1,720,991 research outputs found
Efficiency enhancement of P3HT:PCBM solar cells containing scattering Zn-Al hydrotalcite nanoparticles in the PEDOT:PSS layer
No full textIn this article we report on a new hybrid (organic-inorganic) composite material based on hydrophilic, electrically inert and semi-transparent hydrotalcite (HT) nanoparticles and a pHneutral formulation of PEDOT:PSS. The application of this composite material as electrically and optically active buffer layer in P3HT:PC61BM bulk heterojunction (BHJ) solar cells is reported. Two different synthetic routes are explored to obtain HTs having discoid shape, with a diameter of around 150- 200 nm and a thickness of ~20 nm, to be easily embedded in ~50 nm thick PEDOT:PSS films. The good affinity between HTs and the sulfonate groups of the PEDOT:PSS allows to obtain homogeneous HTs/PEDOT:PSS films, for HT concentrations of 0.25% and 0.50% by weight (vs. PEDOT:PSS). At these particle loads the electrical and morphological features of doped and undoped PEDOT:PSS films are nearly identical, while providing a significant effect on the visible light scattering properties of the composite films. We demonstrate ~12% improvement in power conversion efficiency (PCE) for P3HT:PC61BM solar cells incorporating HTs in the PEDOT: PSS layer, which mainly originates from increased shortcircuit current densities (JSC)
Efficient as-cast bulk-heterojunction solar cells based on a tert-butyl substituted methanofullerene acceptor
No full textWe report on the implementation of a modified methanofullerene PCBtB ([6,6]-phenyl-C(61) butyric acid tert-butylester) as electron acceptor for solution-processable bulk-heterojunction (BHJ) solar cells based on P3HT (poly(3-hexylthiophene)). The results demonstrate how a small modification of the steric hindrance of the benchmark molecule PCBM, leaving the electronic structure unchanged, significantly influences the main properties of the BHJ active layer. In particular, we investigate the effect of the replacement of the PC(61)BM methyl end-group with a tert-butyl substituent on the optical properties, OPV parameters, nanoscale morphology, D: A phase segregation, and charge carrier mobility in bulk-heterojunction with P3HT. We find that the PCBtB-based blends present a finer self-organization, higher D: A phase segregation and good charge carrier mobility, affording interesting photovoltaic responses and highlighting a marked potential of PCBtB to tailor the active BHJ layer. The best BHJ solar cells based on as-cast P3HT: PCBtB blend films exhibit power conversion efficiencies (PCEs) of similar to 3.1%, under a simulated AM1.5G illumination of 100 mW cm(-2), which are greater than the analogous as-cast P3HT: PCBM based devices
Innovative Multifunctional Silk Fibroin and Hydrotalcite Nanocomposites: A Synergic Effect of the Components
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Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Enhancing triboelectric performances of electrospun poly(vinylidene fluoride) with graphene oxide sheets
No full textPoly(vinylidene fuoride) (PVDF) is an easy processable and electroactive polymer, widely investigated for the preparation
of electrospun membranes for triboelectric nanogenerators (TENG). The presence of graphene oxide (GO) fllers into the
PVDF nanofbers, used as electroactive membranes in TENGs, has been reported to improve their performances as GO can
act as charge trapping site. Nevertheless, the addition of GO also afects the dielectric and rheological properties of the
spinning dispersions and the role of such parameters on the nanofber morphology has not been clarifed yet. In this work,
we investigated the efect of GO on the electrospinning process of PVDF–GO dispersions. In particular, we found that the
addition of GO in PVDF solutions modifes their rheological properties by increasing their viscosity and enhancing their
shear thinning behavior. Consequently, compared to the PVDF solution, the electrospinning process of PVDF–GO composite
solutions results in more homogenous and thinner nanofbers. Both PVDF and PVDF–GO nanofbers showed a similar fraction of electroactive PVDF β-phase, which was higher than 80%. This demonstrates that the relative content of β-phase is not
the main responsible for the observed improvement in TENG performances. Therefore, besides acting as a charge trapping
site, the presence of GO also shrinks the PVDF–GO fbers diameter, resulting in an electrospun membrane with increased
specifc surface area compared to the PVDF counterpart
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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