Ce travail de thèse porte sur la synthèse et la caractérisation physico-chimique de métallopolymères conjugués des éléments f en but d'utiliser ces matériaux comme composants actifs de diodes électroluminescentes. En effet, les ions lanthanides possèdent des propriétés d'émission intéressantes dans le cadre de nos applications. La chaine polymère permet quant à elle l'introduction de groupements transporteurs de charges. Ces matériaux devraient donc réunir les caractéristiques requises (transport des charges et émission) pour être utilisés dans des PLEDs (Polymer Light-Emitting Diodes), lesquelles emploient pour leur fabrication des techniques de dépôts en solution. Les PLEDs présentent l'intérêt d'avoir une structure simplifiée par rapport aux OLEDs (Organic Light-Emitting Diodes) qui sont construites par juxtaposition de couches successives de petites molécules évaporées sous vide.La synthèse de trois séries de polymères conjugués a été réalisée. La réaction de polymérisation utilisée s'effectue selon un couplage de Suzuki-Miyaura entre des motifs fluorènes et des monomères porteurs de groupements carbazoles et/ou benzimidazoles permettant de coordiner l'ion lanthanide. Plusieurs métallopolymères ont également été isolés. Les composés synthétisés ont été caractérisés par analyse élémentaire, RMN et chromatographie par exclusion stérique. Des études de photoluminescence sur ces composés en présence ou non d'ions lanthanides luminescents ont été effectuées. Enfin, les polymères et métallopolymères ont été utilisés dans la conception de diodes électroluminescentes.

Organic Light-Emitting Devices (OLEDs) have reached industrial maturity in display technology, since OLEDs provide salient advantages such as high brightness, fast response, wide viewing angle, mechanical flexibility, and low cost manufacturing. Due to the ability of electroluminescence (EL) from triplet excited states as well as singlet excited states, phosphorescent OLEDs (PHOLEDs) have a potential to achieve 100% internal quantum efficiency. Therefore, PHOLEDs can offer a competitive external quantum efficiency. However, the operational stability of PHOLEDs is relatively poor. Several mechanisms have been proposed to address the chemical and physical phenomena associated with intrinsic degradation of PHOLEDs, nevertheless, the reasons behind voltage rise and luminance loss accompanying PHOLEDs long term operation are not yet well understood. The state of the art p-i-n PHOLEDs offer relatively high efficiency and low efficiency roll-off. However, this technology is characterized by structure complexity. Therefore, much of the current research on PHOLEDs focuses on the development of the simplest possible and most easily processed architecture that can deliver the optimal combination of device properties. Simplified PHOLEDs, utilizing one material for both hole transport and emitter host, can be a good candidate for replacement of p-i-n technology. Simplified PHOLEDs offer higher efficiency than the p-i-n PHOLEDs , yet, their EL stability is found to be poor. In this thesis, the role of the ITO/organic interface on simplified PHOLEDs efficiency will be investigated. Furthermore, possible degradation mechanisms at the ITO/organic interface will be explored. Moreover, we will correlate degradation at the ITO/organic interface to PHOLEDs operational stability. Eventually, organic layers modifications including but not limited to emissive layer (EML) will be examined. By studying the indium tin oxide (ITO)/organic interface in simplified PHOLEDs, it was found that this interface is critical to PHOLEDs performance. The study shows that, this interface is critical to the PHOLED overall stability and is considered as one of the limiting factors of the long term operational stability of simplified PHOLEDs. The effect of optical excitation on the ITO/organic interface stability in hole-only devices was investigated. It was found that the ITO/organic interface is susceptible to exciton-induced degradation. This degradation affects the device stability severely compared to current-induced degradation. The exciton-induced degradation can be prevented by doping the hole transport layer (HTL), at the interface with an exciton quencher layer or by blocking the electrons from leaking to the ITO/organic interface that may further recombine with holes to form excitons. Further studies showed that upon combining both electrical stress and optical excitation, the device degradation is even more pronounced which is most likely due to interactions between charges and excitons. By using exciton life-time measurements, a new role of molybdenum trioxide (MoO3) in the electrical stability of PHOLEDs, as an exciton quencher layer, is introduced. Delayed EL (DEL) measurements showed that the simplified PHOLEDs are susceptible to triplet-triplet annihilation (TTA) and triplet-polaron quenching (TPQ) which might affect the operational stability of simplified PHOLEDs. Finally, EML modifications showed that the recombination zone of simplified PHOLEDs is located near the HTL/EML interface.

abstract: Optical Fibers coupled to laser light sources, and Light Emitting Diodes are the two classes of technologies used for optogenetic experiments. Arizona State University's Flexible Display Center fabricates novel flexible Organic Light Emitting Diodes(OLEDs). These OLEDs have the capability of being monolithically fabricated over flexible, transparent plastic substrates and having power efficient ways of addressing high density arrays of LEDs. This thesis critically evaluates the technology by identifying the key advantages, current limitations and experimentally assessing the technology in in-vivo and in-vitro animal models. For in-vivo testing, the emitted light from a flat OLED panel was directly used to stimulate the neo-cortex in the M1 region of transgenic mice expressing ChR2 (B6.Cg-Tg (Thy1-ChR2/EYFP) 9Gfng/J). An alternative stimulation paradigm using a collimating optical system coupled with an optical fiber was used for stimulating neurons in layer 5 of the motor cortex in the same transgenic mice. EMG activity was recorded from the contralateral vastus lateralis muscles. In vitro testing of the OLEDs was done in primary cortical neurons in culture transfected with blue light sensitive ChR2. The neurons were cultured on a microelectrode array for taking neuronal recordings. / Dissertation/Thesis / ICMS response in front and hind limb / Optogenetic response using iLEDs and OLEDs / iLED vs iLED coupled to optical fiber response / Masters Thesis Bioengineering 2015

Research efforts towards realizing electrochemically-stable organic semiconductors have been a focus of the organic light-emitting diode (OLED) industry for decades. This is especially true for the discovery of blue-light emitting materials and compounds with optical band gaps greater than 2.8 eV as these materials undergo rapid degradation resulting in poor operational lifetimes. Benzo[1,2-d:4,5-d']bis(oxazole)s and benzo[1,2-d:4,5-d']bis(oxazole)s (BBOs) are useful building blocks that generate highly fluorescent materials with robust thermal and photo-oxidative stabilities and optical band gaps >2.8 eV. Previously, the Jeffries-EL group has synthesized and studied polymeric BBO systems for OLED application, which achieved sky-blue electroluminescence (EL) with external quantum efficiencies (EQEs) of approximately 1.1 %. However, these systems are plagued with broad electroluminescence due to their polydispersity and have yet to achieve power efficiencies >10 lm/W. Small molecule BBO-based emitters (SM-BBOs) are advantageous due to their discrete size, uniform pi-electron delocalization, and high purity. To date, SM-BBOs have realized deep blue EL with good color purity and EQEs approaching 3%. However, the number of possible structural variants are vast, but known examples of these systems are limited, thus more work is required to increase our understanding of these systems to develop SM-BBOs-based OLEDs with higher efficiencies for commercial utility. Herein, several classes of SM-BBOs bearing various aryl substituents are computationally and experimentally studied to understand fundamental optical and electronic properties. This data is used to determine the structure-property relationships between SM-BBO systems and to design functional microelectronic OLEDs. The collected experimental data is used by our computational teams to improve our predictive strategies and refine synthetic efforts. As such, several SM-BBOs were achieved which produced near-UV and deep-blue EL while combinations of these products were used to obtain the first prototype white OLEDs with temperature tunability using SM-BBO emissive materials. / 2022-09-07T00:00:00Z

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No description available.

Organic electronic devices like organic solar cells and organic light-emitting diodes quickly degrade in ambient conditions if left unprotected. High susceptibility to moisture necessitates their encapsulation. The maximum water ingress acceptable to achieve reasonable lifetimes ranges several orders of magnitudes below industrial flexible barrier solutions. In this work, an electrical Ca-Test is used to optimize and investigate moisture barriers towards their application in device encapsulation. Aside from substantial improvement of the measurement system, atomic layer deposited, sputtered, and thermally evaporated barriers are screened and their water vapor transmission rates measured down to 2*10^(-5) g(H2O)/(m²*d) at 38 °C and 90% RH. Completely new encapsulation techniques are presented using novel molecular layer deposition interlayers or lamination of independently processed barriers. This way, simple Al layers become high-end moisture barriers. Furthermore, different single layer barriers are exposed to a wide variety of climates. An in-depth analysis of water permeation mechanics reveals sorption governed by Henry's law as well as dominance of interface diffusion below the barrier at late test stages. Investigated moisture barriers are applied to organic light-emitting diodes as well as solar cells and great improvements of lifetimes are observed. In addition, significant improvements in stability towards water ingress are witnessed upon the integration of adhesion layers at the cathode interface. Lastly, the great potential and applicability of this technology is showcased by the production and aging of fully flexible, highly efficient, stable organic solar cells. / Organische Elektronik-Bauteile wie organische Solarzellen und organische Leuchtdioden degradieren in kürzester Zeit, wenn sie ungeschützt feuchter Luft ausgesetzt sind. Ihre starke Anfälligkeit gegenüber Wasserdampf macht ihre Verkapselung notwendig. Der maximale Wassereintritt, der für sinnvolle Lebensdauern noch zulässig erscheint, liegt jedoch noch mehrere Größenordnungen unter dem, was mit existierenden Technologien erreicht werden kann. In der vorliegenden Arbeit wird ein elektrischer Kalzium-Korrosionstest benutzt, um Barrieresysteme auf ihre Anwendbarkeit als Verkapselung organischer Bauelemente hin zu untersuchen und zu optimieren. Abgesehen von signifikanten Verbesserungen am Messsystem werden Wasserdampfbarrieren aus Atomlagenabscheidungs-, Kathodenzerstäubungs- und Verdampfungsprozessen vermessen. Dabei werden außerordentlich niedrige Wasserdampfdurchtrittsraten von nur 2*10^(-5) g(H2O)/(m²*d) in einem Alterungsklima von 38 °C und 90% relativer Feuchte verzeichnet. Vollkommen neue Verkapselungstechniken werden realisiert, wie etwa die Integration von Zwischenschichten durch Molekularlagenabscheidung oder die Lamination zweier Barrieren, die unabhängig voneinander prozessiert werden. Dieser Prozess verwandelt einfache Al Schichten in qualitativ hochwertige Wasserdampfbarrieren. Des Weiteren werden verschiedene Einzelschicht-Barrieren einer breiten Klimavariation ausgesetzt. Dies ermöglicht die genaue Analyse der Permeationsmechanismen des Wassers. Es wird gezeigt, dass Sorption hier dem Henry'sche Gesetz folgt. Diffusion entlang der Grenzfläche unterhalb der Barriere dominiert die Permeation zu späten Testzeiten. Die untersuchten Wasserdampfbarrieren werden an organischen Leuchtdioden und Solarzellen erprobt und zeigen große Verbesserungen bezüglich ihrer Lebensdauern. Darüber hinaus zeigt sich eine stark verbesserte Resistenz gegenüber Wassereintritt, wenn eine zusätzliche Adhäsionsschicht unter der Kathodengrenzfläche integriert wird. Letztendlich zeigt sich das große Potential und die Anwendbarkeit der Ergebnisse in der hohen Effizienz und langen Lebensdauer vollflexibler, verkapselter organischer Solarzellen.

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.

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.

[pt] Nesta dissertação foram estudadas as propriedades ópticas, eletroquímicas, elétricas e morfológicas de novos compostos fluorescentes para o desenvolvimento de OLEDs. Para isto, foram estudadas algumas sondas moleculares fluorescentes utilizadas na área biomédica como agentes antitumorais e marcadores ópticos fluorescentes: a) N,N - diisonicotinoil-2-hidroxi-5 metilisoftaldeído diidrazona (DMD); b) 2-(5 -isotiocianato-2 -hidroxifenil)benzoxazol, (5ONCS); c) 1,1 -dipireno (DIPI) e d) 7,7 -terc-butil-1,1- dipireno (TDIPI). Todos estes compostos foram sintetizados por Grupos de pesquisa brasileiros e depositados termicamente em forma de filmes finos no nosso Laboratório. No decorrer do estudo de fabricação dos OLEDs, os dispositivos bicamada baseados no DMD e no 5ONCS se mostraram pouco eficientes devido principalmente à baixa condutividade do DMD e à elevada rugosidade da camada de 5ONCS. A solução destes problemas foi encontrada na técnica de codeposição, que consiste na evaporação simultânea de uma matriz orgânica e de um dopante (DMD ou 5ONCS) numa única camada. Desta forma, foi possível alcançar um aumento da mobilidade das cargas nas camadas co-depositadas alem de favorecer a transferência de energia da matriz para o dopante. Os OLEDs fabricados nestas condições permitiram observar, pela primeira vez, a eletroluminescência dos compostos DMD e 5ONCS. Já os OLEDs baseados nas moléculas DIPI e TDIPI apresentaram eletroluminescência sem a necessidade da co-deposição. Em particular, no caso do OLED baseado no TDIPI foi possível alcançar uma luminância de 1430 cd/m2 com uma eficiência de 2,65 porcento a 1mA. Os resultados deste trabalho evidenciam a potencialidade do uso destes materiais para a fabricação de OLEDs para aplicações na área de iluminação. / [en] In this study the optical, electrochemical, electrical and morphological properties of new fluorescent compounds were studied in order to develop OLEDs based upon these materials. For this purpose some fluorescent molecular probes used in the biomedical field as antitumor agents and fluorescent optical probes were studied: a) N,N diisonicotinoyl-2-hydroxy-5-methylisophthalaldehyde dihydrazone (DMD ), b) 2 - (5 -isothiocyanato -2-hydroxyphenyl) benzoxazole ( 5ONCS ), c) 1,1 - dipyrene (DIPI) and d) 7,7 -tertbutyl- 1,1-dipyrene (TDIPI ). All these compounds were synthesized by Brazilian research groups and then thermally deposited as thin films in our Laboratory. During the study for the fabrication of OLEDs, bilayer devices based on DMD and 5ONCS proved to have low efficiency mainly due to the low conductivity of the DMD and the high roughness of the 5ONCS layer. The solution of these problems was found in the codeposition technique, which consists in the simultaneous evaporation of an organic matrix (host) and a dopant (guest) (5ONCS or DMD) in a single layer. Thus, it was possible to achieve an increase in the charge mobility in the co-deposited layers as well as energy transfer from the guest to the host. The OLEDs fabricated in these conditions allowed the observation, for the first time, of the electroluminescence of DMD and 5ONCS. On the other hand, the DIPI and TDIPI based OLEDs presented good electroluminescence without the need for co-deposition. In particular, in the case of the TDIPI it was possible to achieve a luminance of 1430 cd/m2 with an efficiency of 2.65 percent at 1 mA. The results of this work showed the potential of these materials for the fabrication of OLEDs for lighting applications.