Efficiency Enhancement of Perovskite Solar Cells With Plasmonic Nanoparticles: A Simulation Study

Recently, hybrid organic-inorganic perovskites have been extensively studied due to their promising optical properties with relatively low-cost and simple processing. However, the perovskite solar cells have some low optical absorption in the visible spectrum, especially around the red region. In this paper, an improvement of perovskite solar cell efficiency is studied via simulations through adding plasmonic nanoparticles (NPs) at the rear side of the solar cell. The plasmonic resonance wavelength is selected to be very close to the spectrum range of lower absorption of the perovskite: around 600 nm. Both gold and silver nanoparticles (Au and Ag NPs) are selected to introduce the plasmonic effect with diameters above 40 nm, to get an overlap between the plasmonic resonance spectrum and the requested lower absorption spectrum of the perovskite layer. Simulations show the increase in the short circuit current density (Jsc) as a result of adding Au and Ag NPs, respectively. Enhancement in Jsc is observed as the diameter of both Au and Ag NPs is increased beyond 40 nm. Furthermore, there is a slight increase in the reflection loss as the thickness of the plasmonic nanoparticles at the rear side of the solar cell is increased. A significant decrease in the current loss due to transmission is achieved as the size of the nanoparticles increases. As a comparison, slightly higher enhancement in external quantum efficiency (EQE) can be achieved in case of adding Ag NPs rather than Au NPs

Petrology and geochemistry of the Late Miocene-Pleistocene volcanic rocks from Burgenland and SE Styria, Austria

Die vorliegende Doktorarbeit beschäftigt sich mit der Petrologie, Mineralogie und Geochemie alkaliner, mafischer Laven der westlichen Karpaten-Pannonischen Region (Carpathian-Pannonian Region; CPR). Diese Laven sind in kleineren Vulkanprovinzen im Burgenland (Pauliberg, Oberpullendorf) sowie im südöstlichen steirischen Becken (Klöch, Steinberg, Stradnerkogel, Waltrafelsen) aufgeschlossen. Die ältesten alkalinen, mafischen Vulkanite (Basalte des Burgenlandes) entstanden im Obermiozän (~ 11 Ma) während später Extensionsphasen. Die Hauptphase des Vulkanismus verbunden mit der Förderung alkaliner, mafischer Gesteine fand im Pliozän bis zum Quartär nach der Extension und zeitgleich mit der Kompression statt (z. B. steirisches Becken). Dieser in der gesamten Region auftretende Magmatismus folgte dem post-kollisionalen, kalkalkalinen, subduktionsbezogenen Vulkanismus der westlichen Karpaten. Bei den entnommenen Proben handelt es sich um Alkalibasalte, Basanite/Nephelin-Basanite und Nephelinite. Dabei können die geochemischen Charakteristiken der primitivsten mafischen Magmatite wichtige Hinweise zur Beschaffenheit der Mantelquelle(n) und den Schmelzbedingungen (Schmelztiefe, Aufschmelzgrad) liefern. Sie zeigen geochemische Signaturen der Ozeaninselbasalte (OIB) unabhängig von der geografischen Verbreitung sowie der relativ breiten Variation der chemischen Zusammensetzung. Ihre geochemischen Charakteristiken ähneln jenen der typischen anorogenen Intraplattenbasalte, die nicht durch Krustenkontamination und/oder subduktionsbezogene fluide Phasen/Schmelzen verändert worden. Die Mg# [Magnesiumzahl=100MgO/(MgO+FeOtotal)] der Alkalibasalte variiert zwischen 53 und 68, hauptsächlich jedoch > 62. Zudem ist keine negative Eu-Anomalie zu verzeichnen, was den Schluss zulässt, dass die meisten Magmen nur insignifikante Kristallfraktionierungen erfuhren und so die Zusammensetzung der Primärschmelzen wiederspiegeln. Spurenelementverhältnisse wie Zr/Nb, La/Nb und Ba/Th sowie isotopengeochemische Signaturen ähnlich denen der HIMU-OIB weisen auf die Entstehung der Primärschmelzen im asthenosphärischen Mantel hin, wobei die Interaktion mit der Lithosphäre während des Aufstieges der Schmelzen zur Erdoberfläche (en route) vernachlässigbar ist. Die Konzentration stark inkompatibler Elemente variiert und ist hoch. Hingegen zeigen die schweren seltenen Erdelemente (heavy rare earth elements HREE) nur geringe Gehalte. Es ist somit anzunehmen, dass die Schmelzen durch geringe Aufschmelzgrade im Stabilitätsfeld des Granat-Peridotits entstanden, wobei Granat als Residuum im Mantel verweilte. Die chemischen Variationen der Proben vom Pauliberg (Alkalibasalte und Basanite) deuten auf verschieden kleine Aufschmelzgrade derselben Mantelquelle hin. Die Basalte von Oberpullendorf ähneln hinsichtlich ihrer chemischen und isotopenchemischen Zusammensetzung den Saghey Basalten der „Kleinen ungarischen Ebene“. Die generell analogen Verteilungsbilder der Spurenelemente sowie die geringe Variation der Sr-Nd Isotopenverhältnisse der Laven des steirischen Beckens (Basanite/Nephelin-Basanite und Nephelinite) lassen auf eine ähnliche asthenosphärische Mantelquelle schließen. Die berechnete potentielle Manteltemperatur (Tp) der Pauliberg-Basalte beträgt 1386 °C, der Aufschmelzgrad liegt bei ~ 2 %. Analoge Berechnungen für die mafischen Gesteine von Klöch und Oberpullendorf weisen auf geringe Klinopyroxenfraktionierungen hin was zu einer Überschätzung der Temperaturen Tp (1466 °C bzw. 1530 °C) führt und die Berechnung des Aufschmelzgrades des Mantels bei der Entstehung dieser Primärschmelzen unmöglich macht. Die potentiellen Manteltemperaturen implizieren, dass es keine thermische Anomalien während der Bildungen und dem Aufstieg der Magmen gegeben hat. Überdies repräsentieren die geringen Volumina der eruptierten basaltischen Laven ebenfalls kleine Aufschmelzgrade, was bedeutet, dass die Temperatur des asthenosphärischen Mantels klein und konsistent mit der mittleren, normalen Manteltemperatur war. Demzufolge wird die Aktivität eines Manteldiapirs während der Entstehung der Schmelzen ausgeschlosse.The present PhD thesis deals with petrology, mineralogy and geochemistry of alkaline mafic lavas from the western part of the Carpathian-Pannonian Region (CPR). They crop out in small volcanic centres at Burgenland (Pauliberg, Oberpullendorf) and southeastern Styrian Basin (Klöch, Steinberg, Stradnerkogel, Waltrafelsen). The oldest alkaline mafic volcanism (Burgenland basalts) in the CPR occurred in Late Miocene (~11 Ma) during the late stages of extension whereas the peak of the alkaline mafic volcanism took place during the Pliocene to Quaternary post-dating the extension and coeval to the compression phase (.e.g. Styrian Basin). This type of magmatism subsequently occurred throughout the region following the post-collision calc-alkaline subduction-related volcanics in the western Carpathians. The sampled volcanic rocks comprise alkali basalts, basanites/nepheline-basanites and nephelinites. Among them the most primitive mafic magmatic rocks have geochemical characteristics that can provide important constraints on the nature of their mantle source(s) and the melting conditions (depths and degrees of partial melting). They exhibit ocean island basalts (OIB)-like geochemical signatures, despite their locally different geographic distribution and relatively wide range of variation in chemical compositions. Their geochemical characteristics resemble those of typical intra-plate anorogenic basalts which were not modified by contamination with crustal material and/or subduction-related fluids/melts. The Mg# [Mg-number=100MgO/(MgO+FeOtotal)] of the alkaline basalts varies from 53 to 68 but it is mostly >62 and they lack a negative Eu anomaly suggesting that most of these rocks have experienced insignificant crystal fractionation and approach primary magma compositions. The trace element ratios like Zr/Nb, La/Nb and Ba/Th and the isotopic compositions akin to HIMU-OIB suggest an origin of the primary magmas in the asthenospheric mantle with negligible interaction between magma and lithosphere en route to the surface. The concentrations of highly incompatible elements are variable and high whereas the heavy rare earth element (HREE) concentrations are low suggesting variable small degrees of partial melting in the garnet peridotite field with garnet remaining in the residue. Chemical variation within Pauliberg locality (alkali basalts and basanites) suggest variable small degrees of melting from the same asthenospheric mantle source whereas Oberpullendorf basalts have chemical and isotopic characteristics similar to Saghegy basalts of the Little Hungarian Plain. The general similarity of the trace element distribution patterns and the narrow range of the Sr-Nd isotopic ratios of the Styrian Basin lavas (basanites/nepheline-basanites and nephelinites) might suggest a similar asthenospheric mantle source. The calculated mantle potential temperature (Tp) for the Pauliberg basalts is 1386 oC and a melt fraction of ~2%. Analogous calculations for the Klöch and Oberpullendorf mafic rocks indicate minor clinopyroxene fractionation which leads to an overestimate of the mantle Tp (1466 oC and 1530 oC respectively), making it unfeasible to calculate the degree of partial melting involved in the genesis of the primary magma. These Tp calculations imply that these magmas arose from mantle at ambient temperatures without any indication of thermal anomaly. In addition, they represent small degrees of melting and hence small volumes of the basaltic lavas erupted and low eruption rates suggesting that the asthenospheric mantle Tp was low as well as consistent with ambient mantle temperatures. Accordingly, the mantle plume activity can be excluded from their origin

The infiltration of silver nanoparticles into porous silicon for improving the performance of photonic devices

Hybrid nanostructures have a great potential to improve the overall properties of photonic devices. In the present study, silver nanoparticles (AgNPs) were infiltrated into nanostructured porous silicon (PSi) layers, aiming at enhancing the optoelectronic performance of Si-based devices. More specifically, Schottky diodes with three different configurations were fabricated, using Al/Si/Au as the basic structure. This structure was modified by adding PSi and PSi + AgNPs layers. Their characteristic electrical parameters were accurately determined by fitting the current–voltage curves to the non-ideal diode equation. Furthermore, electrochemical impedance spectroscopy was used to determine the electrical parameters of the diodes in a wide frequency range by fitting the Nyquist plots to the appropriate equivalent circuit model. The experimental results show a remarkable enhancement in electrical conduction after the incorporation of metallic nanoparticles. Moreover, the spectral photoresponse was examined for various devices. An approximately 10-fold increment in photoresponse was observed after the addition of Ag nanoparticles to the porous structure

Truncated Sequences of Influenza Subtype H5 Haemagglutinin for Vaccination and Diagnostic Purposes: Avian influenza, Yeast expression, Peptide vaccination, recombinant Elisa

The highly pathogenic Avian Influenza subtype H5N1 can lead to 100 % mortality in chickens. The main issue in prevention of H5N1 is the development of efficient poultry vaccines. Influenza haemagglutinin (HA) derived recombinant polypeptides would not elicit an immune response against internal viral proteins. Thus HA polypeptide use facilitates differentiation between infected and vaccinated animals (DIVA). Serological tests using recombinant immune-dominant proteins devoid of non-specific moieties present in whole cell preparations might have higher sensitivity and specificity. In the present study, four non-overlapping sequences of different functional domains of influenza A virus subtype H5 virus (A / Thailand / 1 (Kan-1) / 2004) designated P1, P2, P5 and rHA1 were cloned and expressed in Pichia pastoris for vaccination and diagnosis purposes. The four polypeptides were expressed successfully in P. pastoris using peptone methanol (1 % (w/v) yeast extract, 2 % (w/v) peptone, 2 % (v/v) methanol). P1, P2 and rHA1 polypeptides were purified using nickel affinity chromatography, whereas, P5 was purified using lectin affinity chromatography. Correct expression was analysed by SDS-PAGE and western blot, glycosylation analysis and MALDI-TOF.The immune responses of P1, P2 and rHA1 polypeptides were assessed in BALB/C mice. To enhance antibody response, recombinant polypeptides were mixed with the Gerbu adjuvant and injected subcutaneously. Vaccination of mice induced high subtype specific antibody titres in mice as analysed by Elisa (using recombinant antigens or whole H5N1 antigen) and Immunofluorescence assay (IFA) performed on Vero cells infected with H5 (A / Thailand / 1 (Kan-1) / 2004). The immunogenicity of P1, P2, P5 and rHA1 polypeptides was determined in commercial layer chickens. Results showed that P1, P2 and rHA1 polypeptides induced high subtype specific antibody titres in chickens as analysed by Elisa (using recombinant antigens or whole H5N1 antigen), IFA (performed on Vero cells infected with H5N1 A / Thailand / 1 (Kan-1) / 2004) and microneutralization test (µNT). However, P5 polypeptide was not immunogenic in chickens. Neutralizing antibodies could be detected in chicken sera immunized with P1, P2 and rHA1 polypeptides as analyzed with microneutralization test. IgY was analysed in egg yolk of chickens immunized with recombinant polypeptides. The IgY of chicken immunized with P1 and rHA1, transferred to the egg yolk was proportional to maternal serum IgY. However, IgY could not be detected in egg yolk of chickens immunized with P2 and P5 recombinant polypeptides. The more immunogenic polypeptides P1 and rHA1 were used in an recombinant Elisa (rElisa) for detection of influenza A subtype H5 in chickens and duck sera.The optimal antigen for the concentrations of rHA1, P1 was 50 ng / well, 50 ng / well. Analysis of 25 positive sera and 25 negative sera to H5 antibodies revealed that, the sensitivity of Western blot, whole H5N1 Elisa, agar gel immunodiffusion test (AGID), P1-Elisa and rHA1-Elisa was 100 %, 100 %, 52 %, 80 % and 100 %, respectively, while the specificity was 100 %, 100 %, 100 %, 72 %, and 100 %, respectively. Moreover, duck sera, with haemagglutination inhibiting titer ranged from 4 - 8 log2, were tested positive by rHA1 Elisa compared with negative duck sera. Further analysis of 179 serum samples with rHA1-Elisa in comparison with haemagglutination inhibition (HI) and commercial Elisa proved to be highly sensitive and specific. The agreement ratio between rElisa and HI was 84.9 % and between commercial Elisa (Flock check) and HI was 76.5 %. In conclusion, P. pastoris may allow development of an effective recombinant influenza vaccine based on truncated sequences of HA that might provide broader protection against H5 influenza viruses. The possibilities to use rHA1, P1 and P5 recombinant polypeptides as a vaccine against H5 influenza should be further studied. Also our study demonstrates the potential utility of recombinant Elisa as a tool for improvement of serological diagnosis of influenza A subtype H5 in chickens and ducks.Die hochpathogene aviäre Influenza des Subtyps H5N1 erreicht beim Ausbruch von Infektionen in Nutzgeflügelbeständen Mortalitätsraten von bis zu 100 %. Effektive und kostengünstige Impfstoffe werden benötigt, die möglichst auch eine Differenzierung zwischen geimpften Tieren und mit Wild-Virus infizierten Tieren zulassen. In diesem Zusammenhang könnten Peptid-Vakzine eine mögliche Alternative zu den herkömmlichen Impfstoffen darstellen, bei denen unter Verwendung des Vollvirus Antikörper gegen mehrere Virusproteine induziert werden. Außerdem, könnten rekombinante Antigene in serologischen Tests zur Diagnose von H5 Virus in Nutzgeflügel eingesetzt werden. Von dem Einsatz spezifischer rekombinanter Antigene ist eine Verbesserung der Serodiagnostik zu erwarten. In dieser Arbeit, wurden vier verkürzte Sequenzen des Hämagglutinins (P1, P2, P5 und rHA1) von Subtyp H5 (A / Thailand / 1 (Kan-1) / 2004) rekombinant in Pichia Pastoris exprimiert. Dazu erfolgten zunächst eine Klonierung in der Expressionsvektor pAOX und die Transformation von Pichia Pastoris. Die Expression wurde durch Methanol induziert. Der Nachweis der rekombinanten Fusionspeptiden mit C-terminalen Histidin-Tag erfolgte durch SDS-PAGE, Western Blot, Glycolysierungsanalyse, und MALDI-TOF. Der Histidin-Tag ermöglichte die Reinigung von P1, P2 und rHA1 mit Metall-Affinitätschromatographie. Polypeptid P5 hingegen wurde mittels Lectin-Affinitäts- chromatographie gereinigt. Balb/c Mäuse wurden mit Polypeptid P1, P2 bzw. rHA1, versetzt mit Gerbu Adjuvans, immunisiert. Zur Untersuchung der Immunantwort wurden die murinen Seren mittels Elisa (unter Verwendung rekombinanter Antigene oder Voll-H5N1 Antigen) sowie IFA (durchgeführt in Vero- Zellen infiziert mit A / Thailand / 1 (Kan-1) / 2004) analysiert. Dabei wurde die präferentielle Induktion von H5-spezifischen Antikörpern detektiert. Die Immunogenität der P1, P2, P5 und rHA1-Polypeptide wurde in kommerziellen Legehennen bestimmt. Seren wurden mit ELISA, IFA, und Mikroneutralizationstest (μNT) analysiert. Die ELISA-Ergebnisse zeigten, dass die Polypeptide P1, P2 und rHA1 hohe Subtyp-spezifische Antikörpertiter in Hühnern induzierten. Im µNT konnte nur ein niedriger neutralisierender Antikörpertiter nachgewiesen werden. Das P5- Polypeptid ist bei Hühnern nicht immunogen. Im Eigelb von Hühnern, die mit den rekombinanten Polypeptiden P1 und rHA1 immunisiert wurden, konnten H5-spezifische IgY Antikörper detektiert werden. Hühner, die mit P2 und P5 immunisiert wurden, zeigten keine IgY im Eigelb. Die rekombinanten Antigene P1 und rHA1 wurden im ELISA auf ihre potenzielle Eignung für die Serodiagnostik untersucht. Die optimale Antigenkonzentration war 50 ng / well. Die serologische Analyse von 25 positiven und 25 negativen Seren auf Antikörper gegen H5 zeigte, dass Sensitivität und Spezifität von Western Blot, Voll-H5N1 ELISA und rHA1-ELISA bei jeweils 100 % lagen. Bei Agargel- Immunodiffusiontest (AGID) lagen Sensitivität und Spezifität bei 52 % und 100 %, während im P1-Elisa lediglich eine Sensitivität von 80 % und eine Spezifität von 72 % erreicht wurden. Somit eignet sich rHA1 für die Anwendung in der Serodiagnostik. Bei der serologischen Untersuchung von 175 Hühnerseren wurde eine Überbestimmung zwischen rHA1-ELISA und Hämagglutinationshemmungstest (HAI) 84.9 % festgestellt, während diese zwischen dem kommerziellen ELISA (Flock Check) und HAI 76.5 % betrug. Die Ergebnisse zeigten, dass das Expressionssystem P. pastoris als Produktionssystem rekombinanter Antigene für die Serodiagnostik von H5 Influenza geeignet ist. Challenge-Versuche sind nötig, um die Eignung von rekombinanten Antigenen als möglichen Impfstoff gegen H5 Influenza zu untersuchen

Critical Firm-based Enablers-Mediators-Outcomes (CFEMOs): A New Integrated Model for Product Innovation Performance Drivers in the Context of U.S. Restaurants

This study develops an original theoretical model of critical managerially controllable factors that have high potential for achieving significant improvements in the (intermediate and ultimate) outcome(s) of product innovation efforts. To this end, the author draws on the relevant empirical literature and integrates four complementary theoretical perspectives, namely; the critical success factors (CSFs) approach, the resource-based view (RBV), the input-process-output (IPO) model, and the system(s) approach. The model (hereafter CFEMOs) aims to explicate the simultaneous direct and indirect/mediated interrelationships among the product innovation’s critical firm-based enablers (new-product fit-to-firm’s skills and resources, internal cross-functional integration, and top-management support), process execution proficiency, and performance outcomes (operation-level performance, product-level performance, and firm-level performance). Additionally, it aims to predict the variations of the process execution proficiency and the performance outcomes. The CFEMOs model was empirically tested using an online survey that was completed by 386 U.S. restaurants owners/senior executives on their recently innovated new menu-items. By utilising a partial least squares structural equation modelling, the statistical analysis substantiated that, compared to the models of the extant relevant empirical studies, the CFEMOs model has a broader scope and a superior predictive power. It simultaneously explains 72% of the process execution proficiency, 67% of the new menu-item superiority (quality, speed-to-market, and cost-efficiency), 76% of new menu-item performance (customer satisfaction, sales, and profits), and 75% of the new menu-item contribution to the overall restaurant performance (sales, profits, and market share). Furthermore, this study established that those restaurateurs who concurrently succeed in enhancing their internal cross-functional integration, top-management support, and new-product fit-to-firm’s skills and resources, descendingly ranked, would achieve high process execution proficiency, which subsequently would grant them superior operation-level performance, product-level performance, and firm-level performance. This thesis concludes by providing several key original contributions and crucial implications to product innovation research and practice, as well as offering several promising avenues for future research.Egypt, the Egyptian Educational Bureau in London, South Valley University, Faculty of Tourism and Hotels in Luxor, Hotel Management Departmen

Comprehensive performance analysis of perovskite solar cells based on different crystalline structures of MAPbI 3

Perovskite solar cells (PSCs) have shown high optical absorption and consequently provide high conversion efficiency with stable performance. In our work, CH3NH3PbI3 (MAPbI3) as an absorber layer is analyzed for different crystalline structures. Cubic, tetragonal, and orthorhombic phases of perovskite material are investigated to check the impact of the crystalline structure on the solar cell performance. Both density of states and band structure are studied using Quantum-ESPRESSO package depending on density functional theory. Then, all relevant parameters were employed in SCAPS software and comprehensive study was done for examining the effect of the crystalline structure of perovskite layer on the solar cell performance. In-depth, analyses were conducted to evaluate key parameters, including open circuit voltage (Voc), short circuit current (Isc), fill factor (FF), and power conversion efficiency (PCE) considering the variations of perovskite layer thickness and bulk defect densities. The obtained results indicate that cells with cubic MAPbI3, which shows a notably higher bandgap of 1.7 eV and an enhanced optical absorption coefficient, especially in the higher wavelength range (around 105 cm−1), show better performance for almost all three scenarios. Cubic MAPbI3 cells achieve relatively higher peak efficiency of 26% when the absorber layer thickness is almost 900 nm. The investigation into absorber bulk defect densities reveals the critical role of defect levels in PSC performance. Adjusting defect levels from 1014 cm−3 to 1018 cm−3 results in deteriorating trends in Voc, Jsc, FF, and PCE. Jsc remains stable until a defect level of 1017 cm−3, highlighting a threshold where defects begin to impact charge carrier generation and separation. Doping effect has been studied, PCE remains stable until a critical doping level of 1016 cm−3 after which it drops significantly which indicates that doping is cautioned against due to its adverse effects on material and carrier transport. This finding holds significant promise for experimental solar cell fabrication, as it suggests that cubic MAPbI3’s superior bandgap and enhanced optical absorption could lead to more efficient and robust photovoltaic devices in real-world applications

Digital ethics in education: An examination of Omani information studies students’ ethical competencies during e-learning

Shifting to an e-learning style forced students to learn many skills and competencies to benefit from their experience in an e-learning environment. Ethical competencies play a crucial role in ensuring the fairness of students' assessments and the overall educational process. During the COVID-19 pandemic, the research used   a questionnaire to evaluate the ethical understanding of students enrolled in Sultan Qaboos University's Information Studies Department using a quantitative methodology. The findings of this study reveal a significant lack of basic ethical competencies among students in the e-learning environment which negatively impacts their educational experience. The responses obtained indicate a low level of awareness regarding ethical practices in e-learning   as well as a lack of knowledge concerning learning misconduct practices. The study suggests the implementation of an educational program that addresses academic ethical practices and e-learning misconduct across all educational levels. The outcomes of this research contribute to a better understanding of current e-learning practices among students, raise awareness about the importance of ethical competencies in e-learning   and provide guidance for students to develop ethical digital competencies