Using X-ray photoelectron (XPS) and X-ray absorbtion spectroscopy (XAS) we demonstrate charge transfer at an interface between two transition metal phthalocyanines, MnPc and F16CoPc, resulting in charged MnPc + and F16CoPc -, species. Density functional theory calculations reveal that a hybrid state is formed between the two types of phthalocyanines, which causes this charge transfer. For the hybrid state the Mn3dxz interacts with the Co 3dz2 orbital leading to a two-level system. Moreover, we have prepared mixed films out of this pair, which were characterized also by means of electron energy-loss spectroscopy. Our data reveal the formation of MnPc/F16CoPc charge transfer dimers in analogy to the heterojunction. The electronic excitation spectrum of these blends is characterized by a new low energy excitation at 0.6 eV.

The formulation induced photooxidative stability of substituted 6, 13 trialkylsilylethynylpentacene derivatives is report for the first time. It is known that 6,13 trialkylsilylethynylpentacene derivatives undergo rapid oxidation through singlet oxidation and is believed to be primarily to the 6,13 endoperoxide. The effect of solvent, organic semiconductor concentration and the presence of polymeric binder on the rate of photooxidative degradation in oxygen saturated solutions on degradation kinetics have been investigated. The photochemical stability of 6,13 trialkysilylethynylpentacene has been studied in toluene, THF, dichloromethane, chloroform, decane and dodecane at concentrations ranging from 2.5×10-6 M to 5×10-2 M by measurement of the half-life by UV-visible spectroscopy. The predominant degradation products of TIPS-Pentacene are the same regardless of solvent and concentration, being predominantly an endo-peroxide resulting from O2 addition across the 6, 13 position of the pentacene. At low concentration (< 1×10 -3 M), the half- life of TIPS-Pentacene is observed to vary with solvent and the amount of dissolved oxygen, with half-life showing a strong, positive correlation between the product of the Hansen Solubility Parameter (HSP) and the mole-fraction oxygen solubility. In this range, the half-life is observed to increase markedly with increasing solution concentration, showing a linear correlation with mean intermolecular distance within the solution. From intermediate to high concentration, the half-life increase more rapidly with increasing concentration, which is attributed to aggregation. In most solvents, this behaviour shows a specific onset point, suggesting a cooperative rather than isodesmic aggregation mechanism. Photooxidative half-lives of TMTES-pentacene and fluorinated soluble pentacene derivatives were determined from 2.5 × 10-6 M to 5.0 × 10-3 M solutions in THF, toluene, chloroform and CH2Cl2. Independent of solvent and at constant concentration the relative ordering of photo-oxidative resistance was: α-di-FTIPS-pentacene > β-di-FTIPS-pentacene, α-mono -FTIPS-pentacene, β-mono-FTIPS-pentacene > TIPS-pentacene ≥ TMTES-pentacene. The same rank order for a particular derivative was generally maintained over the concentration range 2.5 x 10-6 M to 5 x 10-3 M the stability to photooxidation for all derivative increased with increasing concentration. All derivatives showed a mixture of endooxidation products as shown by APCI mass spectrometry, and 1H NMR.Added polystyrene and isotactic polystyrene were found to accelerate photooxidative degradation whist isotactic polymethylmethacrylate (i-PMMA) and poly (triaylamine) (PTAA) had no effect adding weight to the argument that anything which can act as an acceptor to the solution slows down the degradation and anything which impairs pair-wise energy transfer speeds up the degradation. Understanding of these phenomena is therefore essential for the further application of solution processing of organic materials.

A collection of 4,10-chrysene derivatives was prepared via the BHQ (Bull-Hutchings- Quayle) reaction, their electronic and morphological properties analysed and assessed for suitability as organic semiconductor (OSC) materials. Larger polycyclic aromatic hydrocarbons (PAHs) such as benzo[k]tetraphenes and dinaphtho[1,2,-b:1',2'- k]chrysenes were then prepared and similarly characterised. An acene-based OSC material TMTES-pentacene was also prepared. It is proposed that non-linear PAH- based OSC materials may provide an alternative to popular acene-based materials; offering advantages in stability, diversity and handling.

In this thesis, I utilize first principles density functional theory (DFT) based calculations to investigate the structure and electronic properties including charge transfer behaviors and work function of two types of materials: pentacene based organic semiconductors and ZnO transparent conducting oxides, with an aim to search for high mobility n-type organic semiconductors and fine tuning work functions of ZnO through surface modifications. Based on DFT calculations of numerous structure combinations, I proposed a pentacene and perfluoro-pentacene alternating hybrid structures as a new type of n-type semiconductor. Based on the DFT calculations and Marcus charge transfer theory analysis, the new structure has high charge mobility and can be a promising new n-type organic semiconductor material. DFT calculations have been used to systematically investigate the effect of surface organic absorbate and surface defects on the work function of ZnO. It was found that increasing surface coverage of organic groups and decreasing surface defects lead to decrease of work functions, in excellent agreement with experimental results. First principles based calculations thus can greatly contribute to the investigating and designing of new electronic materials.

This thesis concerns itself with the scientific study of the recently discovered organic magnetoresistance (OMAR) whose underlying mechanism is currently not known with certainty. As an introduction, we briefly review the major findings from prior work done by my colleagues. They found that OMAR can be as large as ~10% magnetoresistance at 10 mT magnetic fields at room temperature. Both OMAR and other kinds of magnetic field effect data in organics can be fitted using the empirical laws B^2/(B^2+B_0^2) or B^2/(|B|+B_0)^2, dependent on material. The fitting parameter B_0 is a measure of the characteristic magnetic field strength of OMAR. We explore the dependence of B_0 on material parameters to clarify the origin of OMAR. Various pi-conjugated semiconductor OMAR devices were studied to explore the possibility that hyperfine interaction causes OMAR. For a quantitative analysis of the experiments, we developed a theoretical fitting formula to relate B_0 to the hyperfine coupling strength. In addition, organic materials with different spin-orbit coupling strengths were also measured. Fluorescence and phosphorescence spectroscopies were used to estimate the spin-orbit coupling strength from the measured spectra. For analyzing our measurements, we developed a fitting formula from the time-dependent Schrodinger equation that takes into account the combined effect of hyperfine and spin-orbit coupling on spin-dynamics. We found that in the case of strong spin-orbit coupling, it dominates the behavior, resulting in magnetic field effect traces that are much wider than those in ordinary organics. However, a small cone remains at zero field with a width equal to the hyperfine coupling strength. We find qualitative agreement between the experimental results and the model. We also investigated the question whether OMAR is related to an excitonic effect, or is primarily a transport effect. We measured the magnetic field effects on current, photocurrent and electroluminescence to address this question. By varying the injection efficiency of the minority carriers, we show that OMAR most likely is not an excitonic effect. Our results provide strong evidence in support of the claim that OMAR is caused by spin-dynamics. However, further study is required to study the mechanism connecting spin-dynamics and conductivity.

L’organique électronique, qui repose sur l’utilisation de molécules et macromolécules fi-conjuguées comme semi-conducteurs dans divers dispositifs électroniques, connaît un essor considérable depuis une vingtaine d’années. L’utilisation de molécules organiques octroie de nombreux avantages vis-à-vis du silicium actuellement largement utilisé comme semi-conducteur. Citons par exemple la facilité de mise en oeuvre et la flexibilité méca- nique. La synthèse de nouvelles structures moléculaires est un axe important pour la mise au point de semi-conducteurs organiques plus performants mais aussi pour fournir les systèmes physiques nécessaires à la compréhension des processus physico-chimiques inhérents au transport de charges. Le paramètre primordial pour déterminer la qualité des semi-conducteurs est la mobilité des charges (μ), soit l’efficacité avec laquelle les charges se déplacent au sein des matériaux pi-conjugués. Il n’est pas impossible, qu’un jour, les performances des semi-conducteurs organiques dépassent celles du silicium en raison de la grande diversité de structures moléculaires accessibles via la synthèse organique. Le contrôle de la dimensionnalité de la structure électronique dans les solides organiques moléculaires est crucial pour le développement des dispositifs électroniques organiques à hautes performances. La dimensionnalité correspond au nombre de dimensions de l’espace (1D, 2D, 3D) dans lesquelles les charges peuvent se déplacer, plus celle-ci sera faible, plus le transport de charges sera sensible aux défauts. Dans ce contexte, nous nous sommes basés sur l’étude menée par Schweicher et al. sur le 2,7-di-tert-butyl[1]benzothiéno[3,2- b]benzothiophène, présentant une dimensionnalité des propriétés du transport de charges proche de deux. Ce travail repose sur la synthèse et la caractérisation de semi-conducteurs moléculaires sur base du [1]benzothiéno[3,2-b]benzothiophène (BTBT) dans le but d’augmenter la dimensionnalité du transport de charges. Pour ce faire, différents groupements aromatiques mais également plusieurs substituants dont le tert-butyle ont été greffés au BTBT. Ce travail a permis de voir que la relation structure-propriétés est difficilement prédictible mais il s’avère que la présence des groupements tert-butyles permet d’augmenter la dimensionnalité dans la plupart des cas. Cependant, lorsque des groupements 2-méthylnonyles sont utilisés à la place des tert-butyles, la structure cristalline des semi-conducteurs présentent généralement du désordre structural, néfaste aux propriétés du transport de charges. Du polymorphisme a aussi été décelé pour quelques semi-conducteurs munis de chaînes octyles. En plus de différents substituants, des groupements aromatiques ont été greffés au BTBT tels que des phényles, des thiényles, des bithiényles et également une unité BTBT pour former le dimère. Contre toute attente, l’allongement du système pi n’a pas conduit à la diminution du potentiel d’ionisation. Néanmoins, l’ajout de longues chaînes alkyles induit le rapprochement spatial des systèmes conjugués au sein de la maille cristalline, octroyant aux semi-conducteurs un potentiel d’ionisation plus faible ainsi que des intégrales de transport plus élevées, propices au transport de charges. Ce travail a permis également de faire une étude préliminaire du transport de charges au sein de monocristaux sur trois semi-conducteurs dont deux nouvellement synthétisés. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Quantum coherence plays a vital role in the excitonic properties of organic semiconductors. Several theoretical and experimental studies have shown an unprecedented role of coherence in charge transfer and transport processes, which in turn can improve the performance of electronic devices. Specifically, an enhancement of exciton coherence size can result in fast energy transport and efficient charge separation. The ability to tailor the design and performance of organic electronics based on exciton coherence effects represents the possibility of ultrafast electronic applications in communication and information technology. The objective of this thesis is the excitonic coherence studies of 1D crystalline thin films of phthalocyanine-based organic semiconductors using steady-state and time-resolved photoluminescence spectroscopy (TRPL). One of the main focuses of this work is on investigating the correlation of intermolecular interactions, $\pi$ orbital overlap and dynamic disorders on the excitonic coherent behaviors in crystalline thin films of various phthalocyanine derivatives (i.e. H$_2$TPP, H$_2$OBPc, H$_2$OCPc, and H$_2$OBNc). Specifically, coherence lengths, exciton-phonon coupling strengths and the nearest neighbor (NN) interaction strengths are determined via: (1) the PL ratio of the excitonic coherence transition and its first vibrational replica and (2) the temperature evolution of radiative recombination lifetimes of coherent excitons. This study showed that the optimum coherence size and the robustness of excitonic coherence can be achieved by a complex interplay between NN interaction, vibrational energies and the coupling to vibrational modes. In particular, it is shown that the shortest NN distance does not ensure the achievement of maximum coherence length within the four investigated phthalocyanine species. Instead, the largest coherence length is measured in the octabutoxy derivative, where the saddle shape of the molecule and crystalline packing results in weaker coupling to the acoustic phonons modes despite having larger intermolecular NN distance. In addition, the effect of static and dynamic disorders on the behavior of exciton coherence is explored by alloying two phthalocyanine derivatives that are close in band gap energies and possess large coherence lengths, H$_2$OBPc and H$_2$OBNc. This study demonstrated the successful tuning of exciton coherence lengths and excitonic parameters in organic analogues of semiconductor alloys, H$_2$OBNc$_x$H$_2$OBPc$_{1-x}$. Furthermore, the correlation of exciton-phonon coupling and radiative recombination rate of coherent excitons with increasing alloy concentration or static disorders are successfully revealed.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第20933号 / 理博第4385号 / 新制||理||1630(附属図書館) / 京都大学大学院理学研究科化学専攻 / (主査)教授 長谷川 健, 教授 倉田 博基, 教授 小野 輝男 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

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Der Schwerpunkt dieser Arbeit liegt auf der Simulation, Entwicklung und Realisierung organischer Halbleiterbauelemente für Anwendungen im Bereich der Sensorik. Unter dem Gesichtspunkt der Fertigung sollen die organischen lichtemittierenden Dioden (OLEDs) und die organischen Photodioden (OPDs) einfach konzeptioniert sein. Je nach Bauelementetyp stehen für die Herstellung der organischen Schichten die Vakuumtechnologie oder lösungsmittelbasierte Prozesse zur Verfügung. Eine Besonderheit der Arbeit ist die Integration der OLEDs bzw. der OPDs auf Silizium-Substraten. Zudem wird die Integration von optischen Filtern für die OLEDs sowie die Etablierung einer Dünnschichtverkapselung für die OLEDs und OPDs gezeigt. Im ersten Teil der Arbeit wird anhand von Simulationen der Dünnschichtoptik erarbeitet, welche Möglichkeiten vorhanden sind, die Charakteristik der OLEDEmission bzw. die Absorptionseigenschaften der OPDs zu beeinflussen. Die Besonderheit der OLEDs für die Sensorikanwendungen liegt hierbei in der Licht-Emission mit geringen Halbwertsbreiten. Es wird anhand von Fluoreszenzmarkern (Rhodamin 6G und Nah-IR Alzheimer Farbstoff-4) und einem Chromoprotein (PAS-GAF-64) verdeutlicht, welche Möglichkeiten für die Sensorik durch die Anregung mit der OLED bestehen. Für die OPDs hingegen wird gezeigt, welche Möglichkeiten es für das Rodamin 6G gibt, mit dielektrischen Spiegeln die Absorptionseigenschaften so zu beeinflussen, dass die gewünschten spektralen Bereiche des Lichtes absorbiert bzw. reflektiert werden. Der zweite Teil widmet sich der Entwicklung der OLEDs anhand der Integrationsmöglichkeiten der dielektrischen Filter sowie deren Optimierung. Es wird am Beispiel des Rhodamin 6G gezeigt, dass für die OLED-Emission eine Halbwertsbreite von 18 nm beim Maximum von 530 nm hat. Durch die Verwendung von Entlastungsschichten zwischen OLED und dielektrischem Spiegel können die Kennwerte der OLED positiv beeinflusst werden und weiterhin werden das Temperaturverhalten der OLEDs sowie die Verspannungseigenschaften der dielektrischen Schichten betrachtet. Darüber hinaus steht im dritten Teil die Entwicklung der organischen Photodioden im Fokus. Hierbei wurden OPDs auf Glas- und Siliziumsubstraten gefertigt. Inhalt der Entwicklung auf Glassubstraten ist die Variation der absorbierenden Schicht und deren Einfluss auf die elektro-optischen Eigenschaften. Die Entwicklung der OPDs auf Siliziumsubstraten basiert auf der Integration sowie der Optimierung verschiedener Absorbersysteme, einer alternativen Anode und Kathode sowie der Integration einer Dünnschichtverkapselung. Im Ergebnis wurden OPDs entwickelt, die ohne Dünnschichtverkapselung einen Photonen-zu-Elektron-Umwandlungs-wirkungsgrad (IPCE) von ca. 37 % bei 550 nm haben. Der IPCE konnte zudem durch die Modifikation des Kathodenaufbaus um 4 % gesteigert werden. Die OPD-Bauelemente mit integrierter Dünnschichtverkapselung zeigen einen IPCE von ca. 33 % bei 550 nm. Weiterhin wurde die Methode der orthogonalen Photolithographie zur Strukturierung der OPDs verwendet und es erfolgte der Übertrag der OPD-Technologie auf 8-Zoll-Halbleitersubstrate. In diesem Zusammenhang sind zur Bewertung von Einflüssen, wie Wasser oder Sauerstoff, Untersuchungen zur Lebensdauer der OPDs durchgeführt worden. Die Kenntnis über den Einfluss der orthogonalen Photolithographie auf die Kennwerte der OPDs sowie der Einfluss der Dünnschichtverkapselung auf die Eigenschaften der OPDs und OLEDs sind essentiell für weitere Entwicklungen und zur Fertigung von Sensoranwendungen. / This work focuses on the simulation, development and implementation of organic semiconductor devices for applications in the field of sensor technology. From the viewpoint of manufacturing, organic light emitting diodes (OLEDs) as well as organic photodiodes (OPD) should be designed simply. Depending on the type of device vacuum technology or solvent-based processes are available for producing organic layer. A special feature of OLED- and OPD-devices is the integration on silicon substrates. In addition, the integration of optical filters for OLED-devices and the thin-film encapsulation of OLEDs and OPDs is shown. The first part of the work elaborates on simulations of thin film optics, describing options to control the characteristics of the OLED-emission or the absorption properties of the OPD. A special characteristic of OLEDs is the light emission with a small full with half maximum for sensor applications. By using of fluorescent markers Rhodamine 6G and near-IR dye Alzheimer-4 or the Chromoproteins (PAS-GAF-64) clarifies the possibilities for sensors by excitation with the OLED. In contrast, for the OPD is shown which solutions are available, to influence the absorption properties of Rhodamin 6G with dielectric mirrors so that desired spectral ranges of light are absorbed or reflected. The second part is dedicated to the development of OLEDs based on integration of dielectric filters and their optimization. It is shown by the example of Rhodamine 6G that the OLED emission represents a full with at half maximum of 18 nm at 530 nm. Furthermore, the temperature behavior of the OLEDs and the strain properties of the dielectric layers are considered. Organic photodiodes are in the focus of the third part of the development. These OPDs were made on glass and silicon substrates. The main objective of the development on glass substrates is the variation of the absorption layer and its influence to the electro-optical properties to increase the spectral sensitivity of the OPD. The development of OPD on silicon substrates deals with the integration and optimization of different absorber systems, an alternative anode and cathode as well as the integration of a thin-film encapsulation. As a result, the OPDs without a thin-film encapsulation have an incident photon-to-electron conversion efficiency (IPCE) of about 37 % at 550 nm. The IPCE was increased to 4 % by modifying the cathode structure. The OPD devices with integrated thin-film encapsulation showed an IPCE of about 33 % at 550 nm. Furthermore, the method of orthogonal photolithography was used to pattern the OPD and an upscaling of the OPD technology to 8-inch semiconductor substrates have been realized. In this context studies have been carried out to evaluate the influence of process and encapsulation to the lifetime of OPDs. The knowledge about the influence of the orthogonal photolithography to the characteristics of OPDs and the influence of the thin-film encapsulation on the properties of OPD and OLEDs is essential for further development and for the manufacturing of sensor applications.