1,721,258 research outputs found
Shining light on hybrid perovskites for photoelectrochemical solar to fuel conversion
No full textHybrid halide perovskites (HaPs) represent a class of material with excellent optoelectronic properties providing distinct avenues for disruptive photo(-electro) catalytic technologies. However, their photocatalytic activity, selectivity and stability remains a scientific and technological hurdle. In this perspective, we discuss fundamental aspects of perovskite based photocatalytic systems, specifically for CO2 conversion and high value oxidation reactions, and highlight critical limiting factors and on-going challenges in the field. We critically assess the recent advances in designing halide perovskite hetero-interfaces and characterization methodologies which are often used to define the performance metrics. Furthermore, we outline important questions and identify emerging trends in relation to the remediation strategy towards improved photocatalytic performance and stability from halide perovskite semiconductors.S. S. acknowledges funding from the European Union’s Horizon Europe program under the Marie Skłodowska-Curie Grant Agreement No. 101067667. S. S. and V. J. acknowledge Catalisti VLAIO (Vlaanderen Agentschap Innoveren & Ondernemen) for their funding through the Moonshot SYN-CAT project (HBC.2020.2614), and the Belgian federal government through the Energy Transition Fund for T-REX project. NM would like to acknowledge the funding from the National Research Foundation (NRF), Singapore, under its Competitive Research Program (CRP) (NRF-CRP25-2020-0002). The authors would like to thank Dr Tom Aernouts and Prof. Bart Vermang for fruitful
discussions
Tunable electroluminescence for pure white emission from a perovskite-based LED
No full textRaw data for project titled "Tunable electroluminescence for pure white emission from a perovskite-based LED"</span
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
Signatures de l'injection optique et électrique de charges dans des monocristaux de rubrene
No full textThèse en anglaisOrganic single crystals are of particular fundamental interest as tools in probing the intrinsic electrical properties and the upper limit of performance for a given organic semiconducting molecule devoid of disorder. Rubrene single crystals are of particular interest in the field of organic electronics due to the high levels of charge carrier mobilities measured in transistors constructed of the same. In this thesis, we explore the properties of rubrene single crystal transistors. The photocurrent properties of rubrene single crystals are measured in ‘air-gap' transistors whose unique structure allows the measurement of photocarrier dynamics without the influence of a dielectric that can act as a source for traps. This structure has allowed us to identify phenomenon like persistent photoconductivity associated with the creation of oxygen related traps on the rubrene surface. Transient studies of the photocurrent reveal the presence of bimolecular recombination of the charge carriers. In addition, we have also performed optical spectroscopy studies including Raman spectra measurements which revealed the presence of endoperoxide related signature on the surface of the crystal while also confirming the low levels of intermolecular coupling present between the molecules. We have also explored the extrinsic factors that determine the surface conductivity of the rubrene crystal, particularly the presence of oxide related compounds on the surface of the crystal using XPS and photoluminescence measurements. The impact of photo-oxidation of the rubrene crystal on the surface conductivities were evaluated by a novel experiment involving the gradual photo-oxidation of the rubrene surface using a focussed laser. The creation of a deep acceptor state that can trap electrons indicates that the electrical properties of the rubrene surface like high unipolar p-type II conductivity and photoconductivity may be modulated by the presence of these oxygen induced states
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
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
Tunable Electroluminescence for Pure White Emission From a Perovskite‐Based LED
No full textHalide perovskite nanocrystals are a promising candidate for lighting applications. However, the production of white light emitting diodes (LEDs) is still a major challenge due to halide ion segregation. In this work, it is demonstrated that reducing the thickness of the perovskite layer in an LED stack can modulate the recombination zone, such that a tunable emission can be obtained. This comprises of an orange electromer emission from a hole-transport layer (HTL), green electroluminescence from the perovskite active layer, and a blue monomer emission from the same HTL. Overall, a pure white emission can be achieved after successful device optimization, which is particularly challenging for LEDs in which the emission originates solely from perovskite layer. It is anticipated that this methodology could be employed on any type of green-emitting nanocrystals to fabricate white LEDs.Nanyang Technological UniversityNational Research Foundation (NRF)P.V. acknowledges a NTU, Singapore Presidential Postdoctoral Fellowship via grant 04INS00581C150. The authors acknowledge financial support from the Singapore National Research Foundation, Prime Minister’s Office, through the Competitive Research Program (CRP Award No. NRF-CRP14-2014-03)
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