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Conlon, Benjamin Patrick. "Solving Series Resistance Problems In GaSb Thermophotovoltaics with Graphene and Other Approaches." Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/78286.
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GaSb Thermophotovoltaics are a key technology in the search for the ability to power small scale autonomous systems. In this work, MBE grown GaSb photovoltaic devices are fabricated and tested under AM 1.5 conditions. These devices displayed short circuit current values as high as 40 mA/cm2 but were found to have poor series resistance. The parasitic resistive characteristics were factored out of the measured cell data and it was found that the photocurrent for the fabricated devices could be as much as 6 mA/cm2 higher then the measured short circuit current. An additional layer of metal was added to the reduce the deleterious resistance characteristics, and it was found to lower the series resistance down to a 4 Ω average across almost all of the devices. The average JSC for all of these devices increased to over 30 mA/cm2, with highs well over 40 mA/cm2, a more consistent result than the original single metal deposition devices. Graphene was applied to the originally fabricated devices in an attempt to remove the series resistances issues as well as act as a surface passivation layer. The graphene was able to reduce series resistance by as much as 50% on some of the devices, with a corresponding 6 mA/cm2 increase in short circuit current exhibited. The photocurrent and diode current values were not changed by more than a measurement error, an indication that surface passivaiton may not have taken place. Graphene was a suitable approach for solving the series resistance issue and its use as both a transparent conductive layer and surface passivation material deserve further investigation.Master of Science
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Park, Hyesung Ph D. Massachusetts Institute of Technology. "Application of CVD graphene in organic photovoltaics as transparent conducting electrodes." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/84386.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 184-191).
Graphene, a hexagonal arrangement of carbon atoms forming a one-atom thick planar sheet, has gained much attention due to its remarkable physical properties. Apart from the micromechanical cleavage of highly ordered pyrolytic graphite (HOPG), several alternate methods have been explored to achieve reliable and repeatable synthesis of large-area graphene sheets. Among these, the chemical vapor deposition (CVD) process has been demonstrated as an efficient way of producing continuous, large area graphene films and the synthesis of graphene sheets up to 30-inch has been reported. Similar to graphene research, solar cells based on organic materials have also drawn significant attention as a possible candidate for the generation of clean electricity over conventional inorganic photovoltaics due to the interesting properties of organic semiconductors such as high absorption coefficients, light weight and flexibility, and potentially low-cost, high throughput fabrication processes. Transparent conducting electrodes (TCE) are widely used in organic photovoltaics, and metal oxides such as indium tin oxide (ITO) have been commonly used as window electrodes. Usually used as thin films, these materials require low sheet resistance (Rsh) with high transparency (T). Currently the dominant material used in the industry standard is ITO. However, these materials are not ideal options for organic photovoltaic applications due to several reasons: (1) non-uniform absorption across the visible to near infrared region; (2) chemical instability; (3) metal oxide electrodes easily fracture under large bending, and they are not suitable for flexible solar cell applications; (4) limited availability of indium on the earth leading to increasing costs with time. Therefore, the need for alternative/replacement materials for ITO is ever increasing and ideally need to be developed with the following characteristics: low-cost, mechanically robust, transparent, electrically conductive, and ultimately should demonstrate comparable or better performance compared to ITO-based photovoltaic devices. With superior flexibility and good electrical conductivity, as well as abundance of source material (carbon) at lower costs compared to ITO, in this thesis, we propose that the CVD graphene can be a suitable candidate material as TCE in organic photovoltaic applications, satisfying the aforementioned requirements.
by Hyesung Park.
Ph.D.
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Brinkman, Daniel. "Modeling and numerics for two partial differential equation systems arising from nanoscale physics." Thesis, University of Cambridge, 2013. https://www.repository.cam.ac.uk/handle/1810/244667.
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This thesis focuses on the mathematical analysis of two partial differential equation systems. Consistent improvement of mathematical computation allows more and more questions to be addressed in the form of numerical simulations. At the same time, novel materials arising from advances in physics and material sciences are creating new problems which must be addressed. This thesis is divided into two parts based on analysis of two such materials: organic semiconductors and graphene. In part one we derive a generalized reaction-drift-diffusion model for organic photovoltaic devices -- solar cells based on organic semiconductors. After formulating an appropriate self-consistent model (based largely on generalizing partly contradictory previous models), we study the operation of the device in several specific asymptotic regimes. Furthermore, we simulate such devices using a customized 2D hybrid discontinuous Galerkin finite element scheme and compare the numerical results to our asymptotics. Next, we use specialized asymptotic regimes applicable to a broad range of device parameters to justify several assumptions used in the formulation of simplified models which have already been discussed in the literature. We then discuss the potential applicability of the simulations to real devices by discussing which parameters will be the most important for a functioning device. We then give further generic 2D numerical results and discuss the limitations of the model in this regime. Finally, we give several perspectives on proving existence and uniqueness of the model. In part two we derive a second-order finite difference numerical scheme for simulation of the 2D Dirac equation and prove that the method converges in the electromagnetically static case. Of particular interest is the application to electrons in graphene. We demonstrate this convergence numerically with several examples for which explicit solutions are known and discuss the manner in which errors appear and propagate. We furthermore extend the Dirac system with Poisson's equation to investigate interesting electronic effects. In particular, we show that our numerical scheme can successfully simulate a beam-splitter and Veselago lens, both of which have been predicted analytically to appear in graphene.
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Holder, Jenna Ka Ling. "Quantum structures in photovoltaic devices." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:d23c2660-bdba-4a4f-9d43-9860b9aabdb8.
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A study of three novel solar cells is presented, all of which incorporate a low-dimensional quantum confined component in a bid to enhance device performance. Firstly, intermediate band solar cells (IBSCs) based on InAs quantum dots (QDs) in a GaAs p-i-n structure are studied. The aim is to isolate the InAs QDs from the GaAs conduction band by surrounding them with wider band gap aluminium arsenide. An increase in open circuit voltage (VOC) and decrease in short circuit current (Jsc) is observed, causing no overall change in power conversion efficiency. Dark current - voltage measurements show that the increase in VOC is due to reduced recombination. Electroreflectance and external quantum efficiency measurements attribute the decrease in Jsc primarily to a reduction in InGaAs states between the InAs QD and GaAs which act as an extraction pathway for charges in the control device. A colloidal quantum dot (CQD) bulk heterojunction (BHJ) solar cell composed of a blend of PbS CQDs and ZnO nanoparticles is examined next. The aim of the BHJ is to increase charge separation by increasing the heterojunction interface. Different concentration ratios of each phase are tested and show no change in Jsc, due primarily to poor overall charge transport in the blend. VOC increases for a 30 wt% ZnO blend, and this is attributed largely to a reduction in shunt resistance in the BHJ devices. Finally, graphene is compared to indium tin oxide (ITO) as an alternative transparent electrode in squaraine/ C70 solar cells. Due to graphene’s high transparency, graphene devices have enhanced Jsc, however, its poor sheet resistance increases the series resistance through the device, leading to a poorer fill factor. VOC is raised by using MoO3 as a hole blocking layer. Absorption in the squaraine layer is found to be more conducive to current extraction than in the C70 layer. This is due to better matching of exciton diffusion length and layer thickness in the squaraine and to the minority carrier blocking layer adjacent to the squaraine being more effective than the one adjacent to the C70.
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Belchi, Raphaëlle. "Architectures à base de nanostructures de carbone et TiO₂pour le photovoltaïque." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS329/document.
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Le photovoltaïque est une énergie renouvelable pouvant aider à lutter contre le réchauffement climatique et l’épuisement des ressources fossiles utilisées pour la production d’énergie. La filière émergente à base de matériaux pérovskites (photovoltaïque de 3ème génération) est très prometteuse car elle utilise des matériaux abondants et faciles à mettre en œuvre (technologie bas-coût) et a montré de plus des rendements record compétitifs en peu de temps. Il reste cependant des verrous technologiques à lever afin de pouvoir développer cette technologie à grande échelle. L’un deux consiste à améliorer la couche de TiO₂ qui transporte les électrons et dont les défauts limitent les performances et la durée de vie des cellules photovoltaïques pérovskites. Ce travail propose l’utilisation de matériaux à base de nanostructures de carbone et de TiO₂ pour améliorer le transport et la collecte des électrons au sein de ces cellules photovoltaïques et ainsi améliorer leur rendement. Pour cela, la pyrolyse laser, technique singulière de production continue de nanoparticules, a été adaptée pour l’élaboration de nanocomposites TiO₂/graphène aux propriétés contrôlées. Ces matériaux ont été caractérisés puis intégrés aux cellules photovoltaïques pérovskites qui ont démontré une meilleure efficacité en présence de graphène. Par ailleurs, ce travail présente une architecture innovante à base de nanotubes de carbone alignés verticalement, en vue d’une application pour la collecte des électrons photo-générés des cellules photovoltaïques pérovskites. Les matériaux carbonés présentent donc de fortes potentialités pour l’optoélectronique, et plus particulièrement pour le photovoltaïque de 3ème générationPhotovoltaic is a promising renewable energy to tackle global warming and the depletion of fossil resources. The emerging field of perovskite solar cells (3rd generation photovoltaic) is very attractive because it uses abundant and easy-processing materials (low-cost technology) and provides competitive efficiencies.Still, efforts remain to be performed to develop this technology, especially concerning the improvement of efficient and reliable charge transporting electrodes. Titanium dioxide layer, commonly used for electron extraction, presents defects that limit the performance and lifetime of the perovskite solar cells.This work proposes the use of materials based on TiO₂ and carbon nanostructures to improve the electron transport and collection within the solar cells, in order to enhance the power conversion efficiency. The singular technique of laser pyrolysis, which is a continuous process of nanoparticles synthesis, was adapted to produce TiO₂/graphene nanocomposites with well-controlled properties. These materials have been characterized and integrated into perovskite solar cells that demonstrate an improved efficiency in presence of graphene.Besides, this work presents an innovating architecture based on vertically aligned carbon nanotubes for the electron collection of a perovskite solar cell. We show then the strong potential of carbon materials for optoelectronic, especially 3rd generation photovoltaic
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Mulderig, Andrew J. "Performance and Active Layer Morphology of P3HT-PCPDTBT Organic Photovoltaic Cells." University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1457619609.
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Handloser, Karl Matthias. "Optical investigation of charge carrier dynamics in organic semiconductors and graphene for photovoltaic applications." Diss., Ludwig-Maximilians-Universität München, 2014. http://nbn-resolving.de/urn:nbn:de:bvb:19-168562.
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Azevedo, Joël. "Assemblage contrôlé de graphène et de nanotubes de carbone par transfert de films de tensioactifs pour le photovoltaïque." Phd thesis, Université Paris Sud - Paris XI, 2013. http://tel.archives-ouvertes.fr/tel-00846430.
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Cette thèse est dédiée à l'étude d'une nouvelle méthode de formation de films ultra-minces de nanomatériaux carbonés sur surface. Basée sur le transfert d'un film d'eau stabilisé par des tensioactifs, elle permet notamment la réalisation et l'étude de films de nanotubes de carbone et d'oxyde de graphène (GO) aux propriétés remarquables. L'efficacité de l'approche développée est prouvée au travers de l'ajustement précis des caractéristiques des films. Pour l'assemblage d'objets bidimensionnels cette approche est particulièrement pertinente puisque la planéité des feuillets de GO est conservée quelle que soit leur taille. Les avantages de l'approche ne se limitent pas à la réalisation de monocouches à morphologie contrôlée mais s'étendent à la réalisation de films multicouches d'épaisseur ajustée et de très faible rugosité. De plus, cette approche est modulable et permet le transfert de films de nano-objets sur des surfaces de différentes mouillabilités et de grandes dimensions (transfert à l'échelle de wafers). L'intérêt du graphène oxydé en tant qu'analogue du graphene ne se justifie que par une désoxygénation (réduction) efficace du matériau idéalement complétée par une réparation de sa structure sp². Cette thèse aborde ces deux aspects. Les électrodes transparentes à base d'oxyde de graphène réduit (rGO) réalisées au cours de cette thèse sont parmi les plus performantes du domaine. Les résultats présentés incluent également un travail important sur les caractérisations électriques des feuillets individuels et des films de GO et de rGO. Ainsi, nous avons prouvé qu'il est possible de mesurer leur conductivité sans contact, par voie électrochimique (Scanning Electrochemical Microscopy). Même si les performances des électrodes en rGO n'atteignent pas celles des électrodes en graphène, les films réalisés peuvent d'ores et déjà être intégrés dans des dispositifs photovoltaïques. Nos travaux permettent de contribuer au domaine émergeant des cellules basées sur l'hétérojonction entre film de nano-objets carbonés et silicium. Dans le cadre de cette thèse nous montrons en particulier que les analyses par Time Resolved Microwave Conductivity sont complémentaires des mesures effectuées à l'échelle des cellules photovoltaïques, chacune permettant de caractériser, sous des angles différents, l'efficacité de séparation des charges photo-induites. Les travaux réalisés au cours de cette thèse contribuent aux problématiques dépendantes d'assemblage et d'intégration des nano-objets carbonés dans des dispositifs en ouvrant de nombreuses perspectives dans ces domaines en rapide évolution.
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Dasari, Mallika. "DESIGN, SYNTHESIS, AND CHARACTERIZATION OF NANOCOMPOSITES TO IMPROVE THE PERFORMANCE OF PHOTOVOLTAIC CELLS." OpenSIUC, 2016. https://opensiuc.lib.siu.edu/dissertations/1276.
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My PhD thesis work is to design, synthesize, and characterize inexpensive and reliable nanocomposites for the photovoltaic (PV) devices. Photovoltaic materials utilized in our studies were synthesized using simple and inexpensive methods. The material properties were tailored and optimized to improve the optical absorption and charge transport properties. The PV cells fabricated with these materials exhibited improved power conversion efficiencies (PCE). The origin of charge generation and charge transfer was studied using different photoactive materials such as CdSe quantum dots (QDs), perylene-3, 4, 9, 10-tetracarboxylic-3, 4, 9, 10-dianhydride (PTCDA), poly(3-hexylthiophene) (P3HT), multiwalled carbon nanotubes (MWCNTs), multilayer graphene (MuLG), and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM).
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Wang, Shujun. "Synthesis of Graphene Quantum Dots and Their Applications in Sensing and Light Harvesting." Thesis, Griffith University, 2017. http://hdl.handle.net/10072/366102.
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Graphene quantum dot (GQD) is a derivative of 2D material graphene. It normally refers to small fragments of graphene having lateral size below 100nm. Not only do GQDs inherit some of the wonder properties of bulk graphene, but they possess properties unique from bulk graphene due to the quantum confinement and edge effects. As an emerging material, GQDs presents a new open field for broad
investigations, from synthesis, explanation of properties to promising applications including sensing, bio-imaging, nanomedicine (e. g. drug delivery), energy conversion (e. g. photovoltaic devices and photocatalyst) optoelectronics, spintronics etc. This PhD project is dedicated to three correlated aspects of GQDs: 1) development of new methods for synthesis of GQDs; 2) mechanistic studies of the
photoluminescence (PL) possessed by GQDs, and; 3) the applications of GQDs in sensing and light harvesting.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Engineering
Science, Environment, Engineering and Technology
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Handloser, Karl Matthias [Verfasser], and Achim [Akademischer Betreuer] Hartschuh. "Optical investigation of charge carrier dynamics in organic semiconductors and graphene for photovoltaic applications / Karl Matthias Handloser. Betreuer: Achim Hartschuh." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2014. http://d-nb.info/1050648013/34.
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Saker, Neto Nicolau 1989. "Síntese de grafenos quimicamente modificados e aplicação em células fotovoltaicas orgânicas." [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/248397.
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Orientador: Ana Flávia NogueiraDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química
Made available in DSpace on 2018-08-26T15:49:22Z (GMT). No. of bitstreams: 1 SakerNeto_Nicolau_M.pdf: 15094468 bytes, checksum: d3c20b6e7dbd840a984fe7d8b1b365a8 (MD5) Previous issue date: 2014
Resumo: Entre as alternativas promissoras para a produção de energia elétrica de modo econômico e ambientalmente sustentável está o aproveitamento da energia luminosa do Sol pelo efeito fotovoltaico. Células fotovoltaicas orgânicas fazem parte da mais nova geração de células solares, e prometem ser produzidas em larga escala a custo reduzido. Entretanto, células orgânicas atualmente estão limitadas por eficiências comparativamente baixas. O objetivo deste trabalho é introduzir derivados de grafeno em células solares orgânicas poliméricas como aceitador de elétrons e transportadores de cargas na camada absorvedora de luz, em substituição parcial ou total aos atuais materiais mais empregados, derivados de fulerenos C60 e C70. Óxido de grafeno (GO) foi obtido a partir da oxidação de grafite mineral utilizando-se o método de Hummers com modificações. Amostras de grafenos quimicamente modificados (CMGs) foram sintetizadas pela reação direta de dispersões de óxido de grafeno com ácido 2-tiofenoacético (TAA) por uma esterificação de Steglich, ou após um tratamento de óxido de grafeno em meio básico com hidróxido de tetrabutilamônio (TBAH). Os CMGs apresentaram funcionalização bastante limitada, tendo ocorrido principalmente uma desoxigenação dos derivados de grafeno. Ainda assim, os CMGs puderam ser dispersos no solvente usado para a preparação da camada absorvedora de luz, 1,2-diclorobenzeno. Os materiais sintetizados foram aplicados em células poliméricas baseadas no polímero poli(3-hexiltiofeno) (P3HT) e no derivado de fulereno [6,6]-fenil-C71-butanoato de metila (PC71BM), e os parâmetros fotovoltaicos resultantes foram obtidos. As eficiências de conversão fotovoltaicas em células contendo CMGs foram potencialmente limitadas pelo processo de desoxigenação
Abstract: Among the promising alternatives for the economically and environmentally sustainable production of electrical energy is the harnessing of the Sun's luminous energy by the photovoltaic effect. Organic photovoltaic cells are part of the newest generation of solar cells, promising large-scale production at reduced costs. However, organic cells are currently limited by comparatively low efficiencies. The objective of this work is to introduce graphene derivatives in polymer organic solar cells as electron acceptors and charge transporters in the light-absorbing layer, partially or fully replacing the currently most used materials, derivatives of C60 and C70 fullerenes. Graphene oxide (GO) was obtained by the oxidation of mineral graphite using a modified Hummers' method. Samples of chemically modified graphenes (CMGs) were synthesized by the direct reaction of graphene oxide dispersions with 2-thiopheneacetic acid (TAA) via Steglich esterification, or after treatment of graphene oxide in basic medium with tetrabutylammonium hydroxide (TBAH). The CMGs showed very limited functionalization and the main occurrence was a deoxygenation of the graphene derivatives. Still, the CMGs were dispersible in the solvent used for the preparation of the light-absorbing layer, 1,2-dichlorobenzene. The synthesized materials were applied in polymer cells based on the polymer poly(3-hexylthiophene) (P3HT) and the fullerene derivative [6,6]-phenyl-C71-butyl methyl ester (PC71BM) and the resulting photovoltaic parameters were obtained. The photovoltaic conversion efficiencies for cells containing CMGs were potentially limited by the deoxygenation process
Mestrado
Quimica Organica
Mestre em Química
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Vai, Vannak. "Planning of low voltage distribution system with integration of PV sources and storage means : case of power system of Cambodia." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAT044/document.
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La consommation d'énergie augmente d'année en année en raison de la croissance de la population et des conditions économiques. Afin de répondre aux besoins de la population et de la société d'utiliser l'électricité, le Gouvernement Cambodgien a mis en place la politique de promotion et d'encouragement du développement de l’électrification ; tous les villages auront de l'électricité d'ici 2020 et au moins 70% des domiciles auront accès à la bonne qualité du réseau électrique d'ici 2030. Pour réussir ces objectifs, l'étude et le développement de la méthodologie du réseau de distribution basse tension (BT) sont étudiés. Cette thèse étudie la planification du réseau de distribution BT avec intégration de Photovoltaïque (PV) et de stockage d’énergie de batterie (BES). La première partie est développée la méthode de planification à long terme pour tacler le défi de l'incertitude sur la charge en zone urbaine ;le nouvel algorithme a été développé pour rechercher l'architecture optimale de minimisation du coût d’investissement (CAPEX) et d’exploitation (OPEX) qui respecte l'ensemble de contraintes topologies et électriques (courant et tension) grâce à la programmation linéaire mixte en nombres entiers à contraintes quadratiques (PLMNECQ), le plus court chemin , first-fit bin-packing, et la méthode de Monte-Carlo. La deuxième partie est traité de l'extension de la zone de couverture de l'électricité avec deux solutions possibles, sont le renforcement du réseau et l'intégration de PV-BES pour le village rural ; l'algorithme génétique (GA) et la technique itérative ont été codés pour rechercher l’emplacement et la capacité. La dernière partie du travail est concentrée sur la planification du réseau de distribution résidentielle BT pour les zones non électrifiées aux rural et urbain grâce à l'architecture optimale et l'intégration de PV-BES sur l'horizon de planificationThe energy consumption is increasing year by year due to the growth of population and the economic conditions. In order to meet the need of population and society to use electricity, the Cambodian government has established the policy to promote and encourage the development of electrification; all the villages will have electricity by the year 2020, and at least 70% of households will have access to grid quality by the year 2030. To achieve these goals, the study and development of methodology on the Low-Voltage (LV) distribution system are investigated. This thesis studies the planning of LV distribution system with integration of Photovoltaic (PV) and Battery Energy Storage (BES). The first part is developed the long-term planning method to tackle the challenge of load demand uncertainty in urban area; the novel algorithm was developed to search for the optimal architecture of minimizing the capital expenditure (CAPEX) and the operation expenditure (OPEX) which respects to the set of topology and electrical (current and voltage) thank to mixed integer quadratically constrained programming (MIQCP), shortest-path, first-fit bin-packing, and Monte-Carlo method. The second part is dealt with the extension of electricity coverage area with two possible solutions which are grid reinforcement and integration of PV-BES for rural village; the Genetic algorithm (GA) and iterative technique were coded to search for location and sizing. The last part is concentrated on the planning of residential low-voltage distribution system in both rural and urban for non-electrified area thanks to the optimal architecture and PV-BES integration over the planning horizon
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Arnaud, Marc-Alexandre Dimitri. "Modélisation multi-échelle de polymères conjugués pour le photovoltaïque organique : confrontation expérience / théorie." Thesis, Pau, 2013. http://www.theses.fr/2013PAUU3053/document.
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Ce travail de recherche prédictive, couplé à des synthèses expérimentales, a pour but d'anticiper la bonne adéquation entre un nouveau polymère donneur de type P3HT et un composé accepteur innovant à base de graphène. Cette étude a notamment porté sur i) la bande d'absorption du polymère donneur « low band gap », ii) sa robustesse face à la dégradation (cristallinité, résistance à l'oxydation), iii) la modulation des propriétés électroniques d'un dérivé de graphène (accepteur) en adéquation avec le donneur. Les résultats montrent que les polythiophènes ayant un substituant éther OR permettent l'amélioration de la conjugaison, de la rigidité, de la cristallinité et de la photostabilité tout en étant électroniquement compatible avec l'hexabenzocoronène fonctionnalisé (acide caorboxylique). De plus, ce nouvel accepteur sera pleinement compatible avec une électrode de graphite grâce à sa prédisposition à l'empilement colonnaireThis predictive research work, combined with an experimental study, aims at anticipate the behavior of a new donor :acceptor pair constituted by a P3HT-type of polymer and an innovative graphene-based acceptor material (HBC). This study is particularly interested in i) the absorption band of the donor (a « low band gap » polymer) and ii) its resistance towards degradation (cristallinity, oxidation stability), and finally iii) the modulation of the electronic properties of the acceptor, in keeping with those of the donor. Results show that polythiophenes grafted with an –OR group improve both conjugation, rigidity, cristallinity and photostability, in addition to their great electronic compatibility with functionalized HBCs. Besides, this new acceptor material will be fully compatible with a graphite electrode, thanks to its columnar structuration
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Tseng, Chi-Yang, and 曾紀洋. "NFSI Doped CVD-Graphene for Enhancing the Efficiency of Graphene-Silicon Schottky Photovoltaics." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/90636125853274312891.
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碩士國立臺灣師範大學
化學系
100
Graphene, a single layer of sp2-bonded carbon atoms, demonstrates many unique physical properties such as high mobility of charge carriers, high thermal conductivity, excellent mechanical and optical properties, so it is expected to be used in transistors, transparent electrodes, sensors and photovoltaic device. Recently, a lot of effort has been focused on improving electric properties of graphene and exploring the new optoelectronic applications. In this study, monolayer graphene was doped with NFSI ((C6H5SO2)2NF) molecular by using chemical doping method. After modified with NFSI, the conductivity of NFSI-graphene has been increased dramatically and high transmittance of monolayer graphene was still preserved. In Raman spectra, the G and 2D band peak position of NFSI-graphene is shift from 1581 to 1586 cm-1、2631 to 2643cm-1, respectively compared to pristine graphene. Furthermore, from the FET and Hall measurement, we found that the hole carrier density of NFSI-graphene was highly increased in consistent with the result of p-type doping. However, the decreases of mobility of NFSI-graphene was could be attributed to impurity scattering. Besides, we also demonstrate monolayer NFSI-graphene/n-silicon Schottky-junction solar cells. Under AM1.5 illumination, the NFSI-graphene/n-silicon Schottky device exhibit a higher power conversion efficiency (PCE) of 3.56% than that of pristine-graphene 1.74%. Current-voltage and capacitance-voltage measurement showed that the enhancement of PCE and Voc is due to increases of the device cell’s built-in potential affected by higher carrier density of NFSI-graphene.
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Lee, Wei-Chen, and 李威辰. "Sunlight-activated Graphene-heterostructure Transparent Cathodes：Enabling High-performance n-graphene/p-Si Schottky Junction Photovoltaics." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/82319427303022639214.
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碩士國立臺灣大學
材料科學與工程學研究所
103
Graphene, which consists of a single atom-thick layer of carbon, has a lot of attracting properties such as tunable work function, high transparency and high carrier mobility etc. All these properties make graphene be a promising material to replacing widely-used ITO as transparent conducting electrode. However, compared to well-developed graphene-based anodes, fabricating a stable graphene-based cathode is more difficult because n-type dopants for graphene have limited thermal and chemical stabilities and are also sensitive to the influence of ambient environment. In the first part of this thesis, we developed a novel “sunlight-activated” graphene-heterostructure transparent electrode. Besides, TiOx was found to be an effective n-type dopant for graphene by surface charge transfer process. With only costing a small amount of ultraviolet, TiOx will photo-generates charges under illumination then are transferred toward graphene and further doped it. This photoactive TiOx/graphene heterostructure transparent electrode exhibits excellent tunable electrical properties and is appropriate to fabricate an n-graphene/p-silicon Schottky junction solar cell, even achieving a record-high power efficiency of graphene/p-silicon structure. In the second part, we aim to improve the performance of device in the first part. With more suitable anti-reflective layers, back contact electrodes, and surface passivation, we demonstrate a “trap-free” photoactive n-graphene/p-Si Schottky solar cell with higher short circuit current and open circuit voltage. This device is also an ideal candidate for future derivatives of tandem cells.
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Ali, Alaa Yousif. "Low temperature synthesis of graphene as an alternative transparent electrode for large area organic photovoltaics." Thesis, 2020. http://hdl.handle.net/1959.13/1417346.
Full textAbstract:
Research Doctorate - Doctor of Philosophy (PhD)This thesis presents a systematic study of the fabrication and optimisation of graphene films as an alternative electrode for large area organic photovoltaics (OPVs). It is mainly focused on the growth of graphene layers at low temperatures (below 700 °C) using chemical vapour deposition (CVD) method. A routine procedure was developed to produce large-area graphene films of centimetre size. Firstly, we demonstrated that we could fabricate multi-layers of graphene films utilising organic solvent residual in a polymer film matrix as the carbon source. The polymer matrix is poly (methyl methacrylate) (PMMA), which can be dissolved in a polar solvent, such as, chlorobenzene. When PMMA is dissolved in chlorobenzene and drop-cast as a film into a quartz slide, a small amount of chlorobenzene is trapped in the PMMA. When heating up the quartz slide to 180 °C, chlorobenzene molecules evaporate and land on copper foils, which is maintained at much high temperature in the growth zone in the CVD system. Copper (Cu) catalytically promotes chlorobenzene dissociation and formation of micron-sized graphene domains at the different growth temperature. After a parametric study, we found that at 75 sccm (standard cubic centimeters per minute) of H2 flow during the growth while maintaining the Cu foil at 600 °C, produced the optimal graphene growth conditions. We also compared PMMA dissolved in other organic solvents and as carbon sources at low-temperature growth ~450 °C for deposition of the graphene layers onto a Cu catalyst. An optimisation process was carried out to see the effects of other carbon sources on the quality of graphene films. The carbon sources studied were both aliphatic solvents (dichloromethane, chloroform, acetone) and aromatic solvents (p-xylene, toluene, o-xylene, chlorobenzene, dichlorobenzene), to probe the growth mechanism of graphene formation. However, none of the other solvents produced a better quality of graphene than chlorobenzene. Lastly, graphene films were used to replace indium tin oxide (ITO) in the OPV device fabrication. The results showed that working devices were successfully made for both small and large areas OPVs.
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Chang, Jan-Kai, and 張然凱. "Toward Fully Solution-Processed Organic Photovoltaics: Spectroscopic Studies on Electronic Structures for Organic Solar Cells with Graphene Electrodes." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/62019909503446059326.
Full textAbstract:
博士國立臺灣大學
光電工程學研究所
103
Heterostructures based on organic semiconductors are fundamentally different and more flexible than those made from conventional covalently bonded inorganics. In particular, organic bulk heterojunction (BHJ) solar cells have been known for their potential as a time-saving, low-cost and lightweight technology. In this work, the electronic properties of internal junctions including donor-acceptor heterojunction, organic/organic and organic/inorganic junctions at each interface within a BHJ solar cell have been studied in detail via photoemission spectroscopy. Promising ways for performance improvement have been developed based on the incorporation of energy ladder, interfacial modification, as well as forming an energetically favorable band alignment by tuning the work function of electrodes. In addition to investigations from the aspect of electronic structure, loss mechanisms induced by interfacial barrier due to band mismatch have been clarified with better understanding of capacitive response provided by impedance spectroscopy. A facile approach that can transfer high-quality graphene along with effective doping was also established based on aqueous intercalation process, enabling n-doped and p-doped graphene for transparent electrode applications. Accordingly, the incorporation of both graphene anode and graphene cathode was successfully carried out to achieve high-performance organic BHJ solar cells with semi-transparency, showing high compatibility with solution-processed organic optoelectronics. Such proposed scheme benefited the integration of graphene with organic BHJ solar cells, which was further developed into a vacuum-free process for device fabrication. Therefore, the development of fully solution-processed semitransparent device distinguishes organic BHJ solar cells as a feasible green energy source for flexible optoelectronics, wearable battery as well as facade integration.
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Panthani, Matthew George. "Colloidal nanocrystals with near-infrared optical properties : synthesis, characterization, and applications." 2011. http://hdl.handle.net/2152/19825.
Full textAbstract:
Colloidal nanocrystals with optical properties in the near-infrared (NIR) are of interest for many applications such as photovoltaic (PV) energy conversion, bioimaging, and therapeutics. For PVs and other electronic devices, challenges in using colloidal nanomaterials often deal with the surfaces. Because of the high surface-to-volume ratio of small nanocrystals, surfaces and interfaces play an enhanced role in the properties of nanocrystal films and devices.
Organic ligand-capped CuInSe2 (CIS) and Cu(InXGa1-X)Se2 (CIGS) nanocrystals were synthesized and used as the absorber layer in prototype solar cells. By fabricating devices from spray-coated CuInSe nanocrystals under ambient conditions, solar-to-electric power conversion efficiencies as high as 3.1% were achieved. Many treatments of the nanocrystal films were explored. Although some treatments increased the conductivity of the nanocrystal films, the best devices were from untreated CIS films. By modifying the reaction chemistry, quantum-confined CuInSeXS2-X (CISS) nanocrystals were produced. The potential of the CISS nanocrystals for targeted bioimaging was demonstrated via oral delivery to mice and imaging of nanocrystal fluorescence.
The size-dependent photoluminescence of Si nanocrystals was measured. Si nanocrystals supported on graphene were characterized by conventional transmission electron microscopy and spherical aberration (Cs)-corrected scanning transmission electron microscopy (STEM). Enhanced imaging contrast and resolution was achieved by using Cs-corrected STEM with a graphene support. In addition, clear imaging of defects and the organic-inorganic interface was enabled by utilizing this technique.text
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Lin, Wai-Chen, and 林渭澄. "Preparation of Fluorinated Graphene Nanosheets for Polymer Photovoltaic Devices." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/35475q.
Full textAbstract:
碩士國立交通大學
平面顯示技術碩士學位學程
103
In this study, we describe the preparation of fluorinated graphene nanosheets (FGS) through photoexfoliation from fluorinated graphite (FG) in liquid phase. We discovered that the use of UV radiation upon the FG dispersion in N-methyl-2-pyrolidone could facilitate the exfoliation of FGS. From the analysis of the images obtained from transmission electron microscopy and atomic force microscopy, the average thickness of the FGSs was ca. 3 nm, which was thinner than that of the nanosheets prepared using conventional sonication approach. Furthermore, the FGS can be uniformly deposited on the substrates by spin coating and behaved as an effective electron transport layer of polymer solar cells (PSCs). The as-prepared inverted PSC exhibited an open circuit voltage of 0.53 V, a short circuit current density of 10.22 mA cm-2 and a fill factor up to 53.7%., resulting in a power conversion efficiency (PCE) of 2.91%. The PCE of the PSC containing FGS prepared through sonication was 1.73%. The lower efficiency was probably due to the higher contact resistances, which may be originated from the higher thickness of the FGS.
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Wu, Chi-Chan, and 吳極湛. "Microwave-assisted synthesis and photovoltaic performance of CuInSe2/graphene nanocomposites." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/14461456757809140672.
Full textAbstract:
碩士元智大學
化學工程與材料科學學系
99
In this thesis, we reported the preparation of hybrid of CISe nanoparticles decorated on the soluble graphene and their mixtures with conjugated polymer P3HT served as the active layer of hybrid solar cells. The graphene oxide nanosheets were prepared by modified Hummer’s method. The results of Raman spectra, FT-IR spectra and XRD diffraction indicated the successful preparation of GO. The CISe nanoparticles were prepared by microwave-assisted solvothermal methods which the reaction time was shorten to only 30 min. In order to improve the dispersion of GO in hydrophobic organic solvents, the SPFG was synthesis by GO treated with phenyl isocyanate. The SPFG/CISe nanocomposities (SGCISe) was prepared by microwave-assisted synthesis. The hybrid solar cells were fabricated with different mixture material such as P3HT/CISe, P3HT/SPFG and P3HT/SGCISe. As the P3HT/SPFG ratio is 1:0.1, he best performance of open circuit voltages (Voc), short-circuit current density (Jsc), fill factor (FF), and efficiency (PCE) obtained at optimized conditions are 1.05 V, 1.3×10-2 mA/cm2, 0.30, and 4×10-3 %, respectively.
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Lin, Shih-Wei, and 林士惟. "Gold Nanoparticle-Decorated Graphene Oxide Nanocomposites for Plasmonic-Enhanced Polymer Photovoltaic Devices." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/18199880237330522308.
Full textAbstract:
碩士國立交通大學
顯示科技研究所
102
In this study, we used gold nanoparticle-decorated graphene oxides (AuNP/GOs) nanocomposites as the hole transport layer (HTL) in organic solar cells. We reduced gold ions to Au NPs by sodium citrate and the resulting Au NPs were adhered to the surface of GOs. In order to avoid aggregation of the Au NPs, the surface of the nanoparticles were further modified by thiol-ligands. The AuNP/GO nanocomposites were further characterized by transmission electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy. Organic photovoltaic devices (OPVs) containing Au NP/GOs composites as the HTLs were also fabricated. Compared to the reference device with pure GOs, the short-circuit current (Jsc) was improved from 8.26 to 10.44 mA/cm^2, and FF was enhanced from 64.5% to 66.8%. While open voltage (Voc) remained unchanged, the overall power conversion efficiency (PCE) of the OPVs fabricated with AuNPs/GO was enhanced from 3.26% to 3.98%. We contributed the device enhancement to the effect of localized surface plasmon resonance induced by AuNPs/GO compositions.
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Mahakul, Prakash Chandra. "Fabrication and Characterization of Carbon Nanotubes and Graphene based Organic Photovoltaic Cells." Thesis, 2018. http://ethesis.nitrkl.ac.in/9816/1/2018_PhD_PCMahakul_512PH104_Fabrication.pdf.
Full textAbstract:
The development of photovoltaic cell (PVC) architecture from economically abundant materials with lower fabrication cost with better performance is of great research interest for next generation optoelectronics. In class better unique physical properties of CNTs as well as the exposed dual surfaces of graphene has been utilised by blending them in a π-conjugated polymer (P3HT) for better carrier transport of charge carriers as well as efficient exciton dissociation. The structural properties of MWCNTs and/or graphene polymer composites have been investigated for photovoltaic applications. Better solar cell performance has been observed with efficiency as high as 4.3% and short circuit current density of 11.77 mA/cm2. Formation of more heterojunction sites as well as the conductive network created by MWCNT and/or reduced graphene in the composite has been attributed for the better performance of the solar cell. Improvement in the observed open-circuit voltage in the devices has been attributed to the increase in the HOMO level of the composites post-filler introduction. MWCNT and rGO incorporated PEDOT:PSS ternary composites has been investigated for transparent conductor applications in plastic solar cells. The poor fill factor observed signifies that there are lots of potential in the material for photovoltaics application. However, further investigation in device structure and controlling their content in the composite is needed for further enhancement in the device performance.
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Tsai, Cheng Lung, and 蔡丞龍. "Hybrid photovoltaic devices based on the reduced graphene oxide-based polymer composite and n-type GaAs." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/57158947170290048754.
Full textAbstract:
碩士國立彰化師範大學
光電科技研究所
100
e present a hybrid photovoltaic device based on GaAs and poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) (PEDOT:PSS) having the reduced graphene oxide (RGO). It is found that conductivity of RGO-doped PEDOT:PSS samples is 27 times higher than that of PEDOT:PSS at 300 K. The improvement of electrical conductivity is considered to mainly come from the mobility enhancement. The carrier mobility in RGO-doped PEDOT:PSS samples exhibits unexpectedly strong temperature dependence, implying the domination of tunneling (hopping) at low (high) temperatures. An exhibition of high mobility of RGO-doped PEDOT:PSS samples is attributed to the increase of the spacing between molecules. In addition, this RGO-doped PEDOT:PSS/GaAs device shows good rectifying behavior with ideality factor of 1.8. The enhanced power conversion efficiency of the PEDOT:PSS/GaAs device was observed by RGO doping. The high photocurrent density originates from high-mobility hole transport combined with long-lifetime electron trapping in the RGO-doped PEDOT:PSS film.
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Bepete, George. "Chemical vapor growth of nitrogen doped carbon nanotube and graphene materials for application in organic photovoltaic devices." Thesis, 2014.
Find full textAbstract:
Application of carbon nanomaterials like fullerene, carbon nanotubes, and graphene in solar
cells using solution processable methods presents a great potential to reduce the cost of
producing electricity from solar energy. However, carbon nanotubes and graphene materials
are predominantly metallic and this limits their function in organic photovoltaic devices
(OPVs) where semiconducting behavior is required. Doping of carbon nanomaterials is a
well-known method for making them semiconducting. Doping of carbon nanomaterials with
nitrogen and boron can tune their properties to suit the requirements for use in photovoltaic
applications as n-type and p-type semiconducting materials, respectively. Indeed, the use of
nitrogen doped and boron doped carbon nanotubes in organic solar cells together with
fullerene acceptors can improve the current density of the OPV devices.
Nitrogen doping of carbon nanotubes can be achieved by using nitrogen-containing precursor
materials during chemical vapor deposition. However the doping of carbon nanotubes with
nitrogen does not automatically make them n-type materials; they remain metallic unless a
large amount of quaternary type nitrogen is incorporated in the carbon nanotubes. In this
work we have developed a method to control the type of nitrogen that is incorporated in
CNTs by using an appropriate synthesis temperature and use of oxygen-containing carbon
precursors during the chemical deposition of carbon nanotubes. Quaternary N was
incorporated in a CVD process when high temperatures and a high concentration of O in the
precursor materials were used. We also showed that the type and amount of N can be
changed from pyrrolic and pyridinic-N-oxide to pyridinic N and quaternary N by annealing N
doped carbon nanotubes at temperatures above 400°C. At temperatures above 800°C most of
the nitrogen is converted to quaternary nitrogen.
N-CNT thin films were used in OPVs so as to modify the ITO electrode and transform it into
a 3D electrode. The resulting effect was an improved short circuit current density in the
devices containing an N-CNT thin film that was placed on top of the ITO electrode. A
reduction in efficiency losses in OPVs at increasing light intensity was observed in the NCNT
ITO modified electrode OPVs. This is a remarkable finding when considering that one
of the main problems hindering commercialization of OPVs is the loss of efficiency at high
light intensities. We related these effects to the efficient charge collection by the modified
ITO electrode. Incorporation of N-CNTs in the bulk heterojunction layer of the OPV device
resulted in poor performance when compared to an OPV device made without N-CNTs. This
effect is caused by shorting of the OPVs. We used a method of incorporating N-CNTs whilst
minimizing shorting and this showed potential for better performance.
A study on the attempted doping of graphene with B to make it a p-type material showed that
in the presence of a nitrogen carrier gas, BN instead of B was incorporated in graphene. This
remarkable finding enabled us to grow a p-type graphene with a possible a band gap opening.
This was corroborated by XPS and Raman spectroscopy studies of the material. This BN
doped graphene material showed potential as a possible replacement of PEDOT:PSS as a
hole transport material in OPVs. The BN doped graphene material can match the
performance of PEDOT:PSS when the level of BN doping in graphene is increased.
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HSU, JING LIANG, and 許景喨. "Effects of Hole Transport Layer of PEDOT:PSS Simultaneously Doped with Graphene Oxides and Gold Nanoparticles on Polymer Photovoltaic Cells." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/39978704754811426579.
Full textAbstract:
碩士國立中正大學
機械工程學系暨研究所
100
Because of the ability of graphene oxides (GOs) in reduction electron-hole recombination rate and the feature of gold nanoparticles (Au-NPs) for surface plasma resonance, this study aims to investigate the feasibility of performance enhancement of an organic photovoltaic (OPV) device through doping both GOs and Au-NPs in the PEDOT:PSS hole transport layer. Results show this arrangement can effectively increase the device’s efficiency. This study starts from finding a suitable doping amount of GOs in the PEDOT:PSS. It was found that there was a 30% efficiency enhancement at the weight ratio of 5 to 1 (PEDOT:PSS to GOs). In addition to its ability in reducing electron-hole recombination rate, the increase of surface roughness of the resulting PEDOT:PSS/GOs layer is believed also playing a positive role on the performance enhancement. Then, the effect of Au-NPs, with an average diameter of 19 nm, on the PEDOT:PSS/Au-NPs was studied individually. Results showed that both the surface roughness and the photoluminescence (PL) intensity of the Au-NPs doped PEDOT:PSS layer were increased and there was a 25% enhancement in device efficiency when the PEDOT:PSS/Au-NPs layer was prepared under the weight ratio of 10 : 1 (PEDOT:PSS to Au-NPs aqueous solution). Finally, the effect of PEDOT:PSS simultaneously doped with GOs and Au-NPs was examined. Results showed, compare with the case that PEDOT:PSS doped only with GOs, this arrangement could increase the device efficiency 24% further.
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Reis, Gabriela Rodrigues Egídio. "Desenvolvimento de superfícies para sistemas fotovoltaicos de elevado rendimento." Master's thesis, 2015. http://hdl.handle.net/10316/38960.
Full textAbstract:
Dissertação de Mestrado Integrado em Engenharia Mecânica apresentada à Faculdade de Ciências e Tecnologia da Universidade de CoimbraEste estudo incidiu sobre o desenvolvimento de superfícies para a produção de um sistema fotovoltaico de elevado rendimento. Por um lado, estas superfícies foram otimizadas de modo a maximizar a sua área específica. Por outro lado, devido às suas excelentes propriedades foram desenvolvidos filmes finos à base de grafeno para revestir as superfícies com vista à sua utilização em células fotovoltaicas. Filmes bicamada de carbono e níquel, e filmes de níquel com diferentes teores em carbono, foram depositados por pulverização catódica magnetrão. Os filmes produzidos foram caraterizados com o objetivo de avaliar a sua rugosidade, espessura e tipo de morfologia, identificar as fases cristalinas presentes e confirmar a presença de grafeno através da análise por espectroscopia de Raman. Foram efetuados tratamentos térmicos para avaliar a sua possível contribuição para a formação de materiais à base de grafeno. Os filmes mais promissores foram analisados em termos de molhabilidade e condutividade. A microtopografia otimizada neste trabalho permite uma maior captação de energia solar, captação essa que é essencial para as células fotovoltaicas do sistema em desenvolvimento. Os filmes de carbono e níquel, com espessuras entre 120 e 350 nm, possuem tamanho de grão nanométrico e rugosidades superficiais médias da ordem de 1-2 nm. Após deposição, a fase Ni cúbica de faces centradas é a única fase detetada por difração de raios X. A presença de carbono amorfo é também comprovada pelos espectros de Raman. Nos filmes tratados termicamente é possível identificar picos Raman característicos do grafeno. A molhabilidade dos filmes mais promissores indica um aumento do caracter hidrofílico após tratamento térmico, o que corrobora a presença de materiais à base de grafeno.
This study focused on the development of surfaces for producing photovoltaic cells with high power conversion efficiency. On one hand, these surfaces were optimized in order to maximize its specific surface area. On the other hand, due to its excellent properties thin films based on graphene were developed to coat these surfaces aiming at their use in photovoltaic cells. Carbon and nickel bilayer films, and nickel films with different carbon content were deposited by magnetron sputtering. The films produced were characterized in order to evaluate their roughness, thickness and type of morphology, to identify the crystalline phases and to confirm the presence of graphene through Raman spectroscopy. Heat treatments were carried out to evaluate their possible contribution to the formation of graphene based materials. The most promising films were analyzed in terms of wettability and conductivity. The microtopography optimized in this work allows solar energy harvesting to be increased, which is essential for the photovoltaic system under development. The carbon and nickel films with thicknesses between 120 and 350 nm, possess nanometer grain size and average surface roughness close to 1-2 nm. After deposition, the Ni face-centered cubic phase is the only phase detected by X-ray diffraction. The presence of amorphous carbon is also confirmed by Raman spectra. In the heat treated films, Raman peaks characteristic of graphene can be identified. The wettability of the most promising films indicates an increased hydrophilic character after heat treatment, which confirms the presence of graphene based materials.
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CHEN, BO-CHENGE, and 陳柏丞. "A Study on Power Generation Characteristics of the Photovoltaic Module with Graphite Composite Material Using Outdoor Experiment and Numerical Calculation." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/b8ftjp.
Full textAbstract:
碩士國立高雄應用科技大學
模具工程系
106
Silicon solar photovoltaic module, powergeneration efficiency is seriously affected bytemperature, because the packaging of solarmodules of the material pet,EVA,Tedlar functionis not as a thermal use, so that when the solarphotovoltaic module to generate electricity, thetemperature continues to rise, it is difficult to heatthe package material, Therefore, it is necessaryto improve the thermal performance of solarphotovoltaic modules. This experiment uses the high conductive material characteristics of the graphite paper insulation, attached to the solar photovoltaic module siliconchip on the back as the endothermic area, andthe other end extends to the outside of themodule as a heat dissipation area, by adding thegraphite paper material to create a new coolingpath, To improve the solar photovoltaic module bythe continuous rise of solar radiation temperature, reduce the operating temperature of powergeneration, to achieve the increase in powerefficiency.In order to pursue experimental results close toreality, the study was conducted in outdoorenvironment. Early to find a better graphite paperlaying heat dissipation area and endothermic area, set the experimental influence factors arefixed graphite endothermic area, the paperdiscusses the heat dissipation area of graphiteand solar module area ratio a_∞/a. Fixed heatdissipation area, the paper discusses the ratio ofa_b/a area to solar module area.After getting better graphite paper laying method,using the obtained better graphite paper laying method in natural convection and forcedconvection under the experimental setup,measuring the solar photovoltaic module powergeneration power than p/p_0 and averagetemperature influence degree, The natural heatconvection coefficient h of the graphite solarphotovoltaic module and the nonimproved solarphotovoltaic module can be obtained by thenumerical calculation method, and the degree ofheat dissipation caused by graphite paper islearned. Experimental results show that the heatdissipation area of a graphite paper afterCASE1C has a moderating value, indicating thatthere is no great benefit to continue to increasethe heat dissipation area, so the better heatdissipation area of graphite paper and solarmodule area than a_∞/a is 0.2147. Due to the limitation of the size of the graphitepaper area, the Experiment II will be defined inthe case of case1c heat dissipation area, caneffectively use the better endothermic area, theexperimental results show that the third chip isnot much benefit, so the better endothermic areais set on the second chip, The a_b/a of the heatabsorbing area of the graphite paper and thesolar module area ratio is 0.399.Second, the experiment and experiment twoobtained the better graphite paper solarphotovoltaic module design, used to comparewith the normal solar photovoltaic modulegeneration efficiency, experimental results showthat adding graphite paper cooling after theoverall power efficiency increased by 2%.
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ROMANO, VALENTINO. "Two-dimensional materials for energy storage and generation." Doctoral thesis, 2019. http://hdl.handle.net/11570/3147646.
Full textAbstract:
Energy is probably the most important factor influencing our everyday life. In fact, we need energy to power up our houses, vehicles, buildings and electronic devices. Storage and generation are the fundamental factors that influence the ways energy can be deployed and produced, so careful strategies have to be designed for their optimization. In particular, the materials used for these technologies should be earth abundant, environmental friendly and cheap. All these requirements are met by two-dimensional (2D) materials (i.e., graphene, transition metal dichalcogenides, etc.), that are currently representing a viable solution to the energy management. In this context, the research works presented in this thesis concern the use of 2D materials in both energy storage and generation devices. In particular, the thesis is organized as follows: Chapter 1 describes the discovery, properties, production and some applications of 2D materials (in particular graphene and transition metal dichalcogenides). Chapter 2 concerns the use of 2D materials in energy storage applications, specifically in electrochemical double layer capacitors. The working principle and main properties of this kind of devices will be thoroughly introduced. Herein, two projects are reported concerning the use of graphene flakes (produced through a wet-jet milling system) as active material for the fabrication of electrodes for electrochemical double layer capacitors. The first project is about the physico-chemical effects raising from the flow of the electrolyte ions on the graphene flakes surface. Our results show that graphene flakes act as “ion sliding” surfaces for the electrolyte ions. The second project, presented in this chapter, shows that the graphene flakes produced by wet-jet milling can be used for the design of high-areal performance electrodes for flexible supercapacitors. These projects are the results of a collaboration with Doctor Francesco Bonaccorso (Istituto Italiano di Tecnologia, Genova, Italy). Chapter 3 deals with energy generation devices, specifically perovskite solar cells. Perovskite materials are now at the centre of huge research efforts for their application in photovoltaics. In this chapter, the main properties of perovskite materials, their use in solar cells and the limits of the resulting devices will be discussed. Finally, the preliminary results on the use of transition metal dichalcogenides flakes in low-dimensional perovskite solar cells will be reported. The aim of this study is to improve the charge collection and the stability of perovskite-based devices. The reported works are carried out in collaboration with Doctor Francesco Bonaccorso (Istituto Italiano di Tecnologia, Genova, Italy), Professor Mohammad Khaja Nazeeruddin (École Polytechnique Fédérale de Lausanne, Sion, Valais) and Professor Giulia Grancini (Università di Pavia, Italy)
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KO, CHENG-CHU, and 柯承初. "Investigation of Photovoltaic Properties and Equivalent Circuit Impedance Analysis for Dye-sensitized Solar Cell Based on AZO Photoanode and Pt Counter Electrode Modified by Reduced Graphene Oxide under Low Illumination, and Study in Series-Parallel Connection Modules." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/86nyah.
Full textAbstract:
碩士國立雲林科技大學
電子工程系
107
In this thesis, the dye-sensitized solar cells (DSSCs) were fabricated on fluorine doped tin oxide (FTO) glass or flexible indium tin oxide/ polyethylene terephthalate (ITO/PET). The photoanode was double layer structure. Firstly, we deposited the Al-doped zinc oxide (AZO) seed layer on FTO glass by sputter system and then grew the zinc oxide (ZnO) nanorods on the AZO seed layer by hydrothermal method. Finally, we deposited the titanium dioxide (TiO2) on ZnO nanorods by the doctor blade method, the photoanode had been finished. The ZnO nanorods could increase the dye adsorption. In the other part, the platinum (Pt) modified is by reduced graphene oxide (rGO). The rGO is two-dimensional materials, which has a high surface and area-to-volume ratio. The rGO was deposited on platinum counter electrode by the doctor-blade method and it can enhance the electrocatalytic activity of the counter electrode. Finally, we measured the current density-voltage curves of the dye-sensitized solar cell (DSSCs), used electrochemical impedance spectroscopy (EIS) to measure impedance and used field emission scanning electron microscopy (FE-SEM) to observe surface morphology of the DSSCs. This new structure could make dye absorbed in a photoanode increase. We know the current situation by ultraviolet-visible spectroscopy. Consequently, This produced an increase in the photoanode ability to absorb the dye, which in turn increased the cell’s short circuit current density, raising the photovoltaic conversion efficiency from 3.71% to 4.87%. In addition, we made the DSSCs module which connected 2 devices in series and 2 devices in parallel and performed the stability analysis. In addition, The DSSCs was measured under the different light intensities. Corresponding to the results, when the light intensity was reduced from 100 mW/cm2 to 30 mW/cm2, the fill factor and the photovoltaic conversion efficiency were increased from 52.85 % to 63.45 % and 4.01 % to 5.25 %, respectively. The photovoltaic conversion efficiency was grown up to 7.82 % when the DSSCs were operated under T5 fluorescent light which light intensities were 0.2 mW/cm2 - 1.7 mW/cm2.
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Kuo, Chien-Hung, and 郭建宏. "Investigation on Photovoltaic Properties of Flexible Arrayed Dye-sensitized Solar Cell Based on IGZO/ TiO2 Double Layered Structure Modified by Graphene under the Low Illumination and Study on Impedance Analysis and Wireless-based Remote Real-time Monitoring System." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/a6xv27.
Full textAbstract:
碩士國立雲林科技大學
電子工程系
106
In this thesis, a way to improve the photovoltaic conversion efficiency (η) of dye-sensitized solar cell (DSSC) has been provided. The structure was divided into two parts. In the first part, the reduced graphene oxide (RGO) - TiO2 composite was fabricated by using hydro-thermal method, which was acted as the dye - adsorbed layer. In the second part, the indium gallium zinc oxide (IGZO) was deposited between dye-adsorbed layer and electrolyte by using sputter system. The DSSC was investigated by electrochemical impedance spectroscopy (EIS), sun light simulation system, field emission scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), ultraviolet-visible spectrophotometer (UV-Visible), X-ray photoelectron spectroscopy (XPS)/electron spectroscopy for chemical analysis (ESCA), X-ray diffractometer (XRD), Raman spectroscopy and transmission electron microscope (TEM). We investigated the photovoltaic properties, series-parallel connection module, internal interface impedance, surface morphology and energy band diagram of arrayed dye-sensitized solar cell based on RGO - TiO2 /IGZO photoelectrode under low illumination. According to the experimental results, due to the high mobility of RGO, which acted as a bridge and accelerated the electron transportation from conduction band of titanium dioxide to conduction band of fluorine doped tin oxide (FTO) glass. That was to say, probability of electron recombination between photo-generated electrons and oxidized-dye molecule was reduced. Furthermore, the energy band gap of dye-adsorbed layer decreased after introducing RGO, which could extend the wavelength range of absorbed-light. Particularly, the amount of harvesting-light is increased. In addition, the high specific surface of RGO was able to increase the amount of dye-loading. The IGZO film was acted as an energy barrier to prevent I-3 from recombining with electrons, which means that it could reduce the probability of reverse recombination. Those modifications of photoelectrode could improve the short-circuit current density (Jsc) of DSSC. Because the photo-generated electrons were reduced with decrease in illumination intensity, that indicated the scattering among electrons was reduced. In order words, the photoluminescence quantum yield (PLQY) will be increased, and the photovoltaic conversion efficiency of DSSC could increase under lower illumination intensity. Finally, the device was investigated by using the wireless-based remote real-time monitor, stability and life-time by source measure unit (SMU) and LabVIEW from National Instruments.
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YOU, PEI-HONG, and 游培弘. "Investigation on the Photovoltaic Characteristics of Flexible Arrayed TiO2 Dye-sensitized Solar Cell Modified by Graphene and Magnetic Beads Integrated with ZnO Nanowires under the Low Illumination and Study on Impedance Analysis of Large-area Series-parallel Equivalent Circuit." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/xc2mb5.
Full textAbstract:
碩士國立雲林科技大學
電子工程系
105
In this thesis, we focused on the performance improvement of dye-sensitized solar cell (DSSC). First, the zinc oxide nanowires was deposited on the different substrates by using water bath method, such as fluorine-doped tin oxide/glass (FTO/Glass) substrate and the indium tin oxide/polyethylene terephthalate (ITO/PET) substrate. After that, the different contents of graphene oxide (GO) and magnetic beads (MBs) were incorporated into titanium dioxide, which will be deposited on the zinc oxide nanowires film by using spin coating method. The optimal incorporating ratio of GO-MBs-TiO2/ zinc oxide nanowires is investigated for the photoelectrode. On the other hand, we also analyzed the series-parallel connection modules and the effects of low illumination for the photovoltaic properties of DSSC. For optimal device, the surface morphology, film thickness, crystalline phase, the optical and photoelectric properties of composite film will be investigated by scanning electron microscope (SEM), X-ray diffractometer (XRD), UV-visible spectroscopy (UV-vis) and electrochemical impedance spectroscopy (EIS). According to the experimental results, the content of 1.5 mL GO and 0.5 mL MBs for DSSC had the optimal photovoltaic properties performances. The optimal photovoltaic conversion efficiency (η) was 4.46 %. Finally, the DSSC of optimal composite film was investigated under different light intensities, which achieved the higher η of 5.21 % a 10 mW/cm2 illumination. The impedance decreased/increased with the increasing connections of the parallel/series module, which photovoltaic conversion efficiencies were 2.81 % and 4.21%, respectively. When use the large area module (2 series + 2 parallel), which η was 3.02%. The optimal η was 3.93% under 10 mW/cm2 illumination.