Les matériaux conjugués ont fait l’objet de beaucoup de recherches durant les dernières années. Les nouveaux matériaux présentent des propriétés intéressantes que ce soit au niveau optique, électrique, mécanique ou même les trois en même temps. La synthèse reste la difficulté principale dans la fabrication de dispositifs électroniques. Les méthodes utilisées pour y parvenir sont l’électropolymérisation, le couplage de Suzuki ou de Wittig. Ces techniques comportent encore de nombreuses contraintes et s’avèrent difficilement réalisables à grande échelle. Les thiophènes, les pyrroles et les furanes ont démontré une bonne conductibilité et une bande de conduction basse due à une conjugaison accrue. L’objectif ici est de synthétiser des oligomères principalement composés de thiophènes dans le but d’en caractériser les propriétés spectroscopiques, électrochimiques et de conduction. La synthèse est souvent l’étape délicate de la fabrication de matériaux conjugués. Nous présentons ici une méthode de synthèse simple par modules avec des unités hétérocycliques. Les modules complémentaires sont attachés par condensation entre un aldéhyde et une amine menant à la formation d’un lien robuste, l’azomethine. Les résultats des propriétés photophysiques et électrochimiques de ces matériaux conjugués seront présentés. En ayant recours à différents groupes électrodonneurs et électroaccepteurs, en variant le degré de conjugaison ou en utilisant différents hétérocycles, les propriétés spectroscopiques, électrochimiques et de bande de conduction peuvent être adaptées à volonté, ce qui en fait des matériaux aux propriétés modelables. Ces nouvelles molécules seront analysées pour en déceler les propriétés recherchées dans la fabrication d’OLED. Nous explorerons les domaines de l’oxidation electrochimique réversible et de la polymérisation menant à la fabrication de quelques prototypes simples. / Conjugated materials have received much attention recently as they show promise for industrial applications. These materials are interesting because of the many new possibilities for devices combining unique optical, electrical and mechanical properties. The synthesis is the major difficulty in the fabrication of electronic devices. Usual methods to do so are electropolymerisation, Suzuki or Wittig coupling. Those techniques are full of constraints and are difficult to scale-up. Thiophenes, pyrroles and furans demonstrated good conductibility and low band-gap due to increased conjugation. Our main goal is to synthesize oligomers made principally of thiophene to characterize their spectroscopic, electrochemical and conduction properties. Synthesis is the most important step in the making of conjugated material. A synthetically simple and modular route to novel conjugated material consisting of heterocyclic units is presented. These complementary modules are linked by condensing aldehydes and amines leading to robust azomethine bonds. The resulting photophysical and electrochemical properties of these conjugated materials will be presented. Through the use of different electron donor and acceptor groups, degree of conjugation or by using different heterocycles, the spectroscopic, electrochemical and band-gap properties can be tailored leading to materials with tunable properties. Those new molecules will be analysed to detect properties suitable for OLED fabrication. This presentation will also address the electrochemical reversible oxidation and polymerization of these compounds leading to the making of simple devices.

This study focuses on the architectural modification of pin-type small-molecule organic solar cells, in particular on the absorption layer and its influence on the key solar cell parameters, such as short circuit current density, fill factor and open circuit voltage. Three different approaches have been applied to improve the match between the solar spectrum and the spectral sensitivity of organic solar cells. In the first part, deposition parameters such as substrate temperature, gradient strength and (graded) absorption layer thickness are evaluated and compared to organic solar cells with homogeneously deposited absorption layers. Moreover, the gradient-like distribution of the absorption layer is characterized optically and morphological effects have been extensively studied. In order to isolate the origin of the efficiency improvement due to the graded architecture, voltage-dependent spectral response measurements have been performed and gave new insights. The second part concentrates on the efficient in-coupling of converted UV light, which is usually lost because of the cut off properties of organic light in-coupling layers. Via Förster resonance energy transfer, the absorbed UV light is re-emitted as red light and contributes significantly to higher short circuit current densities. The correlation between doping concentration, simple stack architecture modifications and the performance improvement is duly presented. In the third and last part, the impact of tri-component bulk heterojunction absorption layers is investigated, as these have potential to broaden the sensitivity spectrum of organic solar cells without chemical modification of designated absorber molecules. Along with the possibility to easily increase the photocurrent, an interesting behavior of the open circuit voltage has been observed. Knowledge about the impact of slight modifications within the solar stack architecture is important in order to be able to improve the device efficiency for the production of cheap and clean energy.

Thesis (M.S.)--Florida State University, 2006. / Advisor: James R. Simpson, Florida State University, College of Engineering, Dept. of Industrial Engineering. Title and description from dissertation home page (viewed Sept. 22, 2006). Document formatted into pages; contains ix, 95 pages. Includes bibliographical references.

Organic electronics is a hot and modern topic which holds great promise for present and future applications. One such application is the light-emitting electrochemical cell (LEC). It can be fully solution processed and driven at low voltage providing light emission from a large surface. Inkjet printers available today can print a variety of inks, both solutions and dispersions. The technique is scalable and a quick and easy way to accurately deposit small quantities of material in user definable patterns onto a substrate. This is desirable to make low cost and efficient optical devices like displays. In this thesis it has been shown that solid electrolytes, after being dissolved in a liquid solvent, can be inkjet printed into a set of well separated distinct drops with an average maximum thickness of 150 nm. The electrolytes are commonly used in LECs and comprised by poly(ethylene glycol) with molar masses ranging from 1 – 35 kg/mol, and potassium trifluoromethanesulfonate (KCF3 SO3 )—together dissolved incyclohexanone to form an ink. The smallest achieved edge to edge distance between the printed drops was 40 μm. Together with a drop diameter of 50 μm it yields a coverage of 24% at a resolution of 280 dpi. Profiles of dried deposited drops of electrolyte were examined with a profilometer, which showed adistinct coffee ring effect on each drop. In particular, the ridges of the coffee rings were broken into pillar like shapes, together forming a structure akin to a scandinavian ancient remnant called stone ship. Different drop diameters were measured in and between the indium tin oxide samples. The drops’ speeds and sizes atejection from the nozzles seemed unchanged, and wettability is most probably the physical phenomena tolook into in order to understand what generates the differences. Local changes in surface roughness and/or surface energy, possibly originating from the cleaning process of the samples, is most likely the cause. No indications towards large differences in surface tension between the printable inks were seen, however their viscoelastic properties were not measured. As part of the thesis work a LEC characterization set-up was built. It drives a LEC at constant currentand measures the driving voltage, -current, and luminance over time. The set-up is controlled by a Labview virtual instrument and the data exported to a text-file for later analysis. The precision of the luminance measurements is ±0.1 cd/m2 for readings < 50 cd/m2 , but the accuracy is uncertain. The conclusion of this thesis is that it is indeed possible to print solid electrolytes dissolved in cyclo-hexanone with an inkjet printer. However, in order to fully understand the spreading and drying of thedrops, studies of the inks’ viscoelastic properties, together with surface roughness and -energy density ofthe substrates, are needed. The largest molar mass of nicely printable poly(ethylene glycol), at an ink concentration of 10 mg/ml, was 35 kg/mol. This is comparable to the molar mass of an active light-emittingmaterial, “SuperYellow”, often used in LECs. Even though their respective molecular structures are very different, this indicates that inkjet printing of complete LEC-inks, containing both the active material and solid electrolyte, is feasible. Most probably it would require substantial tuning of the printing parameters. This thesis provides further hope for future fully inkjet printed LECs.

The 2-dimensional semiconductor family of materials called transition metal dichalcogenides (2d-TMDs) offers many technological advantages: low power consumption, atomically-precise interfaces, lack of nuclear spins and ease of functional integration with other 2d materials are just a few. In this work we harness the potential of these materials as a platform for quantum devices: develop a method by which we can deterministically create single-photon emitting sites in 2d-TMDs, in large-scale arrays. These we call quantum dots (QDs): quantum confinement potentials within semiconductor materials which can trap single-excitons. The single excitons recombine radiatively to emit single-photons. Single-photon sources are a crucial requirement for many quantum information technology (QIT) applications such as quantum cryptography and quantum communication. The QDs are formed by placing the flakes over substrates nano-patterned with protru- sions which induce local strain and provoke the quantum confinement of excitons at low temperatures. This method has been successfully tested in several TMD materials, hence achieving quantum light at different wavelengths. We present one of the very few systems where quantum confinement sites have been shown to be deterministically engineered in a scalable way. Moreover, we have demonstrated how the 2d-based QDs can be embedded within 2d- heterostructures to form functional quantum devices: we have used TMD monolayers along with other 2d-materials - graphene and hexagonal boron nitride - to create quan- tum light-emitting diodes that produce electrically-driven single-photons. Again, very few single-photon sources can be triggered electrically, and this provides a great ad- vantage when considering on-chip quantum technologies. Finally, we present experimental steps towards using our architecture as quantum bits: capturing single-spins inside the QDs, using field-effect type 2d-heterostructures. We are able to controllably charge the QDs with single-electrons and single-holes – a key breakthrough towards the use of spin and valley pseudospin of confined carriers in 2d-materials as a new kind of optically addressable matter qubit. This work presents the successful marriage of 2d-semiconductor technology with QIT, paving the way for 2-dimensional materials as platforms for scalable, on-chip quantum photonics.

Dans ce travail, les dégradations des diodes électroluminescentes (DEL) ont été étudiées en identifiant et en évaluant leurs signatures électriques et photométriques en vieillissement accéléré sous stress thermique et électrique. Un prototype de banc de test expérimental a été développé et construit spécifiquement pour cette étude ce qui nous a permis de tester 128 échantillons en appliquant différentes conditions de stress thermiques et électriques. Quatre types différents de DEL ont été étudié avec des caractéristiques techniques similaires (température de couleur, courant nominal, mono-puce,...) mais avec des technologies différentes couvrant les principaux acteurs du marché (Cree, Osram, Philips et Seoul Semiconductor). Les échantillons ont d'abord été caractérisés à leur état initial, puis soumis à des conditions de stress électrique (à 350mA ou 1050mA) et thermique (fixé à 50°C). Les mécanismes de défaillance ont été analysés en étudiant l'évolution des signatures électriques et photométriques. Ces caractérisations ont permis d'évaluer et de déterminer l'origine des dégradations à différents niveaux : puce semi-conductrice, interconnexions, phosphore ou encapsulation du dispositif. Les caractérisations électriques nous ont permis d'identifier les mécanismes de dégradation de la puce semi-conductrice et de déterminer la nature des dégradations au niveau du contact ohmique du dispositif (sous fort courant injecté). Les caractérisations photométriques complètent cette étude en évaluant les dégradations associées à l'optique (encapsulation et packaging). / In this work, the degradation of light emitting diodes (LEDs) is studied by identifying and evaluating their aging signature during the stress time. The custom-made experimental test bench is built for realization of the test measurement. Through this experimental test bench, it allows to test a large amount of LED samples and enable to select different temperature condition and different current stress level. There are four different types of LED with similar characteristic in term of their color temperature, IF, VF, power (1W) and as monochip, but different technology coming from Cree, Osram, Philips and Seoul Semiconductor. The devices are firstly characterized their electrical and photometrical characteristic at their initial state, then they are submitted to different current stress condition at low current stress (350mA) and high current stress (1000mA) while the thermal stress is fixed at one temperature (50°C). The study of these devices failure mechanism is archived by using the primary method based on the electrical and photometrical characterization of the devices that allows to evaluate their degradation at different locations of the device components such as semiconductor chip, interconnection and device's package. The electrical characteristic of the device's I-V curve: at low injected current level and reverse bias allow us to identify the degradation characteristic of device's semiconductor chip, at high injected current level allows us to determine the degradation of device's ohmic contact and photometric characteristic allows us to evaluate the degradation of device's package system.

Ce travail porte sur l'amélioration des performances en vieillissement de micro-écrans vidéo à matrice active en technologie OLED sur Silicium. La perte d'efficacité lumineuse et la dérive en tension induites par le vieillissement des OLED restent depuis plusieurs années un point faible inhérent à cette technologie et représente toujours un verrou dans la commercialisation des micro-écrans sur un marché encore jeune. Nous proposons ici une étude d'optimisation d'un empilement OLED blanc bi-émetteurs à émission vers le haut basée sur l'amélioration systématique des modes de défaillances reconnus des OLED et adaptée aux spécificités de réalisation de micro-écrans à très forte résolution. Des outils originaux tels que des structures simplifiées de types monocouche ou monoporteur seront utilisés pour comprendre et réduire ces différents mécanismes de dégradation. Du fait de la complexité des structures OLED actuelles, des structures simplifiées seront notamment développées et analysées dans le but d'accéder à la compréhension des phénomènes intrinsèques de dégradation opérant au sein des couches organiques, à leurs interfaces ou encore aux interfaces avec les électrodes. Une méthode de caractérisation électrique encore peu utilisée dans le cas des LED organiques, la spectroscopie d'impédance, sera également développée. Cette technique de caractérisation électrique très prometteuse et surtout non destructive permet à travers l'étude des comportements capacitifs des dispositifs l'accès à de nombreuses informations relatives à la dynamique des charges liées ou mobiles dans les zones de bulk ou interfaciales des matériaux. / The present study deals with active-matrix OLED microdisplays, based on a white top-emitting bi-emitters structure. The optimization of these devices lifetime is the main point of this manuscript. The luminous efficiency loss and the voltage drift induced while ageing of the device under constant current driving conditions are indeed key parameters. A first part consists in understanding the main degradation mechanisms known to operate in OLED devices. A focus on intrinsic mechanisms is here chosen to improve devices lifetime. Extrinsic mechanisms like encapsulation issues or other process optimization are not developed in this work. We propose here a systematic study on the influence of OLED structure parameters on initial but especially on aging performances. The optimization of anode electrical contact through plasma treatments and a thin oxide interlayer show very interesting results for reducing operating bias and voltage drift induced while aging under constant current. The enhancement of doping percentage in doped injection layers also show significant improvement on devices performances, with the great advantage of being a useful tool for controlling devices efficiency. We also find that an optimization of the emission layers thicknesses could lead to great lifetime improvement. Those results are also combined and confirmed by a Design Of Experiments meant to determine the influence of the main process parameters on devices performances. Finally, we initiate the characterization of our OLED devices using impedance spectroscopy measurements. From the modeling of single-layer structures to the understanding of simple bipolar devices through analysis of capacitive evolution of full-stack devices with time, we here show that this technic appears very useful for the understanding of charge carrier dynamic and could help reducing charge accumulation.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / This work presents an optimization methodology for lighting systems that employ LED. Initially, this work brings a calculation methodology capable of obtaining a thermal resistance of heat sink from their dimensions of area, besides enable optimization of the system through reducing their volume by through of change in the number of finned, length and consequently the weight of heat sink. Subsequently, the thesis present a new optimization methodology that has the objective of find the optimal point of operation lighting system taking into consideration the parameters of application current in the device, luminous flux, junction temperature, thermal resistance heat sink, number of LED and lifetime. An example of project is shown, confirming the theory, where the obtained results through of routine calculation coincided with the values found in experimental. The work also present the development of electronic topologies to power a public lighting system employing LED. Therefore, a driver to power of LED based in the integrated two-flyback converters was proposed. One prototype this system was implemented, where the luminaire provide a power of 63W. The experimental results proved the project methodology through of system satisfactory operation, presenting power factor near unit, high efficiency and a low input current distortion was obtained. / Este trabalho apresenta uma metodologia de otimização para sistemas de iluminação que empregam LEDs. Inicialmente, traz-se uma metodologia de cálculos capaz de obter a resistência térmica de dissipadores de calor a partir de suas dimensões de área, além de possibilitar a otimização do sistema através da redução do volume do mesmo por meio da variação do número de aletas, do comprimento e consequentemente da massa do dissipador. Posteriormente o trabalho apresenta uma nova metodologia de otimização que tem o objetivo de encontrar o ponto ótimo de operação do sistema de iluminação, levando-se em conta os parâmetros de corrente direta aplicada no dispositivo, fluxo luminoso, temperatura de junção, resistência térmica do dissipador, número de LEDs e vida útil dos mesmos. Um exemplo de projeto é demonstrado confirmando a teoria apresentada, onde os resultados obtidos através da rotina de cálculos coincidiram com os valores encontrados experimentalmente. O trabalho também apresenta o desenvolvimento de uma topologia eletrônica para alimentar um sistema de iluminação pública empregando LEDs. Dessa maneira, um driver para acionamento de LEDs baseado na integração de dois conversores flyback foi proposto. Um protótipo desse sistema foi implementado, onde a luminária apresenta uma potência de 63W. Resultados experimentais comprovam a metodologia de projeto através da operação satisfatória do sistema, apresentando fator de potência próximo ao unitário, elevada eficiência e o conteúdo harmônico da corrente de entrada do sistema de iluminação atendeu a norma.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The understanding of the interrelationships among the photometrical, electrical and thermal (photo-electro-thermal) parameters is extremely important to design lighting systems based on light-emitting diodes (LEDs), because the LEDs are highly influenced by these conditions. The efficacy and lifespan of an LED system that uses even the best LEDs, commercially available, will be only a fraction of what it would be if the electrical, thermal and optical design is poorly designed. This work proposes an improvement in the estimative of the luminous flux using photo-electro-thermal parameters, without needing any laboratory test. When designing an LED lighting system, it is possible to get almost identical results in terms of luminous flux, luminous efficacy and lifetime by scaling the parameters: intensity of the LED current, the amount of LEDs and the system design cooling. Therefore, a design methodology for LED lighting systems is also proposed. This methodology provides the creation of a design space where the designer can directly identify: the value of the luminous efficacy, thermal resistance of the heatsink and junction temperature when varying the number of LEDs and the direct current, without performing any laboratory testing or using some simulation software with high computational cost. Thus, the designer can set the initial design faster and relate it to the costs involved. Experimental tests were performed in order to validate the proposed design methodology. / O entendimento das inter-relações entre os parâmetros fotométricos, elétricos e térmicos (fotoeletrotérmicos) é extremamente importante para sistemas de iluminação que utilizam diodos emissores de luz (LEDs), pois os LEDs são extremamente sensíveis a estas condições. A eficácia e vida útil de um sistema que utiliza até mesmo os melhores LEDs do mercado será apenas uma fração do que seria se o projeto elétrico, térmico ou óptico for mal concebido. Este trabalho propõe um aprimoramento da estimativa do fluxo luminoso utilizando parâmetros fotoeletrotérmicos, sem a necessidade de realizar nenhum ensaio laboratorial. Ao projetar um sistema de iluminação a LEDs pode-se chegar a resultados quase idênticos em termos de fluxo luminoso, eficácia luminosa e vida útil dimensionando-se os seguintes parâmetros: intensidade da corrente direta aplicada, o número de LEDs utilizados e o dimensionamento do sistema de arrefecimento. Portanto, uma metodologia de projeto para sistemas de iluminação a LED também é proposta. Essa metodologia proporciona a criação de um espaço de projeto no qual o projetista pode identificar diretamente qual é o valor da eficácia luminosa, da resistência térmica do dissipador e da temperatura de junção quando são variados o número de LEDs e a corrente direta, sem realizar qualquer ensaio laboratorial ou usar algum software de simulação com alto custo computacional. Dessa maneira, o projetista pode definir o projeto inicial mais rapidamente e já relacionar os custos envolvidos. Testes experimentais foram realizados para validar o aprimoramento da estimativa de fluxo e da metodologia de projeto proposta.

Made available in DSpace on 2016-08-17T18:39:46Z (GMT). No. of bitstreams: 1 5221.pdf: 2181804 bytes, checksum: 70eb5451e6b2cbb1ae45f09f2e2c0c5f (MD5) Previous issue date: 2013-03-22 / Context and Objectives: Nowadays, phototherapy has been used to enhance physical performance and to accelerate recovery after exercise. The aim of this study was to evaluate the effects of LED therapy (850 nm) and low power (50 mW) on the physical performance of soccer players after 6 weeks of soccer training. Study design/materials and methods: a randomized, double-blind clinical trial, controlled with placebo study was conducted. Sixteen soccer athletes aged between 14 and 16 years participated in the study. The athletes were randomly allocated into 2 groups: (i) training group associated with the LED therapy (LEDT) and (ii) training group associated with the placebo LED therapy (placebo). LED therapy or placebo were applied on the quadriceps, hamstrings and sural triceps immediately after training, twice a week during 6 consecutive weeks (12 sessions of therapies). The LED device (850nm, 50 mW, 30 s on each muscle group and energy of 75 J) was used for phototherapy. The functional performance was evaluated through the jump platform (vertical jump) and photocells (10 and 35 meter races) in the period pre and post training plus LED therapy or placebo therapy. Results: the LEDT Group significantly increased the height (cm) of vertical jump (from 36.02±3.95 to 39.20±4.52; p<0.001) and the muscle power (W) (from 382.62±31.82 to 417.62±31.19; p=0.003) in this same test. The LEDT showed significant increases for the average speed (m/s) at 10 m race (from 5.94 ± 0.35 to 6.13 ± 0.45; p<0.001) and 35 m (from 7,43 ± 0,32 to 7.51 ± 0.32; p=0.003). The Placebo group showed significant increases only for the height of vertical jump (from 36.25±4.55 to 37.38±4.26; p=0.017). Conclusion: LED therapy applied after physical training can improve functional performance of soccer players, evidenced by improvements of the jump height, muscle power and speed racing. / Contexto e Objetivos: Recentemente, a fototerapia por laser e LEDs de baixa potência vem sendo utilizada para aumentar o desempenho físico e acelerar a recuperação pós-exercício. Este estudo consiste em investigar os efeitos da terapia LED, na faixa do infravermelho (850 nm) e baixa potência (50 mW) sobre o desempenho físico de atletas de futebol após 06 semanas de treinamentos específicos desse esporte. Desenho do estudo/Materiais e métodos: Foi realizado um estudo clínico, randomizado, duplo cego e com placebo. Participaram do estudo 16 atletas de futebol com idade entre 14 e 16 anos de idade. Os atletas foram alocados randomicamente em 2 grupos iguais: (i) grupo treinamento associado à terapia LED (LEDT) e (ii) grupo treinamento associado à terapia LED placebo (Placebo). A terapia LED ou placebo foi aplicada sobre o quadríceps femoral, isquiotibiais e triceps sural imediatamente após os treinamentos, 2 vezes por semana, durante 6 semanas consecutivas, totalizando 12 sessões de terapia. Foi utilizado um dispositivo contendo um arranjo de 50 LEDs de baixa potência (850nm, 50 mW, 30 s sobre cada grupo muscular e energia de 75 J). O desempenho funcional doa atletas em salto vertical e em corridas de 10 e 35 metros foram realizados através da plataforma de salto e fotocélulas no período pré e pós-treinamento e terapia LED. Resultados: O grupo LEDT aumentou significativamente a altura (cm) do salto vertical (de 36,02±3,95 para 39,20±4,52; p<0,001) e a potência muscular (W) (de 382,62±31,82 para 417,62±31,19; p=0,003) nesse mesmo teste. A velocidade média (m/s) da corrida de 10m aumentou significativamente no grupo LEDT (de 5,94±0,35 para 6,13±0,45; p<0,001) assim como para a corrida de 35m (de 7,43±0,32 para 7,51±0,32; p=0,003). O grupo Placebo mostrou aumento significativo apenas para a altura do salto vertical (de 36,25±4,55 para 37,38±4,26; p=0,017). Conclusão: A fototerapia por LED de baixa potência aplicada após o treinamento físico pode aumentar o desempenho físico dos atletas de futebol, evidenciado pelo aumento da altura de salto, potencia muscular e velocidade de corrida.