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This dissertation focuses on the design, synthesis, characterization of platinum (II) pyridylazolate complexes and develop high performance organic light emitting diodes (OLEDs) and design and execute high-sensitivity humidity sensors based on the luminescent metal-organic complexes of platinum. A majority of existing platinum compounds do not dissolve in organic solvents, making it difficult to analyze the photophysical characteristics of complexes in solution, a key part of understanding chemical photophysical properties. Furthermore, due to the poor quantum yield, it is inefficient for use in devices such as OLEDs. Chapter 2 reports the synthesis and characterization of a novel heteroleptic platinum(II) pyridylazolate complex with high solubility and quantum yield. The photochemistry of the complex is studied, including efficiency, emission profiles, and lifetimes at different temperatures. Chapter 3 reports the power efficiency (lm/W), current efficiency (cd/A), external quantum efficiency (EQE), luminance and operating voltage (V) of OLED devices made with the heteroleptic platinum(II) pyridylazolate complex. The relation between thickness of hole transport layer and electron transport layer on performance of devices has been studied through building a variety of devices. Chapter 4 includes application of a homoleptic platinum(II) pyridylazolate complex in humidity sensor. In many environments, the relationship between moisture content and emissive wavelength has been investigated. This research reveals that regardless of the humidity level, there is a link between increasing the temperature and decreasing the moisture absorption capacity of the complex.

An experiment was conducted to evaluate the potential of producing dwarf tomatoes (Solanum lycopersicum L.) in an indoor vertical system. Cultivars 'Micro Tom', 'Jochalos', and 'Venus' were grown under the three daily light integral (DLI) levels of 16.9, 22.7, and 27.9 mol·m-2·day-1. Cultivar had an effect on height, with Jochalos being the tallest. Plants grown under 27.9 mol·m-2·day-1 were the shortest. The time of first flower was affected by cultivar, appearing earliest in Micro Tom. Regarding DLI, the first flower was earliest in plants under 22.7 and 27.9 mol·m-2·day-1. The time of first harvest was only affected by cultivar, in which Micro Tom was earliest. There was an interaction effect for the total and marketable fruit count harvested. Micro Tom had the highest overall number of fruits harvested amongst cultivars, and Micro Tom grown under 22.7 and 27.9 mol·m-2·day-1 had more total and marketable fruit counts than those grown under 16.9 mol·m-2·day-1. There was no interaction effect for fruit weight harvested. The effect of cultivar differed between the total and marketable fruit weights harvested, but Jochalos produced the highest weights in both. The effect of DLI was the same for total and marketable fruit weights harvested, with plants under 22.7 and 27.9 mol·m-2·day-1 having the highest weights. Cultivar had an effect on fruit Brix, with Micro Tom fruit having the lowest Brix and Jochalos fruit having the highest Brix. The effect of DLI resulted in fruits produced by plants under 27.9 mol·m-2·day-1 having the highest Brix and fruits produced by plants under 16.9 mol·m-2·day-1 having the lowest. Based on these results, there is potential for dwarf tomatoes to be grown in vertical farm systems. / Master of Science in Life Sciences / An experiment was conducted to evaluate the potential of producing dwarf tomatoes (Solanum lycopersicum L.) in an indoor vertical system. Cultivars 'Micro Tom', 'Jochalos', and 'Venus' were grown under the three daily light integral (DLI) levels of 16.9, 22.7, and 27.9 mol·m-2·day-1. Cultivar had an effect on height, with Jochalos being the tallest. For DLI, all plants grown under 27.9 mol·m-2·day-1 were the shortest. The time of first flower was affected by cultivar, appearing earliest in Micro Tom. Regarding DLI, the first flower was earliest in plants under the higher DLIs. The time of first harvest was only affected by cultivar, in which Micro Tom was earliest. There was an interaction effect for the total and marketable fruit count harvested. Micro Tom had the highest overall number of fruits harvested under the highest DLIs. There was no interaction effect for fruit weight harvested. In cultivars, Jochalos produced the highest weights for both total and marketable fruits. Plants under 22.7 and 27.9 mol·m-2·day-1 had the highest weights for total and marketable fruits harvested. Cultivar had an effect on fruit Brix, with Micro Tom fruit having the lowest Brix and Jochalos fruit having the highest. Uninfluenced by cultivar, fruits produced by plants under 27.9 mol·m-2·day-1 had the highest Brix, while those under 16.9 mol·m-2·day-1 had the lowest. Based on these results, there is potential for dwarf tomatoes to be grown in vertical farm systems.

In this research, we investigated a novel rigid-rod polymer sPBI for mono-layer polymer light emitting diode (PLED) fabrication and luminescence emission. sPBI could be a luminescent polymer with a low threshold voltage of 4.5 V and green light electroluminescence emission (530 nm). Its SO3H pendant attached to the p-phenyl ring improved electronic delocalization along the backbone resulted in a red shift of the absorption spectrum. By attaching propanesulfonated pendants to the heterocyclic moiety of intractable fully conjugated sPBI, water-soluble rigid-rod polyelectrolyte sPBI-PS(Li+) was synthesized to promote its processibility in water or common organic solvent. This water-soluble rigid-rod polyelectrolyte sPBI-PS(Li+) was fabricated for polymer light-emitting electrochemical cells (PLECs) with LiCF3SO3 (LiTf) or LiN(CF3SO2)2 (LiTfSI) dopants for investigating the influence of propanesulfonated pendants as well as dopants on the opto-electronic emission and the room-temperature DC conductivity. The effect of lithium salts (LiTf or LiTfSI) on photoluminescence color of doped sPBI-PS(Li+) films was negligible. sPBI-PS(Li+) PLECs doped with 0.41 and 1.01 wt. % of LiTfSI showed higher green light electroluminescence emission (514 nm) with a lower threshold voltage of 3.0 V and -4.6 V, respectively. Emission brightness of the sPBI-PS(Li+) PLEC did not raise upon increasing the ionic conductivity of the luminescent layer.

GaN-based light emitting diodes (LEDs) face several challenges if the technology is to make a significant impact on the solid state lighting market. The two most pressing of these challenges are cost and efficiency. The development of alternative substrate technologies shows promise toward addressing both of these challenges, as both GaN-based device technology and the associated metalorganic chemical vapor deposition (MOCVD) technology are already relatively mature. Zinc oxide (ZnO) and silicon (Si) are among the most promising alternative substrates for GaN epitaxy. This work focuses on the development of MOCVD growth processes to yield high quality GaN-based materials and devices on ZnO and Si. ZnO, because of its similar lattice constant and thermal expansion coefficient, is a promising substrate for growth of low defect-density GaN. The major hurdles for GaN growth on ZnO are the instability of ZnO in a hydrogen atmosphere and out-diffusion of zinc and oxygen from the substrate. A process was developed for the MOCVD growth of wurtzite GaN and InxGa1-xN on ZnO, and the structural and optical properties of these films were studied. High zinc and oxygen concentrations remained an issue, however, and the diffusion of zinc and oxygen into the subsequent GaN layer was studied more closely. Silicon is the most promising material for the development of an inexpensive, large-area substrate technology. The challenge in GaN growth on Si is the tensile strain induced by the lattice and thermal mismatch between GaN and Si. A thin atomic layer deposition (ALD)-grown Al2O3 interlayer was employed to relieve strain while also simplifying the growth process. While some strain was still observed, the oxide interlayer leads to an improvement in thin film quality and a reduction in both crack density and screw dislocation density in the GaN films. A comparison of GaN-based LEDs grown on sapphire and Al2O3/Si shows similar performance characteristics for both devices. IQE of the devices on silicon is ~32%, compared to ~37% on sapphire. These results show great promise toward an inexpensive, large-area, silicon-based substrate technology for MOCVD growth of GaN-based optoelectronic devices.

This thesis focuses mainly on the techniques to achieve high-performance top-emitting OLEDs, regarding device efficiency and lifetime for both non-inverted and inverted structures. It is thus organized as follows: In Chapter 2, the basic physics of organic semiconductor materials are reviewed, including the electronic properties of organic semiconductor materials, molecular excitations and their electronic transitions etc., which are believed to be critical for understanding of the work. Then, the general device physics of OLEDs are reviewed in detail, which includes almost every important electrical and optical process involved in the device. Finally, techniques and methods used to improve the device performance are summarized, which includes electrical doping of charge carrier transport layers. In Chapter 3, all organic materials, experimental techniques, and characterization methods used in this study are briefly described. In the following Chapter 4, techniques that are used for device optimization of non-inverted top-emitting OLEDs are discussed. Also, the mechanism of light outcoupling enhancement by a capping layer is discussed there. In the last part of Chapter 4, the influence of the optical device structure on the intrinsic quantum yield of the emitters is studied. Chapter 5 is focused on inverted top-emitting OLEDs, which are believed to be better applicable with current mainstream n-type amorphous silicon thin film transistor (TFT) technology. In this Chapter, the organic/metal and metal/organic interfaces are investigated in detail and their influence on device performance is discussed. In Chapter 6, the degradation of top-emitting OLEDs is studied, with a focus on the influence of electrode material and electrode thickness on the lifetime of top-emitting devices.

The electronics industry today is one that stands as a multi-billion dollar industry that is increasingly incorporating more and more products that have ever escalating applications in our everyday life. One of the main sectors of this industry, and one that is likely to continue expanding for a considerable number of years are flat-panel displays. Traditionally, the displays market has been dominated by cathode ray tube (CRT) and liquid crystal displays (LCDs) display types. The drawback of such display displays is that they can be bulky, heavy and/or expensive and so there is considerable room for an alternative and superior technology. One possibility is organic semiconductor displays where light-emitting molecules can be dissolved in common solvents before being inkjet printed, spin-coated or even painted onto any surface giving the benefits of simple and cost effective processing. Organic light-emitting diodes (OLEDs) have recently become ever more evident as a major display type. This thesis focuses on the advancement of light-emitting dendrimers towards flat-panel display applications. The particular interest in dendrimers arises because it has been found they are capable of giving solution-processed phosphorescent devices with high efficiency. Throughout the thesis the benefits of the dendrimer concept are repeatedly shown revealing why this could become the ideal organic material for display applications. The thesis introduces various techniques of electroluminescence and photoluminescence measurements before applying such methods to study a large number of light-emitting dendrimers in order to explore the role of intermolecular interactions, how they are related to molecular structure, and how this determines photophysical and charge transporting properties of the dendrimers. By such studies a number of highly efficient solution-processed phosphorescent light-emitting dendrimers have been identified while the efficiency of devices made from these dendrimers has been improved. This has been demonstrated in each of the three primary display colours of red, green and blue. The work detailed thus brings closer the prospect of dendrimer light-emitting diodes being the future flat-panel display type of choice.

Made available in DSpace on 2014-06-11T19:32:44Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-02-03Bitstream added on 2014-06-13T21:04:40Z : No. of bitstreams: 1 bacagarcia_cj_dr_botfca.pdf: 1838802 bytes, checksum: 409b0975f60ea98eae46f5f5e9811d18 (MD5) / Com o desenvolvimento da tecnologia dos plásticos, tornou-se possível à construção de tubos emissores, com padrão de qualidade, a custos relativamente baixos. O emprego da irrigação localizada, pelo sistema de gotejamento, ganhou no Brasil novo impulso a partir dos anos 90, com a instalação de diversas empresas internacionais especializadas neste mercado. As empresas mais importantes do mundo se fazem presente no Brasil e algumas multinacionais estão produzindo aqui parte de sua linha de produção, como: Netafim, Plastro, Amanco, NaanDan e como empresa brasileira fabricante, existe a Petroisa. Esse trabalho teve por objetivo caracterizar e avaliar de forma técnica e hidráulica alguns tubos emissores para gotejamento, comercializados no mercado brasileiro de acordo com as normas ISO 8796:2004 e ISO 9261:2004. O experimento foi conduzido no Laboratório de Irrigação do Departamento de Engenharia Rural, da Faculdade de Ciências Agronômicas, Universidade Estadual Paulista Julio de Mesquita Filho - Campus de Botucatu, São Paulo. A norma ISO 9261:2004 prescreve critérios para avaliar e especificar gotejadores com vazão inferior a 24 L h-1 e tem por característica principal, a flexibilidade para adaptar economicamente qualquer laboratório de irrigação, porque não especifica as características da bancada de ensaios. 2 Os ensaios visaram à determinação dos seguintes parâmetros: Coeficiente de variação de fabricação, equação característica da relação entre pressão e vazão, espessura da parede, diâmetro interno, espaçamento entre emissores, resistência à pressão hidráulica à temperatura ambiente e à temperatura de 40oC, resistência à tensão de 160 N e 180 N, e ensaio de envelhecimento precoce. As análises mostraram um coeficiente de variação de fabricação (CVf) inferior a 0,07 para todos os tubos emissores... . / With the domain of the technology of plastics, it became possible to manufacture quality emitting pipes standard, at relatively low costs. Trickle irrigation method, using emitting pipes, gained in impulse Brazil during last decade 90, with the installation of several specialized international industries. Multinationals industries such as Netafim, Plastro, Amanco, NaanDan and a Brazilian manufacturer, Petroisa are producing here part of its line of production. This work had the objective, to characterize and evaluate emitting pipes, commercialized in Brazil according to ISO 8796 and ISO 9261:2004 standards. The 4 tests were conducted in the Laboratory of Irrigation of the Faculdade de Ciências Agronômicas - Campus of Botucatu, São Paulo, Brazil. The following parameters were evaluated: manufacturing variation, pressure and discharge equation, thickness of the wall, internal diameter, emitters spacing, resistance to the hydraulic pressure at the current temperature and at raised temperature (40oC), resistance to the 160 tension and 180 N, and precocious aging. The analyses had shown manufacturing coefficients of variation below 0,07 for all the emitting pipes, (maximum value allowed by ISO 9261:2004) standard. The exponents of pressure (x), in the pressure discharge e friction were of 0.431, 0.502, 0.450, 0.575, 0.533, 0.480, 0.470 for Petro Drip, Golden Drip, Chapin, Queen Gil, Aqua Traxx, Tiran and Amanco Drip, emitters respectively, classifying them as not compensating. For ISO 9261:2004, the value of x should not exceed 0.2 to be classified as compensating. The evaluated emitters (Ram, Naan PC, Amanco Drip PC and Twin Plus) had values lesser than 0,075. The test of resistance to the tension, as ISO 9261:2004 is a useful tool to classify an emitting in reusable and not reusable pipe. Aqua Traxx emitter was classified as not reusable. It presented probably... (Complete abstract, click electronic address below).

abstract: White organic light emitting diodes (WOLEDs) are currently being developed as the next generation of solid state lighting sources. Although, there has been considerable improvements in device efficiency from the early days up until now, there are still major drawbacks for the implementation of WOLEDs to commercial markets. These drawbacks include short lifetimes associated with highly efficient and easier to fabricate device structures. Platinum (II) complexes are been explored as emitters for single emissive layer WOLEDs, due to their higher efficiencies and stability in device configurations. These properties have been attributed to their square planar nature. Tetradentate platinum (II) complexes in particular have been shown to be more rigid and thus more stable than their other multidentate counterparts. This thesis aims to explore the different pathways via molecular design of tetradentate platinum II complexes and in particular the percipient engineering of a highly efficient and stable device structure. Previous works have been able to obtain either highly efficient devices or stable devices in different device configurations. In this work, we demonstrate a device structure employing Pt2O2 as the emitter using mCBP as a host with EQE of above 20% and lifetime values (LT80) exceeding 6000hours at practical luminance of 100cd/m2. These results open up the pathway towards the commercialization of white organic light emitting diodes as a solid state lighting source. / Dissertation/Thesis / Masters Thesis Materials Science and Engineering 2016

Optofluidics is a new branch within photonics which attempts to unify concepts from optics and microfluidics. Unification of photonics and microfluidics enable us to carry out analysis of fluids through highly sensitive optical sensing device. These optical sensing devices are contained within a microchip, wherein light is made to pass through analyte (fluids of few nanoliters). The interaction between light and fluid gives rise to highly sensitive diagnostic systems. In this work the fabrication and performance characterization of a fluorescent green OLED for optofluidic applications is presented. The effect of thickness variation of hole injection (CuPc) and hole blocking (BCP) layers on the performance of fluorescent green organic light emitting diodes (OLEDs) have been studied. Even though these two organic layers have opposite functions, yet there is a particular combination of their thicknesses when they function in conjunction and luminous efficiency and power efficiency are maximized. The optimum thickness of CuPc layer, used as hole injection layer and BCP used as hole blocking layer were found to be 18 nm and 10 nm respectively. It is with this delicate adjustment of thicknesses, charge balancing was achieved and luminous efficiency and power efficiency were optimized. Such OLEDs with higher luminance can be monolithically integrated with other optical and fluidic components on a common substrate and can function as monolithically integrated internal source of light in optofluidic sensors. In this work the analysis of a fully integrated optofluidic lab-on-a-chip sensor for refractive index and absorbance based sensing using fluorescent green organic light emitting diode (OLED) as a light source is also presented. This device consists of collinear input and output waveguides which are separated by a microfluidic channel. When light is passed through the analyte contained in the fluidic gap an optical power loss due to absorption of light takes place. Apart from absorption a mode-mismatch between collinear input and output waveguide also occurs. The degree of mode-mismatch, quantum of optical power loss due to absorption of light by the fluid forms the basis of our analysis. Detection of minutest change in refractive index and changes in concentration of species contained in the analyte is indicative of sensitivity. Various parameters which influence the sensitivity of the sensor are mode spot size, refractive index of the fluid, molar concentration of the species contained in the analyte, width of the fluidic gap, waveguide geometry. By correlating various parameters, an optimal fluidic gap distance corresponding to a particular mode spot size to achieve the best sensitivity for refractive index based sensing and absorbance based sensing have been determined.