This thesis aimed to process and characterize hydrogenated germanium (Ge:H) films to use them as a low-bandgap intrinsic absorber layer. The bandgap of Germanium can go down to 0.67 eV. A p-i-n solar cell consisting of intrinsic germanium film produced using Plasma Enhanced Chemical Vapour Deposition (PECVD) can be inexpensively paired with crystalline silicon and other semiconductor materials to produce a multi-junction solar cell with high efficiencies. Such a cell would utilize the lower part of the solar spectrum currently untapped in commercially available mass-produced solar modules. Previous research had deposited Ge:H films using a counterflow PECVD reactor, as compared to a showerhead configuration in the reactor used in this research.

The study consisted of experiments that explored the properties of the germanium film deposited. First, the deposition parameters of PECVD were varied to study its effect on important film properties. Since the germanium layer will be used in a solar cell as the absorber layer, the band-gap and activation energy were the most critical parameters to monitor film intrinsicity. Experiments were performed by depositing germanium layers on glass substrates and silicon wafers to understand the properties of the films when deposited at different temperatures and also when the germane flow was altered. The effect of the power and pressure on the properties of the germanium samples was studied too. In all these experiments, the deposition time and electrode gap are kept constant. The processing window of 3-4.5 mbar and 12-20 W where intrinsic amorphous germanium (a-Ge:H) films can be produced was identified.

Single junction solar cells in p-i-n and n-i-p configuration were then incorporated with the intrinsic amorphous germanium. The p-i-n configuration displayed solar cell characteristics, whereas the n-i-p configuration cells did not, despite the changes in doping of the p-layer. Further experiments were carried out to look into the stability of the material by repeating the J-V curve measurement of the first cell that showed solar cell characteristics, but similar behaviour was not observed. Additionally, Raman spectroscopy was carried out, which revealed that the material is amorphous.

In summary, the results look promising in proving these films as a suitable material for an intrinsic absorber layer. It also strongly suggests that the showerhead PECVD configuration can lead to better control of reaction mechanics, giving films with desired material properties. The layer can be used as an intrinsic layer in a p-i-n structure device, but further investigation is required to look into the interaction of the layers of the solar cells.

This research investigates the optimal integration of power and heat grids to meet energy demands in the Drechtsteden region at minimal costs. Driven by the global push for decarbonization, the study explores the cost-effectiveness of reinforcing the existing power grid versus expanding the heat grid infrastructure, including the potential of waste heat utilization. A Python-based model, leveraging the PyPSA library, was developed to simulate and optimize different scenarios. It was found that reinforcing the power grid is the most cost-effective solution for satisfying the 2030 heat demand, assuming stable geopolitical conditions and material availability. However, under specific conditions, such as decreased heat grid connection costs or abundant waste heat sources, a combined approach might become more viable. The sensitivity analysis highlights the significant impact of technology costs on decision-making. Future research should incorporate resource constraints, long-term projections, and spatial limitations for a more comprehensive assessment of energy system integration.

High conversion efficiencies and low production costs have placed Silicon heterojunction (SHJ) solar cells as one of the top contenders in the photovoltaic market right now. When combined with the interdigitated-back-contacted (IBC) architecture, SHJ-IBC cells set world record efficiencies for silicon cells: in 2024, the record stands at 27.3% efficiency. However, the IBC architecture introduces complex processing steps. The goal of this project is the simplification of processing steps of SHJ-IBC solar cells, obtained with the use of hard masks for the direct deposition of patterned layers.

The first part of the project is focused on the development of hard masks. First, silicon based hard masks have been fabricated using wet and dry etching methods. Their fabrication process has been optimized until high quality masks with low defect rates have been achieved. In addition to these masks, quartz mask samples provided by a third party have been tested. Deposition of 50 and 100nm of (n) nc-Si:H have been made with all masks to evaluate their potential based on their resolution, quality, reusability and price. While quartz masks have demonstrated to be very promising and industry orientated, the best trade-off of qualities in a research environment has been found in dry etched silicon masks.

In the core of the project, dry hard masks have been used to substitute two photolithography steps in the fabrication flowchart of IBC-SHJ solar cells in order to achieve a significant process simplification. The use of hard masks has brought relevant impacts to the SHJ-IBC cell fabrication, like the removal of wet etching steps that can potentially bring uncertainty to process flowchart and the reduction of the processing time to half of what it was before the use of hard masks. Regarding the depositions made through the hard masks, the challenges of obtaining a precise alignment and accurate feature sizes been assessed. The implication of those challenges in the performance of the solar cells has been then evaluated.

Lastly, the thesis introduces a simplified fabrication process of SHJ-IBC solar cells with the implementation of hard masks. With the new fabrication process, efficiencies of up to 5.47% have been demonstrated. Through the introduction of the SHJ-IBC flowchart based on hard mask patterning, the project contributes to the ongoing effort to bring SHJ-IBC cells closer to the industry.

Over the past decade, global efforts to combat climate change have focused on transitioning from fossil fuels to renewable energy sources and battery-based energy storage. This shift is essential to meet the rising global energy demand and integrate renewable power into the grid. However, the current AC based grid infrastructure poses challenges for incorporating DC based renewable sources like photovoltaic (PV) systems and battery storage. A rapid transition from AC to DC systems is impractical, necessitating a grid system that leverages the existing AC infrastructure while integrating DC systems. Hybrid microgrids (HMGs) have emerged as a solution to this challenge.

Our research focuses on a crucial component of HMGs: the Interlink Converter (ILC). Ideally, the two subgrids in a hybrid microgrid generate power to meet their respective demands. When one subgrid cannot meet its demand, the other supports it through the ILC. This system works effectively most of the time. However, during simultaneous power deficiencies in both subgrids, current standards prioritize AC loads, transferring power from the DC to the AC subgrid. This can lead to voltage fluctuations or blackouts in the DC subgrid, which is increasingly problematic as critical DC loads like EV charging stations and data centres grow.
The thesis titled ‘AC-DC Priority Control of an Interlink Converter’ aims to develop an optimal control strategy for ILCs, enhancing their ability to prioritize power transfer between AC and DC subgrids based on priority modes. This research is crucial for future grid stability and the integration of renewable energy sources.