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Electrical, Optical and Sensoric Properties of Organic Semiconductors
Pochekailov, Sergii ; Zmeškal, Oldřich (referee) ; Nešpůrek, Stanislav (advisor)
There is big interest in cheap, sensitive and selective gas sensors. In this work, substituted soluble phthalocyanines are proposed as a sensing materials for several gases. Optical, electrical and gas sensing properties of several phthalocyanines were studied and the mechanisms of their interaction with several analyte gases are described. It was found, that sulfo-substituted Pcs has good sensitivity to humidity. Sulfonamide-substituted phthalocyanines are promising for nitrogen dioxide and volatile organic compounds detection. tert-Butyl-substituted phthalocyanines are sensitive to NO2 under higher temperature and seems to be used for environmental monitoring. Commercial gas sensors for NO2, ethanol and humidity were successfully created.
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Optical properties of protective emulsions
Valasová, Denisa ; Veselý, Michal (referee) ; Zmeškal, Oldřich (advisor)
This bachelor´s thesis is aimed to the study of optical properties of protective commercially available emulsions. Chosen emulsions should be responsible for sun protection. They also may be used in cosmetic industry. In the beginning of the thesis, there are defined theoretical features of emulsions and their interaction with UV radiation. Methods which are used to describe optical properties could be found in this section too. The optical properties were measured in thin layer films, in order to simulate emulsions applied on the human skin. UV-VIS spectrophotometry was mainly used to study the optical properties. The obtained results could serve, purely hypothetically, like sun protective tests of chosen emulsions.
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Perovskite materials
Gavranović, Stevan ; Zmeškal, Oldřich (referee) ; Pospíšil, Jan (advisor)
This bachelor´s thesis is focused on a study of electrical properties of perovskite single crystals prepared by inverse temperature crystallization (ITC). Measurements were done on the organic-inorganic halide perovskite monocrystal MAPbBr3 and on the completely inorganic halide perovskite monocrystal CsPbBr3. Crystalline structure and chemical composition of prepared single crystals were determined using x-ray diffraction analysis. Current-voltage characteristics of perovskite monocrystals were measured using solar simulator. Hole carrier mobility were calculated from determined current-voltage characteristics using SCLC method. Furthermore, the dependencies of dielectric permittivity on frequency of alternating current were measured. MAPbBr3 single crystal showed better electrical properties (higher hole carrier mobilities) than CsPbBr3.
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Study of optoelectrical properties of organic semiconductor thin film layers
Pospíšil, Jan ; Weiter, Martin (referee) ; Zmeškal, Oldřich (advisor)
The thesis is focused on the study of electric and dielectric properties of thin film organic materials that can be used as an active layer of photovoltaic cells. Primarily were studied the properties of the layers on the glass substrates, which consist of a thin active layer of phthalocyanines. On the samples were first measured current-voltage characteristics (in the dark and during the exposure) and the basic parameters of the photovoltaic conversion were determined. Finally were measured frequency dependencies (impedance spectra, in the dark and during the exposure) and the parameters of a model of the structure with organic semiconductor were determined. The obtained results will be used to optimize the properties of photovoltaic cells.
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Study of electrical properties of thin polymer films
Pospíšil, Jan ; Vala, Martin (referee) ; Zmeškal, Oldřich (advisor)
The thesis is focused on the study of electric and dielectric properties of thin-film organic materials that can be used as an active layer of photovoltaic cells. Primarily were studied the properties of the layers on the PET or glass substrate, which consist of a thin active layer of polymethylphenylsilane (PMPSi) or derivatives of diketopyrrolpyrrole (DPP). On a selected sample were first measured current-voltage characteristics and current dependences on time at constant voltage (relaxation characteristics). Finally were measured frequency dependences (impedance spectra) and their relaxation characteristics too. The measured data were evaluated using the methods of fractal analysis in HarFA. The results will be used to optimize the properties of photovoltaic cells.
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Study of electrical and dielectric properties of ionic liquids
Mitáčková, Martina ; Pospíšil, Jan (referee) ; Zmeškal, Oldřich (advisor)
This bachelor thesis is focused on the study of electrical and dielectric properties of ionic liquids. Two types of OECT substrates with different semiconductor channel lengths made of PEDOT:PSS were used to measure these properties. The dielectric properties were measured by impedance spectroscopy, where the dependence of the impedance value and its phase angle on the voltage frequency was measured. It was found from V-A characteristics, that the best closing of semiconductor layer occurs at a positive UGD voltage. The switching speeds of different ionic liquids were compared for this voltage.
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Study of transistor properties with ionic liquids
Mitáčková, Martina ; Pospíšil, Jan (referee) ; Zmeškal, Oldřich (advisor)
This diploma thesis is focused on the study of electric and dielectric properties of transistors based on ionic liquids. The measurements were performed on organic electrochemical transistors with a semiconducting channel made of PEDOT:PSS, which were firstly prepared on ITO substrates, later they were printed using 3D print. Ionic liquid NO4 (1-butyl-3-methylimidazolium hydrogensulfate) was used for measuring of the properties. Electrical properties were determined by measuring volt-ampere characteristics, dielectric properties were measured by impedance spectroscopy.
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Study of Thermal Properties of Materials for 3D Printing
Lapčíková, Tereza ; Menčík, Přemysl (referee) ; Zmeškal, Oldřich (advisor)
The aim of this bachelor thesis was to study thermal properties of materials used for 3D printing (so-called filaments), especially a polylactic acid (PLA). Within the theoretical part there was performed the literature review focused on the description of different methods of 3D printing including the summary of suitable materials for these technologies. In particular, we focused on the preparation of PLA, its summarization of its chemical, physical and thermal properties and its practical use in 3D additive printing manufacturing, e.g. in biomedical applications. In the experimental part, PLA samples of different thicknesses were prepared by 3D printing technique and thermal properties such as thermal capacity and thermal conductivity were determined. It was found that thermal conductivity of studied material was 0,128 W/m/K and specific heat capacity 1335 J/kg/K. These values corresponded to the once given in the literature.
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Study of Thermal Properties of Materials for Cooling of Photovoltaic Panels
Dohnalová, Lenka ; Pavlík, Zbyšek (referee) ; Matiašovský, Peter (referee) ; Zmeškal, Oldřich (advisor)
The topic of this doctoral thesis is to study the thermal properties of PCM materials and discussion of their use for cooling of photovoltaic systems. The aim of the study is to measure and characterize the thermal properties of commercial PCM materials (Micronal®), their practical use is related to the phase transitions. The behavior of bulk materials at different temperatures is well described theoretically and experimentally verified. For the application use it is necessary to examine and determine the thermal properties of PCM materials depending on the phase transitions during heating and cooling. To study the thermal properties of materials the known transient methods of measuring are used which give full information about the behavior of the materials investigated in dependence on the temperature and thus allow the determination of the thermo-physical parameters of the system. For the transient measurements there are used especially pulse transient and step wise method. Newly is used also combination of linear temperature rise (the ramp wise) and the step wise method. The principle is based on the generation of a small amount of heat inside the studied sample and it is measured the thermal response of the system from which it may be then determined the necessary thermo-physical parameters. The theoretical part of this thesis focuses on characterization of methods for the determination of thermo-physical parameters of the investigated material. In the experimental part of the approached process of experiment, the results, the method of evaluation of the obtained data and also the discussion of results from the viewpoint of potential applications are presented.
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Study of electrical and dielectric properties of perovskites
Moravčík, Marek ; Pospíšil, Jan (referee) ; Zmeškal, Oldřich (advisor)
This bachelor’s thesis is focused on a study of electrical and dielectrically properties of perovskite single crystal prepared by inversed temperature crystallization. Measurement was done on sample of MAPbBr3. First the temperature dependences of current-voltage characteristics were measured, they help to determined Arrhenius dependences. Activation energies were determined from Arrhenius dependences for every single voltage. These activation energies were used to determined position of Fermi level during thermodynamic balance. Concentration of state for dominant energies and charge carrier mobility (drift, microscopic) were determined from current-voltage characteristics for constant temperature. Relative permittivity was used to determine these parameters from impedance measurement.
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