Graphene - Page 6

Finding an alternative for ITO as a transparent electrode is one of the major flexible OLED challenges. A few days ago, The Faunhofer Institute FEP demonstrated an OLED device that has a graphene electrode, developed as part of project GLADIATOR.

The Fraunhofer developed the device in collaboration with Spain-based Graphenea, which supplied the CVD-produced monolayer graphene. Graphene-Info posted an interview with the project's coordinator who further explains the technology, why graphene is promising and what are the challenges that still has to be solved before graphene transparent electrodes can be commercialized.

The Faunhofer Institute FEP is going to demonstrate an OLED device that has a graphene electrode, developed as part of project GLADIATOR. The Fraunhofer developed the device in collaboration with Graphenea, which supplied the CVD-produced monolayer graphene.

This first demonstrator is a small OLED device. The partners in this project now aim to create a larger-sized OLED with an active area of 42 cm². They also plan to develop a fully-flexible transparent OLED, with an active area of 3 cm².

A collaborative Innovate UK project called Graphted was launched in April 2015 to evaluate the potential of graphene as a transparent electrode when dispersed in a polymeric matrix. The project will focus on graphene inks and aims to show evidence that they can be used in large-area devices such as OLEDs and OPVs.

The project is led by UK's PolyPhotonix, who's partnering with Applied Graphene Materials and the CPI. The project will begin by examining graphene's use in phototherapy medical devices - as Polyphotonic's first commercial product is the Noctura OLED sleep mask which helps patients with Diabetic Retinopathy.

Researchers from Germany's Goethe University discovered that graphene doped with boron atoms feature an intensive blue fluorescence - which means that this new material may prove to be useful in OLED devices.

The Boron doping changes the graphene in two ways. First of all, it shifts the fluorescence into the desirable blue spectral range. It also improve the capacity to transport electrons. The new material is reportedly not sensitive to oxygen and moisture, unlike most boron-containing graphenes.

FlexEnable (which was spun-off from Plastic Logic in February 2015) has joined the Graphene Flagship, the European $1 billion graphene research project. Last year Plastic Logic demonstrated the world's first display based on a graphene backplane (a 150-PPI active-matrix E Ink panel), and now we have some more details on the company's graphene OTFT goals.

That 2014 E Ink display used graphene as a transparent electrode. FlexEnable is still developing the technology, and now wants to use it in OLED displays and organic LCDs.

Researchers at the Swedish Umea University have shown that if you place semiconductors polymers on a layer of graphene, they transport electrical charges more efficiently than when the polymers are placed on a silicon substrate.

This discovery means that graphene can enable more efficient charge transport in organic electronics such as OLEDs or OPVs.

An LCD works by selectively blocking light from a backlighting unit (BLU, usually made from LEDs) using a crystal which changes its polarization-filtering when voltage is applied. An electrochromic device is similar in idea but more simple as they can be turned from being transparent to being opaque. These kind of displays haven't been commercialized successfully yet due to fragile materials and material mismatches with the electrodes.

But new research at Bilkent University shows that graphene can be used to create such a device that features high percentage optical modulation, optical tuning properties in the UV to infrared, good electrical conductivity with no material mismatches. The display is mechanically flexible.

Flexible OLED displays are quickly becoming a reality, and it is expected that starting from 2015 we're going to start seeing foldable and eventually even stretchable OLEDs used in commercial devices. But for really flexible devices, all components must be flexible too.

While flexible batteries are already being developed, another possibility is to use a flexible supercapacitor. Researchers from MIT developed an extremely stretchable supercapacitor based on crumpled graphene paper.

In June 2013, Cambridge University and Plastic Logic announced a research collaboration that aimed to develop transparent graphene-based backplanes for flexible displays. Now, following this collaboration, Plastic Logic demonstrated the world's first flexible display that uses a graphene backplane.

The first prototype is a 150 PPI active-matrix E Ink display, in which the electrodes were made from solution-processed graphene (patterned after deposition) in a low-temperature (less than 100 degrees Celsius) process. The UK Technology Strategy Board recently gave a grant towards this research, with an aim to develop full-color OLED displays within the next 12 months.

Update: It turns out that the researchers did not fabricate an OLED lighting panel, but a small monochrome (green) OLED device.

Researchers from Philips, Graphenea and the University of Cambridge developed a new graphene-based transparent electrode that outperforms ITO in OLED devices.

Graphene by itself is not a good electrode material because the concentration of the charge carriers is low - which means that you need to dope it with excess carriers - while leaving it flexible and transparent. To achieve that, the team used a metal oxide film (molybdenum trioxide, MoO₃) as an intermediate layer between the graphene and the OLED layers. The work was performed as part of the EU project GRAFOL, aimed at roll-to-roll mass production of graphene.