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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
581

Hybrid-Lithography for the Master of Multi-ModeWaveguides NIL Stamp

Mistry, Akash, Nieweglowski, Krzysztof, Bock, Karlheinz 21 August 2024 (has links)
the presented work demonstrates the fabrication process of the master for nano-imprint lithography (NIL) stamp for multi-mode waveguide (MM-WG) with μ-mirror using hybrid-lithography, which includes a 2-photon-polymerization direct laser writing process (2PP-DLW) for μ-mirror surface and UV-photo lithography for MM-WGs. For the definition of the mirror surface at either end of waveguides in the master stamp, the 2PP-DLW process was used. It offers a lower surface roughness (< 0.1 λ) with fewer processing steps, alignment accuracy of ± 1 μm, prints fine and sharp contours, and relatively faster scanning for a specific material, which makes it the foremost technology over the traditional micro-mirror processes such as the dicing process, moving mask lithography, laser ablation, wet etching, and dry etching. For the fabrication of the waveguide core with rectangular cross-sections in the master stamp, UV mask exposure with SU-8 was used. It is a mass-production and low-cost technique. It gives a smooth structure with 90-degree sidewalls compared to other processes like dry etching, wet etching, mosquito method, and E-beam writing. We demonstrated the design and process of a master pattern with a density range from 0.04 to 0.2 to maintain equal pressure over the stamp in the NIL step for an almost uniform residual thickness layer.:Abstract Introduction Design of Experiments Experimental Results and Discussions Conclusion
582

Mobile Trions in Electrically Tunable 2D Hybrid Perovskites

Ziegler, Jonas D., Cho, Yeongsu, Terres, Sophia, Menahem, Matan, Taniguchi, Takashi, Watanabe, Kenji, Yaffe, Omer, Berkelbach, Timothy C., Chernikov, Alexey 27 November 2024 (has links)
2D hybrid perovskites are currently in the spotlight of material research for light-harvesting and -emitting applications. It remains extremely challenging, however, to externally control their optical response due to the difficulties of introducing electrical doping. Here, an approach of interfacing ultrathin sheets of perovskites with few-layer graphene and hexagonal boron nitride into gate-tunable, hybrid heterostructures, is demonstrated. It allows for bipolar, continuous tuning of light emission and absorption in 2D perovskites by electrically injecting carriers to densities as high as 1012 cm−2. This reveals the emergence of both negatively and positively charged excitons, or trions, with binding energies up to 46 meV, among the highest measured for 2D systems. Trions are shown to dominate light emission and propagate with mobilities reaching 200 cm2 V−1 s−1 at elevated temperatures. The findings introduce the physics of interacting mixtures of optical and electrical excitations to the broad family of 2D inorganic–organic nanostructures. The presented strategy to electrically control the optical response of 2D perovskites highlights it as a promising material platform toward electrically modulated light-emitters, externally guided charged exciton currents, and exciton transistors based on layered, hybrid semiconductors.
583

Ultraviolet and visible semiconductor lasers based on ZnO heterostructures

Kalusniak, Sascha 03 February 2014 (has links)
Im Rahmen dieser Arbeit wurden die optischen Eigenschaften von auf ZnO-basierenden Heterostrukturen untersucht. Besonderes Augenmerk lag hierbei auf ihrer Eignung als aktives Material in Laserdioden für den ultravioletten und sichtbaren Spektralbereich. Es wurde gezeigt, dass ZnO und seine ternären Mischkristalle ZnCdO und ZnMgO erstaunlich vielfältige Anwendungen ermöglichen. Mit diesem Materialsystem lässt sich sowohl ein sehr großer Spektralbereich für Lasertätigkeit abdecken als auch eine Vielzahl von Laseranordnungen realisieren. Im Detail wurde demonstriert, dass sich die Lasertätigkeit von ZnCdO/ZnO Quantengraben-Strukturen vom violetten bis in den grünen Spektralbereich verschieben lässt. Obwohl diese Strukturen starke interne elektrische Felder aufweisen, konnte optisch gepumpte Lasertätigkeit bei Zimmertemperatur bis zu einer Wellenlänge von 510 nm gezeigt werden. Die für die Lasertätigkeit nötige optische Rückkopplung wird durch makroskopische Defekte der Probe verursacht und die Proben fungieren somit als Zufallslaser. Die Herstellung von Mikroresonatoren ermöglichte die Untersuchung des Zusammenspiels von Fabry-Perot- und Zufalls-Rückkopplung. Die experimentellen und theoretischen Ergebnisse zeigen, dass der Schwellengewinn eines Zufallslasers in der Regel größer ist als der des Fabry-Perot-Lasers. Des Weiteren wurde gezeigt, dass hoch reflektierende Braggreflektoren für den ultravioletten und blau/grünen Spektralbereich aus ZnO- und ZnMgO-Schichten hergestellt werden können. Ferner wurden die teils unbekannten Brechungsindexverläufe der verwendeten ternären Materialen erarbeitet und Mikrokavitäten mit ZnO/ZnMgO Quantengraben Strukturen als aktive Schichten realisiert. An diesen Kavitäten konnte bei Temperaturen bis zu 150 K starke Kopplung zwischen Exzitonen und Photonen nachgewiesen werden. Bei Zimmertemperatur konnte vertikal-emittierende Lasertätigkeit im nahen ultravioletten Spektralbereich demonstriert werden. / In the framework of this thesis, the optical properties of ZnO-based heterostructures fabricated by molecular beam epitaxy have been investigated, particularly with regard to their suitability for semiconductor laser devices operating in the ultraviolet and visible spectral range. It turned out that ZnO and its ternary alloys ZnMgO and ZnCdO are extremely versatile. They allow to tune the laser emission in a wide spectral range as well as to realize various laser geometries. In detail, it was shown that the laser emission of ZnCdO/ZnO multiple quantum wells can cover a spectral range from violet to green wavelengths. Although these structures suffer from large built-in electric fields, room temperature laser action under optical pumping was demonstrated up to a wavelength of 510. The optical feedback for lasing is provided by growth imperfections on a macroscopic length scale turning these structures into random lasers. The fabrication of micro-resonators allowed to study the interplay between random and Fabry-Perot feedback. The experimental and theoretical analysis shows that random feedback generally requires a larger gain than under Fabry-Perot feedback. Further, this work demonstrates that ZnO- and ZnMgO-layers can be used to fabricate highly reflective distributed Bragg reflectors for applications in the ultraviolet and blue/green spectral range. The partly unknown dispersion curves of the index of refraction of the employed ternary alloys have been elaborated. This enabled the realization of all monolithic microcavities with ZnO/ZnMgO quantum wells as active zone. For temperatures below 150 K strong exciton-photon coupling is observed in such microcavities. At room temperature, vertical cavity surface emitting laser action in the near UV spectral range is demonstrated for appropriately designed microcavities.
584

White Top-Emitting OLEDs on Metal Substrates / Weiße top-emittierende OLEDs auf Metallsubstraten

Freitag, Patricia 19 July 2011 (has links) (PDF)
This work focusses on the development of top-emitting white organic light-emitting diodes (OLEDs), which can be fabricated on metal substrates. Bottom-emitting OLEDs have been studied intensively over the years and show promising perspectives for future commercial applications in general lighting. The development of top-emitting devices has fallen behind despite the opportunities to produce these devices also on low-cost opaque substrates. This is due to the challenges of top-light-emission concerning the achievement of a broad and well-balanced white emission spectrum in presence of a strong microcavity. The following work is a further step towards the detailed understanding and optimization of white top-emitting OLEDs. First, the available metal substrates and the deposited silver electrodes are examined microscopically to determine their surface characteristics and morphology in order to assess their applicability for thin-film organic stacks of OLEDs. The examination shows the suitability for untreated Alanod metal substrates, which display low surface roughness and almost no surface defects. For the deposited silver anodes, investigations via AFM show a strong influence of the deposition rate on the surface roughness. In the main part of the work top-emissive devices with both hybrid and all-phosphorescent architecture are investigated, in which three or four emitter materials are utilized to achieve maximum performance. The feasibility for top-emitting white OLEDs in first and second order devices is investigated via optical simulations, using the example of a three-color hybrid OLED. Here, the concept of a dielectric capping layer on top of the cathode is an essential criterion for broadband and nearly angle independent light emission. The main focus concerning the investigation of fabricated devices is the optimization of the organic stacks to achieve high efficiencies as well as excellent color quality of warm white emission. The optimization of the hybrid layer structure based on three emitter materials using a combined aluminum-silver anode mirror resulted in luminous efficacies up to 13.3 lm/W and 5.3 % external quantum efficiency. Optical analysis by means of simulation revealed a superior position concerning internal quantum efficiency compared to bottom-emitting devices with similar layer structure. The devices show an enhanced emission in forward direction compared to an ideal Lambertian emitter, which is highly preferred for lighting applications. The color quality - especially for devices based on a pure Al anode - is showing excellent color coordinates near the Planckian locus and color rending indices up to 77. The introduction of an additional yellow emitter material improves the luminous efficacy up to values of 16.1 lm/W and external quantum efficiencies of 5.9 %. With the choice of a all-phosphorescent approach, using orange-red, light blue and green emitter materials, luminous efficacies of 21.7 lm/W are realized with external quantum efficiencies of 8.5 %. Thereby, color coordinates of (x, y) = (0.41, 0.45) are achieved. Moreover, the application of different crystalline capping layers and alternative cathode materials aim at a scattering of light that further reduces the angular dependence of emission. Experiments with the crystallizing material BPhen and thin carbon nanotube films (CNT) are performed. Heated BPhen capping layer with a thickness of 250 nm show a lower color shift compared to the NPB reference capping layer. Using CNT films as cathode leads to a broadband white emission at a cavity thickness of 160 nm. However, due to very high driving voltages needed, the device shows low luminous efficacy. Finally, white top-emitting organic LEDs are successfully processed on metal substrates. A comparison of three and four color based hybrid devices reveal similar performance for the devices on glass and metal substrate. Only the devices on metal substrate show slightly higher leakaged currents. During repeated mechanical bending experiments with white devices deposited on 0.3 mm thin flexible Alanod substrates, bending radii up to 1.0 cm can be realized without device failure. / Diese Arbeit richtet ihren Schwerpunkt auf die Entwicklung von top-emittierenden weißen organischen Leuchtdioden (OLEDs), welche auch auf Metallsubstraten gefertigt werden können. Im Laufe der letzten Jahre wurden bottom-emittierende OLEDs sehr intensiv studiert, da sie vielversprechende Perspektiven für zukünftige kommerzielle Anwendungen in der Allgemeinbeleuchtung bieten. Trotz der Möglichkeit, OLEDs auch auf kostengünstigen lichtundurchlässigen Substraten fertigen zu können, blieb die Entwicklung von top-emittierenden Bauteilen dabei allerdings zurück. Dies läßt sich auf die enormen Herausforderungen von top-emittierenden OLEDs zurückführen, ein breites und ausgeglichenes weißes Abstrahlungsspektrum in Gegenwart einer Mikrokavität zu generieren. Die folgende Arbeit liefert einen Beitrag zum detaillierten Verständnis und der Optimierung von weißen top-emittierenden OLEDs. Zunächst werden die verfügbaren Metallsubstrate und abgeschiedenen Silberelektroden auf ihre Oberflächeneigenschaften und Morphologie mikroskopisch untersucht, um damit ihre Verwendbarkeit für organische Dünnfilmstrukturen in OLEDs einzuschätzen. Die Untersuchung zeigt eine Eignung von unbehandelten Alanod Metallsubstraten auf, welche eine niedrige Oberflächenrauigkeit und fast keine Oberflächendefekte besitzen. Bei den abgeschiedenen Silberelektroden zeigen Untersuchungen mit dem Rasterkraftmikroskop eine starke Beeinflussung der Oberflächenrauigkeit durch die Aufdampfrate. Im Hauptteil der Arbeit werden top-emittierende Dioden mit hybrid und voll-phosphoreszenter Architektur untersucht, in welcher drei oder vier Emittermaterialien verwendet werden, um eine optimale Leistungscharakteristik zu erreichen. Die Realisierbarkeit von top-emittierenden weißen OLEDs in Dioden erster und zweiter Ordnung wird durch optische Simulation am Beispiel einer dreifarb-OLED mit Hybridstruktur ermittelt. Dabei ist das Konzept der dielektrischen Deckschicht - aufgebracht auf die Kathode - ein essenzielles Kriterium für breitbandige und annähernd winkelunabhängige Lichtemission. Der Schwerpunkt im Hinblick auf die Untersuchung von hergestellten Dioden liegt in der Optimierung der organischen Schichtstrukturen, um hohe Effizienzen sowie exzellente warmweiße Farbqualität zu erreichen. Im Rahmen der Optimierung von hybriden Schichtstrukturen basierend auf drei Emittermaterialien resultiert die Verwendung eines kombinierten Aluminium-Silber Anodenspiegels in einer Lichtausbeute von 13.3 lm/W und einer externen Quanteneffizienz von 5.3 %.Eine optische Analyse mit Hilfe von Simulationen zeigt eine überlegene Stellung hinsichtlich der internen Quanteneffizient verglichen mit bottom-emittierenden Dioden ähnlicher Schichtstruktur. Die Dioden zeigen eine verstärkte vorwärts gerichtete Emission im Vergleich zu einem idealen Lambertschen Emitter, welche in hohem Maße für Beleuchtungsanwendungen erwünscht ist. Es kann eine ausgezeichnete Farbqualität erreicht werden - insbesondere für Dioden basierend auf einer reinen Aluminiumanode - mit Farbkoordinaten nahe der Planckschen Strahlungskurve und Farbwiedergabeindizes bis zu 77. Die weitere Einführung eines zusätzlichen gelben Emittermaterials verbessert die Lichtausbeute auf Werte von 16.1 lm/W und die externe Quanteneffizient auf 5.9 %. Mit der Wahl eines voll-phosphoreszenten Ansatzes unter der Verwendung eines orange-roten, hellblauen und grünen Emittermaterials werden Lichtausbeuten von 21.7 lm/W und externe Quanteneffizienten von 8.5 % erzielt. Damit werden Farbkoordinaten von (x, y) = (0.41, 0.45) erreicht. Darüberhinaus zielt die Verwendung von verschiedenen kristallinen Deckschichten und alternativen Kathodenmaterialien auf eine Streuung des ausgekoppelten Lichts ab, was die Winkelabhängigkeit der Emission vermindern soll. Experimente mit dem kristallisierenden Material BPhen und dünnen Filmen aus Kohlenstoffnanoröhren werden dabei durchgeführt. Geheizte BPhen Deckschichten mit einer Schichtdicke von 250 nm zeigen eine geringere Farbverschiebung verglichen mit einer NPB Referenzdeckschicht. Die Verwendung von Kohlenstoffnanoröhren als Kathode führt zu einer breitbandigen weißen Emission bei einer Kavitätsschichtdicke von 160 nm. Schließlich werden weiße top-emittierende organische Leuchtdioden erfolgreich auf Metallsubstraten prozessiert. Ein Vergleich von drei- und vierfarb-basierten hybriden Bauteilen zeigt ähnliche Leistungsmerkmale für Dioden auf Glas- und Metallsubstraten. Während wiederholten mechanischen Biegeexperimenten mit weißen Dioden auf 0.3 mm dicken flexiblen Alanodsubstraten können Biegeradien bis zu 1.0 cm ohne Bauteilausfall realisiert werden.
585

Studium optoelektrických vlastností tenkých vrstev organických polovodičů / Study of optoelectrical properties of organic semiconductor thin film layers

Pospíšil, Jan January 2012 (has links)
The thesis is focused on the study of electric and dielectric properties of thin film organic materials that can be used as an active layer of photovoltaic cells. Primarily were studied the properties of the layers on the glass substrates, which consist of a thin active layer of phthalocyanines. On the samples were first measured current-voltage characteristics (in the dark and during the exposure) and the basic parameters of the photovoltaic conversion were determined. Finally were measured frequency dependencies (impedance spectra, in the dark and during the exposure) and the parameters of a model of the structure with organic semiconductor were determined. The obtained results will be used to optimize the properties of photovoltaic cells.
586

Single- and entangled-photon emission from strain tunable quantum dots devices

Zhang, Jiaxiang 21 August 2015 (has links)
On demand single-photon and entangled-photon sources are key building-blocks for many proposed photonic quantum technologies. For practical device applications, epitaxially grown quantum dots (QDs) are of increasing importance due to their bright photon emission with sharp line width. Particularly, they are solid-state systems and can be easily embedded within a light-emitting diode (LED) to achieve electrically driven sources. Therefore, one would expect a full-fledged optoelectronic quantum network that is running on macroscopically separated, QD-based single- and entangled-photon devices. An all-electrically operated wavelength-tunable on demand single-photon source (SPS) is demonstrated first. The device consists of a LED in the form of self-assembled InGaAs QDs containing nanomembrane integrated onto a piezoelectric crystal. Triggered single photons are generated via injection of ultra-short electrical pulses into the diode, while their energy can be precisely tuned over a broad range of about 4.8 meV by varying the voltage applied to the piezoelectric crystal. High speed operation of this single-photon emitting diode up to 0.8 GHz is demonstrated. In the second part of this thesis, a fast strain-tunable entangled-light-emitting diode (ELED) is demonstrated. It has been shown that the fine structure splitting of the exciton can be effectively overcome by employing a specific anisotropic strain field. By injecting ultra-fast electrical pulses to the diode, electrically triggered entangled-photon emission with high degree of entanglement is successfully realized. A statistical investigation reveals that more than 30% of the QDs in the strain-tunable quantum LED emit polarization-entangled photon-pairs with entanglement-fidelities up to f+ = 0.83(5). Driven at the highest operation speed ever reported so far (400 MHz), the strain-tunable quantum LED emerges as unique devices for high-data rate entangled-photon applications. In the end of this thesis, on demand and wavelength-tunable LH single-photon emission from strain engineered GaAs QDs is demonstrated. Fourier-transform spectroscopy is performed, from which the coherence time of the LH single-photon emission is studied. It is envisioned that this new type of LH exciton-based SPS can be applied to realize an all-semiconductor based quantum interface in the foreseeable distributed quantum networks.
587

Free space optical interconnects for speckled computing

Reardon, Christopher P. January 2009 (has links)
The aim of this project was to produce an integrate-able free space optical transceiver for Specks. Specks are tiny computing units that together can form a powerful network called a SpeckNet. The SpeckNet platform is developed by the SpeckNet consortium, which consists of five Scottish Universities and combines computer science, electrical engineering and digital signal processing groups. The principal goal of creating an optical transceiver was achieved by integrating in-house fabricated VCSELs (with lasing thresholds below 400 uA) and custom designed detectors on the SpeckNet platform. The transceiver has a very low power consumption (approximately 100 uW), which removes the need for synchronous communication through the SpeckNet thus making the network more efficient. I describe both static and dynamic beam control techniques. For static control, I used micro-lenses. I fabricated the lenses by greyscale electron beam lithography and integrated them directly on VCSEL arrays. I achieved a steering angle of 10 degrees with this design. I also looked at integrated gratings etched straight into a VCSEL and observed beam steering with an efficiency of 60% For dynamic control, I implemented a liquid crystal (LC) design. I built a LC cell with 30 individually controlled pixels, but I only achieved a steering angle of 1 degree. Furthermore, I investigated two different techniques for achieving beam steering by interference, using coupled VCSELs (a phased array approach). Firstly, using photonic crystals etched into the surface of the VCSEL, I built coupled laser cavities. Secondly, I designed and built bow-tie type VCSELs that were optically coupled but electrically isolated. These designs work by differential current injection causing an interference effect in the VCSELs far field. This technique is the first stepping stone towards realising a phased optical array. Finally, I considered signal detection. Using the same VCSEL material, I built a resonant-cavity detector. This detector had a better background rejection ratio than commercially available silicon devices.
588

Proposta e avaliação de um sistema complementar de posicionamento baseado em comunicação por luz visível aplicado a sistemas inteligentes de transporte. / Proposal and evoluation of a complementary positioning system based on visible light communication applied to transport system.

Maré, Renata Maria 27 November 2017 (has links)
O uso crescente de dispositivos móveis e o advento da Internet das Coisas têm demandado esforços para prover alternativas de comunicação sem fio. A utilização de sistemas óticos para a transmissão de dados apresenta-se como uma tecnologia promissora e complementar à comunicação por radiofrequência, especialmente devido aos desenvolvimentos consideráveis na tecnologia de iluminação por estado sólido e sua adoção em vários domínios. Os diodos de emissão de luz podem ser utilizados na promoção de comunicação por luz visível em ambientes internos e externos. Nos ambientes externos há inúmeras oportunidades a serem exploradas no que concerne aos Sistemas Inteligentes de Transporte, visto que os diodos de emissão de luz têm sido utilizados em luminárias públicas, semáforos e veículos. Esta pesquisa propôs o desenvolvimento e a avaliação de um sistema de comunicação por luz visível entre elementos da infraestrutura urbana e veículos, mais especificamente, luminárias públicas baseadas em diodos de emissão de luz e o modal de transporte público representado pelos ônibus que circulam em faixas exclusivas. A metodologia foi composta por simulação computacional e pela construção de um protótipo para auxiliar na validação das soluções propostas. O sistema complementar de comunicação sem fio por meio da luz proposto fornece pode fornecer subsídios à determinação do posicionamento preciso dos ônibus, suprindo as deficiências do sistema GPS em locais menos favoráveis à recepção de seus sinais em uma cidade. Essas informações auxiliam os usuários e os gestores do transporte público, atendendo alguns domínios de serviço em Sistemas Inteligentes de Transporte, de acordo com a norma ISO 14813. Os resultados obtidos nos testes com o protótipo, bem como, aqueles observados na simulação, comprovaram a viabilidade do sistema proposto, com o estabelecimento da comunicação entre luminária e ônibus, inclusive quando trafegando a 60 km/h. / The increasing use of mobile devices and the advent of the Internet of Things have called for efforts to provide alternatives for wireless communication. The use of optical systems for data transmission is a promising and complementary technology to radiofrequency communication, especially due to the considerable developments in solidstate lighting technology and its adoption in various domains. Light-emitting diodes can be used to promote visible light communication in indoor and outdoor environments. In outdoor environments there are numerous opportunities to be explored with regard to Intelligent Transport Systems, since light-emitting diodes have been used in public luminaires, traffic lights and vehicles. This research proposed the development and evaluation of a visible light communication system between elements of the urban infrastructure and vehicles, more specifically, public luminaires based on light-emitting diodes and the mode of public transport represented by buses that circulate in exclusive lanes. The methodology was composed by computational simulation and the construction of a prototype, to assist in the validation of the proposed solutions. The proposed complementary wireless communication system through light provides subsidies to determine the precise positioning of buses, supplying deficiencies of the GPS system in places less favorable to the reception of their signals in a city. This information helps the users and the managers of the public transport, attending some service domains in Intelligent Transport Systems, according to the ISO 14813 standard. The results obtained in the tests with the prototype, as well as those observed in the simulation, proved the feasibility of the proposed system, with the establishment of communication between luminaire and bus, even when traveling at 60 km/h.
589

Estudo de dispositivos orgânicos emissores de luz empregando complexos de terras raras e de metais de transição. / Study of organic light-emitting devices using rare earth and transition metals complexes.

Santos, Gerson dos 21 August 2008 (has links)
Neste trabalho foram projetados, fabricados e caracterizados funcionalmente dispositivos eletroluminescentes empregando complexos de Terras Raras (TR) e de Metais de Transição (MT) tanto como em filmes finos termicamente evaporados quanto formados através da técnica de spin-coating. O estudo foi iniciado com os complexos de TRs (especificamente o complexo de Európio e de Térbio) com filmes termicamente evaporados, com vistas à análise da eficiência externa dos dispositivos em função do ligante principal (CL). Desta análise observou-se que a particular estrutura química do CL resulta em diferenças perceptíveis ao nível da caracterização eletro-óptica (de 0,73x10-3 [BTA] para 1,05x10-3 [DBM]). Dando seqüência à análise de dispositivo com camada emissiva termicamente evaporada, foi realizada a análise do complexo de Térbio com dois tipos de ligante neutro (NL). Com base nos resultados obtidos, neste foco do estudo, observou-se que a configuração estrutural do NL implica em diferenças na eficiência externa (de 0,8x10-3 [PHEN] para 4,1x10- 3 [BIPY]) e no comprimento de onda dominante emitido (de 542 nm [BIPY] para 563 [PHEN]). Ainda explorando os complexos de TRs, foram estudados dispositivos empregando estes dispersos em um polímero com função de matriz, neste caso o polivinilcarbazol (PVK), em filmes formados por spin-coating, os quais apresentaram maior eficiência (de 0,72x10-3 [evaporado] para 1,24x10-3 [spincoating]) externa em comparação aos termicamente evaporados. Ainda nesta linha de estudo foi explorada uma nova estrutura de dispositivo empregando filmes automontados, cujos resultados apresentaram uma melhor eficiência externa para três bicamadas de PAni/PEDOT:PSS. Na seqüência, foram empregados os complexos de MT, especificamente de Rutênio e de Rênio, em filmes finos formados por spincoating. Com o primeiro destes, foi avaliada a conseqüência da variação do seu ligante, seus processos de transporte de portadores de carga e os fenômenos relacionados com sua luminescência. Já com o segundo, que foi disperso em PVK em diversas concentrações, foi feita a análise da eficiência externa com a mesma idéia adotada com o complexo de Európio, cujo estudo revelou uma eficiente transferência de energia, descrita pelo mecanismo de Transferência de Carga Metal- Ligante (3MLCT). / This work presents the study of the Rare Earth (RE) and Transition Metals (TM) complexes, as emissive layers of Organic Light-Emitting Devices (OLEDs) designed, built and electro-optically characterized. The thin films were thermally evaporated or spin-coated. This research started with the study of Europium complex changing its central ligand (CL), which showed that its electrical response exhibits external efficiency differences (from 0.73x10-3 [BTA] to 1.05x10-3 [DBM]). It was observed that the particular chemical structure of the CL results in significant differences as seen in the electro-optical characterization. Giving continuity to the thermally evaporated device characterization, an analysis was done with the Terbium complexes with two different neutral ligands (NL). It was noticed, in this work, that an NL change in Terbium complex imply in changes in external efficiency (from 0.8x10-3 [PHEN] to 4.1x10-3 [BIPY]) and in the emitted dominant wavelength (from 542 nm [BIPY] to 563 nm [PHEN]). Following the study using RE complex, we used it as a dye dispersed in polyvinylcarbazole (PVK) matrix, in a spin-coated deposited thin-film, which results showed a better external efficiency in comparison with thermally evaporated thin-films (from 0.72x10-3 [thermal evaporation] to 1.24x10-3 [spin-coating]). Besides, it was studied a new structure of electroluminescent device with thin-film Self-Assembled deposition, which results showed a better external efficiency for three bilayers of PAni/PEDOT:PSS. In the sequence, TM complexes, namely Ruthenium and Rhenium, were studied using spincoated thin-films. With the first of them, the implications of different ligands (bipyridyne and phenanthroline) were evaluated aiming the charge carrier transport and the luminescence related phenomena. The Rhenium complex was dispersed as a dye in the PVK, using the same approach as that used to study the Europium complex showing a very efficient energy transfer process, described in literature as the Metal-Ligand Charge Transfer (3MLCT) mechanism.
590

Design, synthesis and supramolecular architectures of new heterocyclic compounds with potential applications in material chemistry and photovoltaic conversion / Design, synthèse et architectures supramoléculaires de nouveaux composés hétérocycliques avec des applications potentielles en chimie des matériaux et conversion photovoltaïque

Diac, Andreea Petronela 21 October 2015 (has links)
La thèse intitulée «Design, Synthesis and SupramolecularArchitectures of New Heterocyclic Compounds with PotentialApplications in Material Chemistry and Photovoltaic Conversion” eststructurée en cinq chapitres traitant de nouveaux: a)cyclopenta[c]pyrannes hétérocyclique; b)des propriétés fluorescentes; d) potentiels dispositifs de l'électroniquemoléculaire; d) donneurs moléculaires pour les photovoltaïquesorganiques et e) carbon‘quantum’dots électroluminescents.Le premier chapitre présente une étude des dérivéspseudoazulenique ayant une unité cyclopenta[porte sur leur synthèse, l'analyse structurale et leur comportement dansdes réactions de substitution électrophile pour obtenir des composésayant des propriétés fluorescentes.Le deuxième chapitre présentediastéréoisomères et l'étude de propriétés de fluorescencedérivés d’indenopyrone.Le troisième chapitre décrit la synthèse des nouvellesarchitectures basées sur l’unité cyclopenta[être modifiés structurellement par l'influence d'un stimulus chimiqueou électrochimique afin d'élaborer des potentiels dispositifs del'électronique moléculaire.Dans le quatrième chapitre, la synthèsedes propriétés électroniques des nouvelles molécucellules solaires organiques (OSC) ontLe cinquième et dernier chapitre décrit la passivation desdéfauts de surface des nanoparticules de carbone avec desmolécules organiques ou des polymères pour obtenir desnanoparticules de carbone photoluminescentse surnommé ‘quantum dots. / The thesis entitled “Design, Synthesis and SupramolecularArchitectures of New Heterocyclic Compounds with PotentialApplications in Material Chemistry and Photovoltaic Conversion” isstructured into five chapters concerning new: a) heterocycliccyclopenta[c]pyrans; b) indenopyrone derivatives with fluorescentproperties; c) potential devices of molecular electronics; d)donors for organic photovoltaics and e) electroluminescent carbon‘quantum’ dots.The first chapter presents a study of pseudoazulenederivatives having a cyclopenta[c]pyran unit. The survey comprises thesynthesis, structural analysis and reactivity towards electrophilicsubstitution in order to obtain fluorescent compounds.The second chapter deals with the separation odiastereoisomers and the study of fluorescent propertiesindenopyrone derivatives.The third chapter describes the synthesis of newarchitectures based on cyclopenta[c]pyran unit that can be structurallymodified by the influence of a chemical or electrochemical stimulus inorder to work as potential devices in molecular electronics.In the fourth chapter, the synthesis andelectronic properties of new molecular donors for organic solar cellswas described.The fifth and last chapter outlines the passivation of surfacedefects on carbon nanoparticles using small organic molecules orpolymers in order to obtain photoluminescent carbon nanoparticlesdubbed as carbon‘quantum’dots.

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