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Abstract: Quatsomes (QS) are highly stable unilamellar nanovesicles formed by the self-assembly of quaternary ammonium surfactants and sterols. Despite their growing potential as nanocarriers, the molecular determinants of QS membrane structure and mechanics remain poorly understood, limiting the rational design of optimized formulations. Here, we investigate the effect of surfactant chain length, counterion identity, and solution ionic content on the structural and nanomechanical properties of cholesterol-based QS membranes assembled from alkyltrimethylammonium (CnTA+) salts. Supported bilayers and multilamellar membrane stacks were characterized under varying ionic conditions using atomic force microscopy (AFM), AFM-force spectroscopy, X-ray reflectivity, and molecular dynamics simulations. While surfactant chain length (C14 vs C16) had only minor effects on membrane stiffness and negligible influence on fluidity, counterion identity emerged as the dominant factor governing membrane behavior. Smaller chaotropic tendence, as provided by Cl- compared to Br-, promoted tighter molecular packing, resulting in more compact, stiffer membranes with reduced fluidity and greater resistance to AFM tip penetration, an effect that was further enhanced by increasing the ionic concentration of the surrounding environment. These findings highlight the critical role of ionic composition in regulating QS membrane organization and mechanics, providing a framework for the rational design of QS-based nanomaterials.

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Abstract: Vacuum-deposited organic solar cells (OSCs) have lagged behind their solution-processed counterparts in achieving high power conversion efficiency (PCE), in particular as result of higher voltage losses. In this study, we demonstrate a bulk heterojunction OSC using SubNc as donor and DCV3T as non-fullerene acceptor, achieving a PCE of 2.6% and a remarkably low total voltage loss of 0.64 V, lower than the typical values exceeding 0.7 V observed in vacuum thermally evaporated fullerene-based systems. The device also exhibits non-radiative voltage losses comparable to leading non-fullerene-acceptor (NFA) based OSCs. Transient absorption spectroscopy confirms efficient Förster resonance energy transfer from DCV3T to SubNc, followed by electron transfer for exciton separation. Morphological Grazing Incidence Wide-Angle X-ray Scattering features suggest both blends have a preferential edge-on orientation of DCV3T molecules, and the blends with higher DCV3T content could suffer from suppressed out-of-plane lamellar crystallinity with possible connection with greater non-radiative losses. Our findings demonstrate the potential of designing low-voltage-loss evaporated OSCs by building on strategies from solution-processed NFA systems, while highlighting the continued need for new evaporable acceptors with optimised optoelectronic and morphological properties.

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Abstract: Achieving ultranarrow spectral linewidth and broad spectral tunability in light-emitting diodes (LEDs) remains challenging due to linewidth broadening from compositional and size heterogeneities. Here we report an interface-regulated vapour crystallization strategy that enables precise control over the spectral linewidth of solution-processed halide perovskite thin films. Underlying materials that exhibit minimal molecular interactions with perovskite precursors, exemplified by poly(9-vinylcarbazole), facilitate smooth ion diffusion and crystallization assisted by dimethylformamide vapour. This mechanism leads to perovskite films with both horizontal and vertical homogeneity and low inhomogeneous broadening comparable to that of perovskite single crystals. We demonstrate perovskite films with ultranarrow photoluminescence linewidths of 13.6 nm, 13.7 nm, 13.8 nm and 14.4 nm for emissions at 464 nm, 474 nm, 483 nm and 522 nm, respectively. This enables us to achieve sky-blue perovskite LEDs with narrow electroluminescence linewidths of 14.7 nm and a peak external quantum efficiency of 24.6%, with comparable linewidths and performance in LEDs spanning the pure blue to pure green. This work offers a practical and scalable strategy to realize narrow spectral linewidth, broad spectral tunability and high performance in thin film LEDs.

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Abstract: Perovskite solar cells (PSCs) offer a promising pathway towards low-cost, high-efficiency photovoltaics. However, conventional PSCs require at least two charge transport layers (ETL and HTL), increasing fabrication complexity and cost. ETL-free PSCs present a cost-effective alternative but suffer from energy-level misalignment at the perovskite/electrode interface, leading to charge recombination and efficiency losses. Recent studies have employed interfacial modifications to improve energy alignment, yet these still retain multilayer structures. In this work, we developed a simplified, fully ETL- and HTL-free PSC architecture (FTO/Cs0.1 (FA0.88MA0.12)Pb(I0.7Br0.3)(CsFAMA 1.7 eV)/Phenethyl ammonium iodide (PEAI)/Carbon) via introducing 1-ethyl-3-methylimidazolium acetate (EMIM Ac) into the perovskite layer, causing better energy level alignment, reduced trap density, and improved crystallinity. The fully striped-down structure surprisingly achieves an efficiency of 12.53% under 1,000 lux, sufficient to be a battery replacement for indoor energy frugal IoTs, while lowering production costs by minimizing layers and processing steps. Our findings highlight ultra-lean PSCs, which comprise of only perovskite and two electrodes, demonstrating the simplified solar cell structure to date, which is fully capable of powering indoor IoT applications.

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Abstract: Nuclear fusion power is the promise of clean energy generation to meet the demands of the new century. However, containing a plasma with a core temperature ten times hotter than that of the sun is no easy task. The confinement vessel must be constructed from resilient materials that can withstand both the heat and the bombardment of the plasma species. ITER is the first proof-of-concept reactor in constructed. This thesis aims to assist in ITER's goals of understanding the complex fundamental plasma-material interactions and developing materials resilient to the harsh reactor conditions in the global push for nuclear fusion energy. The first goal of the thesis aims to investigate the thermodynamic properties of helium (He) bubbles to contribute to the existing understanding and models of He PMI expected in ITER. Bulk W samples were exposed to a low-energy (25 eV) He plasma at 573 K (LT) and 1050 K (HT). After plasma exposure, these samples were subject to TDS, ERDA, SEM, and in-situ TEM annealing. Structures comprised of a network of bubbles were stable up to 998 K during in-situ TEM annealing of the LT sample. He desorption from the LT sample was inferred to stem from interstitial He rather than these bubbles. Bubbles in the HT sample were found to be thermally active up to 998 K, resulting in an increase in the average bubble size and a loss of number density. GISAXS analysis on the effects of annealing on bubble radius distribution produces results consistent with the TEM. An "Ostwald ripening-like" model was proposed to explain the differences in annealing behaviours of the LT and HT samples. In-situ TEM annealing of a HT bulk W sample at 1073 K showed a reconfiguration of lattice atoms to reduce the surface area of large voids left behind after plasma exposure. It is suggested that lattice effects also contribute to the formation of fuzz and require more investigation. The results provided a deeper understanding of the bubble formation mechanism and subsequent thermodynamics based on the plasma exposure temperature. The differences in behaviour observed from these experiments can be used to help explain temperature-dependent effects such as recrystallisation suppression and form a wide set of consistent experiments for computational models to be compared to. The second goal of the thesis is to characterise the He-PMI of three alloys for possible use as a divertor material in future fusion reactors. Four sputter-deposited materials: sputtered pure W (WS), W-5%(wt)Ta, W-3%(wt)Cr, and W-5%(wt)Ta-3%(wt)Cr were exposed to 25 eV He plasma at LT and HT. After plasma exposure, these materials were subject to TDS, ERDA, SEM and TEM. The addition of Ta to Ws and WCr has been shown to inhibit the formation of He bubbles. This may be a case of increasing the fluence threshold for fuzz rather than the complete prevention of fuzz. Additionally, the addition of Ta slows grain growth of both Ws and WCr. This property is intrinsic to Ta rather than from an emergent W-Ta interaction and could potentially be used to delay the undesired but inevitable onset of recrystallisation. The electrical resistivities of the four sputtered films were measured as a surrogate for its thermal conductivity to characterise how this property changes with alloying and He exposure. The alloying of Ta significantly increases the resistivity of W, much more than that of Cr. As expected, He plasma exposure degrades the resistivity regardless of the material. WTaCr has the largest electrical resistivity and suffers the largest increase after He plasma exposure likely due to the presence of both alloying impurities deforming the lattice and serving as trapping sites. Both effects increase probability of electron scattering. The reduction in thermal conductivity from both alloying and He plasma irradiation, especially for alloys with more elements, will have to be considered alongside its other benefits when determining its viability for fusion reactors.