Spectroscopic investigation on photoreactivity, structure and polymorphism of organic molecular crystals

The study of the spectroscopic phenomena in organic solids, in combination with other techniques, is an effective tool for the understanding of the structural properties of materials based on these compounds. This Ph.D. work was dedicated to the spectroscopic investigation of some relevant processes occurring in organic molecular crystals, with the goal of expanding the knowledge on the relationship between structure, dynamics and photoreactivity of these systems. Vibrational spectroscopy has been the technique of choice, always in combination with X-ray diffraction structural studies and often the support of computational methods. The vibrational study of the molecular solid state reaches its full potential when it includes the low-wavenumber region of the lattice-phonon modes, which probe the weak intermolecular interactions and are the fingerprints of the lattice itself. Microscopy is an invaluable addition in the investigation of processes that take place in the micro-meter scale of the crystal micro-domains. In chemical and phase transitions, as well as in polymorph screening and identification, the combination of Raman microscopy and lattice-phonon detection has provided useful information. Research on the fascinating class of single-crystal-to-single-crystal photoreactions, has shown how the homogeneous mechanism of these transformations can be identified by lattice-phonon microscopy, in agreement with the continuous evolution of their XRD patterns. On describing the behavior of the photodimerization mechanism of vitamin K3, the focus was instead on the influence of its polymorphism in governing the product isomerism. Polymorphism is the additional degree of freedom of molecular functional materials, and by advancing in its control and properties, functionalities can be promoted for useful applications. Its investigation focused on thin-film phases, widely employed in organic electronics. The ambiguities in phase identification often emerging by other experimental methods were successfully solved by vibrational measurements.

Characterization of innovative kerfless cutting of monocrystalline silicon wafers for photovoltaic applications

Nowadays renewable energies are a hot research topic, and the goal is to improve cell efficiency and reduce production costs, aiming to make the use of photovoltaics increasingly widespread and convenient. Monocrystalline silicon solar cells are leaders in the photovoltaic market. However, market-established cutting techniques produce a consistent amount of material waste when cutting ingots into wafers. The“Stress-induced LIft-Off Method” (SLIM) is emerging in recent years as an alternative, more sustainable separation technique, which reduces material loss and can lead to obtaining increasingly thinner wafers, further reducing the required amount of silicon. This thesis presents the micro-characterization of the separated wafers with the SLIM technique. The wafers were obtained with a two-step procedure. First, a layer of defects was induced in the silicon using ultra-short medium-infrared laser pulses. Then, the material was deposited on one of the sides and induced stress in the silicon, such as to further weaken it. In this way, only rapid cooling is required for detachment to occur. The obtained results indicate that the SLIM-cut technique halves the minority carriers’ lifetime. There is no amorphization, crystal disorder or high-pressure phases. However, changes in the Raman spectra suggest that tensile stress may have been produced on these surface layers by the separation process. The AFM topography highlights surface irregularities, which may be removed with a polishing step. The surface also shows laser-modified regions, which are evident in SEM images, but not in AFM topographies, suggesting a charging effect due to electron bombardment. Lastly, the electrical characterization by conductive AFM lacks any changes in the conductive behaviour of the material where the laser-modified areas should be located. In conclusion, these preliminary results are promising to carry out a systematic characterization of this technique of this innovative SLIM technique.

Fabrication by magnetron sputtering and characterization of electrodes based on CuIn0.7Ga0.3Se2 (CIGS)

This thesis work aims to produce and test multilayer electrodes for their use as photocathode in a PEC device. The electrode developed is based on CIGS, a I-III-VI2 semiconductor material composed of copper (Cu), indium (In), Gallium (Ga) and selenium (Se). It has a bandgap in the range of 1.0-2.4 eV and an absorption coefficient of about 105cm−1, which makes it a promising photocathode for PEC water splitting. The idea of our multilayer electrode is to deposit a thin layer of CdS on top of CIGS to form a solid-state p–n junction and lead to more efficient charge separation. In addition another thin layer of AZO (Aluminum doped zinc oxide) is deposit on top of CdS since it would form a better alignment between the AZO/CdS/CIGS interfaces, which would help to drive the charge transport further and minimize charge recombination. Finally, a TiO2 layer on top of the electrodes is used as protective layer during the H2 evolution. FTO (Fluorine doped tin oxide) and Molybdenum are used as back-contact. We used the technique of RF magnetron sputtering to deposit the thin layers of material. The structural characterization performed by XDR measurement confirm a polycrystalline chalcopyrite structural with a preferential orientation along the (112) direction for the CIGS. From linear fit of the Tauc plot, we get an energy gap of about 1.16 eV. In addition, from a four points measurements, we get a resistivity of 0.26 Ωcm. We performed an electrochemical characterization in cell of our electrodes. The results show that our samples have a good stability but produce a photocurrent of the order of μA, three orders of magnitude smaller than our targets. The EIS analysis confirm a significant depletion of the species in front of the electrode causing a lower conversion of the species and less current flows.

A abordagem centrada na pessoa e a psicologia do esporte : vivência de um psicólogo com jogadores e a comissão técnica de uma equipe durante os períodos de preparação e disputa da Copa São Paulo de Futebol Júnior

Universidade Estadual de Campinas . Faculdade de Educação Física

Desenvolvimento de equações generalizadas para estimativa da coordenação motora em crianças e adolescentes portadores de deficiencia mental

Universidade Estadual de Campinas . Faculdade de Educação Física

Efeitos de diferentes tamanhos de palmares nos indicadores tecnicos do nado crawl em esforços maximos de 50 e 100m

Universidade Estadual de Campinas . Faculdade de Educação Física

A dimensão prática na preparação profissional em educação física : concepção e organização acadêmica

Universidade Estadual de Campinas . Faculdade de Educação Física

Pedagogia da roda ginástica (alemã) : análise da proposta metodológica desenvolvida no clube Bayer Leverkusen na Alemanha

Universidade Estadual de Campinas. Faculdade de Educação Física

Modelo de análise técnico-tática do jogo de handebol : necessidades, perspectivas e implicações de um modelo de interpretação das situações de jogo em tempo real

Universidade Estadual de Campinas . Faculdade de Educação Física

Formação e desenvolvimento profissional do treinador : um estudo sobre os treinadores de basquetebol, suas identidade e saberes

Universidade Estadual de Campinas. Faculdade de Educação Física

A visão estrategico-tatica de tecnicos campeões da Liga Nacional de Futsal

Universidade Estadual de Campinas . Faculdade de Educação Física

Esporte educacional e deficiencia : encontros esportivos no contexto escolar

Universidade Estadual de Campinas . Faculdade de Educação Física

Analise da disciplina de educação fisica especial nas Institutições de Ensino Superior publicas do estado do Parana

Universidade Estadual de Campinas . Faculdade de Educação Física

Recreação e lazer como integrantes de curriculos dos cursos de graduação em educação fisica

Universidade Estadual de Campinas . Faculdade de Educação Física

Recreação e lazer como integrantes dos curriculos dos cursos de graduação em educação fisica

Universidade Estadual de Campinas. Faculdade de Educação Física