O presente trabalho envolveu a eletrossíntese de três polímeros da família dos poli(p-fenilenovinileno)s, PPVs, apresentando como substituintes grupos alcóxi de cadeia longa. Esses polímeros foram caracterizados espectroscopicamente (RMN de 1H, IV e UV/VIS), termicamente (TG), por cromatografia por exclusão de tamanho (SEC), eletronicamente por voltametria cíclica e eletricamente por meio de curvas I x V em dispositivos do tipo sanduíche (metal/polímero/metal). Os polímeros foram utilizados na construção de sensores de gases para avaliação da capacidade sensitiva a vapores orgânicos, mostrando-se promissores para utilização em narizes eletrônicos. Construíram-se, também, dispositivos emissores de luz orgânicos (OLEDs) com utilização desses polímeros como camada ativa, no intuito de se conhecer sua aplicabilidade em dispositivos optoeletrônicos. Para tal, foram feitas determinações de luminância e de eficiência quântica de luminância dos OLEDs construídos. Os dispositivos do tipo sanduíche, os OLEDs e as medidas correspondentes foram realizados em Curitiba, em colaboração com o Prof. Dr. Ivo Alexandre Hümmelgen, líder do Grupo de Dispositivos Optoeletrônicos Orgânicos do Departamento de Física da Universidade Federal do Paraná. / The present work describes the electrosynthesis of three polymers of the poly(p-phenylenevinylene) (PPV) family, having at least one long chain alkoxy group as substituent. These polymers were characterized by spectroscopic analyses (1H NMR, IR and UV-Vis), thermogravimetry (TG), size exclusion chromatography (SEC), cyclic voltammetry and electrically by current vs. potential plots obtained from metal/polymer/metal sandwich devices. The polymers were tested as active layers in gas sensors for organic vapour analyses aimed for future use in electronic noses. The same polymers were also employed in organic light emitting diodes (OLEDs) in which the luminance and the luminance quantum efficiency were measured. Both the sandwich devices and the OLEDs were made in Curitiba with the collaboration of Prof. Ivo Hümmelgen, head of the Group of Organic Optoelectronic Devices at the Physics Department of the Federal University of Paraná (UFPR).

Master’s thesis deals with the design of development kit for communication between a microcontroller and a computer using USB, Bluetooth, WiFi and Ethernet interfaces. In the theoretical introduction is the analysis of theese interfaces and the interfaces used for communication by the microcontroller. In the next part, components for the development kit are selected. Then a wiring diagram and the printed circuit board is designed. Next, the firmware design is described. The last chapter deals with the implementation and testing of the development kit. The appendix contains a proposal for a laboratory task to introduce the development kit to students.

In dieser Arbeit werden die verschiedenen Möglichkeiten der Elektronenstrahlstrukturierung von organischen Schichten untersucht und charakterisiert. Je nach ihrer Energie und Leistung bewirkt die Interaktion der beschleunigten Strahlelektronen mit dem Material, auf das sie treffen, unterschiedliche Wechselwirkungen. Im Rahmen der durchgeführten Versuche wird demonstriert, dass diese Wirkung von lokalen, strahlchemischen Strukturveränderungen bis hin zu einem örtlich begrenzten Materialabtrag reicht. Neben den Untersuchungen einzelner organischer Schichten, werden ebenso organische Leuchtdioden (OLEDs) und deren Veränderungen unter Elektroneneinwirkung charakterisiert. Bei der Elektronenstrahlstrukturierung einer OLED mit sehr kleinen Leistungen wird sowohl die elektrische Leitfähigkeit als auch die Leuchtdichte der OLED reduziert. Dabei sind die Veränderungen in den organischen Materialien lokal stark auf den Ort der Elektroneneinwirkung begrenzt. Dies konnte genutzt werden, um eine hochauflösende Graustufenstrukturierung zu demonstrieren und ein Bild mit Strukturbreiten von 2 µm mit einem Elektronenstrahlprozess in eine weiße OLED zu schreiben. Elektronenstrahlprozesse mit höheren Leistungen bedingen eine thermische Wirkung und können so dünne organische Schichten lokal verdampfen. Mit solch einem Prozess konnte ein linien- und flächenhafter Abtrag realisiert werden, ohne die darunterliegende Elektrode zu schädigen. OLEDs haben den Vorteil, dass sie in Dünnschichttechnik hergestellt werden können und sehr kontrastreiche und farbechte Flächenlichtquellen sind. Daher bilden sie auch die Grundlage moderner Displays, an die jedoch stets wachsende Anforderungen gestellt werden. Klassischerweise werden OLED-Farbdisplays mithilfe einer strukturierten Abscheidung durch feine Metallmasken oder durch die Nutzung weißer OLEDs zusammen mit Farbfiltern hergestellt. Im Rahmen dieser Arbeit wurde ein alternatives Strukturierungskonzept entwickelt, dass die Möglichkeit bietet, ein OLED-Farbdisplay mithilfe eines Elektronenstrahlprozesses herzustellen. Das Schichtsystem der OLED bildet einen optischen Resonator, bei dem die Elektroden die Mikrokavität darstellen und die Dicke der organischen Schichten die Resonatorlänge definiert. Mittels kavitätsselektiver Modenauswahl ist es möglich, aus dem Spektrum einer weißen OLED verschiedene Farben auszukoppeln, wenn man die Resonatorlänge ändert. In der vorliegenden Arbeit wurde diese Anpassung der Resonatorlänge durch die Elektronenstrahlstrukturierung der ersten organischen Schicht vorgenommen und so rote, grüne und blaue OLEDs erzeugt und charakterisiert. Neben den grundlegenden Untersuchungen zu diesem Ansatz werden abschließend Grenzen und Möglichkeiten des Verfahrens aufgezeigt.:1 Einleitung 2 Grundlagen 2.1 Organische Leuchtdioden (OLEDs) 2.1.1 Organische Halbleiter 2.1.2 Aufbau und Funktionsweise von OLEDs 2.1.3 Elektro-optische Charakteristik 2.2 OLED-Vollfarbdisplays 2.2.1 Funktionsweise und Konzepte 2.2.2 Strukturierungsmethoden – Stand der Technik 2.3 Elektronenstrahlstrukturierung 2.3.1 Wechselwirkungen von Elektronen mit Festkörpern 2.3.2 Thermische Mikrobearbeitung 2.3.3 Nichtthermische Mikrobearbeitung 3 Zielsetzung und Lösungsansatz 3.1 Ziele dieser Arbeit 3.2 Prinzip Mikrokavität-OLED 4 Methodische Untersuchungen und Charakterisierung 4.1 OLED-Testsubstrate 4.1.1 Aufbau und Layout 4.1.2 Schichtabscheidung 4.2 Elektronenstrahlbehandlung 4.3 Analysemethoden 4.3.1 Schichtcharakterisierung 4.3.2 Elektro-optische Charakterisierung 4.3.3 FTIR-Spektroskopie 4.3.4 Photolumineszenz-Spektroskopie 5 Experimentelle Ergebnisse und Diskussion 5.1 Nichtthermische Elektronenstrahlbearbeitung von organischen Einzelschichten 5.1.1 Spektroskopische Untersuchungen 5.1.2 Elektrische Untersuchungen von Hole-Only-Devices 5.2 Nichtthermische Elektronenstrahlbearbeitung von OLEDs 5.2.1 Elektro-optische Untersuchungen 5.2.2 Hochauflösende Graustufenstrukturierung 5.2.3 Einfluss eines anschließenden Temperns 5.3 Thermische Elektronenstrahlbearbeitung 5.3.1 Thermische Elektronenstrahlstrukturierung organischer Schichten 5.3.2 Elektronenstrahlstrukturierung für Mikrokavität-OLEDs 6 Zusammenfassung und Ausblick A Technische Ergänzunge B Literaturverzeichnis C Abbildungsverzeichnis D Tabellenverzeichnis E Abkürzungsverzeichnis F Lebenslauf der Autorin G Wissenschaftliche Publikationen H Danksagung / In this work different possibilities of electron beam patterning for organic layers are investigated and characterized. Depending on the energy and power of the accelerated beam electrons, different interaction processes with the material can be initiated. Within the performed experiments it could be demonstrated that these effects range from structural chemical changes up to a localized evaporation of material. In addition to investigations of individual organic layers, organic light-emitting diodes (OLEDs) and their changes under the influence of electrons are also characterized. When OLEDs are patterned with an electron beam process with low power, both the electrical conductivity and the luminance of the OLED are reduced. The changes in the organic materials are locally strongly limited to the location of the electron penetration. This could be used to demonstrate a high-resolution grayscale patterning and to write an image with critical dimensions of 2 µm into a white OLED using an electron beam process. Electron beam processes with higher power cause a thermal effect and are able to evaporate thin organic layers locally. With such a process, a linear and areal shaped removal could be realized without damaging the underlying electrode. OLEDs have the advantage that they can be produced in thin-film technology. Furthermore they are an area light source, that has a high contrast and very good color properties. Therefore, most of the modern displays consist of OLEDs. Traditionally, OLED color displays are made by structured deposition through fine metal masks or by the use of white OLEDs together with color filters. As part of this work, an alternative structuring concept has been developed that offers the possibility of producing an OLED color display using an electron beam process. The layer system of the OLED forms an optical resonator in which the electrodes represent the microcavity and the thickness of the organic layers defines the resonator length. By means of cavity-selective mode selection, it is possible to extract different colors from the spectrum of a white OLED by changing the resonator length. In the present work, this adjustion of the resonator length was carried out by electron beam patterning of the first organic layer, thus generating and characterizing red, green and blue OLEDs. In addition to the fundamental investigations on this approach, limits and future perspectives of the method were finally pointed out.:1 Einleitung 2 Grundlagen 2.1 Organische Leuchtdioden (OLEDs) 2.1.1 Organische Halbleiter 2.1.2 Aufbau und Funktionsweise von OLEDs 2.1.3 Elektro-optische Charakteristik 2.2 OLED-Vollfarbdisplays 2.2.1 Funktionsweise und Konzepte 2.2.2 Strukturierungsmethoden – Stand der Technik 2.3 Elektronenstrahlstrukturierung 2.3.1 Wechselwirkungen von Elektronen mit Festkörpern 2.3.2 Thermische Mikrobearbeitung 2.3.3 Nichtthermische Mikrobearbeitung 3 Zielsetzung und Lösungsansatz 3.1 Ziele dieser Arbeit 3.2 Prinzip Mikrokavität-OLED 4 Methodische Untersuchungen und Charakterisierung 4.1 OLED-Testsubstrate 4.1.1 Aufbau und Layout 4.1.2 Schichtabscheidung 4.2 Elektronenstrahlbehandlung 4.3 Analysemethoden 4.3.1 Schichtcharakterisierung 4.3.2 Elektro-optische Charakterisierung 4.3.3 FTIR-Spektroskopie 4.3.4 Photolumineszenz-Spektroskopie 5 Experimentelle Ergebnisse und Diskussion 5.1 Nichtthermische Elektronenstrahlbearbeitung von organischen Einzelschichten 5.1.1 Spektroskopische Untersuchungen 5.1.2 Elektrische Untersuchungen von Hole-Only-Devices 5.2 Nichtthermische Elektronenstrahlbearbeitung von OLEDs 5.2.1 Elektro-optische Untersuchungen 5.2.2 Hochauflösende Graustufenstrukturierung 5.2.3 Einfluss eines anschließenden Temperns 5.3 Thermische Elektronenstrahlbearbeitung 5.3.1 Thermische Elektronenstrahlstrukturierung organischer Schichten 5.3.2 Elektronenstrahlstrukturierung für Mikrokavität-OLEDs 6 Zusammenfassung und Ausblick A Technische Ergänzunge B Literaturverzeichnis C Abbildungsverzeichnis D Tabellenverzeichnis E Abkürzungsverzeichnis F Lebenslauf der Autorin G Wissenschaftliche Publikationen H Danksagung

In the last decades, investigations of organic light-emitting diodes (OLEDs) have tackled several key challenges of this lighting technology and have brought the electron to photon conversion efficiency close to unity. However, currently only 20% to 30% of the photons can typically be extracted from OLED structures, as total internal reflection traps the major amount of the generated light inside the devices. This work focuses on the optimization of the optical properties of top-emitting OLEDs, in which the emission is directed away from the substrate. In this case, opaque materials, e.g. a metal foil or a display backplane can be used as substrate as well. Even though top-emitting OLEDs are often preferred for applications such as displays, two main challenges remain: the application of light extraction structures and the deposition of highly transparent materials as top electrode, without harming the organic layers below. Both issues are addressed in this work. First, top-emitting OLEDs are deposited on top of periodically corrugated light outcoupling structures, in order to extract internally trapped light modes by Bragg scattering and to investigate the basic scattering mechanisms in these devices. It is shown for the first time that the electrical performance is maintained in corrugated top-emitting OLEDs deposited on top of light extraction structures. Furthermore, as no adverse effects to the internal quantum efficiency have been observed, the additional emission from previously trapped light modes directly increases the device efficiency. It has been proven that the spectral emission of corrugated OLEDs is determined by the interference of all light modes inside the air light-cone, including the observation of destructive interference and anti-crossing phenomena. The formation of a coherently coupled mode pair of the initial radiative cavity mode and a Bragg scattered mode has been first observed, when grating structures with an aspect ratio > 0.2 are applied. There, the radiative cavity mode partially vanishes. The observation and analysis of such new emission phenomena in corrugated top-emitting OLEDs has been essential in obtaining a detailed insight on fundamental scattering processes as well as for the optimization and control of the spectral emission by light extraction structures. Second, the adverse impact of using only moderately transparent silver electrodes in white top-emitting OLEDs has been compensated improving the metal film morphology, as the organic materials often prevent a replacement by state-of-the-art electrodes, like Indium-tin-oxide (ITO). A high surface energy Au wetting layer, also in combination with MoO3, deposited underneath the Ag leads to smooth, homogeneous, and closed films. This allows to decrease the silver thickness from the state-of-the-art 15 nm to 3 nm, which has the advantage of increasing the transmittance significantly while maintaining a high conductivity. Thereby, a transmittance comparable to the ITO benchmark has been reached in the wavelength regime of the emitters. White top-emitting OLEDs using the wetting layer electrodes outperform state-of-the art top-emitting devices with neat Ag top electrodes, by improving the angular colorstability, the color rendering, and the device efficiency, further reaching sightly improved characteristics compared to references with ITO bottom electrode. The enormous potential of wetting layer metal electrodes in improving the performance of OLEDs has been further validated in inverted top-emitting devices, which are preferred for display applications, as well as transparent OLEDs, in which the brittle ITO electrode is replaced by a wetting layer electrode. Combining both concepts, wetting layer electrodes and light extraction structures, allows for the optimization of the grating-OLED system. The impact of destructive mode interference has been reduced and thus the efficiency increased by a decrease of the top electrode thickness, which would have not been achieved without a wetting layer. The optimization of corrugated white top-emitting OLEDs with a top electrode of only 2 nm gold and 7 nm silver on top of a grating with depth of 150 nm and period of 0.8 µm have yielded a reliable device performance and increased efficiency by a factor of 1.85 compared to a planar reference (5.0% to 9.1% EQE at 1000 cd/m2). This enhancement is comparable to common light extraction structures, such as half-sphere lenses or microlens foils, which are typically restricted to bottom-emitting devices. Overall, the deposition of top-emitting OLEDs on top of light extraction structures finally allow for an efficient extraction of internally trapped light modes from these devices, while maintaining a high device yield. Finally, the investigations have resulted in a significant efficiency improvement of top-emitting OLEDs and the compensation of drawbacks (optimization of the white light emission and the extraction of internal light modes) in comparison to the bottom-emitting devices. The investigated concepts are beneficial for OLEDs in general, since the replacement of the brittle ITO electrodes and the fabrication of roll-to-roll processing compatible light extraction structures are also desirable for bottom-emitting, or transparent OLEDs.

Den Fokus dieser Arbeit bildet die Untersuchung und die konzeptionelle Verbesserung der wichtigsten Eigenschaften organischer Leuchtdioden (OLED) – die Lebensdauer und die Quantenausbeute, welche sich durch die interne und externe Quanteneffizienz kategorisieren lässt. Es werden monochrome pin- Strukturen betrachtet, welche die Basis für Displays und weiße Multifarben- OLEDs darstellen. Die Auswirkung der Ladungsbalance auf die interne Quanteneffizienz wird untersucht. Dabei finden Triplettemitter Verwendung, da diese aus spinstatistischen Gründen viermal effizienter als fluoreszente Substanzen sind. Für hohe Effizienzen ist die ambipolare Ladungs- und Exzitonenverteilung in der Emissionsschicht mit breiter und zentraler Rekombinationszone anzustreben. Dies wird durch einen energetisch barrierefreien Schichtaufbau über die Auswahl der Matrix-, Blocker- und Transportmaterialien bezüglich geeigneter Transportniveaus und Ladungsträgerbeweglichkeiten erreicht. Bei roten OLEDs wird durch den Austausch des Lochblockers mit geeignetem LUMO die Elektroneninjektion in die löcherleitende Emissionsschicht erhöht und dadurch die Ladungsbalance maximiert. Damit werden externe Quanteneffizienzen von 20% erzielt, was dem Maximum der internen Quanteneffizienz von 100% entspricht. Des Weiteren werden neue Konzepte zur höheren Lichtauskopplung entwickelt. Aufgrund interner Totalreflexionen bleiben 80% der Photonen in Organikund Substratmoden gefangen was die externe Quanteneffizienz begrenzt. Eine deutliche Reduzierung dieser Moden wird bei OLEDs mit stärkeren Mikrokavitäten durch ITO/Silber-Anoden festgestellt. Die energetische und räumliche Umverteilung der Photonen verringert Totalreflexionen womit die Auskopplung bzw. die externe Quanteneffizienz um den Faktor 1,5 erhöht wird. Für rote OLEDs werden dadurch Rekordwerte von 26% externer Quanteneffizienz und einer Leistungseffizienz von 81 lm/W erzielt. Die auftretende winkelabhängige Farbverschiebung kann durch streuende Mikrolinsenfolien reduziert werden. Für verbesserte Auskopplung ohne Farbverschiebung werden Streukonzepte mit rauen Schichten getestet. Kristalline Schichten innerhalb der Organik beeinflussen allerdings den elektrischen Teil der OLED. Dies wird durch extrinsische Verlagerung der Streuschicht ausgeschlossen. Weiterhin wird die intrinsische Degradation von OLEDs mit phosphoreszenten Iridium-Emittern untersucht. Als Hauptursache werden strominduzierte chemische Reaktionen zwischen Emittermolekülen und anderen umgebenden Substanzen identifiziert. Die Akkumulation von Ladungsträgern und Exzitonen fördert diese Reaktionen. Als Zerstörungsmechanismus wird die Dissoziation der Iridium-Emitter mit folgender irreversibler Komplexbildung der Fragmente mit Umgebungsmaterialien wie dem Lochblocker festgestellt. Die OLED-Lebensdauer korreliert dabei doppelt- logarithmisch mit der Anzahl der Komplexe. Die chemische Reaktivität der Umgebungsmaterialien bestimmt die Stärke der Komplexbildung. Mit inerten Substanzen konnte bei roten OLEDs mit 10 Millionen Stunden bei Display-Helligkeit ein Weltrekord erzielt werden. Die geringe Degradation erfordert Extrapolationsmethoden. Es wird ein gestreckt exponentielles Verhalten der Helligkeitsabnahme beobachtet. Eine neue Fehleranalyse der Extrapolation ermöglicht die Angabe von Lebensdauer-Infima bei sehr stabilen OLEDs.

This thesis is about the development and validation of a numerical model for the simulation of the current-voltage characteristics of organic thin-film devices. The focus is on the analysis of a white organic light-emitting diode (OLED) with fluorescent blue and phosphorescent red and green emitters. The simulation model describes the charge transport as a one-dimensional drift-diffusion current and is developed on the basis of the Scharfetter-Gummel method. It incorporates modern theories for the charge transport in disordered organic materials, which are considered by means of special functions for the diffusion coefficient and the charge-carrier mobility. The algorithm is designed such that it can switch between different models for mobility and calculates both transient and steady-state solutions. In the analysis of the OLED, electron and hole transport are investigated separately in series of single-carrier devices. These test devices incorporate parts of the layers in the OLED between symmetrically arranged injection layers that are electrically doped. Thereby, the OLED layer sequence is reconstructed step by step. The analysis of the test devices allows to obtain the numerous parameters which are required for the simulation of the complete OLED and reveals many interesting features of the OLED. For instance, it is shown how the accumulation of charge carriers in front of an interface barrier increases the mobility and the transfer rate across the interface. Furthermore, it is demonstrated how to identify charge-trapping states. This leads to the detection of deep trap states in the emission zone of the OLED -- an interesting aspect, since these states can function as recombination centers and may cause non-radiative losses. Moreover, various other effects such as interface dipoles and a slight freeze-out of active electric dopants in the injection layers are observed. In the simulations of the numerous test devices, the parameters are consistently applied. Thereby, the agreement between simulation and experiment is excellent, which demonstrates the correctness and applicability of the developed model. Finally, the complete OLED is successfully simulated on the basis of the parameters that have been obtained in the analysis of the single-carrier devices. The simulation of the OLED illustrates the transport levels of electrons and holes, and proofs that the OLED efficiency is low because of non-radiative recombination in the interlayer between the phosphorescent and fluorescent emission zones. In this context, many interesting issues are discussed, e.g. the applicability of the Langevin model in combination with the mobility models for the description of recombination and the relevance of interactions between free charge carriers and excitons.

This study focuses on the investigation of the key parameters that determine the optical and electrical characteristics of inverted top-emitting organic light emitting diodes (OLED). A co-deposition of small molecules in vacuum is used to establish electrically doped films that are applied in n-i-p layered devices. The knowledge about the functionality of each layer and parameter is important to develop efficient strategies to reach outstanding device performances. In the first part, the thin film optics of top-emitting OLEDs are investigated, focusing on light extraction via cavity tuning, external outcoupling layers (capping layer), and the application of microlens films. Optical simulations are performed to determine the layer configuration with the maximum light extraction efficiency for monochrome phosphorescent devices. The peak efficiency is found at 35%, while varying the thickness of the charge transport layers, the semitransparent anode, and the capping layer simultaneously. Measurements of the spatial light distribution validate, that the capping layer influences the spectral width and the resonance wavelength of the extracted cavity mode, especially for TM polarization. Further, laminated microlens films are applied to benefit from strong microcavity effects in stacked OLEDs by spatial mixing of external and to some extend internal light modes. These findings are used to demonstrate white top-emitting OLEDs on opaque substrates showing power conversion efficiencies up to 30 lm/W and a color rendering index of 93, respectively. In the second part, the charge carrier management of n-i-p layered diodes is investigated as it strongly deviates from that of the p-i-n layered counterparts. The influence of the bottom cathode material and the electron transport layer is found to be negligible in terms of driving voltage, which means that the assumption of an ohmic bottom contact is valid. The hole transport and the charge carrier injection at the anode is much more sensitive to the evaporation sequence, especially when using hole transport materials with a glass transition temperature below 100°C. As a consequence, thermal annealing of fabricated inverted OLEDs is found to drastically improve the device electronics, resulting in lower driving voltages and an increased internal efficiency. The annealing effect on charge transport comes from a reduced charge accumulation due to an altered film morphology of the transport layers, which is proven for electrons and for holes independently. The thermal treatment can further lead to a device degradation. Finally, the thickness and the material of the blocking layers which usually control the charge confinement inside the OLED are found to influence the recombination much more effectively in inverted OLEDs compared to non-inverted ones.

Smartphones, schnell faltbar für die Hosentasche, ein Laptop, dünn wie Papier mit gestochen scharfem Kontrast, transparente Displays in Windschutzscheiben von Fahrzeugen, oder Fensterscheiben - Diese Technologien werden zunehmend als reale Szenarien diskutiert und haben Eines gemeinsam. Ihre Verwirklichung wird erst durch den Einsatz organischer Leuchtdioden (engl. organic light emitting diode, OLED) ermöglicht. Vor allem in internetbasierten Technologien, sowie neuartiger Displaytechniken und modernem Lichtmanagement wurde das Potential der OLEDs von der Industrie erkannt. Im Vergleich zu herkömmlichen Leuchtmitteln zeichnen sich OLEDs durch eine hohe Energieeffizienz aus. Ihre herausragende Eigenschaft als einzige Lichtquelle, direkt flächiges Licht abzugeben und zudem die Möglichkeit des Aufbaus aus flexiblen, transparenten Dünnschichten geben den OLEDs eine Sonderstellung für diese zukünftigen Anwendungen. Auch die steigende Anzahl an OLED-gestützten Produkten wie Bildschirmen, Smartphones und anderen Displaybauteilen zeigt diesen Trend deutlich. Dabei besteht für die industrielle Nutzung jedoch noch Forschungsbedarf. Diese Maßnahme wird mit Mitteln aus dem Europäischen Sozialfond gefördert und mitfinanziert durch Steuermittel auf Grundlage des von den Abgeordneten des Sächsischen Landtags beschlossenen Haushaltes.

The scientific research on organic luminescent molecules is a broadly diversified field.In the present work, two topics have received special attention: First, room-tem-perature phosphorescence (RTP) in amorphous organic layers, and second, specialapplications of organic LEDs (OLEDs). Since the phosphorescence as a transition between a triplet and a singlet state is notspin conservative, it is natively very slow and is usually overlaid by non-radiativetransitions. Experiments on triplet states are therefore often performed at low tem-peratures. Escaping this limitation, the topic of RTP arises, wherein biluminescenceis a special case. This means that phosphorescence and fluorescence can be observedsimultaneously and special attention is paid to the interaction of the two processes. After a theoretical and methodological introduction, this work transfers an establishedmethod for the determination of the photoluminescence quantum yield (PLQY) tobiluminescent and RTP systems. Among other things, it was shown that interactionsbetween the states must be taken into account in order to obtain correct results.Different physical competences can and must be combined, for example to detect thesole phosphorescent contribution to the PLQY of a biluminescent system. However,there is no literature on the consideration of statistical measurement uncertaintiesduring the PLQY acquisition itself. This gap could be closed by developing a methodthat cleverly exploits the measurement principle to obtain a broad statistical basis fordata analysis with moderate additional experimental effort. This evaluation methodhas its strength especially in the fact that it is independent of the actually investigatedobject and thus has relevance beyond research on organic emitters. The following chapter deals with more basic properties of RTP, analysing a num-ber of molecules that can be interpreted as fragments of the well-known tetra-N-phenylbenzidine (TPB). Using a combination of optical characterization and quan-tum mechanical simulations, the twisted biphenyl-core of TPB has been identified asthe basic molecular building block for efficient radiative triplet-singlet transitions. The systematics coming with a series of similar molecules, was further used to developa numerical fit routine for biluminescent processes. Different numbers of bromineatoms were synthetically attached to TPB, which creates a heavy-atom effect thatenhances spin flips and thus triplet-singlet transitions. Mathematically, the dynamicsof the transition processes can be described with a system of coupled differentialequations. The core elements therein are the transition rates, which reflect the timeconstants of the corresponding processes. Radiative and non-radiative transitions aswell as intermolecular interactions could be quantified that way. The last part of the thesis deals with the physics of OLEDs and the developmentof particular OLED applications. Especially the concept of AC/DC OLEDs is deep-ened, which allows an operation with alternating current (AC) by a combination ofdirect-current (DC) components. The big advantage of this design is the independentcontrollability of two diodes within one light source. This allows, for example, thecontinuous adjustment of the emission colour over a wide range. Further improve-ments such as transparency and improved colour rendering are the results of thiswork. Finally, the AC/DC strategy was transferred to a completely new application,in which spatially different radiation characteristics are developed and exploited.:Abstract List of Publications List of Abbreviations I Fundamentals 1 Introduction 2 Organic Luminophores 2.1 Physical Basics of Organic Molecules 2.1.1 Molecular Orbitals 2.1.2 Spin States of Molecules 2.2 Transitions 2.2.1 Jablonski Diagrams 2.2.2 Singlet-Triplet Transitions 2.3 Non-Linear Processes 2.3.1 Förster and Dexter Transfer 2.3.2 Bimolecular Annihilation Processes 2.3.3 Other Quenching Mechanisms 2.4 Room-Temperature Phosphorescence and Biluminescence 2.5 Rate Equations for Luminescent Molecules 3 Methods and Techniques 3.1 Materials 3.1.1 Materials for Biluminescence and RTP Experiments 3.1.2 OLED Materials 3.1.3 PLQY Reference Samples 3.2 Sample Preparation 3.2.1 Spin Coating 3.2.2 Thermal Evaporation 3.3 Setups for Photoluminescent characterization 3.3.1 Enterprise 3.3.2 Time-Correlated Single Photon Counting 3.3.3 PLQY Setup 3.3.4 Fluoromax 3.4 Setups for OLED characterization 3.4.1 DC Electroluminescence 3.4.2 AC Electroluminescence 3.4.3 Beam-Shaping Profiles 3.4.4 Transparency 3.5 Line Shape Analysis of Emission Spectra II Biluminescence of Organic Molecules 4 Photoluminescence Quantum Yield (PLQY) Measurements 4.1 Measurement and Evaluation Procedure 4.2 Experimental Influences on the Results 4.2.1 Importance of the B Measurement 4.2.2 Calibration of the Setup 4.2.3 Other Systematic Errors 4.3 Data Evaluation 4.3.1 Subtraction of the Background 4.3.2 Choosing the Wavelengths for Evaluation 4.3.3 Statistical Data Analysis 4.3.4 Reabsorption in the Sample 4.4 Application of PLQY Measurements 4.4.1 PLQY Values of Reference Samples 4.4.2 The PLQY of Biluminescent Samples 4.4.3 Negative PLQY and the Influence of Quenching 5 TPB fragments 5.1 Motivation and Scope of the Experiment 5.2 Spectroscopic Characterization 5.3 Discussion of the Results 6 Brominated TPB as Test Case for Rate Equation Fitting 6.1 Scope and Expectations 6.2 The Heavy-Atom Effect 6.3 Estimation of the ISC Rate 6.4 Rate Equation Fitter 6.4.1 Experimental Input parameters 6.4.2 Determination of𝑘rand𝑘nr 6.4.3 Discussion of the Fit Routine 6.4.4 Data Acquisition and Experimental Influences 6.5 PL Characteristics of the BrxTPB-Series 6.6 Fit Curves and Numerical Values 6.7 Discussion 7 Summary of Part II III Organic Light-Emitting Diodes 8 Introduction and Theoretical Background 8.1 OLEDs in the Framework of This Thesis 8.2 Introduction and Recent Advances 8.3 Organic Semiconductors and Light-Emitting Diodes 8.3.1 Charge Carrier Transport 8.3.2 Organic Diode Structure 8.3.3 Luminescent Measures 8.3.4 The Emission Colour 8.3.5 Efficiency Parameters of OLEDs 9 Advances in AC/DC OLEDs 9.1 Transparent and colour-tunable OLEDs 9.2 Real-Time Beam Shaping OLEDs 9.2.1 The Influence of the Cavity Mode 9.2.2 Angularly Confined Emission 9.2.3 Results and Discussion 10 Angular resolved EQE 11 Summary of Part III Appendix A Low Intensity Noise of the Spectrometer B Calculation of the Density of Triplet States C User Manual for Grape C.1 The Figures C.2 Options C.3 Outputs C.4 Internal Data Processing D TPB-Fragments: Line-Shape Analysis E BrxTPB Fit Curves F Side projects Bibliography Acknowledgements / Die wissenschaftliche Forschung an organischen lumineszenten Molekülen ist ein breitgefächertes Themenfeld. In der hier vorliegenden Arbeit fanden besonders zwei The-men Beachtung: zum einen die Raumtemperaturphosphoreszenz (RTP) in amorphenorganischen Schichten, und zum anderen spezielle Anwendungen organischer LEDs(OLEDs). Da die Phosphoreszenz als Übergang zwischen einem Triplett- und einem Sigulettzu-stand nicht spinerhaltend ist, ist er nativ sehr langsam und wird meist von nicht-strahlenden Übergängen überlagert. Häufig finden Experimente zu Triplettzustän-den daher unter sehr niedrigen Temperaturen statt. Diese Einschränkung entgehend,ergibt sich das Themenfeld der RTP, worin die Bilumineszenz ein Spezialfall ist. Dasbedeutet, dass zeitgleich Phosphoreszenz und Fluoreszenz beobachtbar sind und einbesonderes Augenmerk auf dem Wechselspiel der beiden Prozesse liegt. Nach einer theoretischen und methodischen Einführung, wird in der vorliegenden Ar-beit eine etablierte Methode zur Bestimmung der Photolumineszenzeffizienz (PLQY)auf bilumineszente und RTP-Systeme übertragen. Unter anderem zeigte sich hierin,dass besonders Interaktionen zwischen den Zuständen berücksichtigt werden müssen,um korrekte Ergebnisse zu erhalten. Unterschiedliche physikalische Kompetenzenkönnen und müssen kombiniert werden, um zum Beispiel den alleinigen phospho-reszenten Anteil an der PLQY eines biluminszenten Systems zu detektieren. Aller-dings existiert keine Literatur zur Berücksichtigung statistischer Messunsicherheitenwährend der PLQY Detektion. Diese Lücke konnt durch eine entwickelte Methodegeschlossen werden, die das Messprinzip geschickt ausnutzt, um mit moderatem ex-perimentellem Mehraufwand eine breite statistische Basis zur Datenanalyse zu erhal-ten. Diese Auswertemethode hat ihre Stärke besonders darin, dass sie vom eigentlichuntersuchten Objekt unabhängig ist und damit auch Relevanz jenseits der Forschungan organischen Emittern hat. Im anschließenden Kapitel werden grundlegendere Eigenschaften der RTP behandelt,wobei eine Reihe an Molekülen analysiert wird, die als Fragmente des bekannten tetra-N-phenylbenzidine (TPB) interpretiert werden können. Mit einer Kombination ausoptischer Charakterisierung und quantenmechanischen Simulationen konnte der ver-drillte Biphenylkern von TPB als der grundlegende molekulare Baustein für effizientestrahlende Triplett-Singulett-Übergänge identifiziert werden. Die Systematik, die Serien ähnlicher Moleküle mit sich bringen, wurde weiterhingenutzt, um eine numerische Anpassungsroutine für bilumineszente Prozesse zu ent-wickeln. TPB Moleküle wurden synthetisch mit verschiedener Zahl an Bromatomenversehen, was einen Schweratomeffekt erzeugt, der Spinumkehr und damit auch Trip-lett-Singulett-Übergänge verstärkt. Mathematisch kann die Dynamik der Übergangs-prozesse mit einen System gekoppelter Differentialgleichungen beschrieben werden.Die Kernelemente darin die Übergangsraten, die die Zeitkonstanten der entsprechen-den Prozesse widerspiegeln. In der vorliegendenden Arbeit konnten somit strahlendeund nichtstrahlende Übergänge, sowie intermolekulare Wechselwirkungen quantifi-ziert werden. Der letzte Teil der Arbeit befasst sich mit der Physik und der Anwendung von OLEDs.Besonders das Konzept der AC/DC OLEDs wird dabei vertieft, das durch eine Kom-bination aus Gleichstrombauteilen, einen Betrieb mit Wechselstrom ermöglicht. Dergroße Vorteil dieses Aufbaus ist die unabhängige Ansteuerbarkeit zweier Dioden in-nerhalb einer Lichtquelle. Das erlaubt zum Beispiel die stufenlose Einstellung derEmissionsfarbe über einen weiten Bereich. Weitere Verbesserungen wie Transparenzund eine verbesserte Farbwiedergabe sind Ergebnisse dieser Arbeit. Letztlich wurdedie AC/DC Strategie auf einen völlig neuen Anwendungsfall übertragen, in dem räum-lich verschiedene Abstrahlcharakteristiken entwickelt und ausgenutzt werden.:Abstract List of Publications List of Abbreviations I Fundamentals 1 Introduction 2 Organic Luminophores 2.1 Physical Basics of Organic Molecules 2.1.1 Molecular Orbitals 2.1.2 Spin States of Molecules 2.2 Transitions 2.2.1 Jablonski Diagrams 2.2.2 Singlet-Triplet Transitions 2.3 Non-Linear Processes 2.3.1 Förster and Dexter Transfer 2.3.2 Bimolecular Annihilation Processes 2.3.3 Other Quenching Mechanisms 2.4 Room-Temperature Phosphorescence and Biluminescence 2.5 Rate Equations for Luminescent Molecules 3 Methods and Techniques 3.1 Materials 3.1.1 Materials for Biluminescence and RTP Experiments 3.1.2 OLED Materials 3.1.3 PLQY Reference Samples 3.2 Sample Preparation 3.2.1 Spin Coating 3.2.2 Thermal Evaporation 3.3 Setups for Photoluminescent characterization 3.3.1 Enterprise 3.3.2 Time-Correlated Single Photon Counting 3.3.3 PLQY Setup 3.3.4 Fluoromax 3.4 Setups for OLED characterization 3.4.1 DC Electroluminescence 3.4.2 AC Electroluminescence 3.4.3 Beam-Shaping Profiles 3.4.4 Transparency 3.5 Line Shape Analysis of Emission Spectra II Biluminescence of Organic Molecules 4 Photoluminescence Quantum Yield (PLQY) Measurements 4.1 Measurement and Evaluation Procedure 4.2 Experimental Influences on the Results 4.2.1 Importance of the B Measurement 4.2.2 Calibration of the Setup 4.2.3 Other Systematic Errors 4.3 Data Evaluation 4.3.1 Subtraction of the Background 4.3.2 Choosing the Wavelengths for Evaluation 4.3.3 Statistical Data Analysis 4.3.4 Reabsorption in the Sample 4.4 Application of PLQY Measurements 4.4.1 PLQY Values of Reference Samples 4.4.2 The PLQY of Biluminescent Samples 4.4.3 Negative PLQY and the Influence of Quenching 5 TPB fragments 5.1 Motivation and Scope of the Experiment 5.2 Spectroscopic Characterization 5.3 Discussion of the Results 6 Brominated TPB as Test Case for Rate Equation Fitting 6.1 Scope and Expectations 6.2 The Heavy-Atom Effect 6.3 Estimation of the ISC Rate 6.4 Rate Equation Fitter 6.4.1 Experimental Input parameters 6.4.2 Determination of𝑘rand𝑘nr 6.4.3 Discussion of the Fit Routine 6.4.4 Data Acquisition and Experimental Influences 6.5 PL Characteristics of the BrxTPB-Series 6.6 Fit Curves and Numerical Values 6.7 Discussion 7 Summary of Part II III Organic Light-Emitting Diodes 8 Introduction and Theoretical Background 8.1 OLEDs in the Framework of This Thesis 8.2 Introduction and Recent Advances 8.3 Organic Semiconductors and Light-Emitting Diodes 8.3.1 Charge Carrier Transport 8.3.2 Organic Diode Structure 8.3.3 Luminescent Measures 8.3.4 The Emission Colour 8.3.5 Efficiency Parameters of OLEDs 9 Advances in AC/DC OLEDs 9.1 Transparent and colour-tunable OLEDs 9.2 Real-Time Beam Shaping OLEDs 9.2.1 The Influence of the Cavity Mode 9.2.2 Angularly Confined Emission 9.2.3 Results and Discussion 10 Angular resolved EQE 11 Summary of Part III Appendix A Low Intensity Noise of the Spectrometer B Calculation of the Density of Triplet States C User Manual for Grape C.1 The Figures C.2 Options C.3 Outputs C.4 Internal Data Processing D TPB-Fragments: Line-Shape Analysis E BrxTPB Fit Curves F Side projects Bibliography Acknowledgements

Thermally activated delayed fluorescence (TADF) has been proposed as a pathway to achieve high efficiency organic light-emitting diodes (OLEDs) without the use of heavy metal atoms in molecular structures. Many different factors can be decisive for efficient light emission from TADF emitters. However, a complete picture of the working mechanisms behind TADF is still missing and further research exploring novel material and device ideas is required. This thesis aims to extend the understanding of TADF emitter and OLED design considerations by investigating photophysical properties of novel materials as well as fabricating, optimizing and characterizing devices. TADF emitters have great potential of being used in OLEDs because they allow for high quantum efficiencies by utilizing triplet states via reverse intersystem crossing (RISC). In small molecules this is done by spatially separating the frontier orbitals, forming an intramolecular charge-transfer state (iCT) and leading to a small energy difference between lowest excited singlet and triplet states (Δ𝐸ST). In polymer emitters, sufficient frontier orbital separation is harder to achieve, and typical strategies usually include adding known TADF units as sidechains onto a polymer backbone. In this thesis, a novel pathway of TADF polymer design is explored. A shift from a non-TADF monomer to TADF oligomers is explored. The monomer shows non-TADF emission and the delayed emission is shown to be of triplet-triplet annihilation (TTA) origin. An iCT state is formed already in the dimer, leading to a much more efficient TADF emission. This is confirmed by an almost two-fold increase of photoluminescence quantum yield (PLQY), a decrease in the delayed luminescence lifetime and the respective spectral line shapes of the molecules. Recently, intermolecular effects between small-molecule TADF emitters have been given more attention, revealing strong solid-state solvation or aggregation induced changes of sample performance. Implications of this on device performance are not yet fully covered. A thorough investigation of a novel TADF emitter 5CzCO2Me is conducted. Steady-state emission spectra reveal a luminescence redshift with increasing emitter concentration in a small molecule host. In all investigated concentrations, the emission profile remains the same, thus the redshift is attributed to the solid-state solvation effect. The highest photoluminescence quantum yield (PLQY) is achieved in the 20 wt% sample, reaching 66 %. The best OLED in terms of current-voltage-luminance and external quantum efficiency parameters is the device with 60 wt% emitter concentration, reaching maximal EQE values of 7.5 %. It is shown that the emitter transports holes and that charge carrier recombination does not take place on the bandgap of the host, but rather, a mixed host-guest concentration dependent recombination is seen. The hole transporting properties of 5CzCO2Me allows for a new dimension in tuning the device performance by controlling the emitter concentration.