The global lighting source energy consumption accounts for about 22% of the total electricity generated. New high-efficiency solid-state light sources are needed to reduce the ever increasing demand for energy. Single-phased emitter-based composed of transparent conducting oxides (TCOs) nanocrystals and fluorescent dyes can potentially revolutionize the typical composition of phosphors, the processing technology founded on the binding of dye acceptors on the surface of nanocrystals, and the configurations of the light-emitting diodes (LEDs) and electroluminescence devices. The hybrid white-light-emitting nanomaterial is based on the expanded spectral range of the donor-acceptor pair (DAP) emission originated from the γ-gallium oxide nanocrystals via Förster resonance energy transfer (FRET) to the surface-anchored fluorescent dyes. The emission of the nanocrystals and the sensitized emission of the chromophore act in sync as an internal relaxation upon the excitation of the γ–gallium oxide nanocrystals. It extends the lifetime of the secondary fluorescent dye chromophore and the internal relaxation within this hybrid complex act as a sign for a quasi single chromophore. The model system of white-light-emitting nanostructure system developed based on this technology is the γ–gallium oxide nanocrystals-Rhodamine B lactone (RBL) hybrid complex. The sufficient energy transfer efficiency of 31.51% within this system allowed for the generation of white-light emission with the CIE coordinates of (0.3328, 0.3380) at 5483 K. The relative electronic energy differences of the individual components within the hybrid systems based on theoretical computation suggested that the luminance of the nanocomposite comprised of RBL is dominantly mediated by FRET. The production of white-light-emitting diode (WLED) based on this technology have been demonstrated by solution deposition of the hybrid nanomaterials to the commercially available ultraviolet (UV) LED due to the versatility and chemical compatibility of the developed phosphors.

Porous metal oxides formed by supercritical carbon dioxide (SCCO2) treatments at low temperature were used for displays, solar cells, and light emitting diodes (LEDs) applications. The SCCO2 fluid, also known as green solvents, exhibits low viscosity, low surface tension and high diffusivity as gases, and high density and solubility same with liquids. In this thesis, we successfully fabricated porous antimony-doped tin oxide (ATO) and porous indium tin oxide (ITO) by the SCCO2 treatments. In addition, the treatment can also be used to improve the work function and surface energy of ITO anode of an organic LED (OLED). The performance of the OLEDs was drastically enhanced in comparison with that of the devices without any ITO surface treatments. First, the porous ATO films were formed by the SCCO2 treatment for absorption of silver molecules in silver electro deposition devices. The porosity, resistivity and average optical transmittance of the porous ATO film in visible wavelength were 43.1%, 3 £[-cm and 90.4%, respectively. For the silver electro deposition devices with the porous ATO film, the transmittance contrast ratio of larger than 12 in visible spectrum was obtained at an operating voltage of 1.5 V. Furthermore, for the 0.25 cm2 device, the switching time of 4.5 seconds was achieved by applying a square-wave voltage ranging from 1.5 to -0.2 V between the electrodes. On the other hand, the porous ITO with low refractive index was prepared by SCCO2/IPA treatment on gel-coated ITO thin films. The high refractive index of the ITO film was achieved by long-throw radio-frequency magnetron sputtering technique at room temperature. The index contrast (£Gn) was higher than 0.6 between porous ITO and sputtered ITO films. The large £Gn is useful for fabricating conductive anti-reflection (AR) and high reflection (HR) structures using the porous ITO on sputtered ITO bilayers. The weighted average reflectance and transmittance of 4.3% and 83.1% were achieved for the double-layer ITO AR electrode with a sheet resistance of 1.1 K£[/¡E. For HR structures, the reflectance and sheet resistance were 87.9% and 35 £[/¡E with 4 periods ITO bilayers. Finally, the SCCO2 treatments with strong oxidizer H2O2 were proposed to modify surface property of ITO anode of a fluorescent OLED. The highest work function and surface energy of 5.5 eV and 74.8 mJ/m2 was achieved by the SCCO2/H2O2 treatment. For the OLED with 15 min SCCO2 treatment at 4000 psi, the turn-on voltage and maximum power efficiency of 6.5 V and 1.94 lm/W were obtained. The power efficiency was 19.3% and 33.8% higher than those of the OLEDs with oxygen plasma treated and as-cleaned ITO anodes.

In this thesis, we investigated several photoelectric material systems consisted of conjugated polymers by means of computer simulation. We combined several theory and simulation methods to meodeling different subjects from atomic to mesoscopic scale. We dealt with the problems such as quantum efficiency, structure characteristic, and the phase behavior in material. We hope to have better understanding of the relationship between structure characteristic and functional property in material. It will help an engineering designer to adjust the variables that optimize characteristics linking the synthesis of advanced materials with desired physical properties. This work can be divided into three parts. Long side chain substituted PPV polymers applied in light-emitting diode material : Molecular dynamics simulations were employed to investigate structure features and segment orientation of four poly(phenylene vinylene) (PPV)-like conjugated polymers with long flexible side chains at room temperature. In the simulations, the main chains of the polymers were found to be semi-rigid and to exhibit a tendency to coil into ellipsoidal helices or form zigzag conformations of only limited regularity. It was shown that continuous segments of a chain which are quasi-coplanar along the backbone are in a range of 2~4 repeat units. This implies that long-range electron transfer along same backbones of these polymers may not happen but may be mediated by interchain interactions. The ordered orientation and coupling distance of interchain aromatic rings are found to correlate with important optical properties of materials. Then we combined molecular dynamics simulation and density matrix methods modeling of amorphous light-emitting polymers. A simplified method combining molecular dynamics (MD) simulation and density matrix (DM) theory was developed for the prediction of optical properties of long side chain substituted poly(phenylene vinylene) (PPV) polymers. This MD+DM method takes account of the complexity of molecular packing of polymer chains. The method has been tested to simulate the absorption spectra of four model systems. The wavelengths of absorption maxima of the calculated spectra of these four conjugated polymers are in reasonable agreement with experimental data. The simulation also demonstrated that the importance of including interchain interactions in the calculation. Ion-conducting polymer sPBI-PS(Li+): To understand the mechanism of ionic migration in the amorphous matrixes of polymer electrolytes is crucial for their applications in modern technologies. Here, molecular dynamics (MD) simulation was carried out to investigate the ionic conduction mechanism of a particular conjugated rigid-rod polymer, sPBI-PS(Li+). The backbone of this polymer is poly[(1, 7- dihydrobenzo[1, 2-d:4,5-d¡¦]diimidazole- 2,6-diyl)-2-(2-sulfo)-p-phenylene]. The polymer has pendants of propane sulfonate Li+ ionomer. The MD simulations showed that the main chains of sPBI-PS(Li+) are in layer-like structure. The further detailed structure analysis suggested that the £k-electron of this polymer is not delocalized among aromatic rings. This agrees with the experimental result that sPBI-PS(Li+) shows no electronic conductivity and the conductivity of this polymer is mainly ionic. The calculated migration channels of lithium ions and electrostatic potential distributions indicated clearly that the polymer matrix is anisotropic for the migrations of ions. The migration of lithium ions along the longitudinal direction is more preferable than that along the transverse direction. The relaxations of the polymer host were found to play important roles in the transfer process of lithium ions. The hopping of lithium ion from one -SO3-1 group to another is correlated strongly with characteristic motions of -SO3-1 group on a time scale of about 10-13 s. Self-assembly functional material. Dissipative particle dynamics (DPD) simulations were carried out to investigate mixed ionic and non-ionic molecules, sodium tetradecyl sulfate (STS) and tetradecyl triethoxylated ether (C14E3) aqueous system. Different types of mixed micelles are formed depending on the concentrations of STS and C14E3. Our results are in good agreement to the early NMR measurements. From the investigation of surfactant aggregation, we understand the self-assembly mechanism and classical phase behavior in general diblock copolymer. Further, we investigated the self-assembly process on a particular mushroom-shaped supramolecular film material from molecular character to phase behavior. The miniaturized rod-coil triblock copolymers (PS-PI-RCBC) HEMME had been found to self-assemble into well-ordered nanostructures and unusual head to tail multilayer structure. The purpose of our study is to obtain fundamental understanding the connection of the inherent morphological characterization of single molecule and the mechanism of phase behavior of this polar self-assembly system. Dissipative particle dynamics simulation was carried out to study the mechanism of phase behavior of the solvent-copolymers system. We found that the solvent-induced polar effect under different temperature is important in the process of self-assembly of block copolymers. In different temperature the solvent induces hybrid structure aggregation. Our results are consistent with experimental observations and give evidence for a special mechanism governing the unusual phase behavior in thin films of modulated phases. The sizes and stabilization energies of mushroom-shaped supramolecular clusters were predicted by molecular modeling method. Clusters of sizes from 16 to 90 molecules were found to be stable. In combination of classical and simple quantum mechanical calculations, the band gaps of HEMME clusters with various sizes were estimated. The band gap was converged at 2.45 eV for cluster contains 90 molecules. Nonlinear optical properties of the material were investigated by the semi-empirical quantum mechanical calculations of molecular dipole moment and hyperpolarizabilities. Significant second-order nonlinear optical properties were shown from these calculated properties.

In this work, well-defined and stable thin films based on polythiophene and its derivative, are employed as the hole-injection contact of organic light-emitting diodes (OLED). The polymer films are obtained by the electropolymerization or the electrochemical doping/dedoping of a spin-coated layer. Their electrical properties and energetics are tailored by electrochemical adjustment of their doping levels in order to improve the hole-injection from the anode as well as the performance of small molecular OLEDs. By using dimeric thiophene and optimizing the electrodeposition parameters, a thin polybithiophene (PbT) layer is fabricated with well-defined morphology and a high degree of smoothness by electro-polymerization. The introduction of the semiconducting PbT contact layer improves remarkably the hole injection between ITO anode and the hole- transport layer (NPB) due to its favourable energetic feature (HOMO level of 5.1 eV). The vapor-deposited NPB/Alq3 bilayer OLEDs with a thin PbT interlayer, show a remarkable reduction of the operating voltage as well as enhanced luminous efficiency compared to the devices without PbT. Investigations have also been made on the influence of PbT thickness on the efficiency and I-V feature as well as device stability of the OLED. It is demonstrated that the use of an electropolymerization step into the production of vapor deposited molecular OLED is a viable approach to obtain high performance OLEDs. The study on the PbT has been extended to poly(3,4-ethylenedioxythiophene) (PEDT) and the highly homogenous poly(styrenesulfonate) (PSS) doped PEDT layer from a spin-coating process has been applied. The doping level of PEDT:PSS was adjusted quantitatively by an electrochemical doping/dedoping process using a p-tuoluenesulfonic acid containing solution, and the redox mechanism was elucidated. The higher oxidation state can remain stable in the dry state. The work function of PEDT:PSS increases with the doping level after adjusting at an electrode potential higher than the value of the electrochemical equilibrium potential (Eeq) of an untreated film. This leads to a further reduction of the hole-injection barrier at the contact of the polymeric anode/hole transport layer and an ideal ohmic behavoir is almost achieved at the anode/NPB interface for a PEDT:PSS anode with very high doping level. Molecular Alq3-based OLEDs were fabricated using the electrochemically treated PEDT:PSS/ITO anode, and the device performance is shown to depend on the doping level of polymeric anode. The devices on the polymer anode with a higher Eeq than that for the unmodified anode, show a reduction of operating voltage as well as a remarkable enhancement of the luminance. Furthermore, it is found that the operating stability of such devices is also improved remarkably. This originates from the removal of mobile ions such as sodium ions inside the PEDT:PSS by electrochemical treatment as well as the planarization of the ITO surface by the polymer film. By utilizing an Al/LiF cathode with an enhanced electron injection and together with a high Eeq- anode, a balanced injection and recombination of hole and electron is achieved. It leads to a further reduction of the operating voltage and to a drastic improvement of EL efficiency of the device as high as 5.0 cd/A. The results demonstrate unambiguously that the electrochemical treatment of a cast polymer anode is an effective method to improve and optimize the performance of OLEDs. The method can be extended to other polythiophene systems and other conjugated polymers in the fabrication of the OLEDs as well as organic transistors and solar cells.

A numerical model and results for the quantitative simulation of multilayer organic light emitting diode (OLED) and organic solar cell (OSC) are presented. In the model, effects like bipolar charge carrier drift and diffusion with field-dependent mobilities, trapping, dopants, indirect and direct bimolecular recombination, singlet Frenkel exciton diffusion, normal decay and quenching effects are taken into account. For an adequate description of multilayer devices with energetic barriers at interfaces between two adjacent organic layers, thermally assisted charge carrier hopping through the interface, interface recombination, and formation of interface charge transfer (CT) states have been introduced in the model. For the simulation of OSC, the generation of carrier pairs in the mixed layer or at the interface is additionally implemented. The light absorption profile is calculated from optical simulations and used as an input for the electrical simulation. The model is based on three elements: the Poisson equation, the rate equations for charge carriers and the rate equations for singlet Frenkel excitons. These equations are simultaeously solved by spatial and temporal discretisation using the appropriate boundary conditions and electrical parameters. The solution is found when a steady state is reached, as indicated by a constant value of current density. The simulation provides a detailed look into the distribution of electric field and concentration of free and trapped carriers at a particular applied voltage. For organic light emitting diodes, the numerical model helps to analyze the problems of different structures and provides deeper insight into the relevant physical mechanisms involved in device operation. Moreover, it is possible to identify technological problems for certain sets of devices. For instance, we could show that ? in contrast to literature reports - the contact between Alq3 and LiF/Al did not show ohmic behaviour for the series of devices. The role of an additional organic blocking layer between HTL and EML was presented. The explanation for the higher creation efficiency for singlet excitons in the three-layer structure is found in the separation of free holes and electrons accumulating close to the internal interface 1-Naphdata/Alq3. The numerical calculation has demonstrated the importance of controlled doping of the organic materials, which is a way to obtain efficient light emitting diodes with low operating voltage. The experimental results has been reproduced by numerical simulation for a series of OLEDs with different thicknesses of the hole transport layer and emitting layer and for doped emitting layers. The advantages and drawbacks of solar cells based on flat heterojunctions and bulk heterojunctions are analyzed. From the simulations, it can be understood why bulk-heterojunctions typically yield higher photocurrents while flat heterojunctions typically feature higher fill factors. In p-i-n ?structures, p and n are doped wide gap materials and i is a photoactive donor-acceptor blend layer using, e.g,. zinc phthalocyanine as a donor and C60 as an acceptor component. It is found that by introducing trap states, the simulation is able to reproduce the linear dependence of short circuit currents on the light intensity. The apparent light-induced shunt resistance often observed in organic solar cells can also be explained by losses due to trapping and indirect recombination of photogenerated carriers, which we consider a crucial point of our work. However, these two effects, the linear scaling of the photocurrent with light intensity and the apparent photoshunt, could also be reproduced when field-dependent geminate recombination is assumed to play a dominant role. First results that show a temperature independent short circuit photocurrent favour the model based on trap-mediated indirect recombination.

This thesis addresses a multi-phase research and development project that spanned nearly four years, targeted at providing an ultra high-efficiency, user-friendly, and economic intelligent lighting solution for commercial facility applications, initially targeting underground parking specifically. The system would leverage the strengths of four key technologies: high brightness white Light Emitting Diodes (LEDs), wireless sensor and actuator networks, single board computers, and cloud computing. An introduction to these technologies and an overview of how they were combined to build an intelligent lighting solution is given, followed by an in-depth description of the design and implementation of one of the main subsystems – the Sensor Middleware System – residing on a single board computer. Newly-available LED luminaires (a.k.a. light fixtures) bring the combination of high efficiency, reliability, illumination quality, and long-lifetime to the lighting market. Emerging low-power – and recently low-cost – 802.15.4 wireless networks offer high controllability and responsiveness to deployed luminaires and sensors. The cost- associativity, low maintenance, and easy build-up of Internet Data Center “cloud” computing resources make data collection and remote management infrastructure for Building Automation Systems accessible to even small companies. Additionally, these resources can be much more appropriately sized and allocated, which reduces energy use. These technologies are combined to form an Intelligent Lighting System (ILS). Fitting well within the Internet of Things paradigm, this highly distributed messaging-based “system of systems” was designed to be reliable through loose coupling – spanning multiple network layers and messaging protocols. Its goal was to deliver significant energy savings over incumbent technologies, configurable and responsive lighting service behaviour, and improved experience for users within the facility (pedestrians and drivers) and those interacting with its web-based tools (building managers and ILS administrators). The ILS was partitioned into three main subsystems as follows. The installed Wireless Field Network (WFN) of luminaires and sensors provided coordinated scheduled and real-time output level adjustment (i.e. dimming), with the help of motion sensor triggers. The Monitoring and Configuration System (MCS) in the cloud provided remote data collection and a web-based monitoring and configuration Graphical User Interface application. Network hardware and Message-Oriented Middleware (MOM) were responsible for tying these subsystems together. The MOM layer that provided the message brokering, translating, envelope wrapping, and guaranteed delivery services between the WFN and MCS, as well as field supervisory and quality-of-service functions for the WFN, was called the Sensor Middleware System (SMS). It was hosted on a single board computer located at the facility. / Graduate

This PhD thesis is devoted to study electro-optic properties of Gemanium/Silicon-Germanium (Ge/SiGe) multiple quantum wells (MQWs) for light modulation, detection, and emission on Si platform. It reports the first development of high speed, low energy Ge/SiGe electro-absorption modulator in a waveguide configuration based on the quantum-confined Stark effect (QCSE), demonstrates the first Ge/SiGe photodiode with high speed performance compatible with 40 Gb/s data transmission, and realizes the first Ge/SiGe light emitting diode based on Ge direct gap transition at room temperature. Extensive DC and RF measurements were performed on each tested prototype, which was realized using the same epitaxial growth and fabrication process. Simple theoretical models were employed to describe experimental properties of the Ge/SiGe MQWs. The studies show that Ge/SiGe MQWs could potentially be employed as a new photonics platform for the development of a high speed optical link fully compatible with silicon technology.

The global lighting source energy consumption accounts for about 22% of the total electricity generated. New high-efficiency solid-state light sources are needed to reduce the ever increasing demand for energy. Single-phased emitter-based composed of transparent conducting oxides (TCOs) nanocrystals and fluorescent dyes can potentially revolutionize the typical composition of phosphors, the processing technology founded on the binding of dye acceptors on the surface of nanocrystals, and the configurations of the light-emitting diodes (LEDs) and electroluminescence devices. The hybrid white-light-emitting nanomaterial is based on the expanded spectral range of the donor-acceptor pair (DAP) emission originated from the γ-gallium oxide nanocrystals via Förster resonance energy transfer (FRET) to the surface-anchored fluorescent dyes. The emission of the nanocrystals and the sensitized emission of the chromophore act in sync as an internal relaxation upon the excitation of the γ–gallium oxide nanocrystals. It extends the lifetime of the secondary fluorescent dye chromophore and the internal relaxation within this hybrid complex act as a sign for a quasi single chromophore. The model system of white-light-emitting nanostructure system developed based on this technology is the γ–gallium oxide nanocrystals-Rhodamine B lactone (RBL) hybrid complex. The sufficient energy transfer efficiency of 31.51% within this system allowed for the generation of white-light emission with the CIE coordinates of (0.3328, 0.3380) at 5483 K. The relative electronic energy differences of the individual components within the hybrid systems based on theoretical computation suggested that the luminance of the nanocomposite comprised of RBL is dominantly mediated by FRET. The production of white-light-emitting diode (WLED) based on this technology have been demonstrated by solution deposition of the hybrid nanomaterials to the commercially available ultraviolet (UV) LED due to the versatility and chemical compatibility of the developed phosphors.

Orientador: Peterson Bueno de Moraes / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Tecnologia / Made available in DSpace on 2018-08-23T06:55:03Z (GMT). No. of bitstreams: 1 Oliveira_CleliaAparecidadaSilva_M.pdf: 1434373 bytes, checksum: 2411a1ce9b13fbe4e8f7d778c6dfd3ea (MD5) Previous issue date: 2013 / Resumo: A indústria têxtil gera elevados volumes de efluentes com alta carga orgânica e compostos recalcitrantes, os quais são tratados por sistemas baseados em processos físicos, químicos e biológicos convencionais. Entretanto, o caráter não destrutivo dos tratamentos convencionais representa um sério problema no setor. Nos últimos 20 anos, os Processos Oxidativos Avançados (POA) têm estado em evidência devido à sua capacidade em degradar inúmeros compostos orgânicos contidos em águas e efluentes. Uma grande quantidade de trabalhos utilizando luz UV a partir de lâmpadas de vapor de mercúrio tem resultado em elevada eficiência de degradação de substratos recalcitrantes incluindo efluentes têxteis; entretanto, demandam elevado consumo de energia elétrica, encarecendo o tratamento. Em contrapartida, o surgimento de Diodos Emissores de Luz Ultravioleta (LED UV) abre novas fronteiras de aplicação no campo de tratamento de águas residuárias, quanto a custo, operacionalidade e tamanho dos sistemas. Nesse trabalho estudou-se a degradação de um efluente têxtil simulado contendo o corante Remazol Azul Brilhante (C.I. Reactive Blue 19) através de processos eletroquímicos e fotoeletroquímicos que utilizam LED UV, utilizando-se dois reatores: um operando em batelada contendo o fotocatalisador TiO2 e o outro, em fluxo, contendo um cátodo (tela cilíndrica de aço-inoxidável), um tubo de quartzo contendo os LED UV e o Anodo Dimensionalmente Estável (ADE 70%TiO2/30%RuO2). Os resultados demonstraram que, no reator de bancada, a eficiência de remoção de cor foi de 100% para concentração inicial de 50 mg L-1 do corante, em 24 horas de tratamento. No reator em fluxo, utilizando Na2SO4 como eletrólito, o processo eletrolítico resultou em eficiência de 65%; o fotoeletrocatalítico, em 68%, operando a 750 L h-1 e em 57,3 mA cm-2. Quando foi utilizado o eletrólito NaCl, obteve-se remoção de 100% da cor em 5 minutos de tratamento a 750 L h-1, independente da concentração inicial do corante utilizada (50 mg L-1 ou 100 mg L-1), da concentração do eletrólito (0,05 M ou 0,1 M), da densidade de corrente (14,3 mA cm-2 , 28,7 mA cm-2 ou 57,3 mA cm-2) e do processo utilizado / Abstract: The textile industry generates large amount of wastewater containing significant organic load and recalcitrant compounds, which in most cases are treated by conventional systems involving physical, chemical and biological processes, the latter represented mainly by activated-sludge treatment. However, the non-destructive profile of conventional treatments is a serious problem for textile-based industry. Over the past 20 years, the study of Advanced Oxidation Processes (AOP) has been carried out due to its high capacity degradation of numerous organic pollutants contained in waters and wastewaters. Research using UV light from mercury vapor lamps usually has resulted in high efficiency degradation of recalcitrant substrates including textile effluents but requires high electrical power consumption besides other drawbacks. In contrast, the emergence of Ultraviolet Light Emitting Diodes (UV LED) opens new perspectives for application on wastewater treatment, concerning efficiency, footprint and costs of the systems. In this work we studied the degradation of a simulated wastewater containing a textile dye, Remazol Brilliant Blue (C.I. Reactive Blue 19) through electrochemical and photoelectrochemical processes using UV LED as ultraviolet radiation source. The experimental apparatus consisted of two systems: the first, a bench-scale reactor containing TiO2 photocatalyst (P25 DEGUSSA) in solution, and another pilot-scale system operated in batch recirculation mode composed of an tubular stainless-steel screen cathode, a quartz tube containing the UV LED and a oxide-coated titanium anode (DSA©30%TiO2/70%RuO2). The results showed total decolorization of a solution containing 50 mg L-1 of RB in 24-hour treatment in the bench-scale reactor. Tests on flow reactor using Na2SO4 as supporting electrolyte resulted in 65% of color removal using electrolytic process and 68% for photoelectrocatalytic process operating at 750 L h-1 and 57.3 mA cm-2. In experiments using the electrolyte NaCl it was obtained 100% in the color degradation within 5 minutes of treatment at 750 L h-1, regardless of the: initial concentration of dye used (50 mg L-1; 100 mg L-1), concentration of the electrolyte (0.05 M; 0.1 M) and current density value (14.3; 28.7; 57.3 mA cm-2) / Mestrado / Tecnologia e Inovação / Mestra em Tecnologia

Les matériaux semi-conducteurs III-N sont à l’origine d’une véritable révolution technologique. Mais malgré l’effervescence autour de ces sources lumineuses, leurs performances dans le vert et l’UV demeurent limitées. La principale raison à cela est l’orientation cristalline (0001)III-N (dite polaire) selon laquelle ces matériaux sont généralement épitaxiés et qui induit de forts effets de polarisation. Ces effets peuvent cependant être fortement atténués par l’utilisation d’orientations de croissance dite semi-polaires. Malheureusement, les films de GaN semi-polaires hétéroépitaxiés présentent des densités de défauts très importantes, ce qui freine très fortement leur utilisation. L’enjeu de cette thèse de doctorat est de réaliser des films de GaN semi-polaire (11-22) de haute qualité cristalline sur un substrat de saphir en utilisant la technique d’épitaxie en phase vapeur aux organométalliques. La réduction de la densité de défaut étant l’objectif majeur, différentes méthodes d’ingénieries de défauts s’appuyant sur la structuration de la surface des substrats et sur la croissance sélective du GaN ont été développées. Elles ont permis d’établir l’état de l’art actuel du GaN semi-polaire hétéroépitaxié. Par la suite, dans le but d’améliorer les performances des DELs vertes, une étude dédiée à l’optimisation de leur zone active a été menée. D’autre part, le développement de substrats autosupportés de GaN semi-polaires, ainsi que la confection de cristaux 3D de grande taille dont la qualité cristalline est comparable aux cristaux de GaN massifs ont été démontrés. Ces deux approches permettant de s’approcher encore plus de la situation idéale que serait l’homoépitaxie. / Nitride based materials are the source of disruptive technologies. Despite the technological turmoil generated by these light sources, their efficiency for green or UV emission is still limited. For these applications, the main issue to address is related to strong polarization effects due to the (0001)III-N crystal growth orientation (polar orientation). Nevertheless these effects can be drastically decreased using semipolar growth orientations. Unfortunately semipolar heteroepitaxial films contain very high defect densities which hamper their adoption for the time being. The aim of this doctoral thesis is to achieve semipolar (11-22) GaN of high quality on sapphire substrate by metalorganic chemical vapor deposition. Defect reduction being the main objective, several defect engineering methods based on sapphire substrate patterning and GaN selective area growth have been developed. Thanks to refined engineering processes, the remaining defect densities have been reduced to a level that establishes the current state of the art in semipolar heteroepitaxial GaN. These results have enabled the achievement of high quality 2 inches semipolar GaN templates, thus forming an ideal platform for the growth of the forthcoming semipolar optoelectronic devices. With this in mind, to improve green LEDs, a study dedicated to the optimization of their active region has been conducted. Finally, the development of semipolar freestanding substrate has been performed, and beyond, the realization of large size crystals with a structural quality similar to that of bulk GaN has been demonstrated. These last two approaches pave the way to quasi-homoepitaxial growth of semipolar structures.