This work demonstrates the pretilt angle controllable photo-alignment effect in nanoparticles and azo-dye doped liquid crystal film. Followed by increasing the absorbed azo-dye, the vertical alignment induced by nanoparticles of polyhedral oligomeric silsesquioxanes (POSS) can be changed from high pretilt to low pretilt angle. Competition between the homogeneously aligned azo-dye and POSS-induced spontaneous vertical alignment domain generated the variable pretilt angle. The pretilt angle is a function of the pumping intensity and can be controlled continuously within the range of 0¢X~90¢X. With the sufficient absorption of photo excited azo-dye, The POSS induced vertical alignment can be switch to homogeneous alignment. The pretilt angle and surface energy are also examined to confirm the alignment effect. Both nanoparticles and azo-dye induced vertical and homogeneous alignment are non contact methods, and suitable for low temperature plastic process.

In this study, we used two types of materials as working electrode of DSSC, commercial TiO2 (P25) nanoparticle and ZnO nanotip. First part, we sintered TiO2 electrode in nitrogen and treat TiO2 electrode by UV light irradiation, in order to increase dye adsorption onto TiO2. Second part, we used three different buffer layers to grow ASD-ZnO nanotip as working electrode, sputtered-ZnO, sputtered-AZO and spin-coating TiO2. The hetrojuction is formed at the interface of ZnO nanotip/TiO2 buffer layers due to the different materials between ZnO and TiO2, which is beneficial for electron-hole separation. The morphology was measured by field emission scanning electron microscope (FE-SEM, Philip XL-40FEG). The sheet resistivity was measured by four-point probe. The crystallinity was examined by X-Ray diffraction (XRD, Simens D5000). Structural and spectral properties are characterized by ultraviolet-visible spectroscopy (UV-Vis) spectroscopy. The fourier transform infrared spectroscopy (FT-IR spectroscopy, BRUKER 66v/s) deals with the infrared region of absorption spectroscopy. And the Angilent B1500A is used for current-voltage (I-V) characterization of solar cells. In our results, we enhance the performance of TiO2 electrode DSSC, the open circuit voltage can reach to 0.56 V, the short circuit current density can reach to 16.65 mA/cm2, the conversion efficiency can reach to 4.6 % and the fill factor can reach to 49.2 %. On ZnO electrode, the open circuit voltage can reach to 0.57 V, the short circuit current density can reach to 4.43 mA/cm2, the conversion efficiency can reach to 1.21 % and the fill factor can reach to 47.9 %.

In this research, hills-like hierarchical structured TiO2 photoanodes for dye-sensitized solar cells (DSSCs) have been prepared. We expected these appropriately aggregated TiO2 clusters in photoanode layer could cause stronger light scattering and higher dye loading that increased efficiency of photovoltaics. For detailed light-harvesting study, different molecular weight of polyvinyl alcohol (PVA) polymers were used as binders for TiO2 nanoparticles (P-25 Degussa) aggregation. After preparing a series of TiO2 films with dissimilar morphology, the reflection of TiO2 films, absorbance of attached dye, amount of dye loading, and performance of fabricated DSSC devices were measured and investigated. An optimized device had higher dye loading and well light harvesting at the same time that induced a 23% increase of short-circuit current Jsc in DSSCs. Moreover, we found that electrolyte could penetrate or diffuse easily in this higher porous structure. We fabricated dye-sensitized solar cells with MPN-based liquid electrolyte and gel polymer electrolyte. From this structure, the short-circuit current Jsc was increased around 16% and 19% respectively compared to conventional layers with liquid electrolyte and gel polymer electrolyte devices. The increase in highly viscous system of gel polymer electrolyte is due to easier penetration by such hills-like hierarchical structure.

Azo-Dye Doped Liquid Crystal (DDLC) is a developed material which can be used to fabricate optical shutter, displays, etc. In this thesis, we presents of the transient grating on a planar aligned DDLC. The effect of various polarizations of writing and probing beams, and of temperature on the transient grating are examined. Then, we propose a model to explain the result. Through this study, we understand the factors that determine the light-induced aligning Dye effect on nematic liquid crystals.

Currently in Taiwan¡¦s textile-dying industry, sodium hypochlorite (NaOCl) is popularly used as a decolorization oxidant. In order to surely meet the effluent color regulation of 550 ADMI (American Dye Manufactures Institute), excessive dosage of sodium hyperchlorite is commonly used, which results in the increase of residual chloride and the accumulation of toxic chlorinated compound in the environment. This study probes into the characteristics of substitute oxidant for sodium hypochlorite to avoid the production of toxic products. The study includes decolorization efficiency evaluation, economical analysis and feasibility of commercial application. This study adopts ozone as an oxidant and ultraviolet light as the oxidant enhancer for the purpose of preventing the occurrence of secondary pollution products like trihalomethane from the sodium hyperchlorite application. Literature review indicates that there are several studies for reaction mechanisms of oxidation and disinfection of ozone and ultraviolet light for decolorization and the conclusions reveal much promising results. There are three topics in this study, which are: Topic 1: Feasibility study. This study focuses on whether the effluent color concentration of the treatment process meets the color effluent standard or not. A 3.5 L volume reactor was used in this section. Topic 2: Influencing factor analysis. A 14 L volume reactor was adopted for analyzing the influencing factors for decolorization and for comparing the differences in treatment efficiencies between a dye finishing plant effluent and two commercial dyestuff samples. Topic 3: Economic analysis. The analysis focuses on economic comparison between NaOCl and UV/Ozone processes for effluent decolorization. Analysis results of the investment cost, operation/maintenance expense, and investment return duration are presented in this section. A 50 L volume reactor was used to achieve the evaluation for this part. First topic of this study examined some operating parameters for treating effluent from the biological and chemical coagulation units of a dye-finishing wastewater treatment plant using the UV/Ozone technique to meet an effluent regulation of 550 ADMI values could be reduced from approximately 4,000 to 200 ADMI in an hour using the UV/Ozone technique. The results show that higher color removal efficiency could be achieved at pH values around 3 as compared with higher pH values of around 7 and 10. This might be due to the fact that the predominant ozone molecules at lower pH values are more selective to certain chromophore molecules in wastewater, despite the fact that hydroxyl radicals are predominant at higher pH values and have a stronger oxidation capability than ozone. The UV light used in this study emitted from the experimental lamp can excite oxygen and water molecules to produce ozone molecules and hydroxyl radicals that can then increase decolorization rate. The findings of this investigation reveal that the proposed UV/Ozone treatment scheme has potential for development into an environmentally friendly decolorization approach for dye finishing wastewater treatment. The second topic is to investigate the feasibility of applying UV/Ozone techniques to reduce color content caused by two commercial reactive dyes (Orange-13 and Blue-19). Bench experiments were performed using a 14-L reactor. Controlling factors including pH value, dosage of ozone, reaction time, and UV intensity were evaluated to obtain the optimal operating parameters. Results from this study show that the ozone dosage and pH value dominated the effects on the decolorization process. However, UV intensity shows relatively insignificant effects. Results also indicate that the color content could be reduced from 2,000 to 200 ADMI within a reaction time of 30 minutes with a total ozone dosage of 100 mg/L. This study shows that pH values of approximately 3 and 10 favored the decolorization of the studied Dye Blue-19 and Orange-13, respectively. This was due to the effects that molecular ozone and hydroxyl radicals had significant oxidative power at low and high pH, respectively. Moreover, molecular ozone was more selective to certain dye structures during its oxidation process. This also caused the effect that pH value played an important role on color removal. Kinetic analyses show that the decolorization reactions of Dye Orange-13 and Blue-19 followed a first-order decolorization model. Experimental results also indicate that the degree of decolorization was primarily proportional to the ozone dosage. Results from this study provide us an insight into the characteristics and mechanisms of decolorization by UV/ozone technique. Results will also aid in designing a system for field application of dye finishing plants. According to the results from the third topic, for a dye finishing plant of wastewater flow rate of 800CMD (m3/day), the capital cost of equipment and related establishment as well as amendment is about US$ 116,300, and the monthly operation and maintenance cost is US$ 4,030. In this study, ozone was used as a substitute decolorizing oxidant to treat the effluent from the secondary biological and physical/chemical treatment plant. Because the current cost for the decolorization oxidant (NaOCl) is approximately US$ 5,700 per month, the monthly saving, adopting the decolorization system using UZ/Ozone, will be US$ 1,670. The investment return period will be over 7 years and is not attractive to the plant owners. However, to prevent the accumulated toxicity of chloride compounds in the environment and to promote the desires of investment on the advanced decolorization technique, a favorable tax deduction policy needs to be applied.

This study was to prepare nanoscale MgO using the homogeneous precipitation process and to investigate its destructive adsorption with dye wastewater of reactive black-5 and reactive blue-19. In addition, UV-vis Spectrophotometer, Matrix-Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry (MALDI-TOF/MS) and Gas Chromatograph/Mass Spectrometer (GC/MS) were used to analyze the intermediates resulting from destructive adsorption. Based on the results obtained, the destructive adsorption mechanisms for the treatment of dye wasterwater by nanoscale MgO were proposed in this study. In this work, the optimal operating conditions for nanoscale MgO synthesis were determined to be the following: (1) a chemical reaction time of 7 hr, (2) reaction temperature of 125¢J, (3) molar ratio of 9 for urea/MgCl2¡D6H2O, (4) water addition of 250 mL, (5) mixing intensity of 90 strokes per min, (6) calcination at 450¢J for 4 hr, (7) reflux time of 24 hr, (8) freeze-drying method, (9) two stage calcinations. Using these operating conditions one is able to prepare 2-D nanoscale MgO of hexagonal platelets with a thickness of 20-30 nm and BET surface area of 120-125 m2/g. The adsorption model of nanoscale MgO for RB-5 and RB-19 was fitted to the Langmuir equation and their adsorption capacity were 196.08 mg/g and 163.93 mg/g, respectively. Both of them were fitted to the pseudo-second-order kinetic model equation. The optimal operating conditions of nanoscale MgO for destructive adsorption of both dyes were determined to be the following: (1) an initial dye concentration of 1000 mg/L, (2) a nanoscale MgO dose of 15 g/L, (3) a vigorous mixing of 30 min, (4) no need of system pH adjustment. Under such conditions, chemical oxygen demand (COD) and American Dye Manufacturers Institute (ADMI) of RB-5 and RB-19 were lower than the textile effluent standards. According to the UV-vis spectrophotometer scanning results, the color removal of nanoscale MgO for RB-5 and RB-19 was good. At the same time, the absorbance of their second maximal peaks was decreased and some peaks were observed. Therefore, it proved that the model dyes were destroyed. Experimental results have shown that nanoscale MgO has a better performance of destructive adsorption on RB-5 than that of RB-19. This might be ascribed to the following reasons: (1) a greater molecular weight, (2) a longer molecule structure, (3) more sulfate ethyl sulfone groups for RB-5, and (4) a hard to be destroyed structure of anthraquinone for RB-19. The destructive adsorption of dye wastewater by nanoscale MgO presumably took place mainly on the surface active sites of nanoscale MgO, including anion/cation vacancies, superoxide anion, edge, corner, isolated OH, lattice bound OH and assiocited-OH groups. According to the results of MALDI-TOF/MS and GC/MS analysis, the relevant reaction mechanism for RB-5 could be divided into three stages: (1) adsorption and water-soluble groups exfoliation stage, (2) chromophor decomposition and decolorization stage, and (3) further degradation stage for light-color intermediates. On the other hand, the relevant reaction mechanism for RB-19 might involve only the adsorption and auxochrome exfoliation stage and chromophor decomposition and decolorization stage.

The thesis discusses how to utilize Sol-gel method to prepare nano-sized TiO2 films of photoelectrodes and the their use in Dye-Sensitized Solar Cells. The main goal is the study on the production of TiO2 photoelectrodes. When making nano-sized TiO2 films of photoelectrodes, we have to first produce TiO2 sol via the Sol-gel method optical thin films are then made by spin coating. After its spin coating, we study the crystalline phase and morphology of nano-sized TiO2 films of photoelectrodes in terms of two ways: Supercritical drying and oven drying. Among the Dye-Sensitized Solar Cells that are made with different drying methods, owing to higher porosity and surface area, the nano-sized TiO2 films of photoelectrodes made by supercritical drying adsorb more dye molecules and are thus more efficient.

In this study, a high power Q-switch pulse laser has been used as the writing beams. The laser-induced holographic gratings in the DR1-doped liquid crystal samples and the DR1-PMMA polymer thin films were investigated by changing the temperature of samples and the angles of two writing beams. The He-Ne cw laser has been used as a real-time probe beam to detect the first order diffraction signals. Without external field, the gratings are the results of concentrations and diffusions of azo dye isomers. The diffusion model has been utilized to analyze the first order diffraction signals in order to understand the mechanics of gratings and the effect of temperature and angle.

In this study, we deposit titanium dioxide (TiO2) on the indium tin oxide (ITO/glass) substrate by a liquid phase deposition (LPD) method as a buffer layer and coat TiO¬2 particles on LPD-TiO2 films by spin-coating method as anode of dye-sensitize solar cell (DSSC). In order to adjust the optical absorption edge of titanium dioxide to the visible light, we co-dope fluorine and nitrogen into TiO2 by LPD method and Ammonium Fluoride (NH4F). In our experiment, the morphology and thickness was characterized by scanning electron microscopy (SEM), structure was characterized by X-ray diffraction (XRD), chemical properties was characterized by electron spectroscope chemical analysis (ESCA), structural and spectral properties were characterized by ultraviolet-visible spectroscopy (UV-Vis) spectroscopy and current-voltage (I-V) characterization of solar cells was measured by B1500A. In our results, we enhance the performance of TiO2 as a DSSC`s anode, the open circuit voltage can reach to 0.71 V, the short circuit current can reach to 5.14 mA, the conversion efficiency can reach to 1.91 % and the fill factor can reach to 52.5 %.

<p>This thesis is divided into four parts with organic chromophores for dye sensitized solar cells as the common feature and an introduction with general concepts of the dye sensitized solar cells.</p><p>The first part of the thesis describes the development of an efficient organic chromophore for dye sensitized solar cells. The chromophore consists of a triphenylamine moiety as an electron donor, a conjugated linker with a thiophene moiety and cyanoacrylic acid as an electron acceptor and anchoring group. During this work a strategy to obtain an efficient sensitizer was developed. Alternating the donor, linker or acceptor moieties independently, would give us the tool to tune the HOMO and LUMO energy levels of the chromophores. The following parts of this thesis regard this development strategy.</p><p>The second part describes the contributions to the HOMO and LUMO energy levels when alternating the linker moiety. By varying the linker the HOMO and LUMO energy levels was indeed shifted. Unexpected effects of the solar cell performances when increasing the linker length were revealed, however.</p><p>The third part describes the investigation of an alternative acceptor group, rhodanine-3-acetic acid, in combination with different linker lengths. The HOMO and LUMO energy level tuning was once again successfully shifted. The poor electronic coupling of the acceptor group to the semiconductor surface proved to be a problem for the overall efficiency of the solar cell, however.</p><p>The fourth part describes the contributions from different donor groups to the HOMO and LUMO energy levels and has so far been the most successful in terms of reaching high efficiencies in the solar cell. A top overall efficiency of 7.1 % was achieved.</p>