We had demonstrated that, by controlling and changing the temperature, reaction time and washing agents, the morphology and powder size of CuInSe2 can be altered considerably. CuInSe2 was synthesized by a solvothermal route as described by Y. Qian et al. By synthesizing nanorods, we can control the distance which the electrons are transported in hybrid solar cell with conjugated polymers. With the tuning of the band gap by controlling the nanorod length, we can increase the opportunity of orbits overlap between the CuInSe2 material and the PBO polymer matrix.. The synthetic temperature 1800C and reaction time 48 hrs are the best condition in our experiment. By using D.I water and ethanol as washing agents, we can find different morphology of spherical and nanowire. However, we fabricate hybrid solar cell by using these CuInSe2 powders in PBO conjugated polymers. By preparing hybrid solution in different concentration and controlling spin coating rate, we fabricate solar cells device successfully. From the I-V characteristics, we can get noticeable characteristics of diode. Then, we calculate the fill factor (F.F.) with the open-circuit voltage¡]Voc¡^and short-circuit current¡]Isc¡^

Thesis (Dipl.-Ing.)--Johannes Kepler Universität Linz, 2005. / Title from PDF title page (viewed Apr. 29, 2010). Abstract also in German. Includes bibliographical references (p. 60-63).

Philosophiae Doctor - PhD / The rapid increase in global energy demand in recent decades coupled with the adverse environmental impact of conventional fuels has led to a high demand for alternative energy sources that are sustainable and efficient. Renewable solar energy technologies have received huge attention in recent decades with the aim of producing highly efficient, safe, flexible and robust solar cells to withstand harsh weather conditions. c-Si has been the material of choice in the development of conventional inorganic solar cells owing to it superior properties, abundance and higher efficiencies. However, the associated high costs of Si processing for solar cells have led to a gravitation towards alternative organic solar cells which are cheaper and easy to process even though they suffer from stability and durability challenges. In this work, combination of both inorganic and organic materials to form hybrid solar cells is one of the approaches adopted in order to address the challenges faced by solar cell development.

No description available.

Solid-state dye-sensitized solar cells (ssDSCs) offer the possibility of high power conversion efficiencies (PCEs) of over 20%. However, after more than a decade of research, devices still barely reach over 7% PCEs. In this thesis, limitations to device performance are studied in detail, and solutions for future advancement are put forward. In the first part of the thesis, factors limiting charge generation are explored by studying the crystallization environment of mesoporous TiO2 self-assembled through block copolymers. It was found that the density and distribution of sub band gap states are a function of the synthesis conditions and critically affect the performance characteristics of the self-assembled titania used in ssDSCs. As a result, the self-assembled mesoporous oxide system presented in this thesis outperforms for the first time the conventional nanoparticle based electrodes fabricated and tested under the same conditions, with demonstrated PCEs of over 5%. In chapters 6, 7, and 8, the factors limiting the diffusion length and hence, the thickness of the fabricated devices, are carefully examined. Previous literature points towards insufficient pore-filling of the hole transporting material (HTM) as the main limiting factor. In chapter 6, a pore-filling study is shown where a new technique to evaluate the pore-filling fraction of the HTM in the conventional mesoporous metal oxide electrode is also presented and conclude that sufficient pore-filling of thick films can easily be achieved. Another usual strategy to extend the electron lifetime in the devices and thus, the charge diffusion length, involving thin film coatings of insulating metal oxides is examined in chapter 7, with satisfactory results for SnO2-based ssDSCs. The diffusion length can also be extended if the factors limiting the diffusion of charges through the device are identified and removed, as presented in chapter 8. Finally, a study on the stability of the ssDSC is presented in chapter 9. The developments achieved enable long term stability to be effectively targeted, and represent a key milestone towards commercial realization of ssDSCs.

Solar energy is the foremost power source of our planet. Driving photosynthesis on our planet for 3 billion years the energy stored in the form of fossil fuels also originates from the sun. Consumption of fossil fuels to generate energy is accompanied with CO2 emission which affects the earth's climate in a serious manner. Therefore, alternative ways of converting energy have to be found. Solar cells convert sunlight directly into electricity and are therefore an important technology for future electricity generation. In this work solar cells based on the inorganic semiconductor titanium dioxide and hole-transporting dyes are investigated. These type of solar cells are categorized as hybrid solar cells and are conceptually related to both dye-sensitized solar cells and organic solar cells. Light absorption in the bulk of the hole-transporting dye layer leads to the formation of excitons that can be harvested at the organic/inorganic interface. Two design approaches were investigated: 1) utilizing a multilayer of a hole-transporting dye and 2) utilizing a hole-transporting dye as light harvesting antenna to another dye which is bound to the titanium dioxide surface.  Using a multiple dye layer in titanium dioxide/hole transporting dye devices, leads to an improved device performance as light harvested in the consecutive dye layers can contribute to the photocurrent. In devices using both an inteface-bound dye and a hole-transporting dye, excitation energy can be transferred from the hole-transporting dye to the interface dye.

>Magister Scientiae - MSc / In a quest for low operational and maintenance cost solar cell devices, organic photovoltaics remain a potential source of energy worthy to be explored. In order to generate cost- effective electricity from solar energy, either the efficiency of the solar cells must be improved or alternatively the manufacturing cost must be lowered. The power conversion efficiency (PCE) of organic photovoltaics is influenced by the choice of electron acceptor material, the structure of the polymer, the morphology of the film, the interfaces between the layers and the ratio between the electron acceptor material and the polymer. Nevertheless, efficiency is still limited compared to conventional silicon based PV cells due to low mobility of charge carriers with a short exciton diffusion length in the active layer. Currently, hybrid solar cells have been considered as one of the most promising concepts to address the limited efficiency of organic solar cells. Therefore in this thesis ZnO nanoparticles were synthesized using hydrothermal assisted method. These nanoparticles were incorporated in the poly (3-hexylthiophene) (P3HT):[6,6]-phenyl-C61-butyric acid methyl ester (PCBM), and used as additional acceptors of electrons released from the polymer donor material, with the anticipation to increase the electron mobility, and ultimately the PCE. The thermo-gravimetric analyses revealed improved thermal stability of P3HT upon incorporating ZnO in the polymer matrix. X-ray diffraction analyses revealed that the diffraction peaks shift to higher angles when incorporating the ZnO in the P3HT:PCBM surface and this is consistent with the Raman observation. The photovoltaic properties demonstrated that the addition of ZnO nanoparticles in P3HT:PCBM bulk-heterojunction increases PCE from a baseline of ∼1.0 % in the P3HT:PCBM system to 1.7% in the P3HT:PCBM:ZnO ternary system. The enhanced PCE was due to improved absorption as compared to its counterparts. Upon increasing the addition of ZnO nanoparticles in the P3HT:PCBM matrix, the PCE decreases, due to a large phase separation between the polymer, PCBM and ZnO induced by ZnO agglomerations which resulted in increased surface roughness of the active layer. These findings signify that incorporation of ZnO nanostructures in the P3HT:PCBM polymer matrix facilitates the electron transport in the photoactive layer which results to improved efficiency.

This work studies various properties of polymer layers and hybrid layers containing inorganic nanoparticles. MEH-PPV and Polythiophene films are characterized by different experimental techniques. Dark J-V characteristics were measured at different temperatures and the mobility of holes was evaluated in a few cases. Photovoltage spectra are used for a determination of the exciton diffusion length and the SPV method is discussed. The influence of the inorganic nanoparticles CdS and ZnO incorporated into the polymer layers is studied by various experimental methods and the applications of these layers in the inorganic-organic hybrid solar cells are discussed. The inorganic nanoparticle size distributions are obtained by several experimental techniques and the results correspond with the assumptions.

In dieser Arbeit wurden mit Hilfe einer Kombination aus „metal assisted chemical etching“ (MACE) und Polystyrol-Nanopartikel-Lithographie, Säulen-strukturierte Siliziumoberflächen mit verschiedenen Säulendurchmessern und –längen, wie auch unterschiedlichen Säulenabständen, synthetisiert. Das im Anschluss durchgeführte Elektropolier-Verfahren verhalf dabei, die durch den MACE-Prozess erhöhte Oberflächendefektdichte (DSS) zu reduzieren. Dieses Verfahren wurde von in situ Photolumineszenzmessungen unterstützt. Eine im Anschluss an das Elektropolierverfahren durchgeführte Methylpassivierung erwies sich als notwendig, um den Zustand der reduzierten DSS für einen längeren Zeitraum an Luft stabil zu halten. Die elektropolierten und methylpassivierten Oberflächen wurden als Substrate in Kombination mit dem leitfähigen Polymer PEDOT:PSS für die Herstellung von Hybridsolarzellen verwendet. Im Vergleich zu Zellen deren strukturierte Oberfläche nicht zuvor elektropoliert worden ist, kam es bei den zusätzlich elektropolierten Zellen zu einer Effizienzverbesserung und einer Erhöhung des Kurzschlussstroms (JSC). Elektrochemische Verfahren zur Veränderung der Säulen-Morphologie sind in dieser Arbeit ebenfalls untersucht worden. Um eine strukturierte Oberfläche auch in anderen Bereichen, wie etwa der Biosensorik, verwenden zu können, bedarf es neben der Methylpassivierung weiterer Formen der Funktionalisierung. Im Rahmen dieser Arbeit wurde ein Syntheseweg entwickelt, der es ermöglicht direkt an das Siliziumsubstrat gebundene Hydroxylgruppen zu erhalten, ohne dass es zu einer Bildung von intermediären Oxidschichten zwischen Substrat und den Hydroxylgruppen kommt. Diese wurden anschließend mit verschiedenen Silanen umgesetzt, um organische Gruppen an die Oberfläche zu binden. Die gebundenen Silanderivate können im Folgenden weiter modifiziert werden, um die selektive Anbindung von Biomolekülen zu ermöglichen. / Within this work, the “metal assisted chemical etching” (MACE) technique was combined with shadow nanosphere lithography to fabricate nanowire structured Si surfaces with different wire lengths and diameters. Electropolishing procedures subsequent to the wire growth resulted in a reduction of the surface defect density (DSS). The electropolishing procedure was directly monitored with the help of in situ photoluminescence spectroscopy. Previous works already observed a full and air stable surface passivation of flat Si surfaces by methylation. Also in the present work, the nanowire surfaces were methylated after the electropolishing procedure to preserve the reduced DSS. To determine the impact of this method on the solar cell performance, the electropolished and methylated surfaces were combined with the conductive polymer PEDOT:PSS. It revealed that the cells with the electropolished substrates exhibit a higher efficiency and an increased short circuit current (JSC). Different electrochemical procedures to change the wire morphology after the structuring have been investigated as well. To use the Si substrates for applications such as biosensing, different passivation/functionalization techniques besides the methylation are required. In this thesis, a new functionalization procedure was developed to obtain air stable hydroxyl groups that are directly bound to the Si substrate without an intervening oxide layer. To demonstrate the possibility to use these hydroxyl groups in the same way as the hydroxyl groups present on a Si oxide layer, further modifications with different silane species, such as APTES and AMMS, were conducted. In order to generate a more selective anchor group, the bound APTES molecules were further modified by a maleimide derivative, which allow for the selective binding of thiol-containing molecules.

Thesis (Ph. D.)--University of Alabama at Birmingham, 2007. / Title from PDF t.p. (viewed Feb. 3, 2010). Additional advisors: Derrick R. Dean, Sergey B. Mirov, Sergey Vyazovkin, Mary Ellen Zvanut. Includes bibliographical references (p. 122-145).