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Die Verwendung ungiftiger Halbleiter-Nanokristalle für optoelektronische Anwendungen erfordert eine genaue Kenntnis deren physikalischer Eigenschaften. Die bisherige Forschung konzentrierte sich allerdings auf Materialien, die giftige Elemente wie Blei oder Cadmium enthalten. Für kommerzielle Anwendungen sind diese jedoch nicht geeignet. Daher wurden für diese Arbeit ungiftige Nanokristalle mittels optischer Spektroskopie untersucht. Somit konnten Vorteile und Herausforderungen für die Entwicklung von zukünftigen Bauelementen benannt werden. Kolloidale Quantenpunkte sind helle Lichtquellen, die in der nächsten Generation von Leuchtdioden Verwendung finden könnten. Im Gegensatz zu den Cadmium-basierten Varianten werden hier Kern/Schale-Quantenpunkte auf Indiumphosphid-Basis untersucht. Für diese konnten die genauen Relaxationszeiten von Ladungsträgern bestimmt werden. Mit zunehmender Überschussenergie dauert die Relaxation länger. Interessanterweise relaxieren Elektronen trotz größerer energetischer Lücken zwischen den diskreten Energieniveaus schneller als Löcher. Dies konnte mit einem effizienten Auger-ähnlichen Streumechanismus erklärt werden. Darüber hinaus nimmt die Relaxationszeit sogar um eine Größenordnung zu und erreicht Pikosekunden, wenn Löcher aus der Schale in den Kern relaxieren müssen. Aufgrund dieses langsamen Prozesses können Löcher von Fallenzuständen eingefangen werden, was zu strahlungsfreier Rekombination führt. Daher ist eine optimierte Ladungsträgerinjektion für die Entwicklung von effizienten Bauelementen nötig. Als zweites Materialsystem wurde die Gruppe der Perowskite untersucht. Diese ermöglichen eine kostengünstige und einfache Herstellung von hocheffizienten Solarzellen, enthalten aber meist Blei. Eine mögliche Alternative stellen bleifreie Doppelperowskit-Nanokristalle dar. Für diese wurde die Ladungsträgerdynamik auf Basis ihrer indirekten Bandstruktur charakterisiert. Es konnte gezeigt werden, dass defektbedingt gebundene Exzitonen hierbei eine maßgebliche Rolle spielen. Diese Exzitonen führen nicht nur zu einem deutlichen Absorptionsmaximum unterhalb des direkten Bandkantenübergangs, sondern auch zu einer hochenergetischen Emission. Dies ist überraschend, da die Elektronen innerhalb von 10 ps zum Leitungsbandminimum streuen. Dadurch nehmen die Exzitonen einen indirekten Charakter an und die Photolumineszenz verschiebt sich um 1 eV in den roten Spektralbereich, wo die Hauptemission beobachtet werden kann. Somit zeigen diese Ergebnisse den großen Einfluss von Defektzuständen auf die optischen Eigenschaften und die Ladungsträgerdynamik. Die Resultate dieser Arbeit demonstrieren, dass es möglich ist giftige Elemente bei Nanokristallen zu vermeiden und trotzdem vielversprechende optoelektronische Eigenschaften zu erzielen. Die Charakterisierung der Ladungsträgerdynamik mittels optischer Spektroskopie ist gleichzeitig ein wichtiger Beitrag für die Entwicklung von zukünftigen Anwendungen. The use of nontoxic semiconductor nanocrystals for optoelectronic applications requires precise knowledge of their physical properties. The previous research, though, has focused on materials that contain toxic elements such as lead or cadmium. However, these are not suitable for commercial applications. Therefore, in this thesis, nontoxic nanocrystals were investigated by optical spectroscopy. Thus, advantages and challenges for the development of future devices could be identified. Colloidal quantum dots are bright emitters that may be used in the next generation of light-emitting diodes. In contrast to the cadmium-based variants, core/shell quantum dots based on indium phosphide are here investigated. It was possible to determine the exact relaxation time scales of charge carriers. With increasing excess energy the relaxation takes longer. Interestingly, electrons relax faster than holes despite larger energy gaps between the discrete energy levels. This can be explained by an efficient Auger-like scattering mechanism. Furthermore, the relaxation time increases even by an order of magnitude reaching several picoseconds if holes have to relax from the shell into the core. Due to this slow process, hole trapping becomes significant and leads to nonradiative recombination. Therefore, an optimized charge carrier injection process is necessary for the development of efficient devices. As a second material system, the group of perovskites was investigated. They enable a cheap and facile production of highly efficient solar cells, but mostly contain lead. A possible alternative is given by lead-free double perovskite nanocrystals. For these, the charge carrier dynamics was characterized based on their indirect electronic band structure. It could be shown that defect-related bound excitons play a significant role in this process. These excitons not only cause a strong absorption peak below the direct band edge transition but also give rise to a high-energetic emission. This is surprising since the electrons scatter within 10 ps toward the conduction band minimum. Thus, the excitons become indirect and the photoluminescence shifts by 1 eV into the red spectral region, where the main emission peak can be observed. Hence, these results show the important role of defect states for the optical properties and charge carrier dynamics. The results of this thesis demonstrate that it is possible to avoid toxic elements in nanocrystals and still achieve desirable optoelectronic properties. The characterization of the charge carrier dynamics by optical spectroscopy is also an important contribution to the development of future applications.

In many tasks humans can trade speed against accuracy. This variation of strategy has different consequences for congruency effects in different conflict tasks. Recently, Mittelstädt et al. (2022) suggested that these differences are related to the dynamics of congruency effects as assessed by delta plots. With increasing delta plots in the Eriksen flanker task congruency effects were larger under accuracy set, and with decreasing delta plots in the Simon task they were smaller. Here we tested the hypothesis for a single task, making use of the observation that for the Simon task delta plots decline when the irrelevant feature is presented first, but increase when the relevant feature leads. The differences between congruency effects under speed and accuracy instructions confirmed the hypothesized relation to the slope of delta plots. In fact, for similar delta plots in the compared speed-accuracy conditions, the relation should be a straightforward consequence of the shorter and longer reaction times with speed and accuracy set, respectively. However, when relevant and irrelevant features were presented simultaneously, congruency effects were stronger under speed set at all reaction times. For this condition, a supplementary model-based analysis with an extended leaky, competing accumulator model suggested a stronger and longer-lasting influence of the irrelevant stimulus feature. The congruency effects for reaction times were accompanied by congruency effects for error rates when delta plots were decreasing, but not when they were increasing.

This demo gives an example how pde2path can be used for the continuation of periodic orbits for systems with an external periodic forcing. The demo system is a generalized thin film equation, which is able to model substrates with a switchable wettability.

Trabalho de Conclusão de Curso apresentado ao Instituto Latino-Americano de Tecnologia, Infraestrutura e Território da Universidade Federal da Integração Latino-Americana, como requisito parcial à obtenção do título de licenciado em Geografia - Licenciatura. Este artigo pretende analisar a Base Nacional Comum Curricular (BNCC), a partir das discussões sobre a dicotomia entre Geografia Física e Geografia Humana, buscando compreender como as habilidades da disciplina de Geografia do Ensino Fundamental II aportam e associam essas vertentes, além de compreender como impactam na formação contínua dos professores de Geografia. Assim, a partir de uma metodologia qualitativa por meio de revisão bibliográfica, o artigo também abordará as possibilidades do emprego do sistema GTP (geossistema, território e paisagem) na BNCC. O objetivo central é compreender se existe uma perspectiva integradora da Geografia ou se mantém uma dicotomia e separação entre as mesmas no documento citado, enfraquecendo-a pela perpetuação da sua fragmentação, tal fato que pode prejudicar a prática pedagógica dos professores, impedindo-os que exerçam de forma completa seu papel como docente. No entanto, se conclui que é preciso compreender as contradições, nuances e antagonismos pressupostos por tal documento, pois estabelece direitos e metas para o aprendizado e desenvolvimento da Geografia, mas apresenta um documento em que a Geografia Física é carente de conteúdo e desvalorizada.

Trabalho de Conclusão de Curso apresentado ao Instituto Latino Americano de Ciências da Vida e da Natureza da Universidade Federal da Integração Latino Americana, como requisito parcial à obtenção do título de licenciado em Química - Licenciatura. Este trabalho foi realizado com o objetivo de analisar as potencialidades e limitações do jogo “Alquímica”, criado com a intenção de ensinar o conceito de reações químicas com um enfoque histórico. O jogo foi projetado com design de jogos de tabuleiro modernos, aumentando os elementos de decisão e estratégia e reduzindo os elementos de sorte. Para isto utilizou-se do elemental tetrad (mecânica, estética, história e tecnologia) para produção do jogo, tendo em mente um jogo educativo enquanto realizava este processo. Para análise das potencialidades e limitações foi utilizado dois padrões em uma perspectiva qualitativa: (i) regras implícitas e explícitas, (ii) Intencionalidade lúdica. No primeiro padrão pode-se observar como a estrutura mecânica do jogo, a narrativa e estética escolhidas podem favorecer uma atitude lúdica, assim como a decisão de quem será o alquimista (condutor do jogo) apresenta algumas barreiras de jogabilidade aos estudantes. O segundo parâmetro nos permitiu entender como a tecnologia escolhida e as intenções de ensino de química nas regras agem quanto à interação destes elementos com os estudantes.