<p> Integrating solar energy into the electric vehicle (EV) market alleviates the demand for</p> <p>fossil fuels used to generate the electricity used to power these vehicles. Integrated solar panels</p> <p>provide a new method of power generation for an electric vehicle, but researchers must consider</p> <p>new dependent variables such as drag in the figure of vehicle efficiency. For the solar array to be</p> <p>deemed a viable option for power generation, the solar array must generate enough energy to</p> <p>overcome the added weight and aerodynamic drag forces the solar system introduces. The thesis</p> <p>explores the application of photovoltaic modules for power generation in an EV system.</p> <p>Researchers installed an off-the-shelf solar module on the roof of an EV and investigated the</p> <p>system to explore the efficiency tradeoffs. The research sought to identify an optimized solar</p> <p>panel configuration for minimized drag based on maximized panel surface irradiance, cooling,</p> <p>and array output voltage parameters. The study utilized computational fluid dynamics modeling,</p> <p>wind tunnel testing, and full-scale track testing to analyze the system. The results of this study</p> <p>provide an optimized configuration for a Renogy RNG-100D atop a Chevrolet Bolt. The system</p> <p>was considered optimal at a tilt angle of zero degrees when in motion. The performance benefits</p> <p>due to the increased angle of the solar panel tilt were deemed insufficient in overcoming the</p> <p>aerodynamic drag forces introduced into the system while in motion.</p>

<p dir="ltr">Two-dimensional (2D) perovskite semiconductors are an emerging family of hybrid materials featuring a built-in quantum well architecture which has gained much interest due to its potential as a promising candidate for next-generation photovoltaic and optoelectronic applications. To successfully integrate 2D perovskites as efficient devices, it is imperative that a thorough understanding of the fundamental properties these materials possess and how their complex heterostructures behave is established. However, to date, the synthetic challenges regarding high-quality crystals of these materials due to the structural complexity and the hybrid nature have impeded further progress in this area. Thus, we demonstrate a general method to construct tunable 2D organic semiconductor-incorporated perovskites (OSiP) by simultaneously manipulating slab thickness of the inorganic layers and conjugation length of the organic substituents. The energy band offsets and exciton dynamics at the organic-inorganic interfaces were elucidated using computational means and ultrafast spectroscopy, while lattice dynamics were quantified via temperature-dependent spectroscopy and X-ray diffraction studies. Results show that longer and more planar π-conjugated organic ligands induce a more rigid inorganic crystal lattice, which leads to suppressed exciton-phonon interactions and superior optoelectronic properties such as efficient lasing.</p><p dir="ltr">Furthermore, understanding ion migration in two-dimensional (2D) perovskite materials is key to enhancing device performance and stability as well. However, prior studies have been primarily limited to heat and light-induced ion migration. To investigate electrically induced ion migration in 2D perovskites, we construct a high-quality single crystal 2D perovskite heterostructure device platform with near defect-free van der Waals contact. While achieving real-time visualization of directional ion migration, we also uncover the unique behavior of halide anions inter-diffusing towards the opposite direction under prolonged bias. Confocal microscopy imaging reveals a halide migration channel that aligns with the crystal and heterojunction edges. After sustained ion migration, stable junction diodes exhibiting up to ~1000-fold forward to reverse current ratio are realized. Unraveling the fundamental properties of 2D OSiPs as well as ion migration in 2D perovskite heterostructures paves the way towards stable and efficient devices.</p>

Dans ce manuscrit est décrite l'utilisation d'interactions supramoléculaires pour diriger l'auto-assemblage de composés donneurs et accepteurs d'électrons au sein de dispositifs photovoltaïques organiques. Dans ce but, des matériaux de type oligo-3-hexylthiophène et fullerène ont été fonctionnalisés avec des groupements de reconnaissance complémentaires mélamine – acide barbiturique. La présence de élements solubilisants confère à ces composés une bonne mise en oeuvre permettant la fabrication de dispositifs photovoltaïques à hétérojonction volumique. L'effet de la composition et du post-traitement de la couche active sur la performance de ces dispositifs ont été explorés. Les études de mobilité de charge et des mécanismes de recombinaison au sein de ces matériaux indiquent que l'équilibre entre auto-association et séparation de phases est crucial pour l'efficacité en conversion photovoltaïque. / This research aims to elucidate the use of supramolecular interaction to guide the formation of well-defined nanoscale self-assembled architecture in photovoltaic solar cells as a means to improve device efficiency. Complementary molecular recognition sites based on melamine and barbituric acid were used to obtain functionalized fullerene and oligothiophene materials with superior processibility thanks to the presence of specific solubilizing groups. The efficiency of solid-state devices fabricated using the bulk heterojunction design was studied with respect to device morphology and composition. Experiments on recombination mechanism and field effect mobilities suggest that the balance between hydrogen-bonding interactions induce self-assembly and p-p interactions to promote phase segregation is crucial to the micro-structure of the active layer. The investigated of the relationship between the oligothiophene chain size and various complementary hydrogen-bonding motifs is envisaged.

Recently, researchers on nanoparticles and nanostructures has received a great deal of attention not only in the area of synthesis and characterization but also in their potential application in various high-technological applications. Nanomaterials are widely used not only for environmental and biological applications but also for electronic and sensing applications. Among various classes of nanomaterials, the metal oxide nanostructures possess particular important because of their significant physical and chemical properties which allowed them to be used for the fabrication of highly efficient nanodevices. The metal oxide nanomaterials are widely used for catalysis, sensing, and electronic devices, and so on. Due to the high-efficient applications, researchers have developed several synthesis strategies to prepare metal oxide nanostructures with tailored geometry and utilize them for a variety of applications. However, it is still desirable to prepare metal oxide nanomaterials with environment-friendly precursors and processes with varied size and morphology for their effective utilization in specific applications. This thesis focuses on the synthesis, characterizations and specific applications of two undoped and doped metal oxide nanostructures, i.e. zinc oxide (ZnO) and iron oxide (α-Fe2O3). The thesis highlights the development of novel synthesis techniques/procedures which are rapid, consume less energy and time, and are less cumbersome, more economical, especially because of the low temperature process. The other aspect of the thesis is to use the as-synthesized nanomaterials for several important applications such as sensors, photovoltaic, and photocatalysis. The thesis is divided into several chapters. Chapter 1 starts with a brief introduction of the metal oxide nanostructures and their various synthetic methods. In addition to this, a short review on the targeted applications, i.e. sensing, photovoltaic and photocatalytic, of this thesis was also discussed in this chapter. Finally, the chapter describes the objective and importance of the thesis. Chapter 2 deals with the details of the synthesis and characterization techniques used in this thesis. Two specific techniques, i.e. hydrothermal and thermal evaporation, have been used for the synthesis of various undoped and doped nanomaterials explored in this thesis. The synthesized nanomaterials were examined by variety of techniques in terms of the morphological, structural, optical, compositional and electrical properties. Moreover the prepared nanomaterials together were used for various applications such as sensing, photovoltaic and photocatalytic applications. In a word, this chapter provides all the detailed procedures for the synthesis, characterizations and applications of targeted nanomaterials in this thesis. Chapter 3 describes the main results and discussion of the thesis. This chapter is divided into several sections and each section describes the synthesis, detailed characterizations and particular application of a single metal oxide nanomaterial. Section 1 describes the growth, characterization and ammonia chemical sensing applications of well-crystalline ZnO nanopencils grown via facile and simple hydrothermal process using commonly used laboratory chemicals. Importantly, the fabricated ammonia chemical sensor exhibited ultra-high sensitivity. Section 2 demonstrates the use of ZnO balls made of intermingled nanocrystalline nanosheets for photovoltaic device application. Successful growth, characterizations and phenyl hydrazine chemical sensing applications based on Ag-doped ZnO nanoflowers was demonstrated in section 3 of this chapter. Section 4 describes the Ce-doped ZnO nanorods for the detection of hazardous chemical; hydroquinone. Section 5 exemplifies the facile growth and detailed structural and optical characterizations of In-Doped ZnO hollow spheres composed of nanosheets networks and nanocones. Finally, section 6 illustrates the utilization of α-Fe2O3 hexagonal nanoparticles for environmental remediation and smart sensor applications. Moreover the synthesized α-Fe2O3 hexagonal nanoparticles were characterized in detail in terms of their morphological, structural, compositional and optical properties. Chapter 4 briefly highlights the overall conclusion and an outlook for further investigations suggested by the work undertaken here for this thesis. / Τα τελευταία χρόνια τα νανοσωματίδια και οι νανοδομές έχουν προσελκύσει μεγάλο ερευνητικό ενδιαφέρον λόγω των σημαντικών δυνατοτήτων που προσφέρουν για εφαρμογές υψηλής τεχνολογίας. Τα νανοϋλικά χρησιμοποιούντα ευρέως τόσο για περιβαλλοντικές και βιολογικές εφαρμογές όσο και για εφαρμογές στην ηλεκτρονική και τους αισθητήρες. Μεταξύ των διάφορων κατηγοριών νανοϋλικών, οι νανοδομές μεταλλικών οξειδίων παρουσιάζουν ιδιαίτερο ενδιαφέρον λόγω των φυσικών και χημικών ιδιοτήτων τους, που τους επιτρέπουν να χρησιμοποιούνται για την κατασκευή νανοσυσκευών υψηλής απόδοσης, με χαρακτηριστικά πεδία εφαρμογών την κατάλυση, την ηλεκτρονική και τους αισθητήρες. Για τους σκοπούς αυτούς, έχει αναπτυχθεί πληθώρα μεθόδων για την σύνθεση και προετοιμασία νανοδομών μεταλλικών οξειδίων με επιθυμητές γεωμετρίες, ώστε να είναι κατάλληλα για διαφορετικές εφαρμογές. Παρόλα αυτά, εξακολουθεί να υπάρχει έντονο ενδιαφέρον για την παραγωγή τέτοιων υλικών σε διάφορα μεγέθη και μορφολογίες, με περιβαλλοντικά φιλικές μεθόδους, με απώτερο σκοπό την χρησιμοποίησή τους σε συγκεκριμένες εφαρμογές. Η παρούσα διατριβή εστιάζει στην σύνθεση, τον χαρακτηρισμό και τις εφαρμογές των νανοδομών δύο συγκεκριμένων μεταλλικών οξειδίων (ZnO και α-Fe2O3) με ή χωρίς προσμείξεις. Η διατριβή δίνει έμφαση σε νέες τεχνικές σύνθεσης, οι οποίες είναι γρήγορες, καταναλώνουν λιγότερη ενέργεια και είναι πιο οικονομικές κυρίως λόγω χαμηλότερης θερμοκρασίας επεξεργασίας. Οι δομές των νανοϋλικών που προκύπτουν, χρησιμοποιούνται σε διάφορες σημαντικές εφαρμογές, όπως είναι οι αισθητήρες, τα φωτοβολταϊκά και η φωτοκατάλυση. Η διατριβή χωρίζεται σε 4 κεφάλαια. Στο κεφάλαιο 1 δίνεται μία σύντομη εισαγωγή στις νανοδομές των μεταλλικών οξειδίων και τις διάφορες μεθόδους σύνθεσης. Παρουσιάζονται συνοπτικά τα είδη των εφαρμογών τα οποία θα αποτελέσουν αντικείμενο μελέτης και τέλος περιγράφονται οι αντικειμενικοί στόχοι και η σημασία της διατριβής. Το κεφάλαιο 2 πραγματεύεται λεπτομερώς τις τεχνικές σύνθεσης και χαρακτηρισμού που υιοθετούνται στο μεγαλύτερο μέρος της μελέτης. Συγκεκριμένα, για την σύνθεση των νανοϋλικών (με ή χωρίς προσμίξεις) χρησιμοποιούνται οι τεχνικές της υδροθερμικής και της θερμικής εξάχνωσης. Τα παραγόμενα νανοϋλικά μελετήθηκαν ως προς την σύνθεσή τους, καθώς επίσης και τις μορφολογικές, δομικές, οπτικές και ηλεκτρικές ιδιότητες. Στην συνέχεια, χρησιμοποιούνται για τα διάφορα είδη εφαρμογών που αναφέρθηκαν παραπάνω. Με άλλα λόγια, στο κεφάλαιο αυτό περιέχονται όλες οι λεπτομέρειες των διαδικασιών παραγωγής και των εφαρμογών. Το κεφάλαιο 3 περιλαμβάνει την παρουσίαση και συζήτηση των αποτελεσμάτων. Αποτελείται από διάφορες παραγράφους η κάθε μία εκ των οποίων περιγράφει την σύνθεση, τον χαρακτηρισμό και τις εφαρμογές ενός εκ των υλικών. Στην Παράγραφο 1 περιγράφονται η ανάπτυξη, ο χαρακτηρισμός των κρυσταλλικών ZnO νανομολυβδιών μέσω μίας απλής και εύκολης υδροθερμικής διαδικασίας, χρησιμοποιώντας συνηθισμένα εργαστηριακά υλικά, καθώς επίσης και η εφαρμογή τους ως χημικοί αισθητήρες αμμωνίας. Αξίζει να σημειωθεί ότι οι αισθητήρες που κατασκευάστηκαν επέδειξαν υπέρ-υψηλή ευαισθησία. Η παράγραφος 2 επιδεικνύει την χρήση ZnO σφαιρών που είναι κατασκευασμένες απο αναμιγμένα νανοκρυσταλλικά νανοφύλλα για φωτοβολταϊκές εφαρμογές. Η επιτυχής ανάπτυξη και χαρακτηρισμός ZnO νανολουλουδιών εμπλουτισμένα με Άργυρο καθώς επίσης και η χρήση τους σε εφαρμογές αισθητήρων φαινυλο-υδραζίνης παρουσιάζονται στην παράγραφο 3. Στην παράγραφο 4 περιγράφεται η χρήση ZnO νανοράβδων εμπλουτισμένων με Δημήτριο για την ανίχνευση της επικίνδυνης χημικής ουσίας υδροκινόνης. Στην Παράγραφο 5 παρουσιάζεται η ανάπτυξη και ο λεπτομερής δομικός και οπτικός χαρακτηρισμός κοίλων σφαιρών ZnO εμπλουτισμένων με Ίνδιο που αποτελούνται απο δίκτυα νανοφύλλων και νανοκώνους. Τέλος στην παράγραφο 6 περιγράφεται η χρήση εξαγωνικών νανοσωματιδίων α-Fe2O3 για περιβαλλοντική αποκατάσταση και εφαρμογές ευφυών αισθητήρων. Οι δομές αυτές χαρακτηρίστηκαν λεπτομερώς ως προς τη σύνθεση τις μορφολογικές, τις δομικές και τις οπτικές ιδιότητες. Στο κεφάλαιο 4 παρουσιάζονται τα συμπεράσματα της παρούσας διατριβής καθώς επίσης και προστάσεις για την περεταίρω διερεύνηση των υπό μελέτη συστημάτων.

Les cellules solaires polymériques attirent un grand intérêt dans ce domaine de recherche, en raison du faible coût, du procédé de fabrication de grandes surfaces, des matériaux de manutention légers et de la possibilité de leur fabrication par diverses techniques. Pour une bonne efficacité des dispositifs photovoltaïques, la couche active doit contenir une bonne absorption de la lumière du soleil. En termes de bandgap,cela signifie que plus le bandgap est petit, plus le flux de photons absorbés est grand. Une manière d'accomplir ceci avec les matériaux polymères est la synthèse d'un copolymère alterné dans lequel le bandgap optique est diminué, ce que l'on appelle des polymères low-bandgap. L'organisation joue un rôle important dans la performance des dispositifs, y compris les dispositifs photovoltaïques, et la technique Langmuir-Schaefer (LS) permet de fabriquer des films nanostructurés avec contrôle de l'épaisseur, qui peuvent servir de base pour construire de meilleurs dispositifs. Dans ce contexte, l'objectif de ce travail était de synthétiser des polymères low-bandgap et ensuite de fabriquer et caractériser des films LS de ces polymères et leurs mélanges avec un dérivé de fullerène, le PCBM, pour leur application en tant que couche active de cellules solaires. Les films LS des polymères et leurs mélanges avec PCBM ont été fabriqués et des mesures de caractérisation ont été effectuées. Ces films ont été caractérisés par des mesures électriques (courant vs tension, spectroscopie d'impédance et voltampérométrie cyclique), morphologiques (microscopie à force atomique) et optiques (UV-visible, diffusion Raman et transmission infrarouge). Par les films de Langmuir et les mesures morphologiques, il a été possible d'observer les caractéristiques spécifiques concernant la conformation de chaque polymère sous forme de film. Des mesures optiques confirment l'absorption aux longueurs d'onde élevées attendues pour ces polymères. Dans les mesures électriques, les résultats ont montré des conductivités différentes pour les mêmes matériaux lorsque les types d'électrodes ont été changés. Les dispositifs photovoltaïques des films LS fabriqués n'ont pas atteint de bonnes valeurs d'efficacité. Les films spin-coating de ces polymères testés en tant que couche active des dispositifs, sous atmosphère contrôlée, ont montré unefficacité allant jusqu'à 0,6%. / Polymeric solar cells attract great interest in this area of research due to the potential low cost, large area fabrication process, light weight physical feature and the possibility of fabricating these cells by several techniques. To achieve good efficiency in the photovoltaic devices the active layer must have an efficient absorption of sunlight. In terms of bandgap, this means that the smaller the bandgap the greater the flux of photons absorbed. One way to accomplish this, with the polymeric materials, is the synthesis of a polymer in which the optical bandgap has the ability to increase the capture of sunlight, the so-called low-bandgap polymers. The organization plays an important role in the performance of devices, including in photovoltaic devices, and the Langmuir-Schaefer (LS) technique provides the ability to manufacture nanostructured films with thickness control, which can serve as a basis for building better devices. In this context, the aim of this work was to synthesize low-bandgap polymers for later manufacturing and characterization of LS films of these polymers and their blends with a fullerene derivative, PCBM, and test them as active layer of solar cells. LS films of such polymers and their blends with PCBM were made and characterization measurements were performed. These films were characterized by electrical (current vs. voltage, impedance spectroscopy and cyclic voltammetry), morphology (atomic force microscopy) and optical (ultraviolet-visible, Raman scattering and infrared) measurements. Through the Langmuir films and the morphological measurements, it was possible to observe the specific characteristics of how it is the conformation of each polymer in film form. Optical measurements confirmed the absorption at high wavelengths expected for these polymers. In the electrical measurements the results showed different conductivities for the same materials when the types of electrodes were changed. The photovoltaic devices manufactured from LS technique have not reached good efficiency values. When spin-coated active layers were teste as OPV devices in a controlled atmosphere the efficiency achieved up to 0.6%. / Células solares poliméricas atraem grande interesse nessa área de pesquisa, devido ao baixo custo, processo de fabricação de grandes áreas, materiais de manuseio leves e a possibilidade de sua fabricação por diversas técnicas. Para uma boa eficiência dos dispositivos fotovoltaicos, a camada ativa deve conter uma boa absorção da luz solar. Em termos de bandgap, isto quer dizer que quanto menor o bandgap maior o fluxo de fótons absorvidos. Uma maneira de realizar isto com os materiais poliméricos é a síntese de um polímero no qual o bandgap óptico tem a capacidade de aumentar a captura da luz solar, os chamados polímeros low-bandgap. A organização possui um papel importante na performance de dispositivos, inclusive dos fotovoltaicos, e a técnica Langmuir-Schaefer (LS) proporciona a capacidade de fabricar filmes nanoestruturados e com controle de espessura, podendoservir de base para construção de melhores dispositivos. Dentro deste contexto, o objetivo deste trabalho foi sintetizar polímeros low-bandgap e, posteriormente fabricar e caracterizar filmes LS destes polímeros e de suas blendas com um derivado de fulereno, o PCBM, para a aplicação dos mesmos como camada ativa de células solares. Foram fabricados filmes LS dos polímeros e de suas misturas com PCBM e realizadas medidas de caracterização. Estes filmes foram caracterizados por meio de medidas elétricas (corrente vs. Tensão, espectroscopia de impedância e voltametria cíclica), morfológica (microscopia de força atômica) e óptica (Ultravioleta-Visível, Espalhamento Raman e transmissão no infravermelho). Com os filmes de Langmuir e as medidas morfológicas foi possível observar as características específicas de como é a conformação de cada polímero na forma de filme. As medidas ópticas confirmam a absorção em altos comprimentos de onda esperados para estes polímeros. Nas medidas elétricas os resultados mostraram diferentes condutividades para os mesmos materiais quando mudado os tipos de eletrodos. Os dispositivos fotovoltaicos dos filmes LS fabricados não alcançaram bons valores de eficiência. Filmes spin-coating destes polímeros testados como camada ativa dos dispositivos, em atmosfera controlada, revelaram eficiência de até 0.6%.

<div>In a world of ever-increasing demand for energy while preventing adverse effects of climate</div><div>change, renewable energy has been sought after as a sustainable solution. To this end,</div><div>the last couple of decades have seen an advancement in research and development of solar</div><div>photovoltaic (PV) technology by leaps and bounds. This has led to a steady improvement</div><div>in the cost-effectiveness of solar PV as compared to the traditional sources of energy, e.g.,</div><div>fossil fuels as well as contemporary renewable energy sources such as wind and hydropower.</div><div>To further decrease the levelized cost of energy (LCOE) of solar PV, new materials and</div><div>technologies are being investigated and subsequently deployed as residential, commercial, and</div><div>utility-scale systems. One such innovation is called bifacial PV, which allows collection of</div><div>light from the front as well as rear surfaces of a flat PV panel.</div><div><br></div><div>In this thesis, we present a detailed investigation of bifacial solar PV farms analyzed across</div><div>the globe. We define the problem, explore the challenges, and collaborate with researchers</div><div>from academia and the PV industry to find a novel solution.</div><div><br></div><div>First, we begin by developing a multi-module computational framework to numerically</div><div>model a utility-scale bifacial solar PV farm. This requires integrating optical, electrical,</div><div>thermal, and economic models in order to estimate the energy yield and LCOE of a bifacial</div><div>PV system. The first hurdle is to re-formulate the LCOE so that the economist and the</div><div>technologist can collaborate seamlessly. Thus, we re-parameterize the LCOE expression</div><div>and validate our economic model with economists at the National Renewable Energy Lab</div><div>(NREL).</div><div><br></div><div>Second, we extend the existing optical and electrical models created for stand-alone</div><div>bifacial PV panels to models that can simulate a large-scale bifacial solar PV farm. This</div><div>brings the challenge of mathematically modeling solar farms and light collection on the rows</div><div>of PV panels elevated from the ground by taking into account the mutual shading between</div><div>the rows, reflections from the ground, and elevation-dependent light absorption on the rear</div><div>surface of the PV panels from several neighboring rows. Next, we integrate temperaturedependent</div><div>efficiency models to take into account the effects of location-dependent ambient</div><div>temperature, wind speed, and technology-varying temperature coefficients of the solar PV</div><div>system in consideration.</div><div><br></div><div>Third, we complete the comprehensive modeling of bifacial solar PV farms by including</div><div>two types of single-axis tracking algorithms viz. sun-tracking and power tracking. Using these</div><div>algorithms, we explore the best tracking orientation of solar farms i.e., East-West tracking</div><div>vs. North-South tracking for locations around the world. We further find the best land type</div><div>suitable for installation of these E/W or N/S tracking bifacial solar PV farms.</div><div><br></div><div>Fourth, we reduce the computation time of numerical modeling by utilizing the advantages</div><div>of machine learning algorithms. We train neural networks using data from the alreadybuilt</div><div>models to emulate the numerical modeling of a solar farm. Amazingly, we find the</div><div>computation time reduces by orders of magnitude while accurately estimating the energy</div><div>yield and LCOE of PV farms.</div><div><br></div><div>Fifth, we derive, compare, and experimentally validate the thermodynamic efficiency</div><div>limits of photovoltaic-to-electrochemical energy conversion for the purpose of storing solar</div><div>energy for future needs.</div><div><br></div><div>Finally, we present some new ideas and guidelines for future extensions of this thesis as</div><div>well as new challenges and problems that need further exploration.</div>

<p dir="ltr">Transitioning to a carbon-neutral future will require a broad portfolio of green energy generation and storage solutions. With the abundant availability of solar radiation across the Earth’s surface, energy generation from photovoltaics (PVs) will be an important part of this green energy portfolio. While silicon-based solar cells currently dominate the PV market, temperatures exceeding 1000 °C are needed for purification of silicon, and batch processing of silicon wafers limits how rapidly Si-based PV can be deployed. Furthermore, silicon’s indirect band gap necessitates absorber layers to exceed 100 µm thick, limiting its applications to rigid substrates.</p><p dir="ltr">Solution processed thin-film solar cells may allow for the realization of continuous, high-throughput manufacturing of PV modules. Thin-film absorber materials have direct band gaps, allowing them to absorb light more efficiently, and thus, they can be as thin as a few hundred nanometers and can be deposited on flexible substrates. Solution deposition of these absorber materials utilizing molecular precursor-based inks could be done in a roll-to-roll format, drastically increasing the throughput of PV manufacturing, and reducing installation costs. In this dissertation, solution processed synthesis and the characterization of two emerging direct band gap absorber materials consisting of earth abundant elements is discussed: the enargite phase of Cu₃AsS₄ and the distorted perovskite phase of BaZrS₃.</p><p dir="ltr">The enargite phase of Cu₃AsS₄ (ENG) is an emerging PV material with a 1.42 eV band gap, making it an ideal single-junction absorber material for photovoltaic applications. Unfortunately, ENG-based PV devices have historically been shown to have low power conversion efficiencies, potentially due to defects in the material. A combined computational and experimental study was completed where DFT-based calculations from collaborators were used inform synthesis strategies to improve the defect properties of ENG utilizing new synthesis techniques, including silver alloying, to reduce the density of harmful defects.</p><p dir="ltr">Chalcogenide perovskites are viewed as a stable alternative to halide perovskites, with BaZrS₃ being the most widely studied. With a band gap of 1.8 eV, BaZrS₃ could be an excellent wide-bandgap partner for a silicon-based tandem solar cell.Historically, sputtering, and solid-state approaches have been used to synthesize chalcogenide perovskites, but these methods require synthesis temperatures exceeding 800 °C, making them incompatible with the glass substrates and rear-contact layers required to create a PV device. In this dissertation, these high synthesis temperatures are bypassed through the development of a solution-processed deposition technique.A unique chemistry was developed to create fully soluble molecular precursor inks consisting of alkaline earth metal dithiocarboxylates and transition metal dithiocarbamates for direct-to-substrate synthesis of BaZrS₃ and BaHfS₃ at temperatures below 600 °C.</p><p dir="ltr">However, many challenges must be overcome before chalcogenide perovskites can be used for the creation of photovoltaic devices including oxide and Ruddlesden-Popper secondary phases, isolated grain growth, and deep level defects. Nevertheless, the development of a moderate temperature solution-based synthesis route makes chalcogenide perovskite research accessible to labs which do not have high temperature furnaces or sputtering equipment, further increasing research interest in this quickly developing absorber material.</p>

Photoelectrodes and photovoltaic devices have been prepared via multiple thin film deposition methods. Aerosol assisted chemical vapour deposition (AACVD), electrodeposition (ED), chemical bath deposition (CBD) and doctor blade technique (DB) have been used to deposit binary and ternary metal oxide films on FTO glass substrates. The prepared thin films were characterised by a combination of SEM (Scanning Electron Microscopy), powder X-ray diffraction, mechanical strength tests and photochemical measurements. Nickel oxide (NiO) thin films prepared by AACVD were determined to have good mechanical strength . with a photocurrent of 7.6 μA cm-2 at 0 V and an onset potential of about 0.10 V. This contrasted with the dark current density of 0.3 μA cm-2 at 0 V. These NiO samples have very high porosity with crystalline columns evidenced by SEM. In comparison with the AACVD methodology, NiO films prepared using a combination of ED and DB show good mechanical strength but a higher photocurrent of 24 μA cm-2 at 0 V and an onset potential of about 0.10 V with a significantly greater dark current density of 7 μA cm-2 at 0 V. The characteristic features shown in the SEM are smaller pores compared to the AACVD method. Copper (II) oxide (CuO) and copper (I) oxide (Cu2O) films were fabricated by AACVD by varying the annealing temperature between 100-325°C in air using a fixed annealing time of 30 min. It was shown by photocurrent density (J-V) measurements that CuO produced at 325 °C was most stable and provided the highest photocurrent of 173 μA cm-2 at 0 V with an onset potential of about 0.23 V. The alignment of zinc oxide (ZnO) nano-rods and nano-tubes fabricated by CBD have been shown to be strongly affected by the seed layer on the FTO substrate. SEM images showed that AACVD provided the best seed layer for aligning the growth of the nano-rods perpendicular to the surface. Nano-rods were successfully altered into nano-tubes using a potassium chloride bath etching method. NiO prepared by both AACVD and the combined ED/DB method were sensitized to absorb more of the solar spectrum using AACVD to deposit CuO over the NiO. A large increase in the photocurrent was observed for the p-type photoelectrode. These p-type photoelectrode showed a photocurrent density of approximately 100 μA cm-2 at 0 V and an onset potential of 0.3 V. This photocathode was then used as a base to produce a solid state p-type solar cell. For the construction of the solid state solar cells several n-type semiconductors were used, these were ZnO, WO3 and BiVO4. WO3 and BiVO4 were successfully produced with BiVO4 proving to be the optimum choice. This cell was then studied more in depth and optimised by controlling the thickness of each layer and annealing temperatures. The best solid state solar cell produced had a Jsc of 0.541 μA cm-2 (541 nA) and a Voc of 0.14 V, TX146 made up of NiO 20 min, CuFe2O4 50 min, CuO 10 min, BiVO4 27 min, using AACVD and then annealed for 30 min at 600°C.