Dissertations / Theses on the topic 'Optoelectronic and Photovoltaic'
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Lim, Swee Hoe. "Metallic nanostructures for optoelectronic and photovoltaic applications." Diss., [La Jolla] : University of California, San Diego, 2009. http://wwwlib.umi.com/cr/ucsd/fullcit?p3365871.
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Thesis (Ph. D.)--University of California, San Diego, 2009.Title from first page of PDF file (viewed August 20, 2009). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references.
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Vallés, Pelarda Marta. "Different approaches to improve perovskite-based photovoltaic and optoelectronic devices." Doctoral thesis, Universitat Jaume I, 2022. http://dx.doi.org/10.6035/14104.2022.368259.
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Halide perovskites have had a huge impact on different fields in the last decade due to their versatility and amazing optoelectronic properties. However, there are still some issues to improve towards their future utilization and commercialization. In this thesis, several topics associated with perovskite-based photovoltaic and optoelectronic devices are addressed. The different works contribute to enhance the optoelectronic properties of perovskite quantum dots, to replace the most employed hole transporting material in photovoltaic devices (spiro-OMeTAD) and, moreover, to study a methodology which can be incorporated in up-scaling procedures towards their future commercialization as solar cells.Programa de Doctorat en Ciències
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Ho, Kai Wai. "Evaluation and characterization of efficient organic optoelectronic materials and devices." HKBU Institutional Repository, 2020. https://repository.hkbu.edu.hk/etd_oa/816.
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With the progression towards lighter but larger-display self-sustainable mobile devices, device efficiency becomes increasingly important, owing to the higher power display consumption but at the same time more limitation on the size and volume of energy storage. In this thesis, selected aspects regarding to efficiency of three types of optoelectronic devices, indoor photovoltaics (IPVs), perovskite thin-film transistors (TFTs) and organic light-emitting diodes (OLEDs) have been investigated. IPVs can make off-grid devices self-sustainable by harvesting ambient light energy. Its weak irradiance necessitates high-efficiency IPVs to generate sufficient power. Our work addresses the need of knowing the limit of the device parameters for correct evaluation and understanding the efficiency loss for developing clinical tactics. We delivered a general scheme for evaluating the limiting efficiency and the corresponding device parameters of IPVs under various lights, illuminance and material bandgap. In contrast to the AM1.5G conditions, a maximum power conversion efficiency (PCE) of 51-57 % can be achieved under the optimal bandgap of 1.82-1.96 eV. We also propose using the second thickness peak of interference instead of the first as a better optimal absorber thickness after identifying the finite absorption as the major source of efficiency loss. The work provides insights for device evaluation and material design for efficient IPV devices. The novel hybrid organic-inorganic perovskites have gained enormous research interest for its various excellent optoelectronic properties such as high mobility. TFT as an alternative application to the majorly focused photovoltaics is realized in this work. There are few reports on perovskite TFTs due to wetting issues. By employing polymethacrylates with ester groups and aromatic substituents which provide polar and cation-π interactions with the Pb2+ ions, quality films could be fabricated with large crystals and high electron mobility in TFTs. We further improved the performance by resolving interfacial mixing between the perovskite and the polymer using the crosslinkable SU-8, achieving the highest mobility of 1.05 cm2 V−1 s−1. Subsequently, we cured the grain boundaries using methylamine solvent vapor annealing, suppressing the TFT subthreshold swing. The work provides a map for the improvement of perovskite TFTs. It has been revealed that molecular orientations of the emitters in OLEDs with the transition dipole moment lying in plane enhances light outcoupling efficiency. Multiple experimental techniques are needed to provide complementary orientation information and their physical origin. Here, we propose using TFT to probe the orientation of the phosphorescent emitters. Homoleptic fac-Ir(ppy)3 and heteroleptic trans-Ir(ppy)2(acac) and trans-Ir(ppy)2(tmd) were deposited on polystyrene (PS) and SiO2 substrates. Compared to the PS surface inducing isotropic orientation as the control, trans-Ir(ppy)2(acac) and trans-Ir(ppy)2(tmd) possessed decreased carrier mobilities on SiO2. With the study of initial film growth, we infer that preferred orientation induced by the polar SiO2 surface led to an increase in energetic disorder in the well-stacked trans-Ir(ppy)2(acac) and hopping distance in the amorphous trans-Ir(ppy)2(tmd). The highly symmetric fac-Ir(ppy)3 remained its isotropic orientation despite the dipolar interaction. Surprisingly, the TFT technique gives much higher sensitivity to surface-induced orientation, and thus may potentially serve as a unique electrical probe for molecular orientation.
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Ho, Ka Wai. "Evaluation and characterization of efficient organic optoelectronic materials and devices." HKBU Institutional Repository, 2020. https://repository.hkbu.edu.hk/etd_oa/873.
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With the progression towards lighter but larger-display self-sustainable mobile devices, device efficiency becomes increasingly important, owing to the higher power display consumption but at the same time more limitation on the size and volume of energy storage. In this thesis, selected aspects regarding to efficiency of three types of optoelectronic devices, indoor photovoltaics (IPVs), perovskite thin-film transistors (TFTs) and organic light-emitting diodes (OLEDs) have been investigated. IPVs can make off-grid devices self-sustainable by harvesting ambient light energy. Its weak irradiance necessitates high-efficiency IPVs to generate sufficient power. Our work addresses the need of knowing the limit of the device parameters for correct evaluation and understanding the efficiency loss for developing clinical tactics. We delivered a general scheme for evaluating the limiting efficiency and the corresponding device parameters of IPVs under various lights, illuminance and material bandgap. In contrast to the AM1.5G conditions, a maximum power conversion efficiency (PCE) of 51-57 % can be achieved under the optimal bandgap of 1.82-1.96 eV. We also propose using the second thickness peak of interference instead of the first as a better optimal absorber thickness after identifying the finite absorption as the major source of efficiency loss. The work provides insights for device evaluation and material design for efficient IPV devices. The novel hybrid organic-inorganic perovskites have gained enormous research interest for its various excellent optoelectronic properties such as high mobility. TFT as an alternative application to the majorly focused photovoltaics is realized in this work. There are few reports on perovskite TFTs due to wetting issues. By employing polymethacrylates with ester groups and aromatic substituents which provide polar and cation-π interactions with the Pb2+ ions, quality films could be fabricated with large crystals and high electron mobility in TFTs. We further improved the performance by resolving interfacial mixing between the perovskite and the polymer using the crosslinkable SU-8, achieving the highest mobility of 1.05 cm2 V−1 s−1. Subsequently, we cured the grain boundaries using methylamine solvent vapor annealing, suppressing the TFT subthreshold swing. The work provides a map for the improvement of perovskite TFTs. It has been revealed that molecular orientations of the emitters in OLEDs with the transition dipole moment lying in plane enhances light outcoupling efficiency. Multiple experimental techniques are needed to provide complementary orientation information and their physical origin. Here, we propose using TFT to probe the orientation of the phosphorescent emitters. Homoleptic fac-Ir(ppy)3 and heteroleptic trans-Ir(ppy)2(acac) and trans-Ir(ppy)2(tmd) were deposited on polystyrene (PS) and SiO2 substrates. Compared to the PS surface inducing isotropic orientation as the control, trans-Ir(ppy)2(acac) and trans-Ir(ppy)2(tmd) possessed decreased carrier mobilities on SiO2. With the study of initial film growth, we infer that preferred orientation induced by the polar SiO2 surface led to an increase in energetic disorder in the well-stacked trans-Ir(ppy)2(acac) and hopping distance in the amorphous trans-Ir(ppy)2(tmd). The highly symmetric fac-Ir(ppy)3 remained its isotropic orientation despite the dipolar interaction. Surprisingly, the TFT technique gives much higher sensitivity to surface-induced orientation, and thus may potentially serve as a unique electrical probe for molecular orientation.
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Eicker, Ursula Irmgard. "Optical studies of amorphous silicon alloys for optoelectronic and photovoltaic devices." Thesis, Heriot-Watt University, 1989. http://hdl.handle.net/10399/1036.
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BRUNI, FRANCESCO. "NOVEL MATERIAL DESIGN AND MANIPULATION STRATEGIES FOR ADVANCED OPTOELECTRONIC APPLICATIONS." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2017. http://hdl.handle.net/10281/151660.
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Il mio progetto di dottorato è stato focalizzato sui semiconduttori organici per applicazioni fotovoltaiche e di fotorivelazione. Inizialmente ho lavorato sul controllo morfologico di blende binarie di molecole organiche e fullereni usando la cosiddetta strategia dei pigmenti latenti. In particolare ho lavorato sull'ingenierizzazione dello strato attivo di celle solari organiche a eterogiunzione. Ho dimostrato una nuova strategia per controllare la segregazione di fase in film sottili di molecole elettron donatrici e fullereni, introducendo nel sistema un network di legami di idrogeno attivato termicamente. Successivamente ho studiato i processi di accumulazione di carica all’interfaccia tra acqua e un semiconduttore polimerico per applicazioni biomediche per mezzo di nanocristalli colloidali biemissivi con alta sensibilità verso agenti elettronattrattori. In fine, ho dedicato l’ultima parte del mio lavoro all’approfondimento delle possibili applicazioni di questa classe di nanocristalli come sensori raziometrici di pH intracellulare e come vernici per il monitoraggio ottico della pressione.My PhD has been focused on organic semiconductors for photovoltaics and photodetecting applications. Initially, I worked on the control of the morphology in binary blends of small organic molecules and fullerenes using the so called latent pigment approach. Subsequently, I investigated the charge accumulation and polarization effect occurring at the interface between water and a polymeric semiconductor used as optical component in retinal prosthesis by means of inorganic colloidal nanocrystals featuring a ratiometric sensing ability for electron withdrawing agents. As a last part of the work, I focalized on the applications of these nanocrystals as ratiometric sensors for intracellular pH probing and pressure optical monitoring. Specifically, during the first part of my PhD, I worked in the field of organic photovoltaics on the morphology engineering of the active layer of small molecules bulk-heterojunction solar cells. I demonstrated a new strategy to fine tune the phase-segregation in thin films of a suitably functionalized electron donor blended with fullerene derivatives by introducing in the system a post-deposition thermally activated network of hydrogen bonds that leads to improved stability and high crystallinity. Moreover, this process increases the carrier mobility of the donor species and allows for controlling the size of segregated domains resulting in an improved efficiency of the photovoltaic devices. This work revealed the great potential of the latent hydrogen bonding strategy that I subsequently exploited to fabricate nanometric semiconductive features on the film surface by using a very simple maskless lithographic technique. To do so, I focalized a UV laser into a confocal microscope and used the objective as a “brush” to thermically induce a localized hydrogen bonding driven crystallization with diffraction limited resolution. My work on organic semiconductors continued with a study on the surface polarization driven charge separation at the P3HT/water interfaces in optoelectronic devices for biologic applications. In this work, I probed the local accumulation of positive charges on the P3HT surface in aqueous environment by exploiting the ratiometric sensing capabilities of particular engineered core/shell heterostuctures called dot-in-bulk nanocrystals (DiB-NCs). These structures feature two-colour emission due to the simultaneous recombination of their core and shell localized excitons. Importantly, the two emissions are differently affected by the external chemical environment, making DiB-NCs ideal optical ratiometric sensors. In the second part of my PhD, I, therefore, focalized on the single particle sensing application of DiB-NCs. Specifically, I used them to ratiometrically probe intracellular pH in living cells. With this aim, I studied their ratiometric response in solution by titration with an acid and a base. Subsequently, I internalized them into living human embryonic kidney (HEK) cells and monitored an externally induced alteration of the intracellular pH. Importantly, viability test on DiB-NCs revealed no cytotoxicity demonstrating their great potential as ratiometric pH probes for biologic application. Finally, I used DiB-NCs as a proof-of-concept single particle ratiometric pressure sensitive paint (r-PSP). In this application, the emission ratio between the core and the shell emission is used to determine the oxygen partial pressure and therefore the atmospheric pressure of the NC environment.
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Shi, Tingting. "Optoelectronic and Defect Properties in Earth Abundant Photovoltaic Materials: First-principle Calculations." University of Toledo / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1418391935.
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Sola, Margherita. "Optoelectronic properties of LaVO3 perovskite for photovoltaic applications investigated by surface potential measurements." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/10716/.
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La ricerca su materiali innovativi per applicazioni fotovoltaiche si è orientata negli ultimi anni verso lo studio delle perovskiti, per lo sviluppo di nuove tipologie di celle solari ad alta efficienza e basso costo; tuttavia, la commercializzazione di tali celle solari è ancora lontana, a causa della loro grande instabilità. L’ossido di lantanio-vanadio (LaVO3), che presenta la struttura cristallina della perovskite, è un materiale molto promettente per applicazioni fotovoltaiche, in quanto potrebbe risolvere il problema della stabilità.
Gli obiettivi della tesi sono stati: lo studio delle proprietà ottiche ed elettriche del LaVO3; l’implementazione e l’ottimizzazione di un apparato sperimentale di surface photovoltage spectroscopy (SPS), insieme con lo sviluppo del relativo software di acquisizione dati.
L’apparato per SPS è stato implementato con successo, il set-up sperimentale è stato ottimizzato ed è stato sviluppato un software per l’acquisizione dati.
Lo studio delle proprietà morfologiche del LaVO3 alla nanoscala, condotto mediante microscopia a forza atomica, ha permesso l’identificazione delle condizioni di deposizione ottimali dei film sottili. Lo studio delle proprietà elettriche, condotto mediante scanning Kelvin probe microscopy, ha permesso la determinazione del valore dell’altezza barriera all’interfaccia LaVO3/ZnO e delle work function di ZnO e LaVO3.
Si noti che il valore di work function del LaVO3 non era mai stato riportato prima in letteratura. Le misure SPV sul LaVO3 hanno generato un segnale minore del limite di rilevazione dell’apparato: ciò significa che le coppie elettrone-lacuna fotogenerate non vengono separate e raccolte in modo efficiente. In conclusione, il LaVO3 è noto per avere proprietà ottiche ottimali ed elevata stabilità, che sono vantaggi considerevoli per eventuali dispositivi fotovoltaici. Tuttavia, le misure di SPV hanno chiaramente dimostrato che questo materiale non è ottimale come mezzo per il trasporto di carica.
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Han, Lu. "Light Management in Photovoltaic Devices and Nanostructure Engineering in Nitride-based Optoelectronic Devices." Case Western Reserve University School of Graduate Studies / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=case1486996393294605.
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Grand, Caroline. "Controlling electronic properties and morphology of isoindigo-based polymers for photovoltaic applications." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/54856.
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Novel organic conjugated materials have led to new technologies in the field of flexible electronics, with applications in the area of sensors, field effect transistors, or photovoltaic devices. Several material parameters and properties come into play in these devices, including energy of the frontier molecular orbitals, thin film morphology, and charge transport. These properties can be controlled by the chemistry of organic materials, and through processing conditions. In particular, this dissertation focuses on the isoindigo unit as an electron deficient unit to tune polymer light absorption, charge separation, charge transport in the first part of this dissertation, and morphology control in organic photovoltaic (OPV) devices in a subsequent section. The first part of this dissertation introduces the synthesis and properties of isoindigo-containing polymers as n-type, p-type, or ambipolar semiconductors, and their application in all-polymer or polymer:fullerene blends OPV active layers. It is found that polymers with phenyl linkages along the backbone tend to have broader light absorption than polymers with alternating phenyl-thiophene rings; however, steric hindrance in the former leads to low charge mobilities, and poor device performance. In addition, this section highlights the importance of controlling phase separation in OPV devices by focusing on all-polymer blends, which show large phase separation, and polymer:fullerene blends, where the morphology can be controlled through processing additives generating a two-fold increase in device efficiency. Looking at poly(oligothiophene-isoindigo) polymers as model systems, emphasis is placed on photovoltage losses in these devices due to a decrease in effective energy gap between the polymers and fullerene as the oligothiophene donating strength is increased, as well as explanation of the device parameters through description of morphology as solubility is varied.
The second portion of this dissertation focuses on solution properties of polymers and their correlation to thin film morphology. A first study investigates the influence of alkyl side chains on solubility, molecular packing, and phase separation in blends of poly(terthiophene-alt-isoindigo) with fullerenes. Specifically, as side chains are lengthened, solubility is increased, but with limited impact on the blends morphology. On the other hand increased backbone torsion leads to variations in energy levels, polymer packing and large phase separation in blends with fullerenes. These thermodynamic parameters are to put in perspective with the kinetic control of film formation during the coating process. This is discussed in a second study, which looks at the mechanism of thin film formation when processing additives are used. In particular, this study highlights the interactions that provide a driving force for polymer crystallite formation, depending on the mechanism followed when aliphatic and aromatic additives are used. These observations are then used to predict the morphology in spin-coated thin films.
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Kinder, Erich W. "Fabrication of All-Inorganic Optoelectronic Devices Using Matrix Encapsulation of Nanocrystal Arrays." Bowling Green State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1339719904.
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Rodière, Jean. "Optoelectronic characterization of hot carriers solar cells absorbers." Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066703/document.
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La cellule photovoltaïque à porteurs chauds est un dispositif de conversion de l’énergie solaire en énergie électrique dont les rendements théoriques approchent les 86%. Additionnellement à une cellule photovoltaïque standard, ce dispositif permet de convertir l’excédent d’énergie cinétique des porteurs photogénérés, en énergie électrique. Pour cela, le phénomène de thermalisation doit être réduit et des contacts électriques sélectifs en énergie ajoutés. Afin de déterminer les performances potentielles des absorbeurs, tout en surmontant le défi de fabrication des contacts électriques sélectifs, un montage et une méthode de cartographie d’intensité absolue de photoluminescence résolue spectralement ont été utilisés. Ceci a permis d’obtenir la température d’émission et la séparation des quasi-niveaux de Fermi, les deux grandeurs thermodynamiques caractéristiques de la performance des absorbeurs. Dans cette étude, des absorbeurs à base de puits quantiques d’InGaAsP sur substrat d’InP sont utilisés. Les grandeurs thermodynamiques sont estimées et la technique de caractérisation utilisée permet l’accès à des grandeurs tel que le facteur de thermalisation mais aussi un coefficient thermoélectrique, appelé photo-Seebeck. L’analyse quantitative de porteurs chauds dans des conditions pertinentes pour le photovoltaïque est une première ; le dispositif étudié permettrait de dépasser la limite de Schockley-Queisser. Enfin, le dispositif étant muni de contacts des caractérisations électriques sont faites et comparé aux mesures optiques. Afin de mieux comprendre l’évolution des grandeurs thermodynamiques étudiées, une première simulation est proposéeThe hot carrier solar cell is an energy conversion device where theoretical conversion efficiencies reach almost 86%. Additionally to a standard photovoltaic cell, the device allows the conversion of kinetic energy excess of photogenerated carriers into electrical energy. To achieve this, the thermalisation process must be limited and electrical energy selective contacts added. In order to determine potential absorber performances and overcome the fabrication challenge of energy selective contacts, a set-up and the related method of mapping absolute photoluminescence spectra were used. This technique allows getting quasi-Fermi levels splitting and temperature of emission, both thermodynamic quantities characteristic of the performance of the absorbers. In this study, absorbers based on InGaAsP multiquantum wells on InP substrate were used. The thermodynamic quantities are determined and allow to access at quantities such as thermalisation rate but also a thermoelectric coefficient, so-called Photo-Seebeck. The quantitative analysis of the hot carriers regime, in relevant conditions for photovoltaic is a first: the analysed device indicates a potential photovoltaic conversion over the Schockley-Queisser limit. At last, as the device is supplied with electrical contacts, electrical characterization are made and compared to optical measurements. A first simulation is proposed to better understand the thermodynamic quantities evolution as a function of the electrical bias
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Kaya, Emine. "Solution Processable Benzotriazole And Fluorene Containing Copolymers For Photovoltaic Applications." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613561/index.pdf.
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2-Dodecyl benzotriazole and 9,9-dioctylfluorene containing alternating copolymers poly((9,9-dioctylfluorene)-2,7-diyl-(2-dodecyl-benzo[1,2,3]triazole)) (P1), poly((9,9-dioc-tylfluorene)-2,7-diyl-(4,7-bis(thien-2-yl) 2-dodecyl benzo[1,2,3]triazole)) (P2), poly((9,9 dioctylfluorene)-2,7-diyl-(4,7-bis(3-hexylthien-5-yl) 2-dodecyl-benzo[1,2,3]triazole)) (P3) were synthesized via Suzuki polycondensation. Synthesized monomers and copolymers were characterized by Nuclear Magnetic Resonance (1H-NMR, 13C-NMR). Optical and electronic properties of resulting alternating copolymers were investigated by means of Cyclic Voltammetry (CV), Ultraviolet&ndashVisible Spectroscopy and spectroelectrochemistry. All three polymers showed both p and n doping behaviors and multicolored electrochromic states. In order to learn switchingtimes and percent transmittance changes kinetic studies were also performed. Thermal properties of the polymers were investigated via Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). Due to the convenient HOMO and LUMO levels, band gaps, strong absorptions in the visible region and thermal stability, polymers were tested in Organic Solar Cell (OSC) device applications. The preliminary investigation indicated that polymers had promising power conversion efficiencies.
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Khan, Ridita Rahman. "Modeling, Simulation and Characterization of Optoelectronic Properties of 2D-3D CoO-ATO Nano Structures." Scholar Commons, 2017. https://scholarcommons.usf.edu/etd/7414.
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Devices for converting solar energy to electrical energy are not considerably efficient, though there are abundant renewable solar energy sources. Therefore there is a continuous call for investigation of new devices that are efficient and eco-friendly thereby contributing to harvested energy technology.
This thesis characterizes the optical constant (refractive index) of a novel material, cobalt oxide-antimony doped tin oxide (CoO-ATO). Thin film of CoO-ATO is generated using spin coating of CoO-ATO solution having 76.33% chloroform, 13.47% polystyrene, 10% antimony doped tin oxide and 0.2% cobalt oxide by weight. The thin film is analyzed through ellipsometry to acquire the refractive index of the material through the visible spectrum, which is used for modeling an antireflective coating in a solar cell. The model is designed and analyzed by simulation using computer simulated technology, and the results of the analysis of a thin film or a nanofiber membrane of the novel material implemented as an antireflective coating layer that affects the absorption efficiency of the optoelectronic device.
The result of the analysis showed enhancement of absorption efficiency within the visible spectrum for both thin film and nanofiber membrane of the novel material CoO-ATO. The absorption through thin film was more than that of the nanofiber membrane.
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Manda, Venkata Ramana. "Enhancing the Photovoltaic Performance of P3HT/PDIB Silsesquioxane Donor-Acceptor System Using Spray Deposition Fabrication Technique." TopSCHOLAR®, 2014. http://digitalcommons.wku.edu/theses/1336.
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In the past few years, the solution-processed organic based solar cells gained more importance by meeting the demands for cost effective photovoltaic devices. To date, the focus of the organic photovoltaic devices has been on the optimization of the processing the materials to improve photo conversion efficiency and also by modifying the active components of the organic materials. Recently, it has been recognized that the deposition techniques also plays a major role in enhancing the power conversion efficiencies. Currently, though the most common deposition technique for organic solar cells is spin coating, which does not allow scaling up of the large device area. As an alternative method, a simple airbrush spray deposition technique has been developed to fabricate the test devices. The film thickness of the layers was characterized under scanning electron microscope. Devices with different thickness (1000 nm, 500 nm, 240 nm) of poly(3,4-ethylenedioxythipohene) polystyrene sulfonate (PEDOT.PSS) and active layers are prepared and their photovoltaic performances have been evaluated and compared by plotting the IV curves with respect to each thickness. Maintaining the distance between the substrate and the airbrush nozzle the thickness of the layers was controlled. From the results, we found that the test devices with 500 nm thickness of PEDOT.PSS and active layers shows the best device performance with highest current density of 3.97 mA/cm2, open circuit voltage of 1.3 V and power conversion efficiency of 2.34%. As a control experiment, devices were also developed using the standard poly(3- hexylthiophene-2,5-diyl):phenyl-C61-butyric acid methyl ester (P3HT:PCBM) system, but the power conversion efficiencies of these devices were not promising with respect to the literature results. Future studies of this project will focus on improving the power conversion efficiency of poly(3-hexylthiophene-2,5-diyl)/perylenediimide bridged system (P3HT/PDIB) by developing a new device architecture called “tandem solar cells” which consists of multiple layers of different donor and acceptor blends with inorganic transition metal oxides such as zinc oxide and molybdenum oxides.
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Wilkins, Matthew M. "Design of Multi-junction Solar Cells on Silicon Substrates Using a Porous Silicon Compliant Membrane." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/24096.
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A novel approach to the design of multi-junction solar cells on silicon substrates for 1-sun applications is described. Models for device simulation including porous silicon layers are presented. A silicon bottom subcell is formed by diffusion of dopants into a silicon wafer. The top of the wafer is porosified to create a compliant layer, and a III-V buffer layer is then grown epitaxially, followed by middle and top subcells. Due to the resistivity of the porous material, these designs are best suited to high efficiency 1-sun applications. Numerical simulations of a multi-junction solar cell incorporating a porous silicon compliant membrane indicate an efficiency of 30.7% under AM1.5G, 1-sun for low threading dislocation densities (TDD), decreasing to 23.7% for a TDD of 10^7 cm^-2.
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Beal, Russell Joseph. "Effects of Nanoassembly on the Optoelectronic Properties of CdTe - ZnO Nanocomposite Thin Films for Use in Photovoltaic Devices." Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/283601.
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Quantum-scale semiconductors embedded in an electrically-active matrix have the potential to improve photovoltaic (PV) device power conversion efficiencies by allowing the solar spectral absorption and photocarrier transport properties to be tuned through the control of short and long range structure. In the present work, the effects of phase assembly on quantum confinement effects and carrier transport were investigated in CdTe - ZnO nanocomposite thin films for use as a spectrally sensitized n-type heterojunction element. The nanocomposites were deposited via a dual-source, sequential radio-frequency (RF) sputter technique that offers the unique opportunity for in-situ control of the CdTe phase spatial distribution within the ZnO matrix. The manipulation of the spatial distribution of the CdTe nanophase allowed for variation in the electromagnetic coupling interactions between semiconductor domains and accompanying changes in the effective carrier confinement volume and associated spectral absorption properties. Deposition conditions favoring CdTe connectivity had a red shift in absorption energy onset in comparison to phase assemblies with a more isolated CdTe phase. While manipulating the absorption properties is of significant interest, the electronic behavior of the nanocomposite must also be considered. The continuity of both the matrix and the CdTe influenced the mobility pathways for carriers generated within their respective phases. Photoconductivity of the nanocomposite, dependent upon the combined influences of nanostructure-mediated optical absorption and carrier transport path, increased with an increased semiconductor nanoparticle number density along the applied field direction. Mobility of the carriers in the nanocomposite was further mediated by the interface between the ZnO and CdTe nanophases which acts as a source of carrier scattering centers. These effects were influenced by low temperature annealing of the nanocomposite which served to increase the crystallinity of the phases without modification of the as-deposited phase assembly and associated absorption properties. Integration of the nanocomposite as an n-type heterojunction element into a PV device demonstrated the ability to tune device response based on the spectral absorption of the nanocomposite sensitizer film as dictated by the phase assembly. Overall the various phase assemblies studied provided increased opportunity for optimization of the absorption and carrier transport properties of the nanocomposite thin films.
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Shrestha, Niraj. "Optoelectronic Properties of CdSexTe1-x, CuInSe2 and Perovskites for Photovoltaic Applications." University of Toledo / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=toledo159680306858192.
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Brombosz, Scott M. "Alkynylated acenothiadiazoles and N-heteroacenes: synthesis, functionalization, and study of the optical properties for optoelectronic and sensory materials." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37102.
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For organic electronic device applications materials are needed which display good charge carrier mobility, good processability, and stability towards oxygen and moisture. Alkynylated N-Heteroacenes fulfill many of these requirements. Substitution with alkyne groups as well as the introduction of the pyrazine subunit both inhibits oxidative degradation at sensitive position in the molecules. Additionally the trialkylsilylethynyl group aides in directing the packing motif as well as vastly increases the solubility over unsubstituted analogues.
A requisite precursor in the synthesis of alkynylated N-heteroacenes is alkynylated acenothiadiazoles. These thiadiazoles display interesting photophysical properties and can be functionalized to produce a wide range of properties in closely related materials. The acenothiadiazoles themselves have potential applications as an N-type semiconductor. Optical gaps and calculated HOMO-LUMO gaps show that these molecules, when compared to known N-type materials, should be easily injected with electrons. Additionally the crystal packing of these compounds shows favorable π-orbital overlap which should provide excellent charge carrier mobilities.
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Jošt, Marko [Verfasser], Marko [Akademischer Betreuer] Topič, Bernd [Gutachter] Rech, Bernd [Gutachter] Szyszka, Marko [Gutachter] Topič, and Janez [Gutachter] Trontelj. "Fabrication and characterization of nanotextures for light management in photovoltaic and optoelectronic devices / Marko Jošt ; Gutachter: Bernd Rech, Bernd Szyszka, Marko Topič, Janez Trontelj ; Betreuer: Marko Topič." Berlin : Technische Universität Berlin, 2017. http://d-nb.info/1156180805/34.
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Jošt, Marko Verfasser], Marko [Akademischer Betreuer] Topič, Bernd [Gutachter] [Rech, Bernd [Gutachter] Szyszka, Marko [Gutachter] Topič, and Janez [Gutachter] Trontelj. "Fabrication and characterization of nanotextures for light management in photovoltaic and optoelectronic devices / Marko Jošt ; Gutachter: Bernd Rech, Bernd Szyszka, Marko Topič, Janez Trontelj ; Betreuer: Marko Topič." Berlin : Technische Universität Berlin, 2017. http://nbn-resolving.de/urn:nbn:de:101:1-201804162945.
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Eder, Grace M. "Dye Molecule-Based Porous Organic Materials." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1530012900215452.
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Shaw, Nicola Jane. "Studies of dye sensitised photovoltaic cells." Thesis, University of Bath, 1999. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301538.
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Abdi, Jalebi Mojtaba. "Chemical modifications and passivation approaches in metal halide perovskite solar cells." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/283216.
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This dissertation describes our study on different physical properties of passivated and chemically modified hybrid metal halide perovskite materials and development of highly efficient charge transport layers for perovskite solar cells. We first developed an efficient electron transport layer via modification of titanium dioxide nanostructure followed by a unique chemical treatment in order to have clean interface with fast electron injection form the absorber layer in the perovskite solar cells. We then explored monovalent cation doping of lead halide perovskites using sodium, copper and silver with similar ionic radii to lead to enhance structural and optoelectronic properties leading to higher photovoltaic performance of the resulting perovskite solar cells. We also performed thorough experimental characterizations together with modeling to further understand the chemical distribution and local structure of perovskite films upon monovalent cation doping. Then, we demonstrate a novel passivation approach in alloyed perovskite films to inhibit the ion segregation and parasitic non-radiative losses, which are key barriers against the continuous bandgap tunability and potential for high-performance of metal halide perovskites in device applications, by decorating the surfaces and grain boundaries with potassium halides. This leads to luminescence quantum yields approaching unity while maintaining high charge mobilities along with the inhibition of transient photo-induced ion migration processes even in mixed halide perovskites that otherwise show bandgap instabilities. We demonstrate a wide range of bandgaps stabilized against photo-induced ion migration, leading to solar cell power conversion efficiencies of 21.6% for a 1.56 eV absorber and 18.3% for a 1.78 eV absorber ideally suited for tandem solar cells. We then systematically compare the optoelectronic properties and moisture stability of the two developed passivation routes for alloyed perovskites with rubidium and potassium where the latter passivation route showed higher stability and loading capacity leading to achieve substantially higher photoluminescence quantum yield. Finally, we explored the possibility of singlet exciton fission between low bandgap perovskites and tetracene as the triplet sensitizer finding no significant energy transfer between the two. We then used tetracene as an efficient dopant-free hole transport layer providing clean interfaces with perovskite layer leading to high photoluminescence yield (e.g. ~18%). To enhance the poor ohmic contact between tetracene and the metal electrode, we added capping layer of a second hole transport layer which is extrinsically doped leading to 21.5% power conversion efficiency for the subsequent solar cells and stabilised power output over 550 hours continuous illumination.
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GRASSI, FABIO. "Ab Initio Modelling of Semiconductor Nanoparticles for Optoelectronics and Photovoltaics." Doctoral thesis, Università del Piemonte Orientale, 2014. http://hdl.handle.net/11579/115648.
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Robertson, Kyle. "Optoelectronic Device Modeling of GaAs Nanowire Solar Cells." Thesis, Université d'Ottawa / University of Ottawa, 2019. http://hdl.handle.net/10393/39710.
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Nanowire solar cells have great potential as candidates for high efficiency, next-generation solar cell devices. To realize their potential, accurate and efficient modeling techniques en- compassing both optical and electrical phenomena must be developed. In this work, a coupled optical and electronic model of GaAs nanowire solar cells was developed, with the goal of building a platform for automated, algorithmic device optimization.
Significant work was done on the optical portion of model, with the goal of reducing run- times and improving the level of automation. Enhancements were made to an open-source implementation of the Rigorous Coupled Wave Analysis method for solving Maxwell’s equations, to make it more accurate for modeling nanowire solar cells. Its accuracy and efficiency were thoroughly investigated, and with the enhancements presented here it was shown to be an effective technique for rapid optical modeling of nanowire devices. Purely optical optimizations of a sample AlInP-passivated GaAs nanowire on a GaAs substrate were performed to demonstrate the efficacy of the technique using a Nelder-Mead simplex optimization of device geometry.
The optical model was then coupled into a finite volume method based electrical model implemented in TCAD Sentaurus, to compute device efficiencies and ultimately optimize electrical device performance. As a first step, an algorithmic optimization of a p-i-n nanowire solar cell consisting of an AlInP-passivated GaAs nanowire on a Si substrate was performed using the generation rates computed by the enhanced RCWA implementation. The overall geometry was fixed to the result of the optical optimization, and only internal electrical parameters were optimized. The results showed that significant performance improvements can be obtained with the right choice of doping levels and doping region configurations, even without optimizing the global device geometry.
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Опанасюк, Анатолій Сергійович, Анатолий Сергеевич Опанасюк, Anatolii Serhiiovych Opanasiuk, Таїсія Олександрівна Бересток, Таисия Александровна Бересток, and Taisiia Oleksandrivna Berestok. "Research laboratory «optoelectronics and solar power engineering»." Thesis, Одеський національний політехнічний університет, 2013. http://essuir.sumdu.edu.ua/handle/123456789/34062.
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The main goal of the research is to create a device structures (solar cells, optical detectors, and hard radiation detector gases) based on heterojunctions and semiconductor-metal structures.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/34062
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ROONEY, MILES. "Self-assembled, nanostructured organic materials for applications in electronics and optoelectronic devices." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2018. http://hdl.handle.net/10281/199099.
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l'indagine di due metodi per il controllo molecolare della nano-morfologia di dispositivi opto-elettronici. In primo luogo, un metodo di fotoreticolazione per la creazione di strati semiconduttori insolubili adatti per dispositivi fotovoltaici organici. Una grande serie di semiconduttori squaraine sono studiati in un dispositivo di eterogiunzione di massa. Questo approccio è esteso a nuclei semiconduttori di dichetopirrolopirrolo e naftalene diimmide. Lo studio dettagliato della struttura del film dei materiali viene effettuato.
Il secondo approccio è un'indagine sull'applicabilità dei pigmenti latenti per l'optoelettronica organica. Una serie di fotovoltaici organici sono prodotti in architetture di eterogiunzione planare a doppio strato. I dispositivi a film sottile sono testati con una varietà di interstrati e parametri di elaborazione. Il controllo della nanostruttura di questi dispositivi a film sottile viene esaminato con studi a raggi X. Incorporazione di riflettività a raggi X, raggi X speculari, raggi X a gradiente e studi a raggi x grandangolari. In questo modo la massa e le interfacce dei dispositivi a film sottile possono essere esaminate e caratterizzate. L'approccio del pigmento latente viene applicato anche al campo dei transistor ad effetto di campo organico come lo strato semiconduttore attivo. La natura resistente ai solventi di un pigmento semiconduttore genitore mostra un vantaggio sostanziale per la fabbricazione di tali dispositivi. L'esclusivo riarrangiamento cristallino che si verifica dopo la deprotezione di un pigmento latente determina un miglioramento della mobilità del portatore di carica fino a tre ordini di grandezza mentre estende le possibilità di elaborazione delle successive fasi di deposizione necessarie per completare un transistor ad effetto di campo organico
Queste due tecniche sono sviluppate pensando alla compatibilità industriale. Come tale, viene esplorato un nuovo metodo sintetico per una produzione facile, economica ed ecocompatibile di semiconduttori organici. Un ambiente di reazione micellare viene creato attraverso l'uso del comune tensioattivo e dell'eccipiente di droga Kolliphor EL. L'esclusivo nucleo privo di ossigeno di questo tensioattivo offre un nuovo ambiente per l'esecuzione di comuni reazioni di accoppiamento incrociato quali reazioni Suzuki-Miyaura, Stille e Heck in aria e acqua a temperatura ambiente. Alte rese di oltre il 90% vengono recuperate per nuclei semiconduttori organici complessi. La versatilità di questo approccio è estesa dall'uso del toluene come co-solvente. Questo sistema di co-solvente porta allo sviluppo di un'emulsione che può essere utilizzata per eseguire analisi chimiche complesse. La chimica dell'emulsione offre un modo unico per la sintesi di semiconduttori organici complessi con basso carico di catalizzatore metallico ad alto rendimento.the investigation of two methods for molecular control of the nano-morphology of opto-electronic devices. Firstly, a photocrosslinking method for creating insoluble semiconductor layers suitable for organic photovoltaic devices. A large series of squaraine based semiconductors are investigated in a bulk heterojunction device. This approach is extended to diketopyrrolopyrrole and naphthalene diimide semiconducting cores. Detailed study of the materials film structure is carried out. The second approach is an investigation of the applicability of latent pigments for organic opto-electronics. A series of organic photovoltaics are produced in planar bilayer and bulk heterojunction architectures. The thin film devices are tested with a variety of interlayers and processing parameters. The control of the nanostructure of these thin film devices is examined with X-ray studies. Incorporating X-ray reflectivity, Specular x-ray, Gradient temperature X-ray and grazing wide angle x-ray studies. In this manner the bulk and interfaces of thin film devices can be examined and characterised. The latent pigment approach is also applied to the field of organic field effect transistors as the active semiconducting layer. The solvent resistant nature of a parent semiconducting pigment shows a substantial benefit to the fabrication of such devices. The unique crystalline rearrangement which occurs upon deprotection of a latent pigment results in an improvement in charge carrier mobility of up to three orders of magnitude while extending the processing possibilities of the subsequent deposition steps required to complete an organic field effect transistor These two techniques are developed with the thoughts of industrial compatibility in mind. As such, a novel synthetic method for facile, cheap, and environmentally friendly production of organic semiconductors is explored. A micellar reaction environment is created through the use of the common surfactant and drug excipient Kolliphor EL. The unique oxygen free core of this surfactant offers a new environment for carrying out common cross coupling reactions such as Suzuki-Miyaura, Stille and Heck reactions in air and water at ambient temperature. High Yields of over 90% are recovered for complex organic semiconducting cores. The versatility of this approach is extended by the use of toluene as a co-solvent. This co-solvent system results in the development of an emulsion which can be used to perform complex chemistries. Emulsion chemistry offers a unique way to synthesis complex organic semiconductors with low metallic catalyst loading at high yield.
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Molet, Bachs Pau. "Managing light in optoelectronic devices with resonant optical nanostructures." Doctoral thesis, Universitat Autònoma de Barcelona, 2021. http://hdl.handle.net/10803/673260.
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Actualment, un dels reptes en l’àmbit de la manipulació de la llum a la nanoescala és la transició del laboratori a aplicacions reals. Tot i el gran potencial demostrat per algunes estructures fotòniques per a incrementar la eficiència de instruments optoelectrònics, la seva implementació de d’aquestes a dispositius de mercat sovint es obstruïda per la necessitat d’usar tècniques de fabricació poc escalables i d’alt cost. Aquesta tesis està dedicada al disseny i implementació de estratègies de manipulació de la llum per a millorar la eficiència en la recol·lecció d’energia de plaques solars i fotodetectors, així com la millora de la emissió en dispositius d’il·luminació, mitjançant mètodes de nanoestructuració escalables com la nano-litografia suau. Aquesta tècnica té la capacitat de produir patrons i estructures amb una resolució de pocs nanòmetres amb gran fidelitat en àrees grans. A més a més, és compatible amb el processament a gran escala mitjançant el sistema de impressió en cadena “roll to roll” (carret-a-carret). També es tracta d’una tecnologia molt versàtil, ja que permet l’ús de diferents tipus de substrats, és poc invasiva i generalment pot ser introduïda en el esquema de fabricació sense haver de modificar cap pas. Amb l’ajuda d’aquesta tècnica de nanofabricació, explorem una varietat de arquitectures fotòniques i les diferents ressonàncies fotòniques que les fan especials. Entre aquestes darreres podem trobar ressonàncies de Mie, modes de Brewster i modes de cristall fotònic, que proveiran al sistema amb una major interacció llum-matèria a la capa activa del dispositiu, podent-ne millorar les seves capacitats òptiques.
Primer, hem desenvolupat una estratègia per aconseguir una absorció optima de banda ample en semiconductors ultra-fins, amb menys de 100 nm de gruix, per a totes les energies per sobre de la seva energia de banda prohibida. La sinèrgia de les fortes ressonàncies d’interferència de capes fines presents i els modes del cristall fotònic de l’estructura (amb un alt índex de refracció) fan que l’estructura assoleixi fins a un 81% d’absorció en una ampli rang de longituds d’ona (de 400 a 1500 nm).
En segon lloc, hem combinat la litografia suau amb la deposició química de vapor (CVD en anglès) per obtenir una matriu de semiesferes de silici sobre de una guia d’ones d’alt índex de refracció. Hem estudiat les ressonàncies de Mie característiques del substrat, com hibriden amb modes quasi-guiats de la guia d’ones i com això afecta al camp proper de la metasuperfície. Hem anat un pas més enllà estudiant la com la modificació dels paràmetres de disseny de l’estructura afecta les ressonàncies esmentades. Finalment, n’hem demostrat una possible aplicació com a substrat per a incrementar la emissió de llum per part de una molècula emissora.
En la tercera part de la tesi, ens hem enfocat en la implementació de estructures de cristall fotònic bidimensional a tres dispositius diferents per a la millora de la seva eficiència. En particular, millorem la eficiència en la recol·lecció de fotons d’infraroig proper en cèl·lules solars de punts quàntics col·loïdals (PbS) i en fotodetectors orgànics (P3HT: PC60BM i PBTTT: PC70BM), i millorem l’emissió de llum de capes de nanofòsfors (nanocristalls de GdVO4:Eu3+). Hem desenvolupat sistemes fotònics adaptats a cada cas i hem fet una caracterització òptica i electrònica de tots els dispositius. La nanoestructuració en forma de cristall fotònic bidimensional proveeix a les capes actives amb propietats de guies d’ona ressonants, millorant les seves propietats de confinament de la llum en les longituds d’ona desitjades, demostrant així la possibilitat d’implementar les arquitectures.Actualmente, uno de los retos en el ámbito de la manipulación de la luz a la nanoescala es la transición del laboratorio a aplicaciones reales. A pesar del gran potencial demostrado por algunas estructuras fotónicas para incrementar la eficiencia de instrumentos optoelectrónicos, su implementación en dispositivos de mercado muchas veces es obstruida por la necesidad de utilizar técnicas de fabricación poco escalables y de alto coste. Esta tesis está dedicada al diseño e implementación de estrategias de manipulación de la luz para mejorar la eficiencia en la recolección de energía de placas solares y fotodetectores, así como la mejora de la emisión en dispositivos de iluminación, mediante métodos de nanoestructuración escalables como la nano-litografía suave. Esta técnica tiene la capacidad de producir patrones y estructures con una resolución de pocos nanómetros con gran fidelidad en áreas grandes. Encima, es compatible con el procesamiento a gran escala mediante el sistema de impresión en cadena “roll-to-roll” (carrete-a-carrete). También se trata de una tecnología muy versátil, puesto que permite el uso de diferentes tipos de sustratos, es poco invasiva y generalmente puede ser introducida en el esquema de fabricación sin tener que modificar ningún paso. Con la ayuda de esta técnica de nanofabricación, exploramos una variedad de arquitecturas fotónicas y las diferentes resonancias fotónicas que las hacen especiales. Entre estas últimas podemos encontrar resonancias de Mie, modos de Brewster y modos de cristal fotónico, que proveerán al sistema con una mayor interacción luz-materia a la capa activa del dispositivo, mejorar sus capacidades ópticas. Primero, hemos desarrollado una estrategia para conseguir una absorción óptima de banda ancha en semiconductores ultra-finos, con menos de 100 nm de grosor, para todas las energías por encima de su energía de banda prohibida. La sinergia de las fuertes resonancias de interferencia de capas finas presentes y los modos del cristal fotónico de la estructura (con un alto índice de refracción) hacen que la estructura logre hasta un 81% de absorción en un amplio rango de longitudes de omda (de 400 a 1500 nm). En segundo lugar, hemos combinado la litografía suave con la deposición química de vapor (CVD en inglés) para obtener una matriz de semiesferas de silicio sobre de una guía de ondas de alto índice de refracción. Hemos estudiado las resonancias de Mie características del sustrato, como hibridan con modos casi-guiados de la guía de olas y como esto afecta en el campo próximo de la metasuperfície. Hemos ido un paso más allá estudiando como la modificación de los parámetros del diseño de la estructura afecta a las resonancias mencionadas. Finalmente, hemos demostrado una posible aplicación como sustrato para incrementar la emisión de luz por parte de una molécula emisora. En la tercera parte de la tesis, nos hemos enfocado en la implementación de estructuras de cristal fotónico bidimensional a tres dispositivos diferentes para la mejora de su eficiencia. En particular, mejoramos la eficiencia en la recolección de fotones de infrarrojo próximo en células solares de puntos cuánticos coloidales (PbS) y en fotodetectores orgánicos (P3HT: PC60BM y PBTTT: PC70BM), y mejoramos la emisión de luz de capas de nanofósforos (nanocristales de GdVO4:Eu3+). Hemos desarrollado sistemas fotónicos adaptados a cada caso y hemos hecho una caracterización óptica y electrónica de todos los dispositivos. La nanoestructuración en forma de cristal fotónico bidimensional provee a las capas activas con propiedades de guías de onda resonantes, mejorando sus propiedades de confinamiento de la luz en las longitudes de onda deseadas, demostrando así la posibilidad de implementar las arquitecturas.
Currently, one of the main challenges in light management at the nanoscale is the transition from the laboratory to real applications. Despite the great potential shown by photonic architectures to optically improve the performance of many devices, transitioning into marketable devices is often hampered by the low-throughput and expensive nanofabrication techniques involved. This thesis is devoted to the design and development of subwavelength light managing strategies to improve the light harvesting or out-coupling in solar cells, photodetectors and light emitters while using a scalable nanostructuration such as soft nanoimprint lithography (NIL). This technique has been proven to achieve resolutions down to few tens of nanometers with high fidelity in large areas, being compatible with roll to roll processing. It is also versatile regarding the materials where it can be used, non-invasive, and can be seamlessly introduced in the devices fabrication scheme. With the aid of this technique, we explore a variety of photonic architectures and the different types of resonances sustained, from Brewster modes to Mie resonances, in order to enhance the light-matter interaction with the active layer of the device. First, we develop a strategy to achieve broadband optimal absorption in ultra-thin semiconductor materials (less than 100 nm thick) for all energies above their bandgap. The interplay of strong interference thin film resonances and photonic crystal modes sustained by a high refractive index nanostructure on a gold film renders the system with a 81% total absorption over a broad spectral range (from 400 to 1500 nm). Second, we combine soft NIL and chemical vapor deposition to obtain an array of silicon hemispheres on top of a high refractive index dielectric waveguide. We study the Mie resonances supported by the substrate, how these hybridize with the guided modes of the waveguide and how their interaction influences the electromagnetic near field of the metasurface. We further explore the tunability of such resonances with the design parameters of the structure and we demonstrate a potential application of it as a substrate for enhanced photoluminescence. In the third part of the thesis, we focus on the implementation of 2D photonic structures within the active layer of three different devices to improve performance. In particular we enhance the near infrared (NIR) photon harvesting efficiency in a colloidal quantum dot solar cell (PbS-CQD) and in organic photodetectors (P3HT: PC60BM and PBTTT: PC70BM) and improve the light out coupling from a nanophosphor layer (GdVO4:Eu3+ nanocrystals). We developed photonic systems tailored for each device and provide the complete optical and electronic characterization for each case. The nanostructuration with a 2D periodic arrangement renders the active layers with resonant waveguide properties enhancing its light trapping properties in the targeted spectral ranges, hence demonstrating the possibility to implement photonic schemes within actual devices.
Universitat Autònoma de Barcelona. Programa de Doctorat en Ciència de Materials
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Sammito, Davide. "Integration of plasmonic gratings into optoelectronic devices." Doctoral thesis, Università degli studi di Trieste, 2013. http://hdl.handle.net/10077/8578.
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2011/2012ABSTRACT This thesis deals with the control of light absorption in semiconductor devices by the plasmonic resonances of periodically arranged metallic nanostructures integrated on them. Metallic gratings support propagating (SPP) and localized (LSP) plasmonic excitations and surface plasmons-related phenomena, like Extraordinary Optical Transmission (EOT) and plasmonic band gaps, as well as conventional diffraction effects. We combine all the optical resonances outlined to tune the incoupling and distribution of incident photons in the absorbing semiconductor substrate. In particular we consider the application of these concepts to two typologies of optoelectronic devices: photovoltaic solar cells and phototransistors. In the case of photovoltaic devices the objective is to increase the energy conversion efficiency by enhancing light harvesting and re-shaping the absorption profile, in order to improve the collection of photo-generated charge carriers. We begin analyzing a case study, a one-dimensional lamellar grating placed on a silicon substrate, by numerical optical simulations. The aim is to find the coupling conditions of the resonances supported, by designing the geometric parameters of the nanostructures, and showing their impact on the generation profile. These findings are then applied for light trapping purpose to two realistic solar cell layouts. SPP and LSP resonances are able to provide high near field magnification and effectively enhance the absorption of ultrathin organic solar cells. On the other hand, EOT coupled to diffraction orders are more suited to wafer-based Si cells. Then we present the fabrication process developed to realize the designed nanostructures over the large surface area of Si photovoltaic devices. By experiments and simulation we show that an improvement of Internal Quantum Efficiency can be obtained compared to unpatterned devices. Concerning the phototransistors, the aim is use them as compact and scalable biosensors by integrating a plasmonic crystal on the active area. By simulations the grating is designed to maximize transmittance variation due the plasmon resonance shift related to the surface binding of bio-analyte molecules. This event is transduced into an electrical signal at device terminals, as confirmed by characterizations on the first prototypes fabricated. The metallic grating simultaneously works as plasmonic structure and as electronic gate of the transistor in a fully integrated architecture.
SOMMARIO In questa tesi viene trattata la tematica del controllo dell’assorbimento di luce in dispositivi a semiconduttore tramite le risonanze plasmoniche proprie di nanostrutture metalliche integrate con disposizione periodica. Reticoli metallici supportano eccitazioni plasmoniche propaganti (SPP) e localizzate (LSP) e fenomeni correlati ai plasmoni di superficie, quali la trasmissione ottica straordinaria (EOT) e la creazione band gap plasmoniche, così come effetti di diffrazione convenzionali. Tali risonanze ottiche sono state combinate per regolare l’accoppiamento e la distribuzione dei fotoni incidenti in substrati semiconduttori assorbenti. In particolare consideriamo l’applicazione di tali concetti a due tipologie di dispositivi optoelettronici: celle solari fotovoltaiche e foto-transistor. Nel caso dei dispositivi fotovoltaici, l’obiettivo è aumentare l’efficienza di conversione energetica tramite una maggiore raccolta di luce e la redistribuzione del profilo di assorbimento, in modo da migliorare la raccolta dei portatori di carica fotogenerati. L’analisi di un caso di studio, un reticolo lamellare monodimensionale posto su un substrato di silicio, tramite simulazioni ottiche per via numerica, serve a trovare le condizioni di accoppiamento delle risonanze supportate, dimensionando i parametri geometrici delle nanostrutture, e mostrare il loro impatto sul profilo di generazione. Questi risultati sono quindi applicati, per finalità di “light trapping”, a due strutture realistiche di celle solari. Le risonanze SPP e LSP sono capaci di fornire una grande intensificazione del campo vicino e aumentano efficacemente l’assorbimento di celle solari organiche ultra-sottili. D’altro canto, la combinazione di EOT e ordini di diffrazione è più adatta per celle solari spesse in Si. Quindi presentiamo il processo di fabbricazione sviluppato per realizzare le nanostrutture progettate sulle ampie superfici dei dispositivi fotovoltaici in Si. Esperimenti e simulazioni mostrano che è possibile ottenere un aumento dell’efficienza quantica interna rispetto ai dispositivi non nanostrutturati. Per quanto riguarda i foto-transistor, l’obiettivo è utilizzarli come biosensori compatti e scalabili tramite l’integrazione di cristalli plasmonici sull’area attiva. Il reticolo è stato progettato in modo da massimizzare variazioni di trasmittanza dovute alla modulazione delle risonanze plasmoniche indotta dal legame di bio-molecole sulla superficie. Questo evento è trasdotto in un segnale elettrico misurabile ai capi del dispositivo, come confermato dalle caratterizzazioni sui primi prototipi fabbricati. Il reticolo metallico funziona simultaneamente come struttura plasmonica e come gate elettronico del transistor in un’architettura totalmente integrata.
XXV Ciclo
1984
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Roknuzzaman, Md. "Ab initio atomistic insights into lead-free perovskites for photovoltaics and optoelectronics." Thesis, Queensland University of Technology, 2020. https://eprints.qut.edu.au/198196/1/Md_Roknuzzaman_Thesis.pdf.
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This project focuses on the development of advanced non-toxic materials for the applications in energy generation and consumption devices like solar cells, light-emitting diodes, lasers and photodetectors. A first-principles density functional theory calculations are conducted to investigate the properties of a number of inorganic, hybrid and double perovskites compounds to predict their potential for applications in photovoltaics and optoelectronics. The achieved outcomes provide a better understanding of the structural, electronic, optical and mechanical properties of a group of potential compounds and provide new scientific knowledge to develop non-toxic high-quality organic-inorganic materials for photovoltaic and optoelectronic applications.
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Torrisi, Giacomo. "Transparent Conductors based on Ag Nanolayer embedded in Semiconductor Oxides." Doctoral thesis, Università di Catania, 2019. http://hdl.handle.net/10761/4126.
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Aim of this work is the fabrication, processing and characterization of ultrathin TCO/Ag/TCO transparent electrodes. The study, is also focused on the optimization of structural, optical and electrical properties for several applications. The thesis is organized as follows: Chapter 1: it introduces the optoelectronic devices and their optical and electrical properties. Chapter 2: it presents a detailed discussion of the basic electronic structures and optical properties of TCO materials emphasizing the key properties giving them some unique properties. Chapter 3: it treats of very thin TCO/Ag/TCO multilayer structures grown by RF magnetron sputtering. Synthesis and properties of TCO/Ag/TCO multilayers as a function of different combinations of AZO and ITO top and bottom TCO layers, and as function of the Ag film thickness, are investigated. Chapter 4: it describes the compatibility of the AZO/Ag/AZO multilayers with some practical applications.
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Shih, Grace Hwei-Pyng. "Nanostructure and Optoelectronic Phenomena in Germanium-Transparent Conductive Oxide (Ge:TCO) Composites." Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/228175.
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Nanostructured composites are attracting intense interest for electronic and optoelectronic device applications, specifically as active elements in thin film photovoltaic (PV) device architectures. These systems implement fundamentally different concepts of enhancing energy conversion efficiencies compared to those seen in current commercial devices. This is possible through considerable flexibility in the manipulation of device-relevant properties through control of the interplay between the nanostructure and the optoelectronic response. In the present work, inorganic nanocomposites of semiconductor Ge embedded in transparent conductive indium tin oxide (ITO) as well as Ge in zinc oxide (ZnO) were produced by a single step RF-magnetron sputter deposition process.It is shown that, by controlling the design of the nanocomposites as well as heat treatment conditions, decreases in the physical dimensions of Ge nanophase size provided an effective tuning of the optical absorption and charge transport properties. This effect of changes in the optical properties of nanophase semiconductors with respect to size is known as the quantum confinement effect. Variation in the embedding matrix material between ITO and ZnO with corresponding characterization of optoelectronic properties exhibit notable differences in the presence and evolution of an interfacial oxide within these composites. Further studies of interfacial structures were performed using depth-profiling XPS and Raman spectroscopy, while study of the corresponding electronic effects were performed using room temperature and temperature-dependent Hall Effect. Optical absorption was noted to shift to higher onset energies upon heat treatment with a decrease in the observed Ge domain size, indicating quantum confinement effects within these systems. This contrasts to previous investigations that have involved the introduction of nanoscale Ge into insulating, amorphous oxides. Comparison of these different matrix chemistries highlights the overarching role of interfacial structures on quantum-size characteristics. The opportunity to tune the spectral response of these PV materials, via control of semiconductor phase assembly in the nanocomposite, directly impacts the potential for the use of these materials as sensitizing elements for enhanced solar cell conversion efficiency.
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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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Kovacik, Peter. "Vacuum deposition of organic molecules for photovoltaic applications." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:98461a90-5ae3-4ae3-9245-0f825adafa72.
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Organic photovoltaics have attracted considerable research and commercial interest due to their lightness, mechanical flexibility and low production costs. There are two main approaches for the fabrication of organic solar cells – solution and vacuum processing. The former relies on morphology control in polymer-fullerene blends resulting from natural phase separation in these systems. The latter takes advantage of solvent-free processing allowing highly complex multi-junction architectures similar to inorganic solar cells. This work aims to combine the benefits of both by depositing conjugated polymers using vacuum thermal evaporation. By employing this unconventional approach it aims to enhance the efficiency of organic photovoltaics through increased complexity of the thin-film architecture while improving the nanoscale morphology control of the individual active layers. The thesis explores the vacuum thermal deposition of polythiophenes, mainly poly(3-hexylthiophene) (P3HT) and side-group free poly(thiophene) (PTh). A variety of chemical techniques, such as NMR, FT-IR, GPC, DSC and TGA, are used to examine the effect of heating on chemical structure of the polymers. Optimal processing parameters are identified and related to the resulting thin-film morphology and charge transport properties. Efficient photovoltaic devices based on polythiophene donors and fullerene acceptors are fabricated. Materials science techniques AFM, XRD, SEM, TEM and MicroXAM are used to characterize topography and morphology of the thin films, and UV-Vis, EQE, I-V and C-V measurements relate these to the optical and electronic properties. The results of the study show that polymer side groups have a strong influence on molecular packing and charge extraction in vacuum-deposited polymer thin films. Unlike P3HT, evaporated PTh forms highly crystalline films. This leads to enhanced charge transport properties with hole mobility two orders of magnitude higher than that in P3HT. The effect of molecular order is demonstrated on polymer/fullerene planar heterojunction solar cells. PTh-based devices have significantly better current and recombination characteristics, resulting in improved overall power conversion efficiency (PCE) by 70% as compared to P3HT. This confirms that the chemical structure of the molecule is a crucial parameter in deposition of large organic semiconductors. It is also the first-ever example of vacuum-deposited polymer photovoltaic cell. Next, vacuum co-deposited PTh:C60 bulk heterojunctions with different donor-acceptor compositions are fabricated, and the effect of post-production thermal annealing on their photovoltaic performance and morphology is studied. Co-deposition of blended mixtures leads to 60% higher photocurrents than in thickness-optimized PTh/C60 planar heterojunction counterparts. Furthermore, by annealing the devices post-situ the PCE is improved by as much as 80%, achieving performance comparable to previously reported polythiophene and oligothiophene equivalents processed in solution and vacuum, respectively. The enhanced photo-response is a result of favourable morphological development of PTh upon annealing. In contrast to standard vacuum-processed molecular blends, annealing-induced phase separation in PTh:C60 does not lead to the formation of coarse morphology but rather to an incremental improvement of the already established interpenetrated nanoscale network. The morphological response of the evaporated PTh within the blend is further verified to positively differ from that of its small-molecule counterpart sexithiophene. This illustrates the morphological advantage of polymer-fullerene combination over all other vacuum-processable material systems. In conclusion, this processing approach outlines the conceptual path towards the most beneficial combination of solution/polymer- and vacuum-based photovoltaics. It opens up a fabrication method with considerable potential to enhance the efficiency of large-scale organic solar cells production.
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Becker, Pascal [Verfasser]. "Structural and Optoelectronic Properties, Phase Transitions, and Degradation of Semiconducting CsPbI3-Perovskite Thin-Films for Photovoltaics / Pascal Becker." Wuppertal : Universitätsbibliothek Wuppertal, 2019. http://d-nb.info/120422255X/34.
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Bondi, Luca. "Photocurrent generation at organic heterojunction-electrolyte interface for optoelectronic biosensor implementation." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2019.
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This thesis project investigates an organic heterojunction made by common and largely available inert dyes which can operate in cellular fluid without being toxic for their environment. The heterojunction/electrolyte interface converts light into an ionic current pulse strong enough to depolarize adjacent cells. Indeed, such a photoelectrode is envisioned to act as a building block in an artificial retina.
In order to achieve this goal, detailed characterization and understanding of the charge generation mechanism is necessary. To this end I realized two experimental configurations that characterize a photoelectrode made of a p/n junction cast over ITO. In the first configuration, the photoelectrode was studied in a three-electrode electrochemical cell under pulsed LED light stimulation. Using different analytical techniques, I characterized the photoelectrodes impedance and photocurrent transients as a function of a well-defined externally applied potential. In the second configuration I extended the experiment to assess the impact of a more realistic floating photoelectrode operation. In this situation the photoelectrode circuit is closed by a second, passive electrode interface that converts the ionic current back into an electronic one. As a consequence, the potential is no longer defined and I demonstrate that the properties of the passive electrode can be optimized to maximize the capacitive currents and minimize the faradic ones.
The following thesis is organized in three main chapters: first an introduction, where I provide an essential background; then methods and materials, where are described the investigated system, the models used for its interpretation and the methods used to take the measurements; then result and discussion, where the measurements made in the non-floating and floating arrangements and their explicative model are presented and discussed, and simulation are performed and compared to the experimental results.
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Lini, Matilde. "Optoelectronic characterization of hybrid organic-inorganic halide perovskites for solar cell and X-ray detector applications." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/23213/.
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In the last 10 years, the research interest has been drawn towards the hybrid organic-inorganic halide perovskites, an innovative material characterized by remarkable optoelectronic properties and by its simplicity of fabrication; hybrid halide perovskites are currently being employed as active material in solar cells, X-ray photodetectors and light emitting devices.
The following thesis presents the characterization of two perovskite-based materials. The first is a methylammonium lead iodide (MAPbI3) thin film solar cell, which has been
fabricated and characterized at the University of Konstanz (Germany), with the aim to optimize the deposition procedure. The second material is a methylammonium lead bromide (MAPbBr3) single crystal that have been characterized at the University of
Bologna with surface photovoltage and photocurrent spectroscopies, as a function of the deposited dose of X-rays in order to monitor the induced effects of radiation.
After the exposure to X-rays, the exciton binding energy, calculated from the surface photovoltage spectra, has been found to increase by 20 meV with respect to the not irradiated sample. A similar result has been found with the photocurrent spectroscopy. The reasons for the increase in binding energy is discussed and attributed to a change in polarizability of the single crystal. The recovery of the crystals has been registered as well and has shown that the material is able to return to the initial condition after just few hours from the last X-ray's deposition.
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Hallani, Rawad Kamal. "Designing Anthradithiophene Derivatives Suitable For Applications in Organic Electronics and Optoelectronics." UKnowledge, 2015. http://uknowledge.uky.edu/chemistry_etds/61.
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Anthradithiophene (ADT) derivatives have proven to be a front-runner in the world of small molecule semiconductors for organic electronics and optoelectronics. This is mainly due to the improved stability, easy tuning of chemical and physical properties, and impressive device performance that these molecules possess, especially in organic field effect transistors (OFET) and organic photovoltaics (OPV). The second chapter of this dissertation shows that reducing the amount of alkylsilylethynyl groups, used for functionalizing and solubilizing the ADT backbone, does alter the chemical, physical and crystallographic properties of ADTs. These changes offer the opportunity to study and observe different intermolecular interactions as well as monitoring their influence on sulfur scrambling in solid state. Additionally, from the early days ADTs and functionalized ADTs have been synthesized as isomeric mixtures. In chapter three, I demonstrate a new and simple method that can separate the syn and anti isomers of the F-TES-ADT and F-TEG-ADT chromatographically. The effects of isomeric purity on crystal packing and field effect transistor performance were studied extensively.
Chapter four of this dissertation reveals a new generation of acceptor (electron poor) ADT derivatives obtained by attaching cyanide as electron withdrawing group (EWG) to the ADT chromophore. An extensive study was conducted on CN-ADT (acceptor) molecules in small molecule (F-TES-ADT) donor/ small molecule (CN-ADT) acceptor binary BHJ blends as well as P3HT/CN-ADT/PCBM ternary BHJ blends. Photophysical studies of the Donor/ acceptor blends (interface, domains, and crystal orientation) were conducted to obtain a better understanding of the film morphology and its effect on solar cell performance.
Finally, the last part of the dissertation, Chapter five, focus on studying singlet fission in ADT derivatives, as well as the effect of varying the size of the alkylsilylethynyl functional group (used for solubilizing the ADT backbone) on altering the electronic couplings and how can that potentially affect the singlet fission rate in these molecules. We also tried to inspect the extent of the correlation between long-range order in crystal packing and singlet fission by monitoring singlet fission rate and efficiency for ADT derivatives with different thin film morphologies.
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Kim, Vincent Oteyi. "Ultrafast spectroscopy of organic semiconductors : singlet fission and nonfullerene acceptors for organic photovoltaics." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/283561.
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In this dissertation, we investigate two emerging strategies for enhancing the performance of organic photovoltaics. The first takes advantage of a process called singlet exciton fission, and the second embodies an exodus from the fullerene electron acceptors prominent in organic solar cells. Indeed, this versatile class of tunable small molecules are aptly termed nonfullerene acceptors. However, both strategies would benefit from a greater understanding of underlying principles. Singlet exciton fission is a photon-multiplying process in which a singlet exciton from a high-energy absorbed photon splits into two triplet excitons. The process could significantly reduce energy lost to heat in photovoltaic devices, but its mechanisms are still misunderstood. One model involves direct coupling between the singlet and triplet states, and another model involves an intermediate charge transfer state. Transient absorption spectroscopy allowed us to examine singlet fission in films of pentacene, fluorinated pentacene, and coevaporated blends of various mixing ratios. We directly observe an intermolecular charge transfer state during singlet fission in solid films of coevaporated pentacene and peruoropentacene, which supports the model of charge transfer state-mediated singlet fission. Furthermore, we successfully induced singlet fission in one blend by directly exciting the charge transfer state below the bandgap. We use various types of steady state and time-resolved spectroscopy to characterize two types of nonfullerene electron acceptors. The first type is a group of tetraazabenzodiuoranthene diimide (BFI) dimers and a BFI monomer. The BFI dimers were designed to have twisted, nonplanar 3-dimensional structures and have helped achieve power conversion efficiencies of over 8% in organic solar cells. The other type of nonfullerene acceptor is a calamitic small molecule, and we consider the BAF-4CN electron acceptor, which has also been used in a solar cell whose efficiency exceeded 8%. Spectroscopic studies give insight into the performances of these nonfullerene devices in relation to fullerene-derivative counterparts. We find that the nonfullerene blends suffer from more geminate charge recombination. However, despite this drawback, in some cases, slower rates of nongeminate recombination may lead to successful power conversion efficiencies in nonfullerene solar cells.
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Hosatte, Mikaël. "Nanostructured silicon-based metamaterial and its process of fabrication for applications in optoelectronics and energy." Thesis, Strasbourg, 2014. http://www.theses.fr/2014STRAD019.
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Des nanostructures basées sur des différences de cristallinité ont été insérées dans des cellules test en silicium par des techniques d’amorphisation innovantes. Un nouveau mécanisme de multiplication de porteurs a ainsi été observé. Cet effet peut provenir des niveaux d’énergie électronique introduits par de grandes densités locales de bi-lacunes. Un principe de fonctionnement impliquant des mécanismes à niveaux d’énergie multiples et un transport électronique rapide au sein de la bande d’énergie des atomes de phosphore non-ionisés a également été proposé. Cela conduit à une asymétrie favorable entre la génération et la recombinaison des porteurs libres.L’énergie nécessaire à un photon pour enclencher le procédé s’est révélée plus petite que deux fois celle de la bande interdite. L’amélioration du rendement photovoltaïque devient donc concevable et une nouvelle génération de cellules solaires à haute efficacité pourrait ainsi émerger de cet effet de multiplication à faible-énergieNanostructures based on differences of crystallinity have been embedded into all-silicon test devices by innovative amorphization techniques and a new carrier multiplication mechanism was observed. This effect can indeed originate from the electron energy levels resulting from the high densities of divacancies localized at the crystalline/amorphous interfaces.An operating principle involving multiple energy level mechanisms and fast electronic transport within the unionized phosphorus energy band was also advanced. It led to a favourable asymmetry between generation and recombination of free carriers.Besides, contrary to other carrier multiplication effects, photon energy lower than twice the band gap was found sufficient to initiate the process. The enhancement of photovoltaic yields becomes therefore conceivable and propositions of prototypes are made. A new generation of high efficiency solar cells may then emerge from this Low-Energy Electron Multiplication effect
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Ripollés, Sanchis Teresa. "Interfacial and Bulk Operation of Polymeric Solar Cells by Optoelectronics and Structural Techniques." Doctoral thesis, Universitat Jaume I, 2014. http://hdl.handle.net/10803/277095.
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This Ph.D. Thesis focuses on the investigation of organic photovoltaic (OPV) technology, especially in aspects of experimental device processing, and optoelectronic and electrical characterization on OPV devices to be readily marketable. More specifically, the topics addressed are the following: origin of recombination current,open-circuit voltage and crystallinity, transport driving force, contact selectivity and interface states, alternative hole transporting layers and oxygen and degradation routes.
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Pandolfi, Silvia. "High-pressure pathways towards new functional Si-based materials with tailored optoelectronic properties and their characterization." Electronic Thesis or Diss., Sorbonne université, 2019. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2019SORUS459.pdf.
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Dans cet ouvrage, le traitement à haute température et haute pression est utilisé pour développer et optimiser la synthèse de nouvelles formes exotiques du silicium. La synthèse de nouvelles phases de silicium est un point clé dans le développement de technologies à base de Si, en particulier l'énergie solaire. Le développement de nouveaux matériaux à base de silicium à haut rendement pourrait faire face à la fois à l'optimisation des performances et à la réduction des coûts. Au niveau industriel, la haute pression a été principalement utilisée pour la synthèse des diamants et des matériaux super-durs, mais des études récentes ont prouvé qu’elle est également efficace pour la synthèse de nouveaux matériaux à base de silicium à propriétés remarquables pour les applications. Nous abordons ce défi sous tous ses aspects, à partir de l'étude des mécanismes de transition à haute pression jusqu’à la synthèse et à la caractérisation d'un nouveau matériau de silicium. Nous utilisons la diffraction in situ de rayons X à haute-pression haute-température pour observer et caractériser des transitions de phase du silicium et leur dynamique. Grâce à nos résultats, nous donnons de nouvelles perspectives capables de clarifier certains aspects du diagramme de phase du silicium qui étaient encore en discussion. Nous obtenons la première synthèse de silicium hexagonal pur, un défi de longue date dans le domaine. Grâce à notre échantillon de phase pure, nous caractérisons ses propriétés physiques et structurales. Nous prouvons que le silicium hexagonal obtenu à partir du traitement haute pression est sous forme du polytype 4H (séquence d'empilement ABCB). D'autres caractérisations structurelles révèlent une nanostructure hiérarchique dans la morphologie de l'échantillon. La découverte et la caractérisation de nanoparticules quasi-2D accessibles à la manipulation ouvrent de nouvelles perspectives pour le développement de nouveaux dispositifs optoélectroniquesIn this work, high-pressure high-temperature treatment is used to develop and optimize synthetic pathways to new and exotic forms of silicon. The synthesis of new phases of silicon is a key point in the future development of Si-based technology, especially for solar energy. Development of new Si-based materials with high-efficiency could both optimise the performances and reduce the costs. At an industrial level, high-pressure has been mainly used for the synthesis of diamonds and super-hard materials, but recent studies have proven it also efficient in the synthesis of new silicon-based materials with enhanced properties for applications. We tackle this challenge in all its aspects, starting from the study of transition mechanisms at high-pressure and arriving to the synthesis and characterization of a new silicon material. We use in-situ x-ray diffraction at high-pressure high-temperature conditions to monitor and characterize silicon phase transitions and their dynamics. Our results give new insights that clarify some aspects of the silicon phase diagram that were still a matter of debate. We obtain the first synthesis of pure hexagonal silicon, a longstanding challenge in the field. Thanks to our pure-phase sample, we characterize its physical and structural properties. We prove that hexagonal silicon obtained from high-pressure is in the form of 4H polytype (ABCB stacking sequence). Further structural characterizations reveal a hierarchical nanostructure in the pristine morphology of the sample. Discovery and characterization of discrete quasi-2D nanoparticles accessible for manipulation opens new perspectives for the design of new optoelectronic devices
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Greul, Enrico [Verfasser], and Thomas [Akademischer Betreuer] Bein. "On the way to non-toxic and highly stable perovskite-based optoelectronics : synthesis and investigations of lead-free perovskites for photovoltaic applications / Enrico Greul ; Betreuer: Thomas Bein." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2019. http://d-nb.info/119109815X/34.
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Ego, Christophe. "Oligo and polyfluorenes of controlled architecture for applications in opto-electronics." Doctoral thesis, Universite Libre de Bruxelles, 2005. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210958.
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Polyfluorenes are polymers with outstanding properties: They are semi-conducting, relatively rigid, quite stable chemically and thermally, easily substituted and therefore potentially soluble in numerous solvents and more importantly, they exhibit blue electro- and photoluminescence. For all these reasons, these polymers are the subjects of numerous academic and industrial researches.The first subject of this work deal with the design, the synthesis and the characterisation of polyfluorenes end-capped with perylene dicarboximide derivatives. These perylene moieties are able to interact by energy transfer under specific conditions of illumination, proximity and orientation. Their observation by single molecule spectroscopy permitted therefore to gain valuable information concerning the three-dimensional folding of single polyfluorene chains. To complete this study, the synthesis and characterisation of a perylene end-capped trimer of fluorene was performed. This structure being monodisperse, a finer analysis of the energy-transfer occurring between both perylene dyes could be accomplished, which confirmed the structural hypothesis made for the polymer. During these studies, it has been observed that, in addition to the energy transfer occurring between both perylene derivatives, another energy transfer occurs between the polyfluorene backbone and the perylene derivatives upon excitation of the first. This led to the idea of the synthesis of a polyfluorene bearing perylenes dicarboximide as side chains. This perylene-rich polyfluorene has been used to build a photovoltaic cell efficient in the wavelengths of both polyfluorene absorption and perylene carboximide absorption.
Another subject of this work was the design, synthesis and characterisation of polyfluorenes bearing bulky phenoxy groups as side-chains. These polymers, due to their lower tendency toward aggregation, exhibited a better stability of their emission colour upon annealing. Similarly, a series of homo- and copolymers of fluorene bearing bulky and hole accepting triphenylamine substituants was synthesised and characterised. In addition to their improved colour stability in comparison with dialkylpolyfluorenes, the LEDs build with these materials exhibited a very low turn on voltage.
Doctorat en sciences, Spécialisation chimie
info:eu-repo/semantics/nonPublished
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Deng, Zeyu. "Rational design of novel halide perovskites combining computations and experiments." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/287932.
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The perovskite family of materials is extremely large and provides a template for designing materials for different purposes. Among them, hybrid organic-inorganic perovskites (HOIPs) are very interesting and have been recently identified as possible next generation light harvesting materials because they combine low manufacturing cost and relatively high power conversion efficiencies (PCEs). In addition, some other applications like light emitting devices are also highly studied. This thesis starts with an introduction to the solar cell technologies that could use HOIPs. In Chapter 2, previously published results on the structural, electronic, optical and mechanical properties of HOIPs are reviewed in order to understand the background and latest developments in this field. Chapter 3 discusses the computational and experimental methods used in the following chapters. Then Chapter 4 describes the discovery of several hybrid double perovskites, with the formula (MA)$_2$M$^I$M$^{III}$X$_6$ (MA = methylammonium, CH$_3$NH$_3$, M$^I$ = K, Ag and Tl, M$^{III}$ = Bi, Y and Gd, X = Cl and Br). Chapter 5 presents studies on the variable presure and temperature response of formamidinium lead halides FAPbBr$_3$ (FA = formamidinium, CH(NH$_2$)$_2$) as well as the mechanical properties of FAPbBr$_3$ and FAPbI$_3$, followed by a computational study connecting the mechanical properties of halide perovskites ABX$_3$ (A = K, Rb, Cs, Fr and MA, X = Cl, Br and I) to their electronic transport properties. Chapter 6 describes a study on the phase stability, transformation and electronic properties of low-dimensional hybrid perovskites containing the guanidinium cation Gua$_x$PbI$_{x+2}$ (x = 1, 2 and 3, Gua = guanidinium, C(NH$_2$)$_3$). The conclusions and possible future work are summarized in Chapter 7. These results provide theoreticians and experimentalists with insight into the design and synthesis of novel, highly efficient, stable and environmentally friendly materials for solar cell applications as well as for other purposes in the future.
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Regrettier, Thomas. "Modulateurs de lumière à commande optique composés d'une couche photovoltaïque organique." Thesis, Strasbourg, 2017. http://www.theses.fr/2017STRAD038.
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Les performances des modulateurs de lumières à commande optique (OASLMs) à base de cristaux liquides (CLs) dépendent fortement des propriétés de la couche photosensible. Afin de concilier transparence, résolution latérale et production à bas coûts, les semi-conducteurs organiques apparaissent comme des candidats idéaux. Nous avons choisi d'utiliser un mélange P3HT:PCBM comme couche photosensible. Nos résultats ont montré que les cristaux liquides se réorientaient en fonction de l'intensité lumineuse seule et sans tension appliquée. Des mesures complémentaires indiquent que l'effet photovoltaïque est à l'origine de ce phénomène. Ce type de dispositif nous permet de moduler spatialement l'orientation des CLs et démontre son potentiel dans des applications liées à l'holographie. Un second type de dispositif intégrant des couches d'interfaces de PEIE et de PEDOT:PSS nous permet de contrôler l'orientation des CLs et donne de nouvelles pistes permettant de fabriquer des OASLMs autonomesThe performances of liquid crystals (LCs) based optically addressed Spatial Light Modulators (OASLMs) strongly depends on the photosensitive layer properties. To accommodate device transparency, lateral resolution and low cost production, organic semiconductors appear as the ideal candidates. We chose to use a P3HT: PCBM blend as the photosensitive layer. Our results showed that the liquid crystals reorient according to the luminous intensity alone and without external power supply. Additional measurements indicate that the photovoltaic effect is at the origin of this phenomenon. This type of device allowed spatial modulation of the LCs orientation and demonstrates its potential in holographic applications. A second type of device integrating interfacial layers of PEIE and PEDOT: PSS allowed us to control the orientation of the LCs and gives promising routes towards the design of self-sustainable OASLMs
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Le, Borgne Damien. "Photovoltaïque organique : étude des interactions électroniques aux interfaces des hétérojonctions organiques." Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30147/document.
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Du fait de leur faible coût de production et de leur intégration possible sur substrat flexible, les cellules photovoltaïques organiques sont prometteuses pour répondre aux besoins futurs en énergie. Leurs performances reposent sur l'architecture de la cellule et sur la nature des matériaux choisis. Par conséquent, le contrôle à l'échelle nanométrique de la couche active (formation de nanodomaines purs, organisation moléculaire...), ainsi que le développement de nouvelles molécules aux propriétés électroniques et structurales optimisées apparaissent comme des paramètres clés. Dans ce contexte, les travaux présentés dans cette thèse visent à étudier le lien entre la morphologie des films minces et les propriétés de transport à l'échelle nanométrique en fonction des matériaux actifs utilisés. Pour cela deux voies ont été explorées. La première voie repose sur l'utilisation des propriétés d'auto-organisation des cristaux liquides pour améliorer la formation et l'organisation de nanodomaines. Pour cette étude, nous avons choisi d'associer un donneur d'électron classique, le poly-3-hexylthiophène (P3HT), et de le mélanger avec un complexe de nickel [Ni(4dopedt)2] possédant des propriétés cristallines liquides colonnaires. L'étude par Microscopie à Force Atomique (AFM), Conductive-AFM (C-AFM), absorption UV-visible et spectrométrie Raman des films de mélanges démontre l'effet structurant du cristal liquide sur les chaînes de P3HT, en fonction de l'épaisseur de la couche et des traitements thermiques effectués. La deuxième voie explorée repose sur l'ingénierie moléculaire. Suite à une étude bibliographique, nous avons conçu puis synthétisé différentes petites molécules fluorées capables d'agir comme accepteurs d'électrons. Leur synthèse est réalisée en plusieurs étapes, privilégiant une méthode de couplage innovante, l'hétéroarylation directe. Les molécules obtenues ont été caractérisées par les techniques analytiques classiques, puis soumises à une étude de relation structures/propriétés. D'une part, les analyses optiques, électrochimique et thermique ont révélé leur grande stabilité et leur intérêt potentiel pour l'application visée. D'autre part, leur étude en film mince, par spectroscopie d'absorption UV-visible, de fluorescence et par AFM, révèle l'influence de la substitution du squelette conjugué par des atomes de fluor ainsi que de la modification des chaînes alkyles des groupements terminaux sur les propriétés optoélectroniques et structurelles des moléculesOrganic solar cells appear as a promising technology to meet future energy requirements, owing to their low production costs, their great flexibility and their ability to be integrated into light devices. Their performances rely on their architecture and the nature of the chosen materials. As a consequence, two of the key parameters for their development are the control the active layer at a nanometric scale (molecular organisation and the formation of pure compound nanodomains) and the development of new small molecules with optimized electronic and structural properties. This work comes in that aim : the study of the relation between thin film morphology and transport properties at the nanometric scale as function of the chosen materials. Two ways have been explored. The first way relied on self-organisation properties of a liquid crystal for improving the formation and organisation of nanodomains. In this purpose, we have associated a well-known electron donor, the poly-3-hexylthiophene (P3HT), with a complex of nickel, named as [Ni(4dopedt)2], exhibiting columnar liquid crystal properties. Atomic Force Microscopy (AFM), Conductive-AFM (C-AFM), UV-visible absorption and Raman spectroscopy on bulk films have shown the structuring effect of the liquid crystal on the P3HT chains as a function of the films thicknesses and thermal annealing. The second way was based on molecular engineering. Following a bibliographic study, we have designed and synthetized different fluorinated small molecules with electron acceptor capability. For this, a more economical and cleaner synthesis technique has been employed: the direct arylation. These molecules have been characterized by classical analytic technics, and a study of the relation between structure and properties has been carried out. On the one hand, optical, electrochemical and thermal analyses have shown their good stability and their potential for the aimed application. On the other hand, their study in thin film by UV-visible absorption, fluorescence and AFM have shown the influence of backbone substitution by fluorine atoms as well as the impact of the nature of alkyl end chains on the optoelectronic and structural properties of these molecules
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Lepage, Hadrien. "Modélisation de solides à nanocristaux de silicium." Phd thesis, INSA de Lyon, 2012. http://tel.archives-ouvertes.fr/tel-00753248.
Full textAbstract:
Les propriétés physico-chimiques d'un nanocristal semi-conducteur sphérique, intermédiaires entre la molécule et le solide, dépendent de sa taille. Empilés ou dispersés, ces nanocristaux sont les briques architecturales de nouveaux matériaux fonctionnels aux propriétés ajustables, en particulier pour l'optoélectronique. Cette thèse s'inscrit dans le développement de ces nouveaux matériaux et présente avant tout une méthodologie pour la simulation du transport électronique dans un solide à nanocristaux en régime de faible couplage électronique appliquée à des nanocristaux de silicium dans une matrice de SiO2 pour les applications photovoltaïques. La cinétique du déplacement des porteurs est liée au taux de transfert tunnel (hopping) entre nanocristaux. Ces taux sont calculés dans le cadre de la théorie de Marcus et prennent en compte l'interaction électron-phonon dont l'effet du champ de polarisation dans la matrice ainsi que les interactions électrostatiques à courte et longue portée. Le calcul des états électroniques (électrons et trous) en théorie k.p associé à l'utilisation de la formule de Bardeen donne au code la capacité, par rapport à la littérature, de fournir des résultats (mobilité ou courant) en valeur absolue. Les résultats de mobilité ainsi obtenus pour des empilements cubiques idéaux viennent contredire les résultats de la littérature et incitent à considérer d'autres matériaux notamment en ce qui concerne la matrice pour obtenir de meilleurs performances. En outre, les résultats de simulation de dispositifs montrent l'impact considérable des électrodes sur les caractéristiques courant-tension. Aussi, un nouvel algorithme Monte-Carlo Cinétique accéléré a été adapté afin de pouvoir reproduire le désordre inhérent à la méthode de fabrication tout en maintenant un temps de simulation raisonnable. Ainsi l'impact du désordre en taille se révèle faible à température ambiante tandis que les chemins de percolation occultent la contribution des autres chemins de conduction. Des résultats de caractérisation comparés aux simulations tendent par ailleurs à indiquer que ces chemins peuvent concentrer les porteurs et exhiber un phénomène de blocage de coulomb. Enfin, la section efficace d'absorption est calculée théoriquement et permet d'obtenir le taux de génération sous illumination qui se révèle proche du silicium massif. Et une méthode en microscopie à sonde de Kelvin est décrite pour caractériser la durée de vie des porteurs c'est-à-dire le taux de recombinaison, les résultats ainsi obtenus étant cohérents avec d'autres techniques expérimentales.
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Fountaine, Katherine Theresa. "Mesoscale Optoelectronic Design of Wire-Based Photovoltaic and Photoelectrochemical Devices." Thesis, 2015. https://thesis.library.caltech.edu/8928/1/Fountaine_PhDThesis_FinalComplete.pdf.
Full textAbstract:
The overarching theme of this thesis is mesoscale optical and optoelectronic design of photovoltaic and photoelectrochemical devices. In a photovoltaic device, light absorption and charge carrier transport are coupled together on the mesoscale, and in a photoelectrochemical device, light absorption, charge carrier transport, catalysis, and solution species transport are all coupled together on the mesoscale. The work discussed herein demonstrates that simulation-based mesoscale optical and optoelectronic modeling can lead to detailed understanding of the operation and performance of these complex mesostructured devices, serve as a powerful tool for device optimization, and efficiently guide device design and experimental fabrication efforts. In-depth studies of two mesoscale wire-based device designs illustrate these principles—(i) an optoelectronic study of a tandem Si|WO3 microwire photoelectrochemical device, and (ii) an optical study of III-V nanowire arrays.
The study of the monolithic, tandem, Si|WO3 microwire photoelectrochemical device begins with development and validation of an optoelectronic model with experiment. This study capitalizes on synergy between experiment and simulation to demonstrate the model’s predictive power for extractable device voltage and light-limited current density. The developed model is then used to understand the limiting factors of the device and optimize its optoelectronic performance. The results of this work reveal that high fidelity modeling can facilitate unequivocal identification of limiting phenomena, such as parasitic absorption via excitation of a surface plasmon-polariton mode, and quick design optimization, achieving over a 300% enhancement in optoelectronic performance over a nominal design for this device architecture, which would be time-consuming and challenging to do via experiment.
The work on III-V nanowire arrays also starts as a collaboration of experiment and simulation aimed at gaining understanding of unprecedented, experimentally observed absorption enhancements in sparse arrays of vertically-oriented GaAs nanowires. To explain this resonant absorption in periodic arrays of high index semiconductor nanowires, a unified framework that combines a leaky waveguide theory perspective and that of photonic crystals supporting Bloch modes is developed in the context of silicon, using both analytic theory and electromagnetic simulations. This detailed theoretical understanding is then applied to a simulation-based optimization of light absorption in sparse arrays of GaAs nanowires. Near-unity absorption in sparse, 5% fill fraction arrays is demonstrated via tapering of nanowires and multiple wire radii in a single array. Finally, experimental efforts are presented towards fabrication of the optimized array geometries. A hybrid self-catalyzed and selective area MOCVD growth method is used to establish morphology control of GaP nanowire arrays. Similarly, morphology and pattern control of nanowires is demonstrated with ICP-RIE of InP. Optical characterization of the InP nanowire arrays gives proof of principle that tapering and multiple wire radii can lead to near-unity absorption in sparse arrays of InP nanowires.