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Graphene shows great potential for flexible optoelectronic devices owing to its unique 2D structure and excellent electronic, optical, and mechanical properties. Chemical vapor deposition (CVD) is the most promising method for fabricating large‐area and high‐quality graphene films at an acceptable cost; therefore enormous efforts have been attempted to investigate the flexible optoelectronic devices based on CVD‐grown graphene. Here, recent advances and significant development of CVD‐grown graphene towards flexible optoelectronics including photodetectors, organic solar cells, and light‐emitting diodes are reviewed. Insight into the challenges of improvement of optoelectronic properties, work function tuning, as well as interfacial control of CVD‐grown graphene for high‐performance devices is provided. In particular, the availability to fabricate large‐area devices on the flexible substrates is discussed, which is crucial to drive the practical use of CVD‐grown graphene for future wearable optoelectronics. [ABSTRACT FROM AUTHOR]

Energy efficiency of data centers (DCs) is of great concern due to their large amount of energy consumption and the foreseeable growth in the demand of digital services in the future. The past decade witnessed improvements of the energy efficiency of DCs from an extensive margin—a shift from small to large, more efficient DCs. Improvements from the intensive margin, that is, from more efficient operation, would be critical in limiting the energy consumption and environmental impact of DCs in the upcoming period. Machine learning algorithms have advantages in optimizing the operation of DCs to improve energy efficiency as they have shown the potential of discovering control strategies not found by traditional method, and producing working condition‐dependent control strategies. This study proposes ready‐to‐use machine learning methods with practical details to decrease the most commonly used energy efficiency metric—power usage effectiveness in DCs. We achieved an accurate prediction by properly selecting the features used in the proposed prediction models established by neural network, light gradient boosting machine, recurrent neural network, and random forests. The proposed approaches are implemented in one of the largest hyperscale DCs in China—Tencent Tianjin DC, to optimize the set points of controllable variables in the cooling system and to detect and adjust the unreasonable working conditions in the modular data centers. The lower bound of PUE reduction was 0.005 with the proposed approaches, leading to about 1500 MWh (0.24% of the total designed electricity consumption of this DC) of energy saved per year in this hyperscale DC. The proposed methods have the potential to be transferred to DCs of similar scale, and the framework of our work could serve as a guide for machine learning‐based optimization of environmental indicators in other complex product/service systems. [ABSTRACT FROM AUTHOR]

Large‐area fabrication and stacking of various nanometer‐thick functional layers from solutions is essentially important for the construction of flexible thin‐film optoelectronic devices, but very challenging. The existing fabrication methods suffer from either non‐uniformity caused by the coffee‐ring effect or serious solution waste (excess of 90% for spin coating), and are hard to scale up and create stacks. Here, it is shown that centrifugal casting is a universal, scalable, and efficient method to fabricate uniform nanometer‐thick films and their stacks of various materials. The coffee‐ring effect is effectively suppressed, the solution utilization ratio is higher than ≈61%, and the films/stacks show a smooth surface/high‐quality interface. Using this method, flexible quantum dot light‐emitting diode displays with uniform luminance in a large lighting area of ≈115 cm2 that have not been achieved even on rigid substrates by the existing methods, are realized. This efficient and low‐cost solution processing method paves a way for large‐area fabrication of various flexible thin‐film optoelectronic devices. [ABSTRACT FROM AUTHOR]

In human body, alveoli are the primary sites for gas exchange which are formed by the dilation and protrusion of bronchioles at the end of the lung, and the rapid gas‐exchanging process in the alveoli ensures normal life activities. Based on the unique structures and functions of alveoli, it is necessary to study the regulation mechanism of its formation, respiration, and apoptosis. Herein, a class of reversible addition−fragmentation chain transfer (RAFT)‐derived amphiphilic triblock copolymers, PEO‐b‐P(DEAEMA‐co‐FMA)‐b‐PS is designed and synthesized. Due to the amphiphilic and gas‐responsive segments, these triblock copolymers can self‐assemble in aqueous solution and undergo the morphological transition from nanotubes to vesicles under gas stimulation; meanwhile, in the cycles of CO2/O2 stimulation, these vesicles can further realize the volume expansion and contraction, eventually rupture. The gas‐driven morphological transformations of these aggregates successfully imitate the formation, respiration, and apoptosis of alveoli, and provide an essential basis for revealing the life phenomena. [ABSTRACT FROM AUTHOR]

To enhance adsorption of organic dyes like malachite green (MG) onto polymeric absorbents, we prepared carbon nanotube (CNT) filled polyaniline (PANI) composites with large surface areas by simply using entangled CNTs as porous frameworks during PANI polymerization. Adsorption behavior of the CNT/PANI composites in MG solutions was experimentally investigated and theoretically analyzed. The CNT/PANI composites exhibit much higher equilibrium adsorption capacity of 13.95 mg g−1 at an initial MG concentration of 16 mg L−1, increasing by 15% than the neat PANI, which is mainly attributed to large surface areas and strong CNT-PANI interactions of the composites. In addition, theoretical analyses indicate that the adsorption kinetics and the isothermal process of the composites can be well explained by using the Ho pseudosecond-order model and the Langmuir model, respectively. In light of their high MG adsorption and easy operation, the CNT/PANI composites have great potential as high-efficiency adsorbents for removal of dyes from wastewater. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 [ABSTRACT FROM AUTHOR]

Graphene is a potential nanofiller that can dramatically improve the properties of polymer-based composites at a very low loading. This article reviews the state-of-the-art progress in the fabrication, properties, and uses of polymer composites with different kinds of graphene fillers. The results so far reported in the literature indicate that graphene/polymer composites are promising multifunctional materials with significantly improved tensile strength and elastic modulus, electrical and thermal conductivity, etc. Despite some challenges and the fact that carbon naotube/polymer composites are sometimes better in some particular performance, graphene/polymer composites may have wide potential applications due to their outstanding properties and the availability of graphene in a large quantity at low cost. [ABSTRACT FROM AUTHOR]

Solution processed flexible organic solar cells (OSCs) are of interest due to their potential use as environmentally friendly, shapeable, or wearable energy. Such flexible devices require compatible transparent conducting electrodes (TCEs). The use of three‐layer graphene as a useful TCE for flexible OSCs is reported. The conformal coating of the graphene‐based TCE with good retention of performance was achieved using a bulk heterojunction (BHJ) active layer comprised of the non‐polymeric molecular (5Z,5′Z)‐5,5′‐[(5‴,5‴‴′‐{4,8‐bis[5‐(2‐ethylhexyl)‐4‐n‐hexylthiophen‐2‐yl]benzo[1,2‐b:4,5‐b′]dithiophene‐2,6‐diyl}bis{3′,3″,3‴‐tri‐n‐hexyl‐[2,2′:5′,2″:5″,2‴‐quaterthiophene]‐5‴,5‐diyl})bis(methanylylidene)]bis[3‐n‐hexyl‐2‐thioxothiazolidin‐4‐one] (BQR) donor and [6,6]‐phenyl‐C71‐butyric acid methyl ester (PC71BM) as the acceptor. This material combination enables thick BHJ junctions to be used so that the roughness of the graphene surface did not lead to shorted devices. The best graphene/poly(ethylene terephthalate) (PET) devices (PET/graphene/molybdenum oxide/BHJ/calcium/aluminum) show a photoconversion efficiency (PCE) of 5.8%, which while excellent was lower than that of a similar device architecture that used ITO/glass as the anode. The power losses of the graphene/PET‐based cells mainly resulted from absorption losses caused by the optical profile distribution in the device and the relatively high sheet resistance of the anode, leading to an 18% decrease in the short‐circuit current and lower fill factor, respectively. [ABSTRACT FROM AUTHOR]

Review: 279 refs. [ABSTRACT FROM AUTHOR]