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.
The GQDs were used as emitters in organic light-emitting diodes (OLEDs) to identify the quantum dots’ key optical properties. After carefully designing the layer configuration so that electron and hole injection could be balanced, the scientists constructed GQD LEDs exhibiting luminance of 1000 cd/m2, which is considered very high and well over the usual brightness of displays used in smartphones. Because of their thinness, GQDs may even be used to create a foldable paper-like display.
A team of scientists from Columbia, Seoul National University (SNU), and Korea Research Institute of Standards and Science (KRISS) reported the creation of an on-chip visible light source using graphene as a filament. Creating light in small structures on the surface of a chip is crucial for developing fully integrated 'photonic' circuits that do with light what is now done with electric currents in semiconductor integrated circuits.
The scientists attached small strips of graphene to metal electrodes, suspended the strips above the substrate, and passed a current through the filaments to cause them to heat up. The team refers to this design as 'the world's thinnest light bulb', a type of 'broadband' light emitter that can be integrated into chips and may pave the way towards the realization of atomically thin, flexible, and transparent displays, and graphene-based on-chip optical communications.
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.
Graphenea recently introduced large area monolayer graphene suspended over microcavities as a standard catalog product, that can be used for NEMS (Nanoelectromechanical systems) due to its reliance on small vibrating membranes, which are sensitive to tiny forces.
NEMS are entering mainstream technology through sensors and actuators in platforms as common as inkjet printers, accelerometers, displays, and optical switches. The membranes used in NEMS need to be lightweight and stiff, with a high Young's modulus. As such, graphene is a very promising candidate for applications that require ultrathin membranes with excellent mechanical properties.
Researchers from the University of Maryland found that intercalating (embedding) sodium ions in a reduced graphene oxide (rGO) network, printed with graphene oxide (GO) ink, can significantly improve its performance as a transparent conductor in displays, solar cells and electronic devices.
The scientists used cost-effective materials and production techniques to receive a highly scalable printed electronics system that produces relatively inexpensive and stable conductors. The team theorizes the increased stability is due to the natural oxidation of sodium along the edges of the printed networks which forms a barrier that prevents ion loss. Networks printed with the ink exhibit up to 79 percent optical transmittance and 311 Ohms per square of sheet resistance.
UK-based FlexEnable was spun-off from Plastic Logic in February 2015 with an aim to further develop and commercialize the company’s technology platform for organic thin film transistor (OTFT) arrays for flexible displays and ubiquitous sensing. Last month FlexEnable joined the graphene flagship, and announced plans to develop new use cases for graphene in flexible electronics.
I talked briefly to Mike Banach, FlexEnable's Technical Director, and he explained the company's graphene plans and goals. FlexEnable is not a material company - they do not aim to develop and produce graphene material. The define themselves as a applied process technology - what we call a graphene application developer, focused on the flexible electronics market.
Researchers at the University of Guangzhou, China, managed to improve the capacitance of supercapacitors by nearly 1000-fold compared with that of the laminated or wrinkled CVD graphene-film-based supercapacitors. To achieve this, the researchers integrated transparency into freestanding, flexible graphene paper (FFT-GP). These supercapacitors's capacitance is also about ten times better than previously reported values for transparent and flexible supercapacitors based on pure carbon materials. However, some carbon-based nontransparent supercapacitors still perform better than the FFT-GP-based transparent supercapacitor.
The improved performance is mainly based on the prism-like graphene building blocks that the FFT-GP is made of. The hollow structures of the graphene that give the material its transparency also provide additional space for chemical reactions to occur compared to other materials. Also, the aligned and interconnected prism-like structures provide a wide open path for ions and electrons to travel along and the good charge transport leads to an overall better performance.