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Characterization of graphene electrical properties on MEMS structures
Brodský, Jan ; Pekárek, Jan (referee) ; Gablech, Imrich (advisor)
This work presents basic properties of graphene, methods for its synthesis and methods for its characterization by Raman spectroscopy, two-point probe, four-point probe and van der Pauw measurements. The experimental part of this work describes the process of graphene oxide, reduced graphene oxide and graphene sample preparation and measurement of its current-voltage characteristic by two-point probe method. Subsequently, sample annealing in vacuum furnace is described in this work. The annealing is important for acquiring good electrical contact between the 2D material and electrodes. Sample analysis by Raman spectroscopy is performed. The last chapters of this work describe design and fabrication of MEMS structure. Such structure serves for characterization of graphene and other 2D materials.
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Study of optoelectrical properties of organic semiconductor thin film layers of phtalocyanines
Miklíková, Zdeňka ; Vala, Martin (referee) ; Zmeškal, Oldřich (advisor)
Diploma thesis is focused on the study of optoelectric properties of thin layers of organic materials based on phthalocyanines, which can be used as an active layer of photovoltaic cells. Especially are studied the properties of the thin active layers of PdPc and PdPc + IL on the glass or ceramic substrates with aluminium contact, which are prepared by material printing here. On the prepared samples were first measured current-voltage characteristics in the dark and in the light and then were measured impedance spectrums in the dark. The received results will be used to improve the properties and structures of photovoltaic cells.
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Study of electrical and dielectric properties of thin polymer films
Miklíková, Zdeňka ; Novák, Vítězslav (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 substrate, which consist of a thin active layer of mixture ZnPc/PCBM with Al or Au contact. On the selected samples were first measured current-voltage characteristics in the dark and during the exposure then on the selected samples were measured frequency dependences (impedance spectra) in the dark and finally on the selected samples were measured relaxation characteristics (transient response analysis – current dependences on time at constant voltage) in the dark. The measured data for transient measurement 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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Electrical characterization of a unipolar transistor with a graphene channel
Žeravík, František ; Lednický, Tomáš (referee) ; Gablech, Imrich (advisor)
This work deals with basic properties of graphene, methods of its synthesis, doping, transfer, characterization and description of basic properties and fabrication of field-effect transistor with graphene channel. The practical part focuses on electrical characterization of a field-effect transistor with graphene channel. Concretely on measuring the channel resistance, its dependence on gate voltage, finding the Dirac point and determining the dependence of the channel conductivity on the annealing lenght. Lastly, the shift of the Dirac point and the change of the electrical properties of graphene during bending of a MEMS structure with a unipolar transistor with a graphene channel are investigated.
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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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Electrical characterization of a unipolar transistor with a graphene channel
Žeravík, František ; Lednický, Tomáš (referee) ; Gablech, Imrich (advisor)
This work deals with basic properties of graphene, methods of its synthesis, doping, transfer, characterization and description of basic properties and fabrication of field-effect transistor with graphene channel. The practical part focuses on electrical characterization of a field-effect transistor with graphene channel. Concretely on measuring the channel resistance, its dependence on gate voltage, finding the Dirac point and determining the dependence of the channel conductivity on the annealing lenght. Lastly, the shift of the Dirac point and the change of the electrical properties of graphene during bending of a MEMS structure with a unipolar transistor with a graphene channel are investigated.
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Characterization of graphene electrical properties on MEMS structures
Brodský, Jan ; Pekárek, Jan (referee) ; Gablech, Imrich (advisor)
This work presents basic properties of graphene, methods for its synthesis and methods for its characterization by Raman spectroscopy, two-point probe, four-point probe and van der Pauw measurements. The experimental part of this work describes the process of graphene oxide, reduced graphene oxide and graphene sample preparation and measurement of its current-voltage characteristic by two-point probe method. Subsequently, sample annealing in vacuum furnace is described in this work. The annealing is important for acquiring good electrical contact between the 2D material and electrodes. Sample analysis by Raman spectroscopy is performed. The last chapters of this work describe design and fabrication of MEMS structure. Such structure serves for characterization of graphene and other 2D materials.
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Properties of solar cells based on polymer-silicon junction
Pavlovič, Dean ; Toušek, Jiří (advisor) ; Křivka, Ivo (referee)
Title: Properties of solar cells based on polymer-silicon junction Author: Dean Pavlovič Department / Institute: Department of Macromolecular Physics Supervisor of the bachelor thesis: doc. RNDr. Jiří Toušek, CSc, Department of Macromolecular physics Abstract: The aim of this work is to study unconventional materials, namely conjugated polymers, as to be used for photovoltaic purposes. Among these polymers are polyaniline, derivative of polyphenylene vinylene and two derivatives of polythiophene. Four different methods are used to study some of the physical quantities of the samples, that should affect overall efficiency of solar power conversion. Firstly, I-V characteristics yields fill factor and indicates mechanism of charge transport. Method based on surface photovoltage (SPV) estimates diffusion length of the charge carriers - excitons. Impedance spectroscopy and particular method abbreviated CELIV both measure charge carrier mobility. Outcome of this work are the values of these quantities for some of the samples. Keywords: organic semiconductors, solar cells, mobility, diffusion length, current-voltage characteristic
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Study of optoelectrical properties of organic semiconductor thin film layers of phtalocyanines
Miklíková, Zdeňka ; Vala, Martin (referee) ; Zmeškal, Oldřich (advisor)
Diploma thesis is focused on the study of optoelectric properties of thin layers of organic materials based on phthalocyanines, which can be used as an active layer of photovoltaic cells. Especially are studied the properties of the thin active layers of PdPc and PdPc + IL on the glass or ceramic substrates with aluminium contact, which are prepared by material printing here. On the prepared samples were first measured current-voltage characteristics in the dark and in the light and then were measured impedance spectrums in the dark. The received results will be used to improve the properties and structures of photovoltaic cells.
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Study of electrical and dielectric properties of thin polymer films
Miklíková, Zdeňka ; Novák, Vítězslav (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 substrate, which consist of a thin active layer of mixture ZnPc/PCBM with Al or Au contact. On the selected samples were first measured current-voltage characteristics in the dark and during the exposure then on the selected samples were measured frequency dependences (impedance spectra) in the dark and finally on the selected samples were measured relaxation characteristics (transient response analysis – current dependences on time at constant voltage) in the dark. The measured data for transient measurement 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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