|
|
Electrical characteristics of graphene layers and their use as gas sensors
Kučera, Štěpán ; Kaspar, Pavel (referee) ; Macků, Robert (advisor)
This bachelor thesis focuses on the general characterization and description of graphene and related nanostructures. It involves production by the most used methods, including their advantages and disadvantages. Due to the impossibility of connection in the usual way, the graphene sample had to be contacted under visual inspection with a microscope with the tip contacts in the shielded area. Subsequently, it was subjected to current-voltage characterization with normal conditions on a Keithley 4200-CSC instrument. The next step was to measure the same sample under a different gas atmosphere. The result is a comparison of the specific responses to the change in gas atmosphere in which the graphene monolayer was exposed.
|
|
|
Silicon solar cells: methods for experimental study and evaluation of material parameters in advanced structures
Holovský, Jakub ; Vaněček, Milan (advisor) ; Sládek, Petr (referee) ; Hlídek, Pavel (referee)
This work concerns with today's challenges of photoelectrical characterization methods in the research and development of thin film silicon solar cells. Relevant results are obtained only when photocurrent spectroscopy and measurement of current-voltage characteristics, are applied on the real structures that can however be multi-layered, multi-junction devices with nanostructured interfaces. Analytical and numerical optical models comprising light scattering are used for analysis of light absorption and for evaluation of optical absorption coefficient of silicon layers in sub-gap region. The slope of absorption edge and residual absorption in mid-gap indicate material disorder and defect density. Based on the investigation of electrical interaction between sub-cells in the dual-junction solar cell we developed new methods of evaluation of photocurrent spectra and current-voltage characteristics individually for each sub-cell with no need to contact them directly. Usability of Fourier Transform Photocurrent Spectroscopy as a robust method for photocurrent spectroscopy of amorphous silicon is thoroughly analyzed here. The issues of frequency dependence are addressed in detail and comparison with photothermal deflection spectroscopy is made.
|
|
|
Device for automatic measurement of volt-ampere characteristics
Ondráček, Petr ; Vrba, Kamil (referee) ; Lattenberg, Ivo (advisor)
The Master's thesis discusses the design and realization of electronic meter of volt-ampere characteristics using Wifi module ESP32. The device is designed to be able to measure the characteristic in the voltage range of +/- 20 V and current range of +/- 200 mA. The device is controlled by web interface. The user is able to connect to it with for example his or her smartphone. This interface enables the user to configure various parameters, including the range of measurement and the power restriction. Furthermore, it is possible to graphically display the measured characteristic and export the data. To be independent on the outer network, the ESP32 is operated as an access point, which is creating a new simple network without the internet connection. In the Master's thesis, the principle of voltage and current measurement is explained theoretically, the circuit connection of device and the printed circuit board are designed and the cover of the device is modeled. Also the process of creating the device according to the design is described and the cover of the device is printed on 3D printer. After that, the control program is designed, described and uploaded into the resulting device. Finally, the functionality of the device is tested by measuring the volt-ampere characteristics of a few components.
|
|
|
Silicon solar cells: methods for experimental study and evaluation of material parameters in advanced structures
Holovský, Jakub ; Vaněček, Milan (advisor) ; Sládek, Petr (referee) ; Hlídek, Pavel (referee)
This work concerns with today's challenges of photoelectrical characterization methods in the research and development of thin film silicon solar cells. Relevant results are obtained only when photocurrent spectroscopy and measurement of current-voltage characteristics, are applied on the real structures that can however be multi-layered, multi-junction devices with nanostructured interfaces. Analytical and numerical optical models comprising light scattering are used for analysis of light absorption and for evaluation of optical absorption coefficient of silicon layers in sub-gap region. The slope of absorption edge and residual absorption in mid-gap indicate material disorder and defect density. Based on the investigation of electrical interaction between sub-cells in the dual-junction solar cell we developed new methods of evaluation of photocurrent spectra and current-voltage characteristics individually for each sub-cell with no need to contact them directly. Usability of Fourier Transform Photocurrent Spectroscopy as a robust method for photocurrent spectroscopy of amorphous silicon is thoroughly analyzed here. The issues of frequency dependence are addressed in detail and comparison with photothermal deflection spectroscopy is made.
|
|
|
PV plant performance evaluation and optimization
Špinar, Marek ; Ptáček, Michal (referee) ; Morávek, Jan (advisor)
The Master´s thesis deals with issues of operational performance of two photovoltaic power plants. In the thesis is stated the history of photovoltaics, description of photovoltaic effect, used materials and production technology of the most used material in PV industry – Silicon. The basic parts and parameters of photovoltaic power plant are described. Thesis also solves, how could be done the first and periodically control due to relevant directives. The ways of diagnostics potentional failures, methods of measuring and the exam of monitoring system are stated. Practice part is focused on measuring and comparing operational performance of FVE Kurdějov and FVE Šakvice II. Operational performance was calculated from exported data for years 2014 and 2015. The thesis also contains measuring of each string connected to inventors, which are installed on the power plant. The result is an identification of strings with decreased operational performance. Based on that was created recommendations for optimalization and increase of the performance. The last part is software for simulation of photovoltaic power plant. This SW calculates potentional energy, which could be produced in a day with available data export. The calculation is defined by parameters, which are assigned.
|
|
|
Organic semiconductors
Tebich, Ivan ; Macháček, Martin (referee) ; Boušek, Jaroslav (advisor)
My final thesis treats of usage photovoltaic phenomenon to production electric energy by solar cells. It inquires into this phenomenon in organic structures. Further it mentions basic types of constructions organic solar cells and evaluates their properties. In experimental part zhe thesis is focused on characterization thin-film structures made out of photoconductiv organic materials.
|
guest ::
