1,720,959 research outputs found
Tracking and Extraction of Charge Carriers through Dissociation of Excitons in Cesium Lead Halide Perovskite Using Tin Dioxide
No full textLead halide perovskites are governing interest in optoelectronics owing to their superior photophysical properties. The performances in the device depend on the extent of charge carrier extraction and separation of excitons; however, because of the complicacy of the device architect, the real-time monitoring of the charge carrier is challenging. In this work, by employing the steady-state and time-resolved techniques in terms of optical absorption and photoluminescence (PL) measurements, the exploration and deciphering of the photoexcited charge carrier extraction from cesium lead bromide (CsPbBr3) perovskite using tin dioxide (SnO2) as an electron transporting layer is reported. Adopting the thermal evaporation method, a homogeneous qualitatively controlled ∼15 nm-thick CsPbBr3 is fabricated on a previously made SnO2 on an indium-doped tin oxide (ITO) substrate. Steady-state PL implies quenching of CsPbBr3 luminescence in the presence of SnO2, which is further supported by the faster decay in time-correlated single photon counting measurements. The tracking of the charge carrier is directly probed by monitoring the ground-state bleach (GSB) dynamics in different side excitations through pump-probe measurement in femtosecond time resolution. The dynamics are fitted with exponential function, and the early rise in GSB is attributed to hot carrier cooling time. The following time constants represent charge extraction (when CsPbBr3 is measured with SnO2) and recombination. A faster time constant in lifetime values indicates fast charge extraction when the excitation is performed from the extracting layer side. The first-principles calculations using density functional theory (DFT) reveal significant charge rearrangement at the CsPbBr3/SnO2 interface, forming an internal electric field that drives carrier extraction. Our investigation highlights the simplest approaches to dissociation of the excitons and real-time tracking of charge carriers in thin-film perovskite and electron transporting layer interfaces.This research was conducted at King Abdullah University of Science and Technology KAUST, and I am deeply grateful for the support and access to state-of-the-art facilities. My sincere thanks go to Dr. Partha Maity from the Indian Institute of Technology Kanpur, and Dr. Simil Thomas and Prof. Omar F. Mohammed from KAUST for helping during data analysis and manuscript preparation. This work was funded by the University of Jeddah, Jeddah, Saudi Arabia, under grant no. UJ-24-DR-1104-1. The author expresses her sincere thanks and extends her appreciation to the University of Jeddah for the technical and financial support. Your invaluable resources and guidance have been greatly appreciated
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
Engineering and Photophysical Properties of Low-Dimensional Halide Perovskites
No full textLow-dimensional metal halide perovskite semiconductors have received considerable attention due to their low-temperature processability, defect tolerance, and strong quantum confinement; these attributes have led to applications in light emitting diodes (LEDs), solar cells, photodetectors, laser, and optical modulators. Among them, two-dimensional (2D) layered perovskites, in terms of Ruddlesden–Popper and Dion–Jacobson, have received incredible attention because of their stability and sustainability compared to their three-dimensional (3D) counterparts. Despite their great success in chemical synthesis, the thickness of the perovskite layers and ligand-free environment is desirable for optoelectronic applications and cannot be controlled through chemically grown structures. By mimicking the 2D multiple-quantum-well (QW) structure and using the thermal evaporation method, we could address the abovementioned limitations.
This dissertation is devoted to engineering and constructing novel CsPbBr3 perovskite-based artificial multiple quantum wells (MQWs) and controlling the thickness of the thin films. Chapter 1 highlights the introduction of low-dimensional halide perovskites. In Chapter 2, we successfully engineered three different types of band alignments and investigated their optical and photoresponse characteristics. Our results showed different band offsets in the conduction and valence bands, causing distinct optical and electrical properties. The hot carrier dynamics of asymmetric and symmetric CsPbBr3 MQWs are examined in Chapter 3. The time-resolved data demonstrated that sequential hot-electron transfer between the QW layers mediated the delayed hot carrier equilibrium in asymmetric MQWs; this was attributed to the decoupling of hot electron holes originating due to the electron transfer in the cascade band structure. In Chapter 4, we explore and discuss the charge extraction mechanism utilized by the quantum tunneling effect. The interfacial charge transfer processes in terms of charge separation and charge recombination dynamics were studied using TiO2 and Spiro-OMeTAD as electron and hole-transporting materials, respectively. The fabrication methodology, characterization, and performance in visible-light communication applications of various thicknesses of the CsPbBr3 thin films in the nanoscale size regime are examined in Chapter 5. In Chapter 6, the results are summarized; our facile approach and well-controlled study in perovskite-based MQWs facilitate future device applications with enhanced performance
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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