The efficiency of organic light-emitting diodes (OLEDs) typically decreases with increasing current density. This so-called roll-off impedes the market entry of OLEDs in high-brightness applications such as general lighting. One of the most important processes causing roll-off is exciton annihilation, which evolves upon high exciton densities. This mechanism is especially pronounced in phosphorescent molecules due to their long triplet lifetime. In order to reduce the roll-off in phosphorescent OLEDs, this thesis focusses on decreasing the local exciton density by modifying the exciton lifetime, the spatial exciton distribution, and the tendency of emitters to form aggregates. The obtained results lead to a deeper understanding of efficiency roll-off and help sustaining the OLED efficiency at high brightness. The emitter lifetime can be influenced by the optical environment around the emitting dipoles through the Purcell effect. In order to study this effect, the distance between emitter and metal cathode is varied for two different OLED stacks. A strong influence of emitter position and orientation on roll-off is observed and explained by modelling the data with triplet-triplet annihilation theory. Furthermore, design principles for optimal high-brightness performance are established by simulating the roll-off as a function of emitter-cathode distance, emissive dipole orientation, and radiative efficiency. Next, a method is developed that allows extracting the spatial exciton distribution. Therefore, a thin sensing layer that locally quenches excitons is introduced into the emission layer at varying positions. The resulting quenching profile is then fitted using a comprehensive theory based on the diffusion equation, which renders the exciton distribution and diffusion length with nanometer resolution. This method is applied to an emission layer comprising an ambipolar host material. Contrary to expectations which suggest that ambipolar materials exhibit broad exciton formation, a narrow emission zone close to the electron transport layer is found. Additional explorations of structures that might broaden the emission zone point to a narrow emission zone in double emission layers and broader exciton formation in mixed emission layers. Previous investigations revealed a strong correlation between emitter aggregation and molecular dipole moment of the emitter. Within this thesis, the range of studied emitters is significantly extended. It is shown that homoleptic emitters show a stronger tendency to form aggregates than heteroleptic compounds. This is probably not only related to their higher dipole-dipole potential, but also to the molecular structure. Systematic analysis of the deposition parameters shows that aggregate formation depends on the underlying material and increases with increasing substrate temperature and decreasing evaporation rate. The two green emitters Ir(ppy)3 and Ir(ppy)2(acac) are additionally studied by means of X-ray diffraction. Both emitters form crystallite grains and exhibit a preferred orientation. Doping the emitters into an amorphous host, both orientation and crystallite formation retain at the investigated doping concentrations above 20 wt%. This result is a first step toward further understanding of the mechanism of transition dipole orientation.:List of Publications 1 Introduction 2 Principles of Organic Semiconductors 2.1 Molecular Orbitals 2.2 Optical Properties 2.3 Intermolecular Energy Transfer 2.4 Charge Transport 2.5 Organic Light-Emitting Diodes 2.5.1 Structure and Working Principle 2.5.2 Characterization 3 Theory of Efficiency Roll-Off 3.1 Current Status 3.2 Processes Leading to Roll-Off 3.2.1 Triplet-Triplet Annihilation 3.2.2 Triplet-Polaron Interaction 3.2.3 Further Processes Influencing Roll-Off 3.3 Interplay of the Various Processes 3.4 Scope of this Work 4 Experimental Methods 4.1 Sample Preparation 4.2 Measurement 4.2.1 Thin-Film Characterization 4.2.2 OLED Characterization 4.3 Materials 4.3.1 Electrodes, Transport Materials, and Blockers 4.3.2 Materials of the Emission Layer 5 Influence of the Optical Environment 5.1 Introduction 5.2 Influence of Emitter-Cathode Distance 5.3 Emitter Lifetime and Orientation 5.4 Correlation of Roll-Off and Orientation 5.5 Simulation of Roll-Off 5.5.1 Influence of the Electroluminescence Spectrum 5.5.2 Influence of Orientation and Radiative Efficiency 5.6 Conclusion 6 Influence of the Emission Profile 6.1 Preliminary Considerations 6.1.1 Exciton Generation and Diffusion 6.1.2 Width of the Emission Zone 6.1.3 Dependence on the Structure of the Emission Layer 6.2 Measurement of the Emission Profile 6.2.1 Method 6.2.2 Mathematical Description 6.2.3 Experimental Realization and Evaluation 6.3 Ambipolar Matrix Materials 6.3.1 Device Performance 6.3.2 Influence of the Sensing Layer 6.3.3 Emission Profile 6.4 Double- and Mixed Emission Layers 6.4.1 Emission Profile 6.4.2 Influence of the Matrix Ratio 6.5 Summary and Outlook 7 Influence of Molecular Aggregation 7.1 Introduction 7.2 Aggregation of Homoleptic and Heteroleptic Emitters 7.2.1 Photoluminescence Measurements 7.2.2 Time-Resolved Spectroscopy 7.2.3 X-Ray Diffraction 7.2.4 Conclusions on Emitter Orientation 7.2.5 Comparison of the Different Methods—Emitter Aggregation 7.3 Influence of the Matrix Material 7.3.1 Photoluminescence Measurements 7.3.2 Time-Resolved Spectroscopy 7.4 Influence of Processing Parameters 7.4.1 Substrate Heating 7.4.2 Underlying Layer 7.4.3 Evaporation Rate 7.5 Summary and Implications of Aggregation on Efficiency Roll-Off 8 Summary and Outlook 8.1 Summary of Roll-Off Investigations 8.2 Improving the High-Brightness Performance Further 8.3 Concluding Words on Emitter Orientation A Appendix to Theory of Efficiency Roll-Off B Appendix to Emission and Sensing Profiles B.1 Emission Profiles B.2 Emission Profiles Including a Sensing Layer B.3 Sensing Profiles C Appendix to Double- and Mixed Emission Layers C.1 Sample Uniformity C.2 Influence of the Sensor on Current Density C.3 Further D-EML and M-EML structures D Appendix to Molecular Aggregation List of Chemical Compounds List of Abbreviations List of Important Symbols Bibliography Acknowledgement / Die Effizienz organischer Leuchtdioden (OLEDs) nimmt üblicherweise mit ansteigender Stromdichte ab. Dieser so genannte Roll-Off erschwert den Markteintritt von OLEDs in Bereichen, die hohe Helligkeiten erfordern, wie beispielsweise in der Beleuchtung. Einer der wichtigsten Prozesse, die zu Roll-Off führen, ist die Annihilation von Exzitonen. Diese nimmt mit steigender Exzitonendichte zu und ist vor allem in phosphoreszenten OLEDs aufgrund der dort vorhandenen langen Triplettlebensdauer ein großer Verlustfaktor. Im Rahmen dieser Dissertation werden Methoden vorgestellt, die mittels Reduzierung der Exzitonendichte den Roll-Off in phosphoreszenten OLEDs verringern können. Dazu gehören die Veränderung der Exzitonenlebensdauer, die Untersuchung der räumlichen Verteilung der Exzitonen und die Erforschung der Bildung von Emitteraggregaten. Die gewonnenen Ergebnisse führen zu einem besseren Verständnis des Effizienz Roll-Offs und helfen, die Effizienz von OLEDs bei hohen Helligkeiten zu verbessern. Die Emitterlebensdauer kann über den Purcell-Effekt durch Veränderung des die emittierenden Dipole umgebenden elektromagnetischen Felds beeinflusst werden. Dieser Effekt wird genutzt, indem der Abstand zwischen Emitter und Metallelektrode für zwei verschiedene OLED-Aufbauten variiert wird. Der Roll-Off ist stark abhängig von der Position und Orientierung des Emitters und kann durch Modellierung der Daten auf Basis von Triplett-Triplett-Annihilation erklärt werden. Durch Simulation des Roll-Offs in Abhängigkeit des Emitter-Kathode-Abstands, der Orientierung und der strahlenden Effizienz der emittierenden Dipole werden Prinzipien zur optimalen Leistung von OLEDs bei hohen Helligkeiten entwickelt. Als nächstes wird eine Methode eingeführt mittels derer die räumliche Exzitonenverteilung extrahiert werden kann. Dafür wird eine dünne Sensorschicht in die Emissionsschicht eingebracht, die lokal Exzitonen auslöscht. Unter Variation der Position des Sensors wird ein Profil der Auslöschungsintensität bestimmt. Die gemessene Intensität wird mittels einer umfassenden Theorie auf Grundlage der Diffusionsgleichung angepasst, wodurch sich die räumliche Verteilung der Exzitonen und die Diffusionslänge mit einer Auflösung von 1nm ergibt. Die Methode wird auf eine Emissionsschicht angewandt, die das ambipolare Matrixmaterial CBP enthält. Entgegen der Erwartung, dass die Exzitonenbildung in ambipolaren Materialien weiter ausgedehnt ist, ist die gemessene Emissionszone sehr schmal und befindet sich an der Grenze zur Elektronentransportschicht. Um eine Verbreiterung des Emissionsprofils zu ermöglichen, werden weitere Strukturen untersucht. Dabei wird eine schmale Emissionszone in Doppelemissionsschichten beobachtet, wohingegen gemischte Emissionsschichten zu einer Verbreiterung der Exzitonenbildung führen können. Vorangegangene Untersuchungen deckten einen Zusammenhang zwischen der Aggregation von Emittermolekülen und dem Dipolmoment des Emitters auf. In dieser Arbeit werden weitere Emittermoleküle untersucht, wobei eine stärkere Aggregation von homoleptischen Emittern im Vergleich zu heteroleptischen festgestellt wird. Dies ist einerseits im höheren Dipol-Dipol-Potential der homoleptischen Verbindungen und andererseits in der Molekülstruktur begründet. Eine systematische Analyse der Herstellungsparameter zeigt, dass die Aggregatbildung von dem darunter liegenden Material abhängt und mit steigender Substrattemperatur und sinkender Verdampfungsrate zunimmt. Die zwei Grünemitter Ir(ppy)3 und Ir(ppy)2(acac) werden zusätzlich mittels Röntgenspektroskopie untersucht. Beide Emitter bilden kristalline Körner und weisen eine bevorzugte Orientierung auf. Sowohl die Kristallbildung als auch die Orientierung bleiben erhalten, wenn die Emitter mit mehr als 20 Gewichtsprozent in das Matrixmaterial CBP dotiert werden. Dieses Ergebnis ist ein erster Schritt zum besseren Verständnis der in vielen Iridium-Emittern beobachteten Orientierung des Übergangsdipolmoments.:List of Publications 1 Introduction 2 Principles of Organic Semiconductors 2.1 Molecular Orbitals 2.2 Optical Properties 2.3 Intermolecular Energy Transfer 2.4 Charge Transport 2.5 Organic Light-Emitting Diodes 2.5.1 Structure and Working Principle 2.5.2 Characterization 3 Theory of Efficiency Roll-Off 3.1 Current Status 3.2 Processes Leading to Roll-Off 3.2.1 Triplet-Triplet Annihilation 3.2.2 Triplet-Polaron Interaction 3.2.3 Further Processes Influencing Roll-Off 3.3 Interplay of the Various Processes 3.4 Scope of this Work 4 Experimental Methods 4.1 Sample Preparation 4.2 Measurement 4.2.1 Thin-Film Characterization 4.2.2 OLED Characterization 4.3 Materials 4.3.1 Electrodes, Transport Materials, and Blockers 4.3.2 Materials of the Emission Layer 5 Influence of the Optical Environment 5.1 Introduction 5.2 Influence of Emitter-Cathode Distance 5.3 Emitter Lifetime and Orientation 5.4 Correlation of Roll-Off and Orientation 5.5 Simulation of Roll-Off 5.5.1 Influence of the Electroluminescence Spectrum 5.5.2 Influence of Orientation and Radiative Efficiency 5.6 Conclusion 6 Influence of the Emission Profile 6.1 Preliminary Considerations 6.1.1 Exciton Generation and Diffusion 6.1.2 Width of the Emission Zone 6.1.3 Dependence on the Structure of the Emission Layer 6.2 Measurement of the Emission Profile 6.2.1 Method 6.2.2 Mathematical Description 6.2.3 Experimental Realization and Evaluation 6.3 Ambipolar Matrix Materials 6.3.1 Device Performance 6.3.2 Influence of the Sensing Layer 6.3.3 Emission Profile 6.4 Double- and Mixed Emission Layers 6.4.1 Emission Profile 6.4.2 Influence of the Matrix Ratio 6.5 Summary and Outlook 7 Influence of Molecular Aggregation 7.1 Introduction 7.2 Aggregation of Homoleptic and Heteroleptic Emitters 7.2.1 Photoluminescence Measurements 7.2.2 Time-Resolved Spectroscopy 7.2.3 X-Ray Diffraction 7.2.4 Conclusions on Emitter Orientation 7.2.5 Comparison of the Different Methods—Emitter Aggregation 7.3 Influence of the Matrix Material 7.3.1 Photoluminescence Measurements 7.3.2 Time-Resolved Spectroscopy 7.4 Influence of Processing Parameters 7.4.1 Substrate Heating 7.4.2 Underlying Layer 7.4.3 Evaporation Rate 7.5 Summary and Implications of Aggregation on Efficiency Roll-Off 8 Summary and Outlook 8.1 Summary of Roll-Off Investigations 8.2 Improving the High-Brightness Performance Further 8.3 Concluding Words on Emitter Orientation A Appendix to Theory of Efficiency Roll-Off B Appendix to Emission and Sensing Profiles B.1 Emission Profiles B.2 Emission Profiles Including a Sensing Layer B.3 Sensing Profiles C Appendix to Double- and Mixed Emission Layers C.1 Sample Uniformity C.2 Influence of the Sensor on Current Density C.3 Further D-EML and M-EML structures D Appendix to Molecular Aggregation List of Chemical Compounds List of Abbreviations List of Important Symbols Bibliography Acknowledgement

This thesis describes investigations into the photophysical properties of luminescent materials and their application in optoelectronic devices such as light emitting diodes and photodetectors. The materials used were all solution processable because of the interest in low cost processing of organics. I have investigated the photophysics of 1,4,5,8,9,12-hexamethyltriphenylene, a triphenylene derivative which has its luminescence enhanced by the addition of methyl groups. These groups change the planar shape of the triphenylene molecule into a twisted one, changing the symmetry of the molecule and increasing its dipole moment in absorption and emission by ~4 fold. This increased its rate of radiative deexcitation by ~20 times. In addition, the twisted shape of the molecule prevents intermolecular interactions and concentration effects from affecting the luminescence. This results in an efficient solid-state photoluminescence quantum yield of 31%. This thesis also includes an investigation into phosphorescent polymer dendrimers, designed to have suitable viscosities in solution for inkjet printed OLED applications. A photophysical study of the intra-chain aggregation effects on the luminescence was undertaken in both homopolymers and copolymers with high energy gap spacer units. Using double dendrons to increase the steric protection of the luminescent cores, the best homopolymers achieved 12.1% external quantum efficiency (39.3 cd/A) at 100 cd/m² brightness and the best co-polymer achieved 14.7% EQE (48.3 cd/A) at 100 cd/m². This compares favourably with 11.8% EQE for the best phosphorescent polymer and 16% for the best solution processed dendrimer OLED previously reported. Finally I have applied a solution processed enhancement layer to silicon photodiodes to enhance their ultraviolet response. Using a blend of materials to give favourable absorption and emission properties, 61% external quantum efficiency was achieved at 200 nm, which is better than the 20-30% typical for vacuum deposited lumogen enhancement layers used commercially.

Nos últimos anos, complexos de irídio tem sido sugeridos para uso em materiais luminescentes, tais como diodos orgânicos emissores de luz (OLED\'s) e células eletroquímicas emissoras de luz (LEEC\'s). Suas potenciais utilidades como dispositivo é devido as suas características físico-químicas e fotofísicas, as quais são caracterizadas por tempos de vida curtos para o tripleto, estabilidade térmica, além da possibilidade de modificar a emissão sobre uma vasta gama de cores do espectro. Atualmente, muitas pesquisas tentam encontrar complexos de irídio com emissão de luz azul. No entanto, embora emissores de luz azul já tenham sido desenvolvidos, existe o problema relacionado a agregação destes complexos. Para resolver este o problema da agregação é necessário modificar a estrutura padrão do complexo com cadeias carbônicas saturadas para evitar empilhamento π-π. Experimentalmente esta é uma tarefa um tanto difícil. Dessa forma, métodos computacionais têm sido viáveis como uma abordagem para entender a estrutura e propriedades eletrônicas dos sistemas estudados. Aqui, é apresentado um estudo teórico baseado na teoria do funcional da densidade (DFT) para investigar a agregação de complexos de irídio, além de predizer como esta pode ser controlada com o uso de grupos substituintes adequados. Os cálculos foram realizados usando funcional PBE0 e conjunto de base 6-31G*, o qual provou ser adequada na descrição das propriedades do complexo. Portanto, cálculos subsequentes mostraram bons resultados, onde os estados excitados foram previstos ser de natureza predominantemente MLCT (transferência de carga do metal para o ligante) para o complexo 1 e LC (carga centrada no ligante) para o complexo 2. Alterações no ambiente químico provou ter grande influência sobre os estados excitados, onde a inclusão do solvente favoreceu a estabilidade, mantendo os estados excitados tripletos com energia entre 3.01 eV e 3.03 eV. Além disso, o uso dos grupos substituintes provou ser de grande importância para prevenir a agregação, especialmente no complexo 2, em que a partir do dímero matriz (sem substituintes) para o complexo substituído 2-1 (com metil) houve uma desestabilização da energia de interação entre os monômeros no dímero por ~ 19.78 kcal/mol, sendo que a energia do primeiro foi estimada ser -39.78 kcal/mol, enquanto o segundo foi -20 kcal/mol. Nossos resultados sugerem que a modificação do complexo torna-se bastante promissora, fazendo uso de pequenos grupos substituintes e cadeias carbônicas alifáticas, evitando assim, a agregação por empilhamento π-π. / In the last few years, iridium complexes have been suggested for use in luminescent materials such as organic light-emitting diodes (OLEDs) and light emitting electrochemical cells (LEECs)1-3. Their potential utility as luminescent devices is due to the physicochemical and photophysical properties, which are featured by short triplet emitting lifetimes (microseconds time scale), thermal stability, besides of possibility to tune the emission over desired spectral range. Actually, many researches try to find iridium complexes with efficient deep-blue emission, in order to use in these devices. Although many deep-blue emitters have been developed, there is still a big problem related to aggregation. So far, little has been reported about iridium complexes in solid environments, such as inorganic matrix of OLEDs and LEECs devices. To solve this issue is needed tune the structure of the complex in order to prevent the aggregation (steric hindrance), by means of drawing saturated carbon chains on the ligands to avoid the π-π stacking. Experimentally, this is a rather challenging and expensive task. In this aspect, computational methods have been performed as approaches to gain deeper insights about the structure and electronic properties of the studied systems. Here, we present a theoretical study based on density functional theory to investigate the aggregation iridium complexes, in addition to predict how this can be controlled with the use of suitable substituent groups. Calculations were performed using functional PBE0 and 6-31G* basis functions, which proved adequate in describing the properties of the complex. Therefore, subsequent calculations showed good results, where the excited state of the complex are provided, these being predominantly MLCT (metal to ligand charge transfer) nature for the complex 1 and LC (ligand centered) nature to complex 2. Changes in the chemical environment proved to have great influence on the excited states, where the inclusion of the solvent favored its stability, keeping the triplet excited states with energy between 3.01 and 3.03 eV. Furthermore, the use of substituent groups proved to be of great importance to prevent aggregation, especially in complex 2, wherein from the matrix dimer (no substituted) to complex with methyl groups there was a destabilization of the interaction energy between the monomers in the dimer by ~ 19.78 kcal / mol, being that the energy of the first was -39.78 kcal / mol, while the second was to -20 kcal / mol. Our results suggest that the modification of the complex becomes quite promising, making use of small groups and aliphatic carbon chains, thus avoiding aggregation by stacking.

Orientadora: Profª. Drª. Karina Passalacqua Morelli Frin / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Ciência e Tecnologia/Química, 2014. / Este trabalho trata das propriedades dos compostos polipiridinicos fosforescentes fac-[ReCl(CO)3(NN)], fac-[Re(py)(CO)3(NN)]+, em que NN = 4,7-difenil-1,10-fenantrolina (ph2phen) ou 4,7-dicloro-1,10-fenantrolina (Cl2phen) e py = piridina. Os compostos foram sintetizados, purificados, caracterizados por meio da ressonancia magnetica nuclear de protons, 1H NMR, espectroscopias UV-visivel e na regiao do infravermelho e as propriedades eletroquimicas e fotofisicas foram investigadas. As frequencias de estiramento das carbonilas dos compostos fac-[ReCl(CO)3(ph2phen)] (2020, 1912, 1878 cm-1), fac-[Re(py)(CO)3(ph2phen)]+ (2029, 1905 cm-1), fac-[ReCl(CO)3(Cl2phen)] (2022, 1883 cm-1) e fac-[Re(py)(CO)3(Cl2phen)]+ (2030, 1913 cm-1) estao em acordo com a geometria facial dos complexos de renio(I) e os deslocamentos nas posicoes dos picos para frequencias mais altas sustentam o maior efeito retirador de eletrons do ligante coordenado Cl2phen quando comparado ao ph2phen. Nos espectros eletronicos na regiao do UV-visivel dos compostos fac-[ReCl(CO)3(NN)] foram observadas duas regioes principais: uma de mais alta energia, atribuida a ILNN, e uma de menor energia, atribuida a MLCTRe¨NN. Para os compostos fac-[Re(py)(CO)3(NN)]+, atribui-se ainda uma regiao ILpy e MLCTRe¨py. Os compostos apresentam emissao em solucao e em meio polimerico, que e atribuida ao estado excitado de transferencia de carga do metal para o ligante polipiridinico (3MLCTRe¨NN), NN = ph2phen ou Cl2phen, de menor energia. A energia do estado excitado de transferencia de carga (MLCT) dos compostos podem ser modificadas em funcao do ligante axial, do substituinte da fenantrolina e do meio. A energia do maximo de emissao e deslocada para a regiao de mais baixa energia com grupos retiradores de eletrons na fenantrolina, fac-[ReCl(CO)3(ph2phen)] (¿Émax = 615 nm), fac-[ReCl(CO)3(Cl2phen)] (¿Émax = 640) nm, fac-[Re(py)(CO)3(ph2phen)]+( ¿Émax = 570 nm), fac-[Re(py)(CO)3(Cl2phen)]+ (¿Émax = 590 nm) quando comparada a fenantrolina nao substituida, fac-[ReCl(CO)3(phen)] (¿Émax = 600 nm) e fac-[Re(py)(CO)3(phen)]+ (¿Émax = 550 nm) . Nos experimentos de tempos de vida de emissao para os compostos fac-[ReCl(CO)3(Cl2phen)] e fac-[Re(py)(CO)3(Cl2phen)]+ foram encontrados os valores, 1,46 ¿Ês e 1,43 ¿Ês, que sao consistentes com estados emissores que apresentam carater triplete. Para o fac-[ReCl(CO)3(Cl2phen)] foi encontrado um segundo tempo de vida de emissao, 30 ns, que pode ser atribuido a um segundo estado emissor de carater singlete. O composto fac-[ReCl(CO)3(Cl2phen)] apresentou processos de oxidacao, Re(I)¨(II), a Epa = +1,77 V (vs NHE), e reducao, (Cl2phen)¨(Cl2phen*-), a Epc = -1,1 V (vs NHE), em CH2Cl2, e os niveis de energia do highest occupied molecular orbital (HOMO) e do lowest unoccupied molecular orbital (LUMO) calculados iguais a . 6,2 V e - 2,9 V, respectivamente, e comparados aos do PVK.As características eletroquímicas e de emissão, tais como comprimentos de onda, rendimentos quânticos e tempos de vida de emissão do fac-[ReCl(CO)3(Cl2phen)], indicam uma potencial aplicação em dispositivos OLEDs. / This work deals with fundamental properties of the phosphorescent polypyridyl complexes fac-[ReCl(CO)3(NN)], fac-[Re(py)(CO)3(NN)]+, NN = 4,7-diphenil-1,10-phenanthroline (ph2phen) or Cl2phen = 4,7-dichloro-1,10-phenanthroline (Cl2phen) and py = pyridine. The compounds were synthesized, purified and characterized by 1H NMR, UV-vis and IR spectroscopies and both photophysical and electrochemical behaviors have been investigated. The CO stretching frequencies of fac-[ReCl(CO)3(ph2phen)] (2020, 1912, 1878 cm-1), fac-[Re(py)(CO)3(ph2phen)]+ (2029, 1905 cm-1), fac-[ReCl(CO)3(Cl2phen)] (2022, 1883 cm-1) and fac-[Re(py)(CO)3(Cl2phen)]+ (2030, 1913 cm-1) compounds were in accordance with facial geometry of the rhenium complexes and the shifts in peak position to higher frequencies support a better electron-withdrawing character of the coordinated Cl2phen ligand when compared to the ph2phen analog compound. The electronic absorption spectra of the compounds fac-[ReCl(CO)3(NN)] exhibit two main absorption bands: the higher energy band, which was assigned to ILNN, and the lower energy band, assigned to MLCTRe¨NN. The fac-[Re(py)(CO)3(NN)]+ complexes exhibited also a region assigned to an ILpy and MLCTRe¨py transitions. Complexes showed emission in both solution and rigid media, arising from the lowest lying metal to ligand charge transfer (3MLCT) excited state. The energy of the metal to ligand charge transfer (MLCT) excited state of the complexes changed as NN and axial ligand and medium is varied. The energy of the emission maximum was red shift when electron withdrawing substituents were attached at phenanthroline, fac-[ReCl(CO)3(ph2phen)] (¿Émax = 615 nm), fac-[ReCl(CO)3(Cl2phen)] (¿Émax = 640) nm, fac-[Re(py)(CO)3(ph2phen)]+( ¿Émax = 570 nm), fac-[Re(py)(CO)3(Cl2phen)]+ (¿Émax = 590 nm) compared to that phenantroline not replaced, fac-[ReCl(CO)3(phen)] (¿Émax = 600 nm) and fac-[Re(py)(CO)3(phen)]+ (¿Émax = 550 nm). The emission lifetimes measurements of fac-[ReCl(CO)3(Cl2phen)] and fac-[Re(py)(CO)3(Cl2phen)]+ were obtained, 1,46 ¿Ês and 1,43 ¿Ês, and were consistent with a triplet character emitting state. For the fac-[ReCl(CO)3(Cl2phen)], was found a second lifetime, 30 ns, that suggest a second emitting excited state which has singlet character. The compound fac-[ReCl(CO)3(Cl2phen)] showed oxidation, Re(I)¨(II), Epa = +1,78 V (vs NHE), and reduction, (Cl2phen) ¨ (Cl2phen*-), Epc = - 1,1 V (vs NHE), processes, in CH2Cl2, and the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels of the compound were calculated . 6.2 V and . 2.9 V, respectively, and compared to PVK. The electrochemical and emission characteristics such as wavelength, quantum yields and lifetimes fac-[ReCl(CO)3(Cl2phen)], indicate a potential application in OLEDs devices.

The library has existed as a repository for knowledge for centuries. However, in spite of the information revolution and its watershed component, the internet, this institution has found itself fundamentally unchanged. Great strides have been taken to adapt the library to this changing world, but these incremental changes are timid and reactionary. Through the internet the floodgates have opened; individuals are creating and sharing information both personal and academic, in the form of not-so-private journals, works of creative fiction, works of journalism, works of scholarship, and every other form of intellectual (and not so intellectual) propagation imaginable. Additionally, advances in computer display and input technology are breaking down the conceptions of what a computer is and how we interact with them. The trend is pointing to a future where computers are no longer objects, but an integrated component of our built environment, capable of responding to practically limitless simultaneous individual users. This thesis will take the lead on these growing trends and create a new type of information age institution to evolve alongside, rather than supplant, the library: Icomde. This new institution will explore the possibilities of these new technologies while embracing the spirit of the information revolution. It will create a unique place where people can experience state of the art means of information creation, interaction, and collaboration. Finally, when the technology present has been fundamentally surpassed, the Icomde will be dismantled and the pieces distributed to dozens of locations throughout the world to found new Icomdes, with the original site becoming host to the next iteration of whatever advanced technologies will follow. This thesis will seek to examine the cultural, social role of the library as it has evolved and has been propagated through the course of human events, using design and history research, so as to employ the 'spirit' of this place as completely as possible in spite of the proposed radical paradigm shift. It will also use logical argumentation to organize trends in web content generation and publication into patterns that can be interpreted and acted upon in a forward-thinking fashion rather than a reactionary one.

Afin de répondre aux contraintes des nouveaux champs d'applications des biocapteurs, le laboratoire LISA a développé un lecteur optique de fluorescence pour des immunoanalyses permettant une détection en continue. Cet instrument, dont le support de la réaction biologique est une lame de verre, utilise le couplage de la fluorescence en champ proche dans celle-ci. Mon travail de thèse a consisté à rechercher les possibilités d'améliorer les performances de compacité, de robustesse et d'adaptabilité du système en cherchant à intégrer les sources d'excitation de type OLED dans la lame de verre. La recherche d'une configuration adaptée à nos contraintes de détection nous a d'autre part poussé à étudier la répartition de l'émission de molécules fluorescentes à l'interface d'un substrat stratifié.<br />Pour ce faire, un modèle théorique basé sur la décomposition en ondes planes de l'émission d'un dipôle a été développé. Ce modèle nous a permis d'étudier à la fois les propriétés d'émission de sources organiques de types OLED ainsi que celles de molécules fluorescentes situées à l'interface d'un milieu massif recouvert ou non par une couche mince. <br />Une étude expérimentale et théorique de sources organique situées à l'intérieur d'une cavité Fabry Pérot a permis de fournir des réponses concrètes aux deux principaux défauts inhérents aux OLED pour leur intégration, la directivité angulaire d'émission et la largeur spectrale. Enfin, l'étude de lame de verre recouverte par une couche mince de Nitrure de Silicium a montré qu'il était possible d'améliorer le rapport signal sur bruit du détecteur et a permis de valider la configuration de l'instrument mis au point au laboratoire.

Le développement de dispositifs OLED pour des applications dans les afficheurs ou l'éclairage nécessite généralement une approche expérimentale longue et coûteuse afin de déterminer les paramètres clés influant sur les performances. Le but d'une modélisation électrique est de remplacer ce système complexe par un objet simple et de reproduire voire prédire ses comportements principaux (caractéristique Intensité-Tension, J-V) afin de limiter le nombre de séries d'expériences. Une première méthode consiste à utiliser des modèles continus de bandes d'énergie, issus des semiconducteurs cristallins. Cette modélisation par éléments finis 2D a notamment permis de rendre compte des variations d'épaisseurs des couches organiques pour des densités de courant élevées (50 < J < 7x10^3 mA/cm2). Nous avons également montré l'intérêt des simulations 2D pour étudier des architectures complexes avec une électrode nanostructurée. Une seconde méthode réside dans le développement d'un modèle électrique compact, de type composants, compatible avec les outils professionnels de CAO électronique. Le circuit équivalent proposé sépare les phénomènes d'injection et de transport de charges. Il reproduit précisément, avec seulement 8 paramètres obtenus à partir de mesures simples, les caractéristiques statiques J-V sur une grande plage de densités de courant (de 10^-6 à 7x10^3 mA/cm2) ainsi que le comportement dynamique global jusqu'au MHz. Ce modèle permet la simulation de systèmes complexes tels que les écrans matriciels avec leur circuit d'adressage. Par ailleurs, l'analyse et la quantification de l'influence de différentes variations expérimentales en font un outil de développement et/ou de contrôle de production. Les résultats acquis et les perspectives montrent l'intérêt de disposer d'outils de modélisation pour développer des composants ou des dispositifs performants à base d'OLEDs.

Large area flat displays are nowadays considered being a commodity. After the era of bulky CRT TV technology, LCD and OLED have taken over as the most prevalent technologies for high quality image display devices. An important factor underlying the success of these technologies has been the development of high performance photomask writers in combination with a precise photomask process. Photomask manufacturing can be regarded as an art, highly dependent on qualified and skilled workers in a few companies located in Asia. The manufacturing yield in the photomask process depends to a great extent on several steps of measurements and inspections. Metrology, which is the focus of this thesis, is the science of measurement and is a prerequisite for maintaining high quality in all manufacturing processes. The details and challenges of performing critical measurements over large area photomasks of square meter sizes will be discussed. In particular the development of methods and algorithms related to the metrology system MMS15000, the world standard for large area photomask metrology today, will be presented. The most important quality of a metrology system is repeatability. Achieving good repeatability requires a stable environment, carefully selected materials, sophisticated mechanical solutions, precise optics and capable software. Attributes of the air including humidity, CO2 level, pressure and turbulence are other factors that can impact repeatability and accuracy if not handled properly. Besides the former qualities, there is also the behavior of the photomask itself that needs to be carefully handled in order to achieve a good correspondence to the Cartesian coordinate system. An uncertainty specification below 100 nm (3σ) over an area measured in square meters cannot be fulfilled unless special care is taken to compensate for gravity-induced errors from the photomask itself when it is resting on the metrology tool stage. Calibration is therefore a considerable challenge over these large areas. A novel method for self-calibration will be presented and discussed in the thesis. This is a general method that has proven to be highly robust even in cases when the self-calibration problem is close to being underdetermined. A random sampling method based on massive averaging in the time domain will be presented as the solution for achieving precise spatial measurements of the photomask patterns. This method has been used for detection of the position of chrome or glass edges on the photomask with a repeatability of 1.5 nm (3σ), using a measurement time of 250 ms. The method has also been used for verification of large area measurement repeatability of approximately 10 nm (3σ) when measuring several hundred measurement marks covering an area of 0.8 x 0.8 m2. The measurement of linewidths, referred to in the photomask industry as critical dimension (CD) measurements, is another important task for the MMS15000 system. A threshold-based inverse convolution method will be presented that enhances resolution down to 0.5 µm without requiring a change to the numerical aperture of the system. As already mentioned, metrology is very important for maintaining high quality in a manufacturing environment. In the mask manufacturing industry in particular, the cost of poor quality (CoPQ) is extremely high. Besides the high materials cost, there are also the stringent requirements placed on CD and mask overlay, along with the need for zero defects that make the photomask industry unique. This topic is discussed further, and is shown to be a strong motivation for the development of the ultra-precision metrology built into the MMS15000 system. / <p>QC 20130515</p>

This thesis begins with a brief overview of current strategies used in the synthesis of side-chain functionalizad polymers and materials. The discussion then focuses more explicitly on transition metal-based motifs and methodologies that are employed in polymer functionalization and continues with a more detailed overview of this field. The primary hypothesis that is addressed herein is that combining the versatility and strength of metal-ligand interactions with the efficiency and functional group tolerance of ROMP comprises a useful method of generating a variety of functionalized polymers and materials via side-chain metal coordination. Thus, the goal is to test this hypothesis by synthesizing functionalized polymers with a range of useful properties to demonstrate the relevance and importance of this methodology, by employing several different strategies to show the synthetic ease by which the materials can be realized. The strategies and methods discussed in the synthesis of side-chain functionalized polymers are divided into three subgroups: (1) pre-polymerization functionalization, in which all of the modifications take place on the monomer with polymerization as the last step, (2) post-polymerization functionalization, in which the polymer itself is subsequently modified, and (3) combinations of the first two strategies. It is shown that useful functional polymers and materials can be synthesized by any of the above strategies, and representative examples of each are given in both the introduction and in the body of work presented. Modes of functionalization are all based on transition metal coordination, and polymerizations are primarily carried out via ROMP. Metal coordination is shown to be a useful technique for functionalizing polymers, to creating supported emissive complexes, to modulating solution viscosity. Finally, conclusions are drawn regarding the various strategies presented herein, and potential future directions are discussed.

The structural, electronic, and optical properties of a series of organic pi-conjugated polymer, oligomer, or molecular materials of interest for applications in organic electronics are described. For this purpose, quantum-chemical techniques ranging from Density Functional Theory to Hartree-Fock ab initio and semiempirical methods are used to evaluate the charge-transport, charge-transfer, and electroluminescence properties of pi-conjugated organic materials. First, the effect of electronic polarization on the charge-transport parameters of organic semiconductors is discussed. A generalized methodology based on a basis set orthogonalization procedure is developed to determine reliable charge-transport characteristics. The charge-transport parameters of a number of organic semiconductors such as oligoacenes and derivatives are studied with this methodology. Then, triplet emitters, in particular iridium complexes, that achieve high efficiency electroluminescence in organic light-emitting diodes are discussed. The effects of ligand substitution and orientation on the luminescent properties of iridium compounds are investigated in order to develop structure-properties relationships. The emission properties of these complexes are found to be governed by an interplay between metal-to-ligand charge transfer excitations and ligand-centered and/or interligand excitations. The extent of mixing of these various excitations turns out to be highly dependent on the nature of the substituents. Design strategies to shift the emission color towards deep blue are proposed. Finally, several classes of materials acting as hosts for phosphorescent emitters are studied. It is shown that restricting the conjugation length leads to high energy gap host materials suitable for blue phosphorescent emitters.