The emerging carbon-based quantum dots have been attracting attention because of their tremendous potential for optoelectronic and biomedical applications, which is due to their unique and size-tunable optical properties, their ability to be functionalized, and their biocompatibility. Here, we report the facile one-step synthesis of highly fluorescent and amphiphilic n-doped graphitic carbon dots (N-GCDs) using a fumaronitrile (FN) precursor. An interesting property of the prepared GCDs is their near pH neutral dispersibility without refinement, which stands in contrast to reported methods. This finding indicates that our approach could lead to low-cost and efficient processability that is scalable and environmentally friendly. In addition, we find that our N-GCDs have high density of graphitic structure such as sp2-hybridized carbon and tiny amounts of defect by near-edge X-ray absorption fine structure (NEXAFS) results. Finally, to confirm the electro-optical behavior of N-GCDs on photovoltaic devices, we fabricate iPSCs consisting of ITO/PEIE/PTB7:PC71BM (+ N-GCDs)/MoO3/Ag. Using this effective approach, we demonstrate the highest conversion efficiency of ∼8.6% resulting from improved photoresponsibility and charge transport based on various charge and energy transfer dynamics. Also, we believe that the shape, size and functionality of these GCDs can be controlled using other chemical species to provide a variety opportunities for use in optoelectronics, biological applications, and sensors.

Recent development in mobile electronic devices and electric vehicles requires electrical wires with reduced weight as well as enhanced stability. In addition, since electric energy is mostly generated from power plants located far from its consuming places, mechanically stronger and higher electric power transmission cables are strongly demanded. However, there has been no alternative materials that can practically replace copper materials. Here, we report a method to prepare ultrastrong graphene fibers (GFs)-Cu core-shell wires with significantly enhanced electrical and mechanical properties. The core GFs are synthesized by chemical vapor deposition, followed by electroplating of Cu shells, where the large surface area of GFs in contact with Cu maximizes the mechanical toughness of the core-shell wires. At the same time, the unique electrical and thermal characteristics of graphene allow a ∼10 times higher current density limit, providing more efficient and reliable delivery of electrical energies through the GFs-Cu wires. We believe that our results would be useful to overcome the current limit in electrical wires and cables for lightweight, energy-saving, and high-power applications.

New soluble host materials with benzocarbazole and triphenyltriazine moieties, 11-[3-(4,6-diphenyl-[1,3,5]triazin-2-yl)-phenyl]-11H-benzo[a]carbazole and 11-[3'-(4,6-diphenyl-[1,3,5]triazin-2-yl)-biphenyl-4-yl]-11H-benzo[a]carbazole, were synthesized for highly efficient red phosphorescent organic light-emitting diodes (PHOLED). Hole-transporting benzocarbazole moiety and electron transporting triphenyltriazine moiety, which are severely twisted each other enhance the solubility of those materials in common organic solvent. The improved solubility from this molecular design could be due to a reduced π-π stacking interaction, which gives a very uniform film morphology after spin coating of those materials. As a result, we obtained highly efficient soluble PHOLEDs combined with an evaporated blue common layer structure. The resultant red PHOLED exhibited the maximum current efficiency as well as external quantum efficiency values up to 23.7 cd/A and 19.0%.

The impact of anode buffer layers (ABLs) on the performance of CdSe quantum-dot light-emitting diodes (QLED) with a ZnO nanoparticle (NP) electron-transport layer and 4,4′-cyclohexylidenebis[N,N-bis(4-methylphenyl)benzenamine] (TAPC) hole-transport layer was studied. Either MoO3 or 1,4,5,8,9,11-hexaazatriphenylene hexacarbonitrile (HAT-CN) was used as the ABL. The QLED with a HAT-CN ABL exhibited better luminance performance, while the ultraviolet photoelectron spectroscopy and hole-only devices indicated that MoO3 was a superior hole injector. These results suggest that the QLED with a MoO3 ABL suffered from a severe charge carrier imbalance. Therefore, electron injection through the ZnO NP layer must be improved to further enhance the QLED performance.