• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 381
  • 65
  • 46
  • 45
  • 23
  • 15
  • 13
  • 11
  • 10
  • 7
  • 3
  • Tagged with
  • 755
  • 315
  • 226
  • 156
  • 143
  • 139
  • 103
  • 78
  • 77
  • 76
  • 74
  • 70
  • 69
  • 68
  • 65
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
731

Monocouches auto‐assemblées et nanostructures de métaux nobles : préparation et application au photovoltaïque / Self‐assembled monolayer and noble metal nanostructures : preparation and application to organic photovoltaics

Dufil, Yannick 06 November 2018 (has links)
Au cours de ce travail, dans une première approche descendante, nous avons étudié la réalisation de cellules solaires multicouches évaporées à base de matériaux organiques : le pentacène et le PTCDI-C5. Nous nous sommes servis de cela pour bâtir des cellules simple jonction bicouches et les caractériser. Ces cellules ont servi de modèle de référence à notre étude et démontrent des capacités en accord avec la littérature. Nous avons ensuite produit et caractérisé des cellules multijonctions en bicouches. Une rapide étude sur le comportement d’une couche d’argent d’épaisseur nanométrique a servi à déposer la couche de recombinaison de ces cellules. Nous nous sommes ensuite attelés à la réalisation de monocouches auto-assemblées sur silicium dans le but de développer des couches actives donneur-accepteur et de pouvoir les empiler par l’approche ascendante. Après avoir étudié les groupements d’accroche silanes et acides phosphoniques, nous avons investigué la réalisation de SAM de (3-Triméthoxysilylpropyl) diéthylènetriamine (DETAS) sur silicium en tant que couche d’accroche pour les molécules actives. Nous avons mis en évidence la présence de liaisons hydrogènes aidant à l’organisation de la SAM grâce à des analyses ATR-FTIR. Nous nous sommes servis de cette SAM comme couche d’accroche pour la greffe d’une molécule photo-active le pérylène tétracarboxylique dianhydride (PTCDA). Les techniques de caractérisation par AFM, ellipsométrie et spectroscopie Raman nous ont servi à caractériser notre surface après la greffe de PTCDA / During this study, in a first top-down approach, we investigated evaporated multilayer organic solar cells built from pentacene and PTCDI-C5. We studied spectral response from these materials as well as their vacuum deposition characteristics. We used that knowledge to build simple junction and bi-layer solar cells. Those cells were the reference that allowed us to build and characterised multijonctions bi-layer solar cells with a nanostructured silver layer as recombination layer. A simple study of that silver layer was also conducted. We then switched to self-assembled monolayers on silicon in order to build donor-acceptor active layers that could be stacked, in a bottom-up approach. First, we compared silane and phosphonic acid grafting groups with an 18 carbon long alkane chain. Then we studied (3- trimethoxysilylpropyl) diethylentrimaine (DETAS) on silicon with extra care on relative humidity as a grafting parameter. We also investigated DETAS SAM to highlight hydrogen bonding within the monolayer using ATR-FTIR. DETAS SAM were then used as an anchor molecule for a photoactive molecule perylene tetracarboxylicdianhydrid (PTCDA). Characterisation technics used were AFM, ellipsometry, and Raman spectroscopy
732

Budova občanské vybavenosti / Civic amenities building

Brázdová, Kateřina January 2022 (has links)
Mixed-use building in Prostějov The aim of this master´s thesis is to elaborate the project documentation of a mixed-use building in Prostějov. The thesis consists of three parts: architectural-construction part, building services and elective part. The building has two above-ground floors. On the first floor there are storerooms, utility room, sanitary facilities and restaurant with kitchen and storerooms. The second floor is an office floor for one company which includes offices, dayroom, copyroom, meeting room and sanitary facilities. The building is founded on reinforced concrete foundation. The horizontal load-bearing and non-load-bearing structures are designed from ceramics blocks. The building is insulated by ETICS. The vertical load-bearing structures are designed from Spiroll slabs. The building has a green flat roof. There are parking spaces on the grounds. The building will be heated and cooled with a heat pump. It will also have an air condition. Part of electricity demand is covered by photovoltaics. In the third part of thesis, I replace frequently used materials with environmental ones in my project and compare them in terms of thermal engineering, acoustics and price. I used DEKSOFT, Hluk+, Autocad and Revit software. All structures comply with the valid standards and regulations.
733

Revitalizace víceúčelového objektu obce / Revitalization of a multi-purpose building in the village

Federla, Jakub January 2022 (has links)
The aim of master‘s thesis is to renovate old agricultural building and design it as nzeb building. The thesis contains three parts: 1st – design of the building, 2nd – design of building services, and 3rd – assessment of the impact of different operations in building on energy consumption. The results are then evaluated for economic and environmental savings. The renovated building in village Rozkoš will be used for many purposes. It will be divided into 3 parts – a multifunctional hall, a pub, and a club room. Multifunctional hall will be used for various activities for village itself or public. In the pub will be only cold kitchen with small dishes and beverages. Club room can be used for elderly people, workout or young people. The building is low rise and structural system is combined. The vertical load-bearing walls and columns are built of bricks. Horizontal load-bearing structures are cross vaults made also of bricks. Saddle roof is made of timber roof truss. The building site contains also an outdoor car park and a garden. The project was carried out in the Revit.
734

Administrativní budova / Office Building

Tručka, Jiří January 2022 (has links)
This master's thesis deals with project documentation of an office building with commercial premises, cafe, and canteen. The building is located in Žďár nad Sázavou, on plot 2197. The access road is from the north side. The building has 6 floors above ground and 2 underground floors. The building is designed as monolithic reinforced concrete frame with shear core. Basement consists of monolithic reinforced concrete walls. Whole building is based on reinforced concrete slab, which is supported by a system of piles. The external wall is designed from clay blocks. The facade is ventilated.
735

Mateřská a základní škola ve Škrdlovicích / Kindergarten and primary school in Škrdlovice

Peňáz, Zdeněk Unknown Date (has links)
The aim of this master project is to design a nzeb kindergarten and primary school in Škrdlovice. The building has three parts: kindergarten and primary school with 2 above–ground floors and basements are connected with a single canteen. The canteen has a flat extensive green roof, while the kindergarten and primary school have saddle roof. The kindergarten has two identical floors with playrooms, locker rooms, bed and toy storage, teacher’s office, and bathrooms. First floor of the primary school contains locker room, teacher’s’ offices, it classroom, afterschool centre, and toilets. Three classrooms, headmaster’s office, and toilets are in the second floor. The building is designed using Xella building system. The external load–bearing walls, slabs, and internal non–bearing walls are made of aerated concrete blocks. The internal load–bearing are made of lime–sand blocks. The building is insulated with non–fibrous mineral panels. The project includes design of lightning, HVAC, DHW, and photovoltaics systems. The project also includes a study of three structural details including 3D models in BIM software and their thermal assessment. The project was designed using BIM software Revit.
736

Oligothiophene Materials for Organic Solar Cells - Photophysics and Device Properties

Körner, Christian 18 July 2013 (has links)
The rapidly increasing power conversion efficiencies (PCEs) of organic solar cells (OSCs) above 10% were made possible by concerted international research activities in the last few years, aiming to understand the processes that lead to the generation of free charge carriers following photon absorption. Despite these efforts, many details are still unknown, especially how these processes can be improved already at the drawing board of molecular design. To unveil this information, dicyanovinyl end-capped oligothiophene derivatives (DCVnTs) are used as a model system in this thesis, allowing to investigate the impact of small structural changes on the molecular properties and the final solar cells. On thin films of a methylated DCV4T derivative, the influence of the measurement temperature on the charge carrier generation process is investigated. The observed temperature activation in photoinduced absorption (PIA) measurements is attributed to an increased charge carrier mobility, increasing the distance between the charges at the donor/acceptor (D/A) interface and, thus, facilitating their final dissociation. The correlation between the activation energy and the mobility is confirmed using a DCV6T derivative with lower mobility , exhibiting a higher activation energy for charge carrier generation. Another parameter to influence the charge carrier generation process is the molecular structure. Here, alkyl side chains with varying length are introduced and their influence on the intramolecular energy levels as well as the absorption and emission properties in pristine and blend films with the acceptor C60 are examined. The observed differences in intermolecular order (higher order for shorter side chains) and phase separation in blend layers (larger phase separation for shorter side chains) are confirmed in PIA measurements upon comparing the temperature dependence of the triplet exciton lifetimes. A proposed correlation between the side chain length and the coupling between D and A, which is crucial for efficient charge transfer, is not confirmed. The presented flat heterojunction solar cells underline this conclusion, giving similar photocurrent densities for all compounds. Differences in PCE are related to shifts of the energy levels and the morphology of the blend layer in bulk heterojunction devices. Furthermore, the impact of the electric field on the charge carrier generation yield is investigated in a proof-of-principle study, introducing PIA measurements in transmission geometry realized using semitransparent solar cells. The recombination analysis of the photogenerated charge carriers reveals two recombination components. Trapped charge carriers or bound charge pairs at the D/A interface are proposed as an explanation for this result. The miscibility of D and A, which can be influenced by heating the substrate during layer deposition, is of crucial importance to obtain high PCEs. In this work, the unusual negative influence of the substrate temperature on DCV4T:C60 blend layers in solar cells is investigated. By using optical measurements and structure determination tools, a rearrangement of the DCV4T crystallites is found to be responsible for the reduced absorption and, therefore, photocurrent at higher substrate temperature. The proposed blend morphology at a substrate temperature of 90° C is characterized by a nearly complete demixing of the D and A phases. This investigation is of particular relevance, because it shows the microscopic origins of a behavior that is contrary to the increase of the PCE upon substrate heating usually reported in literature. Finally, the optimization steps to achieve a record PCE of 7.7% using a DCV5T derivative as donor material are presented, including the optimization of the substrate temperature, the active layer thickness, and the transport layers.:Abstract - Kurzfassung Publications Contents 1 Introduction 2 Elementary Processes in Organic Semiconductors 2.1 Introduction 2.2 Optical Excitations in Organic Materials 2.2.1 Introduction 2.2.2 Radiative Processes: Absorption and Emission 2.2.3 Non-radiative Relaxation Processes 2.2.4 Triplet Excitons and Intersystem Crossing 2.3 Polarization Effects and Disorder 2.4 Transport Processes in Disordered Organic Materials 2.4.1 Charge Transport 2.4.1.1 The Bässler Model 2.4.1.2 Marcus Theory for Electron Transfer 2.4.1.3 Small Polaron Model 2.4.1.4 Functional Dependencies of the Charge Carrier Mobility 2.4.2 Diffusive Motion 2.4.3 Exciton Transfer Mechanisms 2.4.4 Characteristics of Exciton Diffusion 2.5 Charge Photogeneration in Pristine Materials 3 Organic Photovoltaics 3.1 General Introduction to Solar Cell Physics 3.2 Introduction to the Donor/Acceptor Heterojunction Concept 3.3 The Open-Circuit Voltage in Organic Solar Cells 3.4 Doping of Organic Semiconductors 3.5 Introduction to the p-i-n Concept 3.6 Charge Transfer Excitons in Donor/Acceptor Heterojunction Systems 3.6.1 Introduction 3.6.2 Verification of Charge Transfer Excitons in Donor/Acceptor Systems 3.7 The Process Cascade for Free Charge Carrier Generation in Donor/Acceptor Heterojunction Systems 3.7.1 The Initial Charge Transfer Step 3.7.2 The Binding Energy of the Charge Transfer Exciton 3.7.3 \"Hot\" Charge Transfer Exciton Dissociation 3.7.4 \"Cold\" Charge Transfer Exciton Dissociation 3.7.5 Supposed Influence Factors on Charge Transfer Exciton Dissociation 3.7.6 Recombination Pathways for Charge Transfer Excitons 3.7.7 Free Charge Carrier Formation and Recombination 4 Experimental Methods 4.1 Sample Preparation 4.2 Material Characterization Methods 4.2.1 Optical Characterization 4.2.2 Cyclic Voltammetry 4.2.3 Ultraviolet Photoelectron Spectroscopy 4.2.4 Atomic Force Microscopy 4.2.5 Grazing Incidence X-Ray Diffraction 4.2.6 Organic Field-Effect Transistor 4.3 Photoinduced Absorption Spectroscopy 4.3.1 Introduction 4.3.2 Derivation of the PIA Signal 4.3.3 Recombination Dynamics 4.3.4 Intensity Dependence of the PIA Signal 4.4 Solar Cell Characterization 4.4.1 External Quantum Efficiency 4.4.2 Spectral Mismatch Correction 4.4.3 Current-Voltage Characteristics 4.4.4 Optical Device Simulations 4.4.5 Optical Device Transmission Measurements 5 The Oligothiophene Material System 5.1 Introduction 5.2 Thermal Stability 5.3 Energy Levels 5.4 Optical Properties of the Pristine Materials 5.5 The Donor/Acceptor Couple: DCVnT and C60 5.6 Solar Cell Devices 5.7 Summary 6 Temperature Dependence of Charge Carrier Generation 6.1 Introduction 6.2 Principal Introduction to the PIA Measurements 6.2.1 Interpretation of the Spectra 6.2.2 Interpretation of the Frequency Scans 6.3 Temperature Dependence of the Spectra 6.4 Discussion of the Temperature Dependent Processes in the Blend Layer 6.5 Temperature Activated Free Charge Carrier Generation 6.5.1 Evaluation of the Activation Energy for the DCV4T-Me:C60 Blend 6.5.2 Comparison to a Sexithiophene Derivative (DCV6T-Me) 6.6 Summary 7 Side Chain Investigation on Quaterthiophene Derivatives 7.1 Energy Levels 7.2 Optical Properties 7.2.1 Solution and Pristine Films 7.2.2 Mixed Films with C60 7.3 Influence of the Side Chain Length on the Intermolecular Coupling 7.3.1 PIA Spectra of Pristine and Blend Layers at 10K 7.3.2 Recombination Analysis for Pristine and Blend Films at 10K 7.4 The Influence of the Side Chain Length on the Offset Charge Carrier Generation Rate at Low Temperature 7.5 In the High-Temperature Limit: Implications for Solar Cell Devices 7.5.1 PIA Spectra in Pristine and Blend Films at 200K 7.5.2 Recombination Analysis: Triplet Excitons and Free Charge Carriers 7.6 Solar Cells 7.6.1 Flat Heterojunction Devices 7.6.2 Bulk Heterojunction Devices 7.7 Summary 8 Electric-Field Dependent PIA Measurements on Complete Solar Cell Devices 8.1 Introduction 8.2 Semitransparent Organic Solar Cells 8.3 Photoinduced Absorption Measurements 8.4 Summary and Outlook 9 The Effect of Substrate Heating During Layer Deposition on the Performance of DCV4T:C60 BHJ Solar Cells 9.1 Introduction 9.2 The Importance of Morphology Control for BHJ Solar Cells 9.3 The Impact of Substrate Heating on DCV4T:C60 BHJ Solar Cells 9.4 Absorption and Photoluminescence 9.5 Topographical Investigations (AFM) 9.6 X-ray Investigations 9.6.1 1D GIXRD Measurements 9.6.2 2D GIXRD Measurements 9.7 Proposed Morphological Picture and Confirmation Measurements 9.7.1 Morphology Sketch of the DCV4T:C60 Blend Layer 9.7.2 Confirmation Measurements 9.8 The Equivalence of Temperature and Time 9.9 Summary 10 Record Solar Cells Using DCV5T-Me33 as Donor Material 10.1 Introduction 10.2 The Influence of the Substrate Temperature 10.3 Determination of the Optical Constants 10.4 Stack Optimization 10.5 Summary and Outlook 11 Conclusions and Outlook 11.1 Summary of the Photophysical Investigations 11.2 Summary of Device Investigations 11.3 Future Challenges Appendix A Detailed Description of the Experimental Setup for PIA Spectroscopy Appendix B Determination of the Triplet Level by Differential PL Measurements Appendix C Additional Tables and Figures Appendix D Reproducibility of the Solar Cell Results (Statistics) Appendix E Lists Bibliography Acknowledgments / Der rasante Anstieg des Wirkungsgrads von organischen Solarzellen über die Marke von 10% war nur durch länderübergreifende Forschungsaktivitäten während der letzten Jahre möglich. Trotz der gemeinsamen Anstrengungen, die Prozesse, die zwischen der Absorption der Photonen und der Ladungsträgererzeugung liegen, genauer zu verstehen, sind einige Fragen jedoch immer noch ungelöst, z.B. wie diese Prozesse schon auf dem Reißbrett durch die gezielte Änderung bestimmter Molekülstrukturen optimiert werden können. Um dieses Ziel zu erreichen, werden in dieser Arbeit Dicyanovinyl-substituierte Oligothiophene (DCVnTs) verwendet. Diese Materialien bieten die Möglichkeit, kleine strukturelle Änderungen vorzunehmen, deren Einfluss auf die molekularen und auf die Solarzelleneigenschaften untersucht werden soll. Der Einfluss der Messtemperatur auf den Prozess der Ladungsträgertrennung wird hier an einer methylierten DCV4T-Verbindung in einer dünnen Schicht untersucht. Die bei photoinduzierter Absorptionsspektroskopie (PIA) beobachtete Aktivierung dieses Prozesses mit zunehmender Temperatur wird auf eine erhöhte Ladungsträgerbeweglichkeit zurückgeführt. Der dadurch erhöhte effektive Abstand der Ladungen an der Grenzfläche zwischen Donator (D) und Akzeptor (A) erleichtert die endgültige Trennung der Ladungsträger. Durch den Vergleich mit einer DCV6T-Verbindung wird der Zusammenhang zwischen der Aktivierungsenergie und der Beweglichkeit bekräftigt. Die kleinere Beweglichkeit äußert sich dabei in einer größeren Aktivierungsenergie. Darüber hinaus kann der Ladungsträgergenerationsprozess auch von der Molekülstruktur abhängen. In dieser Arbeit wird untersucht, wie sich die Länge von Alkylseitenketten auf die Energieniveaus der Moleküle, aber auch auf die Absorptions- und Lumineszenzeigenschaften der Materialien in reinen und in Mischschichten mit dem Akzeptor C60 äußert. Die ermittelten Unterschiede bezüglich der Molekülordnung (geordneter für kürzere Seitenketten) und der Phasengrößen in Mischschichten (größere Phasen bei kürzerer Kettenlänge) werden in der Untersuchung der Temperaturabhängigkeit der Lebensdauer von Triplettexzitonen mittels PIA-Messungen bestätigt. Für Solarzellen ist von Bedeutung, ob sich die Seitenkettenlänge auf die Wechselwirkung zwischen D und A auswirkt. Der vermutete Zusammenhang wird hier nicht bestätigt. Ein ähnlicher Photostrom für alle untersuchten Verbindungen in Solarzellen mit planaren Heteroübergängen unterstreicht diese Schlussfolgerung. Unterschiede im Wirkungsgrad werden auf Änderungen der Energieniveaus und die Morphologie in Mischschichtsolarzellen zurückgeführt. Des Weiteren wird in einer Machbarkeitsstudie der Einfluss des elektrischen Felds auf die Generationsausbeute freier Ladungsträger untersucht. Dafür werden halbtransparente Solarzellen verwendet, die es ermöglichen, PIA-Messungen in Transmissionsgeometrie durchzuführen. Als mögliche Erklärung für das Auftreten zweier Rekombinationskomponenten in der Analyse des Rekombinationsverhaltens der durch Licht erzeugten Ladungsträger werden eingefangene Ladungsträger und gebundene Ladungsträgerpaare an der D/A-Grenzfläche genannt. Das Mischverhalten von D und A kann durch ein Heizen des Substrates während des Verdampfungsprozesses eingestellt werden, was von entscheidender Bedeutung für eine weitere Steigerung des Wirkungsgrades ist. Für DCV4T:C60-Mischschichtsolarzellen wird jedoch eine Verschlechterung des Wirkungsgrads zu höheren Substrattemperaturen beobachtet. Durch optische Messungen und Methoden zur Schichtstrukturbestimmung wird dieser Effekt auf eine Umordnung der DCV4T-Kristallite für hohe Substrattemperaturen und die damit verbundene Verringerung der Absorption und damit auch des Photostroms zurückgeführt. Bei einer Substrattemperatur von 90° C sind die D- und A-Komponenten fast vollständig entmischt. Dieses Beispiel ist von besonderer Bedeutung, weil hier die Ursachen für ein Verhalten aufgezeigt werden, das entgegen den Beispielen aus der Literatur eine Abnahme des Wirkungsgrads beim Aufdampfen der aktiven Schicht auf ein geheiztes Substrat zeigt. Schließlich werden die Optimierungsschritte dargelegt, mit denen Solarzellen mit einer DCV5T-Verbindung als Donatormaterial auf einen Rekordwirkungsgrad von 7,7% gebracht werden. Dabei wird die Substrattemperatur, die Dicke der aktiven Schicht und die Transportschichten angepasst.:Abstract - Kurzfassung Publications Contents 1 Introduction 2 Elementary Processes in Organic Semiconductors 2.1 Introduction 2.2 Optical Excitations in Organic Materials 2.2.1 Introduction 2.2.2 Radiative Processes: Absorption and Emission 2.2.3 Non-radiative Relaxation Processes 2.2.4 Triplet Excitons and Intersystem Crossing 2.3 Polarization Effects and Disorder 2.4 Transport Processes in Disordered Organic Materials 2.4.1 Charge Transport 2.4.1.1 The Bässler Model 2.4.1.2 Marcus Theory for Electron Transfer 2.4.1.3 Small Polaron Model 2.4.1.4 Functional Dependencies of the Charge Carrier Mobility 2.4.2 Diffusive Motion 2.4.3 Exciton Transfer Mechanisms 2.4.4 Characteristics of Exciton Diffusion 2.5 Charge Photogeneration in Pristine Materials 3 Organic Photovoltaics 3.1 General Introduction to Solar Cell Physics 3.2 Introduction to the Donor/Acceptor Heterojunction Concept 3.3 The Open-Circuit Voltage in Organic Solar Cells 3.4 Doping of Organic Semiconductors 3.5 Introduction to the p-i-n Concept 3.6 Charge Transfer Excitons in Donor/Acceptor Heterojunction Systems 3.6.1 Introduction 3.6.2 Verification of Charge Transfer Excitons in Donor/Acceptor Systems 3.7 The Process Cascade for Free Charge Carrier Generation in Donor/Acceptor Heterojunction Systems 3.7.1 The Initial Charge Transfer Step 3.7.2 The Binding Energy of the Charge Transfer Exciton 3.7.3 \"Hot\" Charge Transfer Exciton Dissociation 3.7.4 \"Cold\" Charge Transfer Exciton Dissociation 3.7.5 Supposed Influence Factors on Charge Transfer Exciton Dissociation 3.7.6 Recombination Pathways for Charge Transfer Excitons 3.7.7 Free Charge Carrier Formation and Recombination 4 Experimental Methods 4.1 Sample Preparation 4.2 Material Characterization Methods 4.2.1 Optical Characterization 4.2.2 Cyclic Voltammetry 4.2.3 Ultraviolet Photoelectron Spectroscopy 4.2.4 Atomic Force Microscopy 4.2.5 Grazing Incidence X-Ray Diffraction 4.2.6 Organic Field-Effect Transistor 4.3 Photoinduced Absorption Spectroscopy 4.3.1 Introduction 4.3.2 Derivation of the PIA Signal 4.3.3 Recombination Dynamics 4.3.4 Intensity Dependence of the PIA Signal 4.4 Solar Cell Characterization 4.4.1 External Quantum Efficiency 4.4.2 Spectral Mismatch Correction 4.4.3 Current-Voltage Characteristics 4.4.4 Optical Device Simulations 4.4.5 Optical Device Transmission Measurements 5 The Oligothiophene Material System 5.1 Introduction 5.2 Thermal Stability 5.3 Energy Levels 5.4 Optical Properties of the Pristine Materials 5.5 The Donor/Acceptor Couple: DCVnT and C60 5.6 Solar Cell Devices 5.7 Summary 6 Temperature Dependence of Charge Carrier Generation 6.1 Introduction 6.2 Principal Introduction to the PIA Measurements 6.2.1 Interpretation of the Spectra 6.2.2 Interpretation of the Frequency Scans 6.3 Temperature Dependence of the Spectra 6.4 Discussion of the Temperature Dependent Processes in the Blend Layer 6.5 Temperature Activated Free Charge Carrier Generation 6.5.1 Evaluation of the Activation Energy for the DCV4T-Me:C60 Blend 6.5.2 Comparison to a Sexithiophene Derivative (DCV6T-Me) 6.6 Summary 7 Side Chain Investigation on Quaterthiophene Derivatives 7.1 Energy Levels 7.2 Optical Properties 7.2.1 Solution and Pristine Films 7.2.2 Mixed Films with C60 7.3 Influence of the Side Chain Length on the Intermolecular Coupling 7.3.1 PIA Spectra of Pristine and Blend Layers at 10K 7.3.2 Recombination Analysis for Pristine and Blend Films at 10K 7.4 The Influence of the Side Chain Length on the Offset Charge Carrier Generation Rate at Low Temperature 7.5 In the High-Temperature Limit: Implications for Solar Cell Devices 7.5.1 PIA Spectra in Pristine and Blend Films at 200K 7.5.2 Recombination Analysis: Triplet Excitons and Free Charge Carriers 7.6 Solar Cells 7.6.1 Flat Heterojunction Devices 7.6.2 Bulk Heterojunction Devices 7.7 Summary 8 Electric-Field Dependent PIA Measurements on Complete Solar Cell Devices 8.1 Introduction 8.2 Semitransparent Organic Solar Cells 8.3 Photoinduced Absorption Measurements 8.4 Summary and Outlook 9 The Effect of Substrate Heating During Layer Deposition on the Performance of DCV4T:C60 BHJ Solar Cells 9.1 Introduction 9.2 The Importance of Morphology Control for BHJ Solar Cells 9.3 The Impact of Substrate Heating on DCV4T:C60 BHJ Solar Cells 9.4 Absorption and Photoluminescence 9.5 Topographical Investigations (AFM) 9.6 X-ray Investigations 9.6.1 1D GIXRD Measurements 9.6.2 2D GIXRD Measurements 9.7 Proposed Morphological Picture and Confirmation Measurements 9.7.1 Morphology Sketch of the DCV4T:C60 Blend Layer 9.7.2 Confirmation Measurements 9.8 The Equivalence of Temperature and Time 9.9 Summary 10 Record Solar Cells Using DCV5T-Me33 as Donor Material 10.1 Introduction 10.2 The Influence of the Substrate Temperature 10.3 Determination of the Optical Constants 10.4 Stack Optimization 10.5 Summary and Outlook 11 Conclusions and Outlook 11.1 Summary of the Photophysical Investigations 11.2 Summary of Device Investigations 11.3 Future Challenges Appendix A Detailed Description of the Experimental Setup for PIA Spectroscopy Appendix B Determination of the Triplet Level by Differential PL Measurements Appendix C Additional Tables and Figures Appendix D Reproducibility of the Solar Cell Results (Statistics) Appendix E Lists Bibliography Acknowledgments
737

Combinatorial Synthesis and High-Throughput Analysis of Halide Perovskite Materials for Thin-Film Optoelectronic Devices

Näsström, Hampus 30 September 2022 (has links)
Metallhalogenid-Perowskite (MHP) haben sich als hervorragende Materialklasse im Bereich der Optoelektronik erwiesen, obwohl die Degradation der häufig verwendeten organischen Komponenten ihre Langzeitstabilität begrenzt. Um schnell stabile Alternativen zu finden, ist eine Parallelisierung des Prozesses der Materialentwicklung durch kombinatorische Synthese und Hochdurchsatzanalyse erforderlich. In dieser Arbeit wird dies durch die Entwicklung, Implementierung und Validierung zweier komplementärer Methoden für die kombinatorische Synthese realisiert. Zum einen wurde die lösungsmittelbasierte Methode des kombinatorischen Tintenstrahldrucks weiterentwickelt, indem ein neuer Algorithmus für eine verbesserte Tintenmischung bereitgestellt und validiert wurde. Zum anderen wurde die Synthese von CsyPb1-y(BrxI1-x)2-y-Doppelgradientenschichten durch Co-Verdampfung erreicht. Kombinatorische Bibliotheken, die durch diese beiden Methoden hergestellt wurden, wurden für die Hochdurchsatzuntersuchung der strukturellen und optischen Eigenschaften der anorganischen CsyPb1-y(BrxI1-x)2-y-MHP verwendet. Dies ermöglichte die schnelle Erstellung vollständiger Phasendiagramme für Dünnfilme des CsPb(BrxI1-x)3-Mischkristalls, die zeigen, dass die Zugabe von Br die halbleitende Perowskitphase stabilisiert und niedrigere Verarbeitungstemperaturen ermöglicht. Darüber hinaus wurden CsyPb1-y(BrxI1-x)2-y-Bibliotheken mit automatisierten, kontaktlosen optischen Raster-Messungen untersucht, die eine schnelle Sichtung von über 3400 Zusammensetzungen ermöglichten. Dies ermöglichte die Bewertung des photovoltaischen Potenzials von CsyPb1-y(BrxI1-x)2-y über einen sehr breiten Bereich von Zusammensetzungen. Das höchste Wirkungsgradpotenzial wurde für stöchiometrische Zusammensetzungen gefunden, wobei ein Überschuss an Pb oder Cs zu erhöhten Verlusten durch nichtstrahlende Rekombination führt. Diese Ergebnisse liefern wichtige Erkenntnisse für die weitere Entwicklung von anorganischen MHP-Bauelementen. / To keep up with the increasing need for specialized materials, a parallelization of the materials discovery process is needed through combinatorial synthesis and high-throughput analysis. The acceleration of materials discovery is especially of interest in the area of optoelectronics where metal halide perovskites (MHPs) have proven to be an excellent material class and have achieved impressive performance in photovoltaic devices among other applications. However, the degradation of the frequently employed organic components contributes to limiting the long-term stability of MHP devices. In this work, accelerated materials discovery is addressed through the development, implementation, and validation of two complementary methods for combinatorial synthesis. Firstly, the solution-based method of combinatorial inkjet printing was further developed by providing and validating a new algorithm for improved ink mixing. Secondly, the vapor-based synthesis of double-gradient CsyPb1-y(BrxI1-x)2-y was achieved by co-evaporation. Combinatorial libraries created by both methods were used for the high-throughput investigation of the structural and optical properties of the inorganic CsyPb1-y(BrxI1-x)2-y MHPs. This enabled the fast construction of complete phase diagrams for thin-films of the CsPb(BrxI1-x)3 solid solution which show that the addition of Br stabilizes the semiconducting perovskite phase and allows for lower processing temperatures. Additionally, CsyPb1-y(BrxI1-x)2-y libraries were investigated by automized, contact-less, optical mapping measurements, enabling the rapid screening of over 3400 compositions. This enabled the assessment of the photovoltaic potential of CsyPb1-y(BrxI1-x)2-y over a very broad compositional range. The maximum efficiency potential was found for stoichiometric compositions, with excess of Pb or Cs causing increased losses by non-radiative recombination. These results provide vital knowledge for further development of inorganic MHP devices.
738

Ultrafast Exciton Dynamics and Optical Control in Semiconductor Quantum Dots

Wijesundara, Kushal Chinthaka 26 July 2012 (has links)
No description available.
739

Solution growth of polycrystalline silicon on glass using tin and indium as solvents

Bansen, Roman 14 July 2016 (has links)
Mit der vorliegenden Arbeit wird das Wachstum von polykristallinem Silicium auf Glas bei niedrigen Temperaturen aus metallischen Lösungen in einem Zweistufenprozess untersucht. Im ersten Prozessschritt werden nanokristalline Siliziumschichten (nc-Si) hergestellt, entweder durch die direkte Abscheidung auf geheizten Substraten oder durch als ''Amorphous-Liquid-Crystalline''(ALC)-Umwandlung bezeichnete metall-induzierte Kristallisation. Im zweiten Prozessschritt dienen die Saatschichten als Vorlage für das Wachstum von deutlich größeren Kristalliten durch stationäre Lösungszüchtung. Die ALC-Prozessdauer konnte durch umfassende Parameterstudien signifikant reduziert werden. Die Charakterisierung der durch direkte Abscheidung auf geheizten Substraten entstehenden nc-Si Saatschichten offenbarte, dass es sich dabei um individuelle Saatkörner handelt, die in eine quasi-amorphe Matrix eingebettet sind. Die Oxidation der Saatschichten vor dem zweiten Prozessschritt wurde als ein wesentliches Hindernis für das Wachstum identifiziert. Als erfolgreichste Lösung zur Überwindung dieses Problems hat sich ein anfänglicher Rücklöseschritt erwiesen. Da diese Methode jedoch schwierig zu kontrollieren ist, wurde ein UV-Laser-System entwickelt und installiert. Erste Resultate zeigen epitaktisches Wachstum an den Stellen, an denen das Oxid entfernt wurde. Bei der Lösungszüchtung auf ALC-Schichten beginnt das Wachstum an einigen größeren Saatkristallen, von wo aus umliegende Gebiete lateral überwachsen werden. Obwohl Kristallitgrößen bis zu 50 Mikrometern erreicht wurden, war es noch nicht möglich, geschlossene Schichten zu erzielen. Durch Lösungszüchtung auf nc-Si Saatschichten hingegen konnte dieses Ziel erreicht werden. Geschlossene, polykristalline Si-Schichten wurden erzeugt, auf denen alle Si-Kristallite miteinander verbunden sind. Neben den Wachstumsexperimenten wurden 3D-Simulationen durchgeführt, in denen u.a. unterschiedliche Heizerkonfigurationen simuliert wurden. / The subject of this thesis is the investigation of the growth of polycrystalline silicon on glass at low temperatures from metallic solutions in a two-step growth process. In the first process step, nanocrystalline Si (nc-Si) films are formed either by direct deposition on heated substrates, or by a metal-induced crystallization process, referred to as amorphous-liquid-crystalline (ALC) transition. In the second process step, these seed layers serve as templates for the growth of significantly larger Si crystallites by means of steady-state solution growth. Extensive parameter studies for the ALC process helped to bring down the process duration significantly. Characterization of the nc-Si seed layers, formed by direct deposition on heated substrates, showed that the layer is composed of individual seeds, embedded in a quasi-amorphous matrix. The oxidation of the seed layers prior to the second process step was found to be a major obstacle. The most successful solution has been an initial melt-back step. As the process is hard to control, though, a UV laser system has been developed and installed. First promising results show unobstructed epitaxial growth where the oxide has been removed. Steady-state solution growth on ALC seed layers was found to start from a few larger seed crystals, and then cover the surrounding areas by lateral overgrowth. Although crystallites with sizes of up to 50 micrometers were obtained, it was not yet possible to achieve full surface coverage with a continuous layer. By solution growth on nc-Si seed layers, however, it was eventually possible to achieve this goal. Continuous, polycrystalline Si layers were grown, on which all Si crystallites are interlocked. The growth experiments were accompanied by 3D simulations, in which e.g. different heater configurations have been simulated.
740

Elaboration et caractérisation de structures Silicium-sur-Isolant réalisées par la technologie Smart Cut™ avec une couche fragile enterrée en silicium poreux / Elaboration and characterization of Silicon-On-Insulator structures made by the Smart Cut™ technology with a weak embedded porous silicon layer

Stragier, Anne-Sophie 17 October 2011 (has links)
Au vu des limitations rencontrées par la miniaturisation des circuits microélectroniques, l’augmentation de performances des systèmes repose largement aujourd’hui sur la fabrication d’empilements de couches minces complexes et innovants pour offrir davantage de compacité et de flexibilité. L’intérêt grandissant pour la réalisation de structures innovantes temporaires, i.e. permettant de réaliser des circuits sur les deux faces d’un même film, nous a mené à évaluer les potentialités d’une technologie combinant le transfert de films minces monocristallins, i.e. la technologie Smart Cut™, et un procédé de de porosification partielle du silicium afin de mettre au point une technologie de double report de film monocristallin. En ce sens, des substrats de silicium monocristallin ont été partiellement porosifiés par anodisation électrochimique. La mise en œuvre de traitements de substrats partiellement poreux a nécessité l’emploi de techniques de caractérisation variées pour dresser une fiche d’identité des couches minces poreuses après anodisation et évaluer l’évolution des propriétés de ces couches en fonction des différents traitements appliqués. Les propriétés chimiques, structurales et mécaniques des couches de Si poreux ont ainsi été étudiées via l’utilisation de différentes techniques de caractérisation (XPS-SIMS, AFM-MEB-XRD, nanoindentation, technique d’insertion de lame, etc.). Ces études ont permis d’appréhender et de décrire les mécanismes physiques mis au jeu au cours des différents traitements et de déterminer les caractéristiques {porosité, épaisseur} optimales des couches poreuses compatibles avec les séquences de la technologie proposée. La technologie Smart Cut™ a ainsi été appliquée à des substrats partiellement porosifiés menant à la fabrication réussie d’une structure temporaire de type Silicium-sur-Isolant avec une couche de silicium poreux enterrée. Ces structures temporaires ont été « démontées » dans un second temps par collage polymère ou collage direct et insertion de lame menant au second report de film mince monocristallin par rupture au sein de la couche porosifiée et donc fragile. Les structures fabriquées ont été caractérisées pour vérifier leur intégrité et leurs stabilités chimique et mécanique. Les propriétés cristallines du film mince de Si monocristallin, reporté en deux temps, ont été vérifiées confirmant ainsi la compatibilité des structures fabriquées avec des applications microélectroniques telles que les applications de type « Back-Side Imager » nécessitant une implémentation de composants sur les deux faces du film. Ainsi une technologie prometteuse et performante a pu être élaborée permettant le double report de films minces monocristallins et à fort potentiel pour des applications variées comme les imageurs visibles ou le photovoltaïque. / As scaling of microelectronic devices is confronted from now to fundamental limits, improving microelectronic systems performances is largely based nowadays on complex and innovative stack realization to offer more compaction and flexibility to structures. Growing interest in the fabrication of innovative temporary structures, allowing for example double sided layer processing, lead us to investigate the capability to combine one technology of thin single crystalline layer transfer, i.e. the Smart Cut™ technology, and partial porosification of silicon substrate in order to develop an original double layer transfer technology of thin single crystalline silicon film. To this purpose, single crystalline silicon substrates were first partially porosified by electrochemical anodization. Application of suitable treatments of porous silicon layer has required the use of several characterization methods to identify intrinsic porous silicon properties after anodization and to verify their evolution as function of different applied treatments. Chemical, structural and mechanical properties of porous silicon layers were studied by using different characterization techniques (XPS-SIMS, AFM-MEB-XRD, nanoindentation, razor blade insertion, etc.). Such studies allowed comprehending and describing physical mechanisms occurring during each applied technological steps and well determining appropriated {porosity, thickness} parameters of porous silicon layer with the developed technological process flow. The Smart Cut™ technology was successfully applied to partially porosified silicon substrates leading to the fabrication of temporary SOI-like structures with a weak embedded porous Si layer. Such structures were then “dismantled” thanks to a second polymer or direct bonding and razor blade insertion to produce a mechanical rupture through the fragile embedded porous silicon layer and to get the second thin silicon film transfer. Each fabricated structure was characterized step by step to check its integrity and its chemical and mechanical stabilities. Crystalline properties of the double transferred silicon layer were verified demonstrating the compatibility of such structures with microelectronic applications such as “Back-Side Imagers” needing double-sided layer processing. Eventually, a promising and efficient technology has been developed to allow the double transfer of thin single crystalline silicon layer which presents a high potential for various applications such as visible imagers or photovoltaic systems.

Page generated in 0.0364 seconds