http://dspace.univ-mascara.dz:8080/jspui/handle/123456789/23 Sat, 04 Apr 2026 12:12:09 GMT 2026-04-04T12:12:09Z http://dspace.univ-mascara.dz:8080/jspui/handle/123456789/1304 Titre: Contribution à l'etude des propriétés physiques de quelques alliages d'Heusler via des méthodes de premiers principes Auteur(s): Abdelkebir, Bilal Résumé: Dans notre thèse, nous étudions la famille de matériaux à usages multiples appelés alliages half-Heusler. Notre étude vise à explorer les propriétés structurales, électroniques, élastiques et thermoélectriques des alliages half -Heusler de 1- ZrCo Ir Sb x x (x= 0, 0.125, 0.25, 0.375, 0.5, 0.625, 0.75, 0.875, et 1). Afin de prévoir ces différentes propriétés, nous avons effectué des simulations en employant la méthode des ondes planes augmentées linéarisées à potentiel complet (FP-LAPW), établie sur la théorie de la fonctionnelle de la densité (DFT) et mise en oeuvre à l'aide du code WIEN2K. Nos paramètres structuraux calculés sont en excellent accord avec les données théoriques et expérimentales, selon les propriétés structurales calculées grâce à les approximations GGA et LDA. Nous avons utilisé diverses approximations pour analyser les caractéristiques électroniques. Nous avons choisi l'approximation EV-GGA en particulier, car elle a produit la mesure de bande interdite la plus précise. Selon nos résultats, tous les alliages half-Heusler présentent des structures de bande de semi-conducteurs. Les valeurs de la bande interdite de ces composés, qui varient de 1.021 eV à 1.453 eV, indiquent qu'ils pourraient être utilisés dans l'optoélectronique. De plus, les constantes élastiques, le module de compressibilité B et le module de cisaillement G ont été calculés, indiquant la stabilité mécanique de nos alliages. En nous établissant sur la théorie du transport de Boltzmann semi-classique, le code BoltzTrap a été utilisé pour calculer les coefficients de transport, notamment la conductivité électrique, la conductivité thermique électronique et le coefficient de Seebeck. Conformément à l'équation de Slack, la conductivité thermique du réseau est traitée comme un paramètre thermoélectrique indépendant. Le paramètre de Grüneisen et la température de Debye sont calculés à l'aide du programme Gibbs. Ces résultats, qui soulignent l'efficacité des matériaux même à haute température, mettent en évidence leur potentiel d'application dans les dispositifs thermoélectriques. Mon, 29 Sep 2025 00:00:00 GMT http://dspace.univ-mascara.dz:8080/jspui/handle/123456789/1304 2025-09-29T00:00:00Z http://dspace.univ-mascara.dz:8080/jspui/handle/123456789/1253 Titre: Structure Stability and Optical Response of Complex Lead Perovskite: A Computational Approach to Modeling of Perovskite Solar Cells Auteur(s): Merah, Somia Résumé: This work presents a contribution to the study of the effect of bromide substitution on the structural, electronic, and optical properties of Rb₂AgSbCl₆ perovskite materials. To determine these different properties, we conducted simulations using the linearized augmented plane wave (FP-APW) method, which is based on density functional theory (DFT), employing the generalized gradient approximation (WC-GGA) to handle the exchange and correlation terms. The implementation of this method is carried out using the WIEN2K code. The calculated band gap energy for pure Rb₂AgSbCl₆ is approximately 2.08 eV, obtained using the modified Tran-Blaha (TB)–Becke Johnson (mBJ) exchange potential, which is in good agreement with experimental measurements. It was observed that the band gap values decrease as Br substitutes Cl at different concentrations of 25%, 50%, and 75%. Additionally, the band gap energy for Rb₂AgSbBr₆ was calculated, yielding a value of 1.34 eV. This study demonstrates that Br substitution enhances the hole and electron carrier mobility in pure Rb₂AgSbCl₆ compounds. Furthermore, optical analysis reveals that Br substitution improves the optical properties of Rb₂AgSbCl₆ by reducing transparency while enhancing the refractive index and absorption in the visible light region. By analyzing the Spectroscopically Limited Maximum Efficiency (SLME), the specific luminescent minority electron (SLME) of Rb₂AgSb(Cl₀.₅Br₀.₅)₆ was found to be 9.51%. Although this percentage is modest, it can be attributed to the indirect band gap nature of the material. Additionally, we calculated the thermoelectric properties, and the electronic properties indicate that these compounds are p-type semiconductors. Based on the obtained results, it is expected that the band gap, optical, and thermoelectric properties of Rb₂AgSbCl₆ perovskite can be effectively tuned by Br substitution at Cl sites, making Rb₂AgSb(Cl₁₋ₓBrₓ)₆ alloys promising candidates for optoelectronic and photovoltaic applications. Also we study the electronic properties of Rb₂AgSb₁₋ₓBiₓX'₆ alloys, where x takes values of zero, 0.25, 0.50, 0.75, and 1, with X′ representing Cl, Br, or I. Mon, 16 Jun 2025 00:00:00 GMT http://dspace.univ-mascara.dz:8080/jspui/handle/123456789/1253 2025-06-16T00:00:00Z http://dspace.univ-mascara.dz:8080/jspui/handle/123456789/1185 Titre: The effect of charge balance on the performance of photovoltaic materials Auteur(s): LARBI, Rekia Résumé: Renewable energy sources offer the only sustainable means to meet the growing global energy demand while minimizing contributions to anthropogenic climate change and environmental harm. Photovoltaics provide a way to capture the vast solar radiation that reaches the Earth daily and convert it directly into electricity. However, their widespread adoption has historically been limited by high production and deployment costs. Perovskite materials have attracted significant interest over the past decade for their potential in high- efficiency photovoltaic devices. Their chemical and structural flexibility allows materials scientists and engineers to tailor their properties to meet the specific requirements of various applications. In this thesis we use ab initio methods to explore the fundamental distortions in various structures and their corresponding optoelectronic properties. The research focuses on a selection of perovskites compound that are either central to current international photovoltaic studies or have the potential to emerge as significant materials in the field. The study addresses some of the key challenges facing current photovoltaic technologies and examines how newly developed materials, such as halide perovskites, have driven the search for alternatives that combine high efficiency with affordability, scalability, and flexibility for solar cell production. Specifically, this work investigates the Cs₂InBi(Br,Cl)₆, SF₃PbI₃, and (CsRb)(SnGe)I₆ perovskite compounds. Through the calculation of their electronic and optical properties, are able to assess their viability and potential as absorbers within photovoltaic devices. Sun, 09 Feb 2025 00:00:00 GMT http://dspace.univ-mascara.dz:8080/jspui/handle/123456789/1185 2025-02-09T00:00:00Z http://dspace.univ-mascara.dz:8080/jspui/handle/123456789/1169 Titre: Cours sur Les Techniques d’Analyses Physico-chimiques Destiné aux étudiants de Deuxième année licence en physique Quatrième Semestre Auteur(s): MOUCHAAL, Younes Mon, 30 Dec 2024 00:00:00 GMT http://dspace.univ-mascara.dz:8080/jspui/handle/123456789/1169 2024-12-30T00:00:00Z