Green‐luminescent functional graphene quantum dots (GQDs) are prepared by a facile electrochemical approach. The GQDs are rich in oxygen‐containing functional groups and soluble in aqueous or organic ...media, facilitating further functionalization and various applications. Polymer photovoltaic devices using GQDs as a new type of electron‐acceptor material are also demonstrated.
Despite significant study, the precise mechanisms that dictate the efficiency of organic photovoltaic cells, such as charge separation and recombination, are still debated. Here, we directly observe ...efficient ultrafast free charge generation in the absence of field in annealed poly(3-hexylthiophene):methanofullerene (P3HT:PCBM). However, we find this process is much less efficient in unannealed and amorphous regiorandom blends, explaining the superior short-circuit current and fill-factor of annealed RR-P3HT:PCBM solar cells. We use transient optical spectroscopy in the visible and near-infrared spectral region covering, but not limited to, the previously unobserved and highly relevant time scale spanning 1 to 100 ns, to directly observe both geminate and nongeminate charge recombination. We find that exciton quenching leads directly (time scale less than 100 fs) to two populations: bound charges and free charges. The former do not lead to photocurrent in a photovoltaic cell; they recombine geminately within 2 ns and are a loss channel. However, the latter can be efficiently extracted in photovoltaic cells. Therefore, we find that the probability of ultrafast free charge formation after exciton quenching directly limits solar cell efficiency. This probability is low in disordered P3HT:PCBM blends but approaches unity in annealed blends.
The main goal of this article is to provide an overview of recent research in the area of cellulose nanomaterial production from different sources. Due to their abundance, renewability, high strength ...and stiffness, eco-friendliness and low weight, numerous studies have been reported on the isolation of cellulose nanomaterials from different cellulosic sources and their use in high-performance applications. This report covers an introduction to the definition of nanocellulose as well as the methods used for isolation of nanomaterials (including nanocrystals and nanofibers, CNCs and CNFs, respectively) from various sources. The web-like network structure (CNFs) can be extracted from natural sources using mechanical processes, which include high-pressure homogenization, grinding and refining treatments. Also, rod-like CNCs can be isolated from sources such as wood, plant fibers, agricultural and industrial bioresidues, tunicates and bacterial cellulose using an acid hydrolysis process. Following this, the article focuses on the characterization methods, material properties and structures. Encyclopedic characteristics of CNFs and CNCs obtained from different source materials and/or studies are also included. The current report is a comprehensive review of the literature regarding nanocellulose isolation and demonstrates the potential of cellulose nanomaterials for a wide range of high-tech applications.
A one‐step, self‐supported topotactic transformation approach for synthesizing electrochemically active Co3O4 needlelike nanotubes is reported. Used as the active material in the negative electrode ...of a rechargeable lithium ion battery, the Co3O4 nanotubes manifest ultrahigh Li storage capacity with improved cycle life and rate capability. These features are discussed in terms of the unique structure of the materials.
Die Buchreihe Linguistische Arbeiten (LA) trägt wesentlich zur aktuellen linguistischen Theoriebildung im Bereich der allgemeinen und einzelsprachlichen Linguistik bei. Veröffentlicht werden ...hochwertige Arbeiten, die aktuelle Fragestellungen bearbeiten und die Entwicklung der Sprachwissenschaft, synchron oder diachron, empirisch oder theoretisch orientiert, vorantreiben.
Three‐dimensionally “curved” NiO nanomembranes made using a simple fabrication technique followed by a thermal oxidation process are reported. As anode materials for lithium ion batteries, the curved ...NiO nanomembranes exhibit impressive results, i.e., ultrafast power rate (50 C), a high capacity of 721 mAh g−1 at 1.5 C, and a long lifetime of 1400 cycles, making them attractive for high power Li‐ion batteries.
Polymer morphology has proven to be extremely important in determining the optoelectronic properties in polymer‐based devices. The understanding and manipulation of polymer morphology has been the ...focus of electronic and optoelectronic polymer‐device research. In this article, recent advances in the understanding and controlling of polymer morphology are reviewed with respect to the solvent selection and various annealing processes. We also review the mixed‐solvent effects on the dynamics of film evolution in selected polymer‐blend systems, which facilitate the formation of optimal percolation paths and therefore provide a simple approach to improve photovoltaic performance. Recently, the occurrence of vertical phase separation has been found in some polymer:fullerene bulk heterojunctions.1–3 The origin and applications of this inhomogeneous distribution of the polymer donor and fullerene acceptor are addressed. The current status and device physics of the inverted structure solar cells is also reviewed, including the advantage of utilizing the spontaneous vertical phase separation, which provides a promising alternative to the conventional structure for obtaining higher device performance.
Recent advances in controlling the polymer morphology to improve device performance are reviewed in selected polymer‐blend systems, with the origin of the vertical phase separation addressed. The current status of inverted polymer solar cells is reviewed, including its advantage of utilizing the spontaneous vertical phase separation. Comparable efficiency to the conventional device structure renders the inverted configuration a promising alternative.
Tin nanoparticles encapsulated in porous multichannel carbon microtubes (denoted as SPMCTs) were prepared by carbonization of electrospun PAN−PMMA−tin octoate nanofibers fabricated using a ...single-nozzle electrospinning technique. This material exhibited excellent characteristics for lithium ion battery anode applications in terms of reversible capacities, cycling performance, and rate capability. Undertaking such a production configuration allows the long-existing problem of obtaining a high packing density of tin particles while retaining sufficient spare space to buffer the volume variation during lithium alloying and dealloying processes to be properly addressed. Furthermore, the porous carbon shell preserves both the mechanical and chemical stability of the function-active Sn metal, which also serves as a highly conductive medium allowing Li+ to access.
