<p>There are still technique hurdles that needed to be overcome in the commercialization of electrochromic devices (ECDs) for energy-saving smart windows. Among them, the long-term stability of ECDs and the high fabrication cost are <a>the critical issues</a>. The pricey ECDs can only be paid off through saving the energy for years, and their price will be dramatically lower if they can be solution-processed. Here, we studied the ions behaviors in the open-circuit state of electrochromic conjugated polymers (ECPs) which is important to the stability of ECDs during the operation. Moreover, we investigated the solution-processable ion storage layers and paired them with p-type ECPs and demonstrated the possibility of using them in the highly efficient roll-to-roll fabrication of ECD.</p> <p>The crosslinkable non-color changing nitroxy radical-based polymer was investigated as the ion storage layer. With the applied of crosslinking strategy, the dissolution problems of radical polymers-based counter electrode in the electrolyte was suppressed, resulting in the enhancement of both performance and cycling stability of ECDs. Although p-type ion storage materials are widely studied as the ion storage layers for ECPs, they need to go through complicated pretreatment processes, including pre-oxidation, washing, and drying, before they can be paired with ECPs in an ECD. This complicated process greatly increases the fabrication cost. </p> <p>In our last work, we applied the UV ozone (UVO) pretreatment to the solution-processed n-type niobium oxide and evaluated its potentials to be used as the ion storage layer for p-type ECPs. The UVO pretreatment generates strong oxidants like ozone or atomic oxygen which induce the photolysis of organic residues of ligands and organic solvent trapped in the solution-processed metal oxide layer led to the formation of free radical species. These highly reactive species promoted the formation of the amorphous metal−oxygen network. Following by low-temperature annealing (< 150 ^oC), the ion-storage properties of niobium oxide is comparable with the high temperature annealed (300 ^oC) niobium oxide. The method is successfully applied to fabricate niobium oxide on a flexible conductive substrate and demonstrate the capability to pair with p-type ECPs and fabricate high-performance ECDs without the need of any pretreatments. The low-temperature solution processing of both layers will significantly reduce the fabrication cost of ECDs. </p>

A long-term goal within the field of organic electronics has been to developflexible and functional devices, which can be processed and patterned withlow-cost and energy-efficient solution-based methods. This thesis presents anumber of functional paths towards the attainment of this goal via thedevelopment and demonstration of novel fabrication and patterningmethods involving the important organic-semiconductor family termedfullerenes.Fullerenes are soccer-shaped small molecules, with two often-employedexamples being the symmetric C60 molecule and its more soluble derivative[6,6]-phenyl-C61-butyric acid methyl ester (PCBM). We show that PCBM canbe photochemically transformed into a dimeric state in a bi-excited reactionprocess, and that the exposed material features a significantly reducedsolubility in common solvents as well as an effectively retained electronmobility. This attractive combination of material properties allows for adirect and resist-free lithographic patterning of electronic PCBM films downto a smallest feature size of 1 µm, using a simple and scalable two-stepprocess constituting light exposure and solution development. In a furtherdevelopment, it was shown that the two-step method was useful also in thearea-selective transformation of fullerene/conjugated-polymer blend films,as demonstrated through the realization of a functional complementary logiccircuit comprising a 5-stage ring oscillator.In another project, we have synthesized highly flexible, single-crystal C60nanorods with a solution-based self-assembly process termed liquid-liquidinterfacial precipitation. The 1-dimensional nanorods can be deposited fromtheir synthesis solution and employed as the active material in field-effecttransistor devices. Here, it was revealed that the as-fabricated nanorods canfeature an impressive electron mobility of 1.0 cm2 V-1 s-1, which is on par withthe performance of a work horse in the transistor field, viz. vacuumdeposited amorphous Si. We further demonstrated that the processability ofthe nanorods can be improved by a tuned light-exposure treatment, duringwhich the nanorod shell is polymerized while the high-mobility interior bulkis left intact. This has the desired consequence that stabile nanoroddispersions can be prepared in a wide range of solvents, and we anticipatethat functional electronic devices based on solution-processable nanorodscan be realized in a near future.

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Die enormen Fortschritte im Bereich der organischen Elektronik in den letzten Jahrzehnten haben zur Entwicklung effizienter optoelektronischer Bauelemente geführt wie z. B. organische Leuchtdioden (OLEDs), organische Feldeffekttransistoren (OFETs) und organische Photovoltaikzellen (OPV). Darüber hinaus ermöglichen halbleitende Polymere die Herstellung kostengünstiger, großflächiger elektronischer Bauelemente mit Hilfe von Niedertemperatur Lösungsverfahren auf flexiblen Substraten. Der erste Teil dieser Arbeit befasste sich mit der Entwicklung von Host-Materialien für die emittierende Schicht (EML) von OLEDs. Effiziente Host-Materialien sollten bestimmte Eigenschaften aufweisen, z. B. eine hohe Triplett-Energie, einen hohen und ausgeglichenen Ladungsträgertransport, geeignete Grenzorbitalniveaus, die mit denen der Nachbarschichten übereinstimmen, und morphologische Stabilität. Zu diesem Zweck wurden Polymere auf Carbazolbasis mit einer elektronenziehenden Gruppe (EWG) an verschiedenen Stellen der Kette entworfen und durch Suzuki Kupplung synthetisiert. Die Polymere wurden chemisch und optisch charakterisiert, bevor sie nach Dotierung mit Tris(2-phenylpyridin)iridium(III) (Ir(ppy)3) in eine funktionierende grüne OLED eingebaut wurden. Zusätzlich wurden die Ladungstransporteigenschaften durch die Herstellung von Einzelträgergeräte untersucht. Der zweite Teil widmete sich der Herstellung von Halbleitermaterialien für OFET Anwendungen. Nach einem neuartigen Moleküldesign wurde eine Reihe von Verbindungen auf der Basis von Diketopyrrolopyrrol (DPP) und Thiophen durch Stille-Kupplung und phosphinfreie direkte Heteroarylierung synthetisiert. Dieses molekulare Design erwies sich als flexibel für die Synthese neuartiger Derivate durch Modifikation der Endgruppen. Die Korrelation zwischen Struktur und Morphologie wurde ebenfalls untersucht. Die Mobilität der Ladungsträger, welche von der chemischen Struktur und Morphologie des Halbleiters beeinflusst wird, ist einer der wichtigsten Parameter eines OFET. Daher wurden die erhaltenen Materialien mit niedriger Bandlücke in Transistoren verschiedener Architekturen integriert, die durch Lösungsverfahren wie Spin-Coating und Scherbeschichtung hergestellt wurden. Die Mobilität sowie andere OFET-Parameter wurden im p- und n-Typ-Betrieb gemessen.:1 Theoretical background 1.1 Introduction 1.2 Organic semiconductors 1.3 Organic Light Emitting Diodes 1.3.1 Physics of OLEDs 1.3.2 Solution processable OLEDs 1.3.3 Polymer Light-Emitting Diodes 1.4 Organic Field-Effect Transistors 1.4.1 Device operation 1.4.2 Ambipolar transistors 1.5 Synthesis of π-conjugated polymers 1.6 Characterisation methods 1.6.1 Chemical structure characterisation 1.6.2 Optical characterisation 1.6.3 Morphology and microstructure 2 Motivation and aim 3 Results and discussion 3.1 Polymers for ambipolar semiconductors 3.1.1 Molecular design 3.1.2 (N-carbazole)triphenylphosphine oxide polymers 3.1.3 Bis(carbazol-3-yl)triphenylphosphine oxide polymers 3.1.4 ((Carbazol-3-yl)phenoxy)hexyl diphenylphosphinate polymers 3.1.5 ((Phenothiazin-10-yl)phenyl)diphenylphosphine oxide polymers 3.1.6 Device integration 3.1.7 Summary 3.2 DPP based molecules for OFETs 3.2.1 Molecular design 3.2.2 DBT-I series 3.2.3 DBT-II 3.2.4 Device integration 3.2.5 Summary 4 Conclusions and outlook 5 Experimental part 6 Supporting Information 7 Bibliography / Staggering progress in the field of organic electronics over the past decades has led to the development of efficient optoelectronic devices, such as organic light-emitting diodes (OLEDs), organic field-effect transistors (OFETs)and organic photovoltaic cells (OPV). Moreover, semiconducting polymers enable the fabrication of low-cost, large-area electronic devices using low-temperature solution-processing methodologies on flexible substrates. The first part of this thesis focused on the development of host materials for the emitting layer (EML) of an OLED. Efficient hosts should possess a number of properties, such as high triplet energy, good and balanced charge-carrier transport, suitable frontier orbital levels that match those of the neighbouring layers, and morphological stability. To this end, carbazole-based polymers featuring an electron-withdrawing group (EWG) at different positions of the chain were designed and synthesised by Suzuki coupling. Chemical and optical characterisations of the polymers were performed prior to their incorporation into a functioning green OLED upon doping with tris(2-phenylpyridine)iridium(III) (Ir(ppy)3). Additionally, the charge-transport properties were studied through the fabrication of single-carrier devices. The second part was dedicated to the production of semiconductor materials for OFET applications. Following a novel molecular design, a series of compounds based on diketopyrrolopyrrole (DPP) and thiophene were synthesised by Stille coupling and phosphine-free direct heteroarylation. This molecular design was proven to be flexible for the synthesis of novel derivatives by modification of the end-groups. The correlation between structure and morphology was also studied. Mobility, influenced by the chemical structure and morphology of the semiconductor, is one of the most important parameters of an OFET. Thus, the obtained low bandgap materials were integrated into devices of different architectures, fabricated by solution processing methodologies, such as spin coating and shear coating, and the mobility, as well as other OFET parameters, were measured in p- and n-type operation.:1 Theoretical background 1.1 Introduction 1.2 Organic semiconductors 1.3 Organic Light Emitting Diodes 1.3.1 Physics of OLEDs 1.3.2 Solution processable OLEDs 1.3.3 Polymer Light-Emitting Diodes 1.4 Organic Field-Effect Transistors 1.4.1 Device operation 1.4.2 Ambipolar transistors 1.5 Synthesis of π-conjugated polymers 1.6 Characterisation methods 1.6.1 Chemical structure characterisation 1.6.2 Optical characterisation 1.6.3 Morphology and microstructure 2 Motivation and aim 3 Results and discussion 3.1 Polymers for ambipolar semiconductors 3.1.1 Molecular design 3.1.2 (N-carbazole)triphenylphosphine oxide polymers 3.1.3 Bis(carbazol-3-yl)triphenylphosphine oxide polymers 3.1.4 ((Carbazol-3-yl)phenoxy)hexyl diphenylphosphinate polymers 3.1.5 ((Phenothiazin-10-yl)phenyl)diphenylphosphine oxide polymers 3.1.6 Device integration 3.1.7 Summary 3.2 DPP based molecules for OFETs 3.2.1 Molecular design 3.2.2 DBT-I series 3.2.3 DBT-II 3.2.4 Device integration 3.2.5 Summary 4 Conclusions and outlook 5 Experimental part 6 Supporting Information 7 Bibliography