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Characterization of perovskite solar cell materials by transient techniques
Nakládal, Martin ; Zmeškal, Oldřich (referee) ; Novák, Vítězslav (advisor)
This thesis deals with the study of the lifetime of charge carriers in perovskite single crystals. The principle of perovskite solar cells is formulated, their main structures are characterized and the history of the development of perovskite solar cells is summarized, especially in terms of efficiency. The properties of perovskite single crystals with perovskite solar cells are compared. For measurement purposes, transient methods, impedance spectroscopy, load characteristics and the dependence of sensitivity and photocurrent on the wavelength of incident radiation are described. The practical part deals with the method of measuring and evaluating the lifetime of charge carriers in the investigated perovskite single crystals.
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Growth of single crystals and their basic characterization.
Hanzlíková, Kateřina ; Pospíšil, Jiří (advisor) ; Matěj, Zdeněk (referee)
Basic methods of single crystals growth have been studied in this bachelor thesis. The preparation of anatase and ruby single crystals has been realized by floating zone method in different compositions of the surrounding atmosphere. Crystallinity of prepared materials has been verified by Laue method. The same method has been used for orientation of the prepared single crystals along the principal crystallographic axes. The tetragonal structure of TiO2 has been proved by powder X-ray diffraction. The floating zone method has been found as a very suitable and effective method to grow anatase single crystals.
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Growth of single crystals in material research
Bendová, Anežka ; Pospíšil, Jiří (advisor) ; Vališka, Michal (referee)
Title: Growth of single crystals in material research Author: Anežka Bendová Department: Department of Condensed Matter Physics Supervisor of the bachelor thesis: RNDr. Jiří Pospíšil, Ph.D., Department of Condensed Matter Physics Abstract: The subject of this bachelor thesis was a comparative study of single crystal growth methods. The growth of single crystal materials of various classes was tested by multiple methods, especially by growth from supersaturated solution, Bridgman method, Czochralski method and Floating Zone method. Properties and parameters of various techniques were tested and optimized for achieving the highest possible quality of single crystals which parameters were tested by electron microscopy and X-ray diffraction techniques. Suitability and limitations of each method are discussed from the point of size, crystallinity, chemical composition of obtained single crystals and from workload and complexity of the instrumentation. Keywords: Single crystal, Flux, Bridgman method, Czochralski method, Floating Zone method
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Characterization of perovskite solar cell materials by transient techniques
Nakládal, Martin ; Zmeškal, Oldřich (referee) ; Novák, Vítězslav (advisor)
This thesis deals with the study of the lifetime of charge carriers in perovskite single crystals. The principle of perovskite solar cells is formulated, their main structures are characterized and the history of the development of perovskite solar cells is summarized, especially in terms of efficiency. The properties of perovskite single crystals with perovskite solar cells are compared. For measurement purposes, transient methods, impedance spectroscopy, load characteristics and the dependence of sensitivity and photocurrent on the wavelength of incident radiation are described. The practical part deals with the method of measuring and evaluating the lifetime of charge carriers in the investigated perovskite single crystals.
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Growth of single crystals and their basic characterization.
Hanzlíková, Kateřina ; Pospíšil, Jiří (advisor) ; Matěj, Zdeněk (referee)
Basic methods of single crystals growth have been studied in this bachelor thesis. The preparation of anatase and ruby single crystals has been realized by floating zone method in different compositions of the surrounding atmosphere. Crystallinity of prepared materials has been verified by Laue method. The same method has been used for orientation of the prepared single crystals along the principal crystallographic axes. The tetragonal structure of TiO2 has been proved by powder X-ray diffraction. The floating zone method has been found as a very suitable and effective method to grow anatase single crystals.
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Performance of YAG:Ce Scintillators for Low-Energy Electron Detectors in S(T)EM
Lalinský, Ondřej ; Bok, Jan ; Schauer, Petr ; Frank, Luděk
Cerium activated single crystals of yttrium aluminium garnet (YAG:Ce) Y3-xCexAl5O12 are widely used as scintillators in electron detectors for S(T)EM. Nowadays, it is sometimes necessary to detect low-energy electrons without post-acceleration. In such cases, extremely sensitive detectors are required that are able to detect even electrons with energies of only hundreds of eV while avoiding charging of the scintillator surface. However, commonly used scintillators strongly lose their light yield with the decrease of the incident electron energy. Moreover, a thinner conductive layer on the scintillator surface has to be used to allow low-energy electrons to pass through. Possible charging of the surface negatively affects its cathodoluminescence (CL) light yield. The low-energy electron excitation takes place closer to the scintillator surface where damage can be expected owing to its preparation, which also reduces the CL light yield. The aim was to study the influence of the scintillator and its conductive layer on the low-energy electron detection efficiency.
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Innovation possibilities of scintillation electron detector for SEM
Schauer, Petr ; Bok, Jan
To evaluate performance of a scintillation detection system for SEM, it is necessary to consider many scintillator parameters. Various attributes of the scintillator for the SEM electron detector are listed in. The very important parameters are those affecting the detective quantum efficiency (DQE) which is primarily a measure of image noise. Not a less important indicator of image quality is the modulation transfer function (MTF) which describes the ability to show fine image details. Therefore, using a scanning imaging system, the detector bandwidth, which is given especially by the scintillator decay time, is the key to the good MTF. Currently, the YAG:Ce single crystal scintillator (introduced already in 1978 having somewhat limiting decay characteristic is the most frequently used scintillator in the SEM. The aim of this paper is to outline possibilities of scintillator innovation to get the improved MTF and DQE.
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