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    Chemists Provide a Crucial Update to Hyper-Vivid Quantum Dot Screens

    Written by

    Michael Byrne

    Editor

    Screen (or display) technology in 2014 is nuts: LED, SED, LPD, IMOD, PDP, HD, ... Retina. The hyperreality possible is so often just too much, pushing beyond "what things actually look like" and on into the realm of the unnatural and artificial. As something of an analog bystander, the whole rush forward sometimes doesn't seem so much directed toward some visual idyll as directed by technology itself—or shrewd marketing.

    That's an admittedly questionable opinion, and I have to admit to being wowed on occasion by some Blu-Ray updates, to say little of the engineering pocket-miracle I dare still refer to as a "phone." Display technology, like whatever else in current consumer tech, is just getting started, however, no matter that we've already honed in on the theorized limit in which pixels become invisible to the typical human eye (the 300 pixels per inch of Apple's Retina display, though that's up for debate).

    Those now-invisible pixels (maybe) still have the potential to be still more vivid and vibrant, and research being unveiled this week at the 248th National Meeting and Exposition of the American Chemical Society (re)turns to quantum physics for the latest post-reality advance, specifically the peculiar properties of quantum dots.

    A quantum dot is kind of like a very tiny physics cage, capable of keeping a pair of electrons (or the electron-based quasiparticle known as an exciton) in captivity. It's possible to maintain this state with virtually no power expenditure, a property of great interest to the makers of electronic devices and computer system memory. It so happens that power consumption is among the critical flaws of LCD technology, which relies on firing very high energy beams of white light through very dark filters, which convert that light into the colors we see on the screen. By varying the voltage in different pixels, changing the filter properties, it's possible to produce different shades.

    So the screen problem isn't just limited to looks, but LCDs have a related barrier in that department as well. That is, "you always tend to leak a bit of green into red, and blue into green, and so forth," said Eric Nelson, one of the 3M researchers behind this newest technology , in a ACS press release. "So instead of ending up with a very pure red, you end up with an orange-y color. It's difficult to get roses or apples to look very red on a conventional LCD."

    Quantum dots are capable of producing colors without the need for filters in a conventional LCD sense. Colors are based on the dots' relative sizes, as there's a direct relationship between the size of a quantum dot and its emitted energy, and thereby the sorts of light it gives off. If a dot is very, very small, it takes more energy to hold its electrons in captivity. Imagine a prisoner pacing up and down a cell that gets progressively smaller and smaller. As the floor space shrinks, they contact the walls with greater and greater frequency, which increases the amount of power it takes to keep them confined. In light terms, as frequencies increase, colors shift toward blue. So, rather than blasting a liquid-crystal layer with white light, a quantum dot display makes its own colors from scratch.

    This is not something brand new, it should be noted. Organic LED (OLED) technology also works by manipulating the energy levels of electrons (or excitons) and forcing them to give up photons, or light particles, in a process that is similarly tunable. OLED technology is expensive, however, but maintains its shadow over quantum dot displays in part because the latter tend to be prone to quick degradation when exposed to air or water. Nonetheless, dot-based technology is already out in the world via the Kindle Fire HDX (at least).

    "One drawback of QDs is their susceptibility to oxidization and hydrolysis," the 3M presentation's abstract reads. "To maintain their high fluorescence quantum yield, the QDs must be maintained in an air free environment. Therefore to make a commercial LCD application possible, a delivery format that maintains an air free environment and can be easily handled is required." This is a problem.

    The 3M team's advance comes in the form of a special polymer film that sandwiches the quantum dots in a protected layer. This layer has the additional benefit, according to the researchers, of keeping the heavy metals needed for the technology sealed and, theoretically, keeping those metals out of landfills. The proper name for 3M's new product is quantum dot enhancement film (QDEF).

    Whether it's the technology that will fully usher in the new era of quantum displays or not isn't guaranteed, but, at the same time, 3M isn't exactly a startup and already has its various film products all over your non-quantum devices. I wouldn't expected QDEF to languish in that kind of corporate closet for very long.

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