Phosphorescent OLEDs (PHOLEDs) have gained a lot of attention due to their remarkable capability of achieving nearly 100% internal quantum efficiency. Although PHOLEDs are a promising technology for the development of high performance display panels and low power consumption lighting sources, their poor operational stability and efficiency decline at high current density (efficiency roll-off) limit their commercialization. Unlike Fluorescent OLEDs (FOLED) in which singlet excitons are responsible for the device emission, PHOLEDs utilize both singlet and triplet excitons for the emission. However, triplet excitons have much longer lifetime than their counterparts and they can be quenched by two bimolecular interactions (i.e. Triplet-Triplet Annihilation (TTA) and Triplet-Polaron Quenching (TPQ)). These two processes are of particular interests in PHOLEDs, since they directly compete with the radiative relaxation of triplet excitons and therefore, they can considerably reduce the device efficiency. The overall interest of this thesis is to identify and investigate the physical phenomena associated with the efficiency roll-off and electroluminescence degradation in PHOLEDs. This work particularly focuses on understanding the underlying mechanisms associated with TTA and TPQ and their roles in the efficiency roll-off and electroluminescence degradation through the study of delayed electroluminescence. It is found that efficiency loss due to TPQ is mainly caused by charges within the bulk of the emission layer (EML) rather than by charges at the hole transport layer (HTL)/EML interface. Charges on the guest rather than those on the host are found to be the most efficient in quenching excitons, revealing that guest polaronic species are the most detrimental to device efficiency. In addition, recombination of electrons and holes on the host material generally leads to higher device efficiency in comparison to the case where recombination happens on the guest material. Although electron-hole recombination on the host tends to produce higher device efficiency, host e-h recombination is generally also associated with significant efficiency roll-off due to the quenching of the host triplet excitons primarily as a result of host-host TTA. Furthermore, results from the study of devices with various guest concentrations reveals that as the concentration of the guest molecules increases and the creation of host triplet excitons subsides (since most e-h recombination occurs on the guest) host-host TTA decreases, hence also the efficiency roll-off. In such case, quenching is mostly caused by polarons residing on guest sites. At optimum guest concentrations (~8 % Vol.), a balance between host e-h recombination and guest e-h recombination is reached, and thus also minimal TTA and TPQ. Based on the findings from the investigation of efficiency roll-off during short-term device operation, we extended our study to understand the mechanisms associated with the gradual efficiency loss in the devices during long-term operation. Two distinctive degradation mechanisms are observed in PHOLEDs, depending on whether the device contains a hole blocking layer (HBL) or not. For a device without a HBL, excess holes penetrate into the electron transport layer (ETL), and lead to the deterioration of the ETL adjacent to the interface of the emitting layer. The lower electron transport capacity of the degraded ETL alters the balance in hole/electron injection into the emitting layer, and results in a decrease in the luminescence efficiency of the PHOLEDs. For a device with a HBL, on the other hand, holes accumulate and become trapped in the emitting layer, and result in a decrease in the luminescence efficiency of the PHOLEDs, due to their role in acting as exciton quenchers or as non-radiative charge recombination centers. Furthermore, the results show a strong correlation between the extent of hole blockage capacity of the HBL and the deterioration in device EL efficiency, pointing to the major role that the build-up of hole space charges in the emitting layer plays in EL degradation. In this case, gradual increase of trapped charges in the EML enhances the TPQ process and hence exciton quenching manifesting as a reduction of TTA. In addition, gradual increase in driving voltage often observed with prolonged electrical driving of PHOLEDs is mainly governed by the accumulation of holes at this interface. Reducing the build-up of hole space charges in this region, for example, by means of eliminating guest molecules from the vicinity of the interface, leads to a significant improvement in the stability of PHOLED driving voltage.

The research field of organic electronics experiences tremendous developments since the discovery of conducting polymers upon chemical doping and the developments of applications where organic materials replace the traditionally used inorganic semiconductors. Devices such as light-emitting diodes (OLEDs), solar cells, and field-effect transistors (OFETs) based on organic ð-conjugated materials as active materials represent the key applications of the domain. In OLEDs, charge carriers (holes and electrons) are injected from the electrodes into the organic semiconductor and emit light when they meet. Solar cells have an opposite working principle compared to OLEDs: light is absorbed and dissociated in charge carriers that migrate to the electrodes to give rise to an electric current. OFET plays the role of current modulator in electronic circuits by tuning the current flowing in its channel. The gain of better device performances (better conversion efficiency for OLEDs and solar cells or high ON/OFF ratios for OFETs) requires a better understanding at a molecular scale of the charge transport properties that are quantified at the experimental level by the charge carrier mobility ì. Since organic conjugated materials are typically disordered, the charge carriers are mostly localized over a single molecule and charge transfers between molecules occur via a hopping mechanism. In our Ph.D. thesis, we have characterized the charge transport properties at the molecular scale by calculating the parameters entering into the Marcus hopping rate by means of semi-empirical Hartree-Fock methods and Density Functional Theory (DFT) calculations. On that basis, we have propagated a single charge carrier in molecular assemblies by means of a Dynamic Monte-Carlo procedure that we have developed in order to estimate mobility values as the ratio of the total distance travelled by the charge divided by the product of the total time needed to travel that distance and the norm of the electric field. The systems under study were model one-dimensional array of pentacene molecules, single molecular crystals and structures simulated by Molecular Dynamics (liquid crystalline phthalocyanine derivatives) and by Molecular Mechanics (grain boundaries in pentacene layers). The principle results shows anisotropic behaviour and electric field dependence for the charge carrier mobility, the impact of energetic as well as the positional disorder on the charge migration were investigated and we emphasize the importance to describe both disorders at a molecular scale in order to get a reliable picture for the charge transport properties calculations.

Phosphorescent OLEDs (PHOLEDs) have gained a lot of attention due to their remarkable capability of achieving nearly 100% internal quantum efficiency. Although PHOLEDs are a promising technology for the development of high performance display panels and low power consumption lighting sources, their poor operational stability and efficiency decline at high current density (efficiency roll-off) limit their commercialization. Unlike Fluorescent OLEDs (FOLED) in which singlet excitons are responsible for the device emission, PHOLEDs utilize both singlet and triplet excitons for the emission. However, triplet excitons have much longer lifetime than their counterparts and they can be quenched by two bimolecular interactions (i.e. Triplet-Triplet Annihilation (TTA) and Triplet-Polaron Quenching (TPQ)). These two processes are of particular interests in PHOLEDs, since they directly compete with the radiative relaxation of triplet excitons and therefore, they can considerably reduce the device efficiency. The overall interest of this thesis is to identify and investigate the physical phenomena associated with the efficiency roll-off and electroluminescence degradation in PHOLEDs. This work particularly focuses on understanding the underlying mechanisms associated with TTA and TPQ and their roles in the efficiency roll-off and electroluminescence degradation through the study of delayed electroluminescence. It is found that efficiency loss due to TPQ is mainly caused by charges within the bulk of the emission layer (EML) rather than by charges at the hole transport layer (HTL)/EML interface. Charges on the guest rather than those on the host are found to be the most efficient in quenching excitons, revealing that guest polaronic species are the most detrimental to device efficiency. In addition, recombination of electrons and holes on the host material generally leads to higher device efficiency in comparison to the case where recombination happens on the guest material. Although electron-hole recombination on the host tends to produce higher device efficiency, host e-h recombination is generally also associated with significant efficiency roll-off due to the quenching of the host triplet excitons primarily as a result of host-host TTA. Furthermore, results from the study of devices with various guest concentrations reveals that as the concentration of the guest molecules increases and the creation of host triplet excitons subsides (since most e-h recombination occurs on the guest) host-host TTA decreases, hence also the efficiency roll-off. In such case, quenching is mostly caused by polarons residing on guest sites. At optimum guest concentrations (~8 % Vol.), a balance between host e-h recombination and guest e-h recombination is reached, and thus also minimal TTA and TPQ. Based on the findings from the investigation of efficiency roll-off during short-term device operation, we extended our study to understand the mechanisms associated with the gradual efficiency loss in the devices during long-term operation. Two distinctive degradation mechanisms are observed in PHOLEDs, depending on whether the device contains a hole blocking layer (HBL) or not. For a device without a HBL, excess holes penetrate into the electron transport layer (ETL), and lead to the deterioration of the ETL adjacent to the interface of the emitting layer. The lower electron transport capacity of the degraded ETL alters the balance in hole/electron injection into the emitting layer, and results in a decrease in the luminescence efficiency of the PHOLEDs. For a device with a HBL, on the other hand, holes accumulate and become trapped in the emitting layer, and result in a decrease in the luminescence efficiency of the PHOLEDs, due to their role in acting as exciton quenchers or as non-radiative charge recombination centers. Furthermore, the results show a strong correlation between the extent of hole blockage capacity of the HBL and the deterioration in device EL efficiency, pointing to the major role that the build-up of hole space charges in the emitting layer plays in EL degradation. In this case, gradual increase of trapped charges in the EML enhances the TPQ process and hence exciton quenching manifesting as a reduction of TTA. In addition, gradual increase in driving voltage often observed with prolonged electrical driving of PHOLEDs is mainly governed by the accumulation of holes at this interface. Reducing the build-up of hole space charges in this region, for example, by means of eliminating guest molecules from the vicinity of the interface, leads to a significant improvement in the stability of PHOLED driving voltage.

Cette thèse est dédiée à la modélisation et à la compréhension du fonctionnement de dispositifs organiques et plus particulièrement des diodes organiques. Tout d'abord, nous avons modélisé et analysé les caractéristiques courant-tension en mode statique de dispositifs planaire (diodes) ou longitudinaux (barreaux résistifs) à base de TIPS-pentacene. Nous avons pu ainsi expliquer l'origine du redressement en courant pour ce type de dispositifs à base de semi-conducteur non-dopé. L'aspect dynamique a ensuite été pris en compte, avec la proposition d'un modèle numérique et d'un modèle analytique simplifié du comportement en temporel de la diode, ce qui a permis de déterminer quels sont les paramètres physiques impactant la fréquence de coupure. Enfin, compte tenu de l'intérêt grandissant des photodiodes organiques, nous nous intéresserons également dans la dernière partie à la modélisation de la diode sous flux lumineux, pour des applications en tant que cellules solaire ou des photodétecteurs. Nous étudierons dans cette dernière partie l'impact des paramètres électriques et optiques du dispositif (épaisseur, mobilité, taux de dissociation des excitons, indice optique, etc.) sur les courants d'obscurité et sous illumination, et donc les rendements de conversion. / This report is dedicated to the modelling and understanding of organic devices functionement and more particularly to organic diodes. First, we modelled and analysed I-V caracterisations of planar (diodes) and longitudinal (resistive sticks) devices made with TIPS-pentacene. We could explain the reason of the rectifying behavior of devices based on undoped semiconductor. The dynamic aspect was then analysed with the help of a numerical model which was simplifyed in a semi-analytical one. This allowed us to find parameters who have an impact on the cutoff frequency. Finally, as there is a growing interest on organic photodiodes whose applications are organic photodetectors or solar cells, we modellised, in the last part, the impact of light on the functionnement of organic diodes. We studyed the impact of both electrical parameters and optical ones (thicknesses, mobility, dissociations rate of excitons, optical indexes, etc...) on dark current and under illumination.

Organic thin film transistors (TFT) are an attractive option for low cost electronic applications and may be used for active matrix displays and for RFID applications. To extend the range of applications there is a need to develop and optimise the performance of non-volatile memory devices that are compatible with the solution-processing fabrication procedures used in plastic electronics. A possible candidate is an organic TFT incorporating the ferroelectric co-polymer poly(vinylidenefluoride-trifluoroethylene)(P(VDF-TrFE)) as the gate insulator. Dielectric measurements have been carried out on all-organic metal-insulator-semiconductor structures with the ferroelectric polymer poly(vinylidenefluoride-trifluoroethylene) (P(VDF-TrFE)) as the gate insu-lator. The capacitance spectra of MIS devices, were measured under different biases, showing the effect of charge accumulation and depletion on the Maxwell-Wagner peak. The position and height of this peak clearly indicates the lack of stable depletion behavior and the decrease of mobility when increasing the depletion zone width, i.e. upon moving into the P3HT bulk. The lack of stable depletion was further investigated with capacitance-voltage (C-V) measurements. When the structure was driven into depletion, C-V plots showed a positive flat-band voltage shift, arising from the change in polarization state of the ferroelectric insulator. When biased into accumulation, the polarization was reversed. It is shown that the two polarization states are stable i.e. no depolarization occurs below the coercive field. However, negative charge trapped at the semiconductor-insulator interface during the depletion cycle masks the negative shift in flat-band voltage expected during the sweep to accumulation voltages. The measured output characteristics of the studied ferroelectric-field-effect transistors confirmed the results of the C-V plots. Furthermore, the results indicated a trapping of electrons at the positively charged surfaces of the ferroelectrically polarized P(VDF-TrFE) crystallites near the insulator/semiconductor in-terface during the first poling cycles. The study of the MIS structure by means of thermally stimulated current (TSC) revealed further evidence for the stability of the polarization under depletion voltages. It was shown, that the lack of stable depletion behavior is caused by the compensation of the orientational polarization by fixed electrons at the interface and not by the depolarization of the insulator, as proposed in several publications. The above results suggest a performance improvement of non-volatile memory devices by the optimization of the interface. / Organische Transistoren sind besonders geeignet für die Herstellung verschiedener preisgünstiger, elektronischer Anwendungen, wie zum Beispiel Radio-Frequenz-Identifikations-Anhänger (RFID). Für die Erweiterung dieser Anwendung ist es notwendig die Funktion von organischen Speicherelementen weiter zu verbessern. Das ferroelektrische Polymer Poly(vinylidene-Fluoride-Trifluoroethylene) (P(VDF-TrFE)) eignet sich besonders gut als remanent polarisierbarer Isolator in Dünnschich-Speicherelementen. Um Schalt- und Polarisationsverhalten solcher Speicherelemente zu untersuchen, wurden P(VDF-TrFE)-Kondensatoren und Metall-Halbleiter-Isolator-Proben sowie ferroelektrische Feld-Effekt-Transistoren (Fe-FET) aus dem Halbleiter Poly(3-Hexylthiophene) (P3HT) und P(VDF-TrFE) hergestellt und dielektrisch untersucht. Die Charakterisierung der MIS-Strukturen mittels spannungsabhängiger Kapazitätsspektren machte deutlich, dass es nicht möglich ist, einen stabilen Verarmungzustand (Aus-Zustand) zu realisieren. Kapazität-Spannungs-Messungen (C-V) an MIS-Proben mit uni/bi-polaren Spannungszyklen zeigten eine stabile ferroelektrische Polarisation des P(VDF-TrFE)-Films. Eine Depolarisation des Isolators durch den Mangel an Minoritäts-Ladungsträgern konnte als Grund für die Instabilität des Verarmungs-Zustandes ausgeschlossen werden. Die C-V-Kurven wiesen vielmehr auf die Existenz fixierter, negativer Ladungsträger an der Grenzfläche hin. Zusammenfassend kann festgestellt werden: die Ursache der Ladungsträgerinstabilitäten in organischen ferroelektrischen Speicherelementen ist auf die Kompensation der ferroelektrischen Orientierungspolarisation durch "getrappte"(fixierte) negative Ladungsträger zurückzuführen. Dieses Ergebnis liefert nun eine Grundlage für die Optimierung der Isolator/Halbleiter-Grenzfläche mit dem Ziel, die Zahl der Fallenzustände zu minimieren. Auf diesem Wege könnte die Stabilität des Speicherzustandes in organischen Dünnschichtspeicherelementen deutlich verbessert werden.

Biosensors based on solid-state field-effect transistor as transducer stage using organic semiconducting materials as sensing stage have been developed. Polyaniline thin films galvanostatic electrodeposited were fabricated. Varied electrodeposition parameters were tested, such as deposited charge, current density, deposition time and monomer concentration, besides the tests of a polymeric blend composed of polyaniline and polypyrrole and tested as pH potentiometric extended gate field-effect transistor sensor. Then, biosensors were produced using the one-step electrochemical immobilization process to obtain thin polyaniline films with entrapped glucose oxidase and urease enzymes, to detection of glucose and urea, respectively. The optimized films presented sensitivity, linearity and detection range to glucose of 14.6 ± 0.4 mV/decade, 99.8 % and from 10-4 mol/L to 10-1 mol/L. Two different biosensors were produced based on the enzymatic catalysis of urea with selectivity to ammonium or hydroxyl ions. For ammonium ion selective films, the sensor presented sensitivity, linearity and detection range of 14.7 ± 0.9 mV/decade, 98.2 % and from 10-5 mol/L to 10-1 mol/L. For the hydroxyl ion selective film, the same parameters were 7.4 ± 0.5 mV/decade, 98.1 % and from 10-5 mol/L to 10-1 mol/L. The same functionalized polyaniline thin films were used in optical and conductometric biosensors due to the polyelectrochromic characteristic of the material. Improvement of the field-effect system was possible with the multimodal array of enzymatic biosensor. The device was built using different enzymatic sensing stages connected to the extended gate field effect transistor. The system decreased the time needed to make distinct measurements, showed good response to the variation in solutions pH, to the presence of the reference film and to injection of target analyte in solution in real time measurement. The electrolyte gated organic field-effect transistor based on a polythiophene organic semiconducting layer was developed. A modular enzymatic biosensor for glucose and urea, with a linear response in the range between 10-6 and 10-3 mol/L, was achieved. This biosensor relies on the immobilization the enzymes on gold rods, used as gate electrodes in the devices. The use of the bioreceptors proved to be selective and cross-selective in the devices. The possibility of exchanging the modified gate electrode to detect specific analytes using the same device system allows the modular sensor to be reused and applied for a broad range of applications. Which is the case for explosives molecules, TNT and DNT, biosensor fabricated in the same terms. This biosensor relies on the immobilization of specific binding peptides for TNT and DNT on the gold rod / Biossensores do estado sólido baseados em transistores de efeito de campo como estágio transdutor fabricados com materiais semicondutores orgânicos como estágio de detecção foram desenvolvidos. Filmes finos de polianilina eletrodepositados galvanostaticamente foram fabricados. Parâmetros de eletrodeposição foram testados, como carga depositada, densidade de corrente, tempo de deposição e concentração de monômero, além de testes com compósito polimérico de polianilina e polipirrol e aplicados como sensor de transistor de efeito de campo de porta estendida potenciométrica de pH. Em seguida, os biossensores foram produzidos utilizando-se o processo de imobilização eletroquímica conjunta para obtenção de filmes finos de polianilina com enzimas glicose oxidase e urease imobilizadas, para detecção de glicose e ureia, respectivamente. Os filmes otimizados apresentaram sensibilidade, linearidade e faixa de detecção para glicose de 14,6 ± 0,4 mV/década, 99,8% e de 10-4 a 10-1 mol/L. Dois biossensores diferentes foram produzidos a partir da catálise enzimática da ureia com seletividade para íons amônio ou hidroxila. Para filmes seletivos ao íon amônio, o sensor apresentou sensibilidade, linearidade e faixa de detecção de 14,7 ± 0,9 mV/década, 98,2% e de 10-5 a 10-1 mol/L. Para o filme seletivo ao íon hidroxila, os mesmos parâmetros foram 7,4 ± 0,5 mV/década, 98,1% e de 10-5 a 10-1 mol/L. Os mesmos filmes finos de polianilina funcionalizados foram utilizados em biossensores ópticos e condutométricos devido à característica polieletrocromática do material. A melhoria do sistema foi possível com o arranjo multimodal do biossensor enzimático. O dispositivo foi construído usando diferentes estágios de detecção enzimática conectados ao transistor de efeito de campo de porta estendido. O sistema diminuiu o tempo necessário para fazer medições distintas, mostrou boa resposta à variação no pH da solução, à presença do filme de referência e à injeção do analito alvo em solução na medição em tempo real. Foi desenvolvido o transistor orgânico de efeito de campo com porta eletrolítica, baseado em uma camada semicondutora orgânica de politiofeno. Um biossensor enzimático modular para glicose e ureia, com uma resposta linear na faixa entre 10-6 e 10-3 mol/L, foi alcançado. Este biossensor depende da imobilização das enzimas no eletrodo ouro utilizado como porta nos dispositivos. O uso dos bioreceptores mostrou-se seletivo nos dispositivos. A possibilidade de trocar o eletrodo de porta modificada para detectar analitos específicos usando o mesmo sistema de dispositivos permite que o sensor modular seja reutilizado e com diversas aplicações. Sendo este o caso de moléculas de explosivos, TNT e DNT, com biossensor fabricado nos mesmos termos. Este biossensor depende da imobilização de peptídeos de ligação específica para TNT e DNT no eletrodo de ouro

Submitted by Ricardo Magno Lopes da Silva (ricardo.magnolopes@gmail.com) on 2019-01-23T12:18:26Z No. of bitstreams: 1 Dissertação_Ricardo Magno Lopes da Silva.pdf: 5243589 bytes, checksum: 569fbcb2d89d81df48d323d3c812340b (MD5) / Approved for entry into archive by Lucilene Cordeiro da Silva Messias null (lubiblio@bauru.unesp.br) on 2019-01-24T12:27:59Z (GMT) No. of bitstreams: 1 silva_rml_me_bauru.pdf: 5243589 bytes, checksum: 569fbcb2d89d81df48d323d3c812340b (MD5) / Made available in DSpace on 2019-01-24T12:27:59Z (GMT). No. of bitstreams: 1 silva_rml_me_bauru.pdf: 5243589 bytes, checksum: 569fbcb2d89d81df48d323d3c812340b (MD5) Previous issue date: 2018-12-04 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A técnica de autoenrolamento de nanomembrana foi utilizada neste trabalho para a fabricação de capacitores ultracompactos (UCCap), permitindo a caracterização de filmes finos de materiais orgânicos e híbridos. O método é conhecido como roll-up, e consiste na formação de uma nanomembrana tensionada, elaborada a fim de produzir estruturas autosustentadas, que promovem o enrolamento do sistema ao serem libertadas de um substrato, determinando uma arquitetura em 3D. Neste trabalho, a tecnologia de nanomembranas foi utilizada com o objetivo de determinar as propriedades elétricas e dielétricas, sob diferentes temperaturas, de camadas de moléculas semicondutoras (CoPc, CuPc e F16CuPc) e de camadas de estruturas híbridas metal-orgânicas (HKUST-1). A caracterização desses materiais em nanoescala foi possível por meio de sua incorporação em UCCap. Os dispositivos foram caracterizados por medidas de espectroscopia de impedância e corrente elétrica. Em filmes finos das ftalocianinas (= 5 nm) na temperatura ambiente (≈ 296 K), foram encontrados valores de 2,1 ± 0,5 para a constante dielétrica da CoPc (kCoPc), 3,1 ± 0,6 para a CuPc (kCuPc) e 1,2 ± 0,6 para F16CuPc (kF16CuPc). As propriedades elétricas / dielétricas dos filmes das ftalocianinas foram analisadas sob diferentes temperaturas e filmes de CoPc foram explorados na presença de campos magnéticos aplicados com valores de magnitude entre - 500 e + 500 mT. As camadas de HKUST-1 incorporadas ao UCCap possibilitaram a determinação do valor de 3,2 ± 1,6 para sua constante dielétrica (kHKUST-1) à ≈ 296 K. Os valores encontrados para os materiais estudados como camada dielétrica em capacitor no estado-sólido são condizentes com valores encontrados na literatura, determinados nas mesmas condições de temperatura a partir de outros métodos de caracterização. O alto valor de incerteza do cálculo se deve ao pequeno espaço amostral utilizado até então. Foi constatado que a estratégia relatada consiste em uma metodologia adequada para determinação de algumas propriedades de filmes finos orgânicos e híbridos, com potencial para aplicação no estudo de outros materiais em escalas nanométricas. / The rolled-up nanomembrane-based technique was used in this work to the manufacture of ultracompact capacitors (UCCap), allowing the characterization of thin films of organic and hybrid materials. The method, known as roll-up, consists in the formation of a strained nanomembrane, elaborated in order to produce self-supported structures that promote the winding of the system when released from a substrate, determining a 3D architecture. In this work, the nanomembrane technology was used to determine the electrical and dielectric properties, for different conditions of temperatures, in layers of semiconductor molecules (CoPc, CuPc and F16CuPc) and layers of hybrid metal-organic structures (HKUST-1). The characterization of these materials at nanoscale was possible by their incorporation into UCCap. Current-voltage and impedance spectroscopy measurements were used to characterize the devices. For thin films of the phthalocyanines (= 5 nm) at room temperature (≈ 296 K), values of 2,1 ± 0,5 were found for CoPc dielectric constant (kCoPc), 3,1 ± 0,6 for CuPc (kCoPc) and 1,2 ± 0,6 for F16CuPc (kF16CoPc). The electrical / dielectric properties of the phthalocyanine films were analyzed under different temperatures and CoPc films were screened in the presence of applied magnetic fields with magnitude values between - 500 and + 500 mT. The HKUST-1 layers incorporated into the UCCap allowed the determination of a value of 3,2 ± 1,6 for its dielectric constant (kHKUST-1) at ≈ 296 K. The values found for the materials studied as dielectric layer of a solid-state capacitor are consistent with values found in literature, determined in the same temperature conditions yet by other characterization methods. The high uncertainty value of the calculation is due to the small number of samples explored until then. It was verified that the reported strategy consists an adequate methodology for determination of some properties of organic and hybrid thin films, with potential for application in the study of other materials in nanometric scales. / 88882.143501/2017-01

Para que a tecnologia de eletrônica orgânica alcance todo o seu potencial é primordial que o processo de fabricação seja rápido e barato, e uma das maneiras de alcançar isto é com a utilização de processos gráficos especialmente adaptados para a produção de eletrônica, processo esse conhecido por roll-to-roll. Uma grande carência mundial se encontra em equipamentos de produção roll-to-roll de porte laboratorial, que possam ser utilizados para estudos de construção dos dispositivos e, mais importante, a transferência das tecnologias desenvolvidas em laboratório para processos que possam ser facilmente expandidos para a indústria. Neste sentido, durante este trabalho foi desenvolvido um sistema roll-to-roll compacto para produção e estudo de dispositivos orgânicos que apresenta as técnicas de deposição por rotogravura, wire-bar e knife-over-edge comutáveis, sendo empregada uma técnica por vez. O equipamento foi projetado e fabricado de forma a permitir a maior quantidade possível de ajustes das variáveis, com um pequeno consumo de material polimérico e de substrato. Além disto, desenvolveu-se um software de controle operado empregando-se o programa LabVIEW para regulagem da temperatura de secagem, velocidades do substrato e impressão. Como primeiro dispositivo fabricado optou-se por células eletroquímicas emissoras de luz (PLEC) por estas apresentarem baixa tensão de operação e uma baixa influência da espessura e dos eletrodos em suas propriedades optoeletrônicas. Desta forma, foi produzido um dispositivo luminescente sobre papel alumínio, flexível, de baixo custo, sem ITO e todo fabricado no equipamento roll-to-roll aqui desenvolvido. Além disto, o processo foi projetado para ser executado no ambiente, isto é, sem etapas que necessitem vácuo ou atmosfera controlada. Estes dispositivos comprovaram a aplicabilidade do sistema desenvolvido para a produção e desenvolvimento da eletrônica orgânica em laboratório visando a produção industrial final. / To develop the entire potential of Organic Electronic (OE) industry, it is necessary to generate processing methods that include high speed production at low cost. One technique that is emerging as very promising is that known as roll-to-roll. Despite the existence of several roll-to-roll machinery in the market, a small prototype that can be used in laboratories certainly will be very useful for research and as first experiments for production. In this work, we developed a compact roll-to-roll system devoted specifically to the production of printable electronic devices. In particular, this machine disposes deposition techniques as rotogravure, wire-bar and knife-over-edge. It is a versatile machine, which allows the operation of several technical parameters, using a relatively low amount of polymer material and substrate. In addition, we developed a numerical control system that is operated by a computer trough a LabWIEW program. This regulates the drying temperature and the substrate speed, parameters of fundamental importance for a good printed product. As first test we opted for building a coated Light Emitting Electrochemical Cell (PLEC), which are optoelectronic devices that uses relatively low operation voltage and does not exhibit critical thickness dependence. We printed this low cost and flexible device onto aluminum paper, then avoiding any other process and the use of ITO. All the coating processing was carried out in environmental conditions, being not necessary vacuum or accurate control of atmosphere. This application gives a strong evidence that this compact roll-to-roll machine presents a good performance in the fabrication of organic optoelectronic devices, being adequate for research and as guide for industrial production.

In this dissertation, the multiple facets of benzodithiophene (BDT) units are explored, with a focus on understanding how the isomerism of the BDT structure affects the macroscopic properties of the oligomeric and polymeric materials created. First, the story focuses on an overview of the BDT synthons and their applications in organic electronics. A straightforward synthesis of BDT and its derivatization to seven π-conjugated building blocks and seven polymers is presented. Then, symmetric (donor)2-acceptor (D2-A) dye architecture for application in dye-sensitized solar cells are investigated. Two isomeric systems are studied, and the branched sensitizers show a greater incident photon-to-current efficiency than the linear dyes. The nature of the accepting core is also varied between dibenzophenazine to dithienophenazine. The sensitizer with the weakest accepting core displays the best photovoltaic performance, due to an increase in the open-circuit voltage of ~100 mV caused by the favorable shift of the metal oxide conduction band. Lastly, a study of the donating building blocks in these (D2-A) sensitizers demonstrates that increasing the number of donor units from two to six thiophene moiety doubles the solar cell performance, due to the improvement of the light harvesting ability.

Since their discovery, organic electronic materials have been of great interest as an alternative active layer material for active area materials in electronic applications. Initially studied as probes or lasing material the field has progressed to the point where both conjugated polymers and small organics have become fashionable objects of current device oriented solid state research. Organic electronic materials are liquid crystalline materials, packing into well-ordered domains when annealed thermally or via solvent annealing. The macromolecular orientation of the molecules in the solid state causes a shift in the electronic properties due to coupling of the dipoles. The amount of interaction between molecules can be correlated to different nanoscale morphologies. Such morphologies can be measured using microscopy techniques and compared to the spectroscopic results. This can then be extrapolated out to infer how the charges move within a film. Cyanine dyes represent an interesting form class of dyes as the molecular packing is strongly affected by hydrophilic and hydrophobic pendent groups, which cause the dye to arrange into a tubular bilayer. Spectroelectrochemistry is used to monitor and controllably oxidize the samples. Using singular value decomposition (SVD) it is possible to extract each electronic species formed during electrochemical oxidation and model the proposed species using semi empirical quantum mechanical calculations. Polyfluorene is a blue luminescent polymer of interest for its high quantum yield. The solution and solid-state conformation has shown two distinct phases. The formation of the secondary phase shows a dependence on the molecular weight. In a poor solvent, as the molecular weight increases, the secondary phase forms easier. In the solid state, the highly efficient blue emission from polyfluorene is degraded by ketone defects. The energy transfer to preexisting ketone defects is increased as the filmed is thermally ordered. Glass transitions of block copolymers are studied using synthetically novel polymers where an environmentally sensitive fluorescent reporter is placed within various regions of a self-assembled film. Different dynamics are observed within the block of the film then specifically at the interface of two blocks. / text