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Luminescence Diagnostic of Photovoltaic Cells
Stojan, Radek ; Frantík, Ondřej (referee) ; Šály,, Vladimír (referee) ; Vaněk, Jiří (advisor)
Diagnostic of photovoltaic cells defects is one of the key step in production. This dissertation thesis deals about diagnosis of photovoltaic cells by radiative recombination of electron - hole pairs. This radiative recombination is known as luminescence. Diagnostic methods using this local light emission in infrared region have innovative potential. The method of electroluminescence is one of the most widely used luminescence methods whose modifications are applied across the industry, especially in semiconductors. The main area of this thesis research is focused on non-destructive analysis of radiated infrared radiation of monocrystalline and polycrystalline solar cells in various modifications of standard electroluminescence method. In this research there are used two types of CCD cameras are used as luminescent radiation detectors. Method of photon emission microscopy is used for magnification element. Local light emission inspection by microscopy should have benefit to qualitative evaluation of solar cells defects. Radiation emitted by the solar cell has a wave character. This fact brings the potential of using some of the characteristics of the waves. We are talking about the intensity and mainly about new characterization by polarization during the detection of defects in the solar cell surface. Innovation of the measuring workplace of the standard electroluminescence method to use polarization analysis is one of the goals of this dissertation thesis.
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Determination of absolute quantum yield of luminescence
Smísitel, Petr ; Valenta, Jan (advisor) ; Herynková, Kateřina (referee)
In this bachelor thesis we will study the determination of absolute quantum yields (efficiency) of photoluminiscence, which is equal to the ratio of number of emitted photons and number of absorbed photons. The common approach is to compare the absorption and luminescence spectrum. The main experimental problem is to eliminate the influence of angular dependence of reflection, emission and scattering. Therefore it is convenient to use the integrating sphere which eliminate most of the problems of relative measurements of quantum yield. In detail we will describe the method to determine the quantum yields of luminescence using the integrating sphere including the description of the experimental equipment and the procedure of processing data and estimation of uncertainty. Finally, we apply the procedure to solid and liquid samples containing silicon nanocrystals. We will measure the dependence of quantum yields on the applied excitation wavelength. 1
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Smart materials
Valenová, Ludmila ; Němec, Karel (referee) ; Molliková, Eva (advisor)
The bachelor thesis deals with smart materials. In summary, it describes the general classification of smart materials into individual groups. Describing the properties of individual groups and using these materials in practice. In more detail, there are described groups of shape memory materials, color changing materials under the external stimulus, light emitting materials and materials based on piezoelectric effect.
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Preparation of graphene quantum dots and study of their properties
Zdražil, Lukáš ; Mikula, Milan (referee) ; Zmeškal, Oldřich (advisor)
Current methods for preparing graphene quantum dots (GQDs) rely on oxidation and reducing agents or require energy-intensive and technologically demanding preconditions. Applying microwave expansion and liquid phase exfoliation (LPE) in a sample of graphite powder enabled us to prepare GQDs that exhibit strong luminescence in the blue region of the visible spectrum. The proposed technique for synthesizing GQDs is energetically undemanding and does not necessitate additional chemical components.
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Theoretical study of spin-orbit coupling on spectra and photophysics of rhenium complexes
Heydová, Radka ; Záliš, Stanislav (advisor) ; Slavíček, Petr (referee) ; Srnec, Martin (referee)
Title: Theoretical study of spin-orbit coupling on spectra and photophysics of rhenium complexes Author: RNDr. Radka Heydová Department: Physical and Macromolecular Chemistry Supervisor: Ing. Stanislav Záliš, CSc., JHI AS CR, v.v.i. Supervisor's e-mail address: stanislav.zalis@jh.inst-cas.cz Abstract: Relativistic effects, especially spin-orbit coupling (SOC), play an essential role in transition metal chemistry and SOC treatment is indispensable for a correct theoretical description. To demonstrate the importance of SOC, the energies and oscillator strengths of vertical transitions for a series of [ReX(CO)3(2,2'-bipyridine)] (X = Cl, Br, I) and [Re(imidazole)(CO)3(1,10-phenanthroline)]+ complexes were calculated in the spin-free (SF) and spin-orbit (SO) conceptual frameworks. Two different computational approaches were adopted: SO-MS-CASPT2 where SOC was added a posteriori using a configuration interaction model (SO-RASSI), and the approximate perturbative SO-TD-DFT method. Relativistic effects were included via the two-component Douglas-Kroll-Hess transformation and the zeroth-order regular approximation in the former and the latter technique, respectively. The SF (i.e. accounting only for the scalar relativistic effects) and SO results from both methods were compared with each other and to available...
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Copper(I) complexes with phosphinonitrile donors
Horký, Filip ; Štěpnička, Petr (advisor) ; Kubíček, Vojtěch (referee)
Title: Copper(I) complexes with phosphinonitrile donors Author: Bc. Filip Horký Department: Department of Inorganic chemistry Supervisor: prof. RNDr. Petr Štěpnička, Ph.D. Abstract: Although coordination compounds with phosphinonitrile ligands are already well known, in the vast majority of these complexes these ligands coordinate as simple P-donors with their cyano groups acting as auxiliary substituents. This led us to synthesize and study a series of Cu(I) complexes with two isomeric phosphinonitrile donors, namely 2-(diphenylphosphino)benzonitrile (Lo ) and 2-(diphenylphosphino)benzonitrile (Lp ), with different ligand-to-metal ratios and possibly characterize further coordination modes offered by these hybrid donors. This work describes the preparation of phosphinonitrile complexes from the aforementioned ligands and simple copper(I) halides (CuX, X = Cl, Br, I), pseudohalides (X = CN) and from [Cu(MeCN)4][BF4]. The products were characterized by nuclear magnetic resonance, infrared spectroscopy and elemental analysis, mass spectrometry, and their solid-state structures were determined by single-crystal X-ray crystallography. In addition, luminescent properties of the Cu(I) complexes were studied and catalytic activity of selected complexes was tested in copper-catalyzed alkyne-azide cycloaddition...
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Interdisciplinary relations of physics and chemistry in science education
Konečný, Martin ; Valenta, Jan (advisor) ; Rusek, Martin (referee)
Title: Interdisciplinary relations of physics and chemistry in science education Abstract: This master's degree thesis deals with the topic of interdisciplinary relations of chemistry and physics in science education. According to the review, to conveniently integrate physics and chemistry the appropriate topics and approaches were selected. The thesis includes teaching materials and worksheets to the three topics (Evolution of the Universe and the Origin of Elements, Luminescence and Composition and Properties of Matter) that are suitable for integration of physics and chemistry. The teaching material "Evolution of the Universe and the Origin of the Elements" includes a study text for teachers and a shorter study text for pupils. The teaching material "Luminescence" is based on an independent research done by pupils with their own crafted UV-lamp, completed with the facts included in a powerpoint presentation. The teaching material "Composition and Properties of Matter" consists of three parts (The paraffin, The Candle and The Properties of Selected Organic Substances) and is designed for an independent research done by pupils. Listed study materials were checked by teachers during meetings and seminars. The thesis also includes an evaluation of listed study materials by an expert group of high school...
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Multiphoton absorption of ultrafast laser pulse
Zukerstein, Martin ; Trojánek, František (advisor) ; Schmoranzerová, Eva (referee)
Nonlinear optics is constantly developing and in terms of future applications very perspective field of physics. With high-intensity pulsed lasers we are able to study interesting phenomena in matter that we cannot observe with common sources of light. The aim of this thesis is a study of the multiphoton absorption of high-intensity pulses in diamond using z-scan technique. It theoretically describes this nonlinear phenomenon using quantum theory. The next section author took a measurement of the two-photon absorption and found the two-photon absorption coefficients in different samples. Diamond was chosen as the sample material. This material has absolutely unique properties that rank it highly in future applications for optoelectronic devices.
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