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Optimization of organic solar cells
Kratochvíl, Matouš ; Novák, Vítězslav (referee) ; Weiter, Martin (advisor)
This diploma thesis focuses on the preparation of large-scale organic solar cells using techniques compatible with large volume production. The theoretical part consists of research summarizing the basic theoretical background of the function of organic solar cells and the current state of investigation of the shift from laboratory to large-scale production. The experimental part deals with the optimization of methods of preparation of layers of structure of solar cells, which can be converted into industrial scale.
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Materials with FR/NIR photoluminiscence
Chovanec, Filip ; Kratochvíl, Matouš (referee) ; Vala, Martin (advisor)
This bachelor thesis is focused on issues of materials, whose fluorescence maximum is located in regions of the far-red (FR), which is in range from 700-800 nm or near-infrared (NIR), from 800-2500 nm, electromagnetic radiation. Materials, which this thesis is focused on, are organic molecules with charge transfer (CT) system. They are based on electron-donor and electron-acceptor groups located on the opposite sides of the same molecule. Diphenylamine behaves as electron-donor. This moiety is connected to different batch of atoms, which figure as electron-acceptor group. Connection is formed by -conjugated bridge of diphenyl stilbene or dixylil stilbene. Such a variable system has an optionally adjustable magnitude of charge transfer phenomenon, and it is reflected in the fluorescence maximum. Knowledge about fluorescence of these molecules, phenomena accompanying and outrunning this radiation, was acquired through the theoretical research. Strategies, how to set such a DA system or how to set up molecules with FR/NIR fluorescence were also obtained. Practically, characterization and dependence of fluorescence maximum on structure of these molecules, as well as dependence on solvent were determined by fluorescence spectroscopy. Photoluminescence quantum yield was calculated from emission and excitation spectra and studied how structural changes changed values of this quantum yield and fluorescence lifetime too. The result of the bachelor thesis was the finding, that the stronger the charge transfer phenomenon occurs in the molecule, the greater bathochromic shift of emission spectra was observed. At the same time, it was discovered that it was the case of liquid sample, solid samples had shown smaller bathochromic shift.
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Novel materials for organic and hybrid electronics and photonics
Kratochvíl, Matouš ; Yumusak,, Cigdem (referee) ; Táborský, Petr (referee) ; Weiter, Martin (advisor)
Obor organické elektroniky nabízí jedinečnou možnost masové výroby levné a ekologicky přívětivé elektroniky. Otevírá dveře novým funkcím a tvarům zařízení, které standardní elektronika na bázi kovu a křemíku neumožňuje Možnosti dané povahou organických látek a pokrok ve výzkumu syntézy nás zásobují novými materiály pro fotonické aplikace. Hlavní motivací této práce je hledání nových materiálů a zkoumání vztahu mezi jejich molekulární (a krystalickou) strukturou a vlastnostmi. Tato práce je zaměřena na studium optických a/nebo elektrických vlastností nových materiálů pro fotonické aplikace. Materiály prezentované v práci jsou organické i hybridní organicko-anorganické, u nichž je snaha získat to nejlepší z obou světů. Výzkum prezentovaný v této práci se skládá ze tří samostatných částí, které jsou propojeny cílem studovat vztah mezi strukturou materiálu a jeho vlastnostmi a metodami používanými ke studiu těchto vlastností. První část si klade za cíl představit materiály vykazující účinnou fluorescenci v pevné fázi (Solid-State Fluorescence, SSF). V této práci jsou prezentovány dvě série materiálů vykazujících SSF. Barva emise je řízena změnami skupin přitahujících elektrony v push-pull systémech molekul. Výsledky ukazují efektivní (>10%) emise pokrývající většinu viditelného spektra (~450–650 nm). Druhá část prezentovaného výzkumu zkoumá vliv thionace na známou skupinu nízkomolekulárních polovodičů – diketopyrrolopyrrolů (DPP). Prezentované výsledky ukazují ve studovaných molekulách výraznou preferenci n-typové chování následkem thionace, s řádovým zvýšením pohyblivosti elektronů, a také působivě nízko ležící hladiny LUMO (~ 4,5 eV). Třetí část uvedených výsledků je zaměřena na perovskitové materiály pro fotonické aplikace. Hybridní materiál – organo-olovnato-halogenidový perovskit je již téměř půldruhého desetiletí v centru pozornosti výzkumníků v oblasti pokročilé fotoniky. Perovskitové solární články prokazují pozoruhodnou účinnost, avšak jejich využití stále brání problémy se stabilitou. V této práci je prezentována studie stability jako referenční bod pro další výzkum v této oblasti a pro získání vhledu do procesů ovlivňujících stabilitu perovskitových materiálů a solárních článků. Následně je navržen a otestován přístup ke zvýšení stability a výkonu článků, využívající materiály studované ve druhé studii.
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Preparation and characterization of thin organic photovoltaic layers
Kratochvíl, Matouš ; Zmeškal, Oldřich (referee) ; Weiter, Martin (advisor)
This bachelor thesis focuses on preparation of organic solar cells and characterization of their properties. The theoretical part consists of literature search focused on current findings in this area and basic theoretical knowledge of the mechanisms of solar cells functioning. The experimental part of the thesis deals with the preparation of solar cells, targeting large cells, and characterization of basic electrical and optical properties of these cells.
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Pi-conjugated molecules exhibiting singlet fission
Sahuľ, Martin ; Kratochvíl, Matouš (referee) ; Vala, Martin (advisor)
This bachelor thesis focuses on characterisation of novel materials designed for use in future generation of photovoltaic cells. Examined materials were derivates of diketopyrollopyroles, in which the process of singlet fission was confirmed. Using fluorescence reference standards, the correctness of research methodology was confirmed. Measurements of basic optical and fluorescence characteristics such as absorption, excitation and emission spectra, wavelengths of their respective maximum values and quantum yields were made. Since the studied materials only differed in the number of bromine atoms, the effect of bromation on the properties of molecules was discussed from the acquired values. It was found, that substituted bromine atoms increase the excitation and emission wavelengths of diketopyrollopyroles, therefore decreasing the energy needed to excite the molecule. Next, a new method using fluorescence measurements in a magnetic field that can be used for a quick analysis of singlet fission was developed. Measurements made using this method confirmed the occurrence of singlet fission in rubrene as well as in studied materials. Performed measurements gathered new useful information for the design of new molecules and further improvement of the developed method.
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Host-guest systems for efficient infrared solid-state emission
Rottenberg, Vojtěch ; Smolka, Rastislav (referee) ; Kratochvíl, Matouš (advisor)
The goal of this bachelor thesis is to compile a brief research on solid-phase fluorescence, to find suitable molecules for the preparation of host-guest systems that exhibit high quantum yields of solidphase fluorescence in the infrared region and to analyze them. These systems consist of a predominant molecule (host) that exhibits high quantum yields of fluorescence and a quantitatively less abundant molecule (guest) that exhibits fluorescence in the infrared part of the electromagnetic spectrum. The following molecules were chosen: (E)-N,N-diphenyl-4-(2-(5'-vinyl-[1,1':4',1''-terphenyl]-2'- yl)vinyl)aniline (–V) and (E)-5'-(4-(diphenylamino)styryl)-[1,1': 4',1''-terphenyl]-2'-carbonitrile (–CN) as a guest molecule and (E)-2-((5'-(4-(diphenylamino)styryl)-[1,1':4',1''-terphenyl]-2'- yl)methylene)malononitrile (–DCV) as a guest molecule. For sample analysis, emission and excitation spectra were measured using a fluorophore, quantum yields using an integrating sphere, and fluorescence lifetimes using the time-correlated single photon counting (TCSPC) method. From the spectral analyses and quantum yields, it was determined that the molecule (E)-5'-(4- (diphenylamino)styryl)-[1,1':4',1''-terphenyl]-2'-carbonitrile (–CN) is a suitable guest molecule, (E)-2- ((5'-(4-(diphenylamino)styryl)-[1,1': 4',1''-terphenyl]-2'-yl)methylene)malononitrile (–DCV) is not a suitable guest molecule and the suitability of using (E)-N,N-diphenyl-4-(2-(5'-vinyl-[1,1':4',1''- terphenyl]-2'-yl)vinyl)aniline (–V) as a guest molecule is inconclusive.
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Resonance energy transfer in the study of polymer-vesicle interaction
Jízdná, Zuzana ; Kratochvíl, Matouš (referee) ; Mravec, Filip (advisor)
The presented bachelor's thesis dealt with the subject of preparation of cationic vesicular systems, formed by the CTAB and SDS surfactants, in order to study their mutual interaction with the hyaluronan polymer using Förster resonance energy transfer measurements. First, concentration series of vesicular systems with fluorophores were prepared. DPH, perylene and fluorescein were used as fluorophores. Afterwards, the fluorescence lifetime of selected fluorophores was measured by the TCSPC method. Then, the characteristics of the prepared vesicular systems were measured using the DLS and ESL methods. For the final measurement of the interaction between the vesicle and the polymer, a vesiculation solution was chosen based on all the measurements carried out, which contained DPH with a concentration of 3·10-5 mol/l and hyaluronan. Two molecular weights of hyaluronan (300 and 900 kDa) were tested at mass concentrations of 1, 5, 10, 50 and 100 mg/l. The measurement confirmed their mutual interaction, thus this system could find application in the medical sector.
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Organic luminophores with long wavelenght emission
Kolaříková, Adéla ; Kratochvíl, Matouš (referee) ; Vala, Martin (advisor)
This bachelor thesis studies the possibility of achieving intense fluorescence in the red region of the spectrum using Förster resonance energy transfer (FRET) in nanoparticles. First, the optical properties of organic molecules that could be suitable for the creation of a so-called host-guest (HG) system consisting of an acceptor-donor pair were studied. The molecules studied were based on derivatives of diphenylstilbene containing the electron-donor group diphenylamine (DPA-DPS), which is linked to a differing electron-acceptor group via a -conjugated double bond system. The acceptor groups used, i.e., indandione (-IOO), vinyl ( V) and di(methoxycarbonyl)vinyl (-V(COOMe)2), differ from each other in structure and polarity, which was reflected by a change in the position of the fluorescence spectrum. In the HG systems studied, DPA-DPS-IOO always served as the guest (G1) and DPA-DPS-V and DPA-DPS-V(COOMe)2 always served as the host (H1 or H2). Nanoparticles from these substances (G1H1 and G1H2) were prepared by the nanoprecipitation method. FRET was observed for both of these systems. Upon excitation of the matrix, the energy was transferred to the guest G1, which subsequently fluoresced in the long-wavelength region. Furthermore, an increase in the quantum yield of the guest fluorescence was also observed for the nanoparticles formed from the G1H2 system, from 7% (powder) and 3.1% (nanoparticles) to 14% compared to both the powder form and nanoparticles formed from the guest alone. No increase in the quantum yield of guest fluorescence was observed for the nanoparticles of the G1H1 system. The results indicated that FRET can be an effective tool in developing nanoparticles exhibiting intense long-wavelength fluorescence for imaging.
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Electrochemical evolution of hydrogen peroxide for biotechnological applications
Runštuková, Nikola ; Kratochvíl, Matouš (referee) ; Ehlich, Jiří (advisor)
This master‘s thesis deals with the connection of two distinct fields, electrochemistry and biotechnology, where electrochemically generated peroxide was subsequently used in bacterial cultivation. The peroxide was synthesized in an electrolytic cell by reducing oxygen at the cathode to which suitable electrical potential was applied. The aim of this thesis was to investigate the dependence of the amount of hydrogen peroxide produced on a few selected parameters, such as cathode potential, electrode material, the geometry of the measuring cell, or the stirring speed, and then to apply these findings in the continuous stressing of the bacterium Cupriavidus necator H16, in order to increase the production of polyhydroxyalkanoates. The selected parameters were first tested in small-scale measuring cells and then experiments were carried out on a larger scale, in Erlenmeyer flasks. During the experiments, the amount of electric current produced was measured and also the peroxide concentration was examined spectrophotometrically along with the oxygen concentration measured by using an optical sensor. Based on the obtained results, bacteria were cultivated in flasks with a built-in system of steel electrodes, due to which oxidative stress in the form of in situ generated hydrogen peroxide was continuously applied. The bacterial cultures were evaluated by measuring the change in optical density, gravimetric analysis and GC-FID analysis. It was found that even small amounts of hydrogen peroxide (~25 M) can induce a stress response in the organism in the form of increased polyhydroxybutyrate (PHB) synthesis. A percentage increase in the PHB content of the biomass was achieved, however, the overall polymer yield was lower due to lower biomass growth.
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