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develops flexible batteries using solid state thin film lithium polymer, Polymer Matrix Electrolyte (PME) for batteries enabling new small IoT devices, smart clothing, healthcare and more.
OLED with the composite structure of TiO2/graphene/conducting polymer electrode in operation. The OLED exhibits 40.8% of ultrahigh external quantum efficiency (EQE) and 160.3 lm/W of power efficiency. The device prepared on a plastic …more
The arrival of a thin and lightweight computer that even rolls up like a piece of paper will not be in the far distant future. Flexible organic light-emitting diodes (OLEDs), built upon a plastic substrate, have received greater attention lately for their use in next-generation displays that can be bent or rolled while still operating.
A Korean research team led by Professor Seunghyup Yoo from the School of Electrical Engineering, KAIST and Professor Tae-Woo Lee from the Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH) has developed highly flexible OLEDs with excellent efficiency by using graphene as a transparent electrode (TE) which is placed in between titanium dioxide (TiO2) and conducting polymer layers. The research results were published online on June 2, 2016 in Nature Communications.
OLEDs are stacked in several ultra-thin layers on glass, foil, or plastic substrates, in which multi-layers of organic compounds are sandwiched between two electrodes (cathode and anode). When voltage is applied across the electrodes, electrons from the cathode and holes (positive charges) from the anode draw toward each other and meet in the emissive layer. OLEDs emit light as an electron recombines with a positive hole, releasing energy in the form of a photon. One of the electrodes in OLEDs is usually transparent, and depending on which electrode is transparent, OLEDs can either emit from the top or bottom.
In conventional bottom-emission OLEDs, an anode is transparent in order for the emitted photons to exit the device through its substrate. Indium-tin-oxide (ITO) is commonly used as a transparent anode because of its high transparency, low sheet resistance, and well-established manufacturing process. However, ITO can potentially be expensive, and moreover, is brittle, being susceptible to bending-induced formation of cracks.
Graphene, a two-dimensional thin layer of carbon atoms tightly bonded together in a hexagonal honeycomb lattice, has recently emerged as an alternative to ITO. With outstanding electrical, physical, and chemical properties, its atomic thinness leading to a high degree of flexibility and transparency makes it an ideal candidate for TEs. Nonetheless, the efficiency of graphene-based OLEDs reported to date has been, at best, about the same level of ITO-based OLEDs.
As a solution, the Korean research team, which further includes Professors Sung-Yool Choi (Electrical Engineering) and Taek-Soo Kim (Mechanical Engineering) of KAIST and their students, proposed a new device architecture that can maximize the efficiency of graphene-based OLEDs. They fabricated a transparent anode in a composite structure in which a TiO2 layer with a high refractive index (high-n) and a hole-injection layer (HIL) of conducting polymers with a low refractive index (low-n) sandwich graphene electrodes. This is an optical design that induces a synergistic collaboration between the high-n and low-n layers to increase the effective reflectance of TEs. As a result, the enhancement of the optical cavity resonance is maximized. The optical cavity resonance is related to the improvement of efficiency and color gamut in OLEDs. At the same time, the loss from surface plasmon polariton (SPP), a major cause for weak photon emissions in OLEDs, is also reduced due to the presence of the low-n conducting polymers.
Under this approach, graphene-based OLEDs exhibit 40.8% of ultrahigh external quantum efficiency (EQE) and 160.3 lm/W of power efficiency, which is unprecedented in those using graphene as a TE. Furthermore, these devices remain intact and operate well even after 1,000 bending cycles at a radius of curvature as small as 2.3 mm. This is a remarkable result for OLEDs containing oxide layers such as TiO2 because oxides are typically brittle and prone to bending-induced fractures even at a relatively low strain. The research team discovered that TiO2 has a crack-deflection toughening mechanism that tends to prevent bending-induced cracks from being formed easily.
Professor Yoo said, “What’s unique and advanced about this technology, compared with previous graphene-based OLEDs, is the synergistic collaboration of high- and low-index layers that enables optical management of both resonance effect and SPP loss, leading to significant enhancement in efficiency, all with little compromise in flexibility.” He added, “Our work was the achievement of collaborative research, transcending the boundaries of different fields, through which we have often found meaningful breakthroughs.”
Professor Lee said, “We expect that our technology will pave the way to develop an OLED light source for highly flexible and wearable displays, or flexible sensors that can be attached to the human body for health monitoring, for instance.”
Explore further: Nanometer Graphene Makes Novel OLEDs Display
More information: Jaeho Lee et al, Synergetic electrode architecture for efficient graphene-based flexible organic light-emitting diodes, Nature Communications (2016). DOI: 10.1038/NCOMMS11791
The INM will be presenting flexible touch screens, which are printed on thin plastic foils with recently developed nanoparticle inks, using transparent, conductive oxides (TCOs).
Mobile phones and smart phones still haven‘t been adapted to the carrying habits of their users. That much is clear to anyone who has tried sitting down with a mobile phone in the back pocket: the displays of the innumerable phones and pods are rigid and do not yield to the anatomical forms adopted by the people carrying them. By now it is no longer any secret that the big players in the industry are working on flexible displays. How to produce suitable coatings for those cost-efficiently will be demonstrated by INM – Leibniz-Institute for New Materials at stand B46 in hall 2 at this year’s Hannover Messe as part of the leading trade fair for R & D and Technology Transfer which takes place from 25th to 29th April.
The INM will be presenting flexible touch screens, which are printed on thin plastic foils with recently developed nanoparticle inks, using transparent, conductive oxides (TCOs). These inks are suitable for a one-step printing process. Thus transparent lines and patterns are obtained by inkjet printing or alternatively by direct gravure printing, which are electrically conductive even after bending. Thus, a one-step-printing process for cost-efficient TCO structures is enabled.
Conductive coatings with TCOs are usually applied by means of high vacuum techniques such as sputtering. For patterning of the TCO coatings additional cost-intensive process steps are necessary, for example photolithography and etching.
“We use the TCOs to produce nanoparticles with special properties,” explains Peter William de Oliveira, Head of the Optical Materials Program Division. “The TCO ink is then created by adding a solvent and a special binder to these TCO particles. The binder performs several tasks here: it not only makes the TCO nanoparticles adhere well on the substrate; it also increases the flexibility of the TCO coating: in this way, the conductivity is maintained even when the films are bent”.
The ink can be applied to the film directly by inkjet or gravure printing. After curing under UV light at low temperatures less than 130 degrees centigrade, the coating is completed.
The transparent, electronically conductive inks allow conductor tracks to be produced unproblematically even on a large scale by means of classic reel-to-reel processes. Initial trials at INM have been promising. The researchers all agree that the use of structured rollers will in the future allow large, structured conductive surfaces to be printed with a high throughput at low cost.
INM conducts research and development to create new materials – for today, tomorrow and beyond. Chemists, physicists, biologists, materials scientists and engineers team up to focus on these essential questions: Which material properties are new, how can they be investigated and how can they be tailored for industrial applications in the future? Four research thrusts determine the current developments at INM: New materials for energy application, new concepts for medical surfaces, new surface materials for tribological applications and nano safety and nano bio. Research at INM is performed in three fields: Nanocomposite Technology, Interface Materials, and Bio Interfaces.
INM – Leibniz Institute for New Materials, situated in Saarbruecken, is an internationally leading centre for materials research. It is an institute of the Leibniz Association and has about 220 employees.
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The above post is reprinted from materials provided by INM – Leibniz-Institut für Neue Materialien gGmbH. Note: Materials may be edited for content and length.
Special to the BBC at the CES – Dave Lee
If you’re in the business of making TV cabinets – look away now.
For the rest of you, feast your eyes on a remarkable innovation-in-progress. (Watch the Video below)
LG Display has been working on its fully flexible screen for some time now, but it’s at this year’s CES the BBC was given the exclusive first hands-on.
The screen can be rolled up and scrunched around, and the display is full HD.
The one I played with was 18in (45.7cm) corner to corner, but the team at LG say they’re aiming for screens that are 55in and beyond.
At that size they will be able to produce a screen quality of 4K, they say – that’s four times HD.
Right now, the resolution is 1,200 by 810 pixels.
How did they do it? Of course they wouldn’t share the precise details, but the crucial technological leap has been moving from LED TVs to OLED TVs.
The O stands for organic, and it removes the necessity of a back panel providing light to the screen. Therefore, it bends.
Why would you want a bendable TV? LG says it’s ideal for making displays, like in a shop, but also for people who no longer want to sacrifice an entire corner of a room to a television.
With a bendable screen like this, you can roll it up and pop it in a cupboard until you need it again.
Unfortunately – and you knew this bit was coming – LG isn’t able to say how much it would eventually cost, or indeed, when it will actually be sold at all. At the moment, the team is buried in the prototype stage.
“The larger prototype is expected in the near future. But as for a commercial product, we’re still planning the timing,” says KJ Kim, LG Display’s vice president of its marketing division.
That can be translated as it’ll be a while yet.
Because while the screen is remarkable, it suffers a few flaws.
The night-time demo we saw, with quick flashing lights, was designed to conceal the numerous “dead” pixels in the display.
Dead pixels are those that have been damaged, so instead of emitting the correct colour just get appear as a tiny empty square.
There were several dead pixels on the screen and, after I played around with it a bit more, several more emerged.
Right now, the screen can only be rolled up in one direction, which isn’t a limitation, really, but something they will need to suss out before it comes to market.
Also, it’s crucial to point out that the screen can be rolled, but not folded flat.
Folding it flat would permanently damage it, and therefore the screen doesn’t represent a chance for something many have lusted over for a while, an interactive video newspaper that feels just like the paper product.
But we’re getting there.
Imagine an electronic screen that looks and feels like paper that could connect to your smartphone. You can shift your longer readings and video viewing to this bendable screen, then roll it up and throw it in your bag when you arrive at your subway stop. This may sound like sci-fi, but Israeli researchers have actually found a way to develop such thin, flexible screens you can use on the go.
A new Tel Aviv University study suggests that a novel DNA nanotechnology could produce a structure that can be used to produce ultra-thin, flexible screens. The research team’s building blocks are three molecules they’ve synthesized, which later self-assembled into ordered structures. Essentially, the team has built the molecular backbone of a super-slim, bendable digital display. In the field of bio-nanotechnology, scientists utilize these molecular building blocks to develop cutting-edge technologies with properties not available for inorganic materials such as plastic and metal.
This could provide a solution to roughly 2 billion smartphone users who may not want the content they view to be confined to a pocket-sized screen. That’s because currently the size of smartphone screens makes it particularly hard to read more than a few hundred words at a time or watch videos without feeling like you’re on the tilt-a-whirl at Six Flags.
The number of people using mobile devices to view media is on the rise. According to Pew Research Center, 68 percent of smartphone owners use their phone occasionally to follow breaking news stories, and 33 percent do it frequently. Moreover, YouTube reports that 50 percent of its 4 billion video views per month are watched on a mobile device.
SEE ALSO: CES 2015: The Best Of Israeli Tech
The structures formed by the researchers were found to emit light in every color, as opposed to other fluorescent materials that shine only in one specific color. Moreover, light emission was observed in response to electric voltage — which makes this technology a perfect candidate for display screens.
The TAU researchers, who recently published their findings in the scientific journal Nature Nanotechnology, are currently building a prototype of the screen and are in talks with major consumer electronics companies regarding the technology, which they’ve patented. “Our material is light, organic and environmentally friendly,” TAU’s Prof. Ehud Gazit said in a statement. “It is flexible, and its single layer emits the same range of light that requires several layers today.” Moreover, fewer layers are better for consumers, he says: “By using only one layer, you can minimize production costs dramatically, which will lead to lower prices.”
Back to the good old newspaper display?
It’s important to mention that this technology is still in its early stages and a price tag for these screens remains unknown. What is clear, however, is that the desire to consume content on portable, large screens isn’t going away and consumer preferences are trending more and more toward bigger screens.
Ironically, people seem to be drawn back to the old newspaper display – thin, flexible, and capable of being rolled up; now, all of these features are turning digital.
Regardless of flexibility, the tendency to enlarge mobile screens was already evident last year. It is widely believed that sales of Apple and Samsung (500 million smartphone in 2014) were buoyed by their newest smartphone iterations which boast larger screens than past versions. Apple especially took note of this trend, releasing the iPhone 6 (4.7 inch screen) and iPhone 6 Plus (5.5 inches) simultaneously.
Photos and video: LG, U.S. Army RDECOM
Genesis Nanotechnologyo and l o 
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