The excessive use of the fossil fuel has attributed to the emission of carbon dioxide causing rising temperature. To counter act over this, the renewable based energy transition and lithium-ion batteries as storage facility in changing the landscape. However, these lithium-ion batteries prone to thermal runaway, lower operating conditions, dendrite formation making them vulnerable to the transition. All solid-state batteries are the next generation batteries making an revolution in the battery technology by replacing the highly volatile liquid electrolyte to the solid electrolyte for improved safety, high energy density (Li/Si possible to use the anode material), and longer cycle life.

In this thesis, the halide incorporation in lithium argyrodite 𝐿𝑖6-x𝑃𝑆5-x𝑋1+x (X= Cl, Br, I) solid electrolyte was synthesized and further characterized to understand the synthesis conditions and structural-ionic transport correlation of solid electrolyte. The halide enriched lithium argyrodite was synthesized using mechano-chemical synthesis by high energy ball milling and followed by heat treatment. All samples were investigated using following characteristics tools such as X-Ray diffraction, scanning electron microscopy, Raman spectroscopy, and Electrochemical impedance spectroscopy, to understand the structural information, morphology and the ionic conductivity of the composition. In results, the chloride/Bromide enriched in lithium argyrodite shows a higher ionic conductivity of around 14.77 mS 𝑐𝑚-1 for 𝐿𝑖5.5𝑃𝑆4.5𝐶𝑙1.5 and 6.39 mS 𝑐𝑚-1 for 𝐿𝑖5.5𝑃𝑆4.5Br1.5, and various annealing temperatures could improve the crystallinity of composition which also influences the higher ionic conductivity.

As we know from the literature, the lithium argyrodite based solid electrolyte has a narrow electrochemical stability window. It is interesting to note that altering the structure can influence this stability. We have also determined the electrochemical stability window of the chloride-enriched lithium argyrodite (𝐿𝑖5.5𝑃𝑆4.5𝐶𝑙1.5) in both BM and HT samples and compared with the commercial lithium argyrodite (𝐿𝑖6𝑃S5𝐶𝑙) by using linear sweep voltammetry. Additionally, we performed the electrochemical stability window of 𝐿𝑖6𝑃𝑆5𝐵𝑟, 𝐿𝑖5.7𝑃𝑆4.7Br1.3, and 𝐿𝑖5.5𝑃𝑆4.5Br1.5 composition. We observed the halide enriched lithium argyrodite show better electrochemical stability windows.

Overall in this thesis, the processing of halide enriched lithium argyrodite 𝐿𝑖6-x𝑃𝑆5-x𝑋1+x (X = Cl and Br) exhibits cubic crystal structure, various occupancies of halide on 4d site with high ionic conductivity, and good electrochemical stability window to development of all solid-state batteries.

To make silicon thin film solar cells attractive to the market, their efficiencies should reach the efficiencies of the dominant crystalline silicon solar cell. Therefore the search for ways to improve the efficiency of silicon thin film solar cells continues. TCO front contact layers and back reflector layers play a significant role in the increase of thin film solar cell efficiencies. For the optical characterization of these TCO layers, commonly used methods are found to differ significantly in results regarding the extinction coefficient which makes their accuracy questionable.

This research consists of two main parts. For the first part, the commonly used optical characterization methods spectroscopic ellipsometry and spectrophotometry + data analysis in SCOUT are analyzed in accuracy and compared to newly introduced methods using spectrophotometry + data analysis in GenPro4 and photothermal deflection spectroscopy + data analysis in GenPro4 to build a guide on optical characterization of TCO materials. For the second part, the optical response determined using the software GenPro4 of a double junction silicon thin film solar cell for a novel bi-layer front contact design consisting of IOH and i-ZnO will be compared to the optical response for standard used AZO, and ITO single layers to find the best front contact design. Furthermore, the optical response of a double junction silicon thin film solar cell for a back reflector containing an i-ZnO layer on top of the silver back contact will be compared to the optical response for a back reflector containing an AZO layer on top of the silver back contact to find the best back reflector design.

From the results of the optical characterization methods, it is concluded that photothermal deflection spectroscopy + data analysis in GenPro4 is the most accurate method for determining the extinction coefficient of a TCO material. The results of the optical simulations for front contact TCO and back reflector TCO designs showed that the bi-layer can enhance the optical response of a double junction silicon thin film solar cell significantly compared to the AZO and ITO single layers. The i-ZnO TCO back reflector layer was found to induce less parasitic absorption and therefore a better optical response of the double junction silicon thin film solar cell.

Batteries play a vital role in the ongoing energy transition, driving the demand for safer, energy denser and higher performing energy storage solutions. This has propelled research of solid-state batteries. Halide electrolytes, with high ionic conductivities and high oxidation stabilities, have attracted tremendous interest. Currently, the main challenge is that most promising halide solid electrolytes are reliant on expensive and scarce metals, hindering their application at an industrial scale. Therefore, it is of great significance to develop cost-effective halide electrolytes. Zr-based electrolytes show great promise due to their cost-effectiveness (ZrCl₄ = 12.5 USD/kg) and high abundance in the earth's crust (165 mg/kg). However, so far their conductivity have been unsatisfactory, falling below 1 mS/cm. Anion doping with elements like Cl, Br, I, and O has demonstrated to be effective in improving the conductivities of sulfide solid electrolyte. In this work, the O-doping effect is investigated in Zr-based halide solid electrolytes with Li_2xZrCl₄O_x. By using various analysis techniques such as X-ray diffraction, electrochemical impedance spectroscopy, and cyclic voltammetry, this study explores the relationship between compositions, conductivities, and phases within the Li_2xZrCl₄O_x system. The findings reveal that, for each Zr-based oxyhalide composition, varying ball milling times result in different phases, with the most amorphous phase displaying the highest ionic conductivity. Specifically, for x = 1, Li₂ZrCl₄O reaches 1.60 mS/cm after 17.2 hours of ball milling, characterized by a structure featuring 61% amorphous content. Additionally, it demonstrates good performance as an all-solid-state battery with LiNi_0.8Mn_0.1Co_0.1O₂/ Li₂ZrCl₄O/ Li₆PS₅Cl/Li-In, achieving an initial capacity of 125.6 mAh/g at 0.5C and retaining 67.47% capacity after 1000 cycles. Moreover, the impact of I-doping is further explored in Li₃YCl₃Br_3-xI_x, another cost-effective halide solid electrolyte (YCl₃ = 330 USD/kg and 33 mg/kg). The Li₃YCl₃Br_3-xI_x electrolyte displays tunable conductivity and stability characteristics with an excellent conductivity of 3.55 mS/cm for x = 1 compared to 1.94 mS/cm for x = 0 but with a trade-off in oxidation potential of 3.474 V to 3.59 V. This study provides insights into novel cost-effective electrolytes and exhibits the potential of anion doping in enhancing and tuning both conductivity and stability. These electrolytes hold a serious potential as a solid electrolyte in solid-state batteries.

Perovskite solar cells (PSCs) are an emerging and promising photovoltaic technology that have demonstrated impressive power conversion efficiencies exceeding 25% after only fourteen years of development. This rapid progress can mostly be attributed to the development and optimisation of PSCs fabricated by solution-based methods, because of their easy processing and inexpensive equipment. However, to commercialise PSCs, alternative methods are required. Among these methods, the vacuum-based technique thermal evaporation is a suitable candidate. In thermal evaporation, solid precursors are evaporated and deposited onto a substrate in a high vacuum chamber. Thermal evaporation is a mature technique in the semiconductor industry to fabricate pinhole-free and highly uniform thin films at a large scale on different types of substrates. To date, the efficiency of PSCs by thermal evaporation is lagging behind their solution-based counterpart, partly due to limited research on vacuum deposited PVK films and several challenges unique to thermal evaporation.
In this MSc thesis project, organic-inorganic metal halide perovskite absorbers based on thermally evaporated FAxCs1-xPb(IyBr1-y)3 and spin-coated MAPbI3 have been developed together with the additional supporting layers for device fabrication. Several PSCs with different p-i-n architectures have been fabricated and characterised. The device comprises of: ITO as front electrode, spiro-TTB, spiro-OMeTAD and/or MoOx as hole transport layer, PVK absorber layer, C60 as electron transport layer, BCP as buffer layer, and silver and aluminium as metallic back electrode. The goal of this work is to develop and optimise the structural and opto-electronic properties of different device layers and demonstrate a working perovskite solar cell.
PVK engineering is carried out on both thermally evaporated and spin-coated PVK thin films with the aim at obtaining perovskite that possesses desirable opto-electronic properties. For FAxCs1-xPb(IyBr1-y )3 fabricated by sequential layer thermal evaporation, the uniformity and tooling factors were optimised to grow layers with a correct precursor ratio showing a high crystallinity and absorptance. No clear effect of post annealing could be detected for the temperatures and times tested in this work. Achieving the target thickness and obtaining a satisfactory reproducibility were not fully reached. For spin-coated MAPbI3, it was found that increasing the precursor solution concentration helped to achieve a desirable thickness for PSCs. Moreover, an adequate bandgap, diffractogram and absorptance were measured. However, based on the small crystal size determined with SEM, and poor device performance, further improvement is needed.
Transport, contact, and buffer layers were successfully fabricated by developing new deposition recipes for silver, BCP, and spiro-TTB. Furthermore, spectrophotometry measurements show that thermally evaporated HTLs (MoOx and spiro-TTB) exhibit much lower parasitical absorption losses compared to spin-coated spiro-OMeTAD. An optical model to fit spectroscopic ellipsometry data measured on spiro-TTB thin films is created to determine its thickness and optical properties. Moreover, time resolved microwave conductivity results indicate that C60 effectively extracts electrons from MAPbI3. In contrast, spiro-TTB films did not appear to possess any hole extracting abilities. Strong quenching of the steady-state PL signal is observed for bi-layers of MAPbI3 with either C60, spiro-OMeTAD and MoOx . This quenching is possibly caused by extraction of either electrons or holes and/or enhanced non-radiative recombination at the interface.
The optimised films were combined in complete PSCs with most layers fabricated by thermal evaporation through metal masks structuring cells with active areas of 0.16 and 0.36 cm2. Solar cells were characterised in the dark and under illumination using a solar simulator integrated with a glove box to prevent degradation. A wide range of J-V characteristics are identified and classified: (1) ohmic responses, possibly caused by poor quality PVK absorber layers with pinholes filled with thermally evaporated metal, (2) S-shaped curves under illumination, possibly caused by a mismatch in energy band alignment or increased non-radiative recombination at the MoOx/MAPbI3 interface, (3) diode behaviour in the dark, and (4) a high series resistance and low shunt resistance, possibly caused by low mobility, non-optimal thicknesses, internal currents, and a mismatches in band alignment. The most promising PSC featuring the ITO (200 nm)/Spiro-OMeTAD/MoOx (5 nm)/MAPbI3/C60 (20 nm)/BCP (4 nm)/Ag (150 nm) architecture, had a short circuit current of 10.0 mA/cm2 and an open circuit voltage of 0.67 V.
The experiments carried out in this MSc thesis project supported the development of several steps of PSC fabrication process. This work contributes towards understanding thermal evaporation processes of perovskite films and fabricating fully evaporated devices with high efficiency and a large area.

A new intense positron beam lifetime spectrometer is being developed at the Reactor Institute Delft that should be able to perform positron lifetime measurements with depth profiling. The positrons are generated by pair formation using high energy gamma-photons from the Hoger Onderwijs Reactor. This new positron lifetime spectrometer has a unique way to determine the point in time when a positron is injected into the sample material. Before the positrons are injected, they travel through a carbon foil which will then release secondary electrons. These secondary electrons are detected by a microchannel plate detector which starts a timer. Once the positron annihilates within the sample it releases two 511 keV photons. If one of these photons is detected, the timer is stopped, and the elapsed time is stored. Many measurements of the elapsed time are needed to create a positron lifetime spectrum.

The main research goal is to further develop this new positron lifetime spectrometer such that it is able to measure a positron lifetime spectrum. Multiple adaptations and tests were performed in order to achieve the research goal.

At the start of the project, the positron lifetime spectrometer could not deliver a thermalized positron beam from its 50 nm thick tungsten moderator. This problem was solved by reannealing this moderator. Additionally, a new moderator was prepared and annealed. The Variable Energy Positron (VEP) facility was used to perform characterization measurements on the moderators. This facility was modified to allow the transmission of positrons through the moderator and measure emitted thermalized positrons by the moderator. At the same time, a model based on the positron transport equation was developed to simulate and verify the characterization experiments. Both the old and new moderator have shown that they can emit thermalized positrons. The old moderator has a measured efficiency of 0.073 ± 0.002 when the positron implantation energy equals 3.7 ± 0.1 keV. The new moderator has a measured efficiency of 0.123 ± 0.002 when the positron implantation energy equals 3.2 ± 0.1 keV.

During the project, the microchannel plate detector which measures secondary electrons had to be tested, because no detections were observed in previous experiments. Additionally, the scintillation detector which is used to measure annihilation photons was tested. Eventually, both detectors have showed that they work correctly.

Finally, the positron beam of the lifetime spectrometer was aligned such that the positrons travel through the carbon foil onto the target. Secondary electrons generated by positrons have been measured by the microchannel plate detector. Afterwards, the first positron lifetime spectrum was measured using this new instrument. This lifetime spectrum is still rather crude as it shows multiple peaks and a time resolution function with a full width half maximum of 0.57 ns. The research goal of this project has been achieved, but further development is needed in order to accurately measure positron lifetimes.

Within the PVMD group at TU Delft, the study of perovskite/c-Si tandem solar cells is being researched. A comprehensive study is performed through advanced optical and electrical simulations to understand the tandem’s characteristics and operative behavior. We use GenPro4 and Sentaurus TCAD to perform the optical and electrical simulations, respectively. From the previous research, the developed J-V simulations revealed an indication of extra current collection from the tandem’s supporting layers. This extra current density makes the tandem’s short circuit current density J_SC higher than the current-matched J_ph of each perovskite and c-Si absorber layer. Because only J-V curves that could be simulated and not the EQE curves, it remained a mystery of which supporting layers in the tandem that contribute to the extra current collection. In this thesis project, a new EQE simulation methodology was developed to help to solve this mystery of extra current collection from the supporting layers. By performing the EQE simulation, we find that SnO2, TiO2, and Spiro-OMeTAD layers contribute to a total potential extra current collection of 2.50 mA/cm2 to 2.79 mA/cm2. A further study of the extra current collection is also conducted by modifying the simulation method that considers the absorbed photons’ energy in respect to the material’s energy bandgap. Under this further study, only absorbed photons with energy higher than the material’s energy bandgap can generate electron-hole pairs. After considering the absorbed photons’ energy in the simulation, only SnO2 and TiO2 layers that contribute to the significantly lower extra current collection of 0.07 mA/cm2.

The need for more efficient, cheaper, easily producible solar cells is growing as this combination of attributes can decrease the levelized cost of energy (LCOE). A two­terminal (2T) Perovskite and galliuminidium­gallium­selenide (Pvk/CIGS) tandem cell is an excellent candidate, as it can have a power conversion efficiency (PCE) of +30%, can be flexible (making it suitable for roll­-to­-roll production), and
the deposition of a Pvk solar cell (PSC) on top of established techniques like CIGS will only add one extra step to the production process, thereby improving the PCE significantly

This thesis is part of LAFLEX­-2T project which aims to design and engineer a highly efficient flexible 2T thin­-film solar device based on the Pvk/CIGS tandem configuration. The aim of this thesis is to develop an opto­-electrical model of the tandem configuration which replicates the inner physics of a reference solar cell. This can be used to give insights on the current losses occurring in the cell and on the limitations in the charge carrier transport towards the electrodes. Based on this analysis, a route of improvements is proposed with could result in more efficient solar cells.

The simulation template uses optical and electrical simulations based on GENPRO4 and TCAD Sentaurus, respectively. An extensive model for Pvk/CIGS tandem cells is presented and validated using experimentally obtained J­-V curve measurements. It was found that charge transport in the tunnel recombination junction (TRJ) depends on direct energy and in­direct energy transfer, in terms of two tunneling mechanisms: band to band tunneling (B2BT) and trap assisted tunneling (TAT). For TAT, a non­-local model facilitated by trap states is successfully implemented.
Simulation results reveal that the transport in the TRJ of the reference solar cell is based on TAT. The loss analysis points out that reflectance losses are responsible for a loss of 10.92 mA/cm². Similarly, losses due to parasitic absorption are equal to 5.32 mA/cm². The CIGS bottom was identified as the current limiting layer. The dominant recombination mechanisms in the Pvk and CIGS absorber layers are Shockley-­Read­-Hall (SRH) and surface recombination calculated as 4.71 mA/cm² and 1.59 mA/cm² for top Pvk and bottom CIGS, respectively. An increase in losses in the absorber layers in maximum power point (MPP) compared to short circuit (SC) conditions exposed charge transport issues in the collecting path of charge carriers.
After assessing the loss mechanisms, a road­map for efficiency improvements is proposed. After implementation, an increase in the PCE of the reference tandem cell was observed from 10.63% to 26.69%.

Modified Newtonian Dynamics (MOND) can account for a variety of phenomena on galactic scales without the need for dark matter, but it cannot fully explain the mass contained in galaxy clusters. We explore two possible solutions to this problem: relativistic extensions of MOND, and FEM simulations of the apparent matter distribution in clusters, utilising the non-linear AQUAL formulation to analyse non spherically symmetric systems. We consider Covariant Emergent Gravity, and we show that the theory is inconsistent with the original formulation of Emergent Gravity. Moreover, we show that either the theory is incompatible with observations, or it presents grave theoretical difficulties. We then suggest that a covariant formulation of EG can be obtained through a Generalised Einstein Aether (GEA) theory, which is capable of retrieving the MOND PDE, and is, at the same time, consistent with observational constraints. Regarding the FEM simulations of the apparent matter distribution in galaxy clusters, we construct a sample of 15 clusters from the catalogs of Reiprich and Abell for the baryonic mass distribution present in galaxy clusters. We choose FEM for its ability to treat the combination of continuous and discrete mass distributions without the need for smoothing. This is necessary, as in MOND we cannot apply the principle of superposition or the weak lensing formalism. We then utilise the FeniCS software package to study the properties of these clusters. We simulate each cluster with elements up to degree 3, thanks to a speedup by a factor of ∼ 100 obtained by the use of local mesh refinement for the serial case. In addition, we run the code in parallel on a single-threaded 8-core CPU, achieving near optimal weak scaling for the regime of interest. For the mass distribution in the galaxy clusters, we analyse the distribution of baryons, Phantom Dark Matter (PDM) and apparent mass both close to the core and around each galaxy. We find that the PDM tends to clump around the galaxies, regardless of the gas to galaxy mass ratio. Moreover, we show that both the apparent mass and the PDM can exhibit negative masses as predicted by Milgrom. Our observations on the density of PDM around the galaxies match recent observations of small scale weak lensing. In addition, our results for negative mass distributions provide an opportunity to test a prediction of MOND that can never be replicated in the dark-matter paradigm, and shed light on the properties of non-spherically symmetric mass distributions, that have, up to now, not been studied in the literature for the fully non-linear case.

Advancements in energy storage technologies need to keep pace with the accelerating transition to renewable energy sources. Li metal anodes and high voltage cathode materials are widely considered to be the path into next generation Li-ion batteries, while the scare amounts of lithium in the earth's crust has prompted research into other battery materials. Of these, Sodium-ion batteries are extremely interesting due to the abundance of Na, similar insertion chemistry to Li as well as the possibility of using aqueous electrolytes due to higher redox potential. Next generation Li-ion batteries are currently held back due to issues like - dendrite formation at the metal anode which may lead to internal short circuiting and thermal runaway of the organic electrolyte. Similarly, Na-ion systems have issues with organic electrolytes due to the limited solubility of Na electrolyte salts. Solid state electrolytes (SSEs) have rapidly garnered interest as a potential alternative. SSEs vastly improve battery safety due to their superior thermal stability and mechanical strength. However, there are still limitations for SSEs in both these systems that need to be resolved prior to implementing these electrolytes in commercial batteries.In this study, alginate salts, which are natural polysaccarides extracted from brown algae, have been examined as a solution to the problems in these systems. Initially, sodium and lithium salts (NaAlg and LiAlg) of alginic acid were synthesized followed by their physical characterization. Conductivity for sodium and lithium alginate (with 0% water) were both promising at 0.2 mS/cm. Additionally, both LiAlg and NaAlg exhibit excellent performance as binders in anode systems compared to PVdF (polyvinylidene difluoride) binders.For utilizing the LiAlg in Li solid-state batteries, NaSICON-based LAGP electrolyte was synthesized and characterized for this study. The degradation of LAGP on Li contact has already been well researched. To combat the issue, we try to utilize a layer of LiAlg as protective layer at the LAGP surface. The coated LAGP remains stable against Li without undergoing degradation. The Li cyclability and electrochemical performance of LiAlg was further analysed by coating it on a various electrodes and studying their rate capabilities against Li. LiAlg displayed excellent performance as a secondary polymer electrolyte on the surface and in the bulk of the electrodes. These tests show exceptional cycling performances and establish a proof of concept for LiAlg as a polymer electrolyte.NaAlg which was chosen as the electrolyte in Na-ion batteries, displays better gelation properties. The effects of water content and operating temperature on Na conductivity were investigated. For a fixed water content, increasing the temperature results in improved conductivity - though this effect is more prominent at higher water concentrations and within the margin of error at lower water concentrations. At a fixed temperature, the conductivity shows linear improvement in at low (<25%) and high (>90%) water concentrations, while remaining constant between 25% and 90%. Additionally, the performance of NaAlg electrolytes (2w% NaAlg aq. solution) and GPE (20w% NaAlg Gel Polymer Electrolyte) was compared with the conventional Na2SO4 electrolyte. During these tests, the electrolyte underwent degradation possibly caused due to cross-linking induced by the dissolution of Mn2+ from the cathode on de-sodiation. Nevertheless, as a proof of concept, the NaAlg showed promise as an electrolyte (aq. and GPE) but further system optimization needs to be done to fully establish its scope as electrolytes for Na batteries.