For centuries, society has relied on fossil fuels for development, leading to the problem of global warming and significant environmental changes. To address these environmental issues, cleaner and more cost-effective energy productions are required. Solar energy, harnessed through well-developed photovoltaic (PV) technology, offers a promising solution. In the PV research field, perovskite (PVK)-based devices offer a feasible processing and have exhibited a fast increase in efficiency. Despite advancements in both the efficiency and stability of perovskite solar cells, there still is a long way to go towards industrialization due to the formation of pinholes during large area film deposition, nonuniformity, and poor reproducibility. Thermal evaporation technology has shown potential for the commercialization of perovskite solar cells, owing to its compatibility with large areas and textured substrates. In this thesis, we focused on the sequential thermal evaporation of perovskite. Through this approach, post-annealing and precursor mixing processes were investigated. Additionally, crystal orientation was tuned by applying different intermediate annealing temperatures. The optimized process was then applied to upscale both absorber films and cells from 0.09 cm2 to 1 cm2...

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.

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.

Solar photovoltaic (PV) energy has the potential to become a major source of electricity production worldwide. However, the deployment of this renewable energy source comes with several challenges. Besides societal, political, and grid-limiting, several technical limitations decrease the trust in this technology. Within this context arises the Trust-PV project, whose objective is to improve the performance and reliability of photovoltaic systems.

This work contributes to this European project by exploring different power prediction models for several types of PV systems. Considering the broadness of the topic, four parts or blocks are identified. The first part deals with machine learning models to forecast the yield of residential PV systems. The second block focuses on analytical models used during the design phase. The third part is dedicated to systems floating on water. Lastly, a metric to assess the tolerance towards shading of different modules is developed in the fourth block.

Starting with the first block of machine learning techniques for PV power forecasting, Chapter 2 introduces the topic by reviewing a large number of manuscripts. The chapter performs a broad classification of the reviewed literature with the objective to identify trends and gaps in the field. Among the identified trends, one can highlight the high percentage of predictions for the day ahead, the generally low number of systems employed to train the models, and the concentration of systems in mild climates.

The latter points may stem from researchers primarily using the systems available within their institutions. To promote collaboration, Chapter 3 presents a developed website that lists PV power open source databases. The website aims to encourage researchers to train and test their models with different data sources.

One consequence of the concentration of systems in mild climates is that the effect of climate on machine learning models remains underexplored in the literature. Chapter 4 addresses this gap by studying how machine learning models behave for systems located in different climatic zones. The results show that weather homogeneity affects the accuracy of the models. Models developed for systems located in uniform climates - like desert areas - achieve in general higher accuracy than the models developed for systems in highly varying climates - like tropical areas.

Chapter 5 addresses another challenge: creating a single machine learning model able to monitor the performance of a large fleet of residential PV systems. The developed model surpasses in accuracy an analytical reference model but is limited by a fundamental characteristic of machine learning methods: the focus on large errors which resulted in the overlooking of smaller systems. Consequently, Chapter 6 develops a different approach based on the peer-to-peer methodology. In this approach, the power output of similar neighboring systems is compared to identify any malfunctions. The method is tested for the residential fleet of PV systems and proves effective for detecting faults.

Moving on to the second block of analytical power predictions, Chapter 7 presents the PVMD toolbox, a state-of-the-art analytical simulation framework that can predict the power of systems that do not exist yet. The abilities of the toolbox are tested for residential systems in the same chapter and the results show the negative influence that inaccurate input irradiance data has on the predictions.

This importance of accurate irradiance data affects all kinds of PV systems, but especially large-scale ones. Therefore, to monitor them, a proper allocation of irradiance sensors is essential. Hence, in Chapter 8, a software tool is developed to identify the optimal number of irradiance sensors and their position in a PV farm. The tool’s strengths are more prominent in plants located on terrains with significant elevation changes.

The third block focuses on PV systems that are installed on floating platforms rather than on land. Chapter 9 introduces the topic by examining three factors influenced by proximity to water that can impact the production of a floating PV system in a French quarry lake: movement fluctuations, dust accumulation, and module temperature. The results reveal a limited influence of all factors on the production for the period of study therefore facilitating the deployment of floating systems.

The block continues by studying the effect of sea waves for a system located in the North Sea. The simulation results from Chapter 10 reveal that wave fluctuations can have a negative yet limited effect on the DC and AC yield of floating PV systems. These results are further elaborated in Chapter 11, where the model is improved by considering the fluid-structure interaction. This advanced model enables to study the effect of various platform characteristics on the power mismatch losses. The results reveal a trade-off between mechanical stability and mismatch losses.

Finally, the last part deals with the power lost when a PV module is partially shaded. Chapter 12 develops a simulation tool to efficiently calculate the shading tolerability of a PV module given its datasheet. The shading tolerability is a metric that quantifies the resilience towards shading of a PV module, that is how much power is lost when the module is partially shaded. The developed tool is used to create a database of shading tolerability of commercial PV modules, to compare the resilience of different modules towards shading.

Due to increasing population growth and industrialization, the energy demand is soaring around the world. In order to meet this energy demand and continuing with business as usual, there is an increased need for fossil fuels. Burning of fossil fuels such as coal, gas and oil lead to emission of carbon dioxide in atmosphere. Emission of carbon dioxide rises the earth’s surface temperature and is leading to global warming. In order to tackle this crisis, an alternative to fossil fuels need to be investigated. In this regard, renewable energy sources are key as they can be replenished. Solar energy is one of the fastest growing and promising renewable energy sources.

Photovoltaics (PV) modules or solar panels have been installed across the world, converting solar energy into electrical energy. The PV market is dominated by single junction crystalline silicon (c-Si) solar cells. In order to improve the efficiency of single junction solar cells beyond their efficiency limit, tandemsolar cells, which stack one solar cell on top of another, are being actively explored by researchers. In this work, we have focused on perovskite/c-Si tandem solar cells.

Since direct contact of metal with semiconductor leads to recombination, the concept of carrier-selective passivating contacts (CSPCs), which separates the absorber from the metal by a thin passivating layer, becomes important. The most common type of CSPCs are doped hydrogenated amorphous silicon (a-Si:H) on intrinsic amorphous silicon, as in the case of silicon heterojunction (SHJ) solar cells. The other type of CSPCs are polycrystalline silicon (poly-Si) on ultrathin silicon oxide (SiOx) as in the case of poly-Si solar cells. Depending on the fabrication temperature of CSPCs, the former comes under low temperature CSPCs while the latter is a type of high temperature CSPCs. While low temperature CSPCs have been successfully integrated in perovskite/c-Si tandem solar cells, research involving high temperature CSPCs is less developed. In this work, high temperature CSPCs are studied, optimized and integrated in perovskite/c-Si tandem solar cells. In addition, the performance of tandem solar cells is evaluated not only in terms of efficiency but also energy yield which is more relevant for outdoor environment. In addition to poly-Si, this work explores novel materials such as polycrystalline silicon oxide (poly-SiOx) and polycrystalline silicon carbide (poly- SiCx) as high temperature CSPCs...

With an estimated global share of greenhouseemissions of 35%, the building sectormust be the target of significant transformation. These next decades represent one of the best opportunities for a giant energy consumer to become an efficient energy prosumer. Of the many technical possibilities available that can help in this objective, building integrated photovoltaic systems is becoming one of the most salient because of their versatility of application and simplicity of operation. However, to achieve their projected market growth, BIPV products must overcome technical, financial, and social barriers.

The interrelationship between these barriers creates requirements that are sometimes in conflict with each other. Research suggests that the most important parameters for the financial viability of a BIPV system (studied in North America) are its electrical performance and its effective lifetime. However, the social acceptance of BIPV systems, among architects and other consumers, increases when photovoltaic modules are provided with a variety of colors, resulting in losses in their electrical output. Furthermore, a BIPV system can present an installation layout in which its modules operate at high values of temperature, which hinders their useful lifetime.

Significant research has been done to tackle these requirements, striving to find a balance in which each, however contradictory, is met. This thesis seeks to add to this body of research through modeling and experimental efforts focused on creating techniques and concepts to improve the aesthetics and thermal behavior of photovoltaic modules.

After an introductory chapter, Chapter 2 presents an overview of the efforts done so far to improve aesthetics and passively cool photovoltaic modules. The challenges and barriers that remain from a technical perspective are outlined, and the base modeling approach deployed to tackle them is introduced. Chapter 3 presents how this model can be complemented by auxiliary algorithms to find ways to provide color directly to c-Si solar cells by using interference optical filters. The chapter also provides insight into ways of stabilizing color and the beneficial impact that a color optical filter has on the operating temperature of a c-Si solar cell.

Chapter 4 expands on the findings of Chapter 3 and discusses that the application of the color optical filter on the front glass of a PV module provides better benefits, particularly in terms of better color saturation and more vivid hues. In addition, it provides guidelines for how colorimetry can be added to the modeling effort to improve the quality of color matching and color stability of a color photovoltaic module based on optical filters. Furthermore it demonstrates that it is possible to achieve colorful designs with relative DC energy losses below 10%.

Chapter 5 argues that optical filters can also be designed to provide thermal control to photovoltaic modules. Furthermore, this thermal control can be achieved by taking advantage of the harmonic reflectance produced by simple designs. It shows that the analysis of a thermal management solution must always consider their benefits related to extended lifetime. A simple optical thermal filter, despite its lossy nature (in terms of electrical output), can still provide a net benefit in terms of energy yield when this benefit is accounted for.

Chapter 6 presents the huge cooling potential provided by phase change material (PCM). This work is entirely experimental and demonstrates that a single type of PCM can be used in different locations, with different installation layouts, to provide substantial temperature reductions and increase the electrical output of photovoltaic modules with great consistency, even during the wintermonths.

Chapter 7 presents the novel concept of a photovoltaic chimney, developed with the purpose of studying the potential use of the thermal energy produced by photovoltaic modules. The concept was analyzed using common modeling approaches to calculate mass flow and heat production, offering quick ways to create sensitivity analysis for earlier stages of design. These initial stages of the model can be used to have insight into the quality (or lack thereof) of the heat produced and its potential use to improve the ventilation of buildings.

Chapter 8 completes this dissertation, highlighting its main conclusions and providing details on potential areas that can drive future research.

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.

The installed capacity of photovoltaic (PV) technology has increased beyond expectations and is expected to grow even more. One of the most promising PV technologies currently dominating the PV market is the silicon heterojunction (SHJ) solar cells, which hold the highest c-Si single junction efficiency of 27.3% in an interdigitated-back-contacted design. To achieve such high efficiencies, an optimized (i)a-Si:H passivation layer is of great importance. This thesis aims to scale up the lab baseline SHJ technology by optimizing large-area c-Si surface passivation with hydrogenated intrinsic amorphous silicon (i)a-Si:H layers. In view of the development of high-efficiency perovskite/c-Si tandem solar cells, this thesis also covers the development of nanotexture on crystalline silicon (c-Si) wafers used for the bottom cells.
The research for optimization of large-area c-Si passivation with (i)a-Si:H layers first started with obtaining recipes that would deposit uniform (i)a-Si:H layers over M2-sized glasses. The deposition conditions of plasma-enhanced chemical vapor deposition (PECVD) were optimized and various promising recipes that delivered highly uniform (i)a-Si:H layers were obtained. No statistically significant correlation was found between the deposition parameters and the uniformity of the (i)a-Si:H layers.
The passivation quality of the (i)a-Si:H layers was assessed by symmetrically depositing the (i)a-Si:H layers on c-Si wafers and measuring the lifetime. For single-layer passivation strategy, (i)a-Si:H layers prepared with the highly hydrogen-diluted silane (SiH4) resulted in relatively low lifetime values, potentially due to epitaxial growth, while layers deposited with less hydrogen-diluted SiH4 or pure SiH4 resulted in better lifetime values. The best lifetime achieved with single-layer passivation was 8.23 ms. Furthermore, utilizing a bilayer concept that first deposits an ultra-thin (i)a-Si:H layer with pure SiH4 and then stacks on its top a highly hydrogen-diluted (i)a-Si:H layer, can enhance the passivation quality over their single-layer counterparts. With proper selection of the (i)a-Si:H layers that compose the bilayer and the optimum thickness combinations, a lifetime of 16.10 ms was achieved. Moreover, the passivation quality can be further boosted by applying a hydrogen plasma treatment (HPT) of 30 seconds on top of the optimized bilayer. HPT durations longer than 30 seconds resulted in a decrease in lifetime, possibly due to the oversaturation of hydrogen that leads to defect formation. A lifetime as high as 21.53 ms was obtained by combing the bilayer approach and a HPT.
Last but not least, the creation of nanotexture on c-Si wafers was done by anisotropic etching, using KOH, KsSiO3, and surface additive monoTEX 2.6. By varying texturing conditions, namely, temperature and duration, various surface morphologies of c-Si wafers were obtained. According to SEM characterizations, pyramidal features below 1 μm were successfully created mainly thanks to K2SiO3 slowing down the etching rate during the texturing process. The lowest reflectance was obtained by etching the c-Si wafers at 70 °C for 20 minutes. It was also found that K2SiO3 has an extremely slow dissolving rate and the most effective way of dissolving K2SiO3 is by adding KOH and K2SiO3 to DI water at room temperature and heating it to 80 °C while mixing.

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.

Global warming is currently being regarded as one of the most significant concerns in society. As globalnwarming is related to the greenhouse gases emitted from the current energy supply, there is a needbfor renewable energy sources. Solar energy is an energy source which has zero emissions and could
in theory supply the energy demand. A solar cell is technology based on the photovoltaic effect, it converts solar irradiance, specifically the energy derived from photons, into electrical energy. Over the course of the development of photovoltaic technology, numerous variations of solar cells have been introduced. By IRTPV, it is anticipated that new and advanced concepts, especially the Tunnel Oxide Passivating Contact (TOPCon) solar cell, will come to dominate the solar market in the coming years. At ISCKonstanz, the primary objective is to develop solar cells that are feasible for industrial applications.
The solar cell under investigation and exploration within the context of this particular thesis is referred to as TOPCon Rear Junction (TOPCon RJ), it differs from the well-documented TOPCon emitter Front Junction (FJ). The notable advantage lies in the fact that by placing the emitter at the RJ, the FSF can be
lightly doped, thereby reducing Auger recombination. Another advantage is the possibility of increasing the metal pitch between the fingers, reducing the metal used. Even more, the TOPCon RJ doesn’t need the high temperature boron diffusion needed for TOPCon FJ, because of doping during APCVD deposition. Simulation results indicate that TOPCon RJ can achieve at least the same
efficiency as TOPCon FJ. The TOPCon solar cell is developed on large area n-type Cz wafers, with a selective n++/n+ FSF of c-Si, a by APCVD inline deposited p+ poly-Si layer and screen printed silver contacts. The inline APCVD has fast processing as a major advantage. A comprehensive description of the TOPCon RJ solar cell structure will be provided. The solar cell’s parameters will be elaborated on, in order to characterize it. The report incorporates basic supportive solar physics. Various characterization methods will be expounded upon to offer a more comprehensive understanding of the research methodology. The research is divided into three parts: the development of the p+ poly-Si rear layer, the development of the n+ c-Si FSF, and the process of metallization. Good passivation for the individual layers were achieved and good contacting as well. However, viable cell results were not yet obtained. The research necessitates substantial further enhancements. Moreover, the presence of defects and damages significantly impacted the outcomes, lowering the reliability.

Climate change is real. Energy transition plays a crucial role in addressing climate change where solar fuels have emerged as a critical player in reducing the dependence on fossil fuels in industries that cannot transition into renewable electricity as an energy source such as aviation, industrial feedstocks etc. Green methanol is a promising solar fuel if it is sourced via carbon capture technologies. This thesis aims to build and use a model of an integrated methanol synthesis microplant as a tool to predict methanol production and the performance of the microplant under multiple system architectures at Zero Emission Fuels B.V (ZEF) who are developing a solar powered green methanol synthesis plant. The research commenced with data preprocessing which utilised historical weather data from the C3S database. Subsequently, individual subsystem models were developed such as solar photovoltaic (PV) modules, direct air capture (DAC), fluid machinery (FM), alkaline electrolysis cell (AEC), methanol synthesis (MS), distillation (DS), buffer tanks, and battery system. To ensure the microplant's functionality, a sophisticated control algorithm was devised, operating on two distinct levels: battery management and power distribution. Moreover, diverse microplant architectures were designed, to address unique operational scenarios and environmental conditions. The investigation further explored the influence of temporal granularity, and component sizing on microplant behavior. Ultimately, this thesis establishes the feasibility of the ZEF microplant, offering valuable insights for practical implementation across multiple locations. Consequently, it underscores the potential of the ZEF microplant as a promising solution in the transition towards sustainable energy alternatives.

Considering the rapidly growing energy demand in worldwide and climate deterioration caused by fossil fuel, the remarkable potential of solar energy has captured the attention of individuals and industries alike. Among different techniques, poly-Si based passivating contacts have shown great performance on solar cell application, which enabling a high efficiency of over 26%. Plasma-enhanced chemical vapor deposition (PECVD) as one of the promising technologies in a-Si contacting layer fabrication has gradually replaced the conventional LPCVD method in industry. However, the accompanied severe ion bombardment is not negligible, especially on its underlying fragile tunnelling oxide. In this work, the impact of PECVD a-Si:H contacting layer deposition on poly-Si/SiO_x passivating contact is investigated. 
PECVD radio-frequency (RF) power for the contacting a-Si layer on the underlying SiO_x is the only variable in this project, varying from 5 W to 55 W, and pinhole density acts as a bridge to help analyse the intrinsic principles. Firstly, the results of a-Si:H thin film characterization suggest that with an increasing RF power, the a-Si:H thin film is grown at a higher deposition rate and becomes porous. In addition, the pinholes in tunnel oxide are inspected by applying the concepts of “selective etching” and “pinhole magnification”. With a two-step five-point sampling method, it is shown that the effect of RF power on the pinhole density is not monotonically increasing. The highest value is found at 25 W. To explain this, a concept of “protective layer” is proposed, which is defined as a buffer layer (contacting layer) formed at the very beginning during a-Si:H deposition. It appears to be more effective when higher RF power (> 35 W) is applied. Another influence on tunnel oxide property is discussed according to the result from XPS measurement. The percentage of Si⁴⁺ species is found in the case of 25 W, corresponding to the highest pinhole density. This proves to some extent that the severe particle bombardment brought by strong power would weaken or directly break the Si-O bonds in the PECVD substrate, that is the tunnel oxide in our case.
As a result of thin film characterization, five factors contribute to pinhole formation: (i) Defects in tunnel oxide from imperfect oxidation leave potential for pinhole formation. (ii) Severe ion bombardments in PECVD deposition are allowed to weaken or break Si-O in SiO_x. (iii) Island growth of a-Si:H contacting layer makes the exposed region in tunnel oxide continue to be damaged. (iv) “Buffer layer” formation protects the substrate from ion bombardments. (v) The tensile stress applied by a-Si:H films during annealing intensifies the formation of pinholes. 
Subsequently, an unexpected result from passivation quality assessment is that higher passivation level is presented with higher pinhole density. The best passivation quality is found in the case of 25 W, with J₀ of 3.3 fA/cm² and iV_oc of 714 mV. Further, a large optimal process window for RF power adjustment is found from 25 W to 35 W, which leads to an iV_oc over 710 mV, with single side J₀ below 3.5 fA/cm². The results from specific contact resistivity indicate that it is positively correlated to the pinhole density. Eventually, the champion passivating contact with a selectivity of 14.37 in this project is expected to yield a maximum efficiency of 28.9% in an ideal c-Si solar cell.

Silicon heterojunction solar cells (SHJ) showed a record efficiency of 26.81%, approaching the theoretical limit of single-junction crystalline silicon (c-Si) solar cells. To further improve the efficiency, a wide bandgap perovskite top cell can be stacked on top of the SHJ bottom cell forming tandem solar cells, which utilize better the solar spectrum. Recently, a record efficiency of 33.70% was achieved for a monolithic two-terminal perovskite/SHJ tandem solar cell. Typically, a transparent conductive oxide (TCO) layer, functioning as the recombination junction, is used to connect the two sub-cells. However, tandem solar cells with this conventional TCO recombination junction often feature high reflection losses originating from the intermediate interfaces between the two sub-cells. Therefore, this master thesis focused on minimizing these intermediate reflection losses by substituting the TCO-based recombination junction with proposed TCO-free recombination junctions.

Firstly, comprehensive optical simulation studies that compared 2T tandem solar cells with various recombination junctions were performed. In the case of single-side-textured (front-side-flat) tandem configuration, as compared to the reference cell with tin-doped indium oxide (ITO) recombination junctions, the use of the more transparent tungsten-doped indium oxide (IWO) allowed an improved implied photocurrent density in the bottom cell (Jimp,bottom) from 18.30 mA/cm2 to 18.70 mA/cm2. Further, by using the TCO-free recombination junction composed of (p)nc-SiOx:H/(n)nc-SiOx:H or (p)nc-Si:H/(n)nc- Si:H, ranges of optimum thickness combinations were discovered, which allowed high Jimp,bottom values of 20.30 mA/cm2 or 19.80 mA/cm2, respectively. Both TCO-free recombination junctions demonstrated enhanced light coupling to the bottom cell thanks to the optimized interference effect at the intermediate interfaces between two sub-cells, minimizing the associated reflection losses. Furthermore, the designs of tandem solar cells featuring various recombination junctions were optimized to reach maximum matched tandem current density. For the reference cell with ITO recombination junction, a matched tandem current density of 19.40 mA/cm2 was obtained, while the use of TCO-free recombination junctions, for instance, 60 nm (p)nc-SiOx:H/ 70 nm (n)nc-SiOx:H or 30 nm (p)nc-Si:H/75 nm (n)nc-Si:H, demonstrated high Jimp,bottom values of 19.80 mA/cm2 and 19.80 mA/cm2, respectively. These results highlight the optical advantageous implementations of proposed TCO-free recombination junctions for monolith tandem solar cells. Similar observations but less significant improvement by using the proposed TCO-free recombination junctions were found in double-side-textured tandem solar cells. This is due to the already minimized reflection losses of the (p)nc-SiOx:H/(n)nc-SiOx:H or (p)nc-Si:H/(n)nc- Si:H configurations (1.3 mA/cm2 and 1.4 mA/cm2 respectively) as a result of the textured front surface.

Based on optical simulation studies conducted on 2T tandem solar cells, the electrical effectiveness of proposed TCO-free recombination junctions was examined by fabricating proof-of-concept single junction single-side-textured SHJ solar cells. First, we focused on the passivation optimization of the flat (100) c-Si surface as it is prone to detrimental epitaxial growth. An impressive minority carrier lifetime of 16.87 ms was achieved by combing (n)nc-Si: H and (i)a-Si: H bi-layer in a symmetrical configuration. Moreover, we also observed, in general, better conductivity when increasing thicknesses of doped nc- SiOx: H layers when they were deposited on glass or (i)a-Si: H coated glass substrates. Eventually, proof-of-concept single junction single-side-textured SHJ solar cells featuring the proposed TCO-free recombination junction were fabricated. According to the optical simulations, various optimum thickness combinations of (p)nc-SiOx: H and (n)nc-SiOx: H or (p)nc-Si: H and (n)nc-Si: H that composes the recombination junction were tested. Overall, the optically promising TCO-free recombination junctions in 2T tandem solar cells also delivered high FF values in proof-of-concept single-junction SHJ solar cells, demonstrating their potential to be implemented to fabricate high-efficiency monolithic 2T tandem solar cells.

This study explores the effects and severity of microcracks within Solarge’s innovative lightweight polymer-based photovoltaic modules, aiming to recommend a grading criterion specific to the company’s product range. Unlike the traditional PV modules which predominantly employ a glass and aluminum frame, Solarge utilizes lightweight, fully recyclable polymers. The uniqueness of Solarge’s composition presents a novel landscape in terms of durability and degradation trajectories. A pivotal concern arises from the introduction of microcracks, which inherently diminish a PV module’s power output. Leveraging Solarge’s extensive database of current-voltage measurements and electroluminescence images, an initial analysis discerned the emergence of small diagonal and v-type cracks post-production, predominantly after the lamination process. Subsequent experimental methodologies, encompassing mechanical loading and temperature cycling on these modules, demonstrated the growth of these existing cracks into diverse and more complex formations. This evolution of stressors significantly compromised module performance. A categorization system classifying cracks into noncritical (Category 1), critical (Category 2), and very critical (Category 3) was developed, with associated power losses identified for each. Using linear regression, predictive models for crack progression in each category were established. The study culminated in the formulation of a grading criterion proposed to Solarge, aiming to refine their quality assurance.

The photovoltaic (PV) market is currently dominated by crystalline silicon (c-Si) technology, which accounts for 95% of the production. However, the record single-junction c-Si solar cell has achieved a record efficiency of 26.81% approaching the theoretical efficiency limit of 29.43%. In an effort to overcome this barrier, multi-junction devices are being investigated, and perovskite/Si tandem technology is attracting a lot of interest. This is because it is compatible with well-established c-Si technology and is comparatively less expensive. Recently, two-terminal (2T) monolithic tandem devices with a c-Si bottom cell and a perovskite top cell have achieved an impressive 33.7% efficiency. By utilizing a solution-based process it allows for fabricating high-quality perovskite layers. However, problems develop when the bottom cell’s light trapping features exceed the thickness of the perovskite layer. To ensure uniform coverage of high-quality perovskite layer, the light trapping features must be lowered to sub-micrometre (< 1 μm) height.

This thesis investigates three methods for creating sub-micron features on the c-Si bottom cell. The first two approaches include wet-chemical processing from the top-down and bottom-up techniques. Using a poly-Si etch solution, the top-down approach aims to lower the height of large surface features from 3-5 μm to less than 1 μm. This method resulted in substantial reflection losses and poor passivation due to surface-induced roughness, even though the peak height was lowered to 0.9 μm. In order to tackle this issue, an additive was added to the mixture, producing a morphology with a 1.1 μm lower peak height, compared to an initial peak height of 3 μm. Further, the passivation has seen a two-fold increase in minority carrier lifetime. This increase is attributed to the reduced surface roughness that was inspected through SEM images. However, the surface still contained nano-scale features whose origination could be related to the cleaning procedure followed or the (i)a-Si:H layer growth. The second method is a bottom-up approach and uses KOH, K2SiO3, and a surface additive to create sub-micron features on a flat Siwafer. Once the chemical concentrationswere optimized, the peak height was effectively lowered to less than 0.8 μm at an F-ratio of F = 2.0. But, this experiment is conducted at a temperature of 80◦ C. Many non-uniformities in pyramid distribution were observed as well as nano-scale roughness for F-ratio of F=0. This seemed to be resolved with better pyramid homogeneity and reduced nano-scale roughness by lowering the temperature to 70◦ C. While, maintaining a peak height below 0.8 μm at F=2.0. Moreover, this approach also exhibited lower reflection losses which is close to reflection observed from large pyramidal features (˜3μm).

The last method includes the use of lithography to produce 2D periodic inverted nano pyramids. This process flow showed that patterns with critical dimensions close to 100 nm may be transferred using high-throughput nano-imprinting lithography. By using a much rigid soft mold that did not showcase any pattern distortion. However, the limitations in mask opening created issues with the nano-pyramid formation. This further requires the optimization of suitable hard mask layers. To sum up, these methods demonstrate the possibility of producing effective sub-micron features, which is promising for perovskite/Si tandem technological advancements.

Silicon heterojunction (SHJ) solar cell technology is one of the most promising PV technologies because of its high power conversion efficiencies, simple fabrication process and low manufacturing cost. The current world record efficiency of SHJ solar cell reaches up to 26.81%. SHJ solar cell produces the highest VOC over 750 mV among the c-Si solar cell technologies because of the excellent surface passivation provided by the few nanometers (i)a-Si:H layers. The objective of this thesis is to design and optimize the (i)a-Si:H bilayers that not only ensure excellent c-Si surface passivation quality but also allow less-resistive transport of charge carriers in SHJ solar cells.
First, a database focusing on the microstructure properties of (i)a-Si:H layers was established. The database was compiled by systematically varying the PECVD deposition parameters of the pressure, power, and hydrogen dilution ratio. By means of FTIR (Fourier Transform Infrared Spectroscopy) characterizations, higher power and pressure were found to correspond with an increased absorption strength of high stretching modes (HSM), which indicated a higher R* and hydrogen content. These conditions led to the formation of a film that is rich in voids and hydrogen. Conversely, a denser a-Si:H film could be achieved by increasing the hydrogen dilution ratio, where the low stretching modes (LSM) were increased and became dominant. Overall, the built database showcases the possibilities to deposit (i)a-Si:H layers with microstructure factor spanning from 0.193 to 0.805.
Subsequently, passivation optimization of the (i)a-Si:H bilayer on textured (111)-orientated c-Si wafers has been conducted. The optimal passivation is achieved by the combination of a 1 nm underdense i1 layer and a 9 nm dense i2 layer. The void-rich i1 layer with R* = 0.732 and the dense i2 layer with R* = 0.205 improved the passivation greatly from 2 ms to 7.5 ms, as compared to unoptimized STD1 layer (R* = 0.261) and STD2 layer (R* = 0.314). Despite various passivation qualities enabled by various bilayer structures, after hydrogen plasma treatment (HPT), the lifetime of all increased drastically to 17 ms, accompanied by increases FTIR-characterized in both H content and R*, which may indicate that passivation could be saturated after HPT. However, the passivation trend after VHF treatment was not clear. This could potentially be the instability in the PECVD deposition tool.
Finally, (i)a-Si:H bilayers were implemented into FBC-SHJ solar cells, solar cells endowed with a bilayer consisting of X1 layer (R* = 0.382) and D2 layer (R* = 0.205) exhibited an average Voc of 715 mV. Combined with a denser D2 film, RS is reduced, helping to counteract the elevated series resistance associated with the incorporation of the X1 layer, contributing to the enhancement of the fill factor from 78.65% to 80.53%, although at the expense if a slightly lower VOC. The best-performing cell X1 + D2 with treatments gives achieved the highest efficiency of 23.23% (22.33 % on average) and the highest VOC of 717mV compared with an average of 22.24% and 711 mV of the ‘non-optimized’ standard cells fabricated. It is also observed that after treatments, the FF increases while VOC slightly reduces. However, the observed lack of a clear efficiency improvement when using the optimized bilayer as compared to the ‘non-optimized’ standard bilayer could be attributed to the instability of the PECVD tool, which primarily affects the lifetime of precursors, coupled with the relatively large error bars present in the results.

Passivating contacts in the front-rear contacted c-Si solar cells enhances the device performance by quenching the contact recombination and enabling sufficient carrier transport. Tunneling oxide passi- vating contact (TOPCon) which consists of an interfacial oxide and a poly-SiO𝑥 layer is one of the most promising contact techniques in passivating both surfaces of the silicon wafer. However, the full area poly-SiO𝑥 layer is absorptive when it is applied at the front side which has become an efficiency limiting factor. In this project, an advanced local poly-SiO𝑥 passivating contact architecture is proposed and presented. The local poly-SiO𝑥 passivating contacts, so-called “poly-SiO𝑥 finger”, is deposited through a hard mask at predefined locations which will be only placed underneath the metal contacts. The formation of poly-SiO𝑥 finger and its application in the solar cells are discussed.

First, a silicon wafer hard mask is fabricated by a lithography process followed by a KOH wet chemical etch-back process. Specified openings down to 38.7 𝜇m are established which isolate sections of the substrate for the poly-SiO𝑥 finger formation. P+ doped a-SiO𝑥 :H is deposited using PECVD with SiO𝑥 p+ diffused emitter commercial Cz wafers through the hard mask. By investigating the influence of deposition parameters during the PECVD, specifically the power and pressure, decent uniformity of the finger deposition is achieved. An optimized deposition condition of the doped a-SiO𝑥 :H is established for the poly-SiO𝑥 finger formation: an RF power source at 15 Watt, a chamber pressure of 1.5 mbar, and a substrate temperature of 180 °C. A narrow poly-SiO𝑥 finger with a width of 40.0 𝜇m has been demonstrated.

Second, the passivation properties of the symmetrical samples are examined by varying the poly-SiO𝑥 and Al2O3 thickness for the hole carrier selective contacts. A full area p+ TOPCon and Al2O3 symmetric samples were coated on the textured diffused p+ surface with an n-type c-Si substrate to investigate the process parameters on the passivation properties. The optimal 𝑖𝑉𝑜𝑐 of p+ TOPCon samples is 662 𝑚𝑉 and a corresponding 𝐽0 of 156 𝑓 𝐴 𝑐𝑚2 which is obtained with a poly-SiO𝑥 thickness of 50 nm when annealed at 850 °C. The optimal thickness for the Al2O3 passivation layer is achieved by depositing a 20 nm thick layer followed by FGA, with an 𝑖𝑉𝑜𝑐 of 692 𝑚𝑉 and a 𝐽0 of 22.4 𝑓 𝐴/𝑐𝑚2.

Finally, a process flowchart has been created to fabricate c-Si solar cells with the local p+ TOPCon on the front p+ diffused emitter and a full area n+ TOPCon on the rear side. A localized polished area is made by a poly-etch process for the alignment between the substrate and the pattern in the lithography mask. Using the ascertained parameters during the optimization, NAOS-SiO𝑥 combining with 50 nm-thick doped p+ a-SiO𝑥 :H fingers are applied on the p+ diffused surface and 100 nm-thick n+a-SiO𝑥 :H on the rear side. A annealing step is performed for the crystallization. A 20 nm-thick Al2O3 followed by a 75 nm SiN𝑥 layer are deposited on the front side and 100 nm SiN𝑥 layer is applied on the rear side. Lithography, wet chemical etch-back together with Al/Ag(front/rear) evaporation are utilized for solar cells metallization. The fabricated c-Si solar cells with poly-SiO𝑥 fingers has a champion efficiency with an efficiency of 7.91 %, with a 𝑖𝑉𝑜𝑐 of 562 𝑚𝑉, 𝑖𝑛𝑡 𝐽𝑠𝑐 of 34.7 𝑚𝐴 𝑐𝑚2 and fill factor of 40.5 %. The limited performance originates from the poor passivation in the poly-SiO𝑥 local contact area and severe 𝑖𝑉𝑜𝑐 drop after the metallization process. For further improvement, good performing c-Si solar cells by minimizing the recombination in the poly-SiO𝑥 local fingers contacts area and optimizing metallization steps are expected to be fabricated .

This graduation report covers the process and outcome of developing and designing novel photovoltaic (PV) products for architectural and design applications. The project aimed to find innovative solutions for seamlessly integrating photovoltaics into architecture and design and thus contribute to sustainable building practices. With a hands-on, material-driven approach novel PV customization methods were developed and showcased with a demonstrator. Four concepts were proposed based on PV products made with customization methods that were developed during the project. One of these concepts was worked out into a working prototype. This demonstrated the aesthetic qualities of a novel PV coloring technology. The outcome of Solar Style formed the basis of the continued development and commercialization of PV products.

The considerable increase in the number of devices needing connectivity, such as mobile phones and Internet of Things (IoT) devices, has led to an exponential rise in data volumes during the last years, that will surely continue over the next decade. Therefore, it will be increasingly challenging to provide sufficient RF resources. A novel alternative to RF communications is Visible Light Communication (VLC). VLC is a communication technology that uses visible light as an information carrier. The use of VLC for indoor applications has been rapidly growing during the last years – Light Fidelity (LiFi) technology is an example of VLC application – with photodiodes being the most widely used receiving devices. However, looking at both indoor and outdoor communication, photovoltaic (PV) cells represent a relevant alternative for detecting the information. One of the advantages of using a PV cell as receiver is the huge sensitive area for detection of the information that simplifies alignment between transmitter and receiver.

Different light sources can be used in VLC. Typically, either LEDs or LASERs are considered, depending on the characteristics of the link (such as distance, type of receiver, indoor/outdoor application). These light sources differ in terms of spectrum, directionality, optical power density and bandwidth. The performance of the whole VLC link strongly depends on the characteristics of the light source, since it affects the ability of the receiver, such as a PV-device, to detect the information when it overlaps with the ambient light, that can reach very high values, especially in outdoor applications where the ambient light is the sunlight. Therefore, the modelling and analysis of the performance of different light sources in a PV-based VLC link will pave the way towards the realisation of a PV-based communication system of the future; and it is the focus of this thesis project.

The project goals were achieved by first reviewing the characteristics of light sources, to understand their advantages and drawbacks in (PV-based) VLC. This was followed by the development of models of the VLC data-link, with a focus on the light source, which took into account various factors such as the type of light source, its location relative to the receiver, and its dynamic behaviour. This was followed by the realisation of a test setup, to characterise different light sources, and the models were then used to simulate the light distribution from the actual light sources. Finally, the framework was used to simulate a LED-based solar simulator and an outdoor VLC data-link.