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EETE JULAUG 2012

MATERIAL SCIENCES Nanosys teams with 3M film to yield less-costly LCDs By Nicolas Mokhoff Nanosys and the Optical Systems Division of 3M are collabo- formance that has been largely neglected for the last decade,” rating to commercialize Nanosys’ Quantum Dot Enhancement said Jason Hartlove, President and CEO of Nanosys. “Working Film color LCD technology, which could result together with 3M and utilizing their outstand- in delivering OLED performance to LCDs, at ing design and supply chain capabilities will a fraction of the cost and with better energy allow our QDEF technology to be widely efficiency. 3M and Nanosys will work together deployed across all product segments and to commercialize Nanosys’ QDEF technology, will ensure availability to all customers.” a drop-in film that LCD manufacturers can A quantum dot emits light at a very integrate with existing production processes. It precise wavelength. The ability to control utilizes the light emitting properties of quantum the spectral output of a quantum dot allows dots to create a backlight for LCDs. QDEF to create an ideal white backlight “Combining the world class-technology and materials exper- specifically designed for LCDs. Trillions of these quantum dots tise of Nanosys with the engineering, design and supply chain are packaged into a thin film that fits inside an LCD backlight capabilities of 3M will unlock a powerful new color viewing unit. QDEF replaces a similar film already found inside LCD experience for consumers,” said Jim Bauman, Vice President backlights, which means that adding QDEF to manufactur- of the Optical Systems Division at 3M, here at the Society for ing processes requires no new equipment or process changes Information Display venue. Current LCDs are limited to display- for the LCD manufacturer. The Society of Information Display ing 35 percent or less of the visible color spectrum. awarded Nanosys with the 2012 Display Industry Awards Gold “We are working together to improve an area of display per- Display Component of the Year for its QDEF. Cubic silicon carbide could be twice as good as silicon for solar cells By Julien Happich According to Swedish researchers at the Linköping growth rate, at 1mm/hour. The group applies hexagonal silicon University, cubic silicon carbide may be capable of collecting carbide as substrate, and the material is transformed to the more than twice the solar energy than silicon based solar cells. cubic structure during initial stage of growth. The advantage of The cubic silicon carbide is considered a perfect material for using hexagonal substrate is the perfect matching. Structural impurity (intermediate bandgap) solar cell. For measurements have showed a similar quality boron doped cubic SiC, the dopant band of B in like in hexagonal commercial material. The key the bandgap of 3C‐SiC leads to an efficient use parameter in showing off the quality is the carrier of sun light so that an efficiency up to 48‐60% lifetime. Previously this had a lifetime of about could be achieved depending on theoretical 0.1 µs, while the new record value is 8.2µs in as‐ models. But so far, cubic silicon carbide has grown material, an increase of almost two orders shown to be the black sheep of the silicon of magnitude. In comparison, this is even slightly carbide family, explains Mikael Syväjärvi, associ- better than that in hexagonal silicon carbide. ate professor at the Linköping University. While Today’s silicon solar cells have an efficiency hexagonal silicon carbide types have been com- of 20%. In order to increase the efficiency of so- mercialized for many years, cubic silicon carbide Cubic silicon carbide grown on lar cells, multi-junction (thin film) solar cells with has faced too many challenges, such as being different bandgaps is one of the most promising hexagonal silicon carbide. metastable, meaning that it does not really want approaches. The best efficiency of such solar to form. One has to decrease the growth temperature to make cells demonstrated on the research scale is 43.5%. However, it form, but at the same time the growth rate is decreased. The the challenges in fabrication of multi-junction solar cells lie in common approach is to use silicon as substrate, but the lattice the growth of multi‐stacked material and balance of junction and thermal mismatch causes defects and stress. currents. Cubic silicon carbide in a single material which is The Swedish researchers have applied a bulk growth ap- doped during growth, having a high growth rate such as 1 mm/ proach like used in production of hexagonal silicon carbide. hour, could pave the way for more efficient solar cell concepts. According to Syväjärvi, the trick is to lower the growth tem- These results on the growth of cubic silicon carbide were pub- perature while adjusting other parameters to maintain a high lished in the Applied Physics Letter of June 18. www.electronics-eetimes.com Electronic Engineering Times Europe July/August 2012 5


EETE JULAUG 2012
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