1,720,997 research outputs found
Titania nanotube-silver phosphate hybrid heterostructure for improved visible light induced photocatalysis
No full textSelf-organized Titania nanotubes grown on a titanium foil by anodization is loaded with Ag3PO4 using
successive ionic layer adsorption and reaction method. The hybrid heterojunction nanostructure film
thus prepared is investigated for visible light induced photocatalytic decomposition of azo-dye and compared
with the bulk Ag3PO4 film deposited on a Ti-substrate. The results demonstrate that the hybrid heterostructure
exhibits much better photocatalytic performance due to the higher photostability.115141sciescopu
Minimizing Trap Charge Density towards an Ideal Diode in Graphene–Silicon Schottky Solar Cell
No full textPhotovoltaic
device performance of graphene/n-Si Schottky diodes is largely affected
by inhomogeneous oxide formation at the interface that suppresses
the tunneling current of injected and photoexcited charges. The accumulated
trap charges at low current induce charge recombination at the interface
and degrade the ideality factor of the diode and the fill factor (FF)
of the solar cell. This consequently gives rise to a nonlinear current–voltage
(I–V) feature in solar cells,
commonly known as an S-shaped kink, which can be engineered by optimizing
the interface barrier thickness or by increasing the carrier mobility.
Here, we present chemical and electrochemical doping methods to increase
the conductivity of graphene that transforms nonlinear kink photodiodes
with a low FF and solar cell efficiency towards trap-free linear photovoltaic I–V. Space-charge-limited-current
manifested Ohmic I–V diode
behavior with enhanced conductance in graphene by injecting homogeneous
ionic liquid; confirming the significant reduction of trap charge
density. This was further congruent with the disappearance of the
nonlinear kink in photodiodes with a high FF and nearly ideal diodes.
The solar cell efficiency obtained with our strategy is around 13.6%
and suggests possibilities to reach the theoretical limit of 19% by
tailoring parameters such as conductance of graphene, carrier density
of Si, and oxidation of the interfaces
Carrier multiplication in van der Waals layered transition metal dichalcogenides
Full text link© 2019, The Author(s).Carrier multiplication (CM) is a process in which high-energy free carriers relax by generation of additional electron-hole pairs rather than by heat dissipation. CM is promising disruptive improvements in photovoltaic energy conversion and light detection technologies. Current state-of-the-art nanomaterials including quantum dots and carbon nanotubes have demonstrated CM, but are not satisfactory owing to high-energy-loss and inherent difficulties with carrier extraction. Here, we report CM in van der Waals (vdW) MoTe2 and WSe2 films, and find characteristics, commencing close to the energy conservation limit and reaching up to 99% CM conversion efficiency with the standard model. This is demonstrated by ultrafast optical spectroscopy with independent approaches, photo-induced absorption, photo-induced bleach, and carrier population dynamics. Combined with a high lateral conductivity and an optimal bandgap below 1 eV, these superior CM characteristics identify vdW materials as an attractive candidate material for highly efficient and mechanically flexible solar cells in the future11sciescopu
Charge Transport in MoS2/WSe2 van der Waals Heterostructure with Tunable Inversion Layer
No full textDespite numerous studies on two-dimensional van der Waals heterostructures, a full understanding of the charge transport and photoinduced current mechanisms in these structures, in particular, associated with charge depletion/inversion layers at the interface remains elusive. Here, we investigate transport properties of a prototype multilayer MoS2/WSe2 heterojunction via a tunable charge inversion/depletion layer. A charge inversion layer was constructed at the surface of WSe2 due to its relatively low doping concentration compared to that of MoS2, which can be tuned by the back-gate bias. The depletion region was limited within a few nanometers in the MoS2 side, while charges are fully depleted on the whole WSe2 side, which are determined by Raman spectroscopy and transport measurements. Charge transport through the heterojunction was influenced by the presence of the inversion layer and involves two regimes of tunneling and recombination. Furthermore, photocurrent measurements clearly revealed recombination and space-charge-limited behaviors, similar to those of the heterostructures built from organic semiconductors. This contributes to research of various other types of heterostructures and can be further applied for electronic and optoelectronic devices. © 2017 American Chemical Society126281sciescopu
Leaf vein-inspired nanochanneled graphene film for highly efficient micro-supercapacitors
No full textInspired by natural vein-textured leaves, a 2D nanochanneled graphene film with high packing density and efficient ion transport pathways is proposed to facilitate high rate capabilities while maintaining high energy density. The 2D nanochannels serve as pathways for efficient ion diffusion parallel to the graphene planes in all-solid-state micro-supercapacitors with interdigitated electrode geometry. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim354011sciescopu
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Ferromagnetism in MnX2 ( X = S, Se) monolayers
No full textUsing density functional theory combined with Monte Carlo (MC) simulations, we show that the two dimensional (2D) MnS2 and MnSe2 sheets are ideal magnetic semiconductors with long-range magnetic ordering and high magnetic moments (3 mu(B) per unit cell), where all the Mn atoms are ferromagnetically coupled, and the Curie temperatures (T-C) estimated for MnS2 and MnSe2 by the MC simulations are 225 and 250 K, respectively, which can be further increased to 330 K and 375 K by applying 5% biaxial tensile strains.Chemistry, PhysicalPhysics, Atomic, Molecular & ChemicalSCI(E)[email protected]
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