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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.
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Multimedia support of physics education
Koupil, Jan ; Dvořák, Leoš (advisor) ; Obdržálek, Jan (referee) ; Sládek, Petr (referee)
This thesis deals with possibilities of use of multimedia technology in physics education and describes a few new educational units. First chapter of the thesis contains a short definition of multimedia and a brief summary of the importance of multimedia in general. The main merits of the thesis are the four chapters regarding individual multimedia technologies. Firstly, the potentialities of utilization of video records in physics measurements are discussed, including a few new experiments. The second main topic is the slow motion video, its importance, use in physics lessons and the description of a series of recorded slow motion video clips. As the next point, the use of a computer sound card as a measurement tool in innovative experiments is discussed. Finally, in the last chapter a series of newly created computer programs for visualization of hydrogen atom orbital shapes is characterized. The created educational units have been tested and classroom experience, students' or teachers' feedback are presented in corresponding chapters.
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Military Memorial Places in Czechia: Territorial Differences and Changes in Their Perception in the Context of Political Development
Sládek, Petr ; Havlíček, Tomáš (advisor) ; Kučera, Zdeněk (referee)
This diploma thesis deals with military memorial places and their spatial information. The work is processed within the new defined geographic direction Necrogeography and continues on discussion about taboo subject of death, cemeteries and military places. It is also a continuation of similar work on the theme of small religious monuments in Czechia. The work has several aims: It rates the role of military memorial places in the formation of regional and local identity. The other aim is to rate the territorial differentiation of military memorial places and how the form of military commemorative locations differs within Czechia. For the purpose of the work a typology of military memorial places was created which allows data to be compared and concluded. The aim of the research part of this diploma thesis is addition of spatial information of the current inventory of military commemorative places in Czechia and evaluation of territorial differentiation between the years 1918 - 1938 in model areas. Only the existing memorial places are taken to account because of inaccurate records of past memorial places in model areas (inability to capture every single military memorial place in the history of 20th century). Territorial differentiation of military places is analyzed through field research in model...
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Mechanical and Electrical Properties of Microcrystalline Silicon Thin Films
Vetushka, Aliaksei ; Fejfar, Antonín (advisor) ; Čech, Vladimír (referee) ; Sládek, Petr (referee)
Amorphous and nano- or micro- crystalline silicon thin films are intensively studied materials for photovoltaic applications. The films are used as intrinsic layer (absorber) in p-i-n solar cells. As opposed to crystalline silicon solar cells, the thin films contain about hundred times less silicon and can be deposited at much lower temperatures (typically around 200 0 C) which saves energy needed for production and makes it possible to use various low cost (even flexible) substrates. However, these films have a complex microstructure, which makes it difficult to measure and describe the electronic transport of the photogenerated carriers. Yet, the understanding of the structure and electronic properties of the material at nanoscale is essential on the way to improve the efficiency solar cells. One of the main aims of this work is the study of the structure and mechanical properties of the mixed phase silicon thin films of various thicknesses and structures. The key parameter of microcrystalline silicon is the crystallinity, i.e., the microcrys- talline volume fraction. It determines internal structure of the films which, in turn, decides about many other properties, including charge transport and mechanical sta- bility. Raman microspectroscopy is a fast and non-destructive method for probing the...
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Web Interface for Network Anomaly Detection System
Sládek, Petr ; Kováčik, Michal (referee) ; Bartoš, Václav (advisor)
The goal of this work is to create a web interface for network anomaly detection system called HostStats. Its mission is to enable users to effectively work with data and statistics provided by the system. Web interface works as a plugin to NfSen as a completely independent web applications. Implementation took place in PHP using the Nette Framework, HTML5, CSS3, and JavaScript using the jQuery library.
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Application for Communication with the Lost Mobile Phone
Sládek, Petr ; Rychlý, Marek (referee) ; Očenášek, Pavel (advisor)
This thesis is dedicated to communication with lost mobile device throw the Internet with its owner because of the possibility of finding, return or lock the device. It focused on analysis existing solution and draft own mobile application for Android platform with supportive web application, This thesis also summary basic principles of creating application for Android OS and communication with cloud base service Google Cloud Messaging.
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Low level measurement
Roubal, Zdeněk ; Lazar, Josef (referee) ; Sládek, Petr (referee) ; Steinbauer, Miloslav (advisor)
The doctoral thesis presents methods for low-level measurements, which are exemplified by the general measurement of air ion concentration. Within the first section, the author progressively identifies certain critical effects influencing the concentration of air ions, and these effects are to be considered in evaluating the uncertainty of the measured concentrations. Thus, the thesis aims to provide a systematic description of the procedures and requirements related to low-level measurements; the proposed description then involves a discussion of the process reliability requirements, namely the factors of repeatability, elimination of errors, and definition and describability of measurement uncertainties. Such methodology facilitates, among other activities, the long-term monitoring of air ion concentration in extreme environments, including caves or spaces characterized by high temperatures and humidity. The use of common methods for determining the air ion mobility spectrum is accompanied by a number of disturbing effects, such as spurious fluctuation in the concentration of air ions in time. The experimental section of the thesis describes the testing of different configurations of the measuring device (a collecting electrode and a polarization capacitor); at this stage, we seek the most advantageous distribution of the electrostatic field in the sensor – a Gerdien tube. The systematic suppression of the influence of spurious fluctuations in air ion concentration during the measurement of saturation characteristics is carried out with the least-squares numerical method (as a supporting element), a hybrid technique to describe and evaluate the experimental model. In the second part of the thesis, the methodology of low-level measurement is complemented with procedures for the measurement of freezing potential. This latter domain, as an overall experimental approach applicable during phase changes of the sample, has hitherto not been sufficiently characterized from the metrological perspective, in an up-to-date manner; several subregions of the said domain remain somewhat obscured and deserve significantly more attention. In the given context, this thesis systematically considers a problem where comparable measurement results produced by multiple authors are not available. The measuring methodology proposed herein was utilized in applied research to facilitate the fabrication of an apparatus for the experimental measurement of freezing potential in pre-defined samples; the obtained results then lead us to conclusions with respect to the evaluation of effects that cause differences in the measured data, and the results can be further compared with those obtained by other researchers investigating the given segment of the problem.
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The Analysis and Optimization of Selective Technological Processes for Contacts on Crystalline Silicon Solar Cells
Hladík, Jiří ; Sládek, Petr (referee) ; Myslík, Vladimír (referee) ; Szendiuch, Ivan (advisor)
The submitted work deals with the methods for manufacturing and analysis of contacts on crystalline silicon solar cells. It is focused on selective processes for the production of solar cells metal contacts. The masking feature of silicon nitride is used for selective silicon etching, selective phosphorus diffusion and selective electro-less nickel deposition. Properties of metal contacts precursors are investigated using optical microscopy and their electrical properties using methods based on a four-point probe method. Results are used for the manufacturing of silicon, solar cell with an innovative type of the structure of the front side metallization: chemical nickel, conductive adhesive and copper wire. This approach allows to reduce shading of the front area of PV cells with the ability to avoid usage of busbars. The another advantage of this approach is in replacement of costly silver in at least 2/3 cross section of the front side metallization. Selective ablation of silicon nitride layer was conducted by means of IR laser beam.
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