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Organic solar cells prepared by methods compatible with printing technologies
Babincová, Kristina ; Pospíšil, Jan (referee) ; Zmeškal, Oldřich (advisor)
The theoretical part deals mainly with basic properties of organic materials, which are used in electronics, and especially in the field of photovoltaic cells. The experimental part deals with preparation of photovoltaic cells by deposition from solution, characterization of their basic electrical properties and preparation of a photovoltaic cell with its own pattern. Samples of classical and inverted structures of photovoltaic cells with P3HT and PCBM bulk heterojunction were prepared. Reference samples were prepared under standard conditions (under nitrogen). Their efficiency was around 3 %. In addition, samples were prepared by spin coating under laboratory conditions and by spreading. In both cases, their efficiency was about 1.5 %. Large-scale photovoltaic cells (active area of about 1 cm^2) were prepared in the last experiment presented. Efficiency decreased to 0.75 %. From results mentioned above is clear that very simple methods and procedures that do not impair the price/performance ratio can be used to prepare photovoltaic cells.
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Study of ion liquids transistor properties
Maráčková, Lucie ; Nešpůrek, Stanislav (referee) ; Sládek, Petr (referee) ; Zmeškal, Oldřich (advisor)
The doctoral thesis is focused on ionic liquids, electrochemical transistors and the study of their electrical and dielectric properties. Current-voltage characteristics were used for determination of the electrical properties of measured ionic liquids. Impedance spectroscopy was used to determine the dielectric properties of measured ionic liquids. Transient measurement was used to determine the electrical properties of measured organic electrochemical transistors based on ionic liquids. Models of every measured ionic liquid was assembled from current-voltage characteristic and from impedance spectroscopy. Models of every measured organic electrochemical based on ionic liquids was assembled from transient measurement.
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Study of the crystallization process kinetics of perovskites and their precursors
Sršeň, Bohdan ; Gavranović, Stevan (referee) ; Zmeškal, Oldřich (advisor)
This thesis focuses on the properties of perovskite materials and examines the methods for preparing layers and potentially monocrystals of these materials. Emphasis is placed on analyzing the electrical and optical properties of perovskites. The experimental part of the thesis is dedicated to the preparation of perovskite material layers and subsequent measurement of their electrical properties during the crystallization process and after its completion. The prepared samples exhibit a macroscopic size due to the interdigitated electrode structure, ensuring a large active surface area. Special attention is given to the influence of nano-particles on the crystallization process and the resulting current-voltage (I-V) characteristics of the prepared samples. Understanding how the presence of nano-particles affects the crystallization and electrical properties of perovskite layers is crucial. These insights are necessary for further optimization of the preparation processes and enhancing the performance of perovskite materials in their final applications. The thesis provides an overview of the properties of perovskites and their preparation. The experimental results yield important insights into the relationship between nano-particles, crystallization, and electrical characteristics of perovskite layers.
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Thermoelectric properties of alkali activated aluminosilicates
Filipská, Kristýna ; Fiala,, Lukáš (referee) ; Zmeškal, Oldřich (advisor)
This work focuses on the potential usage of alkali-activated aluminosilicates (AAA) in relation to energy harvesting. It sets a goal of familiarizing the reader with thermoelectrical conversion itself and its existence within those materials. Based on this knowledge, the measurement of thermoelectrical voltage has been conducted in chosen mixtures of AAA; more specifically a slag geopolymer with carbon black admixture, a slag geopolymer with graphite powder admixture and a metashale geopolymer with graphite powder admixture. This experiment was executed by repeated heating of the surface area of the sample on one side using a resistor, while the other side was kept at reference temperature. The response in the form of voltage generated in the sample as well as on the electrodes was recorded. The measured values were then used to calculate the Seebeck coefficient. The best response was provided by a slag geopolymer sample with carbon black admixture at 4 % concentration (|| = 1904 V/K). The second goal was to measure thermal properties of those samples, specifically the specific heat capacity, the thermal conductivity coefficient and thermal diffusivity. This goal has been reached by capturing the samples with a thermal camera while heating them on a hot-plate. The highest values of specific heat capacity and the thermal conductivity coefficient were provided by a sample of metashale geopolymer with graphite powder admixture at 8 % concentration (c = 2086 J/kg/K; = 1,815 W/m/K). Thermal diffusivity proved to be almost identical in all samples, 610-7 m2/s on average. Based on the results, we conclude that the thermoelectrical conversion in these materials is not enough to be significant in bigger scale energy harvesting yet. However, we also believe that it’s possible to reach better results with further research.
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Study of optical properties of perovskites and their precursors thin films
Blahut, Jan ; Pospíšil, Jan (referee) ; Zmeškal, Oldřich (advisor)
The thesis is focused on the study of the optical properties of thin films of perovskites and their precursors. The first two chapters of the theoretical part are theoretical introduction to the studied problems, they discuss the basics of electromagnetic radiation and its interaction with matter and basic informations about perovskite materials, especially their semiconductor structure. The remaining two chapters deal with specific principles and practical uses of methods and procedures for the preparation of thin films, as well as the instrumentál characteristics of thin films in terms of their optical properties. The experimental part is focused on the preparation of solutions of perovskites and their precursors, where the replication and optimization of published procedures took place, the preparation of thin layers of these solutions by the spin coating method and their ellipsometric characterization using the Tauc plot method, modeling and fitting of the experimentally determined data, which led to the determination of the index refraction, absorption coefficient and band gap width of individual materials.
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Study of leaded and lead-free perovskite nanoparticles properties
Holečková, Jana ; Zdražil, Lukáš (referee) ; Zmeškal, Oldřich (advisor)
This master thesis examines optical properties of lead and lead-free perovskite nanoparticles. Two types of perovskite nanoparticle solutions with lead or bismuth were prepared. One type was hybrid inorganic-organic perovskite nanoparticles, either containing bromine anions or chlorine anions. The second type was purely inorganic perovskite nanoparticles, also containing either bromine anions or chlorine anions. During synthesis were used different solvents. Solutions were characterized by dynamic light scattering, fluorescence spektrometry and UV-VIS spectrophotometry. The measured results were discussed.
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Study of energy accumulation during phase change of paraffin wax
Lapčíková, Tereza ; Krouská, Jitka (referee) ; Zmeškal, Oldřich (advisor)
This thesis deals with the study of the process of energy storage during phase transformation, the so-called latent heat for commercial materials of the Rubitherm® RT line (Rubitherm Technologies GmbH) with applications in the construction industry. The thermophysical properties of Rubitherm® RT35HC, RT28HC and RT18HC materials differing in phase transformation temperature were investigated using the transient method. For the Rubitherm® RT35HC material a value of the thermal conductivity coefficient in the solid phase of 0.21 W/m/K and in the liquid phase of 0.23 W/m/K was determined. The specific heat capacity value in the solid phase was determined to be 1980 J/kg/K and in the liquid phase 1995 J/kg/K. For Rubitherm® RT28HC, the value of the thermal conductivity coefficient in the solid phase was determined to be 0,23 W/m/K and the value of the specific heat capacity in the solid phase was determined to be 1997 J/kg/K. For the Rubitherm® RT18HC material, a liquid phase thermal conductivity coefficient of 0,27 W/m/K and a liquid phase specific heat capacity of 2010 J/kg/K were determined. Using differential scanning calorimetry (DSC), the melting temperature of the Rubitherm® RT28HC sample was determined at 27.43 °C and solidification at 23.51 °C, while for the Rubitherm® RT35HC sample melting occurred at 36.51 °C and solidification at 31.86 °C and 32.28 °C. In the experimental part of this work, modifications were made to the measuring apparatus used in such a way that it could be used for the study of materials that change their state of matter during the experiment.
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Study of electric properties of thin films of perovskite precursors
Harna, Václav ; Pospíšil, Jan (referee) ; Zmeškal, Oldřich (advisor)
High efficiency perovskite solar cells may be the solution to obtain cheap renewable solar energy. However, characteristics of crystalline perovskite materials suitable for solar cells are not yet all clearly understood. In this thesis was studied and optimized the preparation of perovskite methylammonium lead tribromide (MAPbBr3) crystals using anti solvent vapor assisted crystallization (AVC). These crystals were prepared and studied in a small channel between two carbon electrodes on 3D printed substrate made from polylactic acid (PLA) connected to a larger electrode system were measuring took place. Electrical properties of prepared crystal structures were studied using current voltage characteristic and the process of crystallization was documented. Crystal prepared by AVC method achieved sizes larger than 0,5 mm, their electrical conductance increased with their size and the crystals were photo and thermal sensitive. During crystallization of MAPbBr3 precursors from solution was found that a certain structural change exhibiting an increase in electrical conductance takes place in the presence of MABr. The setup of PLA substrate and measuring electrode system creates great opportunities for study of other perovskite materials and may be able to uncover some of the mysteries that these fascinating materials hold.
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Study of heat transport throw bulk materials with electric conductive aditive
Vacula, Jan ; Menčík, Přemysl (referee) ; Zmeškal, Oldřich (advisor)
Bachelor thesis is focused on the study of heat transport in bulk materials made from PLA (polylactic acid) filaments by 3D printing. For subsequent applications it is important to know the electrical, dielectric and thermal parameters of materials with different dyes, pigments and electrically conductive additives. The aim of this work is mainly to study the thermal properties of the series and the influence of additives on these properties. The main focus is to study the thermal properties of the samples. In the theoretical part, different 3D printing methods are mentioned, the methods of measuring the thermal properties, and finally the properties of the lactic acid polymer are described. The experimental part is devoted to the description of the process of 3D printing samples for measurements and then the method of measuring the thermal properties of the printed samples is described. For samples with electrically conductive admixtures, the thermal conductivity was found to be in the range of (0,217–0,292) W/m/K and the specific heat capacity was found to be (382,2–1 007,2) J/kg/K. The electrically conductive materials (PLA with metallic admixtures) were found to have a very good thermal conductivity and a smaller specific heat capacity, while the materials with admixtures of dyes and pigments showed a smaller thermal conductivity and a larger specific heat capacity.
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