Дисертації з теми "Halide materials"
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1
RAY, ANIRUDDHA. "Synthesis and Characterization of Halide Perovskites and Lower-Dimensional Metal Halide Based Materials." Doctoral thesis, Università degli studi di Genova, 2021. http://hdl.handle.net/11567/1046865.
Повний текст джерелаАнотація:
The goal of this doctoral thesis is to synthesize metal halide octahedra based materials of varying dimensionality and explore their intrinsic structure-property relationships while attempting to apply them in prototype devices.
In Chapter 2 we found using our solvent acidolysis crystallization (SAC) method, 44% of methylammonium can be replaced with a larger organic cation (dimethylammonium) without breaking the 3-dimensional (3D) perovskite structure. We then employed different temperature-dependent studies to explore the implications of such a mixed organic cation composition on the structure and on the optoelectronic properties as well as on photodetector performance.
In Chapter 3 we used the SAC process to fabricate lead-free 2D methylammonium copper halide materials. Here we found that tuning the halide compositions not only modulated the bulk phase and optical properties but also the finer structural effects such as vacancy positions and thermal disorder parameters. We connected these local atomic scale observations to the efficacy of ionic migration in these materials that also modulates their performance in resistive switching memory devices.
In Chapter 4 we explored the structural versatility of Cs-Pb-Br based compounds by studying the connection between the nature and size of the solvated species and the precipitated 0D Cs4PbBr6 and 3D CsPbBr3 powders. Identifying the spectroscopic signatures of the species helped us select the appropriate solvents to obtain 3D-free Cs4PbBr6 that we studied for the first time using 133Cs and 207Pb solid-state nuclear magnetic resonance. We hypothesized on the possible origins of the green emission in these 0D compounds and also studied their suitability for radioluminescence applications.
2
Tomita, Hiroki. "Synthesis and Characterization of Copper Halide Complex Materials." Thesis, KTH, Tillämpad fysikalisk kemi, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-292153.
Повний текст джерелаАнотація:
Energiförbrukning är ett hett ämne i världen idag, eftersom världens befolkning fortsätter att växa. Som ett resultat ökar också den globala energiförbrukningen snabbt och utsläppen av koldioxid därmed, vilket påverkar global uppvärmning och klimatförändringar. Således kommer utvecklingen av förnybara energikällor att bli en av nödvändighet. Solenergi utgör en förnybar energikälla och uppvisar en enorm potential för att tillgodose det globala energibehovet. En solcell är kan användas för att omvandla solljus till elektricitet. Många typer av solceller har utvecklats under det senaste decenniet, och forskning för att förbättra effektiviteten kommer att fortsätta i framtiden. Material baserade på kopparhalogenidkomplex har uppvisat intressanta optiska och elektrokemiska egenskaper på grund av flera laddningsöverföringsexciterade tillstånd. Genom att kombinera kopparhalogenidsystem med organiska ligander med två bindningsgrupper, kommer komplexet att kunna bilda nätverksstrukturer i flera dimensioner och därmed effektivt kunna leda ström. Eftersom kopparhalogenidkomplex uppvisar unika optiska och elektriska egenskaper, är det värt att undersöka dem för användning i solceller. Syftet med examensarbete har varit att undersöka kopparhalogenidkomplex med optiska och elektrokemiska egenskaper. Kopparhalogenidkomplex med bidentatligander har syntetiserats och applicera som tunna filmer undersöktes. I kapitel 1 och 2 av uppsatsen presenteras bakgrunden och en introduktion av denna studie, samt de experimentella metoderna. I kapitel 3 beskrivs syntesen av kopparjodid-4,4'-bipyridinkomplex och karakteriseringen av detsamma. Applicering av det resulterande materialet på glassubstrat diskuteras också. I kapitel 4 beskrivs syntesen av kopparhalogenid-N-oxid-4,4'-bipyridinkomplex med efterföljande karakterisering. I kapitel 5 undersöks metoder för att applicera kopparjodidpyridin på koppar-folie och FTO-belagda glassubstrat.Energy consumption is presently a hot topic in the world since the world’s population continues to grow. As a result, global energy consumption is increasing rapidly and the emission of carbon dioxide is also increasing, which causes global warming and climate change. Thus, the development of renewable energy sources will be one of the solutions. Solar energy is one of the renewable energy sources and has a huge potential to satisfy the global energy demand. A solar cell harvests light and converts it to electricity. Many kinds of solar cells have been developed in the past decades, and investigation for the improvement of the efficiency will be continued in the future. Copper halide organic complex materials have some potential for optical and electrochemical properties due to several charge transfer states inside the structure. By combining copper halide with bidentate organic ligands, the complex will form high dimensional network structure and will have electrical property due to the formation of electron conducting paths. Since copper halide complex has potential for unique optical and electrical properties, it is worth investigating for the further photovoltaic application. The aim of the thesis is to investigate copper halide complex material showing optical and electrochemical property. Copper halide complex with bidentate ligands were synthesized and the way to apply copper halide complex to films were also investigated in this thesis. In chapter 1 and 2, the background and the introduction of this study and the experimental methods are presented. In chapter 3, the synthesis of copper iodide 4,4’-bipyridine complex and the characterization of the complex sample are presented. The application of the complex to glass substrate is also discussed. In chapter 4, the synthesis of copper halide N-oxide-4,4’-bipyridine complex and the characterization are discussed. In chapter 5, the way to apply copper iodide pyridine to copper foil and FTO-coated glass substrate is discussed.
3
Nariyan, Elham. "Halide Removal from Water by Novel Bismuth Materials." Thesis, Griffith University, 2020. http://hdl.handle.net/10072/399435.
Повний текст джерелаАнотація:
Water is scarce and there is a high demand for water usage at different parts of domestic usage (9%), agriculture (70%) and industries (21%). The halides in natural and sea waters are typically of a ration of Cl: Br: I is 100-200:10:1, which means chloride is 10-20 times more than bromide and bromide is 10 times of iodide. Excessive halides-release into the water could be as a result of natural or human activities, for example, mining and produced waters from oil and gas industries could release a high level of halides in water. Removal of excessive amount of halides is crucial for human and living creatures. High chloride concentration could lead to destruction to aquatic lives (as indicated by A. maculatum and R. sylvatica), phytotoxicity, crop damage, corrosion of pipes, and other infrastructures (such as reduced electrode lifetime in hydrometallurgy). Iodide/iodine has some radioactive isotopes and contributed to the environmental disasters during the Chernobyl and Fukushima catastrophes. However, iodide and bromide even at very low concentrations also could bring up problems in health issues such as producing disinfection by-products (DBPs) during water treatment.
More than 600 species of DBPs could be produced in the chlorination disinfections process, and some of the DBPs are known to be very toxic and their levels in water are so restricted. For example, Environmental Protection Agency (EPA) has set limitations for chloroform and bromodichloromethane at 80 and 60 ppb, respectively. The best way to avoid DBPs production is to remove the excessive amount of halides before application of any kind of oxidation for water treatment.
This thesis is focused on removal of Cl-, Br- and I- ions in water. F- is excluded because F- is much easier to precipitate out in comparison to the other three halide anions. Two types of novel bismuth-based materials have been developed for removal of halides at high concentrations (> 1000 mg/L) and low concentrations (< 10 mg/L), respectively. The high concentration halide removal addresses issues in mining industry, whilst the low concentration removal addresses the issue of drinking water quality.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Eng & Built Env
Science, Environment, Engineering and Technology
Full Text
4
Harwell, Jonathon R. "Optoelectronic applications of lead halide perovskites." Thesis, University of St Andrews, 2018. http://hdl.handle.net/10023/16943.
Повний текст джерелаАнотація:
Hybrid perovskites are a new class of semiconductor which have proven to be an ideal material for making thin film solar cells. They have the advantages of flexibility, low cost, and easy processing, whilst achieving efficiencies competitive with monocrystalline silicon. Many of the properties which make them ideal for solar cells are also applicable to light emitting devices, and there is now increasing interest in their application for light emitting diodes (LEDs) and lasers. This thesis aims to use a range of novel spectroscopy techniques to investigate the origin of these favourable properties, and to exploit these properties to produce high performance distributed feedback lasers. A detailed understanding of the origins of the excellent properties of hybrid perovskites is of crucial importance in the search for new variations with improved performance or lowered toxicity. This thesis uses Kelvin probe, air photoemission, and resonant ultrasound spectroscopy to probe deeply into the underlying physics of hybrid perovskite single crystals and devices. Using these techniques, we are able to produce detailed maps of the energy levels in a common perovskite solar cell, and we also gain strong insight into the underlying strains and instabilities in the perovskite structure that give rise to their elastic properties. The strong light emission of hybrid perovskites is then exploited to produce high quality distributed feedback lasers emitting in the green and infrared part of the spectrum. These lasers are observed to have superior stability, good thresholds, and many interesting beam parameters owing to their high refractive index. We explore a wide range of processing methods in order to achieve the lowest lasing threshold and the best stability. Finally, we investigate the properties of low dimensional perovskites and investigate their potential in optoelectronic applications.
5
Demirbas, Erhan. "Investigation of lamp phenomena and lamp materials." Thesis, University of Sheffield, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268289.
Повний текст джерела
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Harrison, Richard Allen 1963. "Far-infrared properties of halide glasses by molecular dynamics." Thesis, The University of Arizona, 1990. http://hdl.handle.net/10150/277257.
Повний текст джерелаАнотація:
Recent discoveries of low-loss, far-infrared transmitting halide glasses have sparked much interest in extending fiber-optic technology into the infrared region. However, a far greater than theoretical loss has been observed which has slowed research in the field. For this reason, computer modeling of several halide glass systems was performed in order to develop a fundamental understanding of the relationships between structural and optical properties of these glasses. ZrF₄, ZrF₄/BaF₂, ZnCl₂ glasses and melts were prepared using an isothermal-isobaric molecular dynamics algorithm. The infrared spectra were then calculated by Fourier transforming the dipole moment autocorrelation functions of the basic structural units. The more ionic ZrF₄ based glasses showed good agreement with experimental data, whereas the covalently bonded ZnCl₂ glass did not. Addition of barium to ZrF₄ glass was found to reduce high frequency modes of vibration in the glass.
7
Xie, Sihan Ph D. Massachusetts Institute of Technology. "Development of colloidal quantum dot and lead halide perovskite light emitting devices." Thesis, Massachusetts Institute of Technology, 2021. https://hdl.handle.net/1721.1/130674.
Повний текст джерелаАнотація:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, February, 2021Cataloged from the official PDF of thesis. Page 139 blank.
Includes bibliographical references (pages 118-138).
In recent years, optically active semiconductors, such as organic molecules, colloidal quantum dots (QDs) and lead halide perovskites, have emerged as top candidates for light emitting materials. One key feature of these materials is their bandgap tunability, e.g. via size or chemical composition, allowing for their emission color to be turned throughout the entire visible spectrum. Thin-film light emitting devices (LEDs) based on these luminophores are promised to deliver the next-generation display technologies that are ultrathin and light, high-color-quality, and energy efficient with new form factors (e.g. foldable and flexible). In this thesis, we present the work performed to improve the understanding and performance of colloidal nanocrystal QDs and lead halide perovskites as visible luminophores in optically- and electrically-driven thin-film LEDs. First, we create an efficient voltage-controlled optical down-converter by operating a quantum dot light emitting diode (QD-LED) under reverse bias. Using field-induced luminescence quenching to our advantage, we show that a large electric field can strongly modify QD carrier dynamics, resulting in stable and reversible QD photoluminescence (PL) modulation. Next, we address the QD's toxicity issue by developing a synthesis of heavy-metal-free ZnSe/ZnS core-shell QDs with narrow spectral linewidth and high PL quantum yield. By employing these QDs as emitters, we demonstrate QD-LEDs with efficient and saturated blue electroluminescence (EL). Finally, we present a new way of depositing compact CsPbBr₃ perovskite thin films by thermal co-evaporation and demonstrate all vacuum-processed perovskite LEDs with efficient green EL emission. Our results show that evaporative deposition can be a viable alternative to solution-based deposition for fabricating high-quality perovskite thin films for LEDs.
by Sihan Xie.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Materials Science and Engineering
8
Chih-Hsiang, Yo. "The Synthesis Of High Surface Area Ti Sponges By Halide Conversion Process For Capacitor Anodes." Case Western Reserve University School of Graduate Studies / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=case1363107584.
Повний текст джерела
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Deng, Zeyu. "Rational design of novel halide perovskites combining computations and experiments." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/287932.
Повний текст джерелаАнотація:
The perovskite family of materials is extremely large and provides a template for designing materials for different purposes. Among them, hybrid organic-inorganic perovskites (HOIPs) are very interesting and have been recently identified as possible next generation light harvesting materials because they combine low manufacturing cost and relatively high power conversion efficiencies (PCEs). In addition, some other applications like light emitting devices are also highly studied. This thesis starts with an introduction to the solar cell technologies that could use HOIPs. In Chapter 2, previously published results on the structural, electronic, optical and mechanical properties of HOIPs are reviewed in order to understand the background and latest developments in this field. Chapter 3 discusses the computational and experimental methods used in the following chapters. Then Chapter 4 describes the discovery of several hybrid double perovskites, with the formula (MA)$_2$M$^I$M$^{III}$X$_6$ (MA = methylammonium, CH$_3$NH$_3$, M$^I$ = K, Ag and Tl, M$^{III}$ = Bi, Y and Gd, X = Cl and Br). Chapter 5 presents studies on the variable presure and temperature response of formamidinium lead halides FAPbBr$_3$ (FA = formamidinium, CH(NH$_2$)$_2$) as well as the mechanical properties of FAPbBr$_3$ and FAPbI$_3$, followed by a computational study connecting the mechanical properties of halide perovskites ABX$_3$ (A = K, Rb, Cs, Fr and MA, X = Cl, Br and I) to their electronic transport properties. Chapter 6 describes a study on the phase stability, transformation and electronic properties of low-dimensional hybrid perovskites containing the guanidinium cation Gua$_x$PbI$_{x+2}$ (x = 1, 2 and 3, Gua = guanidinium, C(NH$_2$)$_3$). The conclusions and possible future work are summarized in Chapter 7. These results provide theoreticians and experimentalists with insight into the design and synthesis of novel, highly efficient, stable and environmentally friendly materials for solar cell applications as well as for other purposes in the future.
10
Weber, Oliver. "Structural chemistry of hybrid halide perovskites for thin film photovoltaics." Thesis, University of Bath, 2018. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.761012.
Повний текст джерелаАнотація:
Hybrid lead halide perovskites, AMX 3 compounds in which A = CH 3 NH 3 (MA), CH(NH 2 ) 2(FA), Cs; M = Pb,Sn; X = I, Br, Cl, display remarkable performance in solution-processed optoelectronic devices, including > 22% efficient thin film photovoltaic cells. These compounds represent the first class of materials discovered to exhibit properties associated with high performance compound semiconductors, while being formed at or near room temperature using simple solution chemistry techniques. This thesis is focused on the synthesis, structural characterisation and phase behaviour of MAPbI 3 , FAPbI 3 , A-site solid solutions and novel organic metal halide framework materials. The complete atomic structure and phase behaviour of methylammonium lead iodide is elucidated for the first time, including hydrogen positions, using high flux, constant wave-length neutron powder diffraction. At 100 K an orthorhombic phase, space group Pnma, is observed, with the methylammonium cations ordered as the C–N bond direction alternates in adjacent inorganic cages. Above 165 K a first order phase transition to tetragonal, I4/mcm, occurs with the unlocking of cation rotation, which is disordered primarily in the ab plane. Above 327 K a cubic phase, space group Pm3m, is formed, with the cations isotropically disordered on the timescale of the crystallographic experiment. The high temperature phase of formamidinium lead iodide, α-FAPbI 3 is shown for the first time to be cubic, (Pm3m), at room temperature using time-of-flight, high resolution neutron powder diffraction. Polymorphism and the low temperature phase behaviour of FAPbI 3 have been further investigated using reactor and spallation neutron sources with high resolution in temperature. A tetragonal phase, P4/mbm, is confirmed in the temperature range 140-285 K.The composition, structural and optical parameters of ’A’ site solid solutions (MA/FA)PbI 3 have been investigated by single crystal X-ray diffraction, UV-vis spectroscopy and 1 H solution NMR. A composition-dependent transition in the crystal class from tetragonal to cubic(or pseudo-cubic) at room temperature is identified and correlated to trends in the optical absorption. Novel hybrid materials with inorganic frameworks of varying dimensionality from 0D to 2D, including imidazolium lead iodide and piperazinium lead iodide, have been synthesised using various templating organic cations and their atomic structures solved by single crystal X-ray diffraction.
11
Ngo, Thi Tuyen. "Analysis of the Interaction of Halide Perovskite with Other Materials and its Effect on the Performance of Optoelectronic Devices." Doctoral thesis, Universitat Jaume I, 2019. http://hdl.handle.net/10803/668130.
Повний текст джерелаАнотація:
Halide perovskites (HPs) have been demonstrated as promising materials for the preparation of efficient solar cells, LEDs and other optoelectronic devices. In addition, HPs can be prepared using low-cost techniques. However some issues such as low stability or hysteresis are hindering their commercialization. As illustrated, combining materials with different natures has been a successful strategy to develop new materials with enhanced properties. In this Doctoral Thesis we analysed the interaction of HPs with other materials, looking for the potential application. The results pointed out that (1) proper preparation of ETMs can significantly improve both the performance and long term stability of solar cells. (2) Better HP film quality can be achieved by combining HP with either QDs or organic molecules, resulting an enhancement in the device performance of solar cells, LEDs and light amplifiers. (3) New property, exciplex emission, can be obtained from the combination of HP and QDs.Las perovskitas de haluro (HP) han demostrado ser materiales prometedores para la preparación de células solares (CS), LED y otros dispositivos optoelectrónicos eficientes, utilizando técnicas de preparación de bajo costo. Empero, problemas como la baja estabilidad e histéresis obstaculizan su comercialización. Como se ilustra, la combinación de materiales con diferentes naturalezas es una estrategia exitosa para mejorar las propiedades. En esta Tesis Doctoral analizamos la interacción de los HP con otros materiales, buscando aplicaciones potenciales. Los resultados señalaron que (1) la preparación adecuada de ETM mejora significativamente tanto el rendimiento como la estabilidad a largo plazo de las CS. (2) Se puede lograr una mejor calidad de película HP combinando HP con QD o moléculas orgánicas, lo que resulta en una mejora en el rendimiento de CS, LED y amplificadores de luz. (3) Se puede obtener una nueva propiedad, la emisión de exciplex, de la combinación de HP y QD.
12
Khazaee, Maryam [Verfasser], and Doru C. [Akademischer Betreuer] Lupascu. "Materials for halide-based thin film solar cells / Maryam Khazaee ; Betreuer: Doru C. Lupascu." Duisburg, 2019. http://d-nb.info/1191714136/34.
Повний текст джерела
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Baker, Paul K. "Seven-coordinate halocarbonyl complexes of the type [MXY(CO)â†3(NCMEe)â†2] (M = Mo, W; X, Y = halide, pseudo halide) as highly versatile starting materials." Thesis, Bangor University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.395109.
Повний текст джерела
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Safdari, Majid. "Chemical Structure and Physical Properties of Organic-Inorganic Metal Halide Materials for Solid State Solar Cells." Doctoral thesis, KTH, Tillämpad fysikalisk kemi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-199951.
Повний текст джерелаАнотація:
Abstract Methylammonium lead (II) iodide has recently attracted considerable interest which may lead to substantial developments of efficient and inexpensive industrial photovoltaics. The application of this material as a light-absorbing layer in solid-state solar cells leads to impressive efficiency of over 22% in laboratory devices. However, for industrial applications, fundamental issues regarding their thermal and moisture stability need to be addressed. MAPbI3 belongs to the perovskite family of materials with the general formula ABX3 ,where is the organic cation (methylammonium) which is reported to be a major source of instability. In this work, a variety of alkyammonium lead (II) iodide materials have been synthesized by changing the organic cation, to study the relationship between the structural and physical properties of these materials. [(A)PbI3] and (A)PbI4 series were studied. Three dimensional (3D) networks (MAPbI3,MAPbBr3), two dimensional (2D) layered systems (BdAPbI4, HdAPbI4, OdAPbI4), and one dimensional (1D) columns (EAPbI3, PAPbI3, EAPb2I6) were found for the materials. [PbI6] octahedral structural units were repeated through the material network depending on the dimensionality and connectivity of the materials. Where a bulkier cation was introduced, the crystallographic unit cell increased in size which resulted in lower symmetry crystals. The connectivity of the unit cells along the material networks was found to be based on corner-sharing and face-sharing. Lower dimensionality resulted in larger bandgaps and lower photoconductivity, and hence a lower light conversion efficiency for the related solar cells. The thermal and moisture stability was greater in the 1D and 2D materials with bulkier organic cations than with methylammonium. In total, an overview is provided of the relationship between the chemical dimensionality and physical properties of the organic-inorganic lead halide materials with focus on the solar cell application.Svenska sammandrag: Metylammoniumbly(II)jodid har under de senaste åren genererat ett stort intresse som ett möjligt material for utveckling av effektiva och på industriell skala billiga solceller. Detta material har använts som ljusabsorberande skikt i fasta solceller med imponerande omvandlingseffektiviteter på över 22% för solceller i laboratorieskala. För att denna nya typ av solceller ska bli intressanta för produktion på industriell skala, så behöver grundläggande frågeställningar kring materialens stabilitet avseende högre temperaturer och fukt klargöras. MAPbI3 har formellt perovskitstruktur med den allmänna formel ABX3, där A utgörs av den organiska katjonen (metyammoniumjonen) och som kan kopplas till materialets instabilitet. I denna avhandling har olika alkylammoniumbly(II)jodidmaterial syntetiserats där den organiska katjonen modifierats med syftet att studera växelverkan mellan struktur och fysikaliska egenskaper hos de resulterande materialen. Material av olika dimensionalitet erhölls; tredimensionella (3D) nätverk (MAPbI3, MAPbBr3), tvådimensionella (2D) skiktade strukturer (BdAPbI4, HdAPbI4, OdAPbI4), och endimensionella (1D) kedjestrukturer (EAPbI3, PAPbI3, EAPb2I6). Flera nya lågdimensionella material (2D och 1D) tillverkats och karaktäriserats för första gången. Enkristalldiffraktometri har använts för att erhålla materialens atomära struktur. Strukturen hos material tillverkade i större mängder konfirmerades genom jämförelse mellan resultat från pulverdiffraktion och enkristalldiffraktion. Den oktaedriska strukturenheten [PbI6] utgör ett återkommande tema i materialen sammankopplade till olika dimensioner. Då större organiska katjoner används karaktäriseras i regel strukturerna av större enhetsceller och lägre symmetri. De lågdimensionella materialen ger typiskt störe elektroniskt bandgap, lägre fotoinducerad ledningsförmåga och därför sämre omvandlingseffektiviteter då de används i solceller. De lågdimensionella materialen (1D och 2D) som baseras på de större organiska katjonerna uppvisar bättre stabilitet med avseende på högre tempereratur och fukt. De tvådimensionella materialens elektroniska struktur har karaktäriserats med hjälp av röntegenfotoelektronspektroskopi, liksom röntgenabsorptions- och emissionsspektroskopi. Resultat från teoretiska beräkningar stämmer väl överens med de experimentella resultaten, och de visar att materialens valensband huvudsakligen består av bidrag från atomorbitaler hos jod, medan atomorbitaler från bly främst bidrar till edningsbandet. Sammantaget erbjuder avhandlingen en översikt av sambandet mellan kemisk dimensionalitet och fysikaliska egenskaper hos ett antal organiska/oorganiska blyhalogenidmaterial med fokus på tillämpning i solceller.
QC 20170123
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Cleaver, Patrick Joseph. "Electronic and Crystalline Characteristics of Mixed Metal Halide Perovskite Semiconductor Films." Wright State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=wright1547412870005544.
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Rathod, Siddharth Narendrakumar. "Structure Stability and Optical Response of Lead Halide Hybrid Perovskite Photovoltaic Materials: A First-Principles Simulation Study." Wright State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=wright1496189488934021.
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Vicente, Juvinch R. "Photo-driven Processes in Lead Halide Perovskites Probed by Multimodal Photoluminescence Microscopy." Ohio University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1585838644331732.
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Hettiarachchi, Chaminda Lakmal. "Organometal Halide Perovskite Solar Absorbers and Ferroelectric Nanocomposites for Harvesting Solar Energy." Scholar Commons, 2017. http://scholarcommons.usf.edu/etd/7034.
Повний текст джерелаАнотація:
Organometal halide perovskite absorbers such as methylammonium lead iodide chloride (CH3NH3PbI3-xClx), have emerged as an exciting new material family for photovoltaics due to its appealing features that include suitable direct bandgap with intense light absorbance, band gap tunability, ultra-fast charge carrier generation, slow electron-hole recombination rates, long electron and hole diffusion lengths, microsecond-long balanced carrier mobilities, and ambipolarity. The standard method of preparing CH3NH3PbI3-xClx perovskite precursors is a tedious process involving multiple synthesis steps and, the chemicals being used (hydroiodic acid and methylamine) are quite expensive. This work describes a novel, single-step, simple, and cost-effective solution approach to prepare CH3NH3PbI3-xClx thin films by the direct reaction of the commercially available CH3NH3Cl (or MACl) and PbI2. A detailed analysis of the structural and optical properties of CH3NH3PbI3-xClx thin films deposited by aerosol assisted chemical vapor deposition is presented. Optimum growth conditions have been identified. It is shown that the deposited thin films are highly crystalline with intense optical absorbance.
Charge carrier separation of these thin films can be enhanced by establishing a local internal electric field that can reduce electron-hole recombination resulting in increased photo current. The intrinsic ferroelectricity in nanoparticles of Barium Titanate (BaTiO3 -BTO) embedded in the solar absorber can generate such an internal field. A hybrid structure of CH3NH3PbI3-xClx perovskite and ferroelectric BTO nanocomposite FTO/TiO2/CH3NH3PbI3-xClx: BTO/P3HT/Cu as a new type of photovoltaic device is investigated. Aerosol assisted chemical vapor deposition process that is scalable to large-scale manufacturing was used for the growth of the multilayer structure. TiO2 and P3HT with additives were used as ETL and HTL respectively. The growth process of the solar absorber layer includes the nebulization of a mixture of PbI2 and CH3NH3Cl perovskite precursors and BTO nanoparticles dissolved in DMF, and injection of the aerosol into the growth chamber and subsequent deposition on TiO2. While high percentage of BTO in the film increases the carrier separation, it also leads to reduced carrier generation. A model was developed to guide the optimum BTO nanoparticle concentration in the nanocomposite films. Characterization of perovskite solar cells indicated that ferroelectric polarization of BTO nanoparticles leads to the increase of the width of depletion regions in the perovskite layer hence the photo current was increased by one order of magnitude after poling the devices. The ferroelectric polarization of BTO nanoparticles within the perovskite solar absorber provides a new perspective for tailoring the working mechanism and photovoltaic performance of perovskite solar cells.
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Puscher, Bianka [Verfasser], Dirk [Akademischer Betreuer] Guldi, and Dirk [Gutachter] Guldi. "Charge Carrier Diffusion and Transfer Mechanism in Hybrid Lead Halide Perovskite Materials / Bianka Puscher ; Gutachter: Dirk Guldi ; Betreuer: Dirk Guldi." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2020. http://d-nb.info/1203375379/34.
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PIPITONE, CANDIDA. "DESIGN, SYNTHESIS AND ATOMIC/ELECTRONIC STRUCTURAL ANALYSIS OF HYBRID HALIDE PSEUDO-PEROVSKITES: PERSPECTIVES AND OPEN ISSUES FOR NOVEL THERMOELECTRIC MATERIALS." Doctoral thesis, Università degli Studi di Palermo, 2022. http://hdl.handle.net/10447/533298.
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Kolodziej, Charles. "Laser Spectroscopic Studies of Ultrafast Charge Transfer Processes in Solar Cell Materials." Case Western Reserve University School of Graduate Studies / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=case1586371698913592.
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Austin, Michael. "An investigation of the processing and reconstruction conditions necessary to optimize the transmissin hologram images formed using conventinal silver halide materials." Thesis, University of Westminster, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.237408.
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Yu, Yue. "Thin Film Solar Cells with Earth Abundant Elements: from Copper Zinc Tin Sulfide to Organic-Inorganic Hybrid Halide Perovskite." University of Toledo / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1513289830601094.
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Liu, Shuhao. "Electronic Transport in Functional Materials and Two-Dimensional Hole System." Case Western Reserve University School of Graduate Studies / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=case1522893320666086.
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Hosseinian, Ahangharnejhad Ramez. "Fabrication of Perovskite Solar Cells & Applications in Multijunction Configurations." University of Toledo / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1575980394222122.
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Yang, Lei. "Hole Transport Materials for Solid-State Mesoscopic Solar Cells." Doctoral thesis, Uppsala universitet, Fysikalisk kemi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-232271.
Повний текст джерелаАнотація:
The solid-state mesoscopic solar cells (sMSCs) have been developed as a promising alternative technology to the conventional photovoltaics. However, the device performance suffers from the low hole-mobilities and the incomplete pore filling of the hole transport materials (HTMs) into the mesoporous electrodes. A variety of HTMs and different preparation methods have been studied to overcome these limitations. There are two types of sMSCs included in this doctoral thesis, namely solid-state dye-sensitized solar cells (sDSCs) and organometallic halide perovskite based solar cells. Two different types of HTMs, namely the small molecule organic HTM spiro-OMeTAD and the conjugated polymer HTM P3HT, were compared in sDSCs. The photo-induced absorption spectroscopy (PIA) spectra and spectroelectrochemical data suggested that the dye-dye hole conduction occurs in the absence of HTM and appears to be of significant importance to the contribution of hole transport. The PIA measurements and transient absorption spectroscopy (TAS) indicated that the oxidized dye was efficiently regenerated by a small molecule organic HTM TPAA due to its excellent pore filling. The conducting polymer P3HT was employed as a co-HTM to transfer the holes away from TPAA to prohibit the charge carrier recombination and to improve the hole transport. An alternative small molecule organic HTM, MeO-TPD, was found to outperform spiro-OMeTAD in sDSCs due to its more efficient pore filling and higher hole-mobility. Moreover, an initial light soaking treatment was observed to significantly improve the device performance due to a mechanism of Li+ ion migration towards the TiO2 surface. In order to overcome the infiltration difficulty of conducting polymer HTMs, a state-of-the-art method to perform in-situ photoelectrochemical polymerization (PEP) in an aqueous micellar solution of bis-EDOT monomer was developed as an environmental-friendly alternative pathway with scale-up potential for constructing efficient sDSCs with polymer HTMs. Three different types of HTMs, namely DEH, spiro-OMeTAD and P3HT, were used to investigate the influence of HTMs on the charge recombination in CH3NH3PbI3 perovskite based sMSCs. The photovoltage decay measurements indicate that the electron lifetime (τn) of these devices decreases by one order of magnitude in the sequence τspiro-OMeTAD > τP3HT > τDEH.
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FRANCESCHINI, PAOLO. "NOVEL SCHEMES FOR ULTRAFAST MANIPULATION OF QUANTUM MATERIALS." Doctoral thesis, Università Cattolica del Sacro Cuore, 2022. http://hdl.handle.net/10280/111822.
Повний текст джерелаАнотація:
La possibilità di controllare le proprietà elettroniche on-demand su una scala di tempo ultraveloce rappresenta una delle sfide più intriganti verso la realizzazione di dispositivi fotonici ed elettronici di nuova generazione. Stimolata da questo, negli ultimi decenni la ricerca scientifica ha concentrato la propria attenzione su diverse piattaforme a stato solido. Tra tutte, nanostrutture dielettriche (e metamateriali) e materiali correlati si presentano come i più promettenti candidati per la realizzazione di dispositivi dotati di nuove funzionalità. Al di là delle caratteristiche specifiche che rendono i dielettrici più adatti ad applicazioni in fotonica e i materiali correlati ai dispositivi elettronici, entrambe le categorie manifestano nuove funzionalità se soggetti ad uno stimolo esterno sotto forma di impulsi di luce con durata più breve della scala di tempo caratteristica del rilassamento dei gradi di libertà interni al sistema. Infatti, lo stato fuori equilibrio raggiunto a seguito di una foto-eccitazione presenta proprietà elettroniche ed ottiche di gran lunga differenti da quelle all'equilibrio. Pertanto, l'obiettivo di questo lavoro di tesi consiste nello sviluppo di nuovi metodi ed approcci sperimentali in grado di indurre, misurare e controllare nuove funzionalità in materiali complessi su una scala di tempo ultraveloce.The possibility to control the electronic properties on-demand on an ultrafast time scale represents one of the most exciting challenges towards the realization of new generation photonic and electronic devices. Triggered by this, in the last decades the research activity focused its attention to different solid-state platforms. Among all, dielectric nanostructures (and metamaterials) and correlated materials represent the most promising candidate for the implementation of devices endowed by new functionalities. Apart from the specific features making dielectrics more suitable for photonic applications and correlated materials for electronic devices, both categories exhibit new functionalities if subjected to an external stimulus in the form of excitation light pulses shorter than the relaxation timescale of the internal degrees of freedom of the system. Indeed, the out-of-equilibrium state achieved upon photoexcitation exhibits electronic and optical properties highly different from those at equilibrium. Therefore, the aim of this thesis work consists in the development of new methods and experimental approaches capable to induce, measure, and control new functionalities in complex materials on an ultrafast time scale.
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Linaburg, Matthew Ronald. "Studies of Halide Perovskites CsPbX3, RbPbX3 (X=Cl-, Br-, I-), and Their Solid Solutions." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1449074303.
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Ahmed, Ejaz, and Michael Ruck. "Chemistry of polynuclear transition-metal complexes in ionic liquids." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-138716.
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Transition-metal chemistry in ionic liquids (IL) has achieved intrinsic fascination in the last few years. The use of an IL as environmental friendly solvent, offers many advantages over traditional materials synthesis methods. The change from molecular to ionic reaction media leads to new types of materials being accessible. Room-temperature IL have been found to be excellent media for stabilising transition-metal clusters in solution and to crystallise homo- and heteronuclear transition-metal complexes and clusters. Furthermore, the use of IL as solvent provides the option to replace high-temperature routes, such as crystallisation from the melt or gas-phase deposition, by convenient room- or low-temperature syntheses. Inorganic IL composed of alkali metal cations and polynuclear transition-metal cluster anions are also known. Each of these areas will be discussed briefly in this contributionDieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich
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Dsouza, Brendan Harry. "Material Degradation Studies in Molten Halide Salts." Diss., Virginia Tech, 2021. http://hdl.handle.net/10919/103052.
Повний текст джерелаАнотація:
This study focused on molten salt purification processes to effectively reduce or eliminate the corrosive contaminants without altering the salt's chemistry and properties. The impurity-driven corrosion behavior of HAYNES® 230® alloy in the molten KCl-MgCl2-NaCl salt was studied at 800 ºC for 100 hours with different salt purity conditions. The H230 alloy exhibited better corrosion resistance in the salt with lower concentration of impurities. Furthermore, it was also found that the contaminants along with salt's own vaporization at high temperatures severely corroded even the non-wetted surface of the alloy. The presence of Mg in its metal form in the salt resulted in an even higher mass-loss possibly due to Mg-Ni interaction. The study also investigated the corrosion characteristics of several nickel and ferrous-based alloys in the molten KCl-MgCl2-NaCl salt. The average mass-loss was in the increasing order of C276 < SS316L < 709-RBB* < IN718 < H230 < 709-RBB < 709-4B2. The corrosion process was driven by the outward diffusion of chromium. However, other factors such as the microstructure of the alloy i.e. its manufacturing, refining, and heat-treatment processes have also shown to influence the corrosion process. Lowering the Cr content and introducing W and Mo in the alloy increased its resistance to corrosion but their non-uniform distribution in the alloy restricted its usefulness. To slow-down the corrosion process, and enhance the material properties, selected alloys were boronized and tested for their compatibility in the molten KCl-MgCl2-NaCl salt. The borided alloys exhibited better resistance to molten salt attack, where the boride layer in the exposed alloy was still intact, non-porous, and strongly adhered to the substrate. The alloys also did not show any compensation in their properties (hardness). It was also found that the boride layer always composed of an outermost silicide composite layer, which is also the weakest and undesired layer as it easily cracks, breaks, or depletes under mechanical and thermal stresses. Various different grades of "virgin" nuclear graphites were also tested in the molten KF-UF4-NaF salt to assist in the selection of tolerable or impermeable graphites for the MSR operational purposes. It was found that molten salt wettability with graphite was poor but it still infiltrated at higher pressure. Additionally, the infiltration also depended on the pore-size and porosity of the graphite. The graphite also showed severe degradation or disintegration of its structure because of induced stresses.Doctor of Philosophy
Molten salts are considered as potential fuel and coolant candidates in MSRs because of their desirable thermophysical properties and heat-transfer capabilities. However, they pose grave challenges in material selection due to their corrosive nature, which is attributed to the impurities and their concentration (mostly moisture and oxygen-based) in the salt. This study focused on purifying the salt to reduce these contaminants without compromising its composition and properties. The influence of purification processes on the corrosion behavior of HAYNES® 230® alloy was studied in the molten chloride salt with different purity conditions. Various nickel and ferrous-based alloys were also studied for their compatibility in the molten chloride salt. This will assist in expediting the material selection process for various molten salt applications. It was observed that several factors such as alloy composition, its microstructure, impurities in the salt attribute to molten salt corrosion. It was also quite evident that corrosion in molten salts is inevitable and hence, the focus was shifted on slowing down this process by providing protective barriers in the form of coatings (i.e. boronization). The borided (coated) alloys not only improved the corrosion resistance but also enhanced and retained their properties like hardness after exposure to molten salts. Since these studies were conducted under static conditions, a more detailed investigation is needed for the selected alloys by subjecting them to extreme flow-conditions and for longer a duration of time. To achieve this objective, a forced circulation molten salt loop was designed and fabricated to conduct flow corrosion studies for alloys in molten chloride salt. Graphite is another critical component of the MSR where it is used as a moderator or reflector. Generally, molten salts exhibit poor wettability with graphite, but they can still infiltrate (graphites) at higher applied pressures, and result in the degradation or disintegration of graphite's structure, and eventually its failure in the reactor. This study provides infiltration data, and understanding of the degradation of various 'virgin' nuclear graphite grades by the molten fluoride salt. This should assist in the selection of tolerable or impermeable graphite grades for MSR operational purposes.
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Ahmed, Ejaz, and Michael Ruck. "Chemistry of polynuclear transition-metal complexes in ionic liquids." Royal Society of Chemistry, 2011. https://tud.qucosa.de/id/qucosa%3A27774.
Повний текст джерелаАнотація:
Transition-metal chemistry in ionic liquids (IL) has achieved intrinsic fascination in the last few years. The use of an IL as environmental friendly solvent, offers many advantages over traditional materials synthesis methods. The change from molecular to ionic reaction media leads to new types of materials being accessible. Room-temperature IL have been found to be excellent media for stabilising transition-metal clusters in solution and to crystallise homo- and heteronuclear transition-metal complexes and clusters. Furthermore, the use of IL as solvent provides the option to replace high-temperature routes, such as crystallisation from the melt or gas-phase deposition, by convenient room- or low-temperature syntheses. Inorganic IL composed of alkali metal cations and polynuclear transition-metal cluster anions are also known. Each of these areas will be discussed briefly in this contribution.Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
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Gretton, Geoffrey B. "Use of an incorporated hardening developer to produce a phase modulated hologram in a silver halide material /." Online version of thesis, 1989. http://hdl.handle.net/1850/11358.
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Galvagno, Erica <1998>. "A study on lead halide perovskites: preparation and characterization." Master's Degree Thesis, Università Ca' Foscari Venezia, 2022. http://hdl.handle.net/10579/21967.
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This work deals with all-inorganic lead halide perovskite (LHP) nanocrystals and it mainly focuses on two different synthetic approaches. The first one is the conventional hot injection method where the reaction is conducted at high temperature and inert atmosphere. Instead, the second approach is a synthesis done at room temperature and developed to overcome some of the issues characterizing the hot injection method. In fact, the possibility to work at a lower temperature and atmospheric condition allows to utilize a greater amount of precursors, which could be useful for the possible scaling up of the whole process. Moreover, the approach developed into this thesis aims at improving some specific aspects among otherwise well-established room temperature procedures. To this purpose, the solvents generally used for synthesis at room temperature have been substituted with water and citric acid has been employed both as capping ligand and to control the pH of the solution to avoid the formation of lead hydroxide. The products obtained by both synthetic routes have been characterized by x-ray diffraction and electron microscopy. The characterization is mostly focused on the compounds obtained using the room temperature approach since this one is partly new and has not been previously inspected, so a wider comprehension of the obtained morphologies is required.
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Kuvayskaya, Anastasia, and Aleksey Vasiliev. "Use of Suzuki Coupling Reaction for Synthesis of Functionalized Materials." Digital Commons @ East Tennessee State University, 2019. https://dc.etsu.edu/asrf/2019/schedule/162.
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Hybrid materials synthesized by grafting of organic molecules onto silica surface have found numerous applications in chemistry, biochemistry, and chemical engineering. In particular, the functionalization of silica gel can be accomplished by various surface reactions of immobilized boronic acids. Suzuki coupling has been chosen due to several advantages, such as mild reaction conditions, tolerance to the aqueous environment, and high yields of the products. The objective of this work was to determine the most effective reaction conditions for modifying porous hybrid materials with large specific surface areas and high density of surface organoboron reactive sites by various functional groups. Prior to modification by Suzuki coupling, the surface of silica gel was functionalized by phenylboronic acid. Two methods were tested for immobilization of phenylboronic acid: hydrosilylation and thiol-ene coupling. The later radical reaction between surface alkylthiol groups and 4-vinylphenylboronic acid was found more effective. Obtained boronated silica gel was used for further functionalization by various aryl halides. Surface Suzuki coupling reaction was catalyzed by palladium acetate in the presence of cesium carbonate as a base, while dimethylformamide was chosen as a solvent. The coupling reactions proceeded at mild heating under constant sonication. Such ultrasonic irradiation was reported earlier to have an activating effect on Suzuki coupling. The analysis of the obtained products indicated formation of surface biaryl compounds, the highest yields have been obtained in reactions with iodobenzene and bromobenzene. Thus, novel functionalized organic/inorganic hybrid materials were successfully synthesized by surface modification of mesoporous silica gel.
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DHANABALAN, BALAJI. "Developing Metal-Halide Layered Perovskite Nanomaterials for Optoelectronics." Doctoral thesis, Università degli studi di Genova, 2021. http://hdl.handle.net/11567/1041905.
Повний текст джерелаАнотація:
The abundant chemical tunability along with outstanding optoelectronic properties of the 2D metal-halide layered perovskite materials, as well as the potential prospect on understanding the structure-property relationships at the molecular level, provide enormous opportunity for the scientific community on designing new and efficient 2D metal-halide layered perovskites for a specific optoelectronic application. These materials still require attention on understanding their fundamental electronic properties and on controlling their synthesis parameters to produce high quality materials. Moreover, the synergy between the organic and inorganic compounds in these systems further opens up the possibility to unlock novel optoelectronic properties by simply integrating many other available functional organic molecules into these structures. This thesis is dedicated to the synthesis of 2D lead-bromide Ruddlesden Popper layered perovskite materials through a simple synthesis technique and by using different organic molecules. It targets a full investigation of the photo-physical properties of the as synthesized materials. Moreover, it presents detailed studies on the effect of structural rigidity and electron-phonon interaction provided by organic molecules on the emission efficiencies of 2D layered perovskites, and their emission tunability by using organic molecules with different architectures. In a more technological view, this thesis summarizes the work performed on the integration of 2D layered perovskites in polymer films and their emission enhancement by mechanical stress.
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Stricker, Elizabeth Ann. "Cuprous Bromide Electrochemistry and its Application in a Flow Battery." Case Western Reserve University School of Graduate Studies / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=case1546604124529032.
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Sale, Martin William Briddon. "The assessment of the photo response efficiency of the silver halide component in a photo-thermographic material." Thesis, University of Westminster, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263935.
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AN, NGOC MAI. "Development of synthesis strategies for efficient, robust, and stable light - emitting nanocomposites based on halide perovskites." Doctoral thesis, Università degli studi di Genova, 2021. http://hdl.handle.net/11567/1047167.
Повний текст джерелаАнотація:
Over the past few years, halide perovskites have generated extensive interest as potential materials for various applications, such as light-emitting diodes, displays, detectors, and tracking (e.g., bio-applications or oil tracing). However, the effective implementation of these halide perovskite NCs in industrial manufacturing processes is limited by their poor stability under various conditions: when exposed to humidity, high temperature, and photo-irradiation, the NCs quickly degrade. Therefore, the research work included in this thesis is mainly focused on developing various strategies to improve the stability of halide perovskite NCs with the aim of implementing them in practical applications. Among different matrix encapsulation materials for perovskites (such as polymers, inorganic metal oxide/halides, and metal-organic framework), silica has been chosen as an efficient matrix to protect halide perovskite NCs due to its excellent properties, which include high optical transparency in the visible, chemical stability, abundance, non-toxicity, and low-cost. Two novel approaches to produce CsPbX3 NCs embedded in silica are developed as simple and straightforward methods via sol-gel route and molten salt synthesis. The resulting composites are investigated on structure, optical properties and their stability against environment conditions. As a proof of concept, these composites are also tested in some application such as down-converter phosphors in light-emitting diode and tracer in oil industry. In an addition work, the structure and optical properties of Sn-based perovskite materials, which are synthesized by hot-injection method, are also discussed, extending the scope of this thesis to non-toxic lead-free perovskite materials.
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Liu, Tianyu. "Perovskite Solar Cells fabrication and Azobenzene Perovskite synthesis: a study in understanding organic-inorganic hybrid lead halide perovskite." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1576840261464488.
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Tang, Xiaofeng [Verfasser], Tobias [Akademischer Betreuer] Unruh, Christoph [Gutachter] Brabec, and Dai [Gutachter] Zhang. "Investigation on the material stability of metal-halide perovskite semiconductors / Xiaofeng Tang ; Gutachter: Christoph Brabec, Dai Zhang ; Betreuer: Tobias Unruh." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2019. http://d-nb.info/1184023808/34.
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Grimm, Judith. "New light emitting materials : synthesis, optical spectroscopy, photon upconversion and photoionization in Ni²+, Ce³+ and Tm²+ doped halides /." [S.l.] : [s.n.], 2006. http://www.zb.unibe.ch/download/eldiss/06grimm_j.pdf.
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Phung, Thi Thuy Nga [Verfasser], Dieter [Akademischer Betreuer] Neher, Antonio [Akademischer Betreuer] Abate, and Iván [Akademischer Betreuer] Mora-Seró. "Defect chemistry in halide perovskites : material characterisation and device integration / Thi Thuy Nga Phung ; Dieter Neher, Antonio Abate, Iván Mora-Seró." Potsdam : Universität Potsdam, 2020. http://d-nb.info/1219911461/34.
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Shahrezaei, Khashayar, and Edvin Öberg. "Evaluation Methods for Friction Materials in a Four-Wheel Drive Drivetrain." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-70776.
Повний текст джерелаАнотація:
BorgWarner located in Landskrona are developing components for the four-wheeldrive drivetrain that are being massed produced in the automotive industry. Thanks to Borg- Warner’s unique product’s properties they have achieved a worldwide leading position as a provider of systems for advanced four-wheeldrive drivetrain (all-wheel drivetrain). The assignment from the BorgWarner is to create a better understanding about when vibrations occur and what properties of a friction disc affect vibrations in the wet clutch. The goals of this thesis are to: Map system parameters like Surface topografy. Measure pressure distribution between the friction discs. Measure the Youngs modulus, also known as stiffness. It is not sure that a bad pressure distribution could cause vibrations in the wet clutch. The results from the topography explain the appearance of the pressure distribution. Varying stiffness means that the density of the material is also varying because the stiffness depends on the material composition. When forces are applied on the friction disc, it leads to varying deformation on samples. When the samples all deforms different, the result of the different deformation could be slanting surface. When a disc with non- parallel friction surface rotates it could generate vibration in the wet clutch.
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Tant, Joseph. "The influence of second phases on the microstructural evolution and the mechanical properties of geological materials." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/the-influence-of-second-phases-on-the-microstructural-evolution-and-the-mechanical-properties-of-geological-materials(d51de894-09a3-413e-adf7-ca2dc7788ced).html.
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Polycrystalline geological materials are not normally single phase materials and commonly contain second phases which are known to influence the grain size and mechanical properties of bulk material. Despite the well documented significance of second phases, there are relatively few detailed systematic experimental studies of the effect of second phases on isostatic high temperature grain growth in geological materials. Grain growth is a process that is fundamental to our understanding of how rocks behave in the lower crust / upper mantle where grain size is considered to play an important role in the localization of deformation in addition to determining the strength of materials at these pressure and temperature conditions. Furthermore, the effect that the spatial distribution and grain size of the second phases have on the mechanical properties of rocks is generally acknowledged, but it is not well constrained. Spatial variation is particularly significant in geological systems where a strength contrast exists between phases. With these two things in mind, a two-part study is presented in which the influence of a pore second phase on the microstructural evolution of halite during grain growth (Part I), and the influence of a calcite second phase on the mechanical behaviour of two phase calcite + halite aggregates (Part II), is investigated. In Part I, high temperature (330 °-600 °C), high confining pressure (200 MPa) isostatic grain growth experiments were carried out on 38-125 μm reagent grade halite (99.5%+ NaCl) powder over durations of 10 secs up to 108 days. After hot-pressing, the halite displays a foam texture. Some porosity remained along the grain boundaries, the size and distribution of which appears to impact significantly on the resulting grain size, growth mechanism and kinetics of halite grain growth. Halite grain growth was found to be well described by the normal grain growth equation: d^(1/n)-d0^(1/n)=k0(t-t0)exp(-H/RT) where t is the duration of the growth period, t0 is the time at which normal growth begins, d is the grain size, d0 is the grain size at t0, k0 is a constant, H is the activation enthalpy for the growth controlling process, R is the universal gas constant,T is temperature and n is a growth constant. At 330 °-511 °C, the data is best described by n = 0.25 indicating growth controlled by surface diffusion around pores that lie on the grain boundaries. An activation enthalpy of 122±34 kJ/mol was obtained using the grain size data from these data sets. At 600 °C the data is best described by n = 0.5, suggesting that a transition to interface controlled growth takes place between 511 °C and 600 °C. To investigate the impact of porosity, the Zener parameter (Z = pore size/pore volume fraction) was determined for individual grains in 10 samples. A general trend of increasing with increasing halite grain size is observed, indicating pore elimination keeps pace with pore accumulation in the growing grains. In some samples, the largest grains display a decrease in the Zener parameter corresponding with an increase in pore volume fraction. These grains are interpreted as having experienced a short-lived, abnormal growth phase shortly after t0 during which pore accumulation outpaced pore elimination. A model of pore controlled grain growth is proposed with a view to explaining these observations. In Part II, calcite + halite aggregates of constant volume fraction (0.60 calcite : 0.40 halite) and varying calcite clast size (6 μm 361 μm) were axially deformed to <1% bulk strain at room temperature in a neutron diffraction beamline. Elastic strain and stress in each phase was determined as a function of load from the neutron diffraction data. The strain (and stress) behaviour correlates well with the microstructural parameters: 1) halite mean free path and 2) calcite contiguity. Both phases behaved elastically up to aggregate axial stresses of 20-37 MPa, above these stresses the halite yielded plastically while the calcite remained elastic. Once yielding began, the rate of enhanced load transfer from halite to calcite with increasing applied load decreased with halite mean free path and increased calcite with contiguity. A Hall-Petch relationship between halite mean free path and aggregate yield stress was observed.
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Wang, Kai. "HIGH PERFORMANCE SOLUTION-PROCESSED PEROVSKITE HYBRIDSOLAR CELLS THROUGH DEVICE ENGINEERING AND NOVEL." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1489066286671653.
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Song, Zhaoning. "Solution Processed High Efficiency Thin Film Solar Cells: from Copper Indium Chalcogenides to Methylammonium Lead Halides." University of Toledo / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1470403462.
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Kaloyanova, Valentina B. "Structural Modeling and Optimization of a Joined-Wing Configuration of a High-Altitude Long-Endurance (HALE) Aircraft." University of Cincinnati / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1259075776.
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BRUNI, CLAUDIA. "ANALYSIS OF SLENDER PIEZOELECTRIC WING CONFIGURATIONS FOR ENERGY HARVESTING: AEROELASTIC MODELING AND EXPERIMENTAL COMPARISONS." Doctoral thesis, Politecnico di Torino, 2016. http://hdl.handle.net/11583/2652663.
Повний текст джерелаАнотація:
The study of the aeroelastic behavior of slender piezoelectric wings gains its relevance within the design perimeter of High Altitude Long Endurance (HALE) aircraft, or more in general of energy independent systems. As a matter of fact, the exploitation of new energy sources, without implying any direct penalization of the flight performances nor of the original aircraft design concept, is particularly appealing for HALE unmanned air vehicles (UAVs). Long range missions entail several design requirements such as high aspect ratio wing and low zero fuel weight, both with the common objective of reducing the energy consumption. However, albeit the structural design challenges afforded during the last years to increase as much as possible the mission duration of HALE aircraft, satellite systems still remain the most effective solution for ground surveillance purposes. Therefore, having additional energy from alternative sources, such as from structural vibrations, has to be embraced as a mission evolution opportunity for HALE UAV. The research activity presented in this thesis aims at investigating the energy extraction, via the application of piezoelectric patches over the wings' surface, from the most commons aeroelastic phenomena: critical flutter, sub-critical and super-critical LCOs, and gust response. For the sake of the just mentioned study, a nonlinear analytical and numerical aeroelastic piezoelectric wing model, which includes geometrical nonlinearities up to the third order and a multi-modal approach, was developed. The importance of higher order nonlinear terms is furthermore investigated via a comparison with FEM and experimental results. The numerical results, in agreement with the experimental results, shown that when the wing undergoes to high static deformations a state of dynamical instabilities may settle at speed even 50% lower than the critical flutter speed, and, in particular, when the oscillation amplitude becomes high, the model has to include higher order nonlinear terms to correctly capture the real oscillation amplitude. The results in terms of energy harvesting from the gust induced vibrations shown that the Squared gust seemed to be more effective for energy harvesting purposes than the 1-Cosine, if compared on the base of the energy content subtended by each curve of the gust profiles. Furthermore, although the 1-Cosine appeared less effective in terms of the amount of power that it can provide to the wing for energy harvesting, it was identified an optimal value of gust penetration gradient at which the assumed piezoelectric wing was able to extract the maximum amount of energy. Finally, thanks to the modal shaker and wind tunnel tests campaign, the importance of the location of the piezoelectric patches over the wing with respect to its dynamical response was investigated. What was seen is that the amount of extractable energy, at LCO, from the second bending mode of the wing is higher than that extractable from the first bending mode and it increases if the piezo-patches are slightly moved towards the wing center. This results suggest the necessity to develop a piezoelectric wing with multiple piezoelectric patches properly located in order to extract energy from the higher number of modes, or simply to the most excited mode, according to the good knowledge of the operational wing dynamic behavior. The order of magnitude of the maximum instantaneous power extracted from the assumed model during LCOs is of 10 mW, a good result if compared to the power demand of modern electronic devices.
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Kirsch, Bertrand. "Apport de l'anisotropie des matériaux composites aux performances aéroélastiques des ailes à grand allongement de drones HALE." Thesis, Aix-Marseille, 2019. http://www.theses.fr/2019AIXM0230.
Повний текст джерелаАнотація:
L'idée d'un drone solaire haute altitude disposant d'une endurance virtuellement infinie, uniquement limitée par des questions de maintenance, fait sont chemin au sein de la communauté aéronautique. Toutefois, en raison de la faible puissance fournie par l'énergie solaire, ce concept nécessite l'utilisation d'une voilure à grand allongement très légère et donc très souple, ce qui la rend vulnérable à des phénomènes d'instabilités destructeurs comme le flottement ou la divergence en torsion. Ces travaux consistent à développer un code de calcul adapté à la physique complexe d'un tel aéronef, permettant d'exploiter les spécificités des matériaux composites pour éviter la présence de ces instabilités dans le domaine de vol. En complément de cas tests issus de la littérature, une campagne d'essais en soufflerie a été menée pour valider la performance du programme. Pour finir, sa capacité à être utilisé au sein d'une plateforme d'optimisation a été illustrée à travers un cas simple de plaque souple compositeThe idea of high altitude solar drones, with a virtually infinite endurance, only restrained by maintenance issues, gain ground in the aviation community. However, because of the low on-board power, this concept implies to design a very lightweight high aspect-ratio wing which is very flexible and then vulnerable to destructive instabilities like flutter or torsional divergence. This work consists in developing a computation code, namely GEBTAero, suitable for this type of airframe, allowing to exploit composite materials specificity to avoid such instabilities in the flight domain. Besides literature test cases, a wind tunnel campaign is conducted in order to validate the program performances. Lastly, its ability to be used within an optimisation framework is assessed with a simple shape composite flat plate
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Morrisey, Bryan J. "Multidisciplinary Design Optimization of an Extreme Aspect Ratio HALE UAV." DigitalCommons@CalPoly, 2009. https://digitalcommons.calpoly.edu/theses/113.
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ABSTRACT
Multidisciplinary Design Optimization of an Extreme Aspect Ratio HALE UAV
Bryan J. Morrisey
Development of High Altitude Long Endurance (HALE) aircraft systems is part of a vision for a low cost communications/surveillance capability. Applications of a multi payload aircraft operating for extended periods at stratospheric altitudes span military and civil genres and support battlefield operations, communications, atmospheric or agricultural monitoring, surveillance, and other disciplines that may currently require satellite-based infrastructure. Presently, several development efforts are underway in this field, including a project sponsored by DARPA that aims at producing an aircraft that can sustain flight for multiple years and act as a pseudo-satellite. Design of this type of air vehicle represents a substantial challenge because of the vast number of engineering disciplines required for analysis, and its residence at the frontier of energy technology.
The central goal of this research was the development of a multidisciplinary tool for analysis, design, and optimization of HALE UAVs, facilitating the study of a novel configuration concept. Applying design ideas stemming from a unique WWII-era project, a “pinned wing” HALE aircraft would employ self-supporting wing segments assembled into one overall flying wing. The research effort began with the creation of a multidisciplinary analysis environment comprised of analysis modules, each providing information about a specific discipline. As the modules were created, attempts were made to validate and calibrate the processes against known data, culminating in a validation study of the fully integrated MDA environment. Using the NASA / AeroVironment Helios aircraft as a basis for comparison, the included MDA environment sized a vehicle to within 5% of the actual maximum gross weight for generalized Helios payload and mission data. When wrapped in an optimization routine, the same integrated design environment shows potential for a 17.3% reduction in weight when wing thickness to chord ratio, aspect ratio, wing loading, and power to weight ratio are included as optimizer-controlled design variables.
Investigation of applying the sustained day/night mission requirement and improved technology factors to the design shows that there are potential benefits associated with a segmented or pinned wing. As expected, wing structural weight is reduced, but benefits diminish as higher numbers of wing segments are considered. For an aircraft consisting of six wing segments, a maximum of 14.2% reduction in gross weight over an advanced technology optimal baseline is predicted.