In the literature on diffusion of innovations, it is widely known that the characteristics and socio-environmental settings of adopters do evolve in space and time. What about innovations themselves? During the diffusion process, don’t some innovations continuously alter in space and time? If so, how does the dynamic character of an innovation influence the diffusion process? In previous research, it has been often assumed that innovations do not continuously alter or get modified when diffusing from a source to potential adopters. This assumption may mean that the innovation is invariant as it diffuses in time and space—i.e., the innovation does not have a continuously dynamic character. Is it always the case in practice?    A single form of an innovation is not always necessarily compatible with the preferences, limitations, and residential settings of adopters. The innovation might appear in different forms when it diffuses in space and time, i.e., it is “dynamic”. This PhD thesis aims to explore how dynamic innovations diffuse in space and time—a relatively understudied topic in research. In doing so, it distinguishes between the diffusion of dynamic innovations and other kinds of innovations. Anchored on the case of diffusion of residential solar photovoltaic (PV) systems, this thesis is composed of a cover essay and six appended papers. The first two appended papers are systematic literature reviews, aiming at understanding the state of the art of the theoretical and contextual research domains. The third paper is based on a case study in southern Germany and explores the diffusion of a dynamic innovation at adopter level. The fourth paper is empirically focused on a local firm’s business model, which is assumed to be a key to understanding the mechanism behind the diffusion of dynamic innovations. The fifth paper is based on lead market hypothesis and tries to explore the diffusion of innovations at the regional level. The sixth paper studies a semi-hypothetical case and offers an innovative method to forecast the diffusion of innovations in general. The contribution of this PhD thesis lies in three research dimensions: context, method, and theory. Firstly, the thesis takes the existing theories (e.g., diffusion of innovations theory and lead market hypothesis) and methods (e.g., case study) and applies them in different contexts of the diffusion of residential solar PV systems: the individual, sub-national, and national level. Secondly, it proposes a new research method, namely the finite element method for forecasting the diffusion of innovations, based on an existing theory (e.g., wave-like diffusion of innovations in time and space) and context (e.g., solar PV systems). Last but not least, the cover essay of this thesis takes the findings of the appended papers and employs an extension of theory of diffusion of innovations. In doing so, it includes the role of the dynamic characteristic of innovations that do alter in time and space during the diffusion process. Overall, the findings of this thesis indicate that the diffusion of dynamic innovations is different in nature, and continuous efforts of change agents are critical for enhancing the diffusion of such innovations. Change agents are especially important to help potential adopters to find out and develop the form of innovation that best fits their needs, limits, and preferences, which are heterogeneous in space and time. / <p>QC 20151117</p> / European Doctorate in Industrial Management

Novel organic conjugated materials have led to new technologies in the field of flexible electronics, with applications in the area of sensors, field effect transistors, or photovoltaic devices. Several material parameters and properties come into play in these devices, including energy of the frontier molecular orbitals, thin film morphology, and charge transport. These properties can be controlled by the chemistry of organic materials, and through processing conditions. In particular, this dissertation focuses on the isoindigo unit as an electron deficient unit to tune polymer light absorption, charge separation, charge transport in the first part of this dissertation, and morphology control in organic photovoltaic (OPV) devices in a subsequent section. The first part of this dissertation introduces the synthesis and properties of isoindigo-containing polymers as n-type, p-type, or ambipolar semiconductors, and their application in all-polymer or polymer:fullerene blends OPV active layers. It is found that polymers with phenyl linkages along the backbone tend to have broader light absorption than polymers with alternating phenyl-thiophene rings; however, steric hindrance in the former leads to low charge mobilities, and poor device performance. In addition, this section highlights the importance of controlling phase separation in OPV devices by focusing on all-polymer blends, which show large phase separation, and polymer:fullerene blends, where the morphology can be controlled through processing additives generating a two-fold increase in device efficiency. Looking at poly(oligothiophene-isoindigo) polymers as model systems, emphasis is placed on photovoltage losses in these devices due to a decrease in effective energy gap between the polymers and fullerene as the oligothiophene donating strength is increased, as well as explanation of the device parameters through description of morphology as solubility is varied. The second portion of this dissertation focuses on solution properties of polymers and their correlation to thin film morphology. A first study investigates the influence of alkyl side chains on solubility, molecular packing, and phase separation in blends of poly(terthiophene-alt-isoindigo) with fullerenes. Specifically, as side chains are lengthened, solubility is increased, but with limited impact on the blends morphology. On the other hand increased backbone torsion leads to variations in energy levels, polymer packing and large phase separation in blends with fullerenes. These thermodynamic parameters are to put in perspective with the kinetic control of film formation during the coating process. This is discussed in a second study, which looks at the mechanism of thin film formation when processing additives are used. In particular, this study highlights the interactions that provide a driving force for polymer crystallite formation, depending on the mechanism followed when aliphatic and aromatic additives are used. These observations are then used to predict the morphology in spin-coated thin films.

The main goal of this thesis is to investigate and develop the physics of dye-based photovoltaic physics through molecular and photonic routes. Numerous photovoltaics devices have been fabricated through the course of this work to study their characteristics, performance, physical composition and action. The relative youth of the field of dye-based optoelectronics provides extensive scope for new research which provides fascinating opportunities in terms of physical processes.This thesis is divided into two main projects; exploring the adaption of conventional dye-sensitized solar cells via starkly different routes which serendipitously culminated in striking similarities at their conclusion. The first route is through incorporating spectrally complementary dye molecules with the intention of extending the range of light absorption of the final devices. This initial aim was achieved and was then furthered by the realisation of an unexpected and unprecedented energy transfer process occurring, imparting enhanced photocurrent generation in both the near-IR and visibile region. The second route involves investigating the effect on dye-sensitized solar cell physics and performance of the inclusion of metallic nanoparticles with the expectation of inducing plasmonic interactions. Novel systems were designed and implemented, devices were made which display significant performance enhancement, attributed to plasmonic coupling into the dyes and thereby increasing photocapture. A number of other investigations are documented whose current completion does not sufficiently warrant independent chapters but whose scientific interest is evident.

Spectrum-splitting is a multijunction photovoltaic technology that can effectively improve the conversion efficiency and reduce the cost of photovoltaic systems. Microscale PV design integrates a group of microconcentrating photovoltaic (CPV) systems into an array. It retains the benefits of CPV and obtains other benefits such as a compact form, improved heat rejection capacity, and more versatile PV cell interconnect configurations. We describe the design and performance of a two-junction holographic spectrum-splitting micro-CPV system that uses GaAs wide bandgap and silicon narrow bandgap PV cells. The performance of the system is simulated with a nonsequential raytracing model and compared to the performance of the highest efficiency PV cell used in the micro-CPVarray. The results show that the proposed system reaches the conversion efficiency of 31.98% with a quantum concentration ratio of 14.41x on the GaAs cell and 0.75x on the silicon cell when illuminated with the direct AM1.5 spectrum. This system obtains an improvement over the best bandgap PV cell of 20.05%, and has an acceptance angle of +/- 6 deg allowing for tolerant tracking. (C) 2017 Society of Photo-Optical Instrumentation Engineers (SPIE)

A methodology for the simulation of CPV systems is presented in four distinct sections: input, optics, uncertainty and electrical output. In the input section, existing methods of describing the solar irradiation that is incident at the primary optical element of a CPV system are discussed, the inadequacies of the existing methods are explored and conditions of validity for their use drawn. An improved and spectrally extended model for a variable, spatially resolved solar image is arrived at. The model is used to analyse losses at the primary concentration device stage under varying solar profiles and air masses. A contextual analysis of an example Seattle based CPV system operating with constant solar tracking errors of 0.3-0.4° show a corresponding loss in isolation available to the optical system of 5-20%, respectively. In the optics section, an optical ray trace model is developed specifically for this work. The optical ray trace model is capable of the spectrally resolved ray tracing of all insolation input models discussed above. Plano-convex and Fresnel lenses are designed, investigated and compared using each of the insolation models described in the input section. Common CPV component material samples for the plano-convex and Fresnel lenses are analysed for their spectrally resolved optical properties. The computational expense of high resolution spatial and spectral modelling is addressed by means of a spectrally weighted banding method. The optical properties parameter spectral weighting method can be applied to any arbitrary spectral band. The bands used herein correspond to the active ranges of a typical triple-junction solar cell. Each band shows a different spectral dependency. Banded beam irradiation proportions are shown to change by as much as 10% in absolute terms within the air mass range of 1 to 3. Significant variations in spectrally banded illumination profiles are found with the extended light source insolation model. These banded variations are mostly unaccounted for with the use of approximated insolation models, further compounding the argument for extended light source Sun models in CPV system simulations. In the uncertainty section, the limitations of the manufacturing process are explored. Manufacturing tolerance errors from manufacturer datasheets are presented. These production uncertainties are used in the design of an erroneous plano-convex lens which is then analysed with the optical modelled presented in the optics section and compared to the ideal design specification. A 15% variation in maximum intensity value is found alongside a linear shift in the focal crossover point of approximately 0.2mm, although the optical efficiency of the lens remains the same. Framing manufacture errors are investigated for a square Fresnel lens system resulting in a linear shift of the focal centre of approximately 0.85mm. A process for the calculation of wind loading force on a CPV array is also presented. The process uses real 2 second resolution wind data and highlights the chaotic nature of loading force. A maximum force of 1.4kN was found on an example day for a 3m by 3m by 0.1m cuboid (i.e. CPV array); corresponding to a wind speed of approximately 13m/s, which is well within the typical operating range of a CPV tracking system. In the electrical output section, a spatially resolved solar cell model is identified and used for the investigation of solar cell performance under the inhomogeneous cell illumination profiles produced in the uncertainty section. Significant differences in the maximum power point of the cell IVs are found for the ideal and erroneous system illumination profiles. Approximately, a 15% variation is found in the plano-convex lens example, with a relative difference of 4% attributable to illumination profile distortion, and a 6% variation in the module framing component example. These results further highlight the need for the consideration of production uncertainties in CPV system simulation.

The thesis deals with renewable resources, their history, development and support with special emphases on photovoltaics. The thesis turns to particular selected states, where the level and forms of support of renewables are analysed, again with emphases on photovoltaics. The thesis contains a chapter dealing with the support of photovoltaics in the Czech Republic, to which refers the applied part of the thesis -- the build-up of photovoltaic power plant in the Czech Republic in year 2008 in comparison with the one realised in 2010 from the cost-profit point of view.

>Magister Scientiae - MSc / Photovoltaic (PV) devices based on inorganic-organic hybrid active layers have been extensively studied for over a decade now. However, photoactive hybrid layers of material combinations such as rr-P3HT and SiNWs still require further exploration as candidates for solar cell (SC) fabrication, due to favourable optical absorption and charge carrier mobility associated with them respectively. The ultimate goal of the study is to fabricate ITO/PEDOT:PSS/rr-P3HT:SiNWs/Al SCs with different SiNWs content and investigate the different parameters or factors influencing the performance of these cells. The vertically aligned SiNW arrays on a Si wafer were synthesised via metal assisted chemical etching (MACE) and a method of chemically detaching these wires was developed. The average length and the diameter of the SiNWs obtained were 4.5 μm and 0.2 μm, respectively. Different weight ratios of as-synthesised SiNWs were then incorporated within rr-P3HT to form different hybrid solutions, i.e. rr-P3HT: 0.3 wt% SiNWs, rr-P3HT: 0.7 wt% SiNWs and rr-P3HT: 1.3 wt% SiNWs. In addition, a pure rr- P3HT solution was made for reference purposes. SEM characterisation shows that the SiNWs are randomly distributed across the active area, and that the film becomes progressively inhomogeneous upon addition of SiNWs, whereas the TEM characterisation revealed that there is no chemical interaction between the rr-P3HT and SiNWs. The UV-Vis and PL spectra suggest that there are changes in absorption and emission characteristics upon SiNW incorporation into the rr-P3HT matrix, which may have impacted the charge transfer .The electrical properties of the different hybrid films were probed using Hall Effect measurements, which revealed that the conductivity increases with the increase in the concentration of nanowires (NWs). The increase in conductivity upon the addition of SiNWs in the rr-P3HT matrix was related to an increase of the mobility (μ) of charge carriers in the hybrid films.

Diminuer l'épaisseur de la couche d'absorbeur est une solution attractive pour produire des cellules photovoltaïques à coût réduit. Cela permet également de réduire la quantité de matériau actif utilisé ainsi que d'améliorer la collection du courant dans la cellule. Cette thèse s'est focalisée sur la conception de nanostructures pour exalter l'absorption de la lumière dans des couches de semiconducteur d'épaisseur réduite et ainsi proposer des cellules ultraminces efficaces.Dans un premier temps, nous avons proposé une approche originale pour piéger la lumière dans une cellule ultra-fine (≤ 100 nm) en silicium amorphe. Un réseau métallique est placé en face avant de la cellule déposée sur un miroir métallique afin d'obtenir une absorption multi-résonante large bande pour les deux polarisations de la lumière. Nous proposons aussi d'utiliser le réseau métallique comme une électrode transparente alternative afin de réduire les pertes optiques dans le contact avant de la cellule. Une analyse numérique approfondie des mécanismes résonants en jeu a été menée ainsi que la fabrication et la caractérisation optique de démonstrateurs.Dans un deuxième temps, nous avons appliqué ce concept de contact avant multi-résonant à des couches ultra-fines en arsenure de gallium (GaAs). Nous avons montré numériquement et expérimentalement le potentiel d'une nanogrille métallique bi-dimensionnelle pour le confinement efficace de la lumière dans 25 nm de GaAs.Enfin, nous avons étudié la possibilité de réduire l'épaisseur de cellules en silicium cristallin d'un facteur 10 à 100 par rapport à l'état de l'art. Nous avons développé un procédé pour transférer des couches de silicium cristallin de quelques microns d'épaisseur épitaxiées par PECVD sur un substrat hôte bas coût. Nous avons également travaillé à la structuration contrôlée de nanopyramides en vue d'un piégeage optique efficace dans ces couches minces. / Reducing the absorber thickness is an attractive solution to decrease the production cost of solar cells. Furthermore, it allows to reduce the amount of material needed and improve the current collection in the cell. This thesis has been focused on the design of nanostructures to enhance light absorption in very small semiconductor volumes in order to achieve efficient ultra-thin solar cells. First, we have proposed an original light-trapping concept for ultra-thin amorphous silicon (a-Si:H) solar cells. A one-dimensional metallic grating is patterned on the front surface of the cell deposited on a metallic mirror. Broadband multi-resonant absorption has been demonstrated for both light polarizations. The metallic grating is also used as an alternative transparent electrode in order to reduce optical losses in the front contact. A detailed analysis of the multi-resonant absorption mechanism has been carried out through numerical calculations. The fabrication and optical characterization of ultra-thin a-Si:H solar cells with metallic gratings have validated the multi-resonant approach.Second, we have proposed a design with a two-dimensional metallic grid as a resonant front contact for very thin (25 nm) gallium arsenide (GaAs) layers. We have shown through the design and fabrication of a proof-of-concept structure the potential of metallic nanogrids to confine efficiently light absorption with an ultra-thin GaAs layer.Finally, advanced light-trapping structures could also allow a thickness reduction of crystalline silicon wafers of a factor 20 to 100 with respect to state-of-the-art cells. We have developed a process to transfer micron-thick epitaxial crystalline silicon (c-Si) layers onto a low-cost host substrate. Inverted nanopyramids have also been fabricated in crystalline silicon in order to achieve a broadband anti-reflection effect. It opens promising perspectives towards the realization of double-sided nanopatterned ultra-thin c-Si cells.

The high balance-of-system costs of photovoltaic installations indicate that reductions in absorber cost alone are likely insufficient for photovoltaic electricity to reach grid parity unless energy conversion efficiency is also increased. Technologies which both yield high-efficiency cells (>25%) and maintain low costs are needed. GaAs and related III-V semiconductors are used in the highest-efficiency single- and multi-junction photovoltaics, but the technology is too expensive for non-concentrated terrestrial applications. This is due in part to the limited scalability of traditional syntheses, which rely on expensive reactors and employ toxic and pyrophoric gas-phase precursors such as arsine and trimethyl gallium. This work describes GaAs films made by close-spaced vapor transport, a potentially scalable technique which is carried out at atmospheric pressure and requires only bulk GaAs, water vapor, and a temperature gradient to deposit crystalline films with similar electronic properties to GaAs prepared using traditional syntheses. Although close-spaced vapor transport of GaAs was first developed in 1963, there were few examples of GaAs photovoltaic devices made using this method in the literature at the onset of this project. Furthermore, it was unclear whether close-spaced vapor transport could produce GaAs films appropriate for use in photovoltaics. The goal of this project was to create and study GaAs devices made using close-spaced vapor transport and determine whether the technique could be used for production of grid-connected GaAs photovoltaics. In Chapter I the design of the vapor transport reactor, the chemistry of crystal growth, and optoelectronic characterization techniques are discussed. Chapter II focuses on compositional measurements, doping, and improved electronic quality in CSVT GaAs. Chapter III describes several aspects of the interplay between structure and electronic properties of photoelectrochemical devices. Chapter IV addresses heteroepitaxial growth of GaAs on "virtual" Ge-on-Si substrates. This is a topic of importance for the broader III-V community as well as the photovoltaic community, as Si is the substrate of choice in many areas of industry. This dissertation includes unpublished and previously published co-authored material.

While mixed ionic-electronic conductors (MIECs) show promise in a number of different device structures, their successful application has been inhibited by difficulties with characterization. The simultaneous influence of both ionic and electronic systems often foils attempts to quantify material parameters important for rational device design. In many cases, even general models of MIEC function can prove uncertain or controversial. This dissertation addresses the broader issue of ambiguity in MIEC characterization by exploring near-infrared absorbance as a method of gaining further insight into these systems. In combination with a traditional suite of techniques, this method enables determination of parameters not otherwise accessible. The determination of a concentration-dependant carrier mobility in an MIEC material will be demonstrated, and MIEC conduction in the unipolar regime will be broadly described as a system of electrochemically-supported charge injection. This model will be subsequently expanded to describe an unusual and previously unreported phenomenon of rectification when MIECs are interfaced with otherwise appropriate semiconducting contacts. A model labeled as extracting-electrode space-charge limited current will be described and experimentally demonstrated. Finally, the unique photovoltaic properties of an ionic heterojunction system comprising two MIECs will be examined. The results will be used to gain insight into the role of ionic asymmetry in the behavior of MIEC interfaces. This dissertation contains coauthored, previously published, and unpublished work.