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Halide perovskites are the leading candidates for next-generation, low-cost optoelectronics with power conversion efficiencies well above 25%. However, operational stability remains a key challenge. Although there is an understanding that the microscale and nanoscale play a consequential role in determining the macroscopic performance and stability, significant gaps remain in the mechanistic understanding of degradation processes at the nanoscale and the mechanisms for stability in cation-alloyed systems. Nanoscale hexagonal phase impurities have been identified as problematic for operational stability, leading to both performance losses and morphological degradation. However, it is still unclear at what stage these phase impurities originate. Understanding this better is critical in order to mitigate the harmful effects of these phase impurities on performance and operational stability. Cation alloying is a commonly used technique in the field to mitigate these hexagonal phase impurities, although not without its challenges. In this thesis study, the nanoscale structural landscape of key halide perovskite compositions is studied. By taking snapshots of the perovskite at different states of the annealing process, the impact of phase impurities on device performance is characterised. Thereon, the mechanism by which composition dictates photostability in FA-rich perovskite absorber layers is studied. It is demonstrated that the composition impacts the degree of octahedral tilt, which is essential to restricting the transition to hexagonal phase impurities. Additionally, it is demonstrated that while a judicious mix of A-site cations can be used to stabilise the photoactive black phase of halide perovskites, it is challenging to achieve this homogeneously over large areas, necessitating a search for alternative or complementary approaches to stabilise perovskite via octahedral tilt. Using scanning electron diffraction (SED) studies, the spacegroup of additive-stabilised-CsPbI3 is demonstrated to be a low symmetry tilted γ-phase. Furthermore, using SED, the nanoscale structural landscape of mixed-phase CsPbI3 absorber layers is studied and it is demonstrated that both narrow-bandgap γ-phase and wide-bandgap δ-phase co-exist at the nanoscale, enabling stable and bright white-light emission. Overall, this thesis provides insights into the role of nanoscale structure in dictating the properties and behaviour of halide perovskites and offers rational guidelines for their optimisation and use in optoelectronic devices. Additionally, it is demonstrated that SED is a powerful tool for studying these materials at the atomic scale, allowing for the detailed characterisation of their structures and properties.

This thesis comprises three independent papers on applied microeconomics. The first chapter studies the impact of primary care provider mergers on quality in England. The second chapter investigates the effect of price dispersion on consumer search behavior, drawing evidence from the retail gasoline market in Greece. The final chapter builds on the second, studying the asymmetric price adjustment and the impact of market competition on the asymmetric price adjustment. The details of the three papers are summarized below: The Effects of General Practice Mergers on Quality in England The primary care market has witnessed a growing trend of provider consolidation through mergers and acquisitions, yet the implications of this concentration remain uncertain. This study addresses this gap by providing the first empirical evidence on the effects of provider mergers on quality using evidence from the English primary care market. By analyzing all provider mergers from 2014 to 2018, I find predominantly negative effects of mergers on quality. Clinical quality does not change at best, and patient satisfaction decreases dramatically. Notably, the impact on quality varies based on the size of the general practices involved. Mergers between large general practices show a detrimental impact on quality, while mergers between small general practices may yield quality benefits. Additionally, there is no difference in the quality impact between mergers involving parties in the same geographical market and those in different markets. An exploration of the mechanism reveals that mismanagement, rather than changes in market concentration, drives the observed decline in quality following mergers. The Effect of Competition and Price Dispersion on Search Behavior We investigate the impact of price dispersion on consumer search behavior, while credibly controlling for market structure. Using the retail gasoline market on isolated, oligopolistic markets, as defined by small Greek islands, we exploit an excise duty tax increase policy as a plausibly exogenous shock to price dispersion. We directly measure consumer search using the number of user visits to a price information platform and mobile application. We find that the tax shock increases price dispersion and that in turn causes a short term increase in consumer search. The effect of price dispersion on consumer search remains regardless of market competition level. Asymmetric Pass-Through and Competition We study the pass-through to retail prices of four major changes in taxes for petroleum products (three increases and one subsequent decrease). We use daily pricing data from gas stations on small Greek islands, which define isolated markets with different number of competitors. First, we find that, on average, the pass-through of the tax hikes is five times higher than for the tax decrease. Second, the pass-through of the tax hikes increases with the number of competitors, but that of the tax decrease does not vary with competition (asymmetric competition effect). Third, there is significant asymmetry in the speed of price adjustments. Fourth, the asymmetric adjustment of retail gasoline prices cannot be explained by tacit collusion and the evidence points to search as the most plausible explanation.

This thesis examines a group of freemen trading in coal at Newcastle upon Tyne in the sixteenth century known as the Hostmen’s Company. The Newcastle hostmen had established an unincorporated guild by 1508 and held the monopoly in the sale of coal from the town’s port during the rapid expansion of the Tyneside coal trade in the half-century from 1550. Their guild was granted legal status by the Crown in 1600. Existing research on the activities of the Newcastle hostmen in the sixteenth century offers important evidence about their monopoly but leaves open questions about the organization and membership of their guild. No comprehensive history of the Tudor hostmen has been attempted before. There has been no detailed assessment of their ascendancy or the trade of their principal members during a period of decisive change in the mining and sale of Tyneside coal and England’s transition to an industrial economy. This thesis uses little-explored town chamberlains’ accounts to investigate the origins, trading networks, family connections, and business activities of the Tudor hostmen for the first time. The accounts show that hosting coal at Newcastle was confined to a small group of citizens drawn mainly from the town’s mercantile and civic elite, and their widows. Some strangers, gentlemen, craftsmen, and yeomen also participated in the hosting trade. After the Dissolution of the Monasteries and the armed rebellions of the English Roman Catholic nobles the principal hostmen used their capital, political power, and religious connections to acquire the bulk of newly available mining land in the vicinity of Newcastle, creating a de facto monopoly in the production as well as the sale of coal. The hostmen shipped Tyneside coal to markets on the English coast, France, the Netherlands, and the Baltic Sea and had gained control over Newcastle’s governance by the mid-sixteenth century. This thesis shows the importance of two urban-industrial coal dynasties founded by the Newcastle corn merchants James Lawson (d. 1544) and Henry Anderson (d. 1559). Members of the Lawson-Anderson oligarchy dominated mining and hosting in Elizabethan Newcastle at a time when there was a more than three-fold increase in the volume of coal leaving the town’s port by the seaborne trade. They mined extensively in the vicinity of Newcastle on the banks of the River Tyne, created the most developed industrialized landscape in Elizabethan England, and built the two biggest integrated coal businesses in the town while continuing to trade as merchants in a wide variety of commodities. This thesis shows that the Lawson-Anderson oligarchy continued to dominate the Tyneside coal trade in the first half of the seventeenth century, though some of their members suffered heavy losses in the Civil War.

Formate production via both CO2 reduction and cellulose oxidation in a solar-driven process is achieved by a semiartificial biohybrid photocatalyst consisting of immobilized formate dehydrogenase on titanium dioxide (TiO2|FDH) producing up to 1.16±0.04 mmolformate gTiO2-1 in 24 hours. Isotopic labelling experiments with 13C-labelled substrates support the mechanism of stoichiometric formate formation through both redox half-reactions. TiO2|FDH was further immobilized on hollow glass microspheres to perform more practical floating photoreforming allowing vertical solar light illumination with optimal light exposure of the photocatalyst to real sunlight. Enzymatic cellulose depolymerization coupled to the floating photoreforming catalyst generates 0.36±0.04 mmolformate mirr-2 after 24 h. This work thus presents simultaneous solar-driven valorization of waste streams, demonstrates the advantages of biohybrid photocatalysts in photoreforming for the first time and will provide inspiration for the development of future semi-artificial waste-to-chemical conversion strategies.

This thesis grapples with two distinct but interrelated issues: Indigenous climate sovereignty and the imagination of climate apocalypse. It is particularly concerned with how these two themes intersect in the High North, a landscape continually constructed as a periphery and frontier. In the pages that follow, I explore the misalignments between colonial projections of the land and its people, and the lived experiences of climate change and colonialism as I encountered them in two Alaska Native villages. This thesis is rooted in a multisited ethnography in Norton Sound, in Western Alaska. The ethnographic object of this study is not Alaska Native communities, but rather the forms of politics that connect rural Indigenous governments to colonial centres of power in the United States Federal government. In that sense, the research presented here is as much a political ethnography as it is an environmental one. The conclusions presented in this thesis are fourfold. 1) Marginalised Alaska Native communities face a neo-colonial pressure whereby, in order to receive assistance, they are required to adopt the bureaucratic forms and logic of their colonisers; 2) the manner in which the Arctic has been enlisted to support popular apocalyptic climate discourse echoes the modernist role the region played in 19th- and 20th-century constructions, as a mirror for urban humanity; 3) social scientists and humanities scholars have broadly neglected the importance of situating knowledge about climate change and ecological futures, and instead resort to sweeping, planetary gestures; and 4) urban narratives of climate apocalypse offer a potent antidote to political alienation.

Removal of nitrogen compounds in wastewater represents more than 10% of the total electrical demand of the integral water cycle. However, more than 80% of the nitrogen in wastewater comes from urine, where it is highly concentrated in the form of urea (20000 mg L-1). Urea contains a significant amount of hydrogen in its structure which, if recovered, makes urea a potential source of green energy. This thesis demonstrates a novel approach for the energy recovery from urea present in urine at the production source, using decentralised wastewater treatment systems. A new process has been developed in this thesis based on the integration of three steps. In the first step, adsorption is used to recover urea from urea, overcoming the energy limitations of thermal treatments applied to big water volumes. In the second step, thermal treatment is used to desorb the urea, achieving the regeneration of the adsorbent and the production of ammonia. Finally, in the third step, ammonia is used as hydrogen storage molecule to catalytically produce hydrogen on demand. The adsorption of urea is evaluated using activated carbon, determining that urea adsorbs due to physical interactions with i) delocalised π electrons of the pristine surface of the carbon and ii) carboxyl functional groups. The adsorption of urea is reduced when working with real urine due to the presence of organic compounds with affinity for activated carbon that interferes with the adsorption of urea. Thermal treatment of adsorbed urea leads to desorption of urea and regeneration of activated carbon showing a stable urea adsorption capacity during 4 consecutive adsorption/desorption cycles. Simultaneously, ammonia is produced with a 50 – 60 % yield, which is coupled with an ammonia decomposition catalyst to obtain hydrogen. Pilot trials are developed and installed in relevant environments as conventional and waterless urinals, where a social analysis shows a good acceptance towards the solution and pointed some aspects for improving. Energy analysis shows a positive balance due to the combination of the hydrogen produced and the savings in the traditional nitrogen removal. Furthermore, economic analysis indicates that the direct use of ammonia to produce electricity or fertilisers can be a competitive alternative to the obtention of hydrogen.

To meet the increasing demand for sustainable products, one can look to nature to scout new functional materials. For instance, the most brilliant and striking colours in plants are obtained using cellulose nanofibrils organised in helicoidal architectures. Interestingly, similar helicoidal architectures with analogous optical response can be obtained in vitro by self-assembly of cellulose nanocrystals (CNCs). CNCs are rod-like colloids capable of arranging into a liquid crystalline phase above a critical concentration in suspension. So far, the process that governs the self-assembly of CNCs into photonic structures was studied only at small scale. This neglects the limitations and challenges posed by large-scale and continuous processes which are prevalent in industrial contexts. In this thesis, I demonstrate how the self-assembly of CNCs can be precisely controlled to produce meters-long films using a roll-to-roll (R2R) equipment. Starting with commercially available material, the preparation of CNC suspension was optimised for R2R deposition to produce films with vibrant photonic colour across the visible range. Particularly, I discuss how the suspension properties, the casting parameters and drying time relate to the optical properties of the produced films. To validate the use of such materials for pigment preparation, I develop a protocol to produce a series of coloured microparticles from R2R-cast CNC films. The optical properties of the CNC microparticles were then assessed in various environment and finally benchmarked against other commercial effect pigments and glitters.

Species extinctions reduce the diversity of functions that an ecosystem can provide, with negative effects for both natural habitats and society. Rewilding is the restoration of these ecosystem functions by returning locally extinct species or their ecological analogues to an environment. Rewilding also has the potential to limit the impact of future climate change on species and ecosystems by introducing or reintroducing species to areas that will be climatologically suitable in the future. The interplay between rewilding and climate change is particularly relevant to the conservation of reptiles. Reptiles respond rapidly to climate change and support important ecosystem functions. As such, climate change is likely to cause local extinctions and range shifts of reptile species, disrupting the ecosystem functions they provide. Despite this, rewilding projects and related research have largely overlooked reptile species. In this thesis I took an interdisciplinary approach, drawing on neontological and palaeontological data and techniques, to examine the interplay between climate change and rewilding in the context of the conservation of reptiles and the ecosystem functions they support. I used the genus *Varanus* as a model taxon to understand how reptiles contribute to ecosystem functions and respond to climate change. To study the contribution of reptiles to ecosystem functions in the context of rewilding, I investigated the response of heath goannas (*Varanus rosenbergi*) of the Yorke Peninsula, South Australia to rewilding interventions as part of the Marna Banggara Rewilding Project (Chapter 2) and quantified their contribution to scavenging services within the landscape (Chapter 3). I found that goanna populations were increasing slowly in response to the control of invasive European mammals as part of the rewilding project. However, I suggested further action must be taken beyond merely controlling invasive species to support the recovery of reptile populations and reinstate the ecosystem functions they support. I went on to quantify the ecosystem services supported by heath goannas as scavengers and found that they play an important role in removing carcasses and reducing agriculturally harmful blowfly populations and therefore are a good candidate for rewilding to expand the range of the population and the services it supports. I used a variety of ecological modelling approaches to study the responses of *Varanus* species to climate change. Using species distribution models, I identified climatic variables as the major determinant of *Varanus* species distributions out of a suite of abiotic, biotic, and anthropogenic variables (Chapter 4). This suggested that climate change will have major and direct effects on the distributions of *Varanus* species. I went on to develop a novel ecometric modelling approach, utilising machine learning technology and fossil data to predict the responses of *Varanus* species to climate change (Chapter 5). My models predicted major range shifts in large species of *Varanus* over the next 100 years. Therefore, any rewilding projects including reptiles should integrate forecasted range shifts into their planning. This could include introducing species that have not lived in a region in recent history but are predicted to have suitable habitat there in the future, rather than reintroducing those that have recently gone extinct from an area but will not retain suitable habitat due to climate change. I brought my study of ecosystem functions and responses to climate change together to investigate the response of heath goannas to climate change and suggest appropriate conservation management responses to maintain the ecosystem functions supported by the species in the face of these changes (Chapter 6). I found that climate change is likely to drive local extinction of heath goannas from much of their current range. However, I also identified that protected areas will act as refuges from the effects of climate change. I suggested that action to expand protected areas may be the best approach to minimise the risk of local extinction of this functionally important species. My research demonstrates that large reptiles, such as members of the genus *Varanus*, provide important roles in ecosystems and should be active targets for rewilding projects. Climate change is likely to cause major and rapid shifts in reptile ranges; conservation planning needs to account for these shifts by taking forecasted range shifts into account. My findings highlight the need for conservation planning and action at large spatial and temporal scales to protect reptiles and the functions they provide for ecosystems worldwide.

Over the past decade, lead-halide perovskites (LHPs) have demonstrated significant potential in terms of their performance across a wide range of optoelectronic devices, including solar cells, photodetectors and light-emitting diodes. However, the toxicity of lead and instability issue of LHPs are still concerns for their widespread implementation. These successes, but also the challenges of LHPs have motivated great efforts across multiple disciplines to search for lead-free and stable alternatives that can have similar optoelectronic properties to LHPs, namely ‘perovskite-inspired materials (PIMs)’. With the deeper understanding of defect tolerance displayed in LHPs, a large number of PIMs have been identified until now. Among all the identified PIMs, ternary chalcogenides or ABZ2 materials, are believed to be one of the most promising alternatives so far, owing to their simple fabrication protocols, strong absorption and high stability in air. Particularly, AgBiS2 solar cells have demonstrated the highest efficiency (9.17%) among all bismuth-based solar cells. Nevertheless, studies into ternary chalcogenides are mostly limited to AgBiS2 photovoltaics, and the investigations into other potential ABZ2 materials or broader applications are rare so far. Therefore, this thesis will aim to investigate the optoelectronic properties of another promising while rarely investigated ABZ2 material – NaBiS2, and also the potential of AgBiS2 as near-infrared (NIR) photodetectors. In the first project of this thesis, NaBiS2 nanocrystals (NCs) have been shown to exhibit extremely strong absorption, along with a comparatively sharp absorption onset. However, optical-pump-terahertz-probe (OPTP) measurements indicated that most free charge-carriers in NaBiS2 NCs will be localised within a few picoseconds. These localised charge-carriers only exhibited low mobility of around 0.03 cm2 V-1 s-1 and could not transport effectively even though they might be rather long-lived in NaBiS2 and unaffected by intentionally-introduced defects. With help from density functional theory (DFT) calculations, all of these unusual characteristics in NaBiS2 have been shown to closely associate with intrinsic cation disorder, which was also observed in AgBiS2. Although post-annealing is effective for improving cation inhomogeneity and enhancing absorption in AgBiS2, its effect on NaBiS2 was found to be rather minor, which also indicated that the charge-carrier localisation process in NaBiS2 could not be significantly mitigated after annealing. Based on the fundamental insights acquired in the first project, the possibility of further improving charge-carrier transport in NaBiS2 NCs through ligand exchange treatment was investigated in my second project. Using a variety of correlated spectroscopic characterisation techniques, I found that NaBiS2 NCs treated by inorganic iodide ligands had enhanced sum mobility and surface photovoltage (SPV) signals, which implies an improvement in the macroscopic charge-carrier transport. However, the ultrafast localisation process was still observed in these iodide-treated NaBiS2 NCs, suggesting that their cation disorder was not greatly changed. At the same time, the defect capture rates were also found to be lower in the iodide-treated NaBiS2 NCs based on my two proposed models for describing charge-carrier dynamics. As a result, solar cells based on these iodide-treated NaBiS2 NCs could exhibit a peak external quantum efficiency (EQE) value over 50%, along with a power conversion efficiency exceeding 0.7%. Although this is an order of magnitude larger than previous reports, I found ion migration to be a limiting factor for NaBiS2 devices from temperature-dependent transient current measurements, where a low activation energy of only 88 meV was extracted. In my third project, AgBiS2 photodetectors were fabricated and characterised in depth. Aside from the broadband photo-response across from ultra-violet (UV) to near-infrared (NIR) region, AgBiS2 photodetectors have demonstrated an extremely high cut-off frequency (f-3dB) on MHz order, indicating their great potential in applications requiring fast device response such as optical communications. The mechanism behind this fast response was studied, and a relatively long drift length compared to the AgBiS2 film thickness is believed to be the key reason. Similar to NaBiS2 devices, ion migration was also found easy in AgBiS2 devices with an activation energy of 124 meV, which could lead to their increasing noise currents with time. Importantly, these noise currents could be also effectively suppressed when optimising the AgBiS2 film thickness, in which a balance between large shunt resistant and cumulative quantity of defects should be reached. Finally, owing to the small bandgap of AgBiS2 NCs (~1.2 eV), AgBiS2 photodetectors could effectively monitor the heartbeat rates by probing the transmission change of blood vessels illuminated by NIR light, which has been widely used in the medical field owing to its deeper penetration in tissues. These three projects not only uncovered several remarkable optoelectronic characteristics of ABZ2 materials, but also investigated possible methods to further alter these characteristics. Although ABZ2 materials have shown great potential as light harvesters, it can be seen that both cation disorder (or charge-carrier localisation) and ion migration are still limiting the performance. More studies on the root causes of both phenomena, and how to effectively suppress their effects on the materials, would be hence crucial in the future work. With more understandings on this material class, we could expect more efficient, stable, and cleaner optoelectronic devices to be realised in the future.