For the past few decades, Ni-YSZ (yttria-stabilized zirconia) has been the dominate anode material of high temperature (>1000¢J) solid oxide fuel cells (SOFCs). However, the conductivity of Ni/YSZ is not enough when the operation temperature is in the intermediate rage of 500~700¢J. Instead, Ni/CGO is a good candidate as the anode material of intermediate temperature SOFCs (IT-SOFC), due to its enhanced conductivity. This work was aimed at the preparation of Ni/CGO composite anodes using the electrostatic assisted ultrasonic spray pyrolysis (EAUSP) method. By properly adjusting the deposition parameters, highly porous composite films with desired phases and microstructure rendering low electrode impedances were obtained. The results indicated that deposition temperature and the applied voltage dictated the evolution of film morphology and hence the interface impedance between the electrode and the electrolyte. Therefore, the optimum deposition parameters for the best microstructure and hence minimum interface impedance were 12 kV for the applied voltage, 6 : 4 for the Ni-CGO mole ratio, 450¢J for the deposition temperature. The microstructure thus obtained possessed a cauliflower-like structure with high porosity. The resultant interface impedance at 550¢J was 0.09 Ωcm2, lower than that obtained from the conventional anode preparation routes of dip-casting (0.14 Ωcm2) or mechanical mixing (0.12 Ωcm2).

Chemically and physically patterned surfaces can be used as templates to guide nano- and micro- scale particle assembly, but the design is often limited by an inability to sufficiently characterize how pattern features influence local particle-surface interactions on the order of thermal energy, kT. The research outlined in this dissertation describes comprehensive optical microscopy (i.e. evanescent wave, video) measurements and analyses of many-body and multi-dimensional interactions, dynamics and structure in inhomogeneous colloidal fluid systems. In particular, I demonstrate how non-intrusive observation of an ensemble of particles diffusing past each other and over a physically patterned surface topography can be used to obtain sensitive images of energy landscape features. I also link diffusing colloidal probe dynamics to energy landscape features, which is important for understanding the temporal imaging process and self-assembly kinetics. A complementary effort in this dissertation investigated the use of external AC electric fields to reversibly tune colloidal interactions to produce metastable ordered configurations. In addition, the electrical impedance spectra associated with colloidal assemblies formed between interfacial microelectrode gaps was measured and consistently modelled using representative equivalent circuits. Significant results from this dissertation include the synergistic use of the very same colloids as both imaging probes and building blocks in feedback controlled selfassembly on patterns. Cycling the AC field frequencies was found to be an effective way to anneal equilibrium colloidal configurations. Quantitative predictions of dominant transport mechanisms as a function of AC electric field amplitude and frequency were able to consistently explain the steady-state colloidal microstructures formed within electrode gaps observed using video microscopy. A functional electrical switch using gold nanoparticles was realized by reversibly forming and breaking colloidal wires between electrode gaps. Extension of the concepts developed in this dissertation suggest a general strategy to engineer the assembly of colloidal particles into ordered materials and controllable devices that provide the basis for numerous emerging technologies (e.g. photonic crystals, nanowires, reconfigurable antennas, biomimetic materials).

Diploma thesis deals with the use of organic materials in photovoltaic applications and the study of their electric and dielectric properties. The theoretical part of thesis deals issue of the use of organic polymeric materials in photovoltaics and their advantages and disadvantages. Next are the results of various studies of organic solar cells by other authors. In the practical part of the work are shown experimental results (volt-ampere characteristics and impedance spectra) of samples of organic semiconductors and their evaluation.