1,721,045 research outputs found
Mechanochemical route to high-purity halide perovskites with real-time temperature tracking
Full text linkMechanochemical synthesis is a sustainable and scalable approach for producing halide perovskites, offering key advantages over traditional solution-based methods, such as solvent-free processing, improved stoichiometric control, and reduced toxicity. In this work, we present a detailed study on the mechanochemical synthesis of MAPbI3 and MAPbBr3, with real-time monitoring of temperature inside the rotating jar to optimize the grinding conditions. We find that the temperature increase primarily originates from mechanical impact rather than the exothermicity of the reaction and does not limit perovskite formation and quality. Ultra-pure MAPbI3 is readily obtained in under 10 minutes, while MAPbBr3 requires longer grinding times for complete conversion (30 min). Prolonged milling yields finer powders, which are essential for formulating well-dispersed, DMF-free inks. These inks enable the fabrication of perovskite films via slot-die coating under ambient conditions. Our findings highlight that real-time thermal diagnostics provides a valuable tool for optimizing mechanochemical synthesis protocols and the importance of powder refinement to achieve homogeneous films suitable for scalable optoelectronic applications
A Sustainable Hydrogel‐Based Dye‐Sensitized Solar Cell Coupled to an Integrated Supercapacitor for Direct Indoor Light‐Energy Storage
Full text linkThe rapid growth of the Internet of Things ecosystem has increased the need for sustainable, cost-effective energy sources for indoor low-power devices. Indoor photovoltaics offer a solution by harnessing ambient indoor lighting, with dye-sensitized solar cells (DSSCs) emerging as strong candidates for these applications. When it comes to indoor environments, there is an increased demand for nontoxic and nonflammable solvents for electrolytes. The use of water-based electrolytes is a promising way to address these issues, while ensuring the eco-friendliness and sustainability of these devices. Herein, a DSSC system is employed featuring an aqueous gel electrolyte composed of xanthan gum, a biosourced polymer, and an iodide/triiodide redox couple. The performances of the cells are characterized under LED lighting, reaching efficiencies up to 3.5% in indoor conditions, and then integrated with an electric double-layer capacitor, also based on a xanthan gum gel electrolyte, resulting in a fully aqueous device for indoor light-energy harvesting and storage with an overall photoelectric conversion and storage efficiency of 1.45%
Effect of a 2D-Modification of Cs2AgBiBr6 on Nucleation and Contact Formation of Subsequently Deposited Hole Transport Layers as Revealed by In Situ Growth Studies
Full text link: A two-dimensional (2D) perovskite interlayer prepared by modification of a three-dimensional (3D) perovskite absorber with organic ammonium ions such as butylammonium (BA+) or phenethylammonium (PEA+) between the 3D perovskite and contact layers is widely known to significantly improve the performance of perovskite solar cells. This has also been confirmed previously for the lead-free double perovskite absorber Cs2AgBiBr6. In this work, film growth of copper phthalocyanine (CuPc) or pentacene (Pn), used as model hole transport materials (HTM), was investigated. Mimicking solar cell geometry, the HTMs were evaporated onto thin films of 2D perovskites BA4AgBiBr8 or PEA4AgBiBr8, as well as on 3D Cs2AgBiBr6, either in its pristine form or after modification by BA+ or PEA+. The morphology and work function were inspected intermittently with respect to the evaporation of the HTMs by Kelvin probe force microscopy at different average film thicknesses. By these means, the origin of device improvements following a 2D-modification in contact with HTMs, as established earlier, was revealed by analyzing in detail the interface of the HTM with the respective perovskite starting at monolayer coverage and proceeding toward bulk thickness. On modified Cs2AgBiBr6, the energy alignment between the perovskite and the HTM was found to be well confined, and the growth of both HTMs was improved compared to pristine Cs2AgBiBr6. HTM growth occurred more homogeneously and led to layer formation, even at early stages of deposition. For CuPc as HTM, these changes were accompanied by preferential formation of needles in a crystal phase different from that formed on pristine Cs2AgBiBr6, as also detected on 2D PEA4AgBiBr8. Pn formed large dendritic islands on the 2D perovskites as well as on layered terraces formed upon ammonium modification of Cs2AgBiBr6, in contrast to the growth of small grains on pristine Cs2AgBiBr6. Implications of these observed changes in film growth and energy level alignment on the observed contact characteristics with the HTMs in model solar cells are discussed. Insight into the mechanism of improving perovskite-based devices by use of 2D/3D perovskite heterostructures is, thereby, provided by these measurements using CuPc or Pn as model HTMs
Tuning Surface Chemistry in 2D Layered BiOI by Facile Liquid‐Phase Exfoliation for Enhanced Photoelectrocatalytic Oxygen Evolution
Full text linkBiOI is a promising photoelectrocatalyst for oxidation reactions. However, the limited photoelectrocatalytic (PEC) activity necessitates the development of new strategies to modify its surface chemistry and thus enhance functional properties. Herein, we present a simple method to increase photocurrent in a BiOI-based photoanode by exfoliating microspheres of the oxyhalide produced through hydrothermal synthesis. Following exfoliation in isopropanol, the resulting layered BiOI-based colloid contains a greater variety of species, including Bi2O2CO3, I3−, IO3−, Bi5+, and hydroxides, compared to the original BiOI. These additional species do not directly enhance the PEC oxygen evolution reaction (OER) performance. Instead, they are consumed or converted during PEC OER, resulting in more active sites on the photoelectrode and reduced resistance, which ultimately improves the water oxidation performance of the exfoliated BiOI. Over long-term chronoamperometry, the exfoliated BiOI demonstrates a photocurrent twice as high as that of the BiOI microspheres. Analysis of the species after PEC OER reveals that the combination of IO3−, Bi5+, and I3− species on the BiOI is beneficial for charge transfer, thus enhancing the intrinsic PEC properties of the BiOI. This study offers new insights into the role of surface chemistry in determining PEC performance, aiding the optimization of 2D materials-based photoelectrocatalysts
Soft Batteries: Electrochemical Innovations for Sustainable Energy Storage
No full textResearch into soft energy storage materials is progressing rapidly with several applications in
healthcare and soft robotics. This chapter presents novel materials used across battery
components in next-generation designs, covering innovations in electrodes, electrolytes, and
separators, in addition with possible structural designs. It includes a collection of fundamentals
about Li-ion chemistry to clarify essential material selection criteria, alongside recent
developments in soft batteries utilizing alternative chemistries
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
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
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