Organizational culture, leadership style and effectiveness: A case study of middle eastern construction clients

During the last few decades, organizational effectiveness has received a great deal of attention in many industrial sectors. As a result, a variety of models have been formulated which measure organizational performance. In the construction industry, two factors have subsequently captured the imagination and interest of researchers and practitioners alike: the culture of the organization and the leadership style of project managers. This focus places a requirement upon construction organizations to recognize and understand their organizational culture, and equally, to clearly communicate it to their employees as part of their capitalist drive of constantly improving performance, productivity and profit. Traditional ways of conducting construction business require a sound understanding of the technical and managerial demands of executing projects, which in turn, places an increased emphasis upon the management and leadership competencies of individual project managers. The purpose of the research is to explore the relationship between organizational culture, authentic leadership style and effectiveness within the context of a case study investigation centred on Middle Eastern construction clients and their project managers. The outcomes of the investigation, which include the presentation of an explanatory model, indicate that organizational culture is directly and positively related to performance and effectiveness, while project managers' leadership style has an indirect relationship to effectiveness. A strong organizational culture is therefore deemed critical to organizational performance

Formulierung von Halbleiterlösungen für die organische Photovoltaik

Due to the worldwide increasing energy demand, new approaches for low cost energy production are gaining more and more interest. Organic solar cells are one of the promising technologies in the field of common photovoltaics. Their compatibility to different coating and printing techniques is based on their ability to allow processing from solution. The control of the microstructure and therefore the resulting device performance of the solar cells can be dominantly influenced by the right choice of the processing solvent. In this thesis the formulation of semiconductor solutions for organic photovoltaics was analyzed. This included the analysis of the liquid phase by characterization of the used solutions, the film deposition and drying, as well as the device processing and characterization. In a fundamental section the solubility behavior and solubility parameters were determined for different organic semiconductor materials. Predictions for the design of organic semiconductor inks were based on the Hansen solubility parameters. Good agreement with applied formulations was found for different processing solvents and solvent blends. Further, the method was used to identify non-halogenated green solvents for organic solar cells which was studied for small molecule solar cells and for an upscaling process of polymer:fullerene solar cells. Three different organic semiconductors were chosen to evaluate the applicability of Hansen solubility parameters: a semi-crystalline polymer (P3HT), a dominantly amorphous polymer (PCPDTBT) and a fullerene derivative (PCBM). Compared to P3HT the solubility in most of the analyzed solvents was significantly higher for PCBM and PCPDTBT. Good solubility was found for all materials in halogenated aromatic solvents. Since temperature is a significant factor for solubility, a study on the temperature dependency in different solvents was performed. P3HT showed a strong increase of solubility at higher temperatures, whereas for PCPDTBT and PCBM no pronounced temperature dependency was found. These results were used to determine the Hansen solubility parameters of the materials. The solubility parameters are based on a digital grating of the used solvents. Wrongly classified solvents can cause a reduced accuracy in the determination of the solubility parameters. Instead of using a collection of different solvents to distinguish between good and bad solvents a novel approach was used, based on a binary gradient method. Two component solvent blend systems consisting of solvent and non-solvent were used. By gradually varying the composition of the blend system the accurate control of the transition from a solvent to a non-solvent system was analyzed. The non-solvents were chosen to mainly represent one direction in the Hansen space. Compared to the conventional method this technique offers the advantages of lower time and cost efforts, higher fit accuracy and a more accurate determination of the solubility limits in different directions. Further, predictions of a Gaussian envelope function for the solute concentration as a function of a solubility parameter by Hughes et al. were found to be in good agreement with the solubility results of different solvents and solvent blends. The determination of solubility parameters with the binary solvent gradient method was further used for the small molecule N(Ph-2T-DCN-Et)3 and the fullerene derivative PC70BM which conformed the applicability of this method for small molecules. These fundamental investigations were used to define mutual solubility regimes of the analyzed materials which offers the possibility to design organic semiconductor inks. Different solvents and solvent blends were used for device processing in an applied section of formulation. In most of the analyzed solvent systems halogenated solvents were involved, offering high solubility for the solutes. Health regulations and security control prohibit the use of these solvents in industrial applications. For the identification of ecological friendly replacements without performance losses, Hansen solubility parameters were used. Benzaldehyde was found to be a potential candidate offering high solubility for the small molecule N(Ph-2T-DCN-Et)3 and PC70BM. OPV processing with benzaldehyde showed device effciencies of 3.71 % which were comparable to chlorobenzene processed devices. For P3HT:PCBM based solar cells non-halogenated formulations with o-xylene, o-xylene/ tetrahydronaphthalene and anisole/tetrahydronaphthalene (THN) were used. P3HT in o-xylene tends to gel formation which limits the processablility. The addition of the low volatile THN showed significant improvements compared to o-xylene processed devices. The mean value device effciency increased from 2.42 % for pristine o-xylene processed devices to 2.59 % for processing with an o-xylene/THN (75/25) solvent blend and further to 2.87 % for an anisole/THN (70/30) system. Further, higher fill factors were achieved by incorporating the previously mentioned solvent blends. The found results suggested a classification of additives according to solubility and boiling point. The addition of non-solvents defined the processability. High volatile nonsolvents resulted in functional devices if the overall solubility was high enough for both solutes. Higher additive concentrations reduced the solubility and film deposition failed. Already small amounts of low volatile non-solvents had the same effect. These additives evaporated slower compared to the host solvent, remained in the wet film for a longer period of time and therefore influenced the complete process from wet to dried film formation. For additives which showed a selective solubility for one component and simultaneously a higher boiling point than the host solvent, a device improvement was found. The longer drying phase and the selective solubility were beneficial for the microstructure formation, resulting in devices with full factor mean values of 69 % for the additive bromoanisole. Besides the influence of solvents on the processing and film formation the impact of a ternary semiconductor component on the morphology of a P3HT:PCBM blend was studied. PCPDTBT was used as a second donor material. Based on grazing incidence wide-angle X-ray scattering (GiWAXS), calorimetric and transport analysis of thin films and solar cells, the mechanisms of a ternary blend were studied. The addition of the low band gap polymer did not dramatically influence the crystalline part of P3HT, but the crystallinity of the fullerene was drastically reduced after addition of PCPDTBT. This led to the conclusion that PCPDTBT intermixes with the crystalline phase of PCBM which was also confirmed by processed solar cells in a reduced device efficiency. The found results were used to define general design rules for the formulation of semiconductor solutions and the development of functional inks: (i) Determination of solubility parameters: identification of processing solvents which offer sufficient solubility for all components (ii) Formulation of semiconductor inks: solvent blends and additives (offering a selective solubility) which modify the drying behavior and the phase separation (iii) Defining film formation parameters: modify process parameters with respect to rheological requirements, wettability, film homogeneity, thickness and morphology optimization.Durch den weltweiten Anstieg des Energiebedarfs gewinnen neue Verfahren zur günstigen Energieproduktion zunehmend an Interesse. Organische Solarzellen sind eine vielversprechende Technologie auf dem Gebiet der Photovoltaik. Die Prozessierung aus der Lösung ermöglicht die Verwendung unterschiedlicher Beschichtungs- und Druckprozesse. Dabei ist die Kontrolle der Mikrostrukturbildung, und damit die Solarzelleneffzienz, entscheidend von der richtigen Wahl des verwendeten Lösungsmittels abhängig. In der vorliegenden Arbeit wurde die Formulierung von Halbleiterlösungen für die organische Photovoltaik untersucht. Dies umfasste neben der Charakterisierung der verwendeten Lösungen, die Filmabscheidung und Trocknung, bis hin zur Bauteilherstellung und -charakterisierung. Basierend auf Vorhersagen der Hansen Löslichkeitsparameter wurden geeignete Lösungsmittel und Formulierungen für die Entwicklung organischer Halbleitertinten verwendet. Für eine industrielle Anwendung ist der Einsatz halogenfreier Lösungsmitteln eine der wesentlichen Voraussetzungen. Daher zählte auch die Identifizierung umweltverträglicher Formulierungen zu den Aufgaben dieser Arbeit. Drei organische Halbleiter wurden ausgewählt, um die Anwendbarkeit der Löslichkeitsparameter zu analysieren: ein semi-kristallines Polymer (P3HT), ein amorphes Polymer (PCPDTBT) und ein Fullerenderivat (PCBM). Im Vergleich zu P3HT zeigten die beiden anderen Materialien deutlich höhere Löslichkeiten in den verwendeten Lösungsmitteln. Halogenierte, aromatische Lösungsmittel zeigten hohe Löslichkeiten für alle drei Materialien. Während für P3HT ein deutlicher Anstieg der Löslichkeit bei höheren Temperaturen gefunden wurde, zeigten PCPDTBT und PCBM nur eine schwache Temperturabhängigkeit. Basierend auf diesen Löslichkeitswerten wurden die Hansen Löslichkeitsparameter der Materialien bestimmt. Die Ergebnisse wurden zur Definition gemeinsamer Löslichkeitsbereiche verwendet. Diese bildeten die Grundlage für die Entwicklung organische Halbleitertinten.Die Löslichkeitsparameter basieren auf einer Klassifizierung der verwendeten Lösungsmittel. Eine fehlerhafte Einteilung verursacht eine geringere Genauigkeit in der Bestimmung der Löslichkeitsparameter. Statt der Verwendung reiner Lösungsmittel, wurden in einem neuen Ansatz zur Bestimmung der Löslichkeitsparameter binäre Lösungsmittelgemische verwendet. Diese bestanden aus einen Lösungsmittel und einem Nicht-Lösungsmittel. Durch die gradielle Veränderung der Zusammensetzung des binären Gemisches ließen sich die Grenzen der Löslichkeitsvolumina exakt bestimmen. Die Vorteile diser Methode gegenüber dem konventionellen Ansatz sind der geringere Zeit- und Kostenaufwand, sowie eine höhere Genauigkeit in der Bestimmung der Löslichkeitsgrenzen. Basierend auf Vorhersagen von Hughes et al. wurde gezeigt, dass die Löslichkeit auch als Funktion der einzelnen Löslichkeitsparameter mit einer Gaussfunktion beschrieben werden kann. Die Anwendbarkeit der Gradientenmethode zur Bestimmung der Löslichkeitsparameter wurde außerdem anhand weiterer Materialien, einem kleinen Molekül N(Ph-2T-DCN-Et)3 und dem Fullerenderivat PC70BM, gezeigt. Basierend auf den Vorhersagen der Hansen-Methode wurden für die Prozessierung von organischen Solarzellen Lösungsmittel und Lösungsmittelgemische ausgewählt. In den meisten analysierten Lösungsmittelsystemen wurden halogenierte Lösungsmittel verwendet, die eine hohe Löslichkeit für die gelösten Halbleiter besitzen. Aufgrund von Gesundheitsvorschriften und Sicherheitsanforderungen können diese Lösungsmittel nicht in industriellen Anwendungen genutzt werden. Für die Prozessierung von Solarzellen basierend auf N(Ph-2T-DCN-Et)3 und PC70BM wurde Benzaldehyd als Lösungsmittel ermittelt. Es bietet eine hohe Löslichkeit für beide Komponenten und lieferte Zelleffizienzen von bis zu 3,71 %, und damit vergleichbare Werte zu Solarzellen die mit Chlorbenzol hergestellt wurden. Für Solarzellen basierend auf P3HT:PCBM wurden nicht-halogenierte Formulierungen mit o-Xylol, o-Xylol/Tetrahydronaphthalin und Anisol/Tetrahydronaphthalin (THN) verwendet. P3HT tendiert in Lösungen mit o-Xylol zu Gelformierung, welche die Prozessierbarkeit limitiert. Durch die Zugabe des hochsiedenden THN wurden deutliche Verbesserungen im Vergleich zu Zellen erreicht, die nur mit o-Xylol hergestellt wurden. Die mittlere Zelleffizienz stieg von 2,42 % für Solarzellen, die mit reinem o-Xylol prozessiert wurden, auf 2,59 % für Zellen basierend auf o-Xylol/THN (75/25) und 2,87 % für das System Anisol/THN (70/30). Außerdem wurden höhere Füllfaktoren für beide Lösungsmittelmischungen erreicht. Die gefundenen Ergebnisse konnten in einer Klassiffizierung von Additiven zusammengefasst werden. Die Zugabe von Nicht-Lösungsmitteln definiert die Prozessierbarkeit. Funktionelle Bauteile konnten bei der Zugabe flüchtiger Additive prozessiert werden, solange die Gesamtlöslichkeit für beide Komponenten ausreichend hoch ist. Höhere Anteile an Nicht-Lösungsmitteln reduzierten die Löslichkeit so stark, dass die Prozessierung von Filmen nicht mehr möglich war. Bereits geringe Mengen von hochsiedenden Nicht-Lösungsmitteln hatten den gleichen Effekt. Im Gegensatz zu flüchtigen Nicht-Lösungsmitteln verdampften diese Additve langsamer als das Hauptlösungsmittel und beeinflussten den gesamten Prozess, vom Nassfilm zur Trockenfilmbildung. Für Additive, die sowohl eine selektive Löslichkeit für eine Komponente und eine höhere Siedetemperatur als das Hauptlösungsmittel hatten, wurden Verbesserungen der Zelleffizienz gefunden. Die längere Trocknungszeit und die Selektivität waren vorteilhaft für die Mikrostrukturbildung und führten zu Solarzellen mit Füllfaktoren von 69 % mit dem Additiv Bromanisol. Neben dem Einfluss von Lösungsmitteln auf die Prozessierung und die Filmformierung wurde auch der Einfluss einer dritten Halbleiterkomponente auf die Morphologie einer P3HT:PCBM Mischung untersucht. Dafür wurde PCPDTBT als zweites Donatormaterial verwendet. Weitwinkelröntgenstreuung, sowie kalorimetrie Analysemethoden und Untersuchungen der Transporteigenschaften von dünnen Filmen und Solarzellen wurden für die Untersuchungen der ternären Mischungen verwendet. Die Zugabe des zweiten Polymers beeinflusste kaum die Kristallinität von P3HT. Im Gegensatz dazu wurde der kristalline Teil des PCBM durch die PCPDTBT-Zugabe stark reduziert. Dies führte zu der Schlussfolgerung, dass sich das PCPDTBT mit der kristallinen Phase des PCBM vermischt. Untersuchungen an Solarzellen bestätigten diese Ergebnisse, da höhere Anteile an PCPDTBT in den Mischungen zu einer Verringerung der Zellleistungen führten. Die gefundenen Ergebnisse ermöglichten das Aufstellen von Designregeln zur Formulierung von Halbleiterlösungen und Entwicklung von funktionellen Tinten: (i) Bestimmung der Löslichkeitsparameter: Identifikation prozessierbare Lösungsmittel mit ausreichender Löslichkeit für alle Komponenten (ii) Formulierung von Halbleitertinten: Lösungsmittelmischungen und Additive (mit selektiver Löslichkeit) zur Modifikation des Trocknungsverhaltens, der Phasenseparation und der resultierenden Morphologie (iii) Definition der Filmformierungsparameter: Modifikation der Prozessierungsparameter hinsichtlich rheologischen Anforderungen, Benetzung, Filmhomogenität/-dicke und Morphologieoptimierung

Automatized analysis of IR-images of photovoltaic modules and its use for quality control of solar cells

It is well known that the performance of solar cells may significantly suffer from local electric defects. Accordingly, infrared thermography (i.p. lock-in thermography) has been intensely applied to identify such defects as hot spots. As an imaging method, this is a fast way of module characterization. However, imaging leads to a huge amount of data, which needs to be investigated. An automatized image analysis would be a very beneficial tool but has not been suggested so far for lock-in thermography images. In this manuscript, we describe such an automatized analysis of solar cells. We first established a robust algorithm for segmentation (or recognition) for both, the PV-module and the defects (hot spots). With this information, we then calculated a parameter from the IR-images, which could be well correlated with the maximal power (Pmpp) of the modules. The proposed automatized method serves as a very useful foundation for faster and more thorough analyses of IR-images and stimulates the further development of quality control on solar modules

A universal method to form the equivalent ohmic contact for efficient solution-processed organic tandem solar cells

The highly transparent, conductive and robust intermediate layer (IML) is the primary challenge for constructing efficient organic tandem solar cells. In this work, we demonstrate an easy but generic approach to realize the fully functional, solution-processed IMLs. In detail, solution-processed silver-nanowires are packed at low concentration between hole- and electron-transporting layers to convert an otherwise rectifying interface into an ohmic interface. The IMLs are proven to be of ohmic nature under applied bias, despite the unipolar charge selectivity of the single layers. Ohmic recombination within IMLs is further proven in organic tandem solar cells fabricated by doctor-blading under ambient conditions. The tandem solar cells based on PCDTBT:[70]PCBM as the bottom cell and pDPP5T-2:[60]PCBM as the top cell give a power conversion efficiency of 7.25%, which is among the highest values for solution-processed organic tandem solar cells fabricated by using a roll-to-roll compatible deposition method in air

High shunt resistance in polymer solar cells comprising a MoO3 hole extraction layer processed from nanoparticle suspension

In this report, we present solution processed molybdenum trioxide (MoO3) layers incorporated as hole extraction layer (HEL) in polymer solar cells (PSCs) and demonstrate the replacement of the commonly employed poly(3,4-ethylene dioxythiophene):(polystyrene sulfonic acid) (PEDOT:PSS). MoO3 is known to have excellent electronic properties and to yield more stable devices compared to PEDOT:PSS. We demonstrate fully functional solar cells with up to 65 nm thick MoO3 HEL deposited from a nanoparticle suspension at low temperatures. The PSCs with an active layer comprising a blend of poly(3-hexylthiophene) and [6,6]-phenyl-C61 butyric acid methyl ester and a MoO3 HEL show comparable performance to reference devices with a PEDOT:PSS HEL. The best cells with MoO3 reach a fill factor of 66.7% and power conversion efficiency of 2.92%. Moreover, MoO3 containing solar cells exhibit an excellent shunt behavior with a parallel resistance of above 100 kΩ cm2

Flexible organic tandem solar modules: a story of up-scaling

The competition in the field of solar energy between Organic Photovoltaics (OPVs) and several Inorganic Photovoltaic technologies is continuously increasing to reach the ultimate purpose of energy supply from inexpensive and easily manufactured solar cell units. Solution-processed printing techniques on flexible substrates attach a tremendous opportunity to the OPVs for the accomplishment of low-cost and large area applications. Furthermore, tandem architectures came to boost up even more OPVs by increasing the photon-harvesting properties of the device. In this work, we demonstrate the road of realizing flexible organic tandem solar modules constructed by a fully roll-to-roll compatible processing. The modules exhibit an efficiency of 5.4% with geometrical fill factors beyond 80% and minimized interconnection-resistance losses. The processing involves low temperature (<70 degrees C), coating methods compatible with slot die coating and high speed and precision laser patterning

Tailoring green formulation : printing and upscaling of inverted organic solar cells

By tailoring the solvents of active organic solar cell layers regarding their solubility (Hansen parameters), non-halogenated solvents and solvent mixtures can be used to print the active layers of organic solar cells. Similar efficiencies to other typical laboratory methods as spin-coating can be reached. Furthermore, using sheet-to-sheet printing or coating techniques compatible to mass-manufacturing and structuring by laser ablation, we can upscale to 10x20 cm(2) and manufacture modules on plastic substrates. This is a breakthrough for organic solar cells and the next important step on the way to utilize organic solar cells for industrial manufacturing

Large area slot-die coated organic solar cells on flexible substrates with non-halogenated solution formulations

The transfer from lab scale to industrial application is one of the challenges for organic photovoltaics. For this, non halogenated formulations are a decisive need for the upscaling process, as are roll-to-toll (R2R) compatible methods. Devices processed with o-xylene using slot-die coating as a sheet-to-sheet technique show a reduced efficiency on a larger scale compared to lab scale solar cells. By using a mixture of high and low volatile solvents which selectively dissolve one component, the film homogeneity and the efficiency is dramatically improved. The slot-die coated active layers for solar cells processed from non-halogenated solvents show device efficiencies above 3% on flexible substrates. (C) 2014 Elsevier B.V. All rights reserved