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Charge carrier transport in conjugated polymers with controlled morphology
Acharya, Udit ; Pfleger, Jiří (advisor) ; Gmucová, Katarína (referee) ; Kalvoda, Ladislav (referee)
The growing demand for new materials for electronics that could offer novel functionalities for everyday use and for special applications in healthcare and industry, together with concerns about energy consumption, have stimulated an increasing research on electrical properties of conjugated macromolecules. The superiority of these macromolecules arises from their inherent properties based on alternating single and double bonds. In this thesis, charge transport in conducting polymers, namely polypyrrole, poly(p-phenylenediamine) and polyaniline, and their composites was investigated with respect to various morphology controlled by oxidant-to-monomer ratio, composite composition and other modifications of their synthesis. Based on a combination of various experimental techniques, like impedance spectroscopy, electron microscopy, electrochemical and optical measurements, the relation between the morphology and charge carrier transport was elucidated. The variable range hopping was found to be a dominant mechanism in the studied polymers. Additionally, metallo-supramolecular polymers have been prepared that offer well-organized structures by complexation of conjugated segments with metal ions. The spectro-electrochemical studies revealed electrochromic phenomena in these polymers. By optimization of...
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Preparation and properties of α,ω-bis(terpyridyl)oligothiophenes and related supramolecular polymers
Štenclová, Pavla ; Svoboda, Jan (advisor) ; Pfleger, Jiří (referee)
Presented diploma thesis describes synthesis of novel α,ω-bis(terpyridyl)bithiophenes and α,ω-bis(terpyridyl)terthiophenes with alkyl substituents on thiophene rings. The α,ω- -bis(terpyridyl)oligothiophenes were prepared using Suzuki-Miyaura coupling of 4'-(5- -bromo-3-alkylthien-2-yl)terpyridine with 2,5-thiophenediboronic acid and 2,2'-bi(1,3,2- -dioxaborolane), respectively. The succesfull transformation of 4'-(5-bromo-3-alkylthien-2- -yl)terpyridine to corresponding bis(terpyridyl)oligothiophenes was confirmed by NMR and HR-MS analyses and IR spectroscopy. UV-vis spectroscopy, excitation and emission photoluminescence (suplemented with determination of photoluminescence quantum yields) and cyclic voltammetry were used to study spectroscopic and redox properties of novel α,ω-bis(terpyridyl)oligothiophenes and previously prepared unsubstitued α,ω-bis(terpyridyl)bithiophene and α,ω-bis(terpyridyl)- terthiophene. Interaction of zinc ions with ligands soluble in tetrahydrofurane was studied using UV-vis spectroscopy and emission photoluminescence spectroscopy. Main-chain supramolecular polymers were sucessfully prepared from four soluble ligands and zinc ions. Properties of prepared polymers were studied using UV-vis spectroscopy, excitation and emission photoluminescence spectroscopy and IR...
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Study of electric and photoelectric effects in organic semiconductors
Chomutová, Radka ; Toušek, Jiří (advisor) ; Pfleger, Jiří (referee)
This work studies various electrical properties of polymer layers of polyaniline, polythiophenes and poly(((benzothiadiazol)4,7-di(thien-2-yl)-5,6-difluoro-2,1,3-benzothiadiazol). Goal of this work is to determine electrical and photoelectrical properties as are electric conductivity, mobility of the free charge carriers, work function of the electrons and diffusion length of excitons. Conductivity was obtained through current and voltage contacts, mobility was measured by CELIV method (charge extraction by linearly increasing voltage). To determine work function a Kelvin probe was built and utilized. Diffusion length of excitons was determined from photovoltage spectrum formed by illuminating space charge region of the polymer.Space charge region on surface of the polymer can arise spontaneously or by laying suitable contact electrode. Powered by TCPDF (www.tcpdf.org)
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Materials containing conducting polymers
Blinova, Natalia ; Stejskal, Jaroslav (advisor) ; Pfleger, Jiří (referee) ; Žigon, Majda (referee)
l. Aims of the Thesis The goal of the Thesis is ůeprlaaraiior ..f .'a:ious norpho|ogies produced by conductingpoly.rners, riz. polvaniline (P{\Ji. the.-onrol of ce.n,tu.-:rrrl. a.rC the understanding of the chemistrv of aniline oxidatton. In rhese studies. three ditTerenr drrectiors have been developed. The first pan of the Thesrs rs focused on the slnthesrs of p.{NI. The oprrmum conditions for preparation of all forms available: powders, thin films, and colloidal dispersrons with respect to the morphology' ýeld, and conductiúý have been described. A systematic study of PANI protonated with phosphoric acid as well as a comparative study of the preparation of PANI and polypynole (PPy) have been made. The oxidation of aniline with noble-merals compounds, such as silver nitrate, the effect of the medium acidity, concentration of reacunts and the possible effect of daylight have been invesrigated. A new approach for the synthesis of PANI with separated reactants, aniline and an oxidant, is described in the second part of the Thesis. Various studies have been presented here to investigate the mechanisms of such reactions. The concept of coupled PANl-assisted redox reaction by means oftransport ofelectrons and protons through conducting PANI membrane has been demonstrated. A possible electron-ion-coupled...
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The preparation of functionalized nonplanar aromatics and study of their physical properties at nanoscale
Mildner, Daniel ; Starý, Ivo (advisor) ; Pfleger, Jiří (referee)
The Thesis studies single-molecule conductance of helicenes by means of scanning tunneling microscopy-based break-junction (STM-BJ) device. Particularly, it focuses on a question how the conductance of helicenes changes with the increased number of aromatic rings. Firstly, Introduction about helicenes is given, namely their syntheses, properties, and applications. Further, methods of single molecule analysis, namely scanning tunneling microscope and break-junction techniques, are discussed with emphasis on organic molecules and their conductance. In the next part, Results and discussion, the synthesis of helicenes is presented and their single-molecule conductance is studied. Through STM-BJ measurements, decreasing trend in molecular conductance with increasing length of a molecular wire is proved. Above that, the correlation of experimental data with theoretical calculations and X-ray diffraction experiments confirms that a single-molecule conductance is measured. Finally, the Experimental section provides detailed description of experimental procedures both for organic and physical experiments.
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Optimization of multilayer structures for organic electronics
Paruzel, Bartosz ; Pfleger, Jiří (advisor) ; Kalvoda, Ladislav (referee) ; Syrový, Tomáš (referee)
Organic electronic devices such as organic field effect transistors (OFETs), light- emitting diodes (OLEDs), resistive memory elements or organic solar cells have attracted an increasing attention in recent years due to the vision of a low-cost and large-scale production of printable electronics. Many papers published during the last decade focused on the intrinsic properties of organic conductors, semiconductors and dielectric materials. Since most of the devices consist of multilayer structures the mutual influence of the processes that take place in the particular layers are important for the functionality of the whole device. This work is aimed to contribute to the characterization and understanding of the mutual interactions of individual layers in the multilayer structures of organic devices. The main achievements of this work can be listed as: (i) Optimization of the thermal stability and dielectric properties of cyanoethylated polyvinylalcohol (CEPVA) high-k dielectric by the crosslinking reaction with the low molecular weight materials or mixing with a high Tg polymer. (ii) Finding possible phenomena in the CEPVA polymer dielectric that influence the charge carrier transport in the OFET active channel made of bis(triisopropylsilylethynyl) pentacene organic semiconductor, using a...
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Synthesis and Functionalization of Phenacenes Containing δ-Lactam Ring.
Váňa, Lubomír ; Církva, Vladimír ; Pfleger, Jiří ; Storch, Jan
This work is aimed at the development of a new efficient methodology towards the synthesis of various aza[5]phenacenes containing δ-lactam ring in their structure. Possibilities of their functionalization or derivatization are also discussed, along with complexation properties of suitable aza-derivatives as ligands in transition-metal complexes. The resulting compounds are investigated in terms of their material properties, especially for the formation of thin film structures capable of an efficient semi-conductivity or their potential application as photoluminescent complexes in OLEDs.
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