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Tesis por compendio / [ES] Las células solares de perovskitas de haluros (HaPSC) se han convertido en uno de los principales candidatos para la producción de dispositivos fotovoltaicos de nueva generación. Sin embargo, su comercialización exige que cumplan estrictos requisitos de rendimiento, seguridad y longevidad. Se sabe que la estabilidad intrínseca de las perovskitas de haluro está estrechamente relacionada con la química de los defectos que se producen en su interior, ya que algún defecto puede participar o iniciar procesos de degradación. Además, algunos de los defectos más comunes en estos sistemas crean estados de trampa poco profundos y electrónicamente activos, que pueden influir en procesos clave como el transporte y recombinación de cargas, lo que los convierte en fundamentales para determinar el rendimiento de los dispositivos. La ingeniería de disolventes ha cobrado importancia como técnica para controlar la cristalización de películas delgadas de haluros de perovskita, lo que ha dado lugar a mejoras experimentalmente observables en la calidad y estabilidad de los cristales, así como a reducciones significativas en las densidades de defectos. A pesar de los importantes esfuerzos realizados recientemente para desarrollar las HaPSC, el rendimiento y la estabilidad de las composiciones con bandas prohibidas anchas han quedado rezagados con respecto a las composiciones para los dispositivos de unión única. El objetivo de esta tesis es abordar este problema desarrollando técnicas experimentales para mejorar las perovskitas inorgánicas de haluros mixtos. Aunque la ingeniería de disolventes puede introducir, reducir o pasivar defectos electrónicamente activos (dopantes) en las perovskitas de haluro, se han realizado relativamente pocas investigaciones sobre los procesos físicos que se producen en los sistemas dopados. Además, las químicas activas de estos sistemas, que aún se están investigando, pueden dar lugar a comportamientos transitorios o a la activación de procesos complejos, lo que complica los esfuerzos experimentales. En esta tesis, estos problemas se superan empleando simulaciones por ordenador para investigar el origen y los factores que dan lugar a niveles óptimos de dopaje en las HaPSCs. Esta tesis doctoral se compone de tres artículos que han sido publicados en revistas indexadas. Dos de ellos desarrollan técnicas experimentales para controlar la cristalización de la película y la estabilidad de las perovskitas de bandas prohibidas anchas. El tercer artículo investiga el papel que desempeñan los dopantes electrónicos en el rendimiento de los dispositivos y cómo pueden aprovecharse para producir HaPSC superiores. En conjunto, estos resultados aportan nuevos conocimientos y técnicas a los experimentadores que trabajan con dispositivos de alto rendimiento. / [CA] Les cèl·lules solars de perovskita d'halur (HaPSC) s'han convertit en un dels principals candidats per a la producció de dispositius fotovoltaics de nova generació. Tanmateix, la seua comercialització requereix que compleixen exigències estrictes en termes de rendiment, seguretat i longevitat. Se sap que l'estabilitat intrínseca de les perovskites d'halur està estretament relacionada amb les químiques de defectes que es produeixen dins d'elles, ja que algun defecte pot participar o iniciar processos de degradació. A m¿es, alguns defectes predominants en aquests sistemes creen estats de trampa poc profunds i electrònicament actius, que poden influir en processos clau com el transport i la recombinació de càrregues, fent-los clau per determinar el rendiment dels dispositius. L'enginyeria de dissolvents ha guanyat rellevància com a tècnica per controlar la cristal·lització de pel·lícules primes de perovskita d'halur, donant lloc a millores experimentalment observables en la qualitat i l'estabilitat dels cristalls, així com a reduccions significatives de la densitat de defectes. Malgrat els esforços recents substancials per desenvolupar les HaPSC, el rendiment i l'estabilitat de les composicions de bandes prohibides amples s'han quedat per darrere de les adequades per a dispositius d'unió única. L'objectiu d'aquesta tesi és abordar aquest problema mitjançant el desenvolupament de tècniques experimentals per millorar les perovskites inorgàniques d'halur mixtos. Tot i que l'enginyeria de dissolvents pot introduir, reduir o passivar defectes electrònicament actius (dopants) en perovskites d'halur, hi ha hagut relativament poques investigacions sobre els processos físics que es produeixen en sistemes dopats. A més, les químiques actives d'aquests sistemes, que encara s'estan investigant, poden donar lloc a comportaments transitoris o a l'activació de processos complexos, cosa que complica els esforços experimentals. En aquesta tesi, aquests problemes es superen mitjançant l'ús de simulacions per ordinador per investigar l'origen i els factors que donen lloc a nivells òptims de dopatge en les HaPSC. Aquesta tesi doctoral està formada per tres articles que s'han publicat en revistes indexades. Dos d'aquests desenvolupen tècniques experimentals per controlar la cristal·lització de la pel·lícula i l'estabilitat de les perovskites de bandes prohibides amples. El tercer article investiga el paper que tenen els dopants electrònics a l'hora de determinar el rendiment dels dispositius i com es poden aprofitar per produir HaPSC superiors. En conjunt, aquests resultats generen noves idees i proporcionen tècniques per als experimentadors que treballen amb dispositius d'alt rendiment. / [EN] Halide perovskite solar cells (HaPSCs) have become one of the leading candidates for the production of next generation photovoltaic devices. However, commercialisation requires them to meet stringent demands in terms of performance, safety and longevity. The intrinsic stability of halide perovskites is known to be closely related to defect chemistries occurring within them since some defects can participate in, or initiate, degradation processes. Moreover, some common defects in these systems create electronically active shallow trap states, which can influence key processes such as charge transport and recombination - making them key in determining device performance. Solvent engineering has gained relevance as a technique for controlling the crystallisation of halide perovskite thin films, leading to experimentally observable improvements in crystal quality and stability as well as meaningful reductions in defect densities. Despite substantial recent efforts into developing HaPSCs, the performance and stability of wide-bandgap compositions has lagged behind those suitable for single-junction devices. The aim of this thesis is to address this problem by developing experimental techniques for improving mix-halide inorganic perovskites. Although solvent engineering can introduce, reduce or passivate electronically active defects (dopants) in halide perovskites, there have been relatively few investigations into the physics occurring in doped systems. Moreover, the active chemistries in these systems, which are still under investigation, can result in transient behaviours or the activation of complex processes - complicating experimental efforts. In this thesis, these problems are overcome by employing computer simulations to investigate the origin and factors giving rise to optimal doping levels in HaPSCs. This doctoral thesis is made up of three articles which have been published in indexed journals. Two of these develop experimental techniques for controlling the film crystallisation and stability of wide-bandgap perovskites. The third article investigates the role of electronic dopants in determining device performance, and how they may be harnessed to produce superior HaPSCs. Together, these results generate new insights and provide techniques for experimentalists working with high performance devices. / This work was funded by the Generalitat Valenciana (ACIF/2020/286), the Ministerio de Economía y Competitividad (Grant Number PID2019-107137RB-C21), European Union’s Horizon 2020 research and innovation programme (Marie Sklodowska-Curie grant No. 893194), the French Agence Nationale de la Recherche (contract number ANR-17-MPGA-0012), and the French government in the frame of the program of investments for the future (Programme d’investissement d’Avenir ANR-IEED-002-01) Alexander Wyn Stewart. acknowledges the Generalitat Valenciana and the EU for financial support (ACIF/2020/286). / Stewart, AW. (2024). Hybrid Perovskites for Photovoltaic Applications [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/202847 / Compendio

Silicon based solar cells have been used as photovoltaic devices for decades due to reasonable cost and environment- friendly nature of silicon. But the conversion efficiency of silicon solar cell is limited; for instance, the maximum conversion efficiency of a crystalline silicon solar cell available in the market developed by Kaneka Corporation is 26 % [1]. In comparison, III-V compound semiconductor multi-junction solar cells are the most efficient solar cells with efficiency of 47.1% [2]. However, due to high-cost substrate materials, III-V solar cells are not the best option for large scale production in real life. Therefore, integration of III-V compound semiconductors on silicon substrate has been studied to obtain III-V/Si multi junction solar cells with high conversion efficiency with reasonable price. To this end, we studied epitaxial growth of on GaAs deposited on Si.This thesis presents the characterization results of the above epitaxial layer and fabrication of a single junction solar cell on GaAs coated Si substrate and its performance.In the first part of the project, epitaxial layer grown by Hydride Vapor Phase Epitaxy (HVPE) on different kinds of substrates at different growth conditions are characterized to identify the optimized growth conditions and a suitable substrate. Samples are characterized by High Resolution X-ray Diffraction (HRXRD) and photoluminescence (PL) to determine the composition of and its crystalline quality and by optical microscope to assess the surface morphology. Scanning Electron Microscope (SEM) is used to study the depth of the dry etched structures.The second part of the project deals with the fabrication process consisting of 21 steps to obtain a single junction solar cell structure on GaAs/Si. This process flow will be explained in some detail along with a brief description of several tools in cleanroom that have been used for this purpose.Finally, in the third part, devices are characterized to investigate their performance. Transmission Line Method (TLM) is used to obtain important parameters such as specific contact resistance. Current- voltage (I-V) relation of solar cell is investigated to acquire its efficiency. The lowest specific contact resistance measured in this project is for p-contact (for 4041DV- cell 8) and the highest efficiency measured is 1.64% (for 4041DV- cell 6).In conclusion, although the results obtained are far from the state-of-the art results, this work has laid the foundation for future work that can lead to a breakthrough in fabricating multi-junction tandem solar cell on silicon. / Kiselbaserade solceller har använts i årtionden på grund av dess rimliga kostnad och miljövänliga natur. Omvandlingseffektiviteten för kiselsolcell är begränsad; till exempel är den maximala omvandlingseffektiviteten för solceller av kristallin kisel utvecklad av Kaneka Corporation 26 % [1]. Som jämförelse är III-V sammansatta halvledare multi-junction solceller de mest effektiva solcellerna med en effektivitet på 47,1 % [2]. På grund av de höga substratmaterialen är III-V-solceller i realiteter inte det bästa alternativet för storskalig produktion. Därför har integration av III-V sammansatta halvledare på kiselsubstrat studerats för att erhålla III-V/Si multi junction solceller med hög omvandlingseffektivitet till rimligt pris. För detta ändamål studerade vi epitaxiell tillväxt av på GaAs avsatt på Si.Denna avhandling presenterar karaktäriseringsresultaten av ovanstående epitaxiella skikt och tillverkning av en enkel förbindelse solcell på GaAs-belagt Si-substrat och dess prestanda.I den första delen av projektet karaktäriseras epitaxiallager odlat med Hydride Vapor Phase Epitaxy (HVPE) på olika typer av substrat vid olika tillväxtförhållanden för att identifiera de optimerade tillväxtförhållandena och ett lämpligt substrat. Prover kännetecknas av högupplöst röntgendiffraktion (HRXRD) och fotoluminescens (PL) för att bestämma sammansättningen av och dess kristallina kvalitet och med optiskt mikroskop för att bedöma morfologin. Scanning Electron Microscope (SEM) används för att studera djupet av de torretsade strukturerna.Den andra delen av projektet behandlar tillverkningsprocessen som består av 21 steg för att erhålla en enda förbindelse solcellsstruktur på GaAs/Si. Detta processflöde kommer att förklaras i detalj tillsammans med en kort beskrivning av flera verktyg i renrum som har använts för detta ändamål.Slutligen, i den tredje delen, karaktäriseras enheter för att frilägga dess prestanda. Transmission Line Method (TLM) används för att erhålla viktiga parametrar som specifikt kontaktmotstånd. Förhållandet mellan ström och spänning (I-V) hos solcellen undersöks för att uppnå optimal effektivitet. Den lägsta specifikt kontaktmotstånd som uppmätts i detta projekt är för p-kontakt (för 4041DV-cell 8) och den högsta uppmätta effektiviteten är 1,64% (för 4041DV-cell 6).Sammanfattningsvis, även om de erhållna resultaten är långt ifrån de senaste resultaten inom forskning, lägger detta arbete grunden för framtida arbete som kan leda till ett genombrott i tillverkningen av multi-junction tandemsolcell på kisel.

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The United Nations have set a number of sustainability goals, Agenda 2030, in order to combat the worlds largest challenges and injustices. The energy market is one of these urgent issues which must be solved. Solar energy is expected to be the fastest growing energy source in the future energy mix. It can be a great way to provide zero emission energy and also become a key part in equality as it can provide energy to people who live off the grid today and raise quality of life all over the world. The aim of this study is to compare different ligands in a copper halide complex to conclude what structural properties of the ligand might be better suited for photoluminescent applications, and especially in solar cells. Eight ligands were chosen for the complexes depending on their level of conjugation: 4,4’-bipyridine, tri(o-tolyl)phosphine, 3,6-di-2-pyridyl-1,2,4,5-tetrazine, pyridine, pyrimidine, pyrazine, phenanthroline, and 2,2’-bipyridine. A series of analytical methods were used to compare the complexes properties; X-Ray diffraction, emission and excitation spectroscopy, time-resolved photoluminescence spectroscopy, microscopy and thermochromism. From these measurements, pyridine and pyrimidine proved to have the greatest potential for working in a solar cell. This was deduced because of the detected crystallinity, having luminescence under UV-light, forming distinct wavelength peaks during excitation and emission in the flourometer, having the longest excited state lifetime and and finally, emitting distinctive colours during thermochromism. When creating the solar cell, pyridine was chosen as ligand due to higher availability than pyrimidine. The method used in this project for making the solar cell is directly applied form a previously tested method, but which was designed for another type of electron donor. This project compared the different ways of applying the copper halide complex on to the cell. The methods used were spin-coating and SILAR for creating the copper iodide thin film and vapour diffusion and immersion to introduce the ligand. These four methods were combined systematically for all combinations. The solar cells were then put in a solar simulator where voltage, current, efficiency and fill factor was measured. The best results came form the solar cell where spin coating and immersion was used, though the overall efficiency of the created cells were low. Copper halide complexes in previous studies have been proven to be reactive with oxygen and the experiments in this project were not carried out in an inert environment. This could have had significant impact on the measurements, as reactions between the complexes and oxygen may have resulted in oxidation and thus inactivation of the complexes. Therefore, it would be interesting to conduct the syntheses again but instead in an inert environment to determine whether oxygen made a major impact on the measurements. In further studies, it would also be worthwhile to investigate how the different layers of the solar cell would have to be adapted for this particular complex to obtain higher efficiency and voltage. Also, making thin film of pyrimidine to be used in a solar cell as it showed the attributes required for a solar cell. Furthermore, it would be interesting to use derivatives of pyrimidine, such as uracil and cytosine which are abundant in nature, as they might be more sustainable choices. This is due to their inherent biodegradability and not posing a threat to either health or environment when handled.

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LBIC is a technique for scanning the local quantum efficiency of solar cells. This kind of measurements needs a highly specialized, and time critical controlling software. In 1996 the client, professor Markus Rinio, constructed an LBIC system, and wrote the controlling software as a Turbo-Pascal 7.0 application, running under the MS-DOS 6.22 operating system. By now (2018) both the software and several hardware components are in dire need to be modernized. This thesis thoroughly describes several important aspects of this work, and the considerations needed for a successful result. This includes both very foundational choices about the software architecture, the choice of suitable operating system, the threading model, and the adaptation to new hardware with vastly different behavior. The project also included a new hardware module for position reports and instrument triggering, as well as several adaptations to transform the DOS-based LBIC software into a pleasant modern GUI application.

Electrical energy is used at approximately the rate of 15 Terawatts world-wide. Generating this much energy has become a primary concern for all nations. There are many ways of generating energy among which the most commonly used are non-renewable and will extinct much sooner than expected. Very active research is going on both to increase the use of renewable energy sources and to use the available energy with more efficiency. Among these sources, solar energy is being considered as the most abundant and has received high attention. The mobile phone has become one of the basic needs of modern life, with almost every human being having one.Individually a mobile phone consumes little power but collectively this becomes very large. This consideration motivated the research undertaken in this masters thesis. The objective of this thesis is to design a model for solar power based charging circuits for mobile phone using Simulink(R). This thesis explains a design procedure of solar power based mobile charger circuit using Simulink(R) which includes the models for the photo-voltaic array, maximum power point tracker, pulse width modulator, DC-DC converter and a battery. The first part of the thesis concentrates on electron level behavior of a solar cell, its structure and its electrical model.The second part is to design an array of solar cells to generate the desired output. Finally, the third part is to design a DC-DC converter which can stabilize and provide the required input to the battery with the help of the maximum power point tracker and pulse width modulation. The obtained DC-DC converter is adjustable to meet the requirements of the battery. This design is aimed at charging a lithium ion battery with nominal voltage of 3.7 V, which can be taken as baseline to charge different types of batteries with different nominal voltages.

Cette thèse s’intéresse aux effets de la compensation des dopants sur les propriétés électriques du silicium cristallin. Nous montrons que le contrôle du dopage net, qui est indispensable à la réalisation de cellules solaires à haut rendement, s’avère difficile dans les lingots cristallisés à partir de silicium contenant à la fois du bore et du phosphore. Cette difficulté s’explique par la forte ségrégation du phosphore durant la cristallisation, qui donne lieu à d’importantes variations de dopage net le long des lingots de silicium solidifés de façon directionelle. Pour résoudre ce problème, nous proposons le co-dopage au gallium pendant la cristallisation et prouvons l’efficacité de cette technique pour contrôler le dopage net le long de lingots de type p ou n fabriqués à partir d’une charge de silicium contenant du bore et du phosphore. Nous identifions les spécificités du matériau fortement compensé ainsi obtenu comme étant: une forte sensibilité de la densité de porteurs majoritaires à l’ionisation incomplète des dopants, une réduction importante de la mobilité comparée aux modèles théoriques et une durée de vie des porteurs qui est déterminée par la densité de porteurs majoritaires et dominée après éclairement prolongé par les centres de recombinaison liés aux complexes de bore et d’oxygène. Pour permettre la modélisation de cellules solaires à base de silicium purifié par voie métallurgique, nous proposons une paramétrisation des propriétés fondamentales du silicium compensé mentionnées ci dessus. Nous étudions également la dégradation de la durée de vie des porteurs sous éclairement dans des échantillons de silicium de type p et n présentant une large gamme de niveaux de dopage et de compensation. Nous montrons que le défaut bore-oxygène est issu d’un complexe formé à partir de bore substitutionnel pendant la fabrication des lingots et activé sous injection de porteurs par une reconfiguration du défaut assistée par des charges positives. Finalement, nous appliquons le co-dopage au gallium pour la cristallisation de silicium UMG et démontrons que cette technique permet d’augmenter sensiblement la tolérance au phosphore sans compromettre le rendement matière de l’étape de cristallisation ou la performance des cellules solaires avant dégradation sous éclairement. / This thesis focuses on the effects of dopant compensation on the electrical properties of crystalline silicon relevant to the operation of solar cells. We show that the control of the net dopant density, which is essential to the fabrication of high-efficiency solar cells, is very challenging in ingots crystallized with silicon feedstock containing both boron and phosphorus such as upgraded metallurgical-grade silicon. This is because of the strong segregation of phosphorus which induces large net dopant density variations along directionally solidified silicon crystals. To overcome this issue, we propose to use gallium co-doping during crystallization, and demonstrate its potential to control the net dopant density along p-type and n-type silicon ingots grown with silicon containing boron and phosphorus. The characteristics of the resulting highly-compensated material are identified to be: a strong impact of incomplete ionization of dopants on the majority carrier density, an important reduction of the mobility compared to theoretical models and a recombination lifetime which is determined by the net dopant density and dominated after long-term illumination by the boron-oxygen recombination centre. To allow accurate modelling of upgraded-metallurgical silicon solar cells, we propose a parameterization of these fundamental properties of compensated silicon. We study the light-induced lifetime degradation in p-type and n-type Si with a wide range of dopant concentrations and compensation levels and show that the boron-oxygen defect is a grown-in complex involving substitutional boron and is rendered electrically active upon injection of carriers through a charge-driven reconfiguration of the defect. Finally, we apply gallium co-doping to the crystallization of upgraded-metallurgical silicon and demonstrate that it allows to significantly increase the tolerance to phosphorus without compromising neither the ingot yield nor the solar cells performance before light-induced degradation.