Indium tin oxide (ITO) films were deposited onto the glass substrate by rf reactive magnetron sputtering method. Deposition was performed by changing processing conditions, such as rf power, process pressure and substrate temperature. The structural, optical and electrical properties of ITO films have been characterized by X-ray diffraction, optical transmittance and sheet resistance. In the process of ITO deposition, we change rf power and fix process pressure at room temperature. And we change process pressure after finding low sheet resistance by changing rf power at room temperature. The low sheet resistance of 35 £[/¡¼ was obtained at room temperature. In addition, we change the substrate temperature while keeping the same rf power and process pressure. When the temperature is 400¢J, the sheet resistance as low as 6.98 £[/¡¼ was obtained. The diffraction peaks on (211), (222), (400), and (440) directions were observed by XRD analysis. Under high temperature (300¢J) deposition the transmittance and diffraction peaks of the films were found to change with different rf power and process pressure. However, the sheet resistances are about the same during the interest for both rf power and process pressure. The UV-visible spectra indicate that the optical transmittance of all the films is between 65 % ~ 90 % at visible range.

This dissertation has focused on the study of the ITO/organic heterojunction and the chemistries therein, it proposes appropriate strategies that enhance the interfacial physical and electronic properties for charge injection with application to organic thin-layer devices. We focused on four major aspects of this work: i) To characterize the ITO surface and chemistries that may be pertinent to interaction with adjacent organic layers in a device configuration. This developed a working model of surface and provided a foundation for modification strategies. Characterization of the electronic properties of the surface indicate less than 5% of the geometrical surface is responsible for the bulk of current flow while the rest is electrically inactive. ii) To determine the extent to which these chemistries are variable and propose circumstances where compositional changes can occur. It is shown that the surface chemistry of ITO is heterogeneous and possible very dynamic with respect to the surrounding environment. iii) To propose a strategy for modification of the interface. Modification of ITO surfaces by small molecules containing carboxylic acid functionalities is investigated. Enhancements in the electron transfer rate coefficient were realized after modification of the ITO electrode. The enhancements are found to stem from a light etching mechanism. Additionally, an elecro-catalytic effect was observed with some of the modifiers. iv) Apply these modifications to organic light emitting diodes (OLEDs) and organic photovoltaic devices (OPVs). Enhancements seen in solution electrochemical experiments are indicative of the enhancements seen for solid state devices. Modifications resulted in substantially lower leakage currents (3 orders of magnitude in some cases) as well as nearly doubling the efficiency.An additional chapter describes the creation and characterization of electrochemically grown polymer nano-structures based on blazed angle diffraction gratings. The discussion details the micro-contact printing process and the electro-catalytic growth of the conductive polymers PANI and PEDOT to form diffraction grating structures in their own right. The resulting diffraction efficiency of these structures is shown to be sensitive to environmental conditions outlining possible uses as chemical sensors. This is demonstrated by utilizing these structures as working pH and potentiometric sensors based on the changing diffraction efficiency.

Indium-tin oxide (ITO) is commonly used as the transparent electrode in organic photovoltaic (OPV) devices. ITO's transparent properties come at the expense of less than ideal electrode characteristics arising from insulating over-oxidized surface species. OPVs fabricated on the native ITO surface tend to exhibit poor performance with a high degree of variability from device to device. Aggressive acid etching of the ITO surface removes the majority of the insulating surface species leading to improvements in OPV efficiency with greater reproducibility and increased device to device consistency.Organic light emitting diodes (OLEDs) are planar electroluminescent light sources that naturally couple a portion of their emission into internally reflected modes within the device substrate. Although this coupling property is well known, few attempts have been made to integrate OLEDs as light sources for internal reflection elements. Furthermore, OPVs share the optical coupling properties of OLEDs and therefore can be used as integrated internal reflection detectors. Integrating both an OLED light source and an OPV detector onto the same substrate results in an internal reflection sensing platform that requires no free-space optics, has low power consumption requirements, and can be easily fabricated on substrates occupying an area less than one square inch. In this work we establish a functional prototype design, characterize the fundamental coupling properties, and demonstrate several surface sensing responses of this fully integrated optical sensing platform.The net solar power production from OPVs arises from the interactions between multiple currents through the device. The photocurrent is the only power producing current in the device and understanding the voltage dependent nature of this current is essential in OPV research. Analysis methods of conventional, inorganic photovoltaics do not adequately describe the photocurrent behavior commonly observed in OPVs. OPV analysis is therefore somewhat limited by the methods commonly employed. To improve upon the convention methods we develop a simplified method of OPV photocurrent analysis based on electrochemical methods that accurately describes the voltage dependence of the photocurrent and leads to greater insight into the key parameters involved in solar power production from OPVs.

We have built an imaging mass spectrometer adapted for ultrashort laser pulses as its ionization technique, as an alternative to other imaging techniques. Before my arrival, the mass spectrometer has only been subject to preliminary tests on noble gases. Since then, we’ve made some modifications to the system in order to properly analyze solids. This thesis shows how we obtain our ultrashort laser pulses, the inner workings of our homemade imaging mass spectrometer, and the results that we’ve obtained with it so far. We tested two modes of operation concerning the extraction of the ions from the system into the mass analyzer: continuous and pulsed. We discuss the advantages and disadvantages of each configuration. We also display preliminary imaging results with our imaging technique of a simple WO3 and ITO structure. We conclude by comparing the resolution of this image to the different techniques in imaging mass spectrometry, how we can further improve our mass spectrometer, and the future use of this machine. Nous avons construit un spectromètre de masse adapté pour les pulses de laser très courts comme technique d’ionisation, pour acquisition des images d’un échantillon. Avant je suis arrivé, le spectromètre de masse avait seulement été utilisé pour des tests préliminaires de gaz nobles. Depuis ce moment, nous avons modifié le système pour analyser les solides. Cette thèse démontre comment on obtient nos pulses de laser très courts, comment notre spectromètre fait maison fonctionne et les résultats nous avons obtenus jusqu’à présent. Nous avons testé deux configurations différentes au sujet de l’extraction des ions du système : constant et pulsé. Nous discutons aussi les avantages et désavantages de chaque mode d’opération. Nous démontrons aussi des images préliminaires d’un substrat mixte de WO3 et ITO. Nous concluons par comparer la résolution des images aux autres techniques de collection d’images, comment nous pouvons améliorer notre spectromètre de masse et les plans pour la machine dans le futur.

Indium tin oxide (ITO) is the most widely used transparent electrode in flexible solar cells because of its high transparency and conductivity. But still, cracking of ITO on PET substrates due to tensile loading is not fully understood and it affects the functionality of the solar cell tremendously as ITO loses its conductivity. Here, we investigate the cracking evolution in ITO/PET exposed to two categories of tests. Monotonous tensile testing is done in order to trace the crack propagation in ITO coating as well as determining a loading range to focus on during our study. Five cycles test is also conducted to check the crack closure effect on the resistance variation of ITO. Analytical model for the damage in ITO layer is implemented using the homogenization concept as in laminated composites for transverse cracking. The homogenization technique is done twice on COMSOL to determine the mechanical and electrical degradation of ITO due to applied loading. Finally, this damage evolution is used for a simulation to predict the degradation of ITO as function in the applied load and correlate this degradation with the resistance variation. Experimental results showed that during unloading, crack closure results in recovery of conductivity and decrease in the overall resistance of the cracked ITO. Also, statistics about the crack spacing showed that the cracking pattern is not perfectly periodical however it has a positively skewed distribution. The higher the applied load, the less the discrepancy in the crack spacing data. It was found that the cracking mechanism of ITO starts with transverse cracking with local delamination at the crack tip unlike the mechanism proposed in the literature of having only cracking pattern without any local delamination. This is the actual mechanism that leads to the high increase in ITO resistance. The analytical code simulates the damage evolution in the ITO layer as function in the applied strain. This will be extended further to correlate the damage to the resistance variation in following studies.

Indium tin oxide is a transparent conductive oxide electrode which is widely used for organic electronics. Morphology of ITO plays an important role in the performance of organic electronics. To understand the influence of the substrate morphology in device performance, a controllable route for producing periodic and aperiodic roughness of ITO surfaces are necessary. In this thesis, this was attempted by using various approaches to forming ITO nanostructures. Initially, ITO was deposited by a traditional sputtering procedure. However, the roughness distribution of the sputtered ITO resulted in a s Gaussian distribution, unsuitable to further studies of roughness. ITO nanostructures can also be formed by depositing ITO nanoparticles on an ITO sub- strates. Using acetate and chloride precursors, ITO films were produced from solution and formed into nanoparticles using the reverse micelles deposition approach. The acetate route (InAc+SnCl2+ethanol), was the most successful prior to the nanoparticle formation, showing high quality ITO with bixbyte crystal structure and Sn percentages of 20%, low enough to form a conductive film. Nanoparticles were fabricated with diblock copolymer reverse micelles(PS-b-P2VP). Reverse micelles were found to act as a nano reactor, restricting the size of nanoparticles by having hydrophilic reactants undergo chemical reactions inside the micelles. However, nanoparticles from the reverse micelles revealed Sn percentages much above 20%. This was attributed to the solubility difference of the precursors leading to displacing or preventing of pre- cursor loading into the reverse micelles. The change of the stirring time, the micelles concentration, the sequence of precursors loading, and the weight of precursors were not found to affect the Sn concentration; moreover, large variations in Sn concentrations were observed. From quantitative nano mechanical testing of the micelles, a maximum load amount for the precursors was observed, confirming that the high concentration of Sn was likely due to the solubility differences between the precursors and their ability to penetrate the micelle. By manipulating the nanoparticles distribution through spin coating speeds, micelles concentration, and deposited volume, several degrees of order were obtained, though hexagonal packing was not observed. In general, even though Sn concentration were found to be above 20%, nanoparticles were successfully fabricated with reverse micelles, confirming that the reverse micelle technique is a good strategy for future studies of roughness. / Thesis / Master of Applied Science (MASc)

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Understanding interfacial charge injection processes is one of the key factors needed for development of efficient organic electronic devices, such as biosensors and energy conversion systems, since these processes control the electrical characteristics of these devices. Spectroelectrochemical characterization of electron transfer processes occurring at the electrode - electroactive thin film interface has been evaluated to improve our understanding of charge transfer kinetics using a novel form of electroreflectance spectroscopy, potential-modulated attenuated total reflectance (PM-ATR), which makes it possible to sensitively monitor spectroscopic changes in thin films as a function of applied potential.PM-ATR was used to evaluate three different redox-active films deposited on indium tin oxide (ITO) electrodes to investigate: i) the orientation dependence of charge transfer rates of thin films of biomolecules, ii) surface treatment and modification effects on charge transfer kinetics of conducting polymers and, iii) estimation of rates of electron injection and conduction band edge of semiconductor nanocrystalline materials.First, Prussian blue film as a model system was used successfully to examine the PM-ATR technique for determination of the charge transfer rate constant between ITO and a molecular film.Second, an anisotropic and redox active protein film, cytochrome c, was used to probe charge transfer rates with respect to molecular orientation. The electron transfer rate measured using TM polarized light was four-fold greater than that measured using TE polarized light. These data are the first to correlate a distribution of molecular orientations with a distribution of electron transfer rates in a redox-active molecular film.Third, the effects of ITO surface treatment and modification on charge transfer kinetics on a conducting polymer, poly(3,4-ethylenedioxythiophene/)/poly(styrenesulfonate) (PEDOT/PSS), were studied. The apparent interfacial charge transfer rate constant for PEDOT/PSS on ITO has been reported for the first time which cannot be measured otherwise with conventional electrochemistry due to high non-Faradaic background of PEDOT/PSS films.Fourth, PM-ATR enabled characterization of reversible redox processes between submonolayer coverages of surface-tethered, CdSe nanocrystals and ITO for the first time. Optically determined onset potentials for electron injection were used for estimation for the conduction band and valance band energies (ECB and EVB, respectively).

The purpose of the thesis is to investigate the improvement of single-crystal Si solar cell efficiency using porous Indium tin oxide (ITO)/ITO double layer antireflection(AR) coating. The resistivity, transmittance and refraction index of the porous ITO films prepared by supercritical CO2 treatment were investigated. At a 2000 psi pressure and 60¡CC, the resistivity of porous ITO films is 15 £[-cm, the average transmittance is better than 95 %, and the refraction index is 1.54. In addition, the resistivity of ITO thin films fabricated by reactive ratio-frequency magnetron sputtering is 7¡Ñ10-4 £[-cm, the average transmittance are 85 %, and the refraction index is 2.0. For the single crystal-Si solar cell with porous ITO/ITO double layer AR coating, the open circuit voltage, short circuit current, fill factor and efficiency are measured.

In this studing, application of the digital image correlation method (DIC) for determining the coefficient of thermal expansion (CTE) of Indium Tin Oxide/Polyethylene Terephthalate(ITO/PET) thin film/flexible substrate was proposed and the effects of thinkness variations of ITO and PET, respectively, on the CTE of the specimens was disscussed. The observation range of experimental temperature was chosen from room temperature to the glass transfer temperature of PET, 70¢J. A novel DIC experimental process for reducing the errors caused from the variations of the refractive index of the surrounding heated air was proposed. As a result, the experimental error of CTE measurement was reduced form 10~17% to less than 5%. The experimental results showed that the CTE of ITO/PET specimen is anisotropic. Futhermore, the CTE of an ITO/PET specimen will be increased by decreasing the thinkness of PET flexible substrate, and increased by increasing the thinkness of ITO film - which means decreasing the surface resistance of ITO film.