High performance optoelectronic applications require simultaneously high mobility ($\mu$) and high quantum efficiency of fluorescence ($\Phi$). While this has been realised for organic small molecule semiconductors, applications such as high efficiency organic photovoltaics and bright organic light-emitting diodes towards electrically driven lasing are hampered by an apparent trade-off between $\mu$ and $\Phi$ in disordered systems. Recent reports of state-of-the-art device performance often optimise $\mu$ and $\Phi$ in disordered organic materials separately, and employ multi-layer architectures. In this work, we investigate materials in a class of donor-acceptor polymer materials; the indacenodithiophene-$\textit{alt}$-benzothiadiazole family, which demonstrate high $\mu$ in spite of a low long-range structural order, to understand the interplay between these two important device figures-of-merit. In the first section, we evaluate the effect of various tuneable parameters on $\mu$ and device performance in organic field-effect transistors. Using chemical modifications to the solubilising side chains, we observe that the substitution of bulky groups leads to a reduction of the hole mobility $\mu_h$ > 2 cm$^{2}$/Vs to ~ 0.5 cm$^{2}$/Vs in the benchmark polymer of this family, indacenodithiophene-$\textit{alt}$-benzothiadiazole. Crystallographic and exciton-quenching based experiments confirm this observation is closely related to the degree of polymer backbone aggregation, and this leads to a different temperature evolution of the transport behaviour. In order to reliably improve $\mu$ in these systems, an elongation of the donor subunit is required. This increases the $\pi$-electron density on the donor, and can lead to an improvement in $\mu$ where the side chain density is decreasing. This chemical design, leading to a more highly aggregated structural motif is much more potent in determining $\mu$, it seems, than design strategies to further improve the energetic disorder in the joint density of states and the potential barrier to torsion, which may be near optimised in these low-disorder systems. In the second section, we unpick the precise relationship between the degree of aggregation apparently linking high $\mu$ to low $\Phi$. With a prototype system, we compare the photophysics of two indacenodithiophene-$\textit{alt}$-benzothiadiazole polymers differing by side chain bulkiness. Despite the aforementioned suppression of $\mu$, we observe an improvement to $\Phi$ of $< 0.02$ to $\sim 0.18$ upon backbone separation. This derivative has the highest $\Phi$ reported for any polymer with $\mu$ exceeding that of amorphous-Si. However, the $\Phi$ in the more aggregated derivative is not limited by the formation of non-emissive excitons, but rather by an additional internal conversion pathway which is strongly temperature dependent, and mediated by Raman-active vibrations and close chain coupling. Extending this study, we analyse additional materials in this family with the highest $\Phi \cdot \mu$ values reported for conjugated polymers. We find that increasing the energy gap leads to an increase in $\Phi$, and secondary emission pathways via weakly luminescent inter-chain charge transfer species. By solving the rate equations for exciton recombination, we use the radiative rate of inter-chain luminescence as a probe to show strong wavefunction mixing at close-contact points for some polymers, and suggest this as the origin for a superior $\mu$ in dithiopheneindenofluorene-$\textit{alt}$-benzothiadiazole compared to indacenodithiophene-$\textit{alt}$-benzothiadiazole. We demonstrate how low $\mu$ can be decoupled from the energy gap ($E_g$), and propose backbone elongation leading to increased inter-chain wavefunction overlap and a higher $E_g$ as a design rule to increase $\Phi$ and $\mu$ together. Finally, we assess the role of low-frequency vibrations in organic semiconductors displaying thermally activated delayed fluorescence (TADF). In the low-aggregation limit where $\Phi$ is maximised, we show that non-radiative triplet recombination is strongly related to low frequency torsional motion, and both are reduced in the presence of a rigid polymer host matrix for various TADF materials across different classes. However, we also explore the importance of rotational freedom in determining the oscillator strength, exchange energy, and spin-orbit coupling matrix elements which mediate luminescence in the absence of a rigid host. We demonstrate that suppressing dynamic motion is a powerful tool to modulate the photophysical properties of these emitters, and can lead to improved $\Phi$ particularly for low $E_g$ emitters.

Eine Reihe 9,9-dialkylsubstituierter Polyfluorene mit linearen und verzweigtkettigen Alkylsubstituenten und einem Molekulargewicht von bis zu 200000 g/mol wurde synthetisiert und charakterisiert. Darüber hinaus wurden einige dieser Polymere mit einer geeigneten 'Lochtransport'-Funktionalität (Triphenylamin-Derivate) ausgestattet, um die Ladungstransporteigenschaften und das Molekulargewicht dieser Substanzen zu kontrollieren. Die thermische Orientierung dieser neuen Polymere auf geriebenen Polyimid-Schichten führte zu hoch anisotropen Filmen mit großen dichroischen Verhältnissen (Absorption parallel und senkrecht zur Reibungsrichtung gemessen). Ferner wurde eine Gruppe chiraler Polyfluorene synthetisiert und hinsichtlich ihrer chiroptischen Eigenschaften untersucht. Der mit diesen chiralen, konjugierten Polymeren erreichte Grad der Anisotropie in Absorption (CD), circular polarisierter Photolumineszenz (CPPL) und Elektrolumineszenz (CPEL) überstieg die bis dahin bekannten Werte um einen Faktor von 200. / A series of 9,9-dialkyl-poly(fluorene-2,7-diyl)s containing linear and branched alkyl substituents with a molecular weight of up to 200000 g/mol has been synthesized and characterized. Moreover, some of the polymers were end capped with a suitable hole transport functionality, such as a triphenylamine derivative, to improve their charge transport properties and to control the molecular weight. The thermal alignment of these novel polymers on a rubbed polyimide layer led to highly anisotropic film formation with large dichroic ratios (absorption parallel and perpendicular to the rubbing direction). Additionally a set of chiral polyfluorenes has been synthesized and investigated with respect to their chiroptical properties. The degrees of anisotropy in absorption (CD), circular polarized photoluminescence (CPPL) and electroluminescence (CPEL) found with these chiral conjugated polymers exceeded the yet known values by a factor of 200.

The high performance organic light-emitting diodes (OLEDs) have been studied. First, we have fabricated a WOLED with AlF3 and m-MTDATA as a hybrid buffer layer. Results indicate that the turn-on voltage can be reduced to 3.1V, and the luminous efficiency can be improved to 14.7 cd/A when a hybrid buffer layer was used. Since the turn-on voltage decreases and the efficiency increases, the power consumption as well as lifespan are then improved. Moreover, the luminous efficiency of the hybrid buffer layer devices also immunes to drive voltage variations. Second, we studied the properties of transportation in OLEDs. The study presented the device of a WOLED with a combination of a graded hole transport layer (GH) structure and a gradually doped emissive layer (GE) structure as a double graded (DG) structure. The DG structure: ITO/MTDATA(15 nm/NPB(15 nm)/NPB:25% BAlq (15 nm)/NPB : 50% BAlq (15 nm)/BAlq:0.5% Rubrene (10 nm)/ BAlq : 1% Rubrene (10nm) /BAlq:1.5%Rubrene (10 nm) / Alq3 (20 nm)/ LiF (0.5 nm)/Al (200 nm) is beneficial for improving both electrical and optical performances. The luminous efficiency of the DG device is 11.8cd/A, which is larger than that of 7.9cd/A with the HJ device. This improvement is attributed to the discrete interface between hole transport layer and emissive layer can be eliminated, surplus holes can be suppressed, electron-hole pairs can obtain optimal transportation and recombination in the emissive layer, and quenching effects can be significantly suppressed. Moreover, the spectra were almost not changed with an increasing drive current. As the efficiency was improved, it is expected that the power consumption can be reduced as well. Third, high efficiency and brightness p-i-n OLEDs with a CsI-doped Alq3 layer as a n-ETL has been studied. The p-i-n WOLED with a 15 % CsI-doped Alq3 layer exhibits a luminous efficiency of 5.75 cd/A at a driving current of 20mA/cm2 as well as a maximum power efficiency of 4.67lm/W. This improved performance is attributed to the increased electron carriers of the n-ETL and the balance of electrons and holes in the recombination zone. The X-ray photoelectron spectroscopy (XPS) have shown that doping of CsI caused chemical reaction, attributing to the increase of carriers. Finally, we focus on the improvement of contrast ration (CR) of OLEDs. We successfully fabricated a conductive organic-metal light-absorbing layer with a high CR and low reflectance for use as a black cathode in an OLED. The black cathode that was fabricated using vacuum deposition has the advantages of low cost and simple fabrication. Moreover, the J-V characteristic of the black cathode device is almost identical to that of a conventional device. Additionally, the reflectance can be reduced from 66.2% to 11.3% and a small reflectance variation around 3.3% over the visible spectrum is appealed. At an ambient illumination of 250 lx, the CR can be increased from 4.2 to 10.8 at a brightness of 250 cd/m2.

Recently, tandem white organic light-emitting diodes are attracting a great deal of interest due to their potential illumination applications. A tandem structure is a mean two or more electroluminescence units that joined together through connecting units in series. So, we can make sense that the connecting unit has play an important role in this particular structure. In my paper research, the functions of connecting units are usually being considered with two aspects: charge transporting and charge generation. But, it was rarely discussed which function is the key point. Three devices were fabricated in this study : (¢¹) unit device, (¢º) tandem device 1 with connecting layers of Alq3:Li/MoO3 and (¢») tandem device 2 with connecting layers of Alq3:Li/HAT-CN. Base on this two connecting unit structure, we can get a quantifiable data from adopting, carrier transporting and carrier generation and figure out which function of connecting unit in tandem device is the main factor. The unit device has outstanding performance comparing to others fluorescence white OLED. It exhibits a maximum luminance of 49820 cd/m2 at 1755 mA/cm2, the power efficiency of 2.52 lm/W at 20 mA/cm2 and CIE (0.33, 0.33). But the power efficiency decreased to 2.07 lm/W at 20 mA/cm2 in tandem device 1. In order to improve device performance, we choose new material HAT-CN to replace to MoO3. From our result, the tandem device 2 have increase power efficiency from 2.07 lm/W to 2.24 lm/W at 20 mA/cm2, and the maximum luminance reach 71790 cd/m2 at 650 mA/cm2 with CIE(0.30, 0.39). We want to figure out why the power efficiency increased after using HAT-CN in tandem device. So we further designed and fabricated the hole only device, electron only device and capacitance device to figure out the charge transporting and charge generation behavior between these two connecting unit constructed based on Alq3:Li/MoO3 and Alq3:Li/HAT-CN. After analyzing the results of these devices, we found that the charge generating plays a major role in tandem OLED¡¦s performance. In other words, if the more carriers can be generated in the connecting layers, the higher power efficiency in tandem device can be realized.

OLEDs for display and lighting applications were studied. Both RGB and color filter technologies were discussed in the display section; meanwhile, RGB white light and tendem white light were discussed in the lighting section. A high performance RGB white display using 1,3,5-tri(1-pyrenyl) benzene (TPB3), C545T (166000 cd/m2) and DCJTB (70600 cd/m2) has been prepared with a 53.3% color gamut. For the color display using PLED technology, a glycerol modified PEDOT (G-PEDOT) is used as buffer layer material. Luminance of the white PLED display increases significantly from 11580 cd/m2 to 16040 cd/m2. A 54.5% color gamut color display is prepared using the white PLED device with a color filter. RGB white device with maximum luminance of 55800 cd/m2, maximum luminance efficiency of 4.55 cd/A, maximum power efficiency of 3.85 lm/W, and CIE coordinate of (0.33, 0.32) is prepared with a device structure of ITO(1300A)/NPB(500A)/TPB3(200A)/DPVBi¡G2% DSB(150A)/Alq3¡G2% DCJTB (150A)/ Alq3(350A)/LiF(8A)/Al(2000A). A high performance single emission layer white OLED device is also prepared. This single-layer device achieves a maximum luminance of 95200 cd/m2, maximum luminance efficiency of 5.9 cd/A, maximum power efficiency of 4.06 lm/W, and CIE coordinate of (0.34, 0.39) with a device structure of ITO(1300A)/NPB(650A)/TPB3:6% DSB:0.6% DCJTB(400A)/Alq3(300A)/LiF(8A)/Al(2000A). Optimization of a tandem OLED device is conducted using a Alq3¡GLi/ HAT-CN interlayer. It is found that turn-on voltage is reduced effectively using the Alq3¡GLi/ HAT-CN interlayer at 20 mA/cm2. Power efficiency is increased to 2.24 lm/W, and maximum luminance of 71790 cd/m2 is achieved with a CIE coordinate of (0.30, 0.39).

The development of new charge transport materials for use in phosphorescent organic light-emitting diodes (OLEDs) remains an important area of research. In this thesis, several examples of carbazole-containing norbornene-based side-chain polymers were synthesized and studied. In addition, several examples of ambipolar transport moieties were produced by combining hole- (carbazole) and electron- (oxadiazole or triazole) transport groups and examined as both small molecules and as norbornene-based side-chain polymers. UV-visible absorption, fluorescence spectroscopy, cyclic voltammetry, and other methods were used to evaluate the properties of the charge transport materials for use as hole- and/or host layers. It was found that side-functionalization produced polymers with photophysical and electrochemical properties corresponding to the charge transport side groups attached. In addition, several crosslinkable hole-transporting materials (copolymer or small molecule-based) incorporating either benzocyclobutenes, trifluorovinyl ethers, oxetanes, or bis(styrene)s were developed. Thin-films of the crosslinkable materials were shown to be readily insolubilized by thermal treatment permitting the deposition of a subsequent layer from solution onto the crosslinked layer. OLEDs fabricated using several of these materials produced efficient devices. Overall, it was shown that side-chain functionalization can be used to afford solution-processable charge transport polymers where the properties are determined mainly by the side group attached. As such, this approach could be extended to additional examples of charge transport moieties.

<p>The presented thesis is devoted to the field of organic light emitting</p><p>diodes (OLEDs). Time-dependent Kohn-Sham density functional theory</p><p>(TDDFT) is applied</p><p>in order to eludicate optical properties such as fluorescence and</p><p>phosphorescence for some of the most important materials. The</p><p>accuracy of TDDFT is evaluated with respect to the calculated absorption</p><p>and emission spectra for commonly used light emitting polymers.</p><p>A continuation of this work is devoted to Polyfluorene as this polymer</p><p>has proven to be very promising. In this study the chain</p><p>length dependence of its singlet and triplet excited states is</p><p>analyzed as well as the excited state structures.</p><p>Understanding the phosphorescence mechanism of tris(2-phenylpyridine)Iridium is</p><p>of importance in order to interpret the high efficiency of OLEDs</p><p>containing these specimens. The mechanism is analyzed by calculating</p><p>the electric transition dipole moments by means of TDDFT using</p><p>quadratic response functions.</p><p>As not only the optical properties are essential for effective</p><p>devices, electron transfer properties are addressed. The electron</p><p>transfer capability of the sulfur and nitrogen analogues of Oxadiazole</p><p>is evaluated through their internal reorganization energy.</p>

<p>Organic Light Emitting Displays (OLEDs) are a new type of thin emissive displays predicted to possess superior properties to existing techniques e.g. Liquid Crystal Display (LCD). The main advantages are low power consumption and a thin display structure. This report contains an explanation of the emissive OLED technology, its functionality and the physics of the organic layer structure in an OLED. The technology is described with respect to the two classes of organic materials used in displays, small molecules and conjugated polymers. </p><p>The information is derived from a study of literature and from different measurements performed on a full-colour OLED microdisplay, based on colour filters. The evaluation of the OLED revealed the main disadvantage of an unsatisfactory lifetime of approximately only one week. The results of the measurements and study are furthermore compared to the traditional LCD technology. </p><p>A conclusion with the advantages and drawbacks with the OLED technology summarises the report together with a short analysis of the future for OLEDs, partly achieved through a written enquiry sent to approximately 20 possible OLED manufactures.</p>

科技的進步使得人類對於資訊的需求大量增加，各種不同的資訊接收裝置亦紛紛以各種型態被發明。對於資訊接受裝置的大量需求帶動了顯示技術的進步，從1924年俄國科學家佐理金發明了映像管到二十一世紀的今天，顯示技術已經進入了百家爭鳴的時代。 在眾多的顯示技術中，OLED顯示技術被視為最具有潛力的顯示技術之一。本研究係以台灣OLED作為研究對象，來了解OLED產業的投資機會。 研究結果顯示雖然OLED產業市場大，但是利潤均被上、中、下游所瓜分此外，被動式驅動PM-OLED將打進主流，成長可期。在投資方面，有機材料、鍍膜設備將會是良好的投資標的。

Triarylamine type materials with vastly altered physical properties are synthesized by hybridizing organic semiconducting structures with silicone and siloxane groups. By altering the silicon content of these materials, we can tune their physical composition from free flowing liquids, to amorphous glasses, to cross-linked films. Much of this modification is enabled by the unique use of a metal-free Si-H activation chemistry; the Piers-Rubinsztajn reaction. This chemistry is demonstrated to be a general and rapid way to build up hybrid semiconducting structures. Key to the utility of these materials in electronic devices, it is shown that hybridization with silicon groups has a negligible effect on the useful electrochemical properties of the base materials. Building on this, it is shown that charge carrier mobility through a prototypical liquid organic semiconductor is similar to the base materials and transport is described by existing dispersive transport theories. Finally, two side projects in the area of organic electronics are discussed. New phthalonitrile based fluorophores are characterized and their utility as deep-blue emitting dopants in organic light emitting diodes is demonstrated. These same π-extended phthalonitriles can also be used as precursors to new red-shifted BsubPcs which display exceptional electrochemical stability and tuning.