Throughout the development of crystalline-silicon/perovskite tandem solar cells, the degradation rate of the perovskite top cells has become a limiting parameter. Currently, perovskite faces stability issues, mainly caused by corrosion and the light-soaking effect. This work investigates the degradation rate of the perovskite top cell, where a model is created to determine the parameters from the single diode model that change the IV-curve of a solar cell and lifetime energy yield simulations were performed to find the maximum tolerable degradation rate of perovskite in a tandem module to obtain a higher energy yield compared to a single-junction module Using experimental data from the King Abdullah University of Science and Technology (KAUST), where the external parameters from the measurements were provided, the changes over time in the ideality factor, saturation current, shunt resistance, and series resistance were estimated, using a numerical model. Linear trend lines through the fitting parameters over time were used and lifetime energy yield simulations were performed. For these simulations, a crystalline-silicon/perovskite tandem cell with an efficiency of 31.1% was compared to to a single-junction cell with an efficiency of 23.9%, where the single-junction cell’s optics are the same as the tandem cell’s bottom cell. To perform lifetime energy yield simulations, the PVMD toolbox is used.
Simulating the lifetime energy yield over 10 years, a perovskite degradation rate of 27.5%/year was found using the electrical parameters under STC, where the power output decreased from 4.95W to 0.24W per cell. Comparing 2T and 4T configurations, where the cell optics were kept the same, degradation rates of 21.2%/year and 9.5%/year were found for 2T and 4T, respectively. Looking at different geographical locations, degradation rates of 19%, 20%, 20.6% and 21.2% per year were found for Delft, Lagos, Lisbon and Shanghai, respectively. These differences were caused by current mismatch between the top and bottom cell, where the highest mismatch of 0.55 mA/cm2 was found in Shanghai.
To determine the maximum tolerable degradation rate of the perovskite top cell resulting in a higher lifetime energy yield for a tandem module compared to a single-junction module over 25 years, various degradation rates were analyzed. The perovskite degradation rate must be lower than 1.5%/year and 3.1%/year for 2T and 4T configurations, respectively, assuming no degradation in the silicon single-junction cell and the tandem cell’s bottom cell.

Renewable energy sources, such as thin-film silicon solar cells, show a lot of potential as the technology promises low production temperatures, low cost and low material usage. Other benefits are the flexible and very lightweight modules that can be fabricated, which enable a wide variety of applications. Other benefits include the low-temperature coefficient and low toxicity of the materials used to create thin-film silicon solar cells. The downside of using thin-film silicon modules is the relatively low power conversion efficiency inherent to the amorphous and nanocrystalline silicon. Another downside of amorphous silicon solar cells is their significant initial degradation, known as the Staebler-Wronski effect. This initial degradation will stabilize after time but does limit the ultimate conversion efficiency, especially for single-junction devices.
Hydrogenated amorphous silicon (a-Si:H) and nano-crystalline silicon (nc-Si:H) solar cells can be added in series to form a tandem device, thus increasing the efficiency of thin-film silicon solar cells. Although the current will be limited for 2-terminal tandem devices, a significant increase in open circuit voltage can be achieved resulting in higher efficiencies. To achieve highly efficient thin-film silicon solar cells a combination of good optical, electrical and material properties need to be combined. Extensive research has been done to achieve such high-efficiency devices focussed on the silicon deposition conditions, glass texturing for effective light scattering and light incoupling through anti-reflection coatings. Further research is focused on Transparent Conductive Oxides (TCO) improvements and the creation of triple or quadruple junctions.
Firstly, this thesis will focus on a literature study on amorphous silicon with a high-energy bandgap, deposition conditions in PECVD chambers and an i-SiOx buffer layer. A top cell of amorphous silicon with a high-energy bandgap can improve the conversion efficiency of a-Si:H/nc-Si:H solar cells by increasing its overall V oc. The amorphous silicon is processed at high pressure (3-9mbar) and high power densities (150-400mW /cm2) in a VHF-PECVD chamber at 40.68M Hz. To improve the poor blue response of these solar cells, a buffer layer of i-SiOx is explored as such a buffer layer has proven itself under normal deposition power densities (28mW /cm2) and pressure (0.7mbar).The i-SiOx did not prove to be effective in improving the blue response. A narrow range of deposition conditions around 5mbar and 25W is found to give high-bandgap energy solar cells with a good blue response.
Secondly, literature findings on a bilayer TCO configuration of IOH (Hydrogenated Indium Oxide) and i-ZnO (intrinsic Zinc-Oxide) to improve nc-Si:H single junction solar cells are provided. Prior studies on the use of a back reflector made out of different ZnO(Zinc-Oxides) are presented. Findings in literature on micro and nano-textured glass are presented and a comparison is made in an experiment to justify the use of a specific texture. Further experiments are carried out to measure the effect of implementing the bilayer TCO and an i-ZnO back reflector and an experiment on the performance and reproducibility of a-Si on MST (modulated surface textured) glass substrates is performed. ITO textured glass is chosen as the best performing substrate and a thick 1μ i-ZnO layer as part of a bilayer TCO is shown to be most effective at light scattering. The i-ZnO as part of a bilayer TCO can also significantly improve the spectral response of a-Si:H solar cell on MST textured glass. Furthermore, the i-ZnO as a back reflector is shown to be more effective when its thickness is increased.
Thirdly, a study is performed on the functioning of the a-Si:H/nc-Si:H tandem cells with respect to the thickness of the p-layer in the tunnel recombination junction (TRJ). An experiment is carried out to improve the reproducibility of a-Si:H/nc-Si:H solar cells by increasing the hickness of p-layer in the TRJ.
The conclusion is made that the glass texturing is more influential than the thickness of the p-layer in this experiment. Further investigation of the p-layer at the front interface of the device is done by an experiment on both MST and Asahi substrates. It is shown that thicker front players do not improve the reproducibility of tandem solar cells, but a trend of more parasitic absorption is seen. Finally, a study on micro and nano-textured glass for a-Si:H/nc-Si:H solar cells is shown. The chosen ITO substrate is finally chosen to demonstrate the progress of ongoing research on the performance of a-Si:H/nc-Si:H solar cells. The bilayer TCO vs a single layer TCO is used in combination with and without a SiNx ARC.
The electrical performance of the solar cells deposited in the final experiment is likely limited by poor IOH depositions and a large contribution of parasitic absorption is shown for the samples with the SiNx ARC. Either interaction of SiNx with the IOH or a poor IOH deposition are the most likely causes. Good 1-R curves are obtained for the solar cells on ITO textured glass substrates, especially the sample with the bilayer TCO and SiNx ARC.

This thesis explores the development of mobile charging systems, which could significantly ease the challenges associated with current electric vehicle charging methods. The purpose of this thesis is to develop an autonomous system to fulfil estimated charging demand on a typical day under different conditions to exemplify how mobile charging systems can address these issues.

The research is mainly motivated by the limitations of conventional charging poles, such as their scarcity, lengthy charging times, unregulated demand, and urban space conflicts as EV usage grows. Future EV statistics and charging station projections are presented underscoring how these challenges can be amplified shortly. As an alternative solution, mobile systems are introduced highlighting products, prototypes, and studies in the market and literature. Through stakeholder analysis, these systems are shown to benefit investors, consumers, and the public, supporting the grid, facilitating convenient charging.

The thesis incorporates a charging demand estimation algorithm to simulate the charging tasks on a typical day. This demand estimation is represented as private, public, and workspace charging load, sampled by considering the probability of energy demand and connection times. Next, the study integrates an iterative optimization process to simulate how effectively this demand can be addressed by a robot-like mobile charging system.

The system is simulated with different price scenarios, grid capacity values of 50 and 100 kW, varying the number of units between 3 and 5, and battery sizes between 70 and 400 kWh. As a result, it is demonstrated that mobile charging systems can effectively reduce peak demand by decoupling charging load from the grid while offering more convenient charging experience. The profitability is assessed through energy arbitrage, operational revenues, and energy costs, noting improvements with seasonal effects and higher grid capacity.

The results show that the switchable battery configuration can effectively minimise the required investment costs because of the smaller number of necessary carrier units mobilising the battery units. A switchable battery setup with 3x270 kWh batteries and 2 carriers is identified as cost-effective for public and workplace demand, with a potential increase to 340 kWh for higher returns despite 20% more investment. The sizing process is reiterated for another demand scenario consisting of a private charging load and 260 kWh capacity is highlighted as a cost-effective choice, while the profits can be improved with 310 kWh capacity.

The thesis further discusses the mobility necessities of the system and the performance requirements of the powertrain. To maintain grounding, the study simulates the parking service area of P1 at the TU Delft campus. A driving cycle is developed by taking site measurements and also considering safety concerns and standards. Consequently, energy consumption and maximum power requirement are calculated by also integrating a weight estimation methodology regarding the main components of the system.

Lastly, the thesis introduces different power converter topologies that can act as a bridge between the system and EVs. As a consequence of a comprehensive analysis of different converters and the findings reported in the literature, various topologies are suggested to be used in different cases.