1,720,956 research outputs found
Quantum Dot Photovoltaics
No full textRemarkable progress over the past decade in photovoltaics using solution-processed nanomaterials as light absorbers has placed colloidal quantum dot (CQD)-based devices on the map. As such, AgBiS2 CQDs have garnered significant attention as materials exhibiting a high absorptivity with environmentally benign alternatives to Pb-chalcogenide or Pb halide perovskite-CQDs. Yet, AgBiS2 CQD-based solar cells have gravely underperformed compared to Pb-containing devices, particularly in the metrics of charge carrier extraction from the AgBiS2 absorber, hence its relative mediocrity. To specifically address the extraction efficiency, a bulk heterostructure (QPB) interlayer at the CQD/polymer interface in AgBiS2 CQD solar cells, resulting in an increase of the power conversion efficiency (PCE), e.g., from 5.10% (an average PCE of 4.94 +/- 0.11%) to 6.78% (an average PCE of 6.59 +/- 0.11%) is deviced. The improved charge extraction at the hole-collecting interface is responsible for the superior performance, corroborated by high photocurrent (21.5 mA cm(-2)) and fill factor (67%). The QPB-interlayered solar cell also gives rise to outstanding durability of the devices, retaining above 95% of the original PCE for 5 months in ambient air. Our strategy based on an eco-friendly CQD/polymer could provide an effective route for next-generation optoelectronics with enhanced charge collection and durability.
Tailored Band Edge Positions by Fractional Ligand Replacement of Nonconductive Colloidal Quantum Dot Films
No full textThe tunable band edge position of colloidal quantum dot (CQD) films is a key part of efficient optoelectronic device design of various forms such as photovoltaics, light-emitting diodes, and photodetectors. An accurate estimation of shifts in the band edge position of CQD layers is still considered challenging, especially when the CQD films are nonconductive. Here, we investigate the effect of nonconductive CQD films on photo-electron spectroscopy (PES) and photoelectron yield spectroscopy (PYS). We demonstrate control of systematic band edge positions by fractional ligand replacement of nonconductive CQD film characterized with photoelectron yield spectroscopy and density functional theory calculations. As-synthesized CQDs with insulat-ing oleate ligands were fractionally replaced with trans-3,5-difluorocinnamic acid molecules in a nonpolar solution. The fractionally replaced surface-bound ligands are quantitatively analyzed using 1H and 19F nuclear magnetic resonance (NMR) spectroscopy. We found that the energy levels of nonconducting CQD films shift linearly as a function of the number of bound trans-3,5-difluorocinnamates with specific dipole moments while retaining hydrophobic wettability.
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
Surface-Originated Weak Confinement in Tetrahedral Indium Arsenide Quantum Dots
No full textWhile the shape-dependent quantum confinement (QC) effect in anisotropic semiconductor nanocrystals has been extensively studied, the QC in facet-specified polyhedral quantum dots (QDs) remains underexplored. Recently, tetrahedral nanocrystals have gained prominence in III-V nanocrystal synthesis. In our study, we successfully synthesized well-faceted tetrahedral InAs QDs with a first excitonic absorption extending up to 1700 nm. We observed an unconventional sizing curve, indicating weaker confinement than for equivalently volumed spherical QDs. The (111) surface states of InAs QDs persist at the conduction band minimum state even after ligand passivation with a significantly reduced band gap, which places tetrahedral QDs at lower energies in the sizing curve. Consequently, films composed of tetrahedral QDs demonstrate an extended photoresponse into the short-wave infrared region, compared to isovolume spherical QD films.
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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