The manufacture of photovoltaic (PV) system components has a role to play in the industrialisation and poverty reduction strategies of developing countries. It has also been suggested that small scale local manufacture of balance of systems components has the potential to improve the maintenance, installation and use of the technology. However, PV is a complex technology and most developing countries have not been able to build the capabilities required to manufacture PV system components of an appropriate quality and price, either in the modern or small scale sectors. The factors that determine the success of PV manufacturers in developing countries are therefore of interest. Previous studies on learning in the PV industry have been focused on industry-wide concerns and have not explicitly addressed enterprise-level capability building or challenges specific to developing countries. In particular, there has been very little published about small scale PV manufacture. This thesis therefore aims to improve understanding of the factors that influence capability building, with a view to assisting decision making in relation to PV manufacture in developing countries. The aims of the study have been fulfilled by the development and assessment of a software simulation training tool for PV cell production line engineers, the development of an analysis framework, and application of it to several case study PV enterprises. Through the application of the framework to the case studies, it has been possible to assess the role of software simulations, the suitability of countries with different types of infrastructure for hosting PV manufacturing and the institutional arrangements or interventions that could be used to promote capability building for PV manufacturers in developing countries. While further case studies are required to make more than tentative conclusions, the framework developed and tested in this thesis may now be used as a tool to systematically and rapidly analyse the appropriateness of different types of PV manufacture in particular countries, to identify the weaknesses in their PV technological systems and therefore to suggest where resources should be invested and where appropriate institutional changes could be made. The simulation software has been demonstrated to be an effective capability building tool, thus providing one of the key elements required for successful manufacturing.

The manufacture of photovoltaic (PV) system components has a role to play in the industrialisation and poverty reduction strategies of developing countries. It has also been suggested that small scale local manufacture of balance of systems components has the potential to improve the maintenance, installation and use of the technology. However, PV is a complex technology and most developing countries have not been able to build the capabilities required to manufacture PV system components of an appropriate quality and price, either in the modern or small scale sectors. The factors that determine the success of PV manufacturers in developing countries are therefore of interest. Previous studies on learning in the PV industry have been focused on industry-wide concerns and have not explicitly addressed enterprise-level capability building or challenges specific to developing countries. In particular, there has been very little published about small scale PV manufacture. This thesis therefore aims to improve understanding of the factors that influence capability building, with a view to assisting decision making in relation to PV manufacture in developing countries. The aims of the study have been fulfilled by the development and assessment of a software simulation training tool for PV cell production line engineers, the development of an analysis framework, and application of it to several case study PV enterprises. Through the application of the framework to the case studies, it has been possible to assess the role of software simulations, the suitability of countries with different types of infrastructure for hosting PV manufacturing and the institutional arrangements or interventions that could be used to promote capability building for PV manufacturers in developing countries. While further case studies are required to make more than tentative conclusions, the framework developed and tested in this thesis may now be used as a tool to systematically and rapidly analyse the appropriateness of different types of PV manufacture in particular countries, to identify the weaknesses in their PV technological systems and therefore to suggest where resources should be invested and where appropriate institutional changes could be made. The simulation software has been demonstrated to be an effective capability building tool, thus providing one of the key elements required for successful manufacturing.

Σκοπός της παρούσας διπλωματικής εργασίας είναι μέσα από την πειραματική διαδικασία και την επεξεργασία των αποτελεσμάτων να μελετηθούν τα φωτοβολταϊκά πλαίσια τεχνολογίας λεπτών φιλμ (Thin Films Photovoltaics-TFPV) που υπάρχουν διαθέσιμα στο εργαστήριο Ασύρματης Τηλεπικοινωνίας του Πανεπιστημίου Πατρών στο Τμήμα Ηλεκτρολόγων Μηχανικών και Τεχνολογίας Υπολογιστών και να εξαχθούν συμπεράσματα που θα οδηγήσουν στην κατανόηση της λειτουργίας τους. Η ανάλυσή τους θα διευκρινίσει την λειτουργία τους και σε πραγματικές εφαρμογές. Επιπλέον θα γίνει προσπάθεια πειραματικής εξομοίωσης συνθηκών δοκιμής στους 25οC υπό ηλιακή ακτινοβολία 1000 W/m2 τονίζοντας ότι οι κατασκευαστικές πληροφορίες σε αυτές τις συνθήκες είναι ενδεικτικές και δεν εκφράζουν την συμπεριφορά των πλαισίων σε πραγματικές συνθήκες λειτουργίας. Επίσης θα παρουσιαστεί η επίδραση της τοπικής σκίασης και της αύξησης της προσπίπτουσας ακτινοβολίας σε μέρος ή και σε ολόκληρο το πλαίσιο που προκαλείται από ανάκλαση με τη βοήθεια κατόπτρου. Ειδικότερα παρουσιάζεται η κατάσταση της ενεργειακής πραγματικότητας σήμερα, οι προβληματισμοί για το περιβάλλον, η στροφή στις Ανανεώσιμες Πηγές Ενέργειας και η σημαντικότητα της ενσωμάτωσης φωτοβολταϊκών στα κτήρια. Επίσης παρουσιάζεται η θεωρία της ηλιακής ενέργειας και των φωτοβολταϊκών συστημάτων με τα πλεονεκτήματα και μειονεκτήματά τους. Στην συνέχεια γίνεται αναφορά στη συνδεσιμότητα των φωτοβολταϊκών με την ΔΕΗ και στις ενεργειακές ανάγκες που μπορούν να καλύψουν σε μια κτηριακή εγκατάσταση. Αναλύονται τεχνικές λεπτομέρειες και χαρακτηριστικά μεγέθη των φωτοβολταϊκών στοιχείων καθώς και η εξέλιξη της φωτοβολταϊκής τεχνολογίας ξεκινώντας από το πυρίτιο και καταλήγοντας στα Λεπτά Φιλμ και σε ακόμα νεότερες τεχνολογίες. Στη συνέχεια γίνεται ανάλυση της τεχνολογίας των λεπτών φιλμ προσανατολισμένη στην ενσωμάτωση τους σαν δομικά υλικά σε κατασκευές (BIPV-Building Integrated Photovoltaics).Στην πειραματική διαδικασία επεξηγείται η λογική που ακολουθήθηκε, η πειραματική διάταξη και τα όργανα που χρησιμοποιήθηκαν. Μελετώνται επίσης οι φωτοβολταϊκές παράμετροι και αναλύονται τα πειραματικά δεδομένα. Η ανάλυση γίνεται ως προς την ακτινοβολία, την θερμοκρασία και την εποχή του έτους. Τέλος, τα αποτελέσματα της ανάλυσης, (μέσο ένος προγράμματος στην γλώσσα προγραμματισμού C++), δημιουργούν μια βάση δεδομένων προσπελάσιμη από τον χρήστη για την πρόβλεψη και εξομοίωση των πειραματικών αποτελεσμάτων σε οποιοδήποτε συνδυασμό θερμοκρασίας και ακτινοβολίας. / The purpose of this diploma thesis is to study thin film photovoltaic panels that are available in the wireless communication laboratory in the University of Patras in the department of Electrical and Computer Engineering. Through the experimental process and processing its results our goal was to extract the conclusions that would lead us to a better understanding of their function. Their analysis will determine their usability in real outdoor PV systems. A simulation of the standard test conditions that are set in 250C temperature and 1000 W/m2 radiation is made, pointing out that this information is unable to indicate the actual function of the panels in outdoor conditions. The effects of partial shadowing and increased radiation with mirror system are also presented. More specifically, the energy reality, thoughts about the environment, the global turn towards the renewable energy sources and the significance of photovoltaic integration in buildings (BIPV- Building Integrated Photovoltaics) are mentioned. The theory of solar energy and photovoltaic technology including its advantages and disadvantages is analyzed. Grid-connected PV systems, their contribution in energy production in buildings and the potential of wide application of BIPV is presented. The advantages of thin film as BIPV materials are also mentioned. The experimental parameters, the logics followed in the set up process and the instruments used are part of the complete analysis of thin film parameters in relation to radiation, temperature and time of the year that the measurements occurred. Finally with a C++, a simulation program was created to predict the behavior of the thin film panels in outdoor conditions.

Η ηλιακή ενέργεια μπορεί να συμβάλει στην αντιμετώπιση του ενεργειακού προβλήματος, με την ευρεία αξιοποίηση των φωτοβολταϊκών και των θερμικών ηλιακών συλλεκτών. Τα φωτοβολταϊκά συστήματα που συνδυάζονται με θερμικές μονάδες κυκλοφορίας νερού ή αέρα, για την απολαβή της θερμότητας από αυτά και την ικανοποιητική διατήρηση της απόδοσής των, αποτελούν τα υβριδικά φωτοβολταϊκά/θερμικά συστήματα (φβ/θ). Τα συστήματα αυτά παράγουν ηλεκτρική και θερμική ενέργεια ταυτόχρονα, αυξάνοντας την ολική παραγόμενη ενέργεια. Με τη χρήση ορισμένων διατάξεων βελτίωσης της απολαβής της θερμότητας από τα φωτοβολταϊκά και της αύξησης της αποδιδόμενης ενέργειας των φωτοβολταϊκών και των θερμικών ηλιακών συλλεκτών, είναι δυνατή η βελτίωση της αποδοτικότητας των συσκευών αυτών, για μια πιο αποτελεσματική εφαρμογή τους στα κτήρια. Η διπλωματική εργασία που ακολουθεί περιλαμβάνει τη μελέτη φωτοβολταϊκών, υβριδικών φωτοβολταϊκών και θερμικών ηλιακών συσκευών. Πραγματοποιήθηκε μελέτη υβριδικού φωτοβολταϊκού/θερμικού συστήματος αέρα με διάφορες βελτιώσεις της αποδοτικής λειτουργίας του και με την προσθήκη μεταλλικών φύλλων ή σωλήνων ροής νερού στον αεραγωγό. Ακόμη, μελετήθηκε επίπεδος ηλιακός θερμικός συλλέκτης με προσθήκη διάφορων τύπων ανακλαστήρων (λευκή επιφάνεια, γαλβανιζέ μεταλλικό φύλλο και καθρέφτης). Πραγματοποιήθηκαν επίσης πειράματα με σωλήνα κενού, ο οποίος συνδυάστηκε με ανακλαστήρες για την αύξηση της προσλαμβανόμενης ηλιακής ακτινοβολίας και βελτίωση της αποδιδόμενης θερμότητας. Με βάση τα αποτελέσματα παρατίθενται συμπεράσματα και προτάσεις σχετικά με τις σύνθετες διατάξεις που αναφέρθηκαν. / Solar energy systems can contribute to energy demand by the proper synergy of photovoltaics and solar thermal collectors. The PV modules which are combined with thermal units and circulating water or air to extract the heat from them, constitute the hybrid photovoltaic/thermal systems (PV/T). These systems provide electrical and thermal energy simultaneously, increasing the total energy output. Adapting some effective heat extraction elements to PV modules and applying devices to have solar radiation increase by the absorbing surfaces of PV and of thermal collectors, an improvement of operation and performance of these systems can be achieved regarding their application to buildings. The thesis that follows includes a study of photovoltaics, hybrid photovoltaic/ thermal systems and solar thermal collectors. More specifically, a study of an air heating hybrid photovoltaic/thermal system was performed, improving suitably the heat extraction by inserting corrugated metallic sheets or water pipes, inside the air channel that is attached to rear surface of PV modules. In addition, a solar thermal collector was studied, by applying several types of reflectors (white plate reflector, galvanized iron plate reflector and specular reflector). Furthermore, a vacuum tube type collector was tested, combined also with reflectors to increase input solar radiation and increase thermal performance. Finally, conclusions and suggestions for a further study, on the above mentioned solar energy systems is included, based on the reported experimental results.

Les perovskites hybrides organique-halogénure de plomb représentent une classe de matériaux émergents, proposés en tant qu'absorbeur de lumière dans le cadre d'une nouvelle génération de cellules solaires. La formule chimique de ces composés est APbX3, où A est un cation organique, X représente un anion halogénure (normalement Cl-, Br-, ou l-, ou alors un alliage composé par ces éléments). Les perovskite hybrides combinent d'excellentes propriétés d'absorption avec une grande longueur de diffusion et de longues durées de vie des porteurs de charge, ce qui permet d'atteindre des efficacités de conversion de photons de 22%. Un autre avantage réside dans leur bas coût de fabrication. Par conséquent, avec le développement de cette classe de matériaux, le photovoltaïque basé sur les perovskites sera potentiellement capable de fortement améliorer les performances de la technologie photovoltaïque actuelle, basée sur le silicium. Dans cette thèse, nous utilisons des méthodes optiques afin d'étudier les propriétés électroniques de base et la morphologie de couches minces de plusieurs représentants des perovskites. Nous étudions notamment des composés ayant le methylammonium et le formamidinium en tant que cations organiques ainsi que les iodures et les bromures à large bande interdite et nous montrons de quelle manière la composition chimique influence les paramètres étudiés. Par magnéto-transmission, nous déterminons directement l'énergie de liaison de l'exciton et sa masse réduite. Nous avons trouvé que les énergies de liaison à T = 2K sont comprises de 14 à 25 meV, plus petites ou comparables à l'énergie thermique moyenne à la température ambiante (25meV). De plus, ces valeurs diminuent à T=160K jusqu'à 10-24meV. Suite à ces résultats, nous concluons que les porteurs photocréés dans les perovksites peuvent être considérés ionisés thermiquement à la température ambiante. Les valeurs de masse effective sont comprises entre 0.09-0.13 fois la masse de l'électron libre. Nous montrons également que l'énergie de liaison de l'exciton ainsi que la masse effective dépendent linéairement de la valeur de la bande interdite. Nos résultats permettent donc d'estimer la valeur des paramètres de ces nouveaux composés perovksites. Nous avons étudié la morphologie de couches minces de perovskite par photoluminescence résolue spatialement avec une résolution micrométrique. Cette technique nous a permis d'observer des grains cristallins uniques. Nous démontrons que la transition de la phase tétragonale à orthorhombique à basse température est incomplète dans tous les matériaux étudiés, comme montré par les résidus de phase tétragonale trouvés à T =4K. En étudiant structurellement certaines régions endommagées et photo-recuites, nous montrons que la présence de la phase tétragonale à basse température augmente, causée par une déplétion de l'halogène. / The hybrid organo-lead halide perovskites are an emerging class of materials, proposed for use as light absorbers in a new generation of photovoltaic solar cells. The chemical formula for these materials is APbX3, where A is an organic cation and X represents halide anions (most commonly Br-, Cl- or I-, or alloyed combination of these). The hybrid perovskies combine excellent absorption properties with large diffusion lengths and long lifetime of the carriers, resulting in photon conversion efficiencies as high as 22%. Another advantage is the inexpensiveness of the fabrication process. Therefore, with the rapid development of this class of materials, the perovskite photovoltaics has perspectives to outperform the well-established silicon technology. Here, we use optical methods to investigate the basic electronic properties and morphology in the thin films of several representatives of the hybrid perovskites. We study the compounds based on Methylammonium and Formamidinium organic cations; the iodides and wide band-gap bromides, showing how the chemical composition influences the investigated parameters. Using magneto-transmission, we directly determine the values of exciton binding energy and reduced mass. We find that the exciton binding energies at T = 2 K, varying from 14 to 25 meV, are smaller or comparable to the average thermal energy at room temperature (˜25 meV). Moreover, these values fall further at T = 160 K, to 10-24 meV. Based on that we conclude that the carriers photocreated in a perovskite material can be considered to be thermally ionized at room temperature. The measured reduced masses are in the range of 0.09-0.13 of the electron rest mass. We also show that both exciton binding energy and reduced mass depend linearly on the band gap energy. Therefore, the values of these parameters can be easily estimated for the synthesis of new perovskite compounds. With the spatially resolved photoluminescence, we probe the morphology of perovskite films with micrometer resolution, which enables us to observe single crystalline grains. The resulting maps show that all investigated thin films are composed from the dark and bright crystalline grains. We demonstrate that the low temperature phase transition from tetragonal to orthorhombic phase is incomplete in all studied materials, as the remains of the tetragonal phase are found even at T = 4 K. By investigating structurally damaged and photo annealed regions, where the occurrence of the tetragonal phase at low temperatures is enhanced, we attribute its presence to the depleted halide content.

Magister Scientiae - MSc (Chemistry) / This work involves the synthesis of copper telluride-polypropylenimine tetra(5-(2-thienyl) salicylaldimine) (CuTe@PPI) and copper antimonide-polypropylenimine tetra(5-(2-thienyl) salicylaldimine) (CuSb@PPI) core-shell nanoparticles (NPs), using two-pots and one-pot synthesis methods, respectively. Their morphology was studied by X-ray diffraction spectroscopy (XRD), high resolution transmission electron microscopy (HRTEM) and high resolution scanning electron microscopy (HRSEM); while their structures were characterized by Fourier transform infrared spectroscopy (FTIR) and elemental analysis. Photophysical properties of the core-shell NPs were determined from ultraviolet-visible absorption spectroscopy (UV-Vis) and photoluminescence spectroscopy (PL). For core-shell NPs produced via two-pots method only CuTe@PPI exhibited ? ? ?* and n ? ?* which indicate that CuSb@PPI produced via two-pots method was unsuccessfully synthesized. The ? ? ?* and n ? ?* transitions indicate the presence of polypropylenimine tetra(5-(2-thienyl) salicylaldimine) (PPI) on the surface of CuTe NPs and CuSb NPs. FTIR confirmed coordination of PPI on the surface of CuTe NPs and CuSb NPs by showing a shift in wavenumber of C=N group bands from PPI. HR-TEM showed that the CuTe@PPI synthesized via one-pot method have a wide particles sizes distribution with an average particles size of 13.60 nm while for CuTe@PPI synthesized via two-pots it was impossible to determine the particles size due to aggregation. CuSb@PPI synthesized via twopots method and one-pot method has a wide particles sizes distribution with an average size of 7.98 nm and 11.61 nm respectively. The average particles sizes determined by HR-SEM were found to be 35.24 nm (CuTe@PPI two-pots method), 33.90 nm (CuTe@PPI one-pot method), 18.30 nm (CuSb@PPI two-pots method), and 16.18 nm (CuSb@PPI one pot method). / 2021-08-31

Au cours des dernières années, les perovskites hybrides organiques-inorganiques ont été employées en tant qu’absorbeurs de lumière, en raison de leurres excellentes propriétés optiques et électroniques. L’efficacité de conversion des photons des cellules solaires hybrides à base de perovskites a augmenté de 6,9% à 23,6% au cours des dernières années. Le but de cette thèse est d’étudier les propriétés optiques et électroniques des perovskites à l’aide de spectroscopie magnéto-optique. Nous avons étudié la relation entre les propriétés excitoniques et la microstructure des perovskites hybrides. Nous avons effectué des mesures de magnéto-transmission sur des couches minces polycristallines de MAPbI3 et des mesures de magnéto-réflectivité sur un monocristal de MAPbI3. Nous avons monté que, à basse température, l’énergie de liaison de l’exciton et sa masse réduite sont les mêmes pour tous les échantillons de MAPbI3 indépendamment de la taille des cristaux.Ensuite, nous avons étudié les propriétés électroniques des perovskites entièrement inorganiques, à savoir les composés CsPbX3 (X = I ou Br ou un mélange de ceux-ci). En effectuant des mesures de magnéto-transmission sur CsPbX3, nous avons déterminé les énergies de liaison de l’exciton et la masse réduite avec une grande précision. Une comparaison des valeurs de constante diélectrique des perovskites inorganiques et inorganiques montre que, à basse température lorsque les mouvements des cations organiques sont interdits, la contribution dominante à l’écrantage diélectrique estliée au mouvement relatif dans la cage à base de halogénures de plomb. / Optical and electronic properties. The photon conversion efficiency of hybrid perovskite based solar cells has increased from 6.9% to 23.6% within the last few years. The aim of this thesis is to investigate the optical and electronic properties of perovskite materials using magneto-optical techniques. We have investigated the relationship between the excitonic properties and the microstructure of hybrid perovskites. We have performed magneto-transmission measurement on MAPbI3 polycrystalline thin films and magneto-reflectivity measurement on a MAPbI3 single crystal. We find that, at low temperature, the exciton binding energy and reduced mass are the same for all MAPbI3 samples with a variety of crystal grain sizes.We have also investigated the electronic properties of the fully inorganic perovskites, namely CsPbX3 compounds (X = I or Br or a mixture of those). By performing the magneto-transmission measurement on CsPbX3, we have determined the exciton binding energies and reduced mass with high accuracy. A comparison of the values of dielectric constant for the fully inorganic and the hybrid organic-inorganic perovskites indicates that, at low temperature when the organic cations are frozen, the dominant contribution to the dielectric screening is related to the relative motion within the lead halide cage.

Morphological architecturing is one of the smart and efficient ways to maximize the number of excitons harvested from the known photoactive materials and existing fabrication technologies. Surfaces and interfaces play a vital role in absorbing light and therefore when patterned regularly, aid in the improvement of light absorption. This thesis deals with the study of light management by morphologically architecturing the organic electroactive materials. Here, morphological architecturing is carried out using electrospinning technique by optimizing various parameters. In the first part, organic photovoltaic system is tailored by morphologically modifying the conjugated polymer active layer and analyzing the enhancement in light collection and hence performance of photovoltaic devices. In the second part, the prospects of using free standing buffer layer instead of thin film buffer layer in a solar cell is evaluated. Furthermore, the study on morphological engineering of conjugated small molecule is carried out, by varying the solvents and derivatives, in order to control morphologies by understanding the underlying mechanism. Overall this thesis attempts to understand the fundamentals in morphological architecturing, by physical architecturing of the small molecules in a device for light management applications as well as demonstrating improvement in light absorption in existing organic photovoltaic systems. In the introduction chapter, a brief description of organic photovoltaics is given followed by highlighting the importance of processing methods in light management and in organic photovoltaics. The significance of structured architecture in improving the device characteristics is presented. The issues and challenges in existing architecturing techniques available in literature are discussed. Electrospinning as a tool for morphological modification for organic photovoltaics is demonstrated. This is followed by an outline of the thesis. In Chapter 2, brief description of procedures carried out for fabrication, characterization and optimization of electrospinning process parameters are discussed. The description of fabrication procedures including electrospinning, spincoating and thermal evaporation are given. Characterization techniques used in this thesis for surface and feature analysis, structural, compositional, optical and opto-electrical analyses are described. Optimization of electrospinning process parameters in obtaining various morphologies are evaluated. In Chapter 3, enhancement of device characteristics of poly (3-hexylthiophene): phenyl C61-butyric acid methyl ester (P3HT: PCBM) by changing active layer film morphology into network structure is elucidated. Network structure is provided by electrospraying assisted hierarchical assembly of short fibrils. Effect of electrospraying parameters such as solvent, polymer blend concentration, applied voltage, tip to collector distance, flow rate and deposition time are analyzed. Solvent and applied voltage are observed to be the major parameters governing the formation of network structure. The optimized conditions are used to investigate the optical and structural properties. Percent reflectance studies showed improvement in light absorption due to increase in surface area. Structural characterization studies indicate an increase in orientation of crystallites and crystallinity as compared to spincoated samples. The optimized conditions along with additional spincoated layer of P3HT:PCBM are used to fabricate bulk heterojunction device. Device characteristics exhibited an increase in short circuit current and thus increase in efficiency from 2.18% to 3.66%. There is a enhancement of 37.5% going from maximum external quantum efficiency of 40%-55% for electrosprayed and spincoated devices. It is anticipated that network morphology could be the next possible structure to be explored in organic photovoltaic materials. In Chapter 4, photonic structure is analyzed and compared. A photonics device requires uniform periodic structural arrangement. Various techniques are used to fabricate these types of structures, employing several steps of fabrication. This work proposes single step hierarchical array of equal submicron size porous structure fabricated by tuning electrospinning processing parameters. The dictating process parameters on evolving structure are high voltage, tip to collector distance and solvent. Morphological and optical investigations suggest that uniform periodic topography helps in light scattering leading to multi reflection and thus enhancement in light absorption. This structure is evaluated as active layer in organic photovoltaic devices using poly (3 hexyl thiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) blend and its device characteristics are analyzed. Consistent and reliable device characteristics obtained through photonic structure is demonstrated. Finally, comparison is drawn to network structure to assess the advantages and limitations of both morphologies as active layer in organic photovoltaics. In Chapter 5, instead of architecturing active layer the next polymer film layer in the organic solar cells, that is the hole transport layer is transformed into free standing nanofiber mats. Morphological, structural and surface wetting properties are assessed for these nanofiber mats followed by fabrication of inverted organic solar cell. The free standing nanofibers mats are obtained by electrospinning the blend of Poly(3,4-ethylenedioxythiophene) Polystyrene sulfonate (PEDOT:PSS) a conducting water soluble polymer with other water soluble polymers such as poly vinyl alcohol (PVA) and poly ethylene oxide (PEO). The study is further extended by employing two batches of PEDOT:PSS of varying conductivity that are analyzed side by side for six ternary and two binary blends each. Electrospinning parameters such as applied voltage and flow rate are optimized and fibers of diameter 150-200 nm are obtained. Maximum content of PEDOT:PSS with which free standing fiber mats could be achieved are 98 and 99%. Subsequent increase in PEDOT:PSS results in formation of beads. Surface wetting behavior showed that hydrophillicity increases with increase in PEDOT:PSS content. Devices are fabricated and the variation in characteristics and charge collection with respect to addition of PEO and PVA are discussed. In Chapter 6, a conjugated small molecule is taken as case study unlike the use of the conjugated polymer studies in previous chapters. A mechanism is proposed for tuning the sphere-spike morphology and also to control the crystallite size through solvent management using a conjugated small molecule. Electrospraying of an organic molecule is carried out using various solvents, obtaining fibril structures along with a range of distinct morphologies. Solvent characteristics play a major role in achieving the morphology of the organic material. A thiophene derivative (7, 9-di (thiophen-2-yl)-8H-cyclopenta [a]acenaphthylen-8-one) (DTCPA) of donor-acceptor-donor (DAD) architecture is used to study this solvent effect. Seven solvents with decreasing vapor pressure are selected for experiments. Electrospraying is conducted at a solution concentration of 1.5 wt % and a constant applied voltage of 15 kV. Gradual transformation in morphology of the electrospun product from spikes-sphere to only spikes is observed. A mechanism describing this transformation is proposed based on the electron micrograph analysis and XRD analysis. These data indicate that the morphological change is due to the synergistic effect of both vapor pressure and dielectric constant of the solvents. Through a reasonable control over the crystallites size and morphology along with supporting transformation mechanism theory, the work in this chapter elucidates electrospraying as a prospective method for designing the architectures in organic electronics. In Chapter 7, light management studies are carried out by morphologically architecturing the carbazole derivatives through electrospraying. The effect of derivatives on morphology is analyzed. The two carbazole derivatives; carbazole-benzothiadiazole (Cz-Bz) resulted in 2D structures and carbazole-benzothiadiazole-bithiophene (Cz-Bz-Bt) resulted in 3D structures after electrospraying. These structures are further analyzed to study the effect of vapor pressure of solvents and solution concentration. Structural characteristics indicate that electrospraying imparts change in molecular structure orientation. Optical studies showed 19 – 31% enhancement in light absorption. Further, three types of organic photovoltaic devices are fabricated and the opto-electrical properties are evaluated. Also, the effect of substrate on morphological formation is assessed. In Chapter 8, the major contributions and conclusions drawn from the morphological architecturing of both conjugated polymers and small molecules are summarized, along with few recommendations for future research.

In recent years, organic photovoltaics (OPVs) have attracted considerable attention as a potential source of renewable energy over traditional materials due to their light weight, low production cost, mechanically stability and compatibility with flexible substrates in roll to roll processing for high volume production. In the OPVs interface plays an important role in determining the performance of the device. Interface signifies formation of efficient contact with electrode, film, and transport of free charge carrier, which results in better performance in the device. Interface engineering also helps in improving mechanical robustness of the device. Hence, understanding of interface, modification and its evaluation is important in fabrication of efficient device. In this thesis interface is modified such that the performance of the device can be improved (chapter 3 and chapter 4). In Chapter 5 and chapter 6 interface is modified such that device can be fabricated on uncommon substrate. Fabrication of device on uncommon substrates (fiber reinforced plastic and flexible glass substrate), has unique challenges. In chapter 5 and chapter 6, we look at how interface is modified to overcome the challenges associated and also understand the role of interface in improving the performance of device on such substrates is discussed. In Chapter 1 we discuss about working of organic solar cells and the challenges associated in device fabrication. Understanding of interface to overcome challenges associated is explained. It also covers brief introduction to the succeeding chapters discussed in the thesis and its recent developments. To understand the properties of interface and to analyze device performance various characterization techniques have been used are discussed in chapter 2. This chapter also covers the materials and general device fabrication techniques used in this thesis. In chapter 3, a narrow bandgap (NBG) polymer used as a near IR sensitizer in P3HT: PCBM blend. Since, P3HT with a band gap of ~1.9 eV, the commonly used p-type material absorbs approximately ~25 % of incident light. Hence, MP2 (NBG polymer) is used along with P3HT: PCBM in active layer to form a ternary blend, which helps in increased absorption. Basic properties of MP2 are evaluated using UV-visible spectroscopy, differential scanning calaorimetry(DSC), thermogravimetric analyser (TGA), gel permeation chromatography (GPC) and photoluminescence (PL) techniques. To evaluate enhanced absorption of ternary UV-visible spectroscopy is carried out. Charge transfer from one moiety to other in ternary blend is evaluated using PL and Ttime resolved microwave conductivity (TRMC). Morphology of the ternary is assessed using atomic force microscope (AFM) and structural characterization is carried out by X-ray diffraction (XRD). Performance of the device is evaluated by current-voltage (J-V) characterizations. Further improved performance is supported by external quantum efficiency (EQE). Charge extraction with linear increasing voltage (CELIV) of the device is done to evaluate the recombination mechanism in the device and to assess the performance of the device. One-dimensional (1D) ZnO nanostructures provide direct paths for charge transport, and also offer large interfacial area to make them an ideal electron transport layer. In chapter 4 highly aligned ZnO nanorods is used as electron transport layer in OPV. Growth of ZnO nanorods is two-step processes, growing seed layer and growing ZnO nanorods from hydrothermal process using an appropriate seed layer. Two different soft-chemical solution- growth methods (upward and downward) are developed to fabricate self-assembled, oriented ZnO nanorods. Substrate mounting, surface properties and optical transmittance are optimized by varying the nanorods growth conditions. Further the ZnO nanorods are UV ozone treated and its effect on performance of nanostructured buffer layer based device is evaluated. In Chapter 5 OPV is fabricated on an opaque FRP substrate. Fabrication of OPV device on opaque substrate plastic is unique and hence understanding various properties is vital. Such devices fabrication require bottom up approach, with transparent electrode as the top electrode and metal electrode on the surface of FRP. FRP has inherent rough surface of about few microns RMS roughness. In order to reduce the roughness of the substrate FRP was planarized. The planarized layer is chosen, such that it chemically binds with the substrate. The chemical interaction between substrate and planarizing coating is evaluated by FTIR and Raman spectroscopy. The binding of planarized layer and FRP is evaluated using nanoscratch technique and surface energies are studied using contact angle measurements. In addition, adhesion properties of the metal electrodes, which are deposited on planarized FRP are evaluated using nanoscratch technique. Fabrication of OPV requires a top transparent electrode. Simple spin coating technique is used to optimize the top electrode. The property of top electrode is evaluated using UV-visible spectroscopy for transmittance, and sheet resistance of the electrode is characterized. OPV device is fabricated on planarized FRP substrate using optimized top transparent electrode and its PV properties is evaluated. Performance of the device is evaluated for two different bottom electrodes and further performance of device is enhanced using buffer layers. Usually flexible OPVs are fabricated on plastic substrate such as PET, PEN. However they are not structurally stable at high temperatures and have high oxygen and moisture Permeability. In Chapter 6 Organic based photovoltaic devices were fabricated on flexible glass. Flexible glass has high strength and it is also known for low oxygen and moisture permeability. Fabrication of device on flexible glass has never been done before and hence, generation of data is necessary for commercialization of the technology. Device fabrication is optimized by using two different transparent conducting layers (ITO- sputter deposited, PEDOT: PSS-solution processed) and device performance was evaluated for both. Since the substrate is flexible in nature understanding the performance of the device during flexing is important. For this 2-parallel plate flexural apparatus is fabricated for in-situ measurements along with current voltage measurements. These devices are flexed cyclically and performance of device is evaluated. Therefore, work discussed in the thesis show by modifying the interface of the device, and understanding various interfaces of the device is crucial for improving the performance of the device. Also by engineering the interface, devices can be fabricated on various types of substrate.

The energy system is being transitioned to increase sustainability. This transition has been accelerated by the increased awareness about the adverse effects of the greenhouse gas (GHG) emissions into the atmosphere. The transition includes switching to electricity as the energy carrier in some sectors, e.g., transportation, increasing the contribution of renewable energy sources (RES) to the grid, and digitalizing the grid services. Electric vehicles (EVs) are promoted and subsidized in many countries among the sustainability initiatives. Consequently, the global sales of EVs rapidly increased in the recent years. Many EV owners might charge their EVs only at home, thereby increasing the residential load. The residential load might further increase due to the initiatives to electrify the heating/cooling sector. This thesis contributes to the knowledge about the operation of the future energy system by modeling the spatial charging load of private EVs in cities, and by proposing a forecasting model to predict the residential load. Both models can be used to evaluate the impacts of both technologies on the local electricity grid. In addition, demand response (DR) schemes can be proposed to reduce the adverse effects of both the charging load of EVs and the residential load. A case study of the EV model on the Herrljunga city grid showed that 100% EV penetration with 3.7 kW (charging rate of 14.8 km/h) chargers will not cause voltage violations in the grid. Winter load is responsible for 5% voltage drop at the weakest bus, and EVs add only 1% to this drop. In a Swedish city, charging EVs will require adding extra 1.43 kW/car to the grid capacity—assuming 22 kW (charging rate of 88 km/h) residential chargers. If the EV charging is not restricted to residential locations, an increase of 1.23 kW/car is expected. The proposed forecasting model is comparable in accuracy to previously developed models. As an advantage, the model produces a probability density function (PDF) describing the model’s certainty in the forecast. In contrast, many previous contributions provided only point forecasts.