05 Oct 2015
|Source: University of Illinois College of Engineering|
11 Aug 2015
Recently, quantum dots (QDs)–nano-sized semiconductor particles that produce bright, sharp, color light–have moved from the research lab into commercial products like high-end TVs, e-readers, laptops, and even some LED lighting. However, QDs are expensive to make so there’s a push to improve their performance and efficiency, while lowering their fabrication costs.
Researchers from the University of Illinois at Urbana-Champaign have produced some promising results toward that goal, developing a new method to extract more efficient and polarized light from quantum dots (QDs) over a large-scale area. Their method, which combines QD and photonic crystal technology, could lead to brighter and more efficient mobile phone, tablet, and computer displays, as well as enhanced LED lighting.
With funding from the Dow Chemical Company, the research team, led by Electrical & Computer Engineering (ECE) Professor Brian Cunningham, Chemistry Professor Ralph Nuzzo, and Mechanical Science & Engineering Professor Andrew Alleyne, embedded QDs in novel polymer materials that retain strong quantum efficiency. They then used electrohydrodynamic jet (e-jet) printing technology to precisely print the QD-embedded polymers onto photonic crystal structures. This precision eliminates wasted QDs, which are expensive to make.
These photonic crystals limit the direction that the QD-generated light is emitted, meaning they produce polarized light, which is more intense than normal QD light output.
According to Gloria See, an ECE graduate student and lead author of the research reported in Applied Physics Letters, their replica molded photonic crystals could someday lead to brighter, less expensive, and more efficient displays. “Since screens consume large amounts of energy in devices like laptops, phones, and tablets, our approach could have a huge impact on energy consumption and battery life,” she noted.
“If you start with polarized light, then you double your optical efficiency,” See explained. “If you put the photonic-crystal-enhanced quantum dot into a device like a phone or computer, then the battery will last much longer because the display would only draw half as much power as conventional displays.”
To demonstrate the technology, See fabricated a novel 1mm device (aka Robot Man) made of yellow photonic-crystal-enhanced QDs. The device is made of thousands of quantum dots, each measuring about six nanometers.
“We made a tiny device, but the process can easily be scaled up to large flexible plastic sheets,” See said. “We make one expensive ‘master’ molding template that must be designed very precisely, but we can use the template to produce thousands of replicas very quickly and cheaply.”
The above post is reprinted from materials provided by University of Illinois College of Engineering. The original item was written by Laura Schmitt. Note: Materials may be edited for content and length.
- Gloria G. See, Lu Xu, Erick Sutanto, Andrew G. Alleyne, Ralph G. Nuzzo, Brian T. Cunningham. Polarized quantum dot emission in electrohydrodynamic jet printed photonic crystals. Applied Physics Letters, 2015; 107 (5): 051101 DOI: 10.1063/1.4927648
Yole Développement says revenues “will exceed phosphors by 2020” as adoption
into LCD TVs rivals OLED quality.
Quantum dots’ virtual adoption cycle, according to Yole Développement
Yole Développement (Yole), the Lyon, France-based market research and strategic
consulting company, has published its new LED down converters technology and market
It presents a detailed review of the industry, especially the impact of the development of
quantum dots on the display and conventional phosphors industry. Yole asks, are quantum dots
now a serious competitor to OLED-based technologies – and its conclusion is: quantum dots
are finally ready for prime time and will exceed traditional phosphor revenue by 2020 by
allowing LCD to compete with OLED in the race for the next generation of displays.”
After the lukewarm reception of 3D and 4K screens, Yole comments that the display
industry needs a “new and disruptive experience improvement” to bring consumers back
to the stores: “image quality perception increases significantly when color gamut and
dynamic contrast ratio are improved.” Yole also notes that “Leading movie studios,
content providers, distributors and display makers have together formed the UHD Alliance
to promote those features.”
Dr Eric Virey, Senior Analyst, LEDs at Yole, commented, “OLED was believed to be
the technology of choice for this next generation of displays. But production challenges
have delayed the availability of affordable OLED TVs. LCD TVs with LED backlights
based on quantum dot down-converters can deliver performance close to, or even
better than OLED in some respects, and at a lower cost.”
QD-LCD ‘could pull ahead’ of OLED display
Until OLEDs are ready, says Yole, “QD-LCD technology will have a unique window of
opportunity to try to close enough of the performance gap such that the majority of
consumers will not be able to perceive the difference between the two technologies
so price would become the driving factor in the purchasing decision.” Under this scenario,
the analyst believes that QD-LCD could establish itself as the dominant technology while
struggling OLEDs “would be cornered into the high end of the market.”
Yole acknowledges that OLED-based displays potentially offer more opportunities for
differentiation but the analyst notes, “OLED proponents need to invest massively and
still have to resolve manufacturing yield issues. For tier-2 LCD panel makers who
cannot invest in OLED, Quantum Dots offer an opportunity to boost LCD performance
without imposing additional CAPEX on their fabs.” At this year’s Consumer Electronics
show, as optics.org reported, no fewer than seven leading TV OEMs including
Samsung and LG demonstrated QD-LCD TVs.
With tunable and narrowband emissions, QDs offer design flexibility to developers
of new displays. But more is needed to enable massive adoption, including the d
evelopment of cadmium-free formulations. Cole cautions that “traditional phosphors
still have to say their last word”. If PFS could further improve in term of stability and decay
time and a narrow-band green composition was to emerge, traditional phosphors could
also be part of the battle against OLED, Yole concludes.
Yole’s analysis Phosphors & Quantum Dots 2015: LED Down-converters for Lighting & Displays
presents an overview of the quantum dot LED market for display and lighting applications
including quantum dot manufacturing, benefits and drawbacks, quantum dots LCD versus
OLED and detailed market forecast. For more information about this report and other
LED technology & market analysis from Yole, visit i-micronews in its LED Reports section.