1,720,959 research outputs found
Materiali perovskitici per celle fotovoltaiche ad alta efficienza e basso impatto ambientale
No full textLa transizione verso la produzione di energia sostenibile richiede lo sviluppo e l'implementazione di materiali e tecnologie eco-compatibili per consentire l'utilizzo su larga scala di fonti di energia rinnovabili. Tra queste, l'energia solare emerge come una risorsa rinnovabile fondamentale, che spinge a compiere notevoli sforzi di ricerca verso metodi economici ed ecologicamente sostenibili per convertire la radiazione solare in energia elettrica. Questa tesi di dottorato si concentra sull'avanzamento delle tecnologie fotovoltaiche di nuova generazione, esplorando alternative sostenibili ai sistemi tradizionali basati sul silicio, con particolare attenzione ai semiconduttori ibridi organici-inorganici noti come perovskiti ad alogenuri metallici (MHPs). In effetti, le celle solari a base di MHPs hanno compiuto progressi impressionanti, con un'efficienza di conversione della potenza che è passata dal 3,8% nel 2009 al 26,7% entro il 2024, rendendole la tecnologia di celle solari a più rapida evoluzione fino ad oggi. Le MHPs, di formula generale ABX3, sono caratterizzate da una struttura tridimensionale in cui i cationi A (ad esempio, CH3NH3+, [CH(NH2)2]+, o Cs+) risiedono in cavità formate da ottaedri [B(X1/2)6]- che condividono gli angoli, dove B è tipicamente Pb2+, Ge2+, o Sn2+, e X è Cl-, Br-, o I-. Questi materiali (e, nello specifico, [CH3NH3]PbI3 o MAPI) presentano eccezionali proprietà optoelettroniche, come bandgap modificabili, elevati coefficienti di assorbimento, mobilità superiore dei portatori di carica e notevole tolleranza ai difetti, che li rendono una pietra miliare per ulteriori sviluppi nella comunità di ricerca sui materiali energetici. Nonostante questi progressi, le MHPs devono affrontare sfide critiche, tra cui la tossicità del piombo, l'uso di solventi pericolosi durante la lavorazione e la limitata stabilità termica e chimica. Questa tesi di dottorato affronta queste sfide studiando alternative sostenibili per i componenti chiave dei sistemi MHPs, come metalli B-site non tossici ed economici, solventi ecologici e additivi ecologici innovativi. In particolare, due diversi aspetti mirano a stabilizzare la formulazione di film sottili MAPI in un processo di deposizione in un unico passaggio: ii) la parziale sostituzione del piombo con lo stagno, in combinazione con solventi non tossici e processi di deposizione per Blade-coating in due step. Gli effetti di formulazioni complesse di perovskite - come le variazioni nelle dimensioni dei domini cristallini, la deformazione e la microdeformazione, l'orientamento cristallografico e le proprietà del bandgap - sono studiati nel contesto dello sviluppo di tecniche di stampa scalabili. Nel corso di questa ricerca, vengono esplorate nuove composizioni di perovskite e metodologie di lavorazione, oltre alla fabbricazione e all'ottimizzazione di dispositivi per celle solari. Le tecniche di XRD, GIWAXS, spettroscopia ottica, AFM e microscopia interferometrica hanno supportato la caratterizzazione approfondita dei film negli studi di correlazione con le prestazioni dei dispositivi. Questo approccio completo mira a far progredire la scalabilità e la commercializzazione delle tecnologie fotovoltaiche basate sulla perovskite, riducendo al contempo la tossicità in più livelli.The transition to sustainable energy production necessitates the development and implementation of eco-friendly materials and technologies to enable the large-scale usage of renewable energy sources. Among these, solar energy emerges as a pivotal renewable resource, driving significant research efforts toward cost-effective and environmentally sustainable methods for employing and converting solar radiation into electrical power. This PhD Thesis focuses on advancing next-generation photovoltaic (PV) technologies by exploring sustainable alternatives to traditional silicon-based systems, with particular emphasis on organic-inorganic hybrid semiconductors known as Metal Halide Perovskites (MHPs). Indeed, MHP-based solar cells have achieved impressive progress, with power conversion efficiencies increasing from 3.8% in 2009 to 26.7% by 2024, making them the fastest-evolving solar cell technology to date. MHPs, of general formula ABX3, are characterized by a three-dimensional framework in which A cations (e.g., CH3NH3+, [CH(NH2)2]+, or Cs+) reside in cavities formed by corner-sharing [B(X1/2)6]− octahedra, where B is typically Pb2+, Ge2+, or Sn2+, and X is Cl−, Br−, or I−. These materials (and, specifically, [CH3NH3]PbI3 or MAPI) exhibit exceptional optoelectronic properties, such as tunable bandgaps, high absorption coefficients, superior charge carrier mobilities, and remarkable defect tolerance, making them a cornerstone for further development within the energy materials research community. Despite these advancements, MHPs face critical challenges, including lead toxicity, usage of hazardous solvents during processing, and limited thermal and chemical stability. This Ph.D. Thesis addresses these challenges by investigating sustainable alternatives to key components in MHP systems, such as non-toxic and cost-effective B-site metals, environmentally friendly solvents, and innovative green additives. In particular, two different aspects are aiming at stabilizing thin film MAPI formulation in a single step deposition process: ii) the partial substitution of lead with tin, in combination with non-toxic solvents in two-steps blade-coating deposition processes. The effects of complex perovskite formulations — such as variations in crystal domain size, strain and microstrain, crystallographic orientation, and bandgap properties — are investigated in the context of developing scalable printing techniques. Throughout this research, novel perovskite compositions and processing methodologies are explored, alongside the fabrication and optimization of solar cell devices. XRD, GIWAXS, optical spectroscopy, AFM and interferometric microscopy techniques supported the in-depth films characterization in correlation studies to the device performances. This comprehensive approach aims to advance the scalability and commercialization of perovskite-based PV technologies while reducing toxicity at multiple levels
Solvent Engineering for Scalable and Sustainable Fabrication of Lead‐tin Perovskite Solar Cells
Full text linkHybrid lead-tin (Pb-Sn) perovskites have emerged as a promising avenue for photovoltaic technology with reduced toxicity and optimized bandgap. However, scaling up Pb-Sn perovskite solar cells (PSCs) from laboratory to industrial scale involves tackling challenges associated with scalable preparation technologies and the sustainability of solvents, the latter representing by far the major component of the reactant mixture(s). Here, innovative low-toxic solvent mixtures are proposed for a two-step blade-coating deposition process of the active perovskite layer: initially, diethylformamide (DEF) and dimethylsulfoxide (DMSO) (in 9:1 volume ratio), for processing the inorganic components of hybrid Pb-Sn perovskites (first step); then, in a second step, isopropanol (IPA) and 2-methyl-2-butanol (2M2B) (in 3:2 volume ratio) for the organic components, promoting the diffusion of the organic cation and the full precursor conversion to perovskite. Employing this low-toxic solvent engineering, low-D/3D Pb-Sn perovskites are successfully prepared with a champion power conversion efficiency (PCE) of 14.2%. Additionally, the devices prepared with both solvent systems retain more than 90% of their initial PCE after storage under an inert atmosphere for ≈2 months. This study represents a significant step toward understanding industrial viability, where not only efficiency but also sustainability of the production process should be considered
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
Crystal Orientation, Strain, and Microstrain of Perovskite Films in a Complex Compositional Parameter Space
Full text linkThe chemical and functional stability issues of halide perovskite films integrated in solar cells are presently catalyzing large interest in the scientific community. Strategies are explored in which A-site doping and mixture of halides and incorporation of large organic cations (LOCs) and/or natural polymers are considered, often concomitantly. In this context, multiple parameters interfere with the crystallization process, and understanding the interplay of microscopic properties with the device stability and efficiency remains a challenging task. Herein, we screened the complex compositional parameter space of the FAxMA1-xPbI3 film series modified by LOCs [in the form of benzylammonium iodide (BzAI), 1,5-n-pentyldiammonium iodide (PDAI2), or 1,4-xylylendiammonium iodide (XDAI2)] and cornstarch incorporation. By combining GIWAXS, XRPD, and imaging analyses, we explore the influence of major constituents on the crystal structure, microstructure, and orientation and on the morphological film properties. By increasing the starch amount, the crystal structure and lattice strain of films are rather unaffected, whereas microstrain systematically rises, which explains the parallel optical band gap widening. By incorporating BzA and PDA cations, the films adopt the [100] orientation in comparison to the [110] of the LOC-free film (cubic notation), but increasing the starch amount induces a systematic crystal randomization in all formulations. These findings suggest a minor influence of texture and microstrain on the excellent photovoltaic performances of MAPbI3-based devices. In contrast, the surface compactness and optimal matching of film thickness and crystal domain size, all influenced by the starch additive, may play a favorable role. XDA incorporates into the 3D perovskite structure and greatly increases the air stability, providing a promising platform toward stable and flexible starch-based devices. This work demonstrates the importance of quantifying and correlating the micro- and macroscopic properties to deepen our understanding of the fundamental mechanisms of perovskite solar cells.</p
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
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