|
|
Novel diketopyrrolopyrroles for organic photovoltaics
Hrabal, Michal ; Zmeškal, Oldřich (referee) ; Vala, Martin (advisor)
The aim of this diploma thesis is to conduct optical and photovoltaic characterization of derivatives of diketopyrrolopyrrole (DPP) as materials suitable for fabrication of bulk heterojunction organic solar cells. The charge transfer from donor material (DPP) to acceptor material (PCBM) is studied by a quenching of fluorescence. The photovoltaic response is studied by current – voltage characteristic which can tell us crucial parameters such as shor circuit current density Jsc, open circuit voltage Voc, fill factor FF and power conversion efficiency PCE. Optical characterization was carried out for symmetrical DPP derivatives (U69 and U97) which both contained diphenylaminstilbene moiety and differed in N-alkyl group. On the other hand photovoltaic characterization was conducted for analogous but asymmetrical materials (U70 and U99). Material U29 was characterized as well but its properties proved to be very poor. Both these characterizations tell us that materials with shorter solubilization groups (U69 and U99) are more suitable candidates. Achieved PCE for U70 was 0,74 % and for U99 up to 1,39 %. From these values one can say that small molecule organic materials can be used for fabrication of solar cells.
|
|
|
Organic solid state lasers
Koutný, Jan ; Salyk, Ota (referee) ; Vala, Martin (advisor)
The aim of this thesis is the preparation and characterization of model components for organic thin-film solid-state lasers. The theses focuses on comparing different methods of determining the threshold energy, which leads to an amplified spontaneous emission of the studied derivative diketo-pyrrolo-pyrrole. The theoretical part is devoted to a summary of knowledge on the interaction of light with matter and lasers with a focus on organic solid-state lasers. The practical part is focused on preparation of model components for organic solid-state lasers, modification of apparatus for their characterization, comparison of evaluation methods for determining the threshold energy and study of the effect of different conditions of components preparation.
|
|
|
Development of a sensing platform for the study of physiological functions of living cells
Marková, Aneta ; Víteček, Jan (referee) ; Vala, Martin (advisor)
The aim was to develop a sensing platform on the base of organic electrochemical transistor (OECT). The focus was on the preparation of proper electrode system and on optimalization of properties of thin layer of organic semiconductor. As a base, commercial glass substrates with integrated indium-tin oxide electrodes were chosen. Thin layers were prepared from organic semiconductor poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) by spin-coating. Four formulations of material were studied. Layers with different thickness were prepared and the dependence of transconductance on the thickness of the layer and ratio of width and length was observed. The degradation of electrode system was solved by galvanic plating with gold. Attention was also paid to modifications to PEDOT: PSS. It has been found that the optimal layer thickness for use in sensors is approximately 150 nm. By reducing the series resistance by using a silver paste, the transconductance of 23 mS was obtained for the Ink 2, for the Ink 3 the transconductance was 44 mS. Sensoric platforms with these transconductances can be used for detection of physiological functions of electrogenic cells, e.g. cardiomyocytes.
|
|
|
Self-cleaning ability of organic photo-active layers
Těthal, Vít ; Vala, Martin (referee) ; Veselý, Michal (advisor)
In this paper, methodes of determination of singlet oxygen (decolorization methodes, luminiscence detection, reaction with anorganic compounds, electon paramagnetic resonation, detecting of singlet oxygen luminiscence, detecting of absorption in IR region) and determination of efectivity of photoactive layers (photobleaching of dye aqueous solution, photodegradation of a solid fatty deposit, photoreduction of an organic dye, photooxidation of sodium salt of terephtalic acid, degradation of 1,3-diphenylisobenzofuran (DPIBF), degradation of diketopyrrolopyrrole (DPP), degradation of acridine orange) are summarized, including principle and procedure. In experimental part, 2 of these methodes (DPIBF and DPP degradation) were chosen and tested. Reaction rate constant and conversion were measured. It was found out that DPIBF methode is quick, reliable and reproducable.
|
|
|
Work-life balance in a selected company
Vala, Michal ; Konečný, Štěpán (referee) ; Hornungová, Jana (advisor)
The bachelor thesis deals with the work-life balance in a selected company. The thesis is divided into three parts. The first part is theoretical, in which the issue of human resource management and the topic of work-life balance are approached. Furthermore, some legislative instruments and flexible work arrangements supporting work-life balance are described. The second part is the analytical part, which contains three case studies and the results of a questionnaire survey in a selected company. The last part is about suggested measures. It contains recommendations in the field of work-life balance based on the questionnaire survey. Following the implementation of these recommendations, the work-life balance of employees in the company should improve.
|
|
|
Materials for organic electronics
Skrášek, Martin ; Zmeškal, Oldřich (referee) ; Vala, Martin (advisor)
The work contains literature search on organic electronics, especially organic solar cells. There is described in detail their principle of function and used materials. Also there are mentioned possibilities of synthesis of conjugated systems for this applications and methods of their structural, optical and electrical characterization. In experimental section and discussion is introduced synthesis of five new, various substituted derivates of benzylidenaniline and their characterisation together with another seven derivates, whose synthesis has been described in bachelor thesis. There is investigated influence of substituents to chemical shift of hydrogen on imine bridge and to position of absorption peaks in UV-Vis spectra. There also has been found method for fabrication of thin layers and solar cells with bulk heterojunction have been fabricated. Next, V-A characteristics and impedance spectra of the cells were recorded. According to obtained results, investigated systems act as photodiodes and in case of three derivates the photoinduced increase of electric current has been observed. But for application in solar cells it is necessary to shift the position of absorption spectra towards longer wavelengths.
|
|
|
Study of possibilities of increasing the biocompatibility of organic semiconductor surfaces
Malečková, Romana ; Šafaříková, Eva (referee) ; Vala, Martin (advisor)
This bachelor thesis deals with the possibility of biocompatibilization of organic semiconducting polymer PEDOT:PSS using RGD peptide for the construction of biosensors. Samples were prepared and compared where the RGD peptide was bound directly, as well as samples with a peptide bound via crosslinker molecule sulfo-SANPAH. Whether the RGD peptide was bound to the substrate was determined by the method of measuring the contact angle of liquids with subsequent calculation of surface energy. The results were further verified by elemental analysis, infrared spectrometry and Raman spectroscopy.
|
|
|
Organic materials for bioelectronic applications
Bystřický, David ; Vala, Martin (referee) ; Weiter, Martin (advisor)
This thesis deals with characterisation of organic semiconductive materials. At first degradation temperatures were discovered by using thermogravimetric analysis. Then by using differencial scanning calorimetry were discovered changes in molecules depending on temperature. In the end of this thesis by OFET characterisation charge carrier mobilities were measured and their dependence on temperature.
|
|
|
Modelling of bioelectronic devices
Truksa, Jan ; Vala, Martin (referee) ; Salyk, Ota (advisor)
Tématem této práce je počítačové modelování organického elektrochemického tranzistoru (OECT). Pro vytvoření modelu bylo třeba vypočítat rozložení elektrického pole a koncentrace iontů elektrolytu. Výpočet byl proveden numericky pomocí metody konečných prvků. Bylo vypočítáno rozložení elektrického potenciálu na povrchu kanálu OECT, dále byly vypočítány změny vodivosti a výstupní proud OECT. Výpočty byly provedeny na osobním počítači pomocí komerčního softwaru COMSOL Multiphysics. Kvůli nedostatečnému výpočetnímu výkonu musel být model rozdělen na části a drasticky zjednodušen. Prezentované výsledky se liší od literatury, protože se nepodařilo správně modelovat saturaci tranzistoru. Odchylky od reálného chování OECT jsou pravděpodobně způsobeny zjednodušením modelu.
|
|
|
Friction of compliant contacts
Vala, Martin ; Galas, Radovan (referee) ; Nečas, David (advisor)
This bachelor’s thesis deals with the study of the friction of compliant contacts and parameters affecting it. First section of this thesis provides analysis of current problematics with friction and compliant materials. In the next section basic definition of friction, compliant material and compliant contacts is provided with an actual study of up-to-date articles. Last section of this thesis is discussion dealing with all the articles and pointing out the influencing parameters. Followed by potential research pathways.
|
guest ::
RSS feed.