1,720,972 research outputs found
Molecular engineering of contact interfaces for high-performance perovskite solar cells
No full textMetal-oxide-based charge-transport layers have played a pivotal role in the progress of perovskite solar cells. Yet metal-oxide/perovskite interfaces are often highly defective, owing to both metal-oxide and perovskite surface defects. This results in non-radiative recombination and impedes charge transfer. Moreover, during operation, such interfaces may suffer from undesirable chemical reactions and mechanical delamination issues. Solving this multifaceted challenge requires a holistic approach to concurrently address the interfacial defect, charge-transfer, chemical stability and delamination issues, to bring perovskite solar cell technology closer to commercialization. With this motivation, we review and discuss the issues associated with the metal-oxide/perovskite interface in detail. With this knowledge at hand, we then suggest solutions based on molecular engineering for many, if not all, challenges that encumber the metal-oxide/perovskite interface. Specifically, in light of the semiconducting and ultrafast charge-transfer properties of dyes and the recent success of self-assembled monolayers as charge-selective contacts, we discuss how such molecules can potentially be a promising solution for all metal-oxide/perovskite interface issues
Recombination junctions for efficient monolithic perovskite-based tandem solar cells: Physical principles, properties, processing and prospects
No full textCrystalline silicon (c-Si) solar cells comprise more than 95% of the photovoltaics (PV) market. At wafer-scale, this technology is gradually reaching its practical power conversion efficiency (PCE) limit. Therefore, new performance-driven and scalable alternatives must be developed to further increase the cost-competitiveness of PV. Stacked PV absorbers with decreasing bandgaps in a tandem configuration utilize more efficiently the solar spectrum, and can thereby overcome the single-junction efficiency limit of conventional solar cells. Specifically, the monolithic, two-terminal tandem solar cell implementation promises a simple, yet high-performance technology with high market-relevance. Metal-halide perovskite absorbers have attracted broad interest in their application as the top cell of such a c-Si based tandem solar cell configuration. Practically, the perovskite and c-Si subcells need to be electronically coupled, where the interfacial structure should guarantee efficient charge recombination of majority carriers (collected from each subcell), without inducing minority-carrier recombination. In this article, we review the mechanism underlying efficient recombination junctions, and discuss available materials systems for perovskite-based tandems, as well as additional requirements such as efficient light coupling into the subcells, processing compatibility, scalability of materials and methods, and stability. We extend our discussion beyond c-Si to thin-film bottom cell technologies such as low-bandgap perovskites and chalcogenides. We conclude with an outlook on considerations for industrialization of such interfacial structures. This journal i
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
Eco-Friendly Spray Deposition of Perovskite Films on Macroscale Textured Surfaces
No full textAn innovative sequential eco-friendly spray coating (SEF-SC) technique is developed to uniformly deposit metal halide perovskite films on macroscale textured surfaces, such as textured crystalline-silicon wafers. Contrasting with previous work on spray-coated perovskite solar cells, the method presented in this work completely avoids the use of toxic and dangerous solvents. Both MAPbI3 and CsFAMAPbI3−xBrx perovskite films deposited by SEF-SC show excellent optoelectronic properties and no phase segregation, even when synthesized in ambient conditions. Uniform perovskite coatings are obtained on textured-silicon heterojunction solar cells underlining the promise of this method, which holds the potential for scalable wet processing of perovskites on rough substrates, such as for low-cost perovskite/silicon tandem solar cell fabrication
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
Photon recycling in perovskite solar cells and its impact on device design
No full textMetal halide perovskites have emerged in recent years as promising photovoltaic materials due to their excellent optical and electrical properties, enabling perovskite solar cells (PSCs) with certified power conversion efficiencies (PCEs) greater than 25%. Provided radiative recombination is the dominant recombination mechanism, photon recycling – the process of reabsorption (and re-emission) of photons that result from radiative recombination – can be utilized to further enhance the PCE toward the Shockley–Queisser (S-Q) theoretical limit. Geometrical optics can be exploited for the intentional trapping of such re-emitted photons within the device, to enhance the PCE. However, this scheme reaches its fundamental diffraction limits at the submicron scale. Therefore, introducing photonic nanostructures offer attractive solutions to manipulate and trap light at the nanoscale via light coupling into guided modes, as well as localized surface plasmon and surface plasmon polariton modes. This review focuses on light-trapping schemes for efficient photon recycling in PSCs. First, we summarize the working principles of photon recycling, which is followed by a review of essential requirements to make this process efficient. We then survey photon recycling in state-of-the-art PSCs and propose design strategies to invoke light-trapping to effectively exploit photon recycling in PSCs. Finally, we formulate a future outlook and discuss new research directions in the context of photon recycling
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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