This diploma thesis deals with the issues of photovoltaic cells. The main aim of this thesis is to introduce the principles of operation of solar cells and methods of detection of defects affecting their quality. The first part is about the functional properties of silicon cells and it also examines the possibilities of detecting the defects of these structures. It also describes the most commonly used modern diagnostic methods. In the next part, practical tests of photovoltaic cells using the methods electroluminescence and photoluminescence are performed. These methods are based on the excitation of luminescence radiation of the silicon material by the external light source.

The master’s thesis deals with the principle of the photoelectric effect, the composition of the photovoltaic cell and different types of solar panels. Here is described the principle of converting wind energy into electricity. This master’s thesis describes reasons for using of the hybrid system. The next section describes the measurement system which is used to measure real operating statuses. The last section is an analysis of measured values and there are listed factors influencing the design of hybrid power system.

This master’s thesis discuss the renewable energy source utilisation, to be more precise it describes the Photovoltaic Power Plants. These sources are not only capable of contributing to the regeneration of the environment and to the electricity production, but they are also capable of generating the investor’s economic profit. The individual chapters describe the external factors affecting the project, present condition of the project’s realization, the theory of photovoltaic cells and systems, CCTV camera systems, which are necessary for the power plant security.

博士(工学) / Doctor of Philosophy in Engineering / 同志社大学 / Doshisha University

Disertační práce je zaměřena na nízkoenergetické konvertory pro zpracování energie. Pro fotovoltaické generátory pracující při nízké úrovní osvětlení byly navrženy konvertory založené na konfiguraci single cell. Pomocí levných výrobních procesů a dostupných materiálů byl navržen a vyroben jednoduchý a spolehlivý termogenerátor. Výrobní postupy využívaly plazmatické aktivace povrchu pomocí výboje s dielektrickou bariérou a modifikované metody depozice PEDOT. Byly navrženy jednoduché a spolehlivé DC/DC měniče pro nízkonapěťové aplikace jako termoelektrické generátory a fotovoltaické články v konfiguraci single cell. Měniče pracují od napětí několika desítek mV a výstupní napětí může být na úrovni několika voltů. Účinnost se blíží 50% a náklady na materiál a výrobu jsou ve srovnání s použitím běžně dostupných integrovaných obvodů pro Energy Harvesting výrazně nižší. Pro řídicí obvody byly použity bipolární tranzistory, které v režimu velmi malých proudů mohou mít napájecí napětí od 0,5 V. Byla ověřena možnost výroby integrovaných obvodů s extrémně nízkým provozním napětím. Tranzistory FET zde pracují v podprahovém režimu a v režimu Bulk-driven.

Notre étude concerne la mise en place et le développement de dépôts de carbure de silicium amorphe hydrogéné (a-SiCx:H) à basse température (370°C), par voie PECVD, sur un réacteur PECVD semi-industriel à faible fréquence (440 kHz). Les propriétés chimiques, optiques et de passivation de surface des couches déposées sont analysées et l’impact du changement des débits de gaz précurseurs (silane et méthane) est aussi étudié. La possibilité d’utiliser le a-SiCx:H comme couche anti-reflet en face avant d’une cellule solaire est envisagée. Bien que l’indice de réfraction d’une couche riche en carbone soit en accord avec la condition de lame quart-d’onde requise pour une couche anti-reflet, le coefficient d’extinction est trop élevé en raison de la proportion significative de silicium dans la couche. Cette absorption peut être atténuée par l’incorporation d’azote dans la couche (a-SiCxNy:H). En revanche, la passivation de surface s’améliore lorsque la quantité de silane augmente. La plus faible vitesse de recombinaison de surface atteinte sur les échantillons après dépôt est de 10 cm.s. / Our study deals with the deposition of amorphous hydrogenated silicon carbide (a- SiCx:H) at low temperature (370°C), by PECVD technique, using a semi-industrial lowfrequency PECVD reactor (440 kHz). The deposited films are analyzed for chemical, optical and surface passivation properties, and the impact of the gas flow parameters (silane and methane) is studied. The possible use of a-SiCx:H as an antireflective coating at the front side of solar cells is investigated. Although the refractive index for high carbon concentration could be in agreement with the demand of quarter-wave layer for antireflective coating, the extinction coefficient remains too high due to a significant silicon content in the material. This absorption can be attenuated by incorporating nitrogen in the layer. However, the surface passivation improves with the silane proportion. The lowest surface recombination velocity of an as-deposited samples is about 10 cm.s.

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.

This thesis deals with the analysis of solar cells by photoluminescence method. Photoluminescence method is based on the excitation of luminescence radiation of the solar cell material by an external excitation light source. This method can detect various types of defects in the material solar cells. The main objective is the design and realization of a measuring system defects of solar cells, which is based on this method. For excitation of luminescence is used LED array. For the detection of luminescence is used CCD camera with IR optical filter. To filter out the excitation light radiation is used disc screen and optical interrupter. The parameters and options of this measuring system are verified and characterized by test measuring for example the achievable rotation speed of screen and response of optical interrupter. At the end is tested detection of luminescence radiation of solar cells in the measuring system. The measured images are compared with the method of electroluminescence.

This master’s thesis named “The Life Cycle of Solar Power, Efficiency and Return” is divided into seven chapters and focuses on the utilization of solar radiation in photovoltaic power stations and solar thermal power stations. The first chapter of this thesis familiarizes the reader with issues concerning renewable resources of energy and presents an overview of the focus of each chapter. The following second chapter is occupied with a topical research of renewable resources of energy utilization in Europe. Further the author presents a brief glance back at the past of solar energy utilization and also a prediction of future solar energy utilization in the Czech Republic. The chapter named “Specification and parameterization of individual technologies” contains an overview of today’s most utilized photovoltaic cells and panels together with an overview of utilized solar collectors and solar thermal power stations. In the following chapter named “Concretization of typical applications and realizations of photovoltaic and solar thermal power stations and determination of all related parameters” the author describes further components of photovoltaic and solar thermal systems. The economical aspect of photovoltaic component production together with an overview of utilized photovoltaic technologies is presented in this chapter. The problem of recycling photovoltaic applications and the current legislative situation regarding this issue in the Czech Republic is also outlined within this chapter. In the fifth chapter of this master’s thesis the author presents mathematical models of a photovoltaic and a solar thermal power station with the focus on economic aspects of investment efficiency assessment. Within this master’s thesis a simulation program in the computational software program Mathematica was created by the author. This program allows a calculation of economic efficiency and return of photovoltaic power station investments. The results of executed simulations are presented in the sixth chapter of this thesis. The last chapter contains an appraisal and summary of results achieved by the author of this thesis.

Photovoltaic in the Czech Republic has gone through significant development during last few years. The thesis describes physical principle of converting solar energy into electrical energy using photovoltaic cells. Photovoltaic power plant is a set of technologic components connected together to utilize solar energy and convert it into electric energy that could be distributed to electric power network. Review of the photovoltaic development in the Czech Republic and the list of the biggest operational photovoltaic power plants present important data for assessment of the current status of photovoltaic technology in the Czech Republic. Chapter operations and maintenance of photovoltaic power plants summarizes the most common causes of failures and presents diagnostic tools for service requests. Due to legislative changes, hybrid photovoltaic power plants construction has been prioritized as it is economically more efficient now. Construction of new hybrid photovoltaic power plant was assessed analytically using SWOT analysis that evaluates strong and weak sides of the projects in comparison with opportunities and threats of construction. After evaluation of obtained data the next steps of the hybrid photovoltaic power plant’s construction plan are proposed. The first part of hybrid photovoltaic power plant design contains PVGIS program's data evaluation, which provides sunlight intensity information for specified area. Obtained data were used in the second part of the design to determine proper components selection for family house hybrid photovoltaic power plant. Finally the economic view of the design and return of investments were assessed.