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and Samsung have invested jointly a total of €25 million to support the development of Cynora’s efficient blue OLED technology. OLED displays currently require
relatively large blue pixel areas to reach suitable brightness. By implementing Cynora’s efficient TADF emitters, display manufacturers could create smaller blue pixels that yield the same amount of light, enabling potential further increases in resolution. The new emitters could also simplify fabrication and lower the cost of OLEDs by reducing the layers required in
A leg up from lasers
their structure, according to the company. Cynora aims to release its first blue OLED emitters by end of this year. Wrzeszcz stated: ‘We strongly believe our TADF materials will contribute to the next material-driven advancement of the OLED industry.’ In the longer term, the firm intends to develop green and red TADF emitters, with plans to introduce them by the end of 2019.
A dot-to-dot picture There will be a significant boost in late
2019 for OLED television manufacturing infrastructure once LG – as the sole maker of OLED television panels – commences operations in its two new manufacturing lines being built in South Korea and China. Meanwhile, other manufacturers, such as China’s BOE Display and CSOT, are also looking at developing their own OLED technology, but even after they’ve done the development work, they will still have to construct $5-10 billion production facilities before they can enter the market, according to Virey.
The period of constrained OLED panel production will present a window of opportunity for competing WCG technologies, particularly quantum dots. Quantum dots offer comparable picture quality to OLED displays and can be manufactured using pre-existing LCD manufacturing infrastructure. Quantum dots are tiny semiconductor structures measuring 2nm to 8nm in diameter that can be grown in large reactors using a chemical self-assembly process. They are highly efficient energy converters that become charged and emit different wavelengths of visible photons after being excited using short wavelength, high energy light. By incorporating them in LCD televisions, WCG performance and an overall dramatic increase in picture quality can be achieved. ‘Quantum dots allow us to show a much
Development of plastic-based electronics is a growing area of research
OLED displays are beginning to take the form of flexible, foldable, rollable and even stretchable structures. While this transition is occurring at high speed, according to Rainer Paetzel, director of marketing at Coherent, display manufacturers still make use of conventional processes such as chemical and physical vapour deposition, lithography and etching, leaving room to incorporate newer, more advanced procedures into their infrastructure. Coherent is now promoting
technologies such as its HyperRapid NX series of ultrashort pulsed lasers to complement the fabrication of organic and printed electronics (OPE), which are manufactured using processes such as screen printing, inkjet printing, flexography, gravure printing and offset
16 Electro Optics November 2017
lithography. Paetzel explained that these electronics could help improve the production of modern devices such as smartphones and wearable technology. ‘At this moment OLED
displays are not hinged on OPE, but in the mid-term OPE will find formidable opportunities in combination with OLED … and has the chance to substitute traditional processes to reach lower cost and less material usage,’ he said. However, virtually all the
above printing techniques have been designed to yield structures discernible by the human eye, and are therefore limited to a spatial resolution of approximately 20µm. Laser applications such as ablation, sintering, curing, cutting, drilling and annealing can thus be used to complement printing
processes by enabling higher resolutions – approximately 5µm with ablation – which are crucial for the continued miniaturisation of OPE. Coherent believes that OPE
offers tremendous promise for manufacturing OLED displays and other modern technologies. However, printing processes must first overcome significant technological hurdles in order to achieve widespread OPE adoption. ‘The unique processing capabilities of ultra-short laser pulses, together with a new generation of products that deliver these pulses in a reliable, flexible and cost- effective manner, may be a key enabler in enhancing the resolution, and hence market opportunities, for OPE technology,’ Paetzel concluded.
broader range of colour,’ commented Yurek, of Nanosys. ‘They can be made to produce any colour in the visible spectrum, while also producing light very efficiently – they are 99 per cent efficient, making them … [one of the] world’s most efficient light emitting materials.’ In 2009 Nanosys, a supplier of quantum
dots for Samsung – one of the main producers of quantum dot televisions – introduced a glass optic known as a Quantum Rail that fitted on to televisions to deliver quantum dot capabilities. While effective, this format proved to be too disruptive to existing LCD production cycles, as extra processes and machines were needed to incorporate the optic. Nanosys was therefore faced with the challenge of introducing quantum dots to LCDs, while minimising the capital expenditure and inconvenience faced by display manufacturers. ‘This led us to producing quantum dot enhancement films (QDEFs), which involve coating a PET film with quantum dots and then dropping it into the backlight of an LCD, replacing the pre-existing diffuser film and requiring no additional production steps,’ said Yurek. QDEFs are therefore much cheaper and
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Coherent
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