Analysis of Degradation of Sb2Se3 Thin Film Solar Cells Deploying a Time-Dependent Approach Linked with 1D-AMPS Simulation

In this paper, we have developed a time-dependent model to study defect growth in the absorber layer of Sb2Se3 thin film solar cells. This model has been integrated with the AMPS-1D simulation platform to investigate the impact of increasing defect density at different positions within the Sb2Se3 layer on the electrical parameters of the solar cell. We adopted the Gloeckler standard model for thin films in AMPS to represent Sb2Se3 materials. The study focuses on tracking the degradation of device performance parameters as donor-like mid-gap states accumulate in the Sb2Se3 layer over time. We monitored the variation of key electrical parameters, including efficiency (η), fill factor (FF), open-circuit voltage (Voc), and short-circuit current (Jsc), at three different positions: the interface with CdS, the bulk of the Sb2Se3 layer, and the interface with the top contact. These positions are susceptible to increasing defect density during prolonged operation and irradiation. To pinpoint the most sensitive part of the Sb2Se3 layer to defect accumulation, we divided the layer into three sub-layers. Our simulation results highlight that the CdS/Sb2Se3 interface is the most vulnerable position in the cell when it comes to defect accumulation. The practical implication of this study is that special attention should be given to the CdS/Sb2Se3 interface during material deposition and the development of high-stability Sb2Se3 thin film solar cells.

Considering students’ abilities in the academic advising process

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. Academic advising is time-consuming work. At the same time, it needs to be efficient and productive in assisting the students to choose appropriate academic courses towards the completion of their selected programs in a beneficial manner. In addition, both private and public educational institutions are, currently, operating in an extremely competitive market and are, thus, faced with various challenges. Among these are the twin challenges of student retention and the rate of success in completion of their chosen academic courses. The mentioned challenges have a direct bearing on the quality of academic advising and services provided to the students, by the individual academic institution. A number of research studies have been carried out suggesting various online academic advising systems for undergraduate and graduate programs. In this context, we develop and present, here, an academic advising system which differs from and improves upon previously suggested methodologies with the inclusion of the facility to track individual students’ performance and, thus, ability in educational subjects and programs, taken in the previous academic terms. Our suggested methodology is based on the use of this facility to guide students in the selection of courses that they may register for the forthcoming academic term. We believe that the consideration of individual students’ past academic preformation, in our suggested methodology, is a significant improvement and will assist students in making more beneficial choices when registering for academic courses

A Molecular Dynamics Study of Water Confined In Between Two Graphene Sheets Under Compression

Several studies have demonstrated interest in creating surfaces with improved water interaction and adaptive properties because the behavior of water confined at the nanoscale plays a significant role in the synthesis of materials for technological applications. Remarkably, confinement at the nanoscale significantly modifies the characteristics of water. We determine the phase diagram of water contained by graphene stack sheets in slab form, at T=300 K, and for a constant pressure using molecular dynamics simulations. We discover that, as shown in the simulation, water can exist in both the liquid and vapor phases depending on the confining geometry and compressibility ratio. We also pay attention to how stable the interacting liquid is in relation to the pressure of compression that is perpendicular to the graphene sheets. To build this system and analyze its surface interface properties, we also used analytical and electronic scale modeling approaches. The impact of nanoconfinement on internal pressure may be seen in water, and this can be used to create interfacial materials for the creation of environmentally friendly solar cell materials. Our research highlights the intricate, seemingly random behavior of nanoconfined water—behavior that is difficult for graphene to understand. The results obtained offer crucial direction for system design and configuration of materials at the graphene/water interface that can be utilized as a benchmark for other future designs

Possibility of Complexation of the Calix[4]Arene Molecule with the Polluting Gases: DFT and NCI-RDG Theory

The calix[4]arenes (abbreviated as CX[4]) are characterized by a specific hydrophobic cavity formed by a four cyclically phenol groups to encapsulate a gas or small molecules. Recently, the CX[4] molecule is used in a specific media and in pharmaceutical drug delivery. The pollution problem will be a vital subject in the future because the increase of the explosions of the gaseous pollutants in the environment. In this report, we have encapsulated the polluting gases NO3, NO2, CO2 and N2 by the calix[4]arene molecule. In this work, The binding energies of the CX[4]-gas has been calculated including the BSSE (Basis Set Superposition Error) counterpoise (CP). The red-shift of the O-H bonding interactions obtained by adding the gas in the sensitive area of calix[4]arene is clearly explained by the infrared spectrum analysis. The Molecular electrostatic potential (MEP) of the stable CX[4]-gas complexes have been investigated in the endo-vs. exo-cavity regions. Finally, the non-covalent interactions analyses of the stable host-guests complexes have been estimated by using DFT calculations

Etude des défauts électriquement actifs dans les composants hyperfréquences de puissance dans les filières SiC et GaN

La demande croissante de composants permettant d\u27opérer à de fortes puissances, à hautes fréquences et à hautes températures a conduit au développement de filières électroniques à base de semiconducteurs à large bande interdite tels que le nitrure de gallium (GaN) et le carbure de silicium (SiC). Toutefois, la maîtrise encore imparfaite des matériaux en termes des défauts au sens large (impuretés, défauts cristallins) limite les performances des dispositifs à base de SiC et GaN. Dans ce travail de thèse nous nous sommes particulièrement intéressé à l\u27étude de deux dispositifs : les transistors MESFETs 4H-SiC et les HEMTs AlGaN/GaN/Si destinés à des applications hyperfréquences et puissance. L\u27étude des caractéristiques des sorties statiques de ces deux composants a révélé certains dysfonctionnements. Pour les MESFETs 4H-SiC, un effet d\u27hystérésis sur la conductance drain-source en fonction du sens de balayage de la tension de grille, un effet de kink et un décalage de la tension de seuil ont été mis en évidence. Une étude de défauts utilisant notamment la DLTS et la CDLTS, nous a permis de montrer que ces effets sont dus à la présence de défauts profonds dans la structure. Pour les HEMTs AlGaN/GaN sur substrat silicium (Si), un effet d\u27hystérésis, ainsi qu\u27un effet d\u27auto-échauffement ont été observés. Les mesures de CDLTS avec des impulsions sur le drain permis ont permis de mettre en évidence la présence de défauts étendus (dislocations) décorés par des pièges ponctuels

Etude du comportement et des microstructures de préimprégnés thermoplastiques à renforts tissés au cours du thermoestampage par bias-extension et microtomographie à rayons X

International audienc

Characterizations, defects and residual stresses induced during thermostamping of woven-fabric reinforced thermoplastic prepregs

Lors de leur mise en forme par thermo- estampage, les pré-imprégnés à matrice polymère thermoplastique et renfort fibreux tissé se déforment selon différents modes encore mal maîtrisés, dont les cisaillements plan et transverse, ce dernier traduisant la friction entre les plis tissés. Une fois formés, des contraintes résiduelles de fabrication sont également générées au cours du refroidissement des pré- imprégnés et altèrent leur stabilité dimensionnelle, tout comme les variations d’humidité relative. Dans ce travail, nous avons étudié ces deux aspects. Dans un premier temps, des essais de traction de biais ont été réalisés sur des pré-imprégnés de polyamide renforcés par des tissus de fibres de verre à hautes températures. L’analyse multi-échelle de la structure des échantillons déformés par tomographie à rayons X met en exergue des mécanismes de déformation des mèches de fibres dont certains ne sont pas pris en compte dans les modèles rhéologiques actuels. En outre, nous avons mis au point un dispositif pour l’étude du cisaillement transverse et la friction inter-plis. Les résultats obtenus montrent et quantifient les influences de la contrainte normale, de la vitesse de déformation et de la température sur le coefficient de frottement inter-plis. Un modèle de frottement basé sur le nombre d’Hersey est ensuite identifié. Dans un deuxième temps, l’exploitation de la mesure de la courbure globale des échantillons après refroidissement a permis d’estimer, via la théorie modifiée des stratifiées, les contraintes résiduelles et leur évolution avec les conditions hygrothermiques ambiantes.During their thermo-stamping, prepregs made of thermoplastic polymer matrices and woven fabrics are subjected to large deformation including in-plane and transverse shear, the last deformation mechanism being related to inter-ply friction. Once shaped, prepregs can still deform due to residual stresses induced by their cooling and/or hygrometric variations. In this work, we focused on these two aspects. Firstly, prepregs made of polyamide reinforced by layers of woven fabrics (glass fibre bundles) were subjected to bias extension at high temperatures. The fibrous structure deformed specimens was analysed with X-ray microtomography, allowing fiber bundles deformation mechanism to be emphasized.Some of them are not taken into account in current rheological model developed for prepregs. In addition, using a dedicated apparatus, we performed transverse shear tests to analyse inter-ply friction within prepregs. Experimental results underline the influence of the normal stress, the shear strain rate and the temperature on the interplay friction coefficient. A friction model based on the Hersey number is then fitted. Secondly, we measure the curvatures of deformed prepregs was to estimate, via the modified laminated theory, residual stresses and their variation with temperature and relative humidity