Acceptor copolymers with low lowest unoccupied molecular orbital (LUMO) energy levels are key materials for organic electronics. In the present work, quaternization of pyridine-flanked diketopyrrolopyrrole (PyDPPPy) is used to lower the LUMO energy level of the resulting monomer (MePyDPPPy) by as much as 0.7 eV. The drastically changed electronic properties of MePyDPPPy hinder a second methylation step even in an excess of trimethyloxonium tetrafluoroborate and thereby give access to the asymmetric functionalization of N-heterocycle-flanked DPP building blocks. The corresponding n-type polymeric ionene PMePyDPPPyT2 with bithiophene as comonomer forms thixotropic organogels with the p-type polythiophene P(g42T-TT), indicative of specific cross-interactions between this couple of copolymers. Gelation of polymer blend solutions, which is absent for other couples of p-type/ n-type polymers, is of general interest for (co)processing and orientation of different electronic polymers simultaneously into films or filaments. Detailed optical and electronic characterization reveals that films processed from organogels exhibit ground-state electron transfer (GSET) enabled by suitably positioned highest occupied molecular orbital (HOMO) and LUMO energy levels of P(g42T-TT) (−4.07 eV) and PMePyDPPPyT2 (−4.20 eV), respectively. Furthermore, molecular interactions related to gelation and GSET do not appear to significantly influence the morphology of the polymer blend films.

Organic π-conjugated solids are promising candidates for new optoelectronic materials. The large body of evidence points at their advantageous properties such as high charge-carrier mobility, large nonlinear polarizability, mechanical flexibility, simple and low cost fabrication and superior luminescence. They can be used as nonlinear optical (NLO) materials with large two-photon absorption (2PA) and as electronic components capable of generating nonlinear neutral (excitonic) and charged (polaronic) excitations. In this work, we investigate the appropriate theoretical methods used for the (a) prediction of 2PA properties for rational design of organic materials with improved NLO properties, and (b) understanding of the essential electronic excitations controlling the energy-transfer and charge-transport properties in organic optoelectronics. Accurate prediction of these electro-optical properties is helpful for structureactivity relationships useful for technological innovations. In Chapter 1 we emphasize on the potential use of the organic materials for these two applications. The 2PA process is advantageous over one-photon absorption for deep-tissue fluorescence microscopy, photodynamic therapy, microfabrication and optical data storage owing to the three-dimensional spatial selectivity and improved penetration depth in the absorbing or scattering media. The design of the NLO materials with large 2PA cross-sections may reduce the optical damage due to the use of the high intensity laser beams for excitation. The organic molecules also possess self-localized excited states which can decay radiatively or nonradiatively to form excitonic states. This suggests the use of these materials in the electroluminescent devices such as light-emitting diodes and photovoltaic cells through the processes of exciton formation or dissociation, respectively. It is therefore necessary to understand ultrafast relaxation processes required in understanding the interplay between the iv efficient radiative transfer between the excited states and exciton dissociation into polarons for improving the efficiency of these devices. In Chapter 2, we provide the detailed description of the various theoretical methods applied for the prediction as well as the interpretation of the optical properties of a special class of substituted PPV [poly (p-phenylene vinylene)] oligomers. In Chapter 3, we report the accuracy of different second and third order time dependent density functional theory (TD-DFT) formalisms in prediction of the 2PA spectra compared to the experimental measurements for donor-acceptor PPV derivatives. We recommend a posteriori Tamm-Dancoff approximation method for both qualitative and quantitative analysis of 2PA properties. Whereas, Agren's quadratic response methods lack the double excitations and are not suitable for the qualitative analysis of the state-specific contributions distorting the overall quality of the 2PA predictions. We trace the reasons to the artifactual excited states above the ionization threshold. We also study the effect of the basis set, geometrical constraints and the orbital exchange fraction on the 2PA excitation energies and cross-sections. Higher exchange (BMK and M05-2X) and range-separated (CAM-B3LYP) hybrid functionals are found to yield inaccurate predictions both quantitatively and qualitatively. The failure of the exchangecorrelation (XC) functionals with correct asymptotic is traced to the inaccurate transition dipoles between the valence states, where functionals with low HF exchange succeed. In Chapter 4, we test the performance of different semiempirical wavefunction theory methods for the prediction of 2PA properties compared to the DFT results for the same set of molecules. The spectroscopic parameterized (ZINDO/S) method is relatively better than the general purpose parameterized (PM6) method but the accuracy is trailing behind the DFT methods. The poor performances of PM6 and ZINDO/S methods are attributed to the incorrect description of excited-to-excited state transition and 2PA energies, respectively. The different v semiempirical parameterizations can at best be used for quantitative analysis of the 2PA properties. The ZINDO/S method combined with different orders of multi-reference configuration interactions provide an improved description of 2PA properties. However, the results are observed to be highly dependent on the specific choice for the active space, order of excitation and reference configurations. In Chapter 5, we present a linear response TD-DFT study to benchmark the ability of existing functional models to describe the extent of self-trapped neutral and charged excitations in PPV and its derivative MEH-PPV considered in their trans-isomeric forms. The electronic excitations in question include the lowest singlet (S1) and triplet (T1 † ) excitons, positive (P+ ) and negative (P- ) polarons and the lowest triplet (T1) states. Use of the long-range-corrected DFT functional, such as LC-wPBE, is found to be crucial in order to predict the physically correct spatial localization of all the electronic excitations in agreement with experiment. The inclusion of polarizable dielectric environment play an important role for the charged states. The particlehole symmetry is preserved for both the polymers in trans geometries. These studies indicate two distinct origins leading to self-localization of electronic excitations. Firstly, distortion of molecular geometry may create a spatially localized potential energy well where the state wavefunction self-traps. Secondly, even in the absence of geometric and vibrational dynamics, the excitation may become spatially confined due to energy stabilization caused by polarization effects from surrounding dielectric medium. In Chapter 6, we aim to separate these two fundamental sources of spatial localization. We observe the electronic localization of P + and Pis determined by the polarization effects of the surrounding media and the character of the DFT functional. In contrast, the self-trapping of the electronic wavefunctions of S1 and T1(T1 † ) mostly follows their lattice distortions. Geometry vi relaxation plays an important role in the localization of the S1 and T1 † excitons owing to the nonvariational construction of the excited state wavefunction. While, mean-field calculated P + , Pand T1 states are always spatially localized even in ground state S0 geometry. Polaron P+ and Pformation is signified by the presence of the localized states for the hole or the electron deep inside the HOMO-LUMO gap of the oligomer as a result of the orbital stabilization at the LCwPBE level. The broadening of the HOMO-LUMO band gap for the T1 exciton compared to the charged states is associated with the inverted bond length alternation observed at this level. The molecular orbital energetics are investigated to identify the relationships between state localization and the corresponding orbital structure. In Chapter 7, we investigate the effect of various conformational defects of trans and cis nature on the energetics and localization of the charged P + and Pexcitations in PPV and MEHPPV. We observe that the extent of self-trapping for P+ and Ppolarons is highly sensitive on molecular and structural conformations, and distribution of atomic charges within the polymers. The particle-hole symmetry is broken with the introduction of trans defects and inclusion of the polarizable environment in consistent with experiment. The differences in the behavior of PPV and MEH-PPV is rationalized based on their orbital energetics and atomic charge distributions. We show these isomeric defects influence the behavior and drift mobilities of the charge carriers in substituted PPVs.

No description available.

Luminescent organic materials with high photostability are essential in optoelectronics, sensor, and photocatalysis applications. However, small organic molecules are generally sensitive to UV irradiation, giving rise to chemical decompositions. In this work, we demonstrate two novel CN-substituted two-dimensional sp²-carbon-linked conjugated polymers (2D CCPs) containing a chromophore triphenylene unit. The Knoevenagel polymerization between 2,3,6,7,10,11-hexakis(4-formylphenyl)triphenylene (HFPTP) and 1,4-phenylenediacetonitrile (PDAN) or 2,2’-(biphenyl-4,4’-diyl)diacetonitrile (BDAN), provides the crystalline 2D CCP-HFPTP-PDAN (2D CCP-1) and 2D CCP-HFPTP-BDAN (2D CCP-2) with dual pore structures, respectively. 2D CCP-1 and 2D CCP-2 exhibit the photoluminescence quantum yield (PLQY) up to 24.9% and 32.3%, which are the highest values among the reported 2D conjugated polymers and π-conjugated 2D covalent organic frameworks. Furthermore, compared with the well-known emissive small molecule tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN), both 2D CCPs show superior photostability under UV irradiation for two hours, profiting from the twisted and rigid structures of the CN-substituted vinylene linkages. The present work will trigger the further explorations of novel organic emitters embedded in 2D CCPs with high PLQY and photostability, which can be useful for optoelectronic devices.

In this work, we demonstrate the first synthesis of vinylene-linked 2D CPs, namely, 2D poly(phenylenequinoxalinevinylene)s 2D-PPQV1 and 2D-PPQV2, via the Horner–Wadsworth–Emmons (HWE) reaction of C2-symmetric 1,4-bis(diethylphosphonomethyl)benzene or 4,4′-bis(diethylphosphonomethyl)biphenyl with C3-symmetric 2,3,8,9,14,15-hexa(4-formylphenyl)diquinoxalino[2,3-a:2′,3′-c]phenazine as monomers. Density functional theory (DFT) simulations unveil the crucial role of the initial reversible C−C single bond formation for the synthesis of crystalline 2D CPs. Powder X-ray diffraction (PXRD) studies and nitrogen adsorption-desorption measurements demonstrate the formation of proclaimed crystalline, dual-pore structures with surface areas of up to 440 m2 g−1. More importantly, the optoelectronic properties of the obtained 2D-PPQV1 (Eg=2.2 eV) and 2D-PPQV2 (Eg=2.2 eV) are compared with those of cyano-vinylene-linked 2D-CN-PPQV1 (Eg=2.4 eV) produced by the Knoevenagel reaction and imine-linked 2D COF analog (2D-C=N-PPQV1, Eg=2.3 eV), unambiguously proving the superior conjugation of the vinylene-linked 2D CPs using the HWE reaction.

O uso de materiais orgânicos em dispositivos eletrônicos, além de menor custo e facilidade de processamento, permite obter flexibilidade e transparência. Entretanto, para que a aplicação comercial desses materiais seja viável, os processos que ocorrem nos dispositivos ainda precisam ser mais bem compreendidos, visando maior eficiência e tempo de vida. É de grande importância o estudo das interfaces entre o semicondutor orgânico e os contatos metálicos, onde ocorre transferência de portadores de carga, e a interface com o dielétrico em transistores orgânicos (OFETs), onde se forma o canal de condução. As interfaces de dispositivos eletrônicos poliméricos foram estudadas, utilizando-se Espectroscopia SFG (do inglês Sum Frequency Generation). Esta técnica obtém um sinal com a soma das frequências de dois feixes incidentes sobrepostos, em um processo seletivo a meios onde não há simetria de inversão, como no caso de interfaces. Com aplicação de um feixe de excitação na região visível e outro sintonizável no infravermelho médio, a espectroscopia SFG fornece um espectro vibracional da interface e permite o estudo do ordenamento e da orientação dos grupos moleculares. Foram construídos e analisados OFETs de poli-3-hexiltiofeno (P3HT) preparados sobre substrato de vidro ou silício, utilizando como isolante óxido de silício e/ou poli-metil-metacrilato (PMMA). Foram obtidos espectros in situ do canal de OFETs em operação, observando pequenas alterações na forma de linha, porém a baixa relação sinal/ruído não permitiu obter conclusões detalhadas. Foi constatada a manifestação de bandas da camada isolante de PMMA como consequência da aplicação de campo elétrico. Este fenômeno foi considerado como uma nova ferramenta para estudar a distribuição de cargas e campo elétrico no canal de transistores. Não foram detectados sinais de degradação irreversível no polímero semicondutor a curto prazo, e a mudança de comportamento elétrico foi atribuída majoritariamente a dopagem por oxigênio absorvido no material. / The usage of organic materials in electronic devices allows not only low cost and ease of processing but also flexibility and transparency. However, to achieve viable commercial application, the processes involved on the devices operation must still be better comprehended, aiming for improved efficiency and life time. There is great importance in the study of the interfaces between organic semiconductors and metallic contacts, where charge transfer takes place, and between the dielectric and semiconductor layers of organic transistors (OFETs), where the conducting channel is formed. The interfaces in polymeric electronic devices were studied by SFG spectroscopy (Sum Frequency Generation). In this technique, a signal with frequency that equals the sum of those of two incident beams is generated in a process only allowed in media without inversion symmetry, such as interfaces. Using a visible excitation beam and a tunable infrared one, SFG spectroscopy yields a vibrational spectrum of the interface and provides information about the conformation and orientation of molecular groups. Poly-3-hexylthiophene (P3HT) OFETs were fabricated using glass or silicon substrates and silicon oxide and/or poly-methyl-methacrylate (PMMA) for the dielectric layer. SFG spectra were acquired in situ from the channel region of operating OFETs, observing small changes in lineshape, but low signal-to-noise ration did not allow a detailed interpretation. It was found that PMMA vibrational bands appeared when polarizing the device. This phenomenon was considered a new tool for studying the electric field and charge distribution along transistor channels. It was not noted any sign of short term irreversible degradation of the semiconducting polymer, and the change in the electrical behavior was attributed mainly to doping of the polymer by oxygen absorbed in the material.

O uso de materiais orgânicos em dispositivos eletrônicos, além de menor custo e facilidade de processamento, permite obter flexibilidade e transparência. Entretanto, para que a aplicação comercial desses materiais seja viável, os processos que ocorrem nos dispositivos ainda precisam ser mais bem compreendidos, visando maior eficiência e tempo de vida. É de grande importância o estudo das interfaces entre o semicondutor orgânico e os contatos metálicos, onde ocorre transferência de portadores de carga, e a interface com o dielétrico em transistores orgânicos (OFETs), onde se forma o canal de condução. As interfaces de dispositivos eletrônicos poliméricos foram estudadas, utilizando-se Espectroscopia SFG (do inglês Sum Frequency Generation). Esta técnica obtém um sinal com a soma das frequências de dois feixes incidentes sobrepostos, em um processo seletivo a meios onde não há simetria de inversão, como no caso de interfaces. Com aplicação de um feixe de excitação na região visível e outro sintonizável no infravermelho médio, a espectroscopia SFG fornece um espectro vibracional da interface e permite o estudo do ordenamento e da orientação dos grupos moleculares. Foram construídos e analisados OFETs de poli-3-hexiltiofeno (P3HT) preparados sobre substrato de vidro ou silício, utilizando como isolante óxido de silício e/ou poli-metil-metacrilato (PMMA). Foram obtidos espectros in situ do canal de OFETs em operação, observando pequenas alterações na forma de linha, porém a baixa relação sinal/ruído não permitiu obter conclusões detalhadas. Foi constatada a manifestação de bandas da camada isolante de PMMA como consequência da aplicação de campo elétrico. Este fenômeno foi considerado como uma nova ferramenta para estudar a distribuição de cargas e campo elétrico no canal de transistores. Não foram detectados sinais de degradação irreversível no polímero semicondutor a curto prazo, e a mudança de comportamento elétrico foi atribuída majoritariamente a dopagem por oxigênio absorvido no material. / The usage of organic materials in electronic devices allows not only low cost and ease of processing but also flexibility and transparency. However, to achieve viable commercial application, the processes involved on the devices operation must still be better comprehended, aiming for improved efficiency and life time. There is great importance in the study of the interfaces between organic semiconductors and metallic contacts, where charge transfer takes place, and between the dielectric and semiconductor layers of organic transistors (OFETs), where the conducting channel is formed. The interfaces in polymeric electronic devices were studied by SFG spectroscopy (Sum Frequency Generation). In this technique, a signal with frequency that equals the sum of those of two incident beams is generated in a process only allowed in media without inversion symmetry, such as interfaces. Using a visible excitation beam and a tunable infrared one, SFG spectroscopy yields a vibrational spectrum of the interface and provides information about the conformation and orientation of molecular groups. Poly-3-hexylthiophene (P3HT) OFETs were fabricated using glass or silicon substrates and silicon oxide and/or poly-methyl-methacrylate (PMMA) for the dielectric layer. SFG spectra were acquired in situ from the channel region of operating OFETs, observing small changes in lineshape, but low signal-to-noise ration did not allow a detailed interpretation. It was found that PMMA vibrational bands appeared when polarizing the device. This phenomenon was considered a new tool for studying the electric field and charge distribution along transistor channels. It was not noted any sign of short term irreversible degradation of the semiconducting polymer, and the change in the electrical behavior was attributed mainly to doping of the polymer by oxygen absorbed in the material.

La production d’énergie avec des cellules photovoltaïques organiques (OPV) est une des applications les plus prometteuses des semi-conducteurs organiques, en raison de leur compatibilité avec les substrats flexibles permettant des produits légers, peu chers et décoratifs. Pendant longtemps, poly(3-hexylthiophène) (P3HT) a été le polymère de choix dans l’OPV combiné au [6,6]-phényl-C61-butanoate de méthyle (PC61BM) comme accepteur. Toutefois, des recherches récentes ont porté sur des polymères avec meilleures absorption et processabilité, qui peuvent assurer des rendements et des durées de vie plus élevés. Des rendements de conversion en puissance (PCE) au-dessus de 11% ont récemment été démontrés. Cette thèse rapporte sur la synthèse et la caractérisation de deux séries de polymères dits à faible bande interdite, LBGs "push-pull" (ou donneur-accepteur), constitués de l'unité donneuse 4,4-bis(2-ethylhexyl)-5,5'-dithieno[3,2-b:2',3'-d]silole (DTS) combinée au 3,6-dithiophén-2-yl-2,5-dihydro-pyrrolo[3,4-c]pyrrole-1,4-dione (DPP) ou au 5,7-di(thiényl)thiéno[3,4-b]pyrazines (DTP), comme unité acceptrice. Toutes les molécules et les polymères ont été caractérisés chimiquement et leur propriétés optoelectroniques, morphologiques et photovoltaïques ont été determinées. La série DTS-DPP a été choisie parce qu'elle est représentative d'un grand nombre de polymères LBG et a fourni un modèle facilement accessible pour évaluer l'importance de la chaîne latérale utilisée sur leur propriétés optoélectroniques et thermiques. Les premières études sur les dispositifs à base de DTS-DPP:PC61BM ont été menées, pour déterminer les propriétés photovoltaïques. Le meilleur dispositif permet d’obtenir un PCE de 1,7% avec JSC de 5,9 mA cm-2, VOC de 0,54 V et FF de 0,58. La série DTS-DTP a été choisie pour la stabilité chimique élevée des deux unités et pour la facilité de substitution des groupes latéraux. La polymérisation a partiellement abouti, en donnant seulement des oligomères. La caractérisation chimique a pu être effectuée, mais leur application dans l’OPV n'a pas été explorée. En termes de stabilité, les mécanismes de défaillance électrique des dispositifs OPV ont été étudiés, montrant une méconnaissance de leur stabilité mécanique. Les contraintes caractéristiques de chaque couche mince présentes dans les cellules solaires organiques constituent la force motrice à l’origine de la délamination des interfaces faibles ou même leur decohésion, causant une perte de l'intégrité et des performances du dispositif. Une technique pour sonder les couches ou les interfaces fragiles dans les cellules solaires polymère:fullerene est présentée. Elle a été développée par l'établissement d'un nouveau set-up pour le test pull-off, développé en utilisant un dispositif à géométrie inverse, de structure verre/ITO/ZnO/P3HT:PC61BM/PEDOT:PSS/Ag. Les dispositifs délaminés ont montré que le point le plus faible est localisé à l'interface AL/HTL, en bon accord avec la littérature. La technique a été étendue en variant les deux couches sensibles, en utilisant differents polymères LBG pour l’AL (PSBTBT et PDTSTzTz) en combinaison avec deux formulations de PEDOT:PSS, CleviosTM HTL Solar à base d'eau et un nouveau HTL Solar 2 à base de solvant organique. Une différence entre la contrainte à la rupture des dispositifs avec différentes combinaisons de AL et HTL est visible, suggérant différents chemins de fracture, tel que confirmé par la caractérisation de surface et qui pourrait être corrélée avec la différence de comportement de la couche active avec les deux formulations de PEDOT:PSS. Une autre voie adoptée, a été d’introduire une couche d’interface de copolymère à blocs amphiphile afin d'améliorer la compatibilité des deux couches. Cette stratégie n'a pas abouti et la nouvelle architecture présente une adhésion réduite. La poursuite de l’amélioration des procédés de fabrication de ces dispositifs pourrait faire de cette nouvelle architecture, une alternative viable. / Organic photovoltaic (OPV) devices are one of the most promising applications of organic semiconductors due to their compatibility with flexible plastic substrates resulting in light weight, inexpensive and decorative products. For a long time poly(3-hexylthiophene) (P3HT) has been the polymer of choice in OPV devices in combination with [6,6]-phenyl-C61-butyric acid methylester (PC61BM) as acceptor. However, recent research has focused on polymers with improved absorbance and processability that can ensure higher efficiencies and longer lifetimes (Low BandGap polymers (LBGs)). This has been fully demonstrated with a power conversion efficiency (PCE) above 11%. This thesis reports synthesis and characterization of two series of so-called “push-pull” (or donor-acceptor) LBGs based on the donor unit 4,4′-bis(2-ethylhexyl)-5,5’-dithieno[3,2-b:2′,3′-d]silole (DTS) and either 3,6-dithiophen-2-yl-2, 5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione (DPP) or 5,7-di(thienyl)thieno[3,4-b]pyrazines (DTP), as acceptor unit. All π-conjugated molecules and polymers were characterized by chemical investigation and their optoelectronic, morphological, and photovoltaic properties are reported. The DTS-DPP series was chosen because representative of a large number of LBG polymers and provided an easily accessible and useful template to discover the importance of the type of side-chain used on the polymer optoelectronic and thermal properties. First studies on DTS-DPP:PC61BM devices have been conducted, in order to investigate any effect on their photovoltaic properties. The best device obtained had a PCE of 1.7% with JSC of 5.9 mA•cm-2, VOC of 0.54 V and FF of 0.58. The DTS-DTP series was chosen for the high stability of the two units and for the ease of substitution of the side-groups. The synthesis was partially successful and only oligomers were obtained. Nonetheless, chemical characterization was performed but their application in OPV was not explored. In terms of device stability, the electrical failure mechanisms in OPV devices have been investigated, while little is known about their mechanical stability. The characteristic thin film stresses of each layer present in organic solar cells, in combination with other possible fabrication, handling and operational stresses, provide the mechanical driving force for delamination of weak interfaces or even their de-cohesion, leading to a loss of device integrity and performance. A technique to probe weak layers or interfaces in inverted polymer:fullerene solar cells is presented. It was developed by establishing a new set-up for the pull-off test. The technique was developed using inverted device, with the structure glass/ITO/ZnO/P3HT:PC61BM/PEDOT:PSS/Ag. The delaminated devices showed that the weakest point was localized at the active layer/hole transporting layer interface, in good agreement with the literature. The technique was extended varying both sensitive layers, using different p-type low bandgap (co)polymers for the active layer (PSBTBT and PDTSTzTz) in combination with two different PEDOT:PSS formulations, the water based CleviosTM HTL Solar and a new organic solvent based HTL Solar 2. The half-devices produced upon destructive testing have been characterized by contact angle measurement, AFM and XPS to locate the fracture point. A difference in the stress at break for devices made with different combinations of active and hole transporting layers is visible, suggesting different fracture paths, as confirmed by surface characterization and could be correlated to the different behavior of the active layer with the two PEDOT:PSS formulations. Another solution adopted, it had been the introduction of amphiphilic block-copolymer interlayer to enhance the compatibility of the two layers. This strategy was not successful and the new architecture showed reduced adhesion strength. Further development of device processing could make this new architecture a viable alternative.

There are two general ways to introduce functionalities into a polymeric structure: functionalization of the monomeric units before polymerization and postfunctionalization of the preformed polymer. Building libraries of polymers with different functionalities can be completed with significantly less effort by the second method, as each postfunctionalization of a single batch of polymeric backbone can involve as little as one synthetic step. One method of building a polymeric backbone for postfunctionalization involves the synthesis of hyperbranched conjugated polymers (HCPs) from AB2 monomeric units. A polymer formed from n AB2 monomeric units should contain n reactive B groups, which act as sites of functionalization. Utilizing this principle, two different hyperbranched poly(phenylene vinylene-phenylene ethynylene) scaffolds were synthesized and studied in both their inherent properties and functionalization. The first HCP synthesized was compared against a monomeric cruciform model and a linear polymer with a similar structure. The hyperbranched polymer has red-shifted absorption and emission in comparison to the cruciform model and linear polymer. The HCP quenches paraquat more efficiently than the linear polymer by a factor of about two, suggesting a greater rate of energy transfer. The functionalization of HCPs was studied; iodine groups decorating the HCPs were replaced with terminal alkynes by Pd-catalyzed coupling, providing a library of 24 differently functionalized HCPs. Elemental analyses of the postfunctionalized polymers show nearly complete substitution of the iodine groups. The postfunctionalized polymers show increased fluorescence compared to the original iodine decorated polymers, due to the loss of the heavy atom effect inducing iodine groups. The emissions of the postfunctionalized polymers in solution show a strong dependence on the groups attached to the conjugated structures, with emission maxima ranging from 505 nm to 602 nm; quantum yields range from 0.7% to 25%. Solid-state emission studies show stronger and more red-shifted spectra compared to emissions observed in solution.

The discovery of conducting and semiconducting polymers has opened the possibility to produce integrated circuits entirely of plastic with standard continuous printing techniques. Nowadays several of this polymers are commercial available, however the performances of this materials are strongly affected by their supramolecular order achieved after deposition. In this research, the influence of some standard printing techniques on the electrical performances of conjugated polymers is evidenced in order to realise logic devices with these materials.