Silicon heterojunction (SHJ) technology is gaining increasing attention due to its lowtemperature and simple fabrication process. Intrinsic hydrogenated amorphous silicon
((i)a-Si:H) serves as a passivation layer, providing excellent chemical passivation, while
doped a-Si:H offers good field passivation and selective contact. Thanks to these features,
SHJ has achieved a high conversion efficiency of 27.09%, approaching the theoretical
limit for silicon-based solar cells. However, achieving excellent passivation performance
results in optical and electrical losses, as the band gap of doped a-Si:H causes parasitic
absorption. One strategy to address this issue is to replace the doped layer with transition
metal oxides (TMOs), which can enable selective contact due to their high or low work
functions. Few researchers have integrated TMOs in silicon-based solar cells to replace
silicon-based doped thin films as selective contact layers. Wide-bandgap TMOs improve
the optical performance of the cells. However, interface reaction between TMOs and the
silicon substrate becomes an issue limiting the electronic properties of the device.

In this research, we first present three different interface engineering methods: no
plasma treatment (noPT), plasma treatment (PT), and plasma treatment with boron
(PTB). We applied these methods to SHJ solar cells with MoOx (2.9 < x < 3) as the hole
transport layer (HTL).MoOx thin-film is deposited by thermal evaporation. The methods
were implemented at theMoOx/(i)a-Si:H interface. Additionally, to address sustainability
concerns related to indium consumption and fully exploit the optical advantages of
MoOx, we propose bifacial SHJ solar cells withMoOx as the HTL to reduce the thickness
indium doped tin oxide (ITO) films. Furthermore, to test the capability of these interface
engineering methods with other TMO materials, we usedWOx (2.9 < x < 3) and V2Ox (2.9
< x < 3) as the hole transport films in SHJ solar cells. The TMO thin-films are deposited by
thermal evaporation. The specific results are summarized as follows.

Chapter 3 explores using MoOx as a HTL to address these issues. By tailoring the
interface betweenMoOx and (i)a-Si:H using interface engineeringmethods, the oxygen
content in MoOx layers has been successfully optimized. The PTB method reduces
the formation of SiOx layer resulting in improved electronic properties and low contact
resistivity. PTB treated samples showed the best performance, with high open-circuit
voltage (VOC) and fill factor (FF). This approach achieved a certified conversion efficiency
of 23.83% with an ultra-thinMoOx layer of 1.7 nm. Notably, a short-circuit current density
(JSC) above 40 mA/cm² has been achieved.

Chapter 4 explores reducing indium consumption by optimizing n-contacts as electron
collector layer andMoOx as a hole collector layer. Bifacial SHJ solar cells withMoOx
as the HTL and various electron transport layers (ETL) were fabricated and optimized
using optical simulations. The results showed that bilayer ((n)nc-Si:H/a-Si:H) and trilayer
((n)nc-SiOx:H/nc-Si:H/a-Si:H) better than monolayer (a-Si:H) in electronic and optical
performance. The use of ultra-thin transparent conductive oxide (TCO) layers combined
withMgF2 as double layer antireflection coatings (DLARC) significantly reduced TCO consumption whilemaintaining high performance. Devices exhibiting 10-nm thick indium
tungsten oxide (IWO) on both side and bilayer n-contact achieved certified efficiencies
of 21.66% and 20.66% when measured from theMoOx and n-contact side, respectively.
This device realizes 90% TCO-reduction. The best-performing bifacial cells exhibited
conversion efficiencies of 23.25% and 22.75% measuring from front and back side, respectively.
The bifaciality factor of the champion device is 0.96. It demonstrates over 67%
reduction in TCO usage compared to traditional SHJ solar cells. This study successfully
shows that reducing TCO thickness and optimizing the interface withMoOx can lead to
high-efficiency bifacial SHJ solar cells, contributing to sustainability challenges related to
indium consumption.

Chapter 5 investigates the application of TMOs likeWOx, and V2Ox as HTLs combined
with interface engineering methods in SHJ solar cells. The study aims to investigate the
applicability of interface engineering methods to other TMOs. X-ray photoelectron
spectroscopy (XPS) is employed to measure oxygen content and defects within TMO films.
The XPS results demonstrate that PTB resulted in higher oxygen content and fewer oxygen
vacancies. The optimal WOx thickness was found to be 2 nm, achieving a champion
cell with 23.30% efficiency with PTB and improved FF of over 80%. Similarly, with PTB
method, the highest efficiency of 22.04% has been realized with 3-nmthick V2Ox layer.
The PTB method effectively controlled interface reactions, leading to better electronic
properties of TMOs. The study concludes that the PTB method offers suitable interface
conditions for depositing TMOs, enhancing SHJ solar cell performance.

Our findings in this study may provide valuable insights into applying TMOs in SHJ
solar cells to achieve high performance. With optimized interface engineeringmethods,
we can significantly reduce the optimal thickness of TMOs and achieve world-record
efficiency. Furthermore, by applying TMOs in bifacial SHJ solar cells, we can decrease the
thickness of indium-based TCOs, realizing both high efficiency and high bifaciality factor.
This approach makes it possible to develop sustainable and efficient solar cells.@en

Power electronics (PE) plays a crucial role in optimizing the performance of photovoltaic (PV) systems. At present, module and sub-module level PE is increasingly being adopted in global PV installations. Typically, PE for sub-module purposes is installed in the PV junction box. However, in this dissertation another approach is investigated: integrating power electronics into or onto crystalline silicon (c-Si) PV cells. This approach has the potential to contribute to the development of shade-tolerant PV modules, increase the reliability of PV module-integrated PE, reduce the volume and weight of the PV system, and support the development of autonomous devices powered by low-power and low-current PV cells. Specifically, the aim of this dissertation is to study the integration of different PE components into c-Si solar cells, and identify the most promising approaches. The dissertation is structured in two parts.

In Part 1, the objective is to gain a comprehensive understanding of the impedance of c-Si solar cells. To this end, Chapter 2 reports a characterization of the impedance of eight single-cell laminates. Each laminate contains a different commercially available c-Si solar cell, featuring various cell architectures, namely Aluminium Back Surface Field (Al-BSF), Passivated Emitter and Rear Contact (PERC), Tunnel Oxide Passivated Contact (TOPCon), Interdigitated Back Contact (IBC), and Silicon Heterojunction (SHJ). It is found that the two main factors contributing to a high PN junction capacitance (C_j) at maximum power point (MPP) are (1) a low wafer dopant concentration and (2) a high MPP voltage. Furthermore, the studied cell laminates exhibit inductances between 63 and 130 nH. Following this, the impedance of PN junctions is further investigated in Chapter 3. Specifically, PN homojunction devices are investigated through Technology Computer-Aided Design (TCAD) simulations. This methodology allows to study the junction impedance in a detailed way, which may be difficult to do experimentally due to noise and reactance of metal contacts. Through analysis of the impedance data it is revealed that the PN junction exhibits the behaviour of a parallel resistor-capacitor circuit (RC-loop) at low frequencies, but undergoes relaxation in both PN junction resistance R_j and capacitance C_j as frequency increases. While various publications on solar-cell impedance model the low-high (LH) junction using an RC-loop, the findings presented in this chapter indicate that such a model does not accurately represent the underlying physics. Instead, this approach is likely compensating for the frequency-dependent behavior of R_j and C_j. Finally, in Chapter 4, the PN junction impedance of modern c-Si solar cells is studied across varying temperature and illumination conditions. In the tested conditions, the range in which the area-specific MPP R_j varies is similar for different cell architectures, despite their different properties. Conversely, the range in which the areal MPP C_j varies is significantly affected by the substrate dopant concentration and MPP voltage of the cell.

In Part 2, the aim is to assess the feasibility of leveraging solar-cell impedance at the input of a power converter, and to explore various methods for integrating additional PE components into solar cells. In Chapter 5, the feasibility of integrating different PE components into c-Si solar cells is explored. First of all, diodes exhibit high ease of integration into PV cells and successfully integrated designs have already been demonstrated in prior work. Alternatively, the integration of transistors is more complex. Since transistor fabrication processes require lithographic steps, it is necessary for cost-effective integration to combine as many processing steps as possible with PV fabrication. Regarding passive component integration, it is found that the self-capacitance of modern c-Si solar cells is sufficiently large to replace the input capacitor of an exemplary boost converter. However, for thin-film capacitor integration, it is challenging to achieve a sufficiently high areal capacitance. Moreover, the self-inductance of a solar-cell string could potentially be leveraged to replace the inductor at the input of a power converter. By analyzing this approach for an exemplary boost converter, it was found that high switching frequencies in the MHz range are required. Alternatively, the required switching frequency may be reduced through the integration of planar inductors. It was found that the area of PV cells is sufficiently large to facilitate the integration of planar coils exhibiting inductance values that are useful for power conversion. Finally, general challenges that should be considered for successful PE-PV integration are appropriate thermal management, opto-electric behaviour under illumination, and repairability. The inductor integration is further studied in Chapter 6. Specifically, it is explored whether large-area planar air-core inductors can yield the required inductor properties to support sub-module power conversion in PV modules. First, it is shown how the interplay between the different design parameters, such as track spacing, track width, number of turns, and middle gap size, play an important role in the inductor properties. This analysis includes changes due to high-frequency effects, which significantly impact the results. The coil geometries that are simulated yield inductance values between 0.3 and 3.2 μH. Considering the power losses, the applicability of such inductors in sub-module power converters is discussed. Finally, in Chapter 7, the concept of COSMOS (COmbined Solar cell and MOSFET) devices is introduced and a process flow is proposed in which back-contact TOPCon solar cells and lateral power MOSFETs are simultaneously fabricated on a single substrate. This process is successfully employed to manufacture both n-type solar cells with integrated p-channel MOSFETs (PMOS) and p-type solar cells with integrated n-channel MOSFETs (NMOS). Notably, efficiencies exceeding 20% are achieved for both n-type and p-type solar cells, highlighting the potential of COSMOS solar cells. Furthermore, two main integration challenges are identified. Firstly, the off-state leakage currents of the MOSFETs increase due to illumination. Secondly, specific topologies of monolithic integration lead to increased off-state leakage currents.@en

Photovoltaics will play a pivotal role in achieving a low-carbon-emission society. Remarkable advancements in the efficiency of crystalline Si (c-Si) solar cells, combined with standardized processes along the whole value chain, have enabled cost-competitive solar electricity production. In order to further decrease the cost of photovoltaic, significant efforts must be dedicated to further enhancing the efficiency of solar cells. The implementation passivating and carrier-selective contacts in recent years has led to a remarkable increase in the conversion efficiency of c-Si solar cells. Solar cells, such as silicon heterojunction (SHJ) and poly-Si/SiOx-based technologies are prime examples of the efficacy of these contacts, as cell efficiencies above 26% have been demonstrated. These achievements can be attributed to the excellent surface passivation properties of the intrinsic amorphous hydrogenated silicon (a-Si:H(i )) and the ultra-thin SiOx interlayers, coupled with the high carrier-selectivity exhibited by the doped Si-based layers. However, a significant limitation associated with these passivating and carrier-selective contacts is related to their optical parasitic absorption losses within the layers. These losses stem from the free-carrier absorption in a-Si:H layers of SHJ solar cells and poly-Si layers, which possess relatively narrow bandgaps, making them prone to absorbing the ultraviolet (UV) portion of sunlight. Consequently, these parasitic absorption losses diminish the amount of light reaching the c-Si absorber, ultimately restricting the short-circuit current (J sc) output of the solar cell. To mitigate these losses, wide-bandgap metal oxide layers, such as MoOx and TiOx, have been proposed as promising alternatives to replace these highly doped Si-based contacts. These metal oxides possess distinct carrier-selective characteristics, primarily due to their differences in work function (WF) with respect to the c-Si, leading to induced band bending within the absorber. Despite significant progress in recent years, several challenges still exist, as metal oxide contacts often suffer from carrier-selectivity issues due to material instability and interface reactions with adjacent layers. This thesis explores several possible strategies to minimize the parasitic absorption losses in passivating and carrier-selective contacts. A considerable portion of the research is devoted to understanding and enhancing the contact properties of the MoOx layer. The focus on MoOx is driven by the challenges it faces with carrier-selectivity, stemming from its low thermal stability and its susceptibility to band alignment issues when combined with various passivating interlayers. An innovative MoOx contact is introduced, incorporating ultra-thin surface passivating interlayers based on Al2O3 films. These ultra-thin interlayers offer substantial advantages, including enhanced surface passivation, minimal parasitic absorption, and improved transport of majority carriers. Additionally, MoOx and TiOx contacts, deposited by pulsed laser deposition (PLD) are also explored for c-Si solar cells...@en

Hydrogen is not only the most common element in the universe, but also a versatile molecule which is an option to decarbonize sectors that are not easily electrified or are energy intensive, such as long-distance transport, chemical industry, and metallurgy among others. Hydrogen gas is typically obtained from fossil fuels, and only a small fraction is produced nowadays from electrolysis, or the process of using water and electricity to produce gaseous hydrogen.
If the electricity for powering the electrolysis process comes from renewable sources, the produced gas will have no associated greenhouse emissions. This is the so-called green hydrogen, which is the base for decarbonization of carbon intensive industries. This work investigates the potential of stand-alone green hydrogen production from solar energy, covering the whole design process, from an allocation and feasibility analysis, to system control. To do so, this thesis is separated in two parts. The first part focuses on the preliminary assessment phase of photovoltaic (PV) systems and the solar resource, while the second covers the integration of PV and electrolysis systems finalizing with a control strategy for these systems.
Chapter 2 presents a methodology for analyzing potential sites for PV deployment, including information on the degradation of the site. This provides the designer with additional information beyond the purely technical and economical layers that are typically considered in this type of study. The more degraded a site is, the more suitable it is for deploying new PV projects, avoiding pristine natural areas. This, combined with mitigation measures can minimize the environmental impact of new PV projects.
An analysis of the efficiency loss of PV systems is discussed in Chapter 3. In particular, the efficiency loss caused exclusively by quick variations in irradiance, as a consequence of passing clouds. These abrupt and quick changes affect not only the solar modules, but components downstream, such as the maximum power point tracker. The implemented algorithm might be sensitive to these changes and move the operating point of the PV module away from its maximum power point, leading to energy loss.
Predicting quick changes of irradiance is a topic covered in Chapter 4. Using sky images and artificial intelligence, it is possible to predict ultra-short-term irradiance. The proposed method is an ensemble of models, each trained on a particular sky condition. Because each model is highly specialized, once the sky condition is determined, the model that performs best on each sky type is employed, leading to lower prediction errors, more precise predictions and lower training data needed. Yet, an accurate prediction is a topic for further research.
The integration of PV with hydrogen systems is introduced in Chapter 5, which presents a literature review on integration methods for PV and electrolyzers as well as the main challenges for operating these systems in a variable manner.
Moving to the design phase, Chapter 6 proposes a sizing procedure, based on Particle Swarm Optimization to minimize the energy that cannot be used by the hydrogen equipment (electrolyzer and compressor), aiming at the maximum energy utilization in the system. Horizontally-placed PV modules provide a good compromise between efficiency, hydrogen production and cost.
Once the system has been designed, Chapter 7 puts together all the topics covered in this dissertation proposing a control strategy for an optimally-sized stand-alone PV electrolyzer systems, without electrical storage. The control is based on prediction of irradaince changes using sky-images. From Chapter 4 it was clear that the prediction using sky images is far from perfect, yet this is needed for control. To solve this problem, the strategy proposed in Chapter 7 relies on information on the uncertainty of the prediction and uses fuzzy logic to account for imperfect predictions. This strategy can effectively smooth power changes without the need of additional storage components.@en

Large-scale deployment of photovoltaic (PV) technology is imperative for realizing a future sustainable and electrified energy system. Over the past decades, technological advancements that enhance the efficiency of PV technologies have been one of the crucial aspects for significantly reducing the cost of PV-generated electricity. Among various crystalline silicon (c-Si) PV technologies, silicon heterojunction (SHJ) solar cells, which have achieved the highest efficiency of single-junction c-Si solar cells, hold great promise for advancing the energy transition facilitated by PV technologies even further. Moreover, notable efficiency enhancements, which are well beyond the theoretical efficiency limit of single-junction c-Si solar cells, have been experimentally demonstrated by combining SHJ solar cells with semi-transparent perovskite solar cells in tandem configurations. This thesis focuses on addressing the challenges of efficient deployments of doped hydrogenated nanocrystalline silicon-based (nc-Si:H-based) layers for high-efficiency front/back-contacted (FBC) SHJ solar cells and applications of FBC-SHJ bottom-cells in two-terminal (2T) and four-terminal (4T) tandem devices with perovskite top-cells, supported by advanced opto-electrical simulations.@en

Solar photovoltaic cells are destined to become an important contributor in the renewable energy sector, also for small electrical systems inside buildings. They can be used to mobilise the electrical infrastructure, by providing an independent energy source for medium-consumption products, like decorative lighting. This thesis shows all aspects of designing and building an interior, solar powered lamp. First, the ideal position for indoor light harvesting has been investigated extensively, by recreating two typical Dutch rooms with 3D modelling software Blender. The light simulation tool RADIANCE was then used to compute the irradiance at various spots in the room, considering three standard sky types. Weather data from the KNMI was used to classify the sky conditions for every hour during two weeks in November, and the results were compared with pyranometer measurements, showing an error of 20% on a daily basis, and 5% over a five day period. The same simulation method was applied to predict the PV energy yield of four common solar cell technologies for a full year, for multiple room orientations and positions on a wall. Based on these results, three concepts were designed, corresponding to three specific room positions with different indoor light characteristics. Ultimately, one concept was chosen to be build as a prototype, with tailor-made, foil-to-foil laminated PV module, consisting of laser cut SunPower interdigitated back contact (IBC) cell technology. At standard test conditions, the measured short-circuit current was 2.37 A, with an open-circuit voltage of 21.5 V and a maximum power point of 35.9 W_p, resulting in an efficiency of 20.3%. Furthermore, a charge controller with maximum power point tracking algorithm was used to charge a 12V polymer lithium-ion battery pack. The combination of pyroelectric infrared (PIR) motion sensor detector and a light sensor module assures a conservative use of a 2.4 W strip of light emitting diodes (LED).

Building Integrated Photovoltaics (BIPV) has the potential to play a major role in the ongoing transition towards nearly zero energy buildings. However, the BIPV market is still a niche market, representing only 1% of the global PV share. One of the main barriers that hinder the deployment of BIPV is the lack of aesthetic flexibility. Architects and designers are often reluctant to embed PV systems in buildings due to their unsuitable color.
In this thesis, the use of interference filters (IFs) as color coating solution for PV modules is proposed. IFs are optical devices designed to selectively reflect a narrow portion of the visible solar spectrum while transmitting the remaining part. The structural coloration provided by the filter is highly dependent on the angle of incidence of the light. This angular dependence could be an issue for BIPV applications, since color homogeneity is often an important requirement. The objective of this work is to model, fabricate and assess the opto-electrical performance of colored crystalline silicon (c-Si) PV modules based on interference filters, with the final goal of increasing the aesthetics of this technology.
First, the angular resilience challenge is addressed. Simulation results show that texturing the glass surface significantly improves the color stability, thanks to diffuse reflection of light. Very high angular resilience up to 80º can be achieved with a double-side texture profile made of hemispherical grooves. Secondly, five interference filters deposited on different glass substrates are used to fabricate 10 x 10 cm² c-Si colored mini-modules. The optical characterization of the demonstrators
allows to partially validate the optical model and confirm the good angular resilience of the textured surfaces. Finally, the electrical performance of the mini-modules is evaluated. I-V measurements show that IFs only affect the short-circuit current of the mini-modules due to optical losses. Depending on the color and the topology of the surface, absolute efficiency losses range from 0,95% to 4,6%.

Bifacial PV modules and floating PV systems are two fast-growing technologies in the photovoltaic sector. Bifacial PV modules make use of the irradiance that is incident on both faces of the module, leading to higher energy yields. Several techniques are used in order to enhance this bifaciality effect, one of them being the use of reflectors. On the other hand, floating PV systems offer multiple advantages with respect to conventional in-land PV systems such as land saving (a big issue for vastly populated areas), higher efficiencies and lower water evaporation rates. The advantages that these technologies provide as well as the big market opportunities that they offer, make them very attractive for new investors.
The uncertainties related to floating PV and bifacial modules are higher compared to conventional power plants. In order to minimize these uncertainties, accurate modelling tools are essential. The most widespread software suites such as PVSyst or System Advisor Model, offer limited flexibility to the user. Therefore, the user is not able to adapt the simulation to very specific cases such as the addition of reflectors to the system. Additionally, they perform simulations only at module level, without performing an analysis at cell level.
Aiming to fill this gap, a Toolbox that is able to model and simulate the annual energy yield of a PV module, considering the physical effects from cell to module level, was developed by the Pho- tovoltaic Devices and Materials group of TU Delft. This Toolbox allows the integration of the work done by different members of the group and it offers great simulation flexibility to the user. The goal of this thesis is to continue the work carried out by former PVMD members and create a new and improved version of the Toolbox.
During this thesis project, several improvements were carried out in the optical models of the Tool- box. Multiple mistakes were discovered and corrected, and new features that improve the Toolbox were added, making it suitable for its use in real projects. Besides that, the thermal part has been improved by adding the option to utilize a thermal model developed in COMSOL Multiphysics that allows to study the temperature distribution in a bifacial PV module. Finally, the Toolbox was ap- plied to the INNOZOWA project, where several simulations were carried out to find the ideal design of a floating PV plant that consists of bifacial PV modules and reflectors. It was found that the chosen design for this type of system can provide a bifacial gain of 18%.

Electric vehicles are only sustainable if the electricity used to charge them comes from renewable sources and not from fossil fuel based power plants. The goal of this PhD thesis is to develop a highly efficient, V2G-enabled smart charging system for electric vehicles at workplaces, that is powered by solar energy. The thesis focusses on three research elements – power converter, charging algorithms and system design.  A 10kW EV charger has been developed that enables the direct DC charging of EV from PV without converting to AC. The charger is bidirectional, so energy from the EV battery can also be fed to the grid for vehicle to grid (V2G). The charger can realize four different power flows: PV → EV, EV → Grid, Grid → EV, PV → Grid. The 10kW modules are modularly built and can be operated without solar input as a bidirectional EV charger as well. Further, several DC charger modules can be operated paralleled for fast charging up to 150kW. The charger is based on silicon carbide and quasi-resonant technology which results in high efficiency (>96%) for both full load and partial load. The integrated EV-PV solution has a lower component count, three times higher power density and lower cost than using separate EV charger and PV inverter exchanging power over AC. The charger is compatible with the CHAdeMO and CCS/Combo charging standard and is designed for implementing smart charging. New smart charging algorithms developed in the project integrate several applications together: PV forecast, EV user preferences, multiplexing of EVs, V2G demand, energy prices, regulation prices and distribution network constraints. For two case studies simulated for Netherlands and Texas, the proposed algorithms reduced the net costs by up to 427% and 651% when compared to average rate charging, respectively.

@en

Low powered electric vehicles and electricity generation with the help of renewable energy technology are two kind of technological advancements which are taking place to meet growing global energy demand while reducing greenhouse gas emissions together at the same time. Achieving these objectives indicate shift from energy demand followed by fossil fuels to renewables. Renewable energy technology and plug-in vehicle electrification adoption have substantial problems associated with it, however there are ways to exploit their potential in order to develop sustainability in the field of electricity and transportation.

This thesis aims at designing the Roadside Photovoltaic (PV) system that act as a major supply of electrical power to charge Electric Bikes (E-bikes). The expansion and rapid growth in E-bikes is tremendous in the Netherlands, therefore the charging of E-bikes is chosen as an application to build the Roadside PV system for campus located at Mekelweg, Delft. The E-bike dynamic consumption is modelled to calculate the driving efficiency of an E-bike, and thus this model is used to compute the state of charge of incoming E-bikes in order to determine the daily consumption of charging station. Furthermore, for maximizing the energy yield of the PV system, the optimal orientation of module is analysed. The mounting and placement of these optimally oriented modules beside the road is decided such that the overall effect of shading is minimal. Moreover, as it is a Roadside PV, the system is compared with the solar road technology to see the difference of how the system behaves when placed optimally beside the roads on poles instead horizontally on roads. Finally, performance of entire grid-tied Roadside PV system with storage is determined according to chosen application.

Among the advantages of crystalline silicon hetero-junction (SHJ) there is the possibility to use a thin c-Si wafer that is bendable, but still has a power conversion efficiency higher than commercially avail- able thin film (TF) modules. Nowadays, all the photovoltaic applications on curved surfaces use TF technologies, however their low power conversion efficiency requires a large area, which is not always available. Therefore, the entry of SHJ technology in the environment-integrated applications will de- crease the required PV area being a competitor of TF wherever the surface available is scarce and the the shape curved and not complex.

A structure that would benefit the advent of SHJ modules is the infotainment spot, which is a solar- powered device that provides useful information and entertainment to the user through an interactive screen. Such a device was realized for the first time by Weeda et al. [1] in TUDelft, but the CIGS module that powered the device made the structure bulky, unattractive and unwieldy. In this thesis the experience of Kaneka Corp., which holds the world’s record of highest conversion efficiency for c-Si hetero-junction, was used to design the PV module that powers the stand-alone system of a new infotainment spot.

In order to calculate the irradiation on the surface of the infotainment spot the Optical Model developed by Santbergen et al. [2] was used because allows flexibility in choosing the design and the location separately. However, this model does not include the surrounding, thus in this thesis three new ap- proaches to include the influence of the surrounding environment were proposed and validated through experimental measurements. Moreover, two of these new approaches have the possibility to study the irradiance also in indoor places. After that, its power was simulated knowing the irradiance values, the temperature of the PV module, computed with a thermal-energy balance, and other meteorological data. Lastly, a load profile was developed to simulate the system performance throughout the year. All these information served to find the best pair of number of SHJ cells to interconnect and battery capacity and basically it is a trade-off between system reliability and system size. The study indicated that in Osaka the infotainment spot would need 42 series connected half-cut solar cells that power a 12 푉 system with a storage capacity of 150 퐴ℎ in order to make the system completely autonomous and operable the whole year. The thesis ended with a working prototype of the Solar-Powered Infotainment Spot 2.0.

The goal of this master thesis was to optimize the tunnel oxide passivating contact (TOPCon) concept for p-type substrates and implementation in silicon (Si) solar cells. TOPCon and other passivating contacts are believed to be a crucial link for increasing solar cell efficiency and further reducing the costs of photovoltaic (PV) systems. The concept that comes closest to the theoretical Auger limit is the Si heterojunction cell with a record efficiency of 26.6%[1]. A problem with this type of cells is that the process temperature that is allowed is limited, increasing the processing temperature results in decreasing passivation and thus loss of efficiency. The TOPCon concept can withstand higher processing temperatures, which is beneficial when it comes to applying a transparent conductive oxide (TCO) layer of certain metallization schemes. For n-TOPCon good results have been obtained in the past leading to a record efficiency of 25.7%[2]. For p-TOPCon, the efficiency is significantly lower and the cause of this discrepancy is not fully understood yet. In this work, the boron doped TOPCon configuration was optimized by optimizing all of the individual components of this passivating contact concept. During this work the tunnel oxide, which can be grown using variousmethods, proved essential to obtain a good passivation. A comparison was made between four different growth methods for the tunnel oxide, from which it was concluded that the thermally grown tunnel oxide performed best in terms of passivation quality and thermal stability. The optimal p-TOPCon stack was found to consist of three layers: a thin intrinsic hydrogenated amorphous silicon (a-Si:H) layer, followed by a boron doped a-Si:H layer. The p-TOPCon stack is finalized by depositing a thin silicon carbide (SiC) capping layer, which was also boron doped. Besides passivation, the specific contact resistivity was also investigated. A metallization stack consisting of titanium, palladium, and silver proved to result in the lowest contact resistivity values. The lowest value which was measured was 10 m­cm2, this is below the threshold value for which fill factor (FF) losses are to be expected. Implementing a thin tungsten oxide (WOx) layer underneath this metallization stack resulted in a stark increase in the specific contact resistivity values. Furthermore, the tunnel oxide influenced the contact resistivity values, where a lower oxidation time and temperature resulted in lower contact resistivity values. In order to better understand the correlation between contact resistivity and passivation, the contact resistivity values and corresponding recombination current values were fitted to two different models: the oxide tunneling model [3] and the pinholes model [4]. The measured resistivity values all laid in the saturated regime, whichmade it difficult to exclude one of the two models. The passivation quality of the p-TOPCon stack was improved by altering the tunnel oxide to a thermally grown oxide and optimizing the TOPCon stack. This resulted in an implied open-circuit voltage (iVoc) value of 710 mV and an implied fill factor (iFF) value of 84.5 %. A good contact was obtained with a titanium, palladium, silver metallization. This resulted in a specific contact resistivity value of 10m­cm2.