Thesis describes recent advances in the synthesis of donor-acceptor conjugated copolymers and their efficient doping via molecular p-dopants.:Chapter I Preface Motivation and Goals Outline 7 Chapter II 8 State of the Art & Characterization Techniques 8 2.1. General Introduction 8 2.1.1. Concept of Conjugated Polymers 9 2.1.2. Electronic Conduction and Necessity of Doping in Conjugated Polymers 11 2.1.3. Solubility and Processing. 14 2.2. Doping 17 2.2.1. Concept of Doping in Conjugated Polymers 17 2.2.2. Morphological Changes of the Material upon Doping. Conductivity. 20 2.2.3. State-of-the-art p-dopants. 23 2.3. Synthetic Strategies for the Design of (Semi)conducting Polymers 28 2.3.1. A Concise Review: from Polyacetylene till Modern DA Polymers 28 2.3.2. Synthetic Routes to Conjugated Polymers 31 2.3.3. Step-growth vs Chain-growth 34 2.3.4. Benchmark solution-processable Polymers 38 2.4. Characterization techniques 41 2.4.1. Conductivity Measurements 41 2.4.2. Electrochemical Voltammetry 42 2.4.3. Uv-vis-near-infrared 44 2.4.4. Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy. 44 2.4.5. Morphological studies. 45 2.4.6. Electron Spin Resonance Spectroscopy. 46 Chapter III 48 Results & Discussion 48 3.1. Diketopyrrolopyrrole-Based Copolymers 50 3.1.1. Motivation 50 3.1.2. Results and Discussion 51 3.1.4. Summary 89 3.2. Naphthalene Diimide-based Copolymer 90 3.2.1. Motivation 90 3.2.2. Results and Discussion 92 3.2.4. Summary 105 3.3. Isoindigo-Based Copolymers 107 3.3.1. Motivation 107 3.3.2. Results and Discussion 108 3.3.4. Summary 119 Summary & Conclusions 120 Outlook 123 Chapter IV 125 Experimental Part 125 4.1. General Methods and Instrumentation 125 4.2. Synthesis 129 4.2.1. Synthesis of diketopyrrolopyrrole copolymer. 129 4.2.2. Synthesis of electron-conducting polymer (PNDIT2) 132 4.2.3. Synthesis of polyisoIndigo 132 4.2.3. Synthesis of Dopants 135 4.3. Cyclic voltammetry measurements 136 4.4. GIWAX data. 143 4.5. Films preparation 145 References 147 Table of Abbreviations 159 List of Publications 161 Acknowledgements 162 Appendix 163

<p>Neuromorphic computing endeavors to develop computational systems capable of emulating the brain’s capacity to execute intricate tasks concurrently and with remarkable energy efficiency. By utilizing new bioinspired computing architectures, these systems have the potential to revolutionize high-performance computing and enable local, low-energy computing for sensors and robots. Organic and soft materials are particularly attractive for neuromorphic computing as they offer biocompatibility, low-energy switching, and excellent tunability at a relatively low cost. Additionally, organic materials provide physical flexibility, large-area fabrication, and printability.</p><p>This doctoral dissertation showcases the research conducted in fabricating a comprehensive spiking organic neuron, which serves as the fundamental constituent of a circuit system for neuromorphic computing. The major contribution of this dissertation is the development of the organic, flexible neuron composed of spiking synapses and somas utilizing ultra-low voltage organic field-effect transistors (OFETs) for information processing. The synaptic and somatic circuits are implemented using physically flexible and biocompatible organic electronics necessary to realize the Polymer Neuromorphic Circuitry. An Axon-Hillock (AH) somatic circuit was fabricated and analyzed, followed by the adaptation of a log-domain integrator (LDI) synaptic circuit and the fabrication and analysis of a differential-pair integrator (DPI). Finally, a spiking organic neuron was formed by combining two LDI synaptic circuits and one AH synaptic circuit, and its characteristics were thoroughly examined. This is the first demonstration of the fabrication of an entire neuron using solid-state organic materials over a flexible substrate with integrated complementary OFETs and capacitors.</p>

This research serves as a meticulous examination into cross-conjugated materials and how alterations of the frontier molecular orbitals can be utilized for applications in "chemical tongue" organic sensing devices. With conjugated materials being used in the development of new sensory devices for detection of metals, bacteria, and chemical warfare agents, the field of organic sensing is growing faster than ever. The purpose of this dissertation is to provide a precedence for the synthesis of new cross-conjugated compounds and outline potential applications of these materials as chemical sensors and molecular probes.

This thesis describes a number of studies on organic semiconductors as laser gain media with the aim of simplifying the excitation scheme and exploring potential applications. A hybrid device taking the advantage of high power inorganic light emitting diodes (LEDs) and low threshold organic distributed feedback lasers is demonstrated to realize a LED pumped organic laser. When the drive current is higher than 152 A, a sharp peak is clearly observed in the laser output spectrum, implying the LED successfully pumps the polymer laser above threshold. This is the first time an incoherent LED has been used as the excitation source for an organic semiconductor laser. A strategy for further improving the performance of the hybrid device is explored with the use of a luminescent concentrator made of a dye doped SU8 film, to intensify the power density from the inorganic LED. The luminescent concentrator is capable of increasing the incident power density by a factor of 9 and reducing the lasing threshold density by 4.5 times. As a preliminary investigation towards mode-locked polymer lasers, the impact of a solid state saturable absorber on a solution based organic semiconductor laser is explored. The dye doped polystyrene thin film saturable absorber exhibits a saturation intensity of a few MW/cm². When it is placed into the laser cavity, a train of short pulses is generated and the underlying mechanism is discussed. Finally, the potential of using organic semiconductor lasers in the detection of nitro-aromatic explosive vapours is studied in distributed feedback polyfluorene lasers. A high sensing efficiency and fast response from the laser prove polyfluorene lasers can be used as disposal and low cost devices in explosive chemosensing.

Polymer and organic electronic memory devices offer the potential for cheap, simple memories that could compete across the whole spectrum of digital memories, from low cost, low performance applications, up to universal memories capable of replacing all current market leading technologies, such as hard disc drives, random access memories and Flash memories. Polymer memory devices (PMDs) are simple, two terminal metal-insulator-metal (MIM) bistable devices that can exist in two distinct conductivity states, with each state being induced by applying different voltages across the device terminals. Currently there are many unknowns and much ambiguity concerning the working mechanisms behind many of these PMDs, which is impeding their development. This research explores some of these many unanswered questions and presents new experimental data concerning their operation. One prevalent theory for the conductivity change is based on charging and charge trapping of nanoparticles and other species contained in the PMD. The work in this research experimentally shows that gold nanoparticle charging is possible in these devices and in certain cases offers an explanation of the working mechanism. However, experimental evidence presented in this research, shows that in many reported devices the switching mechanism is more likely to be related to electrode effects, or a breakdown mechanism in the polymer layer. Gold nanoparticle charging via electrostatic force microscopy (EFM) was demonstrated, using a novel device structure involving depositing gold nanoparticles between lateral electrodes. This allowed the gold nanoparticles themselves to be imaged, rather than the nanoparticle loaded insulating films, which have previously been investigated. This method offers the advantages of being able to see the charging effects of nanoparticles without any influence from the insulating matrix and also allows charging voltages to be applied via the electrodes, permitting EFM images to capture the charging information in near real-time. Device characteristics of gold nanoparticle based PMDs are presented, and assessed for use under different scenarios. Configurations of memory devices based on metal-insulator-semiconductor (MIS) structures have also been demonstrated. Simple interface circuitry is presented which is capable of performing read, write and erase functions to multiple memory cells on a substrate. Electrical properties of polystyrene thin films in the nanometre thickness range are reported for the first time, with insulator trapped charges found to be present in comparable levels to those in silicon dioxide insulating films. The dielectric breakdown strength of the films was found to be significantly higher than bulk material testing would suggest, with a maximum dielectric strength of 4.7 MV•cm-1 found, compared with the manufacturers bulk value of 0.2 – 0.8 MV•cm-1. Conduction mechanisms in polystyrene were investigated with the dominant conduction mechanism found to be Schottky emission.

Ce travail porte sur la conception de nouveaux composés π-conjugués, potentiellement utilisable en électronique organique en tant que matériaux actifs dans des dispositifs tels que les OLEDs, les cellules photovoltaïques et les capteurs optiques. Dans ce but, nous avons exploité le motif silacyclopentadiène appelé également silole, possédant un bon rendement quantique de fluorescence à l'état solide et une excellente conduction des électrons. Dans un premier temps, l'introduction de groupements structurants (triptycène, stilbènes..) sur le silacyclopentadiène a permis de moduler l'arrangement moléculaire dans la couche active et par conséquent, les propriétés d'électroluminescence. Des diodes possédant des performances très encourageantes furent ainsi obtenues. Dans un deuxième temps, des dérivés siloles présentant une structure tridimensionnelle et une architecture spirosilole (accepteur)-bithiophène (donneur) furent synthétisées. Une cellule photovoltaïque basée sur ces édifices présentant des performances encourageantes fut ensuite mis au point. Enfin, l'étude des mécanismes de transfert d'énergie entre un film de polymère fonctionnalisé par un groupement sensible silole et des composés nitroaromatiques nous a permis de réaliser un nouveau type de capteur optique hautement sensible pour la détection d'explosifs. / This work concerns the design of new π-conjugated compounds, potentially useful in organic electronics as active materials in devices such as OLEDs, photovoltaic cells and optical sensors. To this end, silacyclopentadiene, alias silole, groups were used exhibiting high fluorescence quantum yields in the solid state and excellent electron conductivities. Firstly, the introduction of structurizing groups (triptycene, stilbenes etc.) at the silacyclopentadiene allowed tuning of the molecular arrangement in the active layer and, consequently, the electroluminescence properties. Diodes showing very encouraging activities were thus obtained. Secondly, silole derivatives possessing a three-dimensional structure and a spirosilole (acceptor) - bithiophene (donor) architecture were synthesized. A photovoltaic cell based on these molecules was then developed exhibiting encouraging activity. Finally, a study of the mechanisms of energy transfer between a polymer film functionalized by a sensitive silole group and nitroaromatic compounds enabled the development of a new type of highly sensitive optical sensor for the detection of explosives.

Chemisorption of an organic monolayer to tune the surface properties of a transparent conductive oxide (TCO) electrode can improve the performance of organic electronic devices that rely on efficient charge transfer between an organic active layer and a TCO contact. Here, a series of perylene diimides (PDIs) was synthesized and used to study relationships between monolayer structure/properties and electron transfer kinetics at PDI-modified indium-tin oxide (ITO) electrodes. In these PDI molecules, one of the imide substituents is a benzene ring bearing a phosphonic acid (PA) and the other is a bulky aryl group that is twisted out of the plane of the PDI core. The size of the bulky aryl group and the substitution of the benzene ring bearing the PA were both varied, which altered the extent of aggregation when these molecules were absorbed as monolayer films (MLs) on ITO, as revealed by both attenuated total reflectance (ATR) and total internal reflection fluorescence spectra. Polarized ATR measurements indicate that, in these MLs, the long axis of the PDI core is tilted at an angle of 33-42 degrees relative to the surface normal; the tilt angle increased as the degree of bulky substitution increased. Rate constants for electron transfer (k(s,opt)) between these redox-active modifiers and ITO were determined by potential-modulated ATR spectroscopy. As the degree of PDI aggregation was reduced, k(s,opt) declined, which is attributed to a reduction in the lateral electron self-exchange rate between adsorbed PDI molecules, as well as the heterogeneous conductivity of the ITO electrode surface. Photoelectrochemical measurements using a dissolved aluminum phthalocyanine as an electron donor showed that ITO modified with any of these PDIs is a more effective electron-collecting electrode than bare ITO.

In this work, a new condensed matter approach to the study of excitons based on crystalline thin films of the organic molecule phthalocyanine is introduced. The premise is inspired by a wealth of studies in inorganic semiconductor ternary alloys (such as AlGaN, InGaN, SiGe) where tuning compositional disorder can result in exciton localization by alloy potential fluctuations. Comprehensive absorption, luminescence, linear dichroism and electron radiative lifetime studies were performed on both pure and alloy samples of metal-free octabutoxy-phthalocyanine and transition metal octabutoxy-phthalocyanines, where the metal is Mn, Co, Ni, and Cu. Varying the ratios of the metal to metal-free phthalocyanines in all of these studies, as well as looking across a temperature range from 4 Kelvin up to room temperature is essential for quantifying the exciton wavefunction delocalization in crystalline thin films. A comparative study is performed across organic aromatic ringed molecules of different sizes in the same family: phthalocyanine, naphthalocyanine and tetra-phenyl porphyrin. In an analogy to nanocrystals and their size effects, variations in pi-conjugated ring sizes imply an altering in the number of delocalized electrons, impacting the wavefunction overlap between pi-pi orbitals along the perpendicular axis of neighboring molecules. Finally, complementary measurements that assess crystallinity of the in-house deposited thin films, including individual grain absorption, small angle x-ray scattering images, polarized microscope images and a new unique linear dichroism microscopy dual imaging/luminescence technique are also discussed.

Dispositivos baseados em eletrônica orgânica já estão presentes há vários anos no mercado com displays de OLEDs com alta definição de cores e contraste. Atualmente, essas telas são fabricadas com o uso de pequenas moléculas orgânicas depositadas por técnicas de evaporação a vácuo. A possibilidade de deposição dos materiais poliméricos em solução traz vantagens de fabricação com relação a custos e a velocidade de processamento, além de maiores escalas dimensionais. No entanto, diversos entraves técnicos ainda precisam ser superados para garantir desempenho e estabilidade de dispositivos eletrônicos e optoeletrônicos orgânicos. Neste sentido, este trabalho apresenta um equipamento de deposição roll-to-roll de proporções laboratoriais, com o intuito de servir de ponte entre o desenvolvimento acadêmico e as técnicas de produção industriais. Uma primeira versão do equipamento, já apresentado no trabalho de mestrado, foi agora modificado e atualizado com novas funcionalidades. Ele tornou-se mais completo e de operacionalidade mais eficiente, e foi utilizado para a deposição de várias camadas de dispositivos, incluindo a fabricação de eletrodos semitransparentes e da camada ativa de dispositivos luminescentes. Para solucionar as limitações do óxido de estanho e índio (principal condutor semitransparente atualmente) sobre substratos flexíveis, foi validado um eletrodo alternativo, através da síntese e aplicação de nanofios de prata e do polímero condutor PEDOT:PSS por diferentes técnicas de deposição. Também foi investigada a camada ativa de células eletroquímicas emissoras de luz (LEC), depositadas pela técnica slot-die, variando-se o polímero luminescente, de emissão azul, e o solvente utilizado. Por fim, foram fabricados dispositivos luminescentes do tipo LEC com diferentes arquiteturas e sobre diferentes substratos. O dispositivo final apresentado foi fabricado com eletrodos otimizados, depositados por spray com nanofios de prata e PEDOT:PSS, sendo os dois eletrodos semitransparentes. Com isso, obteve emissão em ambas as polaridades e em ambas as direções. / Devices based on organic electronics have been present for some years on the market with OLED displays with high color definition and contrast. Currently, these screens are manufactured using organic small molecules deposited by vacuum evaporation techniques. The possibility of deposition of polymeric materials in solution brings manufacturing advantages in terms of costs and processing speed, as well as larger dimensional scales. However, several technical barriers still need to be overcome to ensure performance and stability of organic electronic and optoelectronics devices. In this sense, this work presents roll-to-roll deposition equipment of laboratory proportions, in order to serve as a bridge between academic development and industrial production techniques. A first version of the equipment, already presented in the master\'s work, has now been modified and updated with new functionalities. It has become more complete and more operationally efficient, and has been used for the deposition of several layers of devices, including the manufacture of semitransparent electrodes and the active layer of luminescent devices. To solve the limitations of indium tin oxide (the main semitransparent conductor today) on flexible substrates, an alternative electrode was validated through the synthesis and application of silver nanowires and the PEDOT:PSS conductive polymer by different deposition techniques. It was also investigated the active layer of light-emitting electrochemical cells (LEC), deposited by the slot-die technique, varying the blue-emitting luminescent polymer and the solvent used. Finally, luminescent LEC devices were manufactured with different architectures and on different substrates. The final device presented was manufactured with optimized electrodes, deposited by spray with silver nanowires and PEDOT:PSS, the two electrodes being semi-transparent. With this, it obtained emission in both polarities and in both directions.

Dispositivos baseados em eletrônica orgânica já estão presentes há vários anos no mercado com displays de OLEDs com alta definição de cores e contraste. Atualmente, essas telas são fabricadas com o uso de pequenas moléculas orgânicas depositadas por técnicas de evaporação a vácuo. A possibilidade de deposição dos materiais poliméricos em solução traz vantagens de fabricação com relação a custos e a velocidade de processamento, além de maiores escalas dimensionais. No entanto, diversos entraves técnicos ainda precisam ser superados para garantir desempenho e estabilidade de dispositivos eletrônicos e optoeletrônicos orgânicos. Neste sentido, este trabalho apresenta um equipamento de deposição roll-to-roll de proporções laboratoriais, com o intuito de servir de ponte entre o desenvolvimento acadêmico e as técnicas de produção industriais. Uma primeira versão do equipamento, já apresentado no trabalho de mestrado, foi agora modificado e atualizado com novas funcionalidades. Ele tornou-se mais completo e de operacionalidade mais eficiente, e foi utilizado para a deposição de várias camadas de dispositivos, incluindo a fabricação de eletrodos semitransparentes e da camada ativa de dispositivos luminescentes. Para solucionar as limitações do óxido de estanho e índio (principal condutor semitransparente atualmente) sobre substratos flexíveis, foi validado um eletrodo alternativo, através da síntese e aplicação de nanofios de prata e do polímero condutor PEDOT:PSS por diferentes técnicas de deposição. Também foi investigada a camada ativa de células eletroquímicas emissoras de luz (LEC), depositadas pela técnica slot-die, variando-se o polímero luminescente, de emissão azul, e o solvente utilizado. Por fim, foram fabricados dispositivos luminescentes do tipo LEC com diferentes arquiteturas e sobre diferentes substratos. O dispositivo final apresentado foi fabricado com eletrodos otimizados, depositados por spray com nanofios de prata e PEDOT:PSS, sendo os dois eletrodos semitransparentes. Com isso, obteve emissão em ambas as polaridades e em ambas as direções. / Devices based on organic electronics have been present for some years on the market with OLED displays with high color definition and contrast. Currently, these screens are manufactured using organic small molecules deposited by vacuum evaporation techniques. The possibility of deposition of polymeric materials in solution brings manufacturing advantages in terms of costs and processing speed, as well as larger dimensional scales. However, several technical barriers still need to be overcome to ensure performance and stability of organic electronic and optoelectronics devices. In this sense, this work presents roll-to-roll deposition equipment of laboratory proportions, in order to serve as a bridge between academic development and industrial production techniques. A first version of the equipment, already presented in the master\'s work, has now been modified and updated with new functionalities. It has become more complete and more operationally efficient, and has been used for the deposition of several layers of devices, including the manufacture of semitransparent electrodes and the active layer of luminescent devices. To solve the limitations of indium tin oxide (the main semitransparent conductor today) on flexible substrates, an alternative electrode was validated through the synthesis and application of silver nanowires and the PEDOT:PSS conductive polymer by different deposition techniques. It was also investigated the active layer of light-emitting electrochemical cells (LEC), deposited by the slot-die technique, varying the blue-emitting luminescent polymer and the solvent used. Finally, luminescent LEC devices were manufactured with different architectures and on different substrates. The final device presented was manufactured with optimized electrodes, deposited by spray with silver nanowires and PEDOT:PSS, the two electrodes being semi-transparent. With this, it obtained emission in both polarities and in both directions.