|
|
Energetic interactions between electon-donors and acceptors for photovoltaic solar cells
Hrabal, Michal ; Heinrichová, Patricie (referee) ; Vala, Martin (advisor)
The aim of this bachelor thesis is to study a charge transfer between materials that could be used for development of new organic solar cells. The charge transfer is studied by a quenching of fluorescence. The thesis is divided into theoretical and experimental part. The basic knowledge needed for correct interpretation of measured data is summarized in the first part. Special attention is paid to the photoinduced electron transfer. Then, the processes of conversion of solar energy into electric energy and properties of potential materials are also discussed. Architecture of organic solar cells is mentioned in the end of the work. The practical part contains the study of quenching of fluorescence by fullerene derivatives and compares the efficiency of quenching to standard materials.
|
|
|
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.
|
|
|
Charge transport in DNA
Drevený, Lukáš ; Mravec, Filip (referee) ; Vala, Martin (advisor)
In this bachelor thesis were investigated charge transport (CT) through a duplexes of DNA by stationary fluorescence spectroscopy, with a fluorescent analogue of adenine - 2-aminopurine (Ap), as fluorescent probe. The aim of study was an influence of changes in the structure of duplexes DNA:DNA or DNA:RNA and effect of the presence of Hg(II) in double-stranded DNA:DNA containing a mutation thymine-thymine in the chain, in the efficiency of charge transfer along the DNA strand. Firstly, in the experimental part was investigated a efficiency of incorporation of Ap into the DNA strand from an excitation spectra and secondly, from the integrals of the emission spectras the quenched factor was calculated. It was found that the Ap can be better incorporated into the chain of DNA:RNA, which is not as rigid as a string of DNA:DNA and thus may be better accepted by the nearby bases in the chain; furthermore, it was found that the photo-induced charge transfer (PET) through the DNA strand sharply drops after exceeding a temperature corresponding with melting point of DNA chain, at which the string of DNA is unraveling. It was also found that the presence of Hg(II) in the chain of DNA:DNA does not adversely affect a charge transfer, but on the contrary, the string is after integration of Hg(II) into the chain more stable and the melting point is shifted to higher temperatures. In this thesis it was proved that photoinduced charge transfer is very sensitive process and could be used for detection of even tiny changes in the structure of nucleic acids.
|
|
|
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.
|
|
|
Charge transport in DNA
Drevený, Lukáš ; Mravec, Filip (referee) ; Vala, Martin (advisor)
In this bachelor thesis were investigated charge transport (CT) through a duplexes of DNA by stationary fluorescence spectroscopy, with a fluorescent analogue of adenine - 2-aminopurine (Ap), as fluorescent probe. The aim of study was an influence of changes in the structure of duplexes DNA:DNA or DNA:RNA and effect of the presence of Hg(II) in double-stranded DNA:DNA containing a mutation thymine-thymine in the chain, in the efficiency of charge transfer along the DNA strand. Firstly, in the experimental part was investigated a efficiency of incorporation of Ap into the DNA strand from an excitation spectra and secondly, from the integrals of the emission spectras the quenched factor was calculated. It was found that the Ap can be better incorporated into the chain of DNA:RNA, which is not as rigid as a string of DNA:DNA and thus may be better accepted by the nearby bases in the chain; furthermore, it was found that the photo-induced charge transfer (PET) through the DNA strand sharply drops after exceeding a temperature corresponding with melting point of DNA chain, at which the string of DNA is unraveling. It was also found that the presence of Hg(II) in the chain of DNA:DNA does not adversely affect a charge transfer, but on the contrary, the string is after integration of Hg(II) into the chain more stable and the melting point is shifted to higher temperatures. In this thesis it was proved that photoinduced charge transfer is very sensitive process and could be used for detection of even tiny changes in the structure of nucleic acids.
|
|
|
Energetic interactions between electon-donors and acceptors for photovoltaic solar cells
Hrabal, Michal ; Heinrichová, Patricie (referee) ; Vala, Martin (advisor)
The aim of this bachelor thesis is to study a charge transfer between materials that could be used for development of new organic solar cells. The charge transfer is studied by a quenching of fluorescence. The thesis is divided into theoretical and experimental part. The basic knowledge needed for correct interpretation of measured data is summarized in the first part. Special attention is paid to the photoinduced electron transfer. Then, the processes of conversion of solar energy into electric energy and properties of potential materials are also discussed. Architecture of organic solar cells is mentioned in the end of the work. The practical part contains the study of quenching of fluorescence by fullerene derivatives and compares the efficiency of quenching to standard materials.
|
guest ::
