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Mavroidis, Constantinos. "Electron transport in GaN epitaxial layers." Thesis, University College London (University of London), 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.407135.
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Kusumawati, Yuly. "Oxide and composite electron transport layers for efficient dye-sensitized solar cells." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066240/document.
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Trois types des ETLs ont été développés et étudiés dans cette travaille comme une photoélectrode dans la cellule solaire à colorant (DSSC). Ils sont composés de (1) deux types de nanoparticules de TiO2-brookite, (2) le composite d'anatase et graphène et (3) la nanoparticule de ZnO qui a nanobâtonnet structure, respectivement. Toutes photoélectrodes sont préparées par le technique « doctor blade ». La morphologie des photoélectrodes ont été caractérisées par microscopie électronique à transmission (MET) et microscopie électronique à balayage (MEB). Les épaisseurs de couche sont mesurées en utilisant la profilométrie. Pour les films caractérisations structurelles, une haute résolution diffractomètre à rayons X a été utilisée. La spectroscopie infrarouge à transformée de Fourier (FTIR) et micro-Raman ont été effectués pour vérifier la préparation composite TiO2_Gr. Les propriétés des films optiques ont été enregistrées avec un spectrophotomètre équipé d'une sphère d'intégration de techniques. Les performances de cellules ont été obtenues en mesurant les courbes IV des cellules sous illumination calibré. Pour atteindre une compréhension profonde du fonctionnement de la cellule, la spectroscopie d'impédance (IS) technique a été étudiée sur une grande gamme de potentiel appliquée. En faisant est l'étude, la structure électronique, porteurs de charge à vie (tn), le transport / heure de collecte (ttr) et les paramètres de transport d'électrons des couches ont été déterminées. L'étude soin de leurs propriétés a révélé non seulement leurs avantages mais aussi leur limitation. Cette information sera bénéfique comme une considération pour les travaux futursThree kinds of ETL have been developed and studied in this present work as a photoelectrode in DSSC. Those composed of (1) two kinds of TiO2-brookite nanoparticles, (TiO2_B1 and TiO2_B2), (2) the composite of anatase and graphene (TiO2_Gr) and (3) the nanorods like ZnO nanoparticles (ZnO_NR), respectively. All photoelectrode are prepared by doctor blading technique. The morphology of photoelectrodes have been characterized using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The layer thicknesses were measured using profilometry. For the film structural characterizations, a high-resolution X-ray diffractometer was used. The Fourier transform infrared (FTIR) and micro Raman measurement have been carried out to verify the TiO2_Gr composite preparation. The optical film properties (total transmission and total reflection) were recorded with a spectrophotometer equipped with an integrating sphere techniques. The cell performances were obtained by measuring the I-V curves of the cells under calibrated illumination. To achieve an in-deep understanding of the cell functioning, the impedance spectroscopy (IS) technique has been studied over a large applied potential range. By doing IS study, the electronic structure, charge carrier lifetime (tn), transport/collection time (ttr) and electron transport parameters of the layers have been determined. The carefully study of their properties has revealed not only their advantages but also their limitation. This information will be beneficial as a consideration for the future work
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Tambwe, Kevin. "P- and e- type Semiconductor layers optimization for efficient perovskite photovoltaics." University of Western Cape, 2019. http://hdl.handle.net/11394/7414.
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>Magister Scientiae - MScPerovskite solar cells have attracted a tremendous amount of research interest in the scientific community recently, owing to their remarkable performance reaching up to 22% power conversion efficiency (PCE) in merely 6 to 7 years of development. Numerous advantages such as reduced price of raw materials, ease of fabrication and so on, have contributed to their increased popularity.
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Bradley, Colin. "Understanding Charge Transport and Selectivitiy in Ionically Functionalized Fullerenes for Electron-Selective Interfacial Layers." Thesis, University of Oregon, 2018. http://hdl.handle.net/1794/23171.
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Significant improvements in power conversion efficiency (>10%) of emerging thin-film photovoltaics have been achieved in the last 5 years. High efficiencies would not be possible without the development of new selective interfacial layers. However, a complete understanding of how interfacial layers function to improve the selectivity of charge extracting contacts in thin-film photovoltaics is still being sought. The goal of this work is to contribute to the understanding of the operation of selective interfacial layers based on the study of ionically functionalized fullerenes. Just as other ionically functionalized materials have shown promise as electron-selective interfacial layers in organic photovoltaics and mixed organic-inorganic halide perovskites, Chapter II demonstrates the utility of ionically functionalized fullerenes. High performing solar cells necessitate the use of conductive interfacial layers; anomalously high conductivity in ionically functionalized materials, which have been used as interfacial layers, has been ascribed to self-doping. This work demonstrates that less than 1% of an ionically functionalized fullerene is reduced in its highly conductive pristine state and is concurrent with the presence of distinct chemical species. These studies describe how the chemical origin of the high conductivity of ionically functionalized fullerenes does not require the invocation of direct anion reduction or significant chemical transformations such as Hofmann-like elimination reactions occurring to a stoichiometric degree. This work also addresses the question of how the selectivity of a charge extracting contact is improved by the presence of an interfacial layer. The quantification of energy barrier reduction, which is often discussed in terms of work function modification or energy-level alignment, is demonstrated using metal|semiconductor junctions modified with an ionically functionalized fullerene. The barrier height of high work function electrodes was reduced significantly, by as much as 0.45 V, and was correlated to thin (2–5 nm) portions of the film rather than fullerene aggregates. The studies that comprise this work form a coherent model for understanding the key factors that have resulted in the continued use of ionically functionalized interfacial layers, their high conductivity, and energy barrier modification of the charge extracting electrodes. This dissertation contains coauthored, previously published, and unpublished work.10000-01-01
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Rushforth, Andrew William. "The transport properties of two dimensional electron gases in spatially random magnetic fields." Thesis, University of Nottingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342029.
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Schubert, Marcel. "Elementary processes in layers of electron transporting Donor-acceptor copolymers : investigation of charge transport and application to organic solar cells." Phd thesis, Universität Potsdam, 2014. http://opus.kobv.de/ubp/volltexte/2014/7079/.
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Donor-acceptor (D-A) copolymers have revolutionized the field of organic electronics over the last decade. Comprised of a electron rich and an electron deficient molecular unit, these copolymers facilitate the systematic modification of the material's optoelectronic properties. The ability to tune the optical band gap and to optimize the molecular frontier orbitals as well as the manifold of structural sites that enable chemical modifications has created a tremendous variety of copolymer structures. Today, these materials reach or even exceed the performance of amorphous inorganic semiconductors. Most impressively, the charge carrier mobility of D-A copolymers has been pushed to the technologically important value of 10 cm^{2}V^{-1}s^{-1}. Furthermore, owed to their enormous variability they are the material of choice for the donor component in organic solar cells, which have recently surpassed the efficiency threshold of 10%.
Because of the great number of available D-A copolymers and due to their fast chemical evolution, there is a significant lack of understanding of the fundamental physical properties of these materials. Furthermore, the complex chemical and electronic structure of D-A copolymers in combination with their semi-crystalline morphology impede a straightforward identification of the microscopic origin of their superior performance. In this thesis, two aspects of prototype D-A copolymers were analysed. These are the investigation of electron transport in several copolymers and the application of low band gap copolymers as acceptor component in organic solar cells.
In the first part, the investigation of a series of chemically modified fluorene-based copolymers is presented. The charge carrier mobility varies strongly between the different derivatives, although only moderate structural changes on the copolymers structure were made. Furthermore, rather unusual photocurrent transients were observed for one of the copolymers. Numerical simulations of the experimental results reveal that this behavior arises from a severe trapping of electrons in an exponential distribution of trap states. Based on the comparison of simulation and experiment, the general impact of charge carrier trapping on the shape of photo-CELIV and time-of-flight transients is discussed.
In addition, the high performance naphthalenediimide (NDI)-based copolymer P(NDI2OD-T2) was characterized. It is shown that the copolymer posses one of the highest electron mobilities reported so far, which makes it attractive to be used as the electron accepting component in organic photovoltaic cells.par
Solar cells were prepared from two NDI-containing copolymers, blended with the hole transporting polymer P3HT. I demonstrate that the use of appropriate, high boiling point solvents can significantly increase the power conversion efficiency of these devices. Spectroscopic studies reveal that the pre-aggregation of the copolymers is suppressed in these solvents, which has a strong impact on the blend morphology.
Finally, a systematic study of P3HT:P(NDI2OD-T2) blends is presented, which quantifies the processes that limit the efficiency of devices. The major loss channel for excited states was determined by transient and steady state spectroscopic investigations: the majority of initially generated electron-hole pairs is annihilated by an ultrafast geminate recombination process. Furthermore, exciton self-trapping in P(NDI2OD-T2) domains account for an additional reduction of the efficiency. The correlation of the photocurrent to microscopic morphology parameters was used to disclose the factors that limit the charge generation efficiency. Our results suggest that the orientation of the donor and acceptor crystallites relative to each other represents the main factor that determines the free charge carrier yield in this material system. This provides an explanation for the overall low efficiencies that are generally observed in all-polymer solar cells.Donator-Akzeptor (D-A) Copolymere haben das Feld der organischen Elektronik revolutioniert. Bestehend aus einer elektronen-reichen und einer elektronen-armen molekularen Einheit,ermöglichen diese Polymere die systematische Anpassung ihrer optischen und elektronischen Eigenschaften. Zu diesen zählen insbesondere die optische Bandlücke und die Lage der Energiezustände. Dabei lassen sie sich sehr vielseitig chemisch modifizieren, was zu einer imensen Anzahl an unterschiedlichen Polymerstrukturen geführt hat. Dies hat entscheidend dazu beigetragen, dass D-A-Copolymere heute in Bezug auf ihren Ladungstransport die Effizienz von anorganischen Halbleitern erreichen oder bereits übetreffen. Des Weiteren lassen sich diese Materialien auch hervorragend in Organischen Solarzellen verwenden, welche jüngst eine Effizienz von über 10% überschritten haben. Als Folge der beträchtlichen Anzahl an unterschiedlichen D-A-Copolymeren konnte das physikalische Verständnis ihrer Eigenschaften bisher nicht mit dieser rasanten Entwicklung Schritt halten. Dies liegt nicht zuletzt an der komplexen chemischen und mikroskopischen Struktur im Film, in welchem die Polymere in einem teil-kristallinen Zustand vorliegen. Um ein besseres Verständnis der grundlegenden Funktionsweise zu erlangen, habe ich in meiner Arbeit sowohl den Ladungstransport als auch die photovoltaischen Eigenschaften einer Reihe von prototypischen, elektronen-transportierenden D-A Copolymeren beleuchtet. Im ersten Teil wurden Copolymere mit geringfügigen chemischen Variationen untersucht. Diese Variationen führen zu einer starken Änderung des Ladungstransportverhaltens. Besonders auffällig waren hier die Ergebnisse eines Polymers, welches sehr ungewöhnliche transiente Strom-Charakteristiken zeigte. Die nähere Untersuchung ergab, dass in diesem Material elektrisch aktive Fallenzustände existieren. Dieser Effekt wurde dann benutzt um den Einfluss solcher Fallen auf transiente Messung im Allgemeinen zu beschreiben. Zusätzlich wurde der Elektronentransport in einem neuartigen Copolymer untersucht, welche die bis dato größte gemesse Elektronenmobilität für konjugierte Polymere zeigte. Darauf basierend wurde versucht, die neuartigen Copolymere als Akzeptoren in Organischen Solarzellen zu implementieren. Die Optimierung dieser Zellen erwies sich jedoch als schwierig, konnte aber erreicht werden, indem die Lösungseigenschaften der Copolymere untersucht und systematisch gesteuert wurden. Im Weiteren werden umfangreiche Untersuchungen zu den relevanten Verlustprozessen gezeigt. Besonders hervorzuheben ist hier die Beobachtung, dass hohe Effizienzen nur bei einer coplanaren Packung der Donator/Akzeptor-Kristalle erreicht werden können. Diese Struktureigenschaft wird hier zum ersten Mal beschrieben und stellt einen wichtigen Erkenntnisgewinn zum Verständnis von Polymersolarzellen dar.
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Allen, William D. "Aspects of spin polarised transport." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368082.
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Schubert, Marcel [Verfasser], and Dieter [Akademischer Betreuer] Neher. "Elementary processes in layers of electron transporting Donor-acceptor copolymers : investigation of charge transport and application to organic solar cells / Marcel Schubert. Betreuer: Dieter Neher." Potsdam : Universitätsbibliothek der Universität Potsdam, 2014. http://d-nb.info/1052682847/34.
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Whitfield, Thomas Britain. "An analysis of copper transport in the insulation of high voltage transformers." Thesis, University of Surrey, 2001. http://epubs.surrey.ac.uk/843581/.
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Examination of the paper insulation and copper stress braiding during stripdown of a number of Current Transformers (FMK type 400kV) has revealed the presence of dark deposits. Copper foils are often interspersed within layers of paper insulation and mineral oil found in transformer windings. The dark deposits were often found in association with these foils, affecting several layers of paper in addition to the layer in contact with the copper foil. This thesis describes the research undertaken to identify these deposits and establish a mechanism for the transportation through the paper layers. Preliminary investigation using scanning electron microscopy (SEM) in conjunction with energy dispersive X-ray analysis (EDX) has shown these dark deposits to be copper based. X-ray photoelectron spectroscopy was used to show that the transport of the copper deposit through the paper insulation was working under the influence of a diffusion controlled process, related to Fick's law. Laboratory studies in support of work designed to eliminate the problem have shown that corrosion of copper occurs in mineral oils containing a trace of oxygen. This corrosion is non protective in character and leads to migration of copper into adjacent layers of paper. It has been shown that the transport of copper through several layers of paper can be measured by XPS and that the concentration from one paper winding to the next declines in accord with Fick's law for non-steady state diffusion. Measurements of surface concentrations by XPS correlate well with measurements made with atomic absorption spectroscopy on solutions of extracts of the contaminated paper. The laboratory measurements have allowed determination of the diffusion coefficients and activation energy for the transport process and thus give a basis for interpretation of the diffusion profiles found in the transformer in terms of time and temperature of operation. The diffusion process is temperature dependant. The results have been used to produce long term prediction curves.
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Aversa, Pierfrancesco. "Primary Defects in Halide Perovskites : Effect on Stability and Performance for Photovoltaic Applications Effect of organic PCBM Electron transport Layers on natural and post-irradiation ageing of optical absorption and emission in methyl ammonium lead triiodide spin –coated on p-i-n Solar Sell Substrates Effect of organic PCBM Electron transport Layers on natural and post-irradiation ageing of optical absorption and emission in triple cation lead mixed halide perovskite spin –coated on p-i-n Solar Sell Substrates Electron Irradiation Induced Ageing Effects on Radiative Recombination Properties of methylammonium lead triiodide layers on p-i-n solar cell substrates Electron Irradiation Induced Ageing Effects on Methylammonium Lead Triiodide Based p-i-n Solar Cells Electron Irradiation Induced Ageing Effects on Radiative Recombination Properties of Quadruple Cation Organic-Inorganic Perovskite Layers." Thesis, Institut polytechnique de Paris, 2020. http://www.theses.fr/2020IPPAX050.
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Ces onze dernières années ont vu apparaitre les pérovskites organiques inorganiques hybrides (HOIPs) comme un passionnant domaine de recherche pour leur application potentielle dans les technologies du photovoltaïque (PV) en raison de leurs exceptionnelles propriétés optoélectroniques et de leur facilité de mise en oeuvre. Cependant, les matériaux HOIPs ont plusieurs inconvénients dont leur manque de stabilité en conditions opérationnelles. Améliorer celle-ci est l'un des plus grands défis à relever avant commercialisation. La formule générale est (A1,A2,A3,A4)Pb(X1,X2)3, où les sites A occupés par une distribution de 1 à 4 cations métalliques/organiques et les sites X par celle d’anions halogénures. Les défauts lacunaires natifs sont considérés comme une cause possible de dégradation des cellules solaires HOIPs. L'objectif de ce travail est de comprendre le rôle des défauts dans la stabilité à long terme des matériaux PV HOIPs. A cette fin, des défauts primaires ont été introduits de manière contrôlée par irradiation avec des électrons de haute énergie (1MeV) dans des lots de couches et cellules solaires (SCs) à base de divers composés HOIPs. Il s'agit notamment du prototype PV HOIPs, MAPbI3 (A1PbX13), et de nouveaux composés mixtes d’halogénures à triple ou quadruple cations, (CsMAFA)Pb(I1-xBrx)3 (A3PbX23) ou (GACsMAFA)Pb(I1-yBry)3 (A4PbX23). Les couches sont fabriquées selon la même procédure que les couches actives SCs et, ensuite, traitées dans des conditions similaires. Pour A1PbX13/A3PbX23, la structure SC est de type p-i-n avec des couches organiques pour le transport des trous et des électrons (HTL/ETL). Les couches sont déposées sur le substrat verre/ITO/HTL (PEDOT:PSS) sans ou avec couche supérieure ETL (PCBM). Pour A4PbX23, la structure SC est de type n-i-p avec des couches ETL inorganiques (TiO2) et HTL organiques (Spiro-OMeTAD). Les couches sont directement déposées sur du verre.La spectroscopie d'annihilation de positons donne une évidence directe de l'existence de défauts lacunaires natifs et induits par irradiation dans chaque composé. Les spectres d’absorbance en fonction de l’énergie montrent que le vieillissement naturel et après irradiation génère différentes populations de défauts dans chaque composé. De plus, celles-ci pour A1PbX13 et A3PbX23 diffèrent selon l'absence ou la présence de la couche supérieure ETL. Les populations de défauts évoluent pendant au moins 3 mois. Le vieillissement modifie (i) la bande interdite, (ii) les queues de bande de conduction/valence et (iii) l'absorption optique via des niveaux électroniques profonds. Les effets d’illumination sous laser varient aussi en fonction du vieillissement. L’asymétrie des pics de photoluminescence (PL) dans chaque composé sous illumination laser continue reflète une superposition de raies d’émission gaussiennes à énergie, FWHM et hauteur évoluant avec le temps d'illumination. Les transitions d'émission impliquent des niveaux électroniques localisés peu profonds dans A3PbX23/A4PbX23 et résonnants dans A1PbX13. De tels effets durent au moins 3 mois dans A4PbX23. Ces niveaux électroniques sont attribués à des populations de défauts spécifiquement induits par illumination. Le vieillissement naturel et après irradiation donne des spectres PL à décroissance temporelle résolue en une ou deux exponentielles. Le nombre et la durée de vie sont fortement influencés par l’irradiation initiale et la composition. Une amélioration frappante du fonctionnement PV pour le type SC p-i-n est induite par le vieillissement dû à l'irradiation. Le rendement quantique externe et les performances PVs ont des valeurs plus élevées pour l’état irradié que de référence durant 6 à 12 mois de vieillissement. Cela prouve que l'ingénierie des défauts par irradiation d'électrons à haute énergie a le potentiel de fournir des voies de traitement innovantes pour améliorer la stabilité à long terme des performances photovoltaïques HOIPsDuring the last eleven years, Hybrid Organic Inorganic Perovskites (HOIPs) materials have emerged as an exciting topic of research for potential application in solar cell technologies due to their outstanding optoelectronic properties and processing advantages. However, HOIPs materials suffer from several drawbacks with, in peculiar, their lack of stability under operational conditions (light, bias, environment…). To improve this stability is one of the biggest challenges to be addressed before commercialization. The general formula for HOIPs is (A1,A2,A3,A4)Pb(X1,X2)3, where the A sites can be occupied by a distribution of 1 to 4 metallic/organic cations and X sites with halide anions. The role of native vacancy defects has been questioned as a possible cause for HOIPs solar cells degradation. The aim of this work is to understand the defect role in long term stability of HOIPs materials for photovoltaics. For this reason, primary defects were introduced in a controlled way via high energy electron irradiation (1MeV) in sets of layers and solar cells (SCs) fabricated using various HOIPs compounds. Those include the photovoltaic HOIPs prototype, MAPbI3 (A1PbX13), and emergent triple or quadruple cation mixed halide HOIPs, (CsMAFA)Pb(I1-xBrx)3 (A3PbX23) or (GACsMAFA)Pb(I1-yBry)3 (A4PbX23). The HOIPs layers are fabricated according to the same procedure as the HOIPs active SC layers and, subsequently, treated in similar conditions. For A1PbX13 and A3PbX23, the solar cells are of the p-i-n structure with organic hole and electron transport layer (HTL/ETL). The HOIPs layers are deposited on the glass/ITO/HTL (PEDOT:PSS) substrate without or with the top ETL layer (PCBM). For A4PbX23, the solar cells are of the n-i-p type with inorganic ETL (TiO2) and organic HTL (Spiro-OMeTAD) layers. The layers are directly deposited on glass without the ETL layer.Positron Annihilation Spectroscopy (PAS) gives direct evidence for native vacancy-type defects and irradiation induced ones in layers of each HOIP compound. The energy dependence of absorbance shows that natural and after irradiation ageing generates different defect populations in each HOIP compound. These populations strikingly also differ depending on the absence or presence of the top ETL layer for the A1PbX13 and A3PbX23 compounds. The defect populations evolve over ageing duration as long as 3 months. The prominent effects of ageing include (i) band gap modification, (ii) tailing of conduction/valence band extrema and (iii) optical absorption via deep subgap electronic levels. Illumination effects under laser also vary with ageing for each HOIP compound. Asymmetric photoluminescence (PL) peaks in each compound under continuous laser illumination reflect that radiative emission involves Gaussian emission rays with energy, FWHM and height evolving with illumination time. The emission transitions involve shallow localized electronic levels in A3PbX23 and A4PbX23 and resonant ones in A1PbX13. These electronic levels are attributed to specifically illumination-induced defect populations. Natural and after irradiation ageing result in PL decay lifetime spectra resolved into one or two exponential decay components. The decay components number and lifetime are strongly affected by the initial production of irradiation defects and HOIPs composition. Such effects last over 3 months at least in A4PbX23. The p-i-n solar cells exhibit most striking irradiation ageing induced photovoltaics performance. The External Quantum Efficiency (EQE versus photon energy) and the photovoltaic performance (I-V under illumination) of the irradiated solar cells have higher values than those in the reference SCs after 6 to 12 months of ageing. This gives evidence that defect engineering via high energy electron irradiation has a potential for providing innovative processing pathways to enhance the long-term stability of HOIPs photovoltaic performance
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Hu, Zhelu. "Investigations towards more performing and more stable solution-processed hybrid perovskite solar cells." Electronic Thesis or Diss., Sorbonne université, 2020. http://www.theses.fr/2020SORUS329.
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Dans cette thèse de doctorat, je me suis concentré sur l'optimisation et les stratégies concernant la couche de transport d'électrons (ETL), la couche active à base de pérovskite hybride et leurs interfaces dans les cellules solaires fonctionnelle,de pérovskite. En ce qui concerne l'étude des ETL, j'ai réalisé deux travaux : l'un porte sur la comparaison d'une architecture simplifiée de cellules solaires planaires à base de pérovskite sans ETL avec celle d'un ETL plan en TiO2 (décrit au chapitre 2) ; un autre travail porte sur la comparaison des cellules solaires à base de pérovskite avec des nanocolonnes de Ti02(NA) orientées à celles comportant simplement une ETL de TiO2 plane et non nanostructurée (chapitre 3). Lors des recherches sur la couche active de pérovskite, la pérovskite à cations mixtes et aux halogénures mixtes a été utilisée,dans trois axes de travail distincts. J'ai tout d'abord optimisé et maximisé la taille des grains de la couche active de pérovskite (chapitre 2). Ensuite, j'ai étudié des films de pérovskite hybride nano-structurés et leur amélioration au niveau de la collection de la lumière (chapitre 6). J'ai aussi étudié les propriétés thermiques des films minces de pérovskite à cation mixte et j'ai notamment déterminé leur conductivité et leur diffusivité thermique. L'étude contribue à comprendre leur meilleure stabilité thermique par rapport aux pérovskite à base d'iodure de plomb de méthylammonium (MAPbI3) (voir chapitre 4). Enfin, j'ai étudié les méthodes de passivation pour atténuer la recombinaison de la charge interfaciale et pour améliorer la stabilité des cellules solaires de pérovskite (chapitre 5)In this Ph.D. thesis,I have been focused to investigate optimizations and strategies concerning the electron transportlayer (ETL),the hybrid perovskite active layer, and their interfaces in functional perovskite solar cells. On the investigatior of ETLs, I have performed two works: One is on the comparison of a simplified ETL-free planar perovskite solar cells,architecture to that with a planar TiO2 ETL (described in Chapter 2); Another work is on the comparison of perovskite,solat cells with well-oriented one-dimension TiO2 nanocolumn (NA) ETL to those with a planar TiO2 ETL (Chapter 3).On,the investigations of the perovskite active layer, mixed-cation and mixed-halide perovskite was applied into three,relevant works: (1) I optinized and maximized the grain size of the perovskite active layer (Chapter 2); (2) I studied nano-,structured hybrid perovskite fims and their light-harvesting enhancement (Chapter 6): (3) I investigated the thermal,properties of mixed-cation perovskite thin films to understand their improved thermal stability compared to,methylammonium lead iodide (MAPbi3) perovskite (Chapter 4). In addition, I studied passivation methods to alleviate the interfacial charge recombination and to improve the stability of perovskite solar cells (chapter 5)
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Cupido, Ian Patrick. "Nitrogen and argon treatment of titanium dioxide nanowire arrays." University of Western Cape, 2021. http://hdl.handle.net/11394/8040.
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>Magister Scientiae - MScTiO2 nanoparticle films are important electron transport layers (ETLs) in photovoltaics such as dye-sensitised, perovskite and polymer hetero-junction solar cells. These films, however, have significant electron trap-sites as a result of the large density of oxygen vacancies present in nano-sized TiO2. These trap-sites cause electron-hole recombination and ultimately lower photon-to-current conversion efficiency of the underlying cell during operation. Doping the TiO2 lattice with low atomic number elements such as nitrogen is a proven method to overcoming the charge transport inefficiency of TiO2 ETLs; another is the use of one-dimensional (1D) nanowires (NWs), instead of nanoparticles.
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Pawar, Krantikumar Subhash. "Ab Initio Modeling of an Electron Transport Layer Interface in Hybrid Perovskite Solar Cells." Wright State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=wright1610125331928229.
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Sugiura, Kenji, Hiromichi Ohta, Shin-ichi Nakagawa, Rong Huang, Yuichi Ikuhara, Kenji Nomura, Hideo Hosono, and Kunihito Koumoto. "Anisotropic carrier transport properties in layered cobaltate epitaxial films grown by reactive solid-phase epitaxy." American Institite of Physics, 2009. http://hdl.handle.net/2237/12628.
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Widmer, Johannes. "Charge transport and energy levels in organic semiconductors." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-154918.
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Organic semiconductors are a new key technology for large-area and flexible thin-film electronics. They are deposited as thin films (sub-nanometer to micrometer) on large-area substrates. The technologically most advanced applications are organic light emitting diodes (OLEDs) and organic photovoltaics (OPV). For the improvement of performance and efficiency, correct modeling of the electronic processes in the devices is essential. Reliable characterization and validation of the electronic properties of the materials is simultaneously required for the successful optimization of devices. Furthermore, understanding the relations between material structures and their key characteristics opens the path for innovative material and device design. In this thesis, two material characterization methods are developed, respectively refined and applied: a novel technique for measuring the charge carrier mobility μ and a way to determine the ionization energy IE or the electron affinity EA of an organic semiconductor. For the mobility measurements, a new evaluation approach for space-charge limited current (SCLC) measurements in single carrier devices is developed. It is based on a layer thickness variation of the material under investigation. In the \"potential mapping\" (POEM) approach, the voltage as a function of the device thickness V(d) at a given current density is shown to coincide with the spatial distribution of the electric potential V(x) in the thickest device. On this basis, the mobility is directly obtained as function of the electric field F and the charge carrier density n. The evaluation is model-free, i.e. a model for μ(F, n) to fit the measurement data is not required, and the measurement is independent of a possible injection barrier or potential drop at non-optimal contacts. The obtained μ(F, n) function describes the effective average mobility of free and trapped charge carriers. This approach realistically describes charge transport in energetically disordered materials, where a clear differentiation between trapped and free charges is impossible or arbitrary. The measurement of IE and EA is performed by characterizing solar cells at varying temperature T. In suitably designed devices based on a bulk heterojunction (BHJ), the open-circuit voltage Voc is a linear function of T with negative slope in the whole measured range down to 180K. The extrapolation to temperature zero V0 = Voc(T → 0K) is confirmed to equal the effective gap Egeff, i.e. the difference between the EA of the acceptor and the IE of the donor. The successive variation of different components of the devices and testing their influence on V0 verifies the relation V0 = Egeff. On this basis, the IE or EA of a material can be determined in a BHJ with a material where the complementary value is known. The measurement is applied to a number of material combinations, confirming, refining, and complementing previously reported values from ultraviolet photo electron spectroscopy (UPS) and inverse photo electron spectroscopy (IPES). These measurements are applied to small molecule organic semiconductors, including mixed layers. In blends of zinc-phthalocyanine (ZnPc) and C60, the hole mobility is found to be thermally and field activated, as well as increasing with charge density. Varying the mixing ratio, the hole mobility is found to increase with increasing ZnPc content, while the effective gap stays unchanged. A number of further materials and material blends are characterized with respect to hole and electron mobility and the effective gap, including highly diluted donor blends, which have been little investigated before. In all materials, a pronounced field activation of the mobility is observed. The results enable an improved detailed description of the working principle of organic solar cells and support the future design of highly efficient and optimized devicesOrganische Halbleiter sind eine neue Schlüsseltechnologie für großflächige und flexible Dünnschichtelektronik. Sie werden als dünne Materialschichten (Sub-Nanometer bis Mikrometer) auf großflächige Substrate aufgebracht. Die technologisch am weitesten fortgeschrittenen Anwendungen sind organische Leuchtdioden (OLEDs) und organische Photovoltaik (OPV). Zur weiteren Steigerung von Leistungsfähigkeit und Effizienz ist die genaue Modellierung elektronischer Prozesse in den Bauteilen von grundlegender Bedeutung. Für die erfolgreiche Optimierung von Bauteilen ist eine zuverlässige Charakterisierung und Validierung der elektronischen Materialeigenschaften gleichermaßen erforderlich. Außerdem eröffnet das Verständnis der Zusammenhänge zwischen Materialstruktur und -eigenschaften einen Weg für innovative Material- und Bauteilentwicklung. Im Rahmen dieser Dissertation werden zwei Methoden für die Materialcharakterisierung entwickelt, verfeinert und angewandt: eine neuartige Methode zur Messung der Ladungsträgerbeweglichkeit μ und eine Möglichkeit zur Bestimmung der Ionisierungsenergie IE oder der Elektronenaffinität EA eines organischen Halbleiters. Für die Beweglichkeitsmessungen wird eine neue Auswertungsmethode für raumladungsbegrenzte Ströme (SCLC) in unipolaren Bauteilen entwickelt. Sie basiert auf einer Schichtdickenvariation des zu charakterisierenden Materials. In einem Ansatz zur räumlichen Abbildung des elektrischen Potentials (\"potential mapping\", POEM) wird gezeigt, dass das elektrische Potential als Funktion der Schichtdicke V(d) bei einer gegebenen Stromdichte dem räumlichen Verlauf des elektrischen Potentials V(x) im dicksten Bauteil entspricht. Daraus kann die Beweglichkeit als Funktion des elektrischen Felds F und der Ladungsträgerdichte n berechnet werden. Die Auswertung ist modellfrei, d.h. ein Modell zum Angleichen der Messdaten ist für die Berechnung von μ(F, n) nicht erforderlich. Die Messung ist außerdem unabhängig von einer möglichen Injektionsbarriere oder einer Potentialstufe an nicht-idealen Kontakten. Die gemessene Funktion μ(F, n) beschreibt die effektive durchschnittliche Beweglichkeit aller freien und in Fallenzuständen gefangenen Ladungsträger. Dieser Zugang beschreibt den Ladungstransport in energetisch ungeordneten Materialien realistisch, wo eine klare Unterscheidung zwischen freien und Fallenzuständen nicht möglich oder willkürlich ist. Die Messung von IE und EA wird mithilfe temperaturabhängiger Messungen an Solarzellen durchgeführt. In geeigneten Bauteilen mit einem Mischschicht-Heteroübergang (\"bulk heterojunction\" BHJ) ist die Leerlaufspannung Voc im gesamten Messbereich oberhalb 180K eine linear fallende Funktion der Temperatur T. Es kann bestätigt werden, dass die Extrapolation zum Temperaturnullpunkt V0 = Voc(T → 0K) mit der effektiven Energielücke Egeff , d.h. der Differenz zwischen EA des Akzeptor-Materials und IE des Donator-Materials, übereinstimmt. Die systematische schrittweise Variation einzelner Bestandteile der Solarzellen und die Überprüfung des Einflusses auf V0 bestätigen die Beziehung V0 = Egeff. Damit kann die IE oder EA eines Materials bestimmt werden, indem man es in einem BHJ mit einem Material kombiniert, dessen komplementärer Wert bekannt ist. Messungen per Ultraviolett-Photoelektronenspektroskopie (UPS) und inverser Photoelektronenspektroskopie (IPES) werden damit bestätigt, präzisiert und ergänzt. Die beiden entwickelten Messmethoden werden auf organische Halbleiter aus kleinen Molekülen einschließlich Mischschichten angewandt. In Mischschichten aus Zink-Phthalocyanin (ZnPc) und C60 wird eine Löcherbeweglichkeit gemessen, die sowohl thermisch als auch feld- und ladungsträgerdichteaktiviert ist. Wenn das Mischverhältnis variiert wird, steigt die Löcherbeweglichkeit mit zunehmendem ZnPc-Anteil, während die effektive Energielücke unverändert bleibt. Verschiedene weitere Materialien und Materialmischungen werden hinsichtlich Löcher- und Elektronenbeweglichkeit sowie ihrer Energielücke charakterisiert, einschließlich bisher wenig untersuchter hochverdünnter Donator-Systeme. In allen Materialien wird eine deutliche Feldaktivierung der Beweglichkeit beobachtet. Die Ergebnisse ermöglichen eine verbesserte Beschreibung der detaillierten Funktionsweise organischer Solarzellen und unterstützen die künftige Entwicklung hocheffizienter und optimierter Bauteile
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Sanderson, Douglas Grant. "An investigation of the relationship between the structure and function of the blue copper electron transport protein plastocyanin using thin-layer, steady-state spectroelectro-chemistry /." The Ohio State University, 1985. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487262513407884.
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Chikara, Shalinee. "A SYSTEMATIC STUDY OF THERMODYNAMIC AND TRANSPORT PROPERTIES OF LAYERED 4D AND 5D CORRELATED ELECTRON SYSTEMS." UKnowledge, 2011. http://uknowledge.uky.edu/gradschool_diss/843.
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Correlated electron materials have been at the forefront of condensed matter research in the past couple of decades. Correlation in materials, especially, with open d and f electronic shells often lead to very exciting and intriguing phenomenon like high temperature superconductivity, Mott metal-insulator transition, colossal magnetoresistance (CMR). This thesis focuses on triple-layered Sr4Ru3O10, Sr substituted double layered (Ca1-- xAx)3Ru2O7 (A = Ba, Sr) and 5d system Sr2IrO4 and Sr3Ir2O7. Triple-layered Sr4Ru3O10 displays interesting phenomena ranging from quantum oscillations, tunneling magnetoresistance, unusual low temperature specific heat, strong spin-lattice coupling to switching behavior. The central feature, however, is the unique borderline magnetism: along the c-axis. Sr4Ru3O10 shows spontaneous ferromagnetism, indicating a strong Coulomb exchange interaction, U and a large density of states at the Fermi surface, g(EF ), hence Ug(EF ) ≥ 1 (Stoner criterion). But within the ab-plane it features a pronounced peak in magnetization and a first-order metamagnetic transition. The coexistence of the interlayer ferromagnetism and the intralayer metamagnetism makes Sr4Ru3O10 a really unique system. Also, in this thesis the spin-valve behavior exhibited by impurity doping at the Ca site by Ba and Sr in the double layered Ca3Ru2O7 is reported. Spin valve effect is a phenomenon only realized in multilayer thin films. Here, spin valve is observed in bulk single crystals of impurity dopedCa3Ru2O7, Ca3(Ru1-xCrx)2O7 and (Ca1- xAx)3Ru2O7 (A = Ba, Sr). 5d Iridates are expected to be more metallic and less magnetic than their 3d and 4f counterparts because of the extended 5d orbitals. In marked contrast, many iridates are magnetic insulators with exotic properties. The focus in this thesis is on Sr2IrO4 which diplays a novel Jeff = 1/2 Mott state. Magnetic, electrical, and thermal measurements on single-crystals of Sr2IrO4, reveal a novel giant magneto-electric effect (GME) arising from a frustrated magnetic/ferroelectric state. The GME and electric polarization hinge on a spin-orbit gapping of 5d-bands, rather than the magnitude and spatial dependence of magnetization, as traditionally accepted.
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Ali, Fawad. "Investigation of metal oxides thin films developed by PVD system for perovskite solar cells." Thesis, Queensland University of Technology, 2019. https://eprints.qut.edu.au/127139/1/Fawad_Ali_Thesis.pdf.
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This research presents thin film deposition and characterization of metal oxides using industrially viable Physical Vapour Deposition (PVD) techniques. The research examines low temperature processed electron and hole transport metal oxides for high performance and stable perovskite solar cells. The physical, chemical, optical and electronic properties of the films were investigated and their device performance has been evaluated. The performance of the device improved and the materials cost reduced by replacing the expansive organic materials with more stable inorganic metal oxides.
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Matta, Sri Kasi Venkata Nageswara Rao. "Computational exploration of two-dimensional (2D) materials for solar energy applications." Thesis, Queensland University of Technology, 2019. https://eprints.qut.edu.au/134244/1/Sri%20Kasi%20Venkata%20Nageswara%20Rao%20Matta%20Thesis_Redacted.pdf.
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This project is to find innovative and alternate Nano-sized materials for solar energy applications. This include conversion of solar light energy into electricity or generate clean environment friendly fuels by breaking water into Oxygen and Hydrogen. The study has explored material characteristics at electronic level to reveal new properties. These revelations then compared amongst some of the organic and inorganic materials for the intended purpose. Innovative design of new carbon-compounds (termed as carbon Quantum dots) included in the study for use in the new generation Perovskite solar cells for charge transfer.
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Fournier, Olivier. "Synthèse par ALD et caractérisation de couches extractrices d'électrons pour application dans les cellules solaires à base de pérovskite." Electronic Thesis or Diss., Université Paris sciences et lettres, 2021. http://www.theses.fr/2021UPSLC025.
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L'intérêt éveillé par les cellules solaires à base de pérovskite dans la communauté photovoltaique (PV) est allé grandissant ces 10 dernières années, dû notamment aux excellentes propriétés opto-électroniques de ces matériaux, à la diversité de leurs applications potentielles et à leur attractivité économique.Cette technologie est attendue sur le marché du PV d'ici 2023, mais certains défis tels que la stabilité des cellules ou le passage à l'échelle industrielle restent à relever afin de garantir son industrialisation.Une stratégie consiste à optimiser les couches extractrices de charge qui doivent garantir une bonne sélectivité vis-à-vis des porteurs de charge et assurer une bonne interface avec la pérovskite.Le dépôt chimique en phase vapeur à flux alternés (Atomic Layer Deposition - ALD) est une méthode de dépôt industrielle permettant la synthèse de nombreux matériaux.Les films minces déposés par ALD sont denses, homogènes, sans piqûres, conformes, et leur épaisseur et leur composition peuvent être contrôlées à l'échelle nanométrique.L'ALD apparait donc comme un candidat idéal pour déposer ces couches extractrices de charge.Cette thèse s'est intéressée au développement et à la caractérisation de divers oxydes par ALD.Le SnO2 et le TiO2 ont été développés à l'Institut Photovoltaïque d'Île-de-France (IPVF) à partir de deux procédés pour chaque matériau.A partir des caractérisations des couches minces obtenues, un procédé a été retenu pour chaque matériau en vue d'une intégration dans un dispositif PV en tant que couches inorganiques extractrices d'électrons.L'intégration d'une couche compacte de TiO2-ALD (15 nm) dans une architecture mésoporeuse a été démontrée, et ses propriétés comparées à la couche compacte standard déposée par pyrolyse d'aérosol.Des efficacités de conversion similaires de 19% ont été montrées, ainsi qu'une meilleure homogénéité engendrant une meilleure reproductibilité des résultats; ce moyen de dépôt est maintenant utilisé pour les cellules de référence à l'IPVF.L'intégration du SnO2-ALD est aussi présentée.Une couche de 10 nm de SnO2 a montré des efficacités moyennes dues à un déficit dans le facteur de forme.L'ajout d'une couche organique a résolu ce problème et a permis d'atteindre des performances de 16%.Enfin, la modification de ZnO-ALD par des dérivés de l'acide phosphonique a été étudiée.L'organisation des molécules à la surface du ZnO, puis leur effet sur la croissance de la pérovskite ont été détaillés, mais les résultats de cellules complètes restent très faiblePerovskite solar cells have sparked a large interest in the photovoltaic community in the last 10 years due to their expedient optoelectrical properties, their vast scope of applications and their economical attractiveness.They are expected to reach the market by 2023, but challenges have to be tackled first, among which upscale and stability issues.To do so, a strategy is to work on the charge transport layers.They need to ensure a high selectivity towards one charge carrier, and have a good interface.Atomic layer deposition is an industrial deposition technique which allows for the synthesis of a large variety of materials.ALD layers are dense, homogeneous, conformal, pinhole-free and their thickness and composition can be controlled at the nano-scale.ALD hence appears as an ideal candidate to deposit the charge extraction layers.This thesis focuses on the development and on the characterization of various oxides by ALD.SnO2 and TiO2 have been developed at the Institut Photovoltaïque d'Île-de-France (IPVF) with two different processes for each material.Their properties in regard of an integration in perovskite solar cells as inorganic electron transport layers have been explored, and one process for each material has been chosen.The advantageous integration of a 15 nm-thick ALD-TiO2 layer has been demonstrated as compact blocking layer in a mesoporous architecture, and compared to a blocking layer deposited by spray pyrolysis.Similar power conversion efficiencies (PCE) up to 19% have been achieved, with a higher homogeneity of the ALD layer leading to a better reproducibility of the results now used in the baseline production at IPVF.The integration of ALD-SnO2 in planar structures is also discussed.The 10 nm-thick layer alone was found to give mediocre efficiencies due to a lack of fill factor.The addition of an organic interlayer solved this issue allowing for PCE up to 16%.Finally an analysis of the interface between ALD-ZnO modified by phosphonic acid derivatives and a perovskite absorber is proposed.The organization of the molecules at the surface of ZnO and their impact on the perovskite have been determined, but the performances of full devices are poor
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Satter, Md Mahbub. "Design and theoretical study of Wurtzite III-N deep ultraviolet edge emitting laser diodes." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/53042.
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Designs for deep ultraviolet (DUV) edge emitting laser diodes (LDs) based on the wurtzite III-nitride (III-N) material system are presented. A combination of proprietary and commercial advanced semiconductor LD simulation software is used to study the operation of III-N based DUV LDs theoretically. Critical factors limiting device performance are identified based on an extensive literature survey. A comprehensive design parameter space is investigated thoroughly with the help of advanced scripting capabilities. Several design strategies are proposed to eliminate the critical problems completely or partially.
A DUV LD design is proposed based exclusively on AlInN active layers grown epitaxially on bulk AlN substrates because AlInN offers a promising alternative to AlGaN for the realization of LDs and LEDs operating in the DUV regime. The proposed AlInN-based design also features a tapered electron blocking layer (EBL) instead of a homogeneous one. Tapered EBLs redistribute the interfacial polarization charge volumetrically throughout the entire EBL thickness via compositional grading, and eliminate the parasitic inversion layer charge.
AlGaN based DUV LD designs are explored also because at present, it may be difficult to grow AlInN epitaxially with superior crystalline quality. Polarization charge matching is proposed to improve electron and hole wavefunction overlap within the active region. Although the strategy of polarization charge matching has already been proposed in the literature to enhance performance of visible wavelength LEDs and LDs, the proposed design presents the first demonstration that polarization charge matching is also feasible for DUV LDs operating at sub-300 nm wavelengths.
A lateral current injection (LCI) LD design is proposed featuring polarization-charge-matched barriers and regrown Ohmic contacts to avoid a group of issues related to the highly inefficient p-type doping of wide bandgap III-N materials in vertical injection designs. The proposed design partially decouples the problem of electrical injection from that of optical confinement. Although the idea of an LCI LD design has been proposed in the literature in the 90s to be used as longer wavelength active sources in optoelectronic integrated circuits using GaInAsP/InP and related material systems, the proposed design is the first theoretical demonstration that this concept can be applied to DUV LDs based on III-N material system.
To solve the problem of hole transport in vertical injection designs, a DUV LD design based exclusively on AlGaN material system is presented, featuring an inverse-tapered p-waveguide layer instead of an EBL. Several EBL designs are investigated, and compared with conventionally-tapered EBL design. Through judicious volumetric redistribution of fixed negative polarization charge, inverse tapering may be exploited to achieve nearly flat valence band profiles free from barriers to hole injection into the active region, in contrast to conventional designs. Numerical simulations demonstrate that the inverse tapered strategy is a viable solution for efficient hole injection in vertical injection DUV LDs operating at shorter wavelengths (< 290 nm).
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Liu, Guoduan. "Fabrication and Characterization of Planar-Structure Perovskite Solar Cells." UKnowledge, 2019. https://uknowledge.uky.edu/ece_etds/137.
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Currently organic-inorganic hybrid perovskite solar cells (PSCs) is one kind of promising photovoltaic technology due to low production cost, easy fabrication method and high power conversion efficiency.
Charge transport layers are found to be critical for device performance and stability. A traditional electron transport layer (ETL), such as TiO2 (Titanium dioxide), is not very efficient for charge extraction at the interface. Compared with TiO2, SnO2 (Tin (IV) Oxide) possesses several advantages such as higher mobility and better energy level alignment. In addition, PSCs with planar structure can be processed at lower temperature compared to PSCs with other structures.
In this thesis, planar-structure perovskite solar cells with SnO2 as the electron transport layer are fabricated. The one-step spin-coating method is employed for the fabrication. Several issues are studied such as annealing the samples in ambient air or glovebox, different concentration of solution used for the samples, the impact of using filter for solutions on samples. Finally, a reproducible fabrication procedure for planer-structure perovskite solar cells with an average power conversion efficiency of 16.8%, and a maximum power conversion efficiency of 18.1% is provided.
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Madani, Sepideh Sadat. "Investigation of charge transport metal oxides for efficient and stable perovskite solar cells." Thesis, Queensland University of Technology, 2022. https://eprints.qut.edu.au/235892/1/Sepideh%2BSadat%2BMadani%2BThesis%282%29.pdf.
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This research investigates various thin-film metal oxides as charge transport layer for improving the performance and stability of perovskite solar cells. Physical Vapor Deposition techniques such as magnetron sputtering, and electron beam evaporation were used to fabricate the metal oxide thin films. The structural, morphological, chemical, optical, electrical, and electronic properties of the films were studied. Solar Cell Capacitance Simulator was employed for investigating the performance of the PSC using the experimental data as input parameters. Results showed that optimized properties of the metal oxide thin films as charge (hole) transport layer have improved the performance of the PSC device.
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Vergnat, Michel. "Hydrogénation d'alliages semi-conducteurs amorphes : Structure et propriétés électroniques des alliages amorphes hydrogènes SI::(1-X)SN::(X):H." Nancy 1, 1988. http://www.theses.fr/1988NAN10322.
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Les atomes d'hydrogène sont introduits dans les couches durant leur élaboration par évaporation. L'influence des paramètres de préparation est mise en évidence sur les propriétés physiques de couches de SI pur. Les alliages SI::(1-X)SN::(X) et SI::(1-X)SN::(X) : H peuvent être préparés à l'état amorphe dans une large gamme de compositions. Des études de diffraction électronique, de spectrométrie moessbauer et des mesures de densité massique montrent que ces alliages possèdent une structure tétraédrique. Cette méthode a également permis d'élaborer des multicouches SI/SI : H, de l'étain semiconducteur et de l'hydrure de titane
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Ou, Cheng-Chi, and 歐政佶. "Anisotropy of Electron Transport in Few-Layers ReSe2." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/r6222h.
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碩士國立交通大學
電子物理系所
106
In this thesis, we used mechanical exfoliation to produce few-layers rhenium selenide (ReSe2) flakes on a silicon wafer covered by 300-nm thick silicon dioxide. Standard electron-beam lithography and thermal evaporation were used to pattern gold (Au) electrodes on ReSe2 flakes. The as-fabricated field effect transistor (FET) devices of ReSe2 were annealed in a high vacuum to improve the metal contact and to reduce the contact resistance. The devices were then electrically characterized. At room temperature, ReSe2 reveals itself as a n-type semiconductor, showing an on-off ratio of current up to 106. We studied electron transport in the ReSe2 FET devices in a wide temperature range from 80 K to 600 K. At a temperature below 200 K, electron transport in ReSe2 is well described by the theory of two-dimensional Mott’s variable range hopping. In this temperature range, we have discovered a phase transition from an insulator to a metallic state with increasing carrier concentration, adjusted by the back-gating voltage. As a temperature in the range between 300 K and 500 K, electron transport in ReSe2 is well described by thermally activated transport. When the temperature is higher than 500 K, the few-layers ReSe2 flakes changes from semiconducting to metallic behaviors once more. It reveals another insulator-to-metal transition at such a high temperature. This transition could originates from the electron-phonon interactions. ReSe2 is known for its anisotropic electrical property. Here we make multiple probes to measure electrical properties in different lattice orientations. We measured transfer characteristics of ReSe2 FET devices in several different orientations. As a first step, we set the orientation of 0° as the direction showing the highest mobility. We found that the direction of the lowest mobility is always exhibiting at 90°. In addition, we studied the anisotropy of electron transport at temperatures from 80 to 300 K. We learned that the anisotropy effect in ReSe2 only gives a different magnitude of conductance in different orientation while the mechanism of electron transport is the same in all directions.
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Lin, Hsi-Kuei, and 林熙貴. "Effects of A Block Copolymer–tuned Fullerene Electron Transport Layer and Dual Nanocomposite Carrier Transport Layers for Inverted Planar Perovskite Solar Cells." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/4z7ac8.
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博士國立交通大學
材料科學與工程學系所
106
In photovoltaic devices, more effective transfer of dissociated electrons and holes from the active layer to the respective electrodes will result in higher fill factors and short-circuit current densities and, thus, enhanced power conversion efficiencies (PCEs). Planar perovskite photovoltaics feature an active layer that can provide a large exciton diffusion length, reaching several micrometers, but require efficient carrier transport layers for charge extraction. In the first part study, we enhanced the PCE of perovskite solar cells by employing an electron transfer layer (ETL) comprising [6,6]phenyl-C61-butyric acid methyl ester (PC61BM) and, to optimize its morphology, a small amount of the block copolymer polystyrene-b-poly(ethylene oxide) (PS-b-PEO), positioned on the perovskite active layer. When incorporating 0.375 wt % PS-b-PEO into PC61BM, the PCE of the perovskite photovoltaic device increased from 9.4% to 13.4%, a relative increase of 43%, because of a large enhancement in the fill factor of the device. To decipher the intricate morphology of the ETL, we used synchrotron grazing-incidence small-angle X-ray scattering for determining the PC61BM cluster size, atomic force microscopy and scanning electron microscopy for probing the surface, and transmission electron microscopy for observing the aggregation of PC61BM in the ETL. We found that the interaction between PS-b-PEO and PC61BM resulted in smaller PC61BM clusters that further aggregated into dendritic structures in some domains, a result of the similar polarities of the PS block and PC61BM; this behavior could be used to tune the morphology of the ETL. The optimal PS-b-PEO-mediated PC61BM cluster size in the ETL was 17 nm, a large reduction from 59 nm for the pristine PC61BM layer. This approach of incorporating a small amount of nanostructured block copolymer into a fullerene allowed us to effectively tune the morphology of the ETL on the perovskite active layer and resulted in enhanced fill factors of the devices and thus their device efficiency. For the second part study, we employed two nanocomposite carrier transfer layers—a ETL comprising PC61BM doped with the small molecule 4,7-diphenyl-1,10-phenanthroline (Bphen), to enhance the electron mobility, and a hole transfer layer (HTL) comprising poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) doped with molybdenum disulfide (MoS2) nanosheets, to enhance the hole mobility. We used ultraviolet photoelectron spectroscopy to determine the energy levels of these composite ETLs and HTLs; atomic force microscopy and scanning electron microscopy to probe their surface structures; and transmission electron microscopy and synchrotron grazing-incidence small-angle X-ray scattering to decipher the structures of the ETLs. Adding a small amount (less than 1%) of Bphen allowed us to tune the energy levels of the ETL and decrease the size of the PC61BM clusters and, therefore, generate more PC61BM aggregation domains to provide more pathways for electron transport, leading to enhanced PCEs of the resulting perovskite devices. We used quantitative pump-probe data to resolve the carrier dynamics from the perovskite to the ETL and HTL, and observed a smaller possibility of carrier recombination and a shorter injection lifetime in the perovskite solar cell doubly modified with carrier transport layers, resulting in an enhancement of the PCE. The PCE reached 16% for a planar inverted perovskite device featuring an ETL incorporating 0.5 wt% Bphen within PC61BM and 0.1 wt% MoS2 within PEDOT:PSS; this PCE is more than 50% higher than the value of 10.2% for the corresponding control device.
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Chang, Chun-Jung, and 張峻榮. "ZnO nanocrystals incorporating PEIE/polyfluorene electrolyte as electron transport layers for cesium-containing perovskite light-emitting devices." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/5bkvhq.
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碩士國立交通大學
照明與能源光電研究所
107
In this work, we demonstrate inverted perovskite light-emitting devices (PeLEDs) based on ZnO nanocrystals (NCs) and cesium lead bromide (CsPbBr3) film as the electron transport and emission layers, respectively. A polyethyleneimine ethoxylated (PEIE) and/or an ionic polyfluorene electrolyte containing trimethylammonium hexafluorophosphate groups (namely P2-PF6) were introduced between ZnO NCs and CsPbBr3 film to enhance electron injection. The introduction of the PEIE/P2-PF6 bilayer can effectively improve CsPbBr3 coverage and morphology, thereby reducing current leakage in PeLEDs. Meanwhile, the improved CsPbBr3 film showed better photoluminescence, owing to anti-quenching capability of the PEIE/P2-PF6 and prolonged carrier lifetime. Herein, the PeLEDs with the structure ITO/ZnO NCs/ PEIE/P2-PF6/CsPbBr3 film/poly(9,9-dioctylfluorene-co-N-(4-butylphenyl)diphenyl amine) (TFB)/Au were fabricated, employing TFB as the hole transport layer. The PeLED based on the PEIE/P2-PF6 showed a turn-on voltage of 2.8 V, a max luminance of 3,927 cd/m2 and max current efficiency of 0.2 cd/A that was significantly higher than those without PEIE/P2-PF6 bilayer.
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Chittawanij, Apisit, and 艾比西. "The Study of Electron Transport Layers in Organic Light-Emitting Diodes by Thermal Evaporation and Stamping in Solution Processes." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/jzxu39.
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博士國立虎尾科技大學
光電工程系光電與材料科技博士班
104
This dissertation is about the engineering of high performance OLEDs, which includes the electron transport layer thermal evaporation and stamping in OLED solution-processes. The following work is included in this dissertation: (i) An n-type doping system of tris(8-hydroxy-quinolinato) aluminum (Alq3) doped 2-(hydroxyl) quinolone lithium (Liq) in hybrid white OLEDs is developed and its device performances are compared with the conventional device. The maximum current efficiency of 23.2 cd/A and power efficiency of 7.4 lm/W at 20 mA/cm2 were obtained from the n-type doping HWOLED device. (ii) White OLEDs based on phosphorescent emitters are regarded as potential candidates for future lighting and display applications. In this study three phosphorescent dyes are incorporated, iridium(III) [bis(4,6-difuoro phenyl)-pyridinato-N,C2′] picolinate (FIrpic), tris[2-phenylpyridinato-C2,N] iridium (III) (Ir(ppy)3) and bis[2-(1-isoquinolinyl-N) phenyl-C](2,4-pentanedionato-O2,O4) iridium(III) (Ir(piq)2 acac), into a host of 4,4′-Bis(N-carbazolyl)-1,1′-biphenyl (CBP) to achieve a simple single-emitting white OLED layer using the solution process. The current and power efficiencies of the blue device with FIrpic 20 wt% in chlorobenzene were 2.95 and 0.89 lm/W at 20 mA/cm2. The current efficiency of 3.1 cd/A at 20 mA/cm2 and the CIE coordinates of (0.31, 0.32) at 1000 cd/m2 were obtained from the white device. (iii) To achieve high-performance OLEDs using solution-processing, uniform amorphous film formation is a very important prerequisite, which depends strongly on the solution-process materials. Highly efficient flexible blue OLEDs were fabricated by solution-processing commercial small molecules as the mixed-hosts. The hole transporting 4,4′ ,4″ -tri(N-carbazolyl)triphenylamine (TCTA) doped with the host 2,6-bis(3-(9H- carbazol-9-yl)phenyl)pyridine (26DCzPPy) as the solution-processed mixed-host for flexible blue OLED was investigated. The device with TCTA doped host exhibits the luminance of 2800 cd/m2, current density of 14.00 cd/A and power efficiency of 4.3 lm/W at 20 mA/cm2. (iv) Efficient multilayered flexible blue OLEDs were fabricated using the stamping method with PDMS and release film as transfer film. In order to overcome the mixing problem that occurs between the organic layers during the solution-processes, the stamping method was utilized on a small molecule layer. At the current density of 20 mA/cm2, the flexible blue OLED with PDMS as transfer film stamping device shows current and power efficiencies of 5.2 cd/A and 1.5 lm/W, respectively. The multilayered flexible blue OLEDs manufactured using the proposed stamping method presented significantly over spin-coated devices.
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Huang, Yi-Jiun, and 黃義鈞. "Doping Zinc Oxide with Molybdenum or Tungsten Disulfide Nanosheets as Electron Transport Layers for Polymer with Fullerene or Small Molecule Photovoltaics." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/c7z7k5.
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博士國立交通大學
材料科學與工程學系所
107
In organic photovoltaic (OPV) devices, more effective transfer of dissociated electrons and holes from the active layer to the respective electrodes will result in higher fill factors (FF) and short-circuit current densities (Jsc) and, thus, enhanced power conversion efficiencies (PCE). The PCE of OPVs is affected not only by active layer but also transport layer. In my study, I specialize in developing the electron transport layer (ETL) by doping two-dimensional (2D) transition-metal dichalcogenide (TMD) materials for OPV devices. In the first part study, we incorporated molybdenum disulfide (MoS2) nanosheets into sol–gel processing of zinc oxide (ZnO) to form ZnO:MoS2 composites for use as ETLs in inverted polymer solar cells featuring a binary bulk heterojunction active layer. We could effectively tune the energy band of the ZnO:MoS2 composite film from 4.45 to 4.22eV by varying the content of MoS2 up to 0.5 wt%, such that the composite was suitable for use in bulk heterojunction photovoltaic devices based on poly[bis(5-(2-ethylhexyl)thien-2-yl)benzodithiophene–alt–(4-(2-ethylhexyl)-3-fluorothienothiophene)-2-carboxylate-2,6-diyl)] (PTB7-TH):phenyl-C71-butryric acid methyl ester (PC71BM). In particular, the PCE of the PTB7-TH:PC71BM (1:1.5, w/w) device incorporating the ZnO:MoS2 (0.5 wt%) composite layer as the ETL was 10.1%, up from 8.8% for the corresponding device featuring ZnO alone as the ETL—a relative increase of 15%. Incorporating a small amount of MoS2 nanosheets into the ETL altered the morphology of the ETL and resulted in enhanced current densities, fill factors, and PCEs for the devices. We used ultraviolet photoelectron spectroscopy (UPS), synchrotron grazing-incidence wide-/small-angle X-ray scattering (GIWAXS/GISAXS), atomic force microscopy (AFM), and transmission electron microscopy (TEM) to characterize the energy band structures, internal structures, surface roughness, and morphologies, respectively, of the ZnO:MoS2 composite films. For the second part study, a new universal ETL that involves doping hydrogen-plasma treated tungsten disulfide (WS2) nanosheets into ZnO for polymer/fullerene or small molecule OPVs was prepared. A hydrogen-plasma treatment was used to alter the structures of WS2 nanosheets such that the W6+ content was converted into W4+; then ZnO:WS2 nanosheets composites were prepared to form ETLs. The energy band of the ZnO:WS2 films could be tuned from 5.15 to 4.60 eV by varying the concentration of the WS2 nanosheets up to 0.5 wt%. It was found that ZnO:WS2 ETLs exhibited superior charge transport properties than those of the pristine ZnO layer because of the structure changes, as determined from the X-ray scattering characterizations. OPVs incorporating active layers of PTB7-TH/PC71BM and PTB7-TH/IDIC blends exhibited their power conversion efficiencies of 10.3% and 6.7%, respectively, with the incorporation of 0.3 wt% of the WS2 nanosheets, up from 8.9% and 5.4% for the corresponding devices featuring pristine ZnO—relative increases of 16% and 24%, respectively. This study demonstrates the effectiveness of hydrogen-plasma treatment for altering the surface structures of 2D TMD nanosheets, and paves a way for the composite ETLs for use in OPVs.
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Li, Cheng-Wei, and 李丞偉. "Modify TiOx electron transport layer of organic solar cells." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/36270723548232476106.
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Siao, Ming-Deng, and 蕭名登. "Surface Electron Accumulation and Electronic Transport in MoS2 Layer Semiconductors." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/8qzu62.
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碩士國立臺灣科技大學
應用科技研究所
105
Surface electron accumulation (SEA) and thickness-dependent electric properties in the molybdenum disulfide (MoS2) two-dimensional (2D) nanostructures have been observed and investigated. The MoS2 nanoflakes fabricated by mechanical exfoliation exhibit several orders of magnitude higher conductivity than their bulk counterparts. The carrier activation energy of nanostructures is lower than that of the bulk counterparts. The transfer length method was used to determine the current transport in MoS2 following a 2D behavior rather than the conventional 3D mode. Scanning tunneling microscopy measurements confirmed the presence of surface electron accumulation (SEA) in this layer material. Notably, the pronounced n-doping characteristic can be easily removed by producing a fresh surface through mechanical exfoliation. Long-term exposure to air can transform the intrinsic fresh surface into a metallic-like surface, indicating that SEA is not inherent. The FET measurement indicates that the MoS2 nanoflakes with fresh surface exhibit higher mobility and lower electron concentration compare to the nanoflakes with non-fresh surface. A more significant surface scattering in the non-fresh MoS2 nanoflakes was proposed.
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Lin, Guan-Hong, and 林冠宏. "Studies on electron and hole transport layer in polymer solar cell." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/60348014300394884579.
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碩士國立清華大學
化學工程學系
98
In recent years, polymer solar cells have become an important issue, because of attention to alternative energy resources. For polymer solar cells, the morphology of active layer and the series resistance both play important roles in designing highly efficient solar cells.Therefore, the influence of these two factors on efficiency of polymer solar cells based on poly(3-hexylthiophene) (P3HT) blended with [6,6]-pheneyl-C61 butyric acid methyl ester (PCBM) as the active layer is investigated in this thesis. In the first part of this thesis, we use thermal annealing and solvent annealing approach to change the active layer morphology. Under the optimal condition, the device efficiency of 3.75 % and 4 % are achieved for thermal annealing and solvent annealing. In the second part of this thesis, a water-soluble polyaniline, sulfonic acid ring substituted polyaniline (SPAN), which is synthesized in our laboratory, is adopted as a hole transport layer in the polymer solar cells.The device efficiency of 3.75 % is achieved which is similar to device with PEDOT：PSS as a hole transport layer (3.9 %), and indicates that SPAN has opportunity to substitute PEDOT：PSS as hole transport layer material in polymer solar cells. In the last part of this thesis, we use water-soluble crown-ether-substituted polyfluorene, poly[9,9’-bis(6’-(((1,4,7,10,13,16)hexaoxacyclooctadecanyl) methoxy)hexyl)fluorene] (PF-18-crown-6) as the electron transport layer for the first time to reduce series resistance in the polymer solar cells. The device efficiency can be promoted from 2.45 % to 2.82 % after insertion of this layer, which indicates PF-18-crown-6 can reduce series resistance of polymer solar cells and enhance the device efficiency.
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Liao, Ying Han, and 廖盈涵. "Tuning TiO2 Electron Transport Layer to Enhance Perovskite Solar Cell Performance." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/mchd6u.
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HSU, YUAN-HAO, and 許元豪. "Preparation of Perovskite Active Layer and TiO2 Electron Transport Layer Applied for Perovskite Solar Cell." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/r874qr.
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碩士國立雲林科技大學
電子工程系
106
In order to prepare a high quality perovskite active layer while avoiding complex and time-consuming processes, the perovskite active layer is prepared by using one-step spin-coating method. In order to control the completion and amount of the perovskite grains, the toluene dumping time in the one-step spin-coating method is used to prepare the perovskite active layer of perovskite solar cell (PSC). The electron transport layer (ETL) is prepared by using spin-coating method, where the electron transport layer includes both compact layer (CL) and mesoporous layer (ML). The compact layers with different thicknesses are prepared by using different rotational speeds, and the mesoporous layers are prepared by using different TiO2 materials: TiO2 powder P90 (P90) or TiO2 paste T (T). The PSCs are prepared by using these perovskite active layers and electron transport layers, while the performances of PSCs are investigated. In the first part of this study, one-step spin-coating method is used to prepare perovskite active layers by using different toluene dumping time. The result implies that the highest photoelectric conversion efficiency (PCE) of the PSC is 5.29%, in which the perovskite active layer of PSC is prepared with toluene dumping at the fifth second. In the second part of this study, the TiO2 compact layer is prepared with different rotational speeds, and the TiO2 mesoporous layer is prepared by using different TiO2 materials: TiO2 powder P90 (P90) and TiO2 paste T (T). The result implies the thickness of compact layer with a rotational speed of 5000 rpm in 30 seconds is 35 nm, on which a mesoporous layer of TiO2 (T) is stacked as electron transport layer in PSC and the PSC has the best performances, where the open-circuit voltage (Voc) is 0.95 V, the short-circuit current density (Jsc) is 18.45 mA/cm2, the fill factor (F.F.) is 0.42, and the photoelectric conversion efficiency (PCE) is 7.45%.
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Wang, Hung-Yi, and 王宏毅. "Electron transport and field-effect properties of ferrocene on few-layer MoS2." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/23314607645291693357.
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碩士國立交通大學
電子物理系所
104
In this thesis, we will discuss the changes of electron transport and field-effect behavior when the organometallic compound-ferrocene is adsorbed on the surface of few-layer molybdenum disulfide. We used mechanical exfoliation to make few-layer molybdenum disulfide (MoS2) flakes on silicon substrate, capped with 300-nm thick silicon dioxide layer. The standard electron beam lithography and thermal evaporation were used to deposit source and drain electrodes on few-layer MoS2 flakes. The MoS2 devices were annealed in a high vacuum in order to fix structural defects of MoS2 and to lower the contact resistivity. Two-probe measurement is used to measure the source-drain current voltage (I-V) curve and gate voltage-drain current (〖V_g-I〗_(SD )) curve. An atomic force microscopy was used to measure the topography and the thickness of few-layer MoS2. After the electrical properties of bare MoS2 devices were characterized, the ferrocene molecules were deposited on surface of the MoS2 by using micro tube. The ferrocene deposited MoS2 devices were annealed in a high vacuum to remove the solvent (chloroform). We then compared the electrical properties with that of bare MoS2 devices. The few-layer MoS2 devices are n-type semiconductors at room temperature. When the ferrocene molecules are deposited, the electric dipole of ferrocene gives internal electric fields that decrease electric fields in MoS2 supplied by the back-gate voltage. It results in the increasing of off-state current as more and more ferrocene molecules are adsorbed on the MoS2 surface. On the other hand, the temperature dependent resistance of ferrocene on MoS2 is well described by the theory of two-dimensional (2D) variable range hopping (VRH) transport in the temperature range from 200 to 100 K. The mobility reduces and the characteristic temperature extracted from fitting to the 2D VRH theory increases after ferrocene deposition. These results indicate that the existence of ferrocene introduces a disorder of stray electric fields in few-layer MoS2.
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KimLien, Duong Thi, and 楊氏金蓮. "Perovskite Solar Cell Having AlxZn(1-x)O Nanorod Electron Transport Layer." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/90636757820691475714.
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碩士國立成功大學
材料科學及工程學系
104
In the present work, we have investigated the use of ZnO nanorods (NRs) and Al modified ZnO (AZO) NRs in perovskite solar cell. ZnO NRs were synthesized using chemical bath deposition. The effect of deposition condition on the NR characteristics was studied. Desired NR layers were used for the deposition of perovskite, CH3NH3PbI3, using either a two-step sequential deposition or a one-step deposition technique. The deposition of the perovskite on the NR layer was optimized by examining the morphology, thickness, crystalline structure, optical absorption, and photoluminescence property. Solar cells were fabricated using selected NR and perovskite layers, having either glass or plastic substrates. The resulting cells were evaluated using a sun light simulator and current-voltage measurement. The effects of the characteristics of the NR layers on the cell performance are addressed.
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Kim, Seyoung 1981. "Electron transport in graphene transistors and heterostructures : towards graphene-based nanoelectronics." Thesis, 2012. http://hdl.handle.net/2152/ETD-UT-2012-05-5420.
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Two graphene layers placed in close proximity offer a unique system to investigate interacting electron physics as well as to test novel electronic device concepts. In this system, the interlayer spacing can be reduced to value much smaller than that achievable in semiconductor heterostructures, and the zero energy band-gap allows the realization of coupled hole-hole, electron-hole, and electron-electron two-dimensional systems in the same sample. Leveraging the fabrication technique and electron transport study in dual-gated graphene field-effect transistors, we realize independently contacted graphene double layers separated by an ultra-thin dielectric. We probe the resistance and density of each layer, and quantitatively explain their dependence on the backgate and interlayer bias. We experimentally measure the Coulomb drag between the two graphene layers for the first time, by flowing current in one layer and measuring the voltage drop in the opposite layer. The drag resistivity gauges the momentum transfer between the two layers, which, in turn, probes the interlayer electron-electron scattering rate. The temperature dependence of the Coulomb drag above temperatures of 50 K reveals that the ground state in each layer is a Fermi liquid. Below 50 K we observe mesoscopic fluctuations of the drag resistivity, as a result of the interplay between coherent intralayer transport and interlayer interaction. In addition, we develop a technique to directly measure the Fermi energy in an electron system as a function of carrier density using double layer structure. We demonstrate this method in the double layer graphene structure and probe the Fermi energy in graphene both at zero and in high magnetic fields. Last, we realize dual-gated bilayer graphene devices, where we investigate quantum Hall effects at zero energy as a function of transverse electric field and perpendicular magnetic field. Here we observe a development of v = 0 quantum Hall state at large electric fields and in high magnetic fields, which is explained by broken spin and valley spin symmetry in the zero energy Landau levels.text
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Chang, Yan-Ru, and 張雁茹. "Bathocuproine Doped in PCBM as an Electron Transport Layer for Perovskite Photovoltaic Application." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/c789dr.
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碩士國立交通大學
材料科學與工程學系所
106
In this study, we doped different amounts of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (bathocuproine, BCP) in [6,6]phenyl-C61-butyric acid methyl ester (PC61BM) and successfully improved the power conversion efficiency (PCE) of perovskite photovoltaic device. With the incorporation of BCP, we found that it can not only ameliorate the film formation property of PCBM and the interfacial contact but facilitate the charge transport and separation at the interface through effectively passivating the surface trap states of perovskite as well. These physical, optical, morphological, and electronic improvements result in higher open-circuit voltage (Voc), short-circuit current density (Jsc), and fill factor (FF). Therefore, the PCE is improved from 9.4% to 14.3%. The planar-heterojunction structure of the photovoltaic devices having the confugutation ITO/PEDOT:PSS/CH3NH3PbI3-xClx/PC61BM:BCP/Ag. In order to systematically investigate the effect of BCP doping, we use a combination of characterizations, including grazing-incidence small-angle X-ray scattering (GISAXS), atomic force microscopy (AFM), scanning electron microscopy (SEM), photoluminescence (PL) and ultraviolet–visible spectroscopy (UV-vis). We can understand that, as a result, this approach of incorporating small molecule into a fullerene allowed us to effectively tune the morphology of the ETL on the perovskite active layer and resulted in enhanced device efficiency.
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ThanhSon, Bach, and 白青山. "Integration of Reduced Graphene Oxide in Electron Transport Layer of Perovskite Solar Cells." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/jj2epj.
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碩士國立成功大學
材料科學及工程學系
107
The electron transport layer (ETL) plays a crucial role in facilitating electron extraction and inhibiting recombination in perovskite solar cells. Reduced graphene oxide (RGO) is a potential complement to the common ETL material TiO2 thanks to its excellent electrical conductivity and mobility and the suitability for scalable, low-temperature solution-processed deposition. RGO powder is synthesized through microwave-assisted hydrothermal method, and various amounts of o-phenylenediamine (OPD) are added into the precursor to create Nitrogen-doped RGO of different doping levels. The as-synthesized RGO samples characteristics are examined by XRD, XPS and Raman spectroscopy. The perovskite layer of CH3NH3PbI3 is deposited on RGO and TiO2 using a two-step spin coating process, and the as-deposited perovskite characteristics are examined through photoluminescence and UV-Vis spectroscopy. Finally, photovoltaic performance measurements of completed RGO-integrated devices is conducted under illumination of 1 Sun AM 1.5G sunlight simulator.
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Huang, Hao-Jung, and 黃浩榕. "A Study of High Efficient Organic Electroluminescent Devices with Multi-Layer Electron Transport Structure." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/43437894603157769335.
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碩士國立成功大學
電機工程學系
88
In this thesis, doped electron transport layer (ETL) and doped hole transport layer (HTL) organic electroluminescent (OEL) devices are successfully prepared by a vacuum evaporation system. The optimum rubrene doping concentration in Tris-(8-hydroxyquinolinato) aluminum(Ⅲ) (Alq3) and N,N’-diphenyl-N,N’-bis(3-methyphenyl)-1,1’-biphenyl-4,4’-diamine (TPD), which is 2.5 and 4 wt%, respectively. We have demonstrated that using Li/Al cathode and a Phthalocyanine Copper (CuPc) buffer layer for the device, ITO/CuPc/ TPD/Alq3/CuPc/Li/Al, can efficiently lower the operation voltages and enhance the performance of OEL devices. Furthermore, using CuPc to replace part of Alq3 for electron transport layer can lower operating voltages and get better luminous efficiencies. The role of CuPc in such OEL devices will be discussed. The vacuum evaporation system is adopted to deposit organic films of Alq3, TPD, and CuPc on the ITO coated glass substrate. The highly fluorescent molecule, rubrene, is doped in either Alq3 or TPD. Current-voltage curves are used for electrical analysis. Luminance, photoluminescence (PL), electroluminescence (EL) , ultraviolet-visible spectroscopy (UV-Vis), and commission innternationale de I’Eclairage (CIE) are used for the study of optical characteristics. By using a Li/Al cathode and replacing part of Alq3 with CuPc as an electron transport layer, we can lower the operating voltage and enhance the performance of OEL devices. The luminance, 1000 cd/m2, can be obtained at 5.5 V driving voltage. The maximum luminance is as high as 14000 cd/m2 in the investigation. Finally, We have demonstrated that CuPc is not a good material for an electron transport layer itself, but CuPc with a Li contact can get better electron transport property than Alq3.
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Wang, Tsung-Chang, and 王宗昶. "Investigation of electron transport layer and fluoride for the properties of organic solar cells." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/fu8884.
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碩士國立高雄大學
應用物理學系碩士班
97
The organic solar cells (OSC) have several superior advantages to inorganic solar cells, including lower cost, larger fabrication area, lighter weight and flexible property. Unfortunately, the power conversion efficiency (PCE) of the OSC is quite poor at the present time. Thus, improvement of PCE is an important issue. And then there are improvement methods of OSC from introduction of device concept such as change in active material, light harvesting structure, annealing and the electron transport layer (ETL). In this study, the structure of small-molecule OSC with is ITO-coated glass substrate /Copper phthalocyanine (CuPc) / fullerene (C60)/electron transport layer (ETL)/Al. The active layer is composed of CuPc and C60. 2-(4-Biphenylyl)-5-(4-tert-butylphenyl)-1, 3, 4-oxadiazole (PBD), Aluminum tris(8-hydroxyquinoline) (Alq3) and bathocuproine (BCP) are used as an electron transport layer. The materials of LiF and KF are used as a modification layer. In this study, the thicknesses of each material have been optimized for a better PCE. Besides, the short current density (Jsc) of devices with BCP layer was greatly improved compared with that of other ETL materials. The superior properties of BCP, such as lower electron injection barrier, higher UV/vis absorption efficiency and lower surface roughness, have been demonstrated by the energy level diagram, UV/vis absorption spectra and atom force microscope (AFM) data. In order to further improve the PCE of devices, we add ultra-thin fluoride as a modification layer to the devices with BCP layer. The PCE of OSC is improved from 0.54 % to 0.64 %.
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Shin-YuLin and 林信宇. "Deposition of Gallium Nitride films as electron transport and hole blocking layer in OLED." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/76k2ax.
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碩士國立成功大學
化學工程學系
102
This article is about the research of Gallium Nitride(GaN) as electron injection and hole blocking layer in Organic Light Emitting Diode(OLED). The traditional material for electron injection and hole blocking layer is BCP, which Tg point is low. We want to use GaN to replace Bathocuproine(BCP) to enhance the stability of OLED device. Using RF sputtering method to grow GaN film under different condition, thermal evaporation system to deposit organic layer. In the begin the device performance was bad ,with turn on voltage up to 15V and only 119cd/m2. After figuring out the problem, change the working pressure from 10mTorr to 5mTorr, and treat the surface with N2 plasma. The device performance now enhances from 119cd/m2 to 1091cd/m2.
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Yi-ChingChen and 陳怡靜. "Performance Investigation of Perovskite Solar Cells with Multi-Layer Electron and Hole Transport Structures." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/kjq5rb.
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Tsai, Yung-Han, and 蔡詠涵. "Two-dimensional atomically thin perovskite oxide as electron transport layer for perovskite solar cells." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/as64kv.
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碩士國立臺灣大學
材料科學與工程學研究所
106
Two-dimensional (2D) oxides are a large group of 2D materials. These 2D oxides can be divided into two subgroups: 2D metal oxides and 2D perovskite oxides. They are rich in structural diversity, electronic properties, and have novel physical and chemical properties from quantum confinement or surface effects comparing to their bulk states. 2D oxides are widely applied in the nanocapacitors, secondary batteries, and photocatalysts fields. Among the 2D perovskite oxides, Ca2Nb3O10 (CNO) atomic sheet is an n-type wide bandgap semiconductor. It has well aligned conduction band minimum with that of the lead halide perovskite, which is an efficient light absorber for solar cell application. These properties make CNO a promising electron transport material to extract electrons and block holes from lead halide perovskite light absorber. On the other hand, comparing to the conventional high temperature (> 500 ˚C) sintered compact-TiO2 electron transport layer, CNO can be deposited with relative low temperature (< 150 ˚C) solution process. In this work, we deposited CNO with low temperature Langmuir-Blodgett deposition method as electron transport layer to fabricate perovskite solar cell. The resultant devices showed best efficiency of 14.10%, which is compatible to the conventional high-temperature sintered compact-TiO2 device (14.07%). Moreover, the CNO based devices showed better electron transport ability than the conventional ones. Our work showed that CNO atomic sheet is a highly promising electron transport material for low-temperature solution processed all perovskite structure solar cells.
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Agrawal, Neetu. "Electron optics with dirac fermions: electron transport in Mano-and bi- layer graphene through various scalar and vector potential barriers." Thesis, 2013. http://localhost:8080/iit/handle/2074/6561.
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Zeng, Yu (Anne). "A study of electron transport in the inversion layer advanced silicon carbide (SiC) power MOSFETs /." Diss., 2004. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3147336.
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Lin, Shu-Wei, and 林書緯. "Application and Characterization of Organic-Inorganic Hybrid Electron Transport Layer Used for Organic Photovoltaic Device." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/00125799217068940233.
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碩士國立交通大學
工學院加速器光源科技與應用碩士學位學程
102
In this research we present an “Organic-Inorganic Hybrid Electron Transport Layer” to control microstructure and tune energy level of zinc oxide. In the experimental part, we blend polyethylenimine with sol-gel processed zinc oxide and control the concentration of polyethylenimine to modify property of zinc oxide. The small angle X-ray scattering (SAXS) measurements demonstrate decrease of zinc oxide nanoclusters size for better quality of thin film. The ultraviolet photoelectron spectroscopy (UPS) measurements show shift of energy level for better electron-transporting. Using this approach, P3HT:PC61BM solar cell parameters including short circuit current density and fill factor are improved leading to the PCE increase up to 4.6%.
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Wei, Chen-Yo, and 魏晨祐. "Studies on High Performance Low Bandgap Polymer Solar Cell Through Modifications of Electron Transport Layer." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/y7z25j.
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Ke, We-Chen, and 柯威辰. "Interface Modification on Electron Transport Layer to Improve Power Conversion Efficiency of Perovskite Solar Cells." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/m7yjdh.
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碩士國立臺灣大學
材料科學與工程學研究所
107
Perovskite solar cells (PSCs) have drawn enormous attention in recent years owing to their high power conversion efficiency over 20%. Some of its exceptional properties such as remarkably high absorption over the visible spectrum, long charge carrier diffusion lengths in the μm range, and tunable band gap by interchanging various structure ions reveal its great potential in solar conversion. Nevertheless, in order to promote carrier transmission efficiency of devices, how to elevate the ability to quench carriers aiding with other material layers’ aiding is an important issue nowadays. In the beginning, perovskite added Louis base is proofed to facilitate power conversion efficiency of perovskite solar cells; therefore, urea is adopted and successfully promotes efficiencies of devices. However, it is confirmed by papers that zinc oxide (ZnO) and tin oxide (SnO2) possess higher electron mobility and more suitable band structure, which are considered to be the replacements of TiO2 ETL. After analyzing surface morphology, X-ray diffraction, and carrier quenching efficiency, it is understood that ZnO coated perovskite is quite unstable and quickly degrades in atmosphere. Besides, tin oxide demonstrates the best transmission rate in three of them, so this metal oxide electron transport material is chose to do the next step of surface modification. The second is introducing the surface modification material to effectively separate excitons into carriers and for them to be quenched by ETL. Here, C60 pyrrolidine tris-acid (CPTA) and [6,6]-phenyl- C61-butyric acid methyl ester (PCBM) are separately passivated on SnO2 for comparison. In the past, PCBM was usually adopted in inverted perovskite solar cell as an organic electron transport layer, and it has been found that it could be used in surface as well modification in recent years. However, surface morphology, X-ray diffraction and photoluminescence (PL) show that CPTA transfers carrier more efficiently. In FTIR data analysis, the further study comprehends that the hydroxyl terminal groups on CPTA are coordinated with oxygen-vacancy-related defects of Sn in SnO2, and chemical bonding with interface modification brings better transfer ability than PCBM with non-bonding passivation on SnO2, forasmuch it is more advisable to be applied in facilitating performance of perovskite solar cells.
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SINGHAL, NISHANT. "NUMERICAL SIMULATION OF PCBM AND MoO3 STACED ELECTRON AND HOLE TRANSPORT LAYER BASED PEROVSKITE SOLAR CELL." Thesis, 2018. http://dspace.dtu.ac.in:8080/jspui/handle/repository/16227.
Full textAbstract:
In this study, a perovskite based solar cell device has been proposed and the power conversion efficiency, fill factor, open circuit voltage and short circuit current density of the proposed device was analyzed. When simulated, it achieves a power conversion efficiency of over 14% with AM 1.5 illumination. This type of perovskite solar cell has shown potential towards achieving a low cost and efficient solar energy conversion method and unlike its silicon counterparts, it has none of the disadvantages that are present in silicon based solar cells.
Different materials and their combinations were used as electron transport layer and hole transport layer. Materials that were used as electron transport layer resulted in short circuit current density of 17.92 mA.cm-2. When a combination of two materials were used as hole transport layer, it has been observed that the external quantum efficiency is close to 55% in the 350-450 nm range which corresponds to high power conversion efficiency of 14.27% but the open circuit voltage showed little variation around 1.02 volts .
When MoO3 is used as a hole transport layer and its thickness and doping was optimized, it was observed that there is a 60% increase in the short circuit current density as the thickness of MoO3 was decreased and a 2% decrease in the PCE and FF with increase in thickness. When the doping of MoO3 is varied, the external quantum efficiency went down from 55% to 50%.
Detailed realistic technology computer aided design (TCAD) analysis has been performed to predict the behavior of the device.