OLEDs - Page 5

The OLED Association, a trade group that promotes OLED technologies, published an interesting article in which they give predictions for the OLED market. The Association sees Samsung returning to the OLED TV market in 2017, and those upcoming OLED TVs will use several new technologies - including graphene-based transparent electrodes.

Last month we reported that researchers at Korea's ETRI developed transparent graphene-based electrodes for OLED panels. The researchers say that these new electrodes improve the transparency and "image quality" of OLEDs by 40 to 60 percent, compared to current silver-based electrodes. The researchers aim to continue the research and improve the performance of their electrodes.

Researchers involved in the 10.6 million Euro European research project called GRAFOL have reportedly demonstrated a cost-effective roll-to-roll production tool capable of making large sheets of graphene on an industrial scale. The tool operates at atmospheric pressure and at reduced operating temperature, and is proclaimed by the researchers "the best route to low-cost manufacture".

Graphene-enhanced perovskite PV

The project team also believes that graphene could be used as a substitute for transparent indium tin oxide (ITO) electrodes used in organic LEDs (OLEDs), enabling flexible designs while helping reduce dependency on ITO. In addition, the team showed that it is possible to adapt the CVD method to grow graphene on 300 mm-diameter silicon wafers the standard size currently used in the semiconductor industry. That suggests the potential to integrate graphene in silicon photonics platforms, as well as flexible thin-film solar cells with transparent electrodes (like perovskite PVs, for example).

Researchers at Korea's ETRI (Electronics and Telecommunications Research Institute) developed transparent graphene-based electrodes for OLED panels. The researchers say that these new electrodes improve the transparency and "image quality" of OLEDs by 40 to 60 percent, compared to current silver-based electrodes.

The researchers explain that current metal (mostly silver) based electrodes have a limited viewing angle because of their internal light reflection, and the external light reflection affects the image quality. Graphene electrodes are more transparent and reduce the reflectance by 40-60 percent.

Graphene 3D Lab has announced filing a provisional patent for a process of 3D printing an OLED light source that immediately functions when printed, with a graphene coated transparent conductor window. This unique structure is the product of an innovative multi-functional 3D Printer, which can make thin films as well as 3D structures.

The printer patent relates to a technology that should lead the industry in multiple deposition techniques, robotic manipulator, laser and UV curing capabilities. G3L considers the new IP a dramatic leap forward, offering the ability to 3D print with multiple functional materials at the same time, including the ability to 3D print a working light. This printer was reportedly designed to maximize the attributes of the functional materials that the company already developed, and plans to introduce in the future to the market.

The Centre of Process Innovation (CPI) has announced that it will be part of a UK-based collaboration to develop the next generation of graphene-based ultra-barrier materials for flexible transparent plastic electronic based displays. The materials on which this work focuses on are required for the next generation of smartphones, tablets and wearable electronics and the twelve month project titled ‘Gravia’ will investigate the feasibility of producing graphene-based barrier films for next generation flexible OLED lighting and display products. 

The project combines the skills from each of the partners (University of Cambridge, FlexEnable Ltd, the National Physical Laboratory and the Centre for Process Innovation) and expects to deliver a feasible material and process system. It builds upon significant existing investments by InnovateUK and the EPSRC in this area. The resulting ultra-barrier material can be potentially used in a wide range of novel applications by the lead business partner, FlexEnable.

A few days ago we reported that the Fraunhofer Institute FEP will demonstrate an OLED device with a graphene-based electrode, as part of project GLADIATOR. The researchers hope that the graphene will enable devices that are highly flexible and stable. The CVD-produced monolayer graphene was produced by Graphenea, and the project that will run until April 2017 aims to produce larger demonstrators.

We had the good chance of talking to Beatrice Beyer, the project's coordinator at the Fraunhofer Institute, and she was kind enough to answer a few questions we had regarding the project and the technology they develop.

Q: Beatrice, thanks for your time. Can you explain to us how the graphene compares to ITO as an OLED electrode?

For the time being, the optoelectronic performance of graphene as a transparent electrode is still not as good as for the mature 'industry standard' ITO, but the performance and production technologies are continuously improving and we are optimistic that soon graphene based devices will reliably compete with ITO based on performance.

As part of project GLADIATOR, The Fraunhofer Institute FEP will show an innovative organic light emitting diodes (OLEDs) with a graphene-based electrode at Plastic Electronics 2015. The fabricated OLED on transparent graphene electrodes has been realized on a small area, and the target of the next one and a half years of the project is to successfully achieve large area OLEDs.

With graphene as an electrode, the researchers at the Fraunhofer FEP hope for flexible devices with higher stability. The electrode contains CVD-produced monolayer graphene of high quality, supplied by Graphenea, in order to compete with the reference material ITO (which graphene, in this case, replaces), the transparency and conductivity of graphene must be very high. Therefore, not only the process of electrode manufacturing is being optimized, but also different ways of doping graphene to improve its properties are being examined.

A collaborative Innovate UK project called Project Graphted that began on 1st April 2015 aims at evaluating Graphene’s potential as a transparent electrode when dispersed in a polymeric matrix. Graphted will be led by PolyPhotonix, a UK-based company that develops applications based on OLED lighting panels, and will include a 12 month feasibility study in which PolyPhotonix will be working in collaboration with Applied Graphene Materials and CPI (a UK-based R&D institute that helps companies develop and scale manufacturing processes).

The project seeks to provide proof of concept evidence that a Graphene-based electronic device can be successfully developed and fully categorised in terms of morphology and physical properties. If so, the approach holds potential to generate a range of electronic inks that can be utilised on a large scale. Application areas include OLEDs and organic photovoltaics (OPV).

Researchers from Korea Advanced Institute of Science and Technology (KAIST) have fabricated light-emitting diodes (LEDs) based on graphene quantum dots (GQDs). The researchers made pure GQDs using a cost-effective, scalable and environmentally friendly method that allows direct fabrication of GQDs using water, without surfactants or chemical solvents.

Those GQDs were then used as emitter material to create an OLED device.The scientists constructed GQD LEDs exhibiting luminance of 1000 cd/m2, which is well over the typical brightness levels of the portable displays used in smartphones.

Scientists at the Goethe University in Germany have developed a new class of organic luminescent materials through the targeted introduction of boron atoms into the molecular structures of graphene. The compound feature an intensive blue fluorescence and are therefore of interest for use in organic light-emitting diodes (OLEDs). 

A comparison of the new boron-containing nanographenes with an analogous boron-free material verifies the fact that the boron atoms have a great impact on two important properties of an OLED: the fluorescence shifts into the desirable blue spectral range and the capacity to transport electrons is substantially improved. currently, very limited use can be made of boron-containing nanographenes, since most of the exponents are sensitive to air and moisture. The scientists in this study claim that this problem does not occur with their materials, which is important with regard to practical applications.