1,720,958 research outputs found
Highly Stable and Efficient CsPbI3 Perovskite Quantum Dot Solar Cells with Chloride-Passivated SnO2 Quantum Dots ETL
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Increasing Photocurrent in Lead Sulfide Quantum Dots Solar Cells via Overpassing Active Layer Thickness Limitation
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Thermally Stable and Efficient Planar Perovskite Solar Cells through a Facile Surface Passivation Using a Novel IDTT-Based Small Molecule Additive
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Suppressed Degradation and Enhanced Performance of CsPbI3 Perovskite Quantum Dot Solar Cells via Engineering of Electron Transport Layers
No full textCsPbI3 perovskite quantum dots (CsPbI3-PQDs) have recently come into focus as a light-harvesting material that can act as a platform through which to combine the material advantages of both perovskites and QDs. However, the low cubic-phase stability of CsPbI3-PQDs in ambient conditions has been recognized as a factor that inhibits device stability. TiO2 nanoparticles are the most regularly used materials as an electron transport layer (ETL) in CsPbI3-PQD photovoltaics; however, we found that TiO2 can facilitate the cubic-phase degradation of CsPbI3-PQDs due to its vigorous photocatalytic activity. To address these issues, we have developed chloride-passivated SnO2 QDs (CI@SnO2 QDs), which have low photocatalytic activity and few surface traps, to suppress the cubic-phase degradation of CsPbI3-PQDs. Given these advantages, the CsPbI3-PQD solar cells based on CI@SnO2 ETLs show significantly improved device operational stability (under conditions of 50% relative humidity and 1-sun illumination), compared to those based on TiO2 ETLs. In addition, the CI@SnO2-based devices showed improved open circuit voltage and photocurrent density, resulting in enhanced power conversion efficiency (PCE) up to 14.5% compared to that of TiO2-based control devices (PCE of 13.8%).11Nsciescopu
Monodisperse Perovskite Colloidal Quantum Dots Enable High-Efficiency Photovoltaics
No full textBandtail broadening originating from increasing the polydispersity of colloidal quantum dots (CQDs) deteriorates opencircuit voltage (V-OC) and hinders charge-carrier transport in CQD photovoltaics. The development of colloidal synthetic routes has enabled preparing monodisperse perovskite CQDs (Pe-CQDs) that have attracted attention as promising absorbers in CQD photovoltaics. However, polar-antisolvent-based purification induces the dissolution and agglomeration of Pe-CQDs, resulting in an irregular size distribution. Consequently, the photovoltaic performance decreases because of the increase in Pe-CQD polydispersity. Here, we demonstrate the preparation of well-purified monodisperse CsPbI3-Pe-CQDs via size selection on the basis of gel permeation chromatography. Well-purified monodisperse Pe-CQDs exhibit improved photovoltaic performance and achieve a low Pe-CQD polydispersity. Furthermore, these Pe-CQDs show higher photoluminescence quantum yields, narrower full-widths at half-maximum, and lower Urbach energies, in comparison to irregular-sized Pe-CQDs without size selection. Therefore, CsPbI3-Pe-CQD solar cells comprising monodisperse Pe-CQDs show the highest power conversion efficiency (15.3%) and V-OC (1.27 V) among the fully inorganic CsPbI3-Pe-CQD solar cells reported so far.11Nsciescopu
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
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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