Graphene's optoelectronic properties enable electrically controlling light at the nanometer scale

Scientists from ICFO, MIT, CNRS, CNISM and Graphenea collaborated to demonstrate how graphene can enable the electrical control of light at the nanometer level. Electrically controlled modulation of light emission is crucial in applications like sensors, displays and various optical communication system. It also opens the door to nanophotonics and plasmonics-based devices. 

Graphenea and MIT electrically Controlled Energy Flow into Photons and Plasmons image

The researchers managed to show that the energy flow from erbium into photons or plasmons can be controlled by applying a small electrical voltage. The plasmons in graphene are unique, as they are very strongly confined, with a plasmon wavelength that is much smaller than the wavelength of the emitted photons. As the Fermi energy of the graphene sheet was gradually increased, the erbium emitters went from exciting electrons in the graphene sheet, to emitting photons or plasmons. The experiments showed the graphene plasmons at near-infrared frequencies, which may be beneficial for communications applications. In addition, the strong concentration of optical energy offers new possibilities for data storage and manipulation through active plasmonic networks.

Will graphene adaptation 'GraphExeter' replace ITO?

University of Exeter scientists discovered that GraphExeter, an adaptation of graphene, is durable to prolonged exposure to high temperatures and humidity. This makes the material not only a transparent, flexible and lightweight conductor, but a resilient one at that. The scientists predict major importance of this discovery for various electronic applications (and a possible ITO replacement).

GraphExeter material image

GraphExeter is a University of Exeter discovery, and is made of sandwiched molecules of ferric chloride between two graphene layers. It turns out that this creates a unique conductor with many useful traits, which is also now proving to be durable: the researchers found that it can withstand relative humidy of up to 100% at room temperature for 25 days, as well as temperatures of up to 150C or as high as 620C in vacuum.

Flexible transparent graphene electrodes may enable electronic tattoos

Researchesr from Korea's Ulsan, KAIST and ETRI institutes developed a process that produces flexible transparent graphene electrodes that can be attached to the skin (or any kind of delicate object). This could enable applications such as electronic tattoo-like stickers or bio-signal sensors.

Transprent graphene electrodes on skin photo

A graphene metal fiber composite ise used, which lowers the resistance of the transparent electrode to approximately 1/20th of existing ones. This enables the electrodes to be used in flexible displays or sensors. The new process is similar to a widely-used semiconductor process which means that this can be scaled commercially.

Graphene may enable electrochromic displays

Electrochromic displays are made from materials in which the transmittance of light to be adjusted by applying a voltage. These work similarly to LCDs by letting light from a backlighting unit (BLU) pass or not and so show desired images. These kind of displays haven't been commercialized successfully yet due to fragile materials and material mismatches with the electrodes.

Graphene electrochromic device examples (Bilkent University)

But this may change now, thanks to graphene. Researchers at Bilkent University developed a graphene electrochromic device that demonstrated 55% modulation and a broad spectral response. Both the electrode and the electrochromic device are made from graphene, and this enables a high percentage optical modulation, optical tuning properties in the UV to infrared, good electrical conductivity with no material mismatches. The display is mechanically flexible.

Plastic Logic and the CGC demonstrate the first graphene-based flexible display

In June 2013, Cambridge University's Graphene Centre (CGC) and Plastic Logic started to develop a transparent graphene-based backplane for flexible displays. Now Plastic Logic demonstrated the first display that was developed in that collaboration research. Plastic Logic says that this is the first time grpahene has been used in a transistor-based flexible device.

Plastic Logic and CGC graphene-based EPD prototype photo

The prototype (shown above) is an active-matrix electrophoretic (E Ink) display fabricated on flexible plastic. The electrodes are made from solution-processed graphene which was patterned after deposition with micron-scale features. The prototype has a pixel density of 150 PPI and was made at low temperatures (less than 100 degrees celsius). This is just a prototype of course and you can see many defects in display.

Graphene quantum dots prove highly efficient in emitting light

Researchers from the Korean's KAIST institute developed a new process to produce graphene quantum dots that are equal in size and highly efficient in emitting light. Quantum Dots potentially can be used to develop emissive flexible displays (similar to OLED displays), and this development may enable those displays to be graphene-based.

KAIST graphene quantum dots production process

The process involves mixing salt, water and graphite and then synthesizing a chemical compound between layers of graphite. All the resulting quantum dots were 5 nanometer in diameter, and these QDs do not contain and heavy metals (like current commercial quantum dots). The process is reportedly easy to scale and should not be expensive.

Cambridge researchers aims to make flexible, printed graphene-based cameras

The National Science Foundation of China (NSFC) awarded an 18-month Young International Researcher Fellowship to a University of Cambridge researcher that will look to se graphene materials composites for organic optoelectronic compounds. The researcher hope to use inkjet printers to produce those devices and then integrate them into displays, light detectors and gas sensors.

Printed graphene-based photo detector chip photo

In plain English, it means that they hope these kind of devices will enable flexible, cheap and fast cameras. Compared to current printed organic circuits, the graphene-based will be less sensitive to temperature and moisture and will also offer much faster response time that is suited for photodetection.


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