchen (TUM) Institute of Business Informatics is now working on taking things a step farther, with the development of an on-screen avatar that will talk to drivers, and even understand their spoken questions.

The experimental Avatar-based Virtual Co-driver System (AviCoS) is designed to work with the monitor of the Audi Mulitmedia Interface, which already comes standard on all of the automaker's vehicles.

The system uses artificial intelligence to understand drivers' spoken questions about their car, and responds verbally. Descriptive images and videos also appear on-screen, with the animated avatar character pointing out relevant details. In Touch and Tell mode, drivers can also receive explanations of various vehicle functions by touching the appropriate areas of the screen.

As with many such driver assistance technologies, there is the possibility that AviCoS could distract drivers from paying attention to the road. The designers have somewhat addressed that problem, by suppressing first the image of the avatar, and then all of the graphics, as the vehicle's speed increases. Drivers remain able to converse with the avatar, however, which could still be distracting.

Down the road, the TUM researchers would like to see the system being able to identify the driver's state of mind, by analyzing their tone of voice and speech rhythm. If AviCoS determined that the driver was getting stressed out, it could lessen their sensory overload by suppressing its video output. Working with the car's other systems, it could also do things such as instructing the navigation system to provide directions earlier, and more often.

Latest LHC experiments show early universe behaved like a liquid

Physicists from the ALICE detector team have been colliding lead nuclei together at CERN's Large Hadron Collider (LHC) in an attempt to recreate the conditions in the first few microseconds after the Big Bang. Early results have shown that the quark-gluon plasma created at these energies does not form a gas as predicted, but instead suggest that the very early universe behaved like a hot liquid.
The Large Hadron Collider enables physicists to smash together sub-atomic particles at incredibly high-energies, providing new insights into the conditions present at the beginning of the universe.

ALICE (an acronym for A Large Ion Collider Experiment) researchers have been colliding lead nuclei to generate incredibly dense sub-atomic fireballs – mini Big Bangs at temperatures of over ten million degrees.
Previous research at lower energies had suggested the hot fire balls produced in nuclei collisions behaved like a liquid, yet many still expected the quark-gluon plasma to behave like a gas at these much higher energies.
Additionally, it has been found that more sub-atomic particles are produced in the collision than some theoretical models suggested.
“Although it is very early days we are already learning more about the early Universe,” said Dr David Evans, from the University of Birmingham’s School of Physics and Astronomy, and UK lead investigator at ALICE experiment. “These first results would seem to suggest that the Universe would have behaved like a super-hot liquid immediately after the Big Bang.”

The ALICE experiment aims to study the properties of the state of matter called a quark-gluon plasma. The ALICE Collaboration comprises around 1,000 physicists and engineers from around 100 institutes in 30 countries. During collisions of lead nuclei, ALICE will record data to disk at a rate of 1.2 gigabytes (GB), equivalent to two CDs every second, and will write over two petabytes (two million GB) of data to disk. This is equivalent to more than three million CDs, or a stack of CDs without boxes several miles high!
To process this data, ALICE will need 50,000 top-of-the-range PCs, from all over the world, running 24 hours a day.