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Yuan, Chunze. "The Study of II-VI Semiconductor Nanocrystals Sensitized Solar Cells." Licentiate thesis, KTH, Teoretisk kemi och biologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-93752.
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Semiconductor nanocrystals, also referred to as quantum dots (QDs), have been the focus of great scientific and technological efforts in solar cells, as a result of their advantages of low-cost, photostability, high molar extinction coefficients and size-dependent optical properties. Due to the multi-electron generation effect, the theoretically maximum efficiency of quantum dots-sensitized solar cells (QDSCs) is as high as 44%, which is much higher than that of dye-sensitized solar cells (DSCs). Thus QDSCs have a clear potential to overtake the efficiency of all other kinds of solar cells. In recent years, the efficiency of QDSCs has been improved very quickly to around 5%. It is however still much lower than that of DSCs. The low efficiency is mostly caused by the high electron loss between electrolyte and electrodes and the lack of an efficient electrolyte. In this thesis, we have been working to enhance the performance of QDSCs with II-VI group nanocrystals by increasing the electron injection efficiency from QDs to TiO2 and developing new redox couples in electrolyte. To increase the electron injection, firstly, colloidal ZnSe/CdS type-II QDs were synthesized and applied for QDSCs for the first time, whose photoelectron and photohole are located on CdS shell and ZnSe core, respectively. The spatial separation between photoelectron and photohole can effectively enhance the charge extraction efficiency, facilitating electron injection, and also effectively expand the absorption spectrum. All these characteristics contribute to the high photon to current conversion efficiency. Furthermore, a comparison between the performances of ZnSe/CdS and CdS/ZnSe QDs shows that the electron distribution is important for the electron injection of the QDs in QDSCs. Secondly, colloidal CdS/CdSe quantum rods (QRs) were applied to a quantum rod-sensitized solar cell (QRSCs) that showed a higher electron injection efficiency than analogous QDSCs. It is concluded that reducing the carrier confinement dimensions of nanocrystals can improve electron injection efficiency of nanocrystal sensitized solar cells. In this thesis, two types of organic electrolytes based McMT-/BMT and TMTU/TMTU-TFO were used for QDSCs. By reducing the charge recombination between the electrolyte and counter electrode, fill factor (FF) of these QDSCs was significantly improved. At the same time, the photovoltages of the QDSCs were remarkably increased. As a result, the overall conversion efficiency of QDSCs based on the new electrolytes was much higher than that with a commonly used inorganic electrolyte. In addition, CdS QDSCs on NiO photoelectrode were studied which shows a n-type photovoltaic performance. This performance is attributed to the formation of a thin Cd metal film before CdS QDs formation on NiO. Since the CB edge of CdS sits between the Fermi level and the CB edge of Cd metal, a much strong electron transfer between Cd and CdS QD is obtained, resulting in the observed n-type photovoltaic performance of these CdS/NiO QDSCs.QC 20120425
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Razgoniaeva, Natalia Razgoniaeva. "Photochemical energy conversion in metal-semiconductor hybrid nanocrystals." Bowling Green State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1465822519.
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Cattley, Christopher Andrew. "Quaternary nanocrystal solar cells." Thesis, University of Oxford, 2016. http://ora.ox.ac.uk/objects/uuid:977e0f75-e597-4c7a-8f72-6a26031f8f0b.
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This thesis studies quaternary chalcogenide nanocrystals and their photovoltaic applications. A temperature-dependent phase change between two distinct crystallographic phases of stoichiometric Cu2ZnSnS4 is investigated through the development of a one pot synthesis method. Characterisation of the Cu2ZnSnS4 nanocrystals was performed using absorption spectroscopy, transmission electron microscopy (TEM) and powder X-ray diffraction (XRD). An investigation was conducted into the effects of using hexamethyldisilathiane (a volatile sulphur precursor) in the nucleation of small (<7nm), mono-dispersed and solution-stable quaternary Cu2ZnSnS4 nanocrystals. A strategy to synthesize high quality thermodynamically stable kesterite Cu2ZnSnS4 nanocrystals is established, which subsequently enabled the systematic study of Cu2ZnSnS4 nanocrystal formation mechanisms, using optical characterization, XRD, TEM and Raman spectroscopy. Further studies employed scanning transmission electron microscopy (STEM) energy dispersive x-ray (EDX) mapping to examine the elemental spatial distributions of Cu2ZnSnS4 nanocrystals, in order to analyse their compositional uniformity. In addition, the stability of nanocrystals synthesised using alternative ligands is investigated using Fourier transform infrared spectroscopy, without solution based ligand substitution protocol is used to replace aliphatic reaction ligands with short, aromatic pyridine ligands in order to further improve Cu2ZnSnS4 colloid stability. A layer-by-layer spin coating method is developed to fabricate a semiconductor heterojunction, using CdS as an n-type window, which is utilised to investigate the photovoltaic properties of Cu2ZnSnS4 nanocrystals. Finally, three novel passivation techniques are investigated, in order to optimise the optoelectronic properties of the solar cells to the point where a power conversion efficiency (PCE) of 1.00±0.04% is achieved. Although seemingly modest when compared to the performance of leading devices (PCE>12%) this represents one of the highest obtained for a Cu2ZnSnS4 nanocrystal solar cell, fabricated completely under ambient conditions at low temperatures.
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Nemitz, Ian R. "Synthesis of Nanoscale Semiconductor Heterostructures for Photovoltaic Applications." Bowling Green State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1277087935.
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Li, Guangru. "Nanostructured materials for optoelectronic devices." Thesis, University of Cambridge, 2016. https://www.repository.cam.ac.uk/handle/1810/263671.
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This thesis is about new ways to experimentally realise materials with desired nano-structures for solution-processable optoelectronic devices such as solar cells and light-emitting diodes (LEDs), and examine structure-performance relationships in these devices. Short exciton diffusion length limits the efficiency of most exciton-based solar cells. By introducing nano-structured architectures to solar cells, excitons can be separated more effectively, leading to an enhancement of the cell’s power conversion efficiency. We use diblock copolymer lithography combined with solvent-vapour-assisted imprinting to fabricate nano-structures with 20-80 nm feature sizes. We demonstrate nanostructured solar cell incorporating the high-performance polymer PBDTTT-CT. Furthermore, we demonstrated the patterning of singlet fission materials, including a TIPS-pentacene solar cell based on ZnO nanopillars. Recently perovskites have emerged as a promising semiconductor for optoelectronic applications. We demonstrate a perovskite light-emitting diode that employs perovskite nanoparticles embedded in a dielectric polymer matrix as the emissive layer. The emissive layer is spin-coated from perovskite precursor/polymer blend solution. The resultant polymer-perovskite composites effectively block shunt pathways within the LED, thus leading to an external quantum efficiency of 1.2%, one order of magnitude higher than previous reports. We demonstrate formations of stably emissive perovskite nanoparticles in an alumina nanoparticle matrix. These nanoparticles have much higher photoluminescence quantum efficiency (25%) than bulk perovskite and the emission is found to be stable over several months. Finally, we demonstrate a new vapour-phase crosslinking method to construct full-colour perovskite nanocrystal LEDs. With detailed structural and compositional analysis we are able to pinpoint the aluminium-based crosslinker that resides between the nanocrystals, which enables remarkably high EQE of 5.7% in CsPbI3 LEDs.
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Wong, Henry Mo Pun. "Semiconducting nanocrystals for hybrid solar cells." Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.613367.
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Ehrler, Bruno. "Nanocrystalline solar cells." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.607785.
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Schnabel, Manuel. "Silicon nanocrystals embedded in silicon carbide for tandem solar cell applications." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:da5bbb64-0bcd-4807-a9f3-4ff63a9ca98d.
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Tandem solar cells are potentially much more efficient than the silicon solar cells that currently dominate the market but require materials with different bandgaps. This thesis presents work on silicon nanocrystals (Si-NC) embedded in silicon carbide (SiC), which are expected to have a higher bandgap than bulk Si due to quantum confinement, with a view to using them in the top cell of a tandem cell. The strong photoluminescence (PL) of precursor films used to prepare Si-NC in SiC (Si-NC/SiC) was markedly reduced upon Si-NC formation due to simultaneous out-diffusion of hydrogen that passivated dangling bonds. This cannot be reversed by hydrogenation and leads to weak PL that is due to, and limited by, non-paramagnetic defects, with an estimated quantum yield of ≤5×10-7. Optical interference was identified as a substantial artefact and a method proposed to account for this. Majority carrier transport was found to be Ohmic at all temperatures for a wide range of samples. Hydrogenation decreases dangling bond density and increases conductivity up to 1000 times. The temperature-dependence of conductivity is best described by a combination of extended-state and variable-range hopping transport where the former takes place in the Si nanoclusters. Furthermore, n-type background doping by nitrogen and/or oxygen was identified. In the course of developing processing steps for Si-NC-based tandem cells, a capping layer was developed to prevent oxidation of Si-NC/SiC, and diffusion of boron and phosphorus in nanocrystalline SiC was found to occur via grain boundaries with an activation energy of 5.3±0.4 eV and 4.4±0.7 eV, respectively. Tandem cells with a Si-NC/SiC top cell and bulk Si bottom cell were prepared that exhibited open-circuit voltages Voc of 900 mV and short-circuit current densities of 0.85 mAcm-2. Performance was limited by photocurrent collection in the top cell; however, the Voc obtained demonstrates tandem cell functionality.
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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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Marín, Beloqui José Manuel. "Solution processed inorganic semiconductor solar cells." Doctoral thesis, Universitat Rovira i Virgili, 2015. http://hdl.handle.net/10803/334407.
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En aquesta tesi, l'estudi optoelectrònica i fabricació de diferents solució de processament de semiconductors inorgànics com ara PBS Quantum Dots i cèl·lules solars perovskita s'han fabricat. Al llarg d'aquesta tesi mesuraments optoelectrònics com fotoinducidas càrrega Extracció (PICE), fotoinducidas transitòria fotovoltaje (PIT-PV), fotoinducidas transitòria fotocorriente (PIT-PC) Laser transitòria Espectroscòpia d'Absorció (L-TAS) s'han realitzat a les cèl·lules solars eficients per tal de estudiar els diferents processos elèctrics interns presents en el dispositiu sota condicions de treball.
Usant aquestes tècniques, el desdoblament dels nivells de Fermi s'han trobat per ser l'origen de la tensió en PBS QD cèl·lules solars (Capítol 2).
A més, en el capítol 4.1 d'un estudi optoelectrònic intensiva s'ha realitzat a les cèl·lules solars perovskita mesoporosos, on es van descobrir decaïments biexponenciales de TPV i càrrega diferencial es va proposar manera tan adequada per obtenir la càrrega generada en el dispositiu.
D'altra banda, els dispositius van ser fabricats utilitzant diferents polímers com HTM, i els resultats proporcionats van confirmar que la regeneració va ser superior al 90%, i que PIT-PV realitzat en condicions de foscor corresponen a la recombinació entre els orificis de la HTM i els electrons en el TiO2, com presentat en el capítol 4.2.
A més, els resultats presentats en el capítol 4.3 mostrar que una capa de Al2O3 monoatòmic alentir el recombinació en el dispositiu d'augment de la tensió del dispositiu.En esta tesis, el estudio optoelectrónico y la fabricación de diferentes solución de procesado de semiconductores inorgánicos tales como PbS Quantum Dots y células solares de perovskita se han fabricado. A lo largo de esta tesis medidas optoelectrónicos como fotoinducidas carga Extracción (PICE), fotoinducidas transitoria fotovoltaje (PIT-PV), fotoinducidas transitoria fotocorriente (PIT-PC) Laser transitoria Espectroscopia de Absorción (L-TAS) se han realizado a las células solares eficientes con el fin de estudiar los diferentes procesos eléctricos internos presentes en el dispositivo bajo condiciones de trabajo. Usando estas técnicas, el desdoblamiento de los niveles de Fermi ha sido encontrado como el origen de la tensión en PbS QD células solares (Capítulo 2). Además, en el capítulo 4.1 de un estudio optoelectrónico intensiva se ha realizado a las células solares perovskita mesoporosos, donde se descubrieron decaimientos biexponenciales de TPV y carga diferencial se propuso manera tan adecuada para obtener la carga generada en el dispositivo. Por otra parte, los dispositivos fueron fabricados utilizando diferentes polímeros como HTM, y los resultados proporcionados confirmaron que la regeneración fue superior al 90%, y que PIT-PV realizado en condiciones de oscuridad corresponden a la recombinación entre los huecos de la HTM y los electrones en el TiO2, como presentado en el capítulo 4.2. También, los resultados presentados en el capítulo 4.3 mostraron que una capa de Al2O3 monoatómico ralentiza la recombinación en el dispositivo de aumento de la tensión del dispositivo.
In this thesis, the optoelectronic study and fabrication of different solution processed inorganic semiconductor such as PbS Quantum Dots and perovskite solar cells have been fabricated. Along this thesis optoelectronic measurements such as PhotoInduced Charge Extraction (PICE), PhotoInduced Transient PhotoVoltage (PIT-PV), PhotoInduced Transient PhotoCurrent (PIT-PC) Laser Transient Absorption Spectroscopy (L-TAS) have been performed to efficient solar cells in order to study the different inner electrical processes present in the device under working conditions. Using these techniques, the splitting of Fermi levels have found to be the origin of the voltage in PbS QD solar cells (Chapter 2). Besides, in chapter 4.1 an intensive optoelectronic study has been performed to mesoporous perovskite solar cells, where biexponential decays of TPV were discovered and Differential Charging was proposed as suitable way to obtain the charge generated in the device. Moreover, devices were fabricated using different polymers as HTM, and results provided confirmed that the regeneration was over 90%, and that PIT-PV performed in dark conditions correspond to the recombination between the holes in the HTM and the electrons in the TiO2, as presented in chapter 4.2. Also, results presented in chapter 4.3 showed that a monoatomic layer of Al2O3 slow down the recombination in the device increasing the device voltage..
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Mat-Teridi, Mohd. "Construction of photosensitised semiconductor cathodes." Thesis, Loughborough University, 2012. https://dspace.lboro.ac.uk/2134/10286.
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Recent studies suggest that the performance of dye-sensitised solar cells (DSC) has appeared to have reached a limit, therefore solar cells based on semiconductor materials, such as extremely thin absorber (ETA) solar cells and tandem solar cells are currently the subject of intense research in the framework of low-cost photovoltaic devices as sources of harvesting sunlight to generate electricity. Generally, semiconductor solar cells have been divided into two different types, namely anodic and cathodic type solar cells. Extensive research and development work has been focused on anodic semiconductor sensitised solar cells to date. In contrast, the cathodic semiconductor sensitised solar cells have received no attention which is very surprising. Developing the cathodic semiconductor sensitised solar cell concept is very important in the development of tandem solar cells as well as other new solar cell configurations. The main reason for the lack of research in this area was due to the rarity of p-type semiconductor materials, which made it difficult to find suitable materials to match the energy band edges for cathodic semiconductor sensitised solar cells (CSSC) as well as solid-state cathodic semiconductor solar cells (SS-CSSC). The primary aim of this thesis was to construct cathodic semiconductor sensitised solar cells as well as their solid-state analogues (SS-CSSC). The work conducted within this doctoral study presents state-of-art materials and thin film processing/preparation methods, their characterisation and developing CSSCs and SS-CSSCs employing such films in cascade configurations. No reports have been published in the literature on SS-CSSC to date. The first stage of this thesis is focused on optimising the morphology and the texture (porosity) of the CuI and NiO semiconductor photocathode, by the introduction of new deposition methods namely, pulsed-electrodeposition (PED) and Aerosol-Assisted Deposition (AAD) and Aerosol-Assisted Chemical Vapour Deposition (AACVD). The electrodes prepared by employing the methods mentioned above and controlling the deposition parameters systematically, we have achieved significant improvement in the film morphology and the texture of the deposited films. The resulting electrodes showed excellent improvement in the photoelectrochemical performance which made it suitable for application in construction of both CSSC and SS-CSSC. The photoelectrochemical performance of the electrodes can be seen clearly through the photocurrent density data. For the case of bare CuI, the PEC performance of electrode prepared by the AAD and PED compared against that of continuous-electrodeposition (ED) electrodes. The photocurrent density achieved for the electrodes prepared by AAD and PED was reported around 175 and 75 µAcm-2 respectively which are way higher than the ED case. At the second stage of this study, the work focused on fabrication and characterisation of the CSSCs. Cathodic sensitised PEC solar cells (CuI/Cu2S/(Eu2+/Eu3+) and NiO/Cu2S/(I3-/I-)) were fabricated by deposition of p-Cu2S on the texture controlled CuI and NiO photocathodes. The morphological properties of the photocathode, in particular layer thickness, particle size and film porosity, play an important role in the PEC performance of CSSCs. Optimisation of these parameters led to increased adsorption of the Cu2S light harvester on the photocathode s surface. As a result, the charge injection from Cu2S to the wide band gap photocathode material (CuI and NiO) was significantly improved. Due to this, the CSSC performance showed significant improvement as semiconductor sensitised cathodic solar cells (CSSC). The IPCE and photocurrent density of the CSSC achieved in this study was around (19 and 7 %) and (1 and 0.5 mAcm-2) for the CuI/Cu2S and NiO/Cu2S electrodes respectively. Finally, the SS-CSSC has been fabricated by employing n-Fe2O3 electron transport layer. The construction of SS-CSSC for the first time using the n-Fe2O3 electron transport layer (CuI/Cu2S/Fe2O3 and NiO/Cu2S/Fe2O3) allowed us to study the materials, optical and photoelectrochemical properties of this device. Under AM 1.5 illumination, the SS-CSSC shows a photocurrent density of 6 and 9 µAcm-2 for CuI/Cu2S/Fe2O3 and NiO/Cu2S/Fe2O3 solar cells, respectively. The results of this work indicated low performance for both SS-CSSC compared to CSSC results, due to the lack of adsorption between the absorber and Fe2O3 electrode. However, this study proved the concept of SS-CSSC based on semiconductor material, which is valuable for the future work of cathodic semiconductor sensitised solar cells as well as solid-state tandem solar cells.
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Lian, Zichao. "Photo-Induced Carrier Transfer in Heterostructured Semiconductor Nanocrystals for Solar Energy Conversion." Kyoto University, 2018. http://hdl.handle.net/2433/235053.
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Chang, Jin. "Controlled synthesis of inorganic semiconductor nanocrystals and their applications." Thesis, Queensland University of Technology, 2013. https://eprints.qut.edu.au/63960/1/Jin_Chang_Thesis.pdf.
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This thesis is a comprehensive study of the synthesis of nanomaterials. It explores the synthetic methods on the control of the size, shape and phase of semiconductor nanocrystals. A number of important conclusions, including the mechanism behind crystal growth and the structure-relationship, have been drawn through the experimental and theoretical investigation. The synthesized nanocrystals have been tested for applications in gas sensing, photocatalysis and solar cells, which exhibit considerable commercialization potential.
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Dang, Hongmei. "Nanostructured Semiconductor Device Design in Solar Cells." UKnowledge, 2015. http://uknowledge.uky.edu/ece_etds/77.
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We demonstrate the use of embedded CdS nanowires in improving spectral transmission loss and the low mechanical and electrical robustness of planar CdS window layer and thus enhancing the quantum efficiency and the reliability of the CdS-CdTe solar cells. CdS nanowire window layer enables light transmission gain at 300nm-550nm. A nearly ideal spectral response of quantum efficiency at a wide spectrum range provides an evidence for improving light transmission in the window layer and enhancing absorption and carrier generation in absorber. Nanowire CdS/CdTe solar cells with Cu/graphite/silver paste as back contacts, on SnO2/ITO-soda lime glass substrates, yield the highest efficiency of 12% in nanostructured CdS-CdTe solar cells. Reliability is improved by approximately 3 times over the cells with the traditional planar CdS counterpart. Junction transport mechanisms are delineated for advancing the basic understanding of device physics at the interface. Our results prove the efficacy of this nanowire approach for enhancing the quantum efficiency and the reliability in window-absorber type solar cells (CdS-CdTe, CdS-CIGS and CdS-CZTSSe etc) and other optoelectronic devices.
We further introduce MoO3-x as a transparent, low barrier back contact. We design nanowire CdS-CdTe solar cells on flexible foils of metals in a superstrate device structure, which makes low-cost roll-to-roll manufacturing process feasible and greatly reduces the complexity of fabrication. The MoO3 layer reduces the valence band offset relative to the CdTe, and creates improved cell performance. Annealing as-deposited MoO3 in N2 reduces series resistance from 9.98 Ω/cm2 to 7.72 Ω/cm2, and hence efficiency of the nanowire solar cell is improved from 9.9% to 11%, which efficiency comparable to efficiency of planar counterparts. When the nanowire solar cell is illuminated from MoO3-x /Au side, it yields an efficiency of 8.7%. This reduction in efficiency is attributed to decrease in Jsc from 25.5mA/cm2 to 21mA/cm2 due to light transmission loss in the MoO3-x /Au electrode. Even though these nanowire solar cells, when illuminated from back side exhibit better performance than that of nanopillar CdS-CdTe solar cells, further development of transparent back contacts of CdTe could enable a low-cost roll-to-roll fabrication process for the superstrate structure-nanowire solar cells on Al foil substrate.
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CAPITANI, CHIARA. "Synthesis of semiconductor colloidal nanocrystals with large Stokes-shift for luminescent solar concentrators." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2022. http://hdl.handle.net/10281/366195.
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I concentratori solari luminescenti (LSCs) sono delle guide d’onda composti da una matrice polimerica drogata o ricoperta con fluorofori. La luce solare diretta e/o diffusa che penetra nella matrice è assorbita dai fluorofori e poi riemessa dagli stessi con energia minore. La luce emessa, grazie alla riflessione totale interna, propaga fino a raggiungere i bordi della guida d’onda dove è convertita in elettricità da celle fotovoltaiche poste sul perimetro della matrice.
L’efficienza del dispositivo è ridotta da numerosi processi di perdita, sia dovuti alla riflessione della matrice e al cono di fuga, sia quelli che dipendono dalle caratteristiche dei fluorofori, come il coefficiente di assorbimento, il quantum yield (QY) di fotoluminescenza (PL) e il riassorbimento.
Per minimizzare tali perdite, una buona alternativa ai tradizionali fluorofori sono i quantum dots (QDs) colloidali che presentano solitamente un elevato QY, un alto coefficiente di assorbimento e una lunghezza d’onda di emissione controllabile cambiando le dimensioni dei nanocristalli tramite modifiche dei parametri di sintesi. Inoltre, ingegnerizzando opportunamente i QDs, è possibile realizzare particelle con elevato Stokes-shift tra gli spettri di assorbimento ed emissione, in modo da ridurre quanto più possibile il riassorbimento.
Il progetto si è quindi focalizzato sullo sviluppo della sintesi di QDs, al fine di ottimizzare il QY di fotoluminescenza, la compatibilizzazione con la matrice polimerica e la fotostabilità, limitando comunque il riassorbimento.
Inoltre. la procedura di sintesi deve essere facilmente trasportabile su volumi industriali, per soddisfare il fabbisogno di produzioni di elevati metri quadrati di LSCs.
Durante i tre anni di progetto di dottorato in Alto Apprendistato ho potuto sviluppare una procedura di sintesi che consiste in quattro step:
• crescita di nanocristalli di CuInS2 core;
• formazione del quaternario tramite aggiunta di zinco (ZnCuInS2); passaggio cruciale per aumentare il QY e controllare la lunghezza d’onda di emissione;
• crescita di una shell di solfuro di zinco (ZnCuINS2/ZnS) per passivare la superficie dei nanocristalli, aumentare il QY e la fotostabilità;
• trattamento post sintesi di scambio di leganti parziale per migliorare la solubilità nella matrice polimerica.
I nanocristalli così prodotti mostrano un QY del 60% ed un’ottima solubilità nella matrice polimerica. Infatti, è stato prodotto un LSC di grande dimensione (30 cm x 30 cm x 0.7 cm) la cui optical power efficiency, OPE = 6.8%.
Inizialmente ho sviluppato la procedura di sintesi in un pallone di vetro da 25 mL, producendo 250 mg a sintesi. Grazie all’attrezzatura fornita da Glass to Power S.p.A ho potuto studiare lo scale-up della sintesi. Dapprima ho effettuato studi preliminare, per approfondire alcune possibili problematiche dovute all’aumento dei volumi, su palloni di maggiori dimensioni, 500 mL e 2 L. Analizzate e risolte le tematiche di riscaldamento e stop della sintesi ho effettuato sintesi in un reattore preindustriale producendo 300 g di nanocristalli di ZnCuINS2/ZnS.
Oltre ad incrementare la produzione di sintesi da 250 mg a 300 g mi sono occupata dell’ottimizzazione della procedura di sintesi. Ho testato diverse strategie per incrementare il QY senza danneggiare la solubilità nel polimero. Grazie ad una variazione di reagente nel secondo step e ad un incremento dei layer della shell ho ottenuto nanocristalli con 80% di QY.
Il prossimo step sarà effettuare lo scale-up di questa nuova procedura e produrre LSC di grandi dimensioni.
Grazie alle collaborazioni con altri studenti di dottorato ho sintetizzato nanocristalli di calcogenuro drogati oro e opportunamente decorati con molecole coniugate per sistemi di up-conversion. Grazie all’introduzione dell’oro in questi sistemi si è ottenuta un’efficienza di up-conversion del 12%.Luminescent solar concentrators (LSCs) are waveguides composed of a polymeric matrix doped or coated with fluorophores. The direct and/or diffuse sunlight that penetrates the matrix is absorbed by the fluorophores and then re-emitted by them with less energy. The light emitted, thanks to the total internal reflection, propagates until it reaches the edges of the wave guide where it is converted into electricity by photovoltaic cells placed on the perimeter of the matrix. The efficiency of the device is reduced by numerous loss processes, due to the reflection of the matrix and the escape cone, and/or due to the characteristics of the fluorophores, such as the absorption coefficient, the quantum yield (QY) of photoluminescence (PL) and the reabsorption. To minimize losses due to fluorophores, a good alternative are colloidal quantum dots (QDs) that usually have a high QY, a high absorption coefficient and a controllable emission wavelength by changing the size of the nanocrystals. Furthermore, by properly engineering the QDs, it is possible to realize particles with high Stokes-shift between the absorption and emission spectra, in order to reduce the reabsorption as much as possible. The project is focused on the development of the synthesis of QDs, in order to optimize the QY of photoluminescence, compatibility with the polymer matrix and photostability, while limiting the reabsorption. Besides. the synthesis procedure must be easily transferable on industrial volumes, to meet the production needs of high square meters of LSCs. During the three years of the doctoral project in High Apprenticeship I was able to develop a synthesis procedure consisting of four steps: • growth of CuInS2 core nanocrystals; • quaternary formation with zinc addition (ZnCuInS2); crucial step to increase the QY and control the emission wavelength; • growth of a zinc sulphide shell (ZnCuInS2/ZnS) to passivate the surface of nanocrystals, increase QY and photostability; • post-synthesis treatment of the partial exchange of ligands to improve solubility in the polymer matrix. The nanocrystals thus produced show 60% QY and excellent solubility in the polymer matrix. In fact, a large size LSC (30 cm x 30 cm x 0.7 cm) was produced, whose optical power efficiency, OPE = 6.8%. Initially, I developed the synthesis procedure in a 25 ml glass flask, producing 250 mg for batch. Thanks to the equipment provided by Glass to Power s.p.A I was able to study the increase in the scale of the synthesis. Firstly, in order to investigate some possible problems due to the increase in volumes, I have carried out preliminary studies on larger balloons, 500 mL and 2 L. After analysis of heating and quenching of synthesis, I have performed the synthesis in a preindustrial reactor producing 300 g of nanocrystals of ZnCuInS2/ZnS. In addition I also optimized the synthesis procedure. I tested several strategies to increase QY without damaging solubility in the polymer. Thanks to a variation of the reagent in the second step and an increase of the shell layers, I obtained nanocrystals with 80% of QY. The next step will be to scale up this new procedure and produce large LSCs. I collaborated with other PhD students, in particular, I synthesized with a heat-up method CdSe nanocrystals doped with Au7 clusters and decorated with conjugated dyes as efficient triplet sensitizers or up-conversion applications (gold doping improves up-conversion efficiency). The beneficial effects of the doping strategy result in a maximum UC efficiency of 12%, which is an unprecedented result for up-conversion based on decorated NCs as triplet sensitizers.
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Liang, Xinxing. "Synthesis of perovskite nanocrystals and their applications in perovskite solar cells." Thesis, University of Bath, 2018. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.767584.
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Perovskite solar cells are a very promising photovoltaic technology which was first reported in 2009 and developed very rapidly. The crystallisation within perovskite films is highly dependent on processing environments, such as temperature, humidity, atmosphere, even light, which makes the fabrication of perovskite solar cells rather lab-dependent and poorly reproducible. One strategy to overcome this problem is to develop a controlled synthesis of perovskite nanocrystals which can then be ordered into films in a separatestep. In this thesis, optimisation of planar perovskite solar cells is carried out by the engineering of perovskite film fabrication methods. Different deposition methods along with different process factors such as solvents, temperature and precursor recipes are compared. One step spin-coating method with the recipe of MAI:PbCl2=3:1 gives the best PCE of 12.1 ± 0.7 % in air with controlled humidity of < 35%, showing high reliability and reproducibility. Doping of TiO2 layers with Zn2+, Sn4+ and Nb5+ ions are carried out to investigate the impacts of doping ions in different valence states on the electron-transporting properties of TiO2 ETLs. The different doping ions shift the flat band potential differently. Zn2+ largely negatively shifts the flat band potential, whereas Nb5+ positively shifts and Sn4+ barely changes the flat band potential of TiO2. the Zn-doping of the TiO2 ETL decreases the performance of the cells. However, when a thin layer of Zn-doped TiO2 is deposited on top of the pristine TiO2 layer as interlayer, the cell efficiency is slightly improved. Following the cell optimisation, to achieve better control over the crystallisation process, a facile flow reactor is developed for the synthesis of MAPbX3 perovskite nanocrystals at low temperature, which are further used for perovskite solar cells. The nanocrystals show narrow size distribution, good emissive properties and high stability. The bandgap of the nanocrystals was easily tuned between 485-745 nm by changing the halide composition. The photoluminescence of the MAPbI3 NCs in the first supernatant can also be tuned by changing the process parameters such as temperature, residence time and ligand concentration. However the impacts are more complex in the second supernatant in toluene with the appearance of multiple peaks in the PL spectra. It could be resultedfrom the formation of smaller NCs due to the reprecipitation of the incompletely removed reactants when added into toluene, or the fragmentation of the NCs upon dispersion into toluene, but better understanding is still needed. In the last part of the thesis, the synthesised MAPbI3 nanocrystals are investigated in perovskite solar cell applications. They have been applied as interlayers at the perovskite HTM interface, where they improved the stability of the devices towards moisture. The nanocrystals and their bulk by-products are also used as active light-absorbing layers for perovskite solar cells, delivering the best PCEs of 0.51% and 1.2% respectively, and notably showing outstanding water resistance. Further improvements in the cell performance could potentially be achieved by the removal of the insulating long chain ligands using effective ligand exchange treatments.
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Косяк, Володимир Володимирович, Владимир Владимирович Косяк, Volodymyr Volodymyrovych Kosiak, Анатолій Сергійович Опанасюк, Анатолий Сергеевич Опанасюк, Anatolii Serhiiovych Opanasiuk, Юрій Павлович Гнатенко, et al. "Ternary semiconductor thin films for solar cells application." Thesis, Lublin University of Technology, 2011. http://essuir.sumdu.edu.ua/handle/123456789/30140.
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The Cd1-xMnxTe semiconductor compound is a promising material for hetero-junction
thin films solar cells application [1]. But physical properties (optical, structural and
electrophysical) of polycrystalline Cd1-xMnxTe thin films are not studied well. However
these properties have strong effect on thin films performance. Therefore the main task of
this research is to study the main physical properties of Cd1-xMnxTe thin films obtained at
different growth condition.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/30140
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Mitra, Somak. "Nanoscale engineering for the integration of silicon nanocrystals in solar cells nanoarchitectures." Thesis, Ulster University, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.629076.
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One of the main contributions of this thesis is the improvement on the overall performance of the solar cells due to the impact of the surface engineering of silicon nanocrystals (SiNCs) and also down conversion of high energy photons by SiNCs. It is demonstrated that surface engineering techniques by using microplasma processing improve the capabilities of the SiNCs for different opto-electronic applications and in particular for solar cells. Surface engineering of SiNCs in water shows long term stability, which could allow the deployment of SiNCs for a wider range of applications. Microplasma-induce liquid chemistry on SiNCs in ethanol and water shows very unique surface properties which are not achievable by other techniques. The optical and electronic properties of SiNCs/polymer colloid and nanocomposites have been analyzed. It has been found that microplasma processed SiNCs/polymer nanocomposite shows improved optical properties and also exhibits enhanced photogeneration and conductivity. This thesis is focused on the application of SiNCs in photovoltaic devices. Hybrid bulk heterojunction solar cells and SiNCs-Schottkey barrier photo voltaic devices have been developed. Hybrid bulk heterojunction solar cells have polymers and SiNCs as an active layer. A range of different device structures have been produced and investigated with support from current-voltage characteristics, which contributed to identify band alignment and the suitability of the architectures for the solar cells. The results also explain the limitations of the solar cells due to either dissociation and/or transport properties. SiNCs based nanocomposites are being employed as an optical converter first time in organic solar cell. SiNCs/polymer nanocomposite allows down conversion of high energy photons demonstrating a drastic improvement in solar cell efficiency with concentrated light.
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Harries, Joanna Elizabeth. "Semiconductor nanoparticle sensitization of solid state nanocrystalline solar cells." Thesis, University of Bath, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.438648.
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Eskandari, Rahmatollah. "Ferroelectric-Semiconductor Systems for New Generation of Solar Cells." ScholarWorks@UNO, 2017. http://scholarworks.uno.edu/td/2318.
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This dissertation includes two parts. In the first part the study is focused on the fabrication of multifunctional thin films for photovoltaic applications. There is no doubt about the importance of transforming world reliance from traditional energy resources, mainly fossil fuel, into renewable energies. Photovoltaic section still owns very small portion of the production, despite its fast growth and vast research investments. New methods and concepts are proposed in order to improve the efficiency of traditional solar cells or introduce new platforms. Recently, ferroelectric photovoltaics have gained interest among researchers. First objective in application of ferroelectric material is to utilize its large electric field as a replacement for or improvement of built-in electric field in semiconductor p-n junctions which is responsible for the separation of generated electron-hole pairs. Increase in built in electric field will increase open-circuit voltage of the solar cell.
In this regard, thin films of ferroelectric hafnium dioxide doped with silicon have been fabricated using physical vapor deposition techniques. Scanning probe microscopy techniques (PFM and KPFM) have been employed to analyze ferroelectric response and surface potential of the sample. The effects of poling direction of the ferroelectric film on the surface potential and current-voltage characteristics of the cell have been investigated. The results showed that the direction of poling affects photoresponse of the cell and based on the direction it can either improved or diminished.
In the second part of this work, epitaxial thin films have been synthesized with physical vapor deposition techniques such as sputtering and electron beam evaporation for the ultimate goal of producing multifunctional three-dimensional structures. Three-dimensional structures have been used for applications such as magnetic sensors, filters, micro-robots and can be used for modification of the surface of solar cells in order to improve light absorption and efficiency. One of the important techniques for producing 3-D structures is using origami techniques. The effectiveness of this technique depends on the control of parameters which define direction of bending and rolling of the film or curvature of the structure based on the residual stress in the structure after film’s release and on the quality and uniformity of the film. In epitaxially grown films, the magnitude and direction of the stress are optimized, so the control over direction of rolling or bending of the film can be controlled more accurately. For this purpose, deposition conditions for epitaxy of Zn, Fe, Ru, Ti, NaCl and Cr on Si, Al2O3 or MgO substrates have been investigated and optimized. Crystallinity, composition and morphology of the films were characterized using reflective high energy diffraction (RHEED), Auger electron spectroscopy (AES), energy dispersive X-ray (EDX), and scanning electron microscopy (SEM).
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Lefrançois, Aurélie. "Synthèse de nanocristaux de type Chalcopyrite en vue d'applications en cellules solaires." Phd thesis, Université de Grenoble, 2013. http://tel.archives-ouvertes.fr/tel-01062176.
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Cette thèse porte sur l'étude de nanocristaux semi-conducteurs ternaires, et leur application dansdes cellules solaires hybrides organiques/inorganiques. Les nanocristaux semi-conducteurs absorbentla lumière à des longueurs d'ondes déterminées par leur taille et leur composition, et conduisent lescharges électriques. Ils sont stables en solution, ce qui permet un dépôt de couches minces à bascout. Aujourd'hui les meilleurs rendements en cellules solaires hybrides sont obtenus à partir de nanocristauxbinaires contenant soit du plomb, soit du cadmium. Les nanocristaux ternaires conserventles propriétés particulières des nanocristaux binaires tout en permettant de s'affranchir des élémentstoxiques. Cependant, leur synthèse reste à optimiser pour contrôler de leur structure cristalline et leurcomposition.Nous avons réalisé, par voie chimique, la synthèse de nanocristaux de CuInS2 de taille et de compositioncontrôlées. En suivant in situ la synthèse de ces nanocristaux par diffraction des rayons X sous rayonnementsynchrotron nous avons trouvé que les précurseurs s'organisent avant nucléation sous forme deplans espacés par deux longueurs du ligand utilisé (ici dodécanethiol, DDT). Cela impacte nucléationet croissance des nanocristaux. Les ligands stabilisent les nanocristaux en solution colloïdale, maisleur caractère isolant peut inhiber le transfert et le transport de charges. Le remplacement du ligandd'origine (DDT) par un ligand plus court, l'éthylhexanethiol (EHT), modifie les niveaux d'énergie etpermet d'augmenter la conductivité des films de nanocristaux. Nous avons intégré des nanocristauxde CuInS2 entourés d'EHT dans des cellules hybrides constituées d'un polymère conjugué (P3HT) etd'un fullerène (PCBM). L'efficacité des cellules solaires contenant des nanocristaux entourés d'EHTest significativement améliorée par rapport à celle des cellules de P3HT :PCBM réalisées dans lesmêmes conditions. Le transfert et la mobilité des charges sont étudiés par RPE sous éclairement etphoto-CELIV respectivement. De ces études il ressort que l'amélioration des cellules provient d'unemeilleure génération et dissociation des charges.
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Miao, Yinghong. "Nanocrystalline titanium dioxide solar cells sensitized with germanium quantum dots." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 73 p, 2008. http://proquest.umi.com/pqdweb?did=1597633711&sid=14&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Noel, Nakita K. "Advances in hybrid solar cells : from dye-sensitised to perovskite solar cells." Thesis, University of Oxford, 2014. https://ora.ox.ac.uk/objects/uuid:e0f54943-546a-49cd-8fd9-5ff07ec7bf0a.
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This thesis presents a study of hybrid solar cells, specifically looking at various methods which can be employed in order to increase the power conversion efficiency of these devices. The experiments and results contained herein also present a very accurate picture of how rapidly the field of hybrid solar cells has progressed within the past three years. Chapters 1 and 2 present the background and motivation for the investigations undertaken, as well as the relevant theory underpinning solar cell operation. Chapter 2 also gives a brief review of the literature pertinent to the main types of devices investigated in this thesis; dye-sensitised solar cells, semiconductor sensitized solar cells and perovskite solar cells. Descriptions of the synthetic procedures, as well as the details of device fabrication and any measurement techniques used are outlined in Chapter 3. The first set of experimental results is presented in Chapter 4. This chapter outlines the synthesis of mesoporous single crystals (MSCs) of anatase TiO2 as well as an investigation of its electronic properties. Having shown that this material has superior electronic properties to the conventionally used nanoparticle films, they were then integrated into low temperature processed dye-sensitised solar cells and achieved power conversion efficiencies of > 3%, exhibiting electron transport rates which were orders of magnitude higher than those obtained for the high temperature processed control films. Chapter 5 further investigates the use of MSCs in photovoltaic devices, this time utilising a more strongly absorbing inorganic sensitiser, Sb2S3. Utilising the readily tunable pore size of MSCs, these Sb2S3 devices showed an increase in voltage and fill factor which can be attributed to a decrease in recombination within these devices. This chapter also presents the use of Sb2S3 in the meso-superstructured configuration. This device architecture showed consistently higher voltages suggesting that in this architecture, charge transport occurs through the absorber and not the mesoporous scaffold. Chapters 6 and 7 focus on the use of hybrid organic-inorganic perovskites in photovoltaic devices. In Chapter 6 the mixed halide, lead-based perovskite, CH3NH3PbI3-xClx is employed in a planar heterojunction device architecture. The effects of Lewis base passivation on this material are investigated by determining the photoluminescence (PL) lifetimes and quantum efficiencies of treated and untreated films. It is found that passivating films of this material using Lewis bases causes an increase in the PLQE at low fluences as well as increasing the PL lifetime. By globally fitting these results to a model the trap densities are extracted and it is found that using these surface treatments decreases the trap density of the perovskite films. Finally, these treatments are used in complete solar cells resulting in increased power conversion efficiencies and an improvement in the stabilised power output of the devices. Chapter 7 describes the materials synthesis and characterisation of the tin-based perovskite CH3NH3SnI3 and presents the first operational, lead-free perovskite solar cell. The work presented in this thesis describes significant advances in the field of hybrid solar cells, specifically with regards to improvements made to the nanostructured electrode, and the development and implementation of more highly absorbing sensitizers. The improvements discussed here will prove to be quite important in the drive towards exploiting solar power as a clean, affordable source of energy.
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Chern, Kevin Tsun-Jen. "GaInN/GaN Schottky Barrier Solar Cells." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/52899.
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GaInN has the potential to revolutionize the solar cell industry, enabling higher efficiency solar cells with its wide bandgap range spanning the entire solar spectrum. However, material quality issues stemming from the large lattice mismatch between its binary endpoints and questionable range of p-type doping has thus far prevented realization of high efficiency solar cells. Nonetheless, amorphous and multi-crystalline forms of GaInN have been theorized to exhibit a defect-free bandgap, enabling GaInN alloys at any indium composition to be realized. But the range of possible p-type doping has not yet been determined and no device quality material has been demonstrated thus far. Nonetheless, a Schottky barrier design (to bypass the p-type doping issue) on single-crystal GaInN can be used to provide some insight into the future of amorphous and micro-crystalline GaInN Schottky barrier solar cells. Through demonstration of a functional single crystalline GaInN Schottky barrier solar cell and comparison of the results to the best published reports for more conventional p-i-n GaInN solar cells, this work aims to establish the feasibility of amorphous and multi-crystalline GaInN solar cells.Ph. D.
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Tachibana, Yasuhiro. "Charge separation and recombination in dye sensitised semiconductor solar cells." Thesis, Imperial College London, 2000. http://hdl.handle.net/10044/1/8787.
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Smith, Thomas. "Studies of p-type semiconductor photoelectrodes for tandem solar cells." Thesis, Loughborough University, 2014. https://dspace.lboro.ac.uk/2134/14522.
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Photoelectrodes and photovoltaic devices have been prepared via multiple thin film deposition methods. Aerosol assisted chemical vapour deposition (AACVD), electrodeposition (ED), chemical bath deposition (CBD) and doctor blade technique (DB) have been used to deposit binary and ternary metal oxide films on FTO glass substrates. The prepared thin films were characterised by a combination of SEM (Scanning Electron Microscopy), powder X-ray diffraction, mechanical strength tests and photochemical measurements. Nickel oxide (NiO) thin films prepared by AACVD were determined to have good mechanical strength . with a photocurrent of 7.6 μA cm-2 at 0 V and an onset potential of about 0.10 V. This contrasted with the dark current density of 0.3 μA cm-2 at 0 V. These NiO samples have very high porosity with crystalline columns evidenced by SEM. In comparison with the AACVD methodology, NiO films prepared using a combination of ED and DB show good mechanical strength but a higher photocurrent of 24 μA cm-2 at 0 V and an onset potential of about 0.10 V with a significantly greater dark current density of 7 μA cm-2 at 0 V. The characteristic features shown in the SEM are smaller pores compared to the AACVD method. Copper (II) oxide (CuO) and copper (I) oxide (Cu2O) films were fabricated by AACVD by varying the annealing temperature between 100-325°C in air using a fixed annealing time of 30 min. It was shown by photocurrent density (J-V) measurements that CuO produced at 325 °C was most stable and provided the highest photocurrent of 173 μA cm-2 at 0 V with an onset potential of about 0.23 V. The alignment of zinc oxide (ZnO) nano-rods and nano-tubes fabricated by CBD have been shown to be strongly affected by the seed layer on the FTO substrate. SEM images showed that AACVD provided the best seed layer for aligning the growth of the nano-rods perpendicular to the surface. Nano-rods were successfully altered into nano-tubes using a potassium chloride bath etching method. NiO prepared by both AACVD and the combined ED/DB method were sensitized to absorb more of the solar spectrum using AACVD to deposit CuO over the NiO. A large increase in the photocurrent was observed for the p-type photoelectrode. These p-type photoelectrode showed a photocurrent density of approximately 100 μA cm-2 at 0 V and an onset potential of 0.3 V. This photocathode was then used as a base to produce a solid state p-type solar cell. For the construction of the solid state solar cells several n-type semiconductors were used, these were ZnO, WO3 and BiVO4. WO3 and BiVO4 were successfully produced with BiVO4 proving to be the optimum choice. This cell was then studied more in depth and optimised by controlling the thickness of each layer and annealing temperatures. The best solid state solar cell produced had a Jsc of 0.541 μA cm-2 (541 nA) and a Voc of 0.14 V, TX146 made up of NiO 20 min, CuFe2O4 50 min, CuO 10 min, BiVO4 27 min, using AACVD and then annealed for 30 min at 600°C.
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Berhe, Seare Ahferom. "Acceptor-sensitizers for Nanostructured Oxide Semiconductor in Excitonic Solar Cells." Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc699927/.
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Organic dyes are examined in photoelectrochemical systems wherein they engage in thermal (rather than photoexcited) electron donation into metal oxide semiconductors. These studies are intended to elucidate fundamental parameters of electron transfer in photoelectrochemical cells. Development of novel methods for the structure/property tuning of electroactive dyes and the preparation of nanostructured semiconductors have also been discovered in the course of the presented work. Acceptor sensitized polymer oxide solar cell devices were assembled and the impact of the acceptor dyes were studied. The optoelectronic tuning of boron-chelated azadipyrromethene dyes has been explored by the substitution of carbon substituents in place of fluoride atoms at boron. Stability of singlet exited state and level of reduction potential of these series of aza-BODIPY coumpounds were studied in order to employ them as electron-accepting sensitizers in solid state dye sensitized solar cells.
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Shen, Zhangfeng. "Engineering Carbon-Semiconductor Hybrid Materials for Photocatalysis and Solar Cells." Thesis, Curtin University, 2017. http://hdl.handle.net/20.500.11937/66005.
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Carbon-semiconductor hybrid materials (CSHMs) are promising candidates for solar energy conversion because of their enhanced light harvesting ability and the prolonged charge carrier separation. In this thesis, a series of CSHMs has been successfully fabricated and applied in photocatalysis and dye-sensitized solar cells. The aim of this thesis is to develop cost-effective methods to prepare CSHMs with appropriate morphologies, compositions, and interfacial contact to promote the efficiency of photocatalysis and solar energy conversion.
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Unger, Eva. "XDSC : Excitonic Dye Solar Cells." Doctoral thesis, Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-168608.
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Solar energy is the foremost power source of our planet. Driving photosynthesis on our planet for 3 billion years the energy stored in the form of fossil fuels also originates from the sun. Consumption of fossil fuels to generate energy is accompanied with CO2 emission which affects the earth's climate in a serious manner. Therefore, alternative ways of converting energy have to be found. Solar cells convert sunlight directly into electricity and are therefore an important technology for future electricity generation. In this work solar cells based on the inorganic semiconductor titanium dioxide and hole-transporting dyes are investigated. These type of solar cells are categorized as hybrid solar cells and are conceptually related to both dye-sensitized solar cells and organic solar cells. Light absorption in the bulk of the hole-transporting dye layer leads to the formation of excitons that can be harvested at the organic/inorganic interface. Two design approaches were investigated: 1) utilizing a multilayer of a hole-transporting dye and 2) utilizing a hole-transporting dye as light harvesting antenna to another dye which is bound to the titanium dioxide surface. Using a multiple dye layer in titanium dioxide/hole transporting dye devices, leads to an improved device performance as light harvested in the consecutive dye layers can contribute to the photocurrent. In devices using both an inteface-bound dye and a hole-transporting dye, excitation energy can be transferred from the hole-transporting dye to the interface dye.
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Akgul, M. Zafer. "Environmentally friendly nanocrystals synthesized and processed in ambient conditions for solution-processed solar cells." Doctoral thesis, Universitat Politècnica de Catalunya, 2021. http://hdl.handle.net/10803/671521.
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Due to the continuously increasing energy demand and the environmental concerns about climate changes raised by international community, alternative energy resources have been put under intense investigation for the past decade. As a consequence, different technologies have been proposed, photovoltaics being a promising one among them. Till now, different structures and methods have been employed to fabricate photovoltaics for energy production. Traditionally, vacuum-based deposition methods have been used to form the stacks required for proper photovoltaic operation. Triggered by the advancements in colloidal synthesis methods, thin films of colloidal semiconductor nanocrystals (CNCs) have gained tremendous attention as cheap substitutes for vacuum-deposited layers. Up to date, various colloidal synthesis methods have been developed to produce semiconductor nanocrystals for applications in photovoltaics. Thanks to the high degree of controllability and high material quality, hot injection methods have been the way-to-go for the past decades. However, the application of CNC films in large-scale photovoltaics has been delayed due to the synthesis constraints originating from hot injection methods itself.
In this work, we demonstrate that it is possible to eliminate the need for air-free techniques by careful selection of the precursors and oxygen-aware design of reaction conditions. We use the semiconducting compound silver bismuth sulfide (AgBiS2) as the prototype material to demonstrate the easiness and efficiency of the method. This semiconducting compound is selected as the prototype material thanks to its attractive optical properties for photovoltaics and the environmentally friendly nature of the constituent elements. Solar cells fabricated using CNCs synthesized at room temperature have yielded a power conversion efficiency of 5.5 %, demonstrating the promising potential of the method. The application of the method in the synthesis of AgBiS2 CNCs results in a cost reduction of at least 60 % compared to the previous studies reporting similar photovoltaics-grade AgBiS2 CNCs. Another important challenge in employing hot injection methods is the scalability. Due to the difficulties in maintaining the thermal fluctuations within the reaction volume low and in the maintenance of inert atmosphere inside the reaction vessel, hot injection methods impose an inherent scale constraint on the synthesis. On the other hand, with the elimination of scale constraint by the use of an ambient condition synthesis method, the requirement for high temperature reaction and chemically inert reaction environment is eliminated, enabling us to achieve large-scale volume production of CNCs. This, in turn, can lower the production cost of CNCs further, hence the cost of photovoltaics that are based on CNCs. In addition, we show that the ambient condition method can be adapted for the synthesis of another metal chalcogenide, namely silver bismuth selenide CNCs (AgBiSe2) with an extended absorption spectrum further into the near infrared down to ~ 0.9 eV. The resulting AgBiSe2 CNC solar cells achieved a preliminary efficiency up to 2.6 %. Also, thanks to the structural similarity of these two compounds, the two methods that are developed for the synthesis of AgBiS2 and AgBiSe2 CNCs are combined and optimized to obtain alloyed quaternary AgBiSSe CNCs as a facile means of bandgap tuning in silver bismuth chalcogenide semiconductor family. The formation of AgBiSSe CNCs are verified through optical and structural characterization methods to show the formation of quaternary phase and also the phase purity of the obtained product. Overall, it is shown that the proposed ambient condition synthesis method is capable of providing photovoltaics-grade RoHS-compliant materials at a lower cost and higher throughput compared to the hot-injection based methods, opening a novel way for low-cost environmentally friendly photovoltaics.Debido al continuo aumento de la demanda de energía y las preocupaciones ambientales sobre el cambio climático planteadas por la comunidad internacional, los recursos energéticos alternativos han sido objeto de una intensa investigación durante la última década. Como consecuencia, se han propuesto diferentes tecnologías, siendo la fotovoltaica una prometedora entre ellas. Hasta ahora, se han empleado diferentes estructuras y métodos para fabricar células solares para la producción de energía. Tradicionalmente, se han utilizado métodos de deposición basados en vacío para formar las capas necesarias para el funcionamiento fotovoltaico adecuado. Debido a los avances en los métodos de síntesis coloidal, las películas finas de nanocristales semiconductores en solución coloidal (CNCs) han ganado una gran atención como sustitutos baratos de las capas depositadas al vacío. Hasta la fecha, se han desarrollado varios métodos de síntesis coloidal para producir nanocristales semiconductores para aplicaciones en energía fotovoltaica. Gracias al alto grado de controlabilidad y la alta calidad del material, los métodos de inyección en caliente han sido el camino a seguir durante las últimas décadas. Sin embargo, la aplicación de películas de CNCs en fotovoltaica a gran escala se ha retrasado debido a las propias limitaciones de estos métodos de síntesis. En este trabajo, demostramos que es posible eliminar la necesidad de técnicas inertes mediante la selección cuidadosa de los precursores y el diseño de las condiciones de reacción conscientes del oxígeno. Usamos el compuesto semiconductor sulfuro de bismuto y plata (AgBiS2) como material prototipo para demostrar la facilidad y eficiencia del método. Este compuesto semiconductor se ha seleccionado como material prototipo gracias a sus atractivas propiedades ópticas para la energía fotovoltaica y la naturaleza ecológica de los elementos constituyentes. Las células solares fabricadas con CNCs sintetizadas a temperatura ambiente han arrojado una eficiencia de conversión de energía del 5,5 %, lo que demuestra el potencial prometedor del método. La aplicación del método en la síntesis de CNCs de AgBiS2 da como resultado una reducción de costes de al menos un 60 % en comparación con los estudios anteriores que reportaron CNCs de AgBiS2 de una calidad fotovoltaica similar. Otro desafío importante al emplear métodos de inyección en caliente es la escalabilidad. Debido a las dificultades para mantener bajas las fluctuaciones térmicas y la atmósfera inerte dentro del recipiente de reacción, los métodos de inyección en caliente imponen una restricción de escala inherente a la síntesis. Por otro lado, con la eliminación de la restricción de escala mediante el uso de un método de síntesis en condiciones ambientales, se elimina también el requisito de reacción a alta temperatura y entorno de reacción químicamente inerte, lo que nos permite lograr una producción en volumen a gran escala de CNCs. Esto, a su vez, puede reducir aún más el coste de producción de los CNCs, y en consecuencía el coste de las células fotovoltaicas que se basan en CNCs. Además, mostramos que el método en condiciones ambientales se puede adaptar para la síntesis de otro calcogenuro metálico, por ejemplo, CNCs de seleniuro de bismuto y plata (AgBiSe2) con un espectro de absorción más extendido en el infrarrojo cercano, hasta ~ 0.9 eV . Las células solares de CNCs de AgBiSe2 alcanzaron una eficiencia preliminar de hasta el 2,6 %. Además, gracias a la similitud estructural de estos dos compuestos, los dos métodos desarrollados para la síntesis de CNCs de AgBiS2 y AgBiSe2 se combinan y optimizan para obtener CNCs de la aleación cuaternaria AgBiSSe como un medio fácil de sintonización de bandgap en familia de semiconductores de calcogenuro de bismuto y plata.La formación de AgBiSSe CNCs se verifica mediante métodos de caracterización óptica y estructural para mostrar la formación de fase cuaternaria y también la pureza de fase del producto obtenido. En general, se demuestra que el método de síntesis de condiciones ambientales propuesto es capaz de proporcionar materiales fotovoltaicos compatibles con RoHS a un costo menor y un mayor rendimiento en comparación con los métodos basados en inyección en caliente, lo que abre un camino novedoso para la energía fotovoltaica ecológica de bajo costo. .
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Penny, Melissa. "Mathematical modelling of dye-sensitised solar cells." Thesis, Queensland University of Technology, 2006. https://eprints.qut.edu.au/16270/1/Melissa_Penny_Thesis.pdf.
Full textAbstract:
This thesis presents a mathematical model of the nanoporous anode within a dyesensitised solar cell (DSC). The main purpose of this work is to investigate interfacial charge transfer and charge transport within the porous anode of the DSC under both illuminated and non-illuminated conditions. Within the porous anode we consider many of the charge transfer reactions associated with the electrolyte species, adsorbed dye molecules and semiconductor electrons at the semiconductor-dye- electrolyte interface. Each reaction at this interface is modelled explicitly via an electrochemical equation, resulting in an interfacial model that consists of a coupled system of non-linear algebraic equations. We develop a general model framework for charge transfer at the semiconductor-dye-electrolyte interface and simplify this framework to produce a model based on the available interfacial kinetic data. We account for the charge transport mechanisms within the porous semiconductor and the electrolyte filled pores that constitute the anode of the DSC, through a one- dimensional model developed under steady-state conditions. The governing transport equations account for the diffusion and migration of charge species within the porous anode. The transport model consists of a coupled system of non-linear differential equations, and is coupled to the interfacial model via reaction terms within the mass-flux balance equations. An equivalent circuit model is developed to account for those components of the DSC not explicitly included in the mathematical
model of the anode. To obtain solutions for our DSC mathematical model we develop code in FORTRAN for the numerical simulation of the governing equations. We additionally employ regular perturbation analysis to obtain analytic approximations to the solutions of the interfacial charge transfer model. These approximations facilitate a reduction in computation time for the coupled mathematical model with no significant loss of accuracy. To obtain predictions of the current generated by the cell we source kinetic and transport parameter values from the literature and from experimental measurements associated with the DSC commissioned for this study. The model solutions we obtain with these values correspond very favourably with experimental data measured from standard DSC configurations consisting of titanium dioxide porous films with iodide/triiodide redox couples within the electrolyte. The mathematical model within this thesis enables thorough investigation of the interfacial reactions and charge transport within the DSC.We investigate the effects of modified cell configurations on the efficiency of the cell by varying associated parameter values in our model. We find, given our model and the DSC configuration investigated, that the efficiency of the DSC is improved with increasing electron diffusion, decreasing internal resistances and with decreasing dark current. We conclude that transport within the electrolyte, as described by the model, appears to have no limiting effect on the current predicted by the model until large positive voltages. Additionally, we observe that the ultrafast injection from the excited dye molecules limits the interfacial reactions that affect the DSC current.
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Gladney, Dewey Clinton. "Simulating radiation-induced defects on semiconductor devices." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Sep%5FGladney.pdf.
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Wang, Qiaoyi. "Theoretical investigation of realistic III-V semiconductor intermediate band solar cells." Thesis, University of Bristol, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.723446.
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Chen, Jie. "Spectroscopic Ellipsometry Studies of II-VI Semiconductor Materials and Solar Cells." University of Toledo / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1286813480.
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Ngamsinlapasathian, Supachai. "New aspects of dye-sensitized solar cells using mesoporous semiconductor electrodes." Kyoto University, 2004. http://hdl.handle.net/2433/145254.
Full textAbstract:
Kyoto University (京都大学)0048
新制・課程博士
博士(エネルギー科学)
甲第11150号
エネ博第99号
新制||エネ||27(附属図書館)
22719
UT51-2004-R25
京都大学大学院エネルギー科学研究科エネルギー基礎科学専攻
(主査)教授 吉川 暹, 教授 八尾 健, 教授 片桐 晃
学位規則第4条第1項該当
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Young, Eric Rustad. "Crystal Growth and Surface Modification of Pyrite for Use as a Photovoltaic Material." PDXScholar, 2018. https://pdxscholar.library.pdx.edu/open_access_etds/4233.
Full textAbstract:
Pyrite (FeS2) has recently attracted significant interest as a photovoltaic material due to its promising optical properties, high photon to electron conversion yield, and low-cost raw materials. However, hopes have been tempered by recent discoveries that suggest the presence of hard to remove bulk sulfur defects. This research was focused on engineering and implementing the crystallization of pyrite from a sulfur rich solution to counteract the material's natural tendency to form bulk sulfur defects. Homoeptiaxial layers and single-crystal samples have been grown from tellurium sulfur melts with an Fe:S ratio of 1:4 using both natural and synthetic substrates. The homoepitaxial layer has been characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high resolution transmission electron microscopy (HRTEM), confirming the epitaxial nature of the synthetic FeS2 layer, and X-ray and ultraviolet photoelectron spectroscopy (XPS and UPS) to better understand the energetics of the grown materials. Furthermore, epitaxial growth onto natural pyrite, in contrast to substrate etching, was established using sulfur-34 substitution and secondary ion mass spectrometry (SIMS). Growth onto synthetic pyrite was also described. Finally, the photovoltaic properties of homoepitaxial layers of high temperature solution growth pyrite onto a synthetic templating crystal was characterized using electrochemical methods.
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Willis, Shawn M. "Advanced optoelectronic characterisation of solar cells." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:07683f00-b7ba-4be3-aec0-f389fed34644.
Full textAbstract:
Optoelectronic characterisation techniques are assessed in their application to three solar cell systems. Charge injection barriers are found in PbS/ZnO colloidal quantum dot solar cells through the use of temperature dependent current-voltage and capacitance-voltage measurements. The injection barriers are shown to complicate the Mott-Schottky capacitance analysis which determines built-in bias and doping density. A model that incorporates depletion capacitance and a constant capacitance arising from the injection barriers is given to explain the Mott-Schottky plots. The junction mechanism at the PbS/ZnO interface is found to transition from excitonic to p-n behaviour based on the amount of UV photodoping the cell has received. External quantum efficiency analysis at different photodoping times reveals a growing charge collection region within the material, demonstrating the shift to p-n behaviour. This is further supported by the observance of depletion capacitance behaviour after, but not before, UV photodoping. Defects within GaAs cells containing InAs quantum dots are found to enhance the sub-bandgap performance of the cell using external quantum efficiency analysis. This is verified by illuminated current-voltage analysis using a 1000 nm high pass optical filter to block photons of larger energy than the bandgap. Using capacitance-voltage analysis, high temperature rapid thermal annealing is shown to induce defects in dilute nitride cells, which explains the drop in open circuit voltage compared to lower temperature annealed cells. The doping level of polymer solar cells exposed to air is found to increase with continued exposure using Mott-Schottky capacitance analysis. Current-voltage measurements show the formation of an Al2O3 barrier layer at the polymer/aluminium interface. The usefulness of capacitance-voltage measurements to probe the polymer/fullerene interface is investigated in thermally evaporated thiophene/C60 cells.
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Penny, Melissa. "Mathematical modelling of dye-sensitised solar cells." Queensland University of Technology, 2006. http://eprints.qut.edu.au/16270/.
Full textAbstract:
This thesis presents a mathematical model of the nanoporous anode within a dyesensitised solar cell (DSC). The main purpose of this work is to investigate interfacial charge transfer and charge transport within the porous anode of the DSC under both illuminated and non-illuminated conditions. Within the porous anode we consider many of the charge transfer reactions associated with the electrolyte species, adsorbed dye molecules and semiconductor electrons at the semiconductor-dye- electrolyte interface. Each reaction at this interface is modelled explicitly via an electrochemical equation, resulting in an interfacial model that consists of a coupled system of non-linear algebraic equations. We develop a general model framework for charge transfer at the semiconductor-dye-electrolyte interface and simplify this framework to produce a model based on the available interfacial kinetic data. We account for the charge transport mechanisms within the porous semiconductor and the electrolyte filled pores that constitute the anode of the DSC, through a one- dimensional model developed under steady-state conditions. The governing transport equations account for the diffusion and migration of charge species within the porous anode. The transport model consists of a coupled system of non-linear differential equations, and is coupled to the interfacial model via reaction terms within the mass-flux balance equations. An equivalent circuit model is developed to account for those components of the DSC not explicitly included in the mathematical model of the anode. To obtain solutions for our DSC mathematical model we develop code in FORTRAN for the numerical simulation of the governing equations. We additionally employ regular perturbation analysis to obtain analytic approximations to the solutions of the interfacial charge transfer model. These approximations facilitate a reduction in computation time for the coupled mathematical model with no significant loss of accuracy. To obtain predictions of the current generated by the cell we source kinetic and transport parameter values from the literature and from experimental measurements associated with the DSC commissioned for this study. The model solutions we obtain with these values correspond very favourably with experimental data measured from standard DSC configurations consisting of titanium dioxide porous films with iodide/triiodide redox couples within the electrolyte. The mathematical model within this thesis enables thorough investigation of the interfacial reactions and charge transport within the DSC.We investigate the effects of modified cell configurations on the efficiency of the cell by varying associated parameter values in our model. We find, given our model and the DSC configuration investigated, that the efficiency of the DSC is improved with increasing electron diffusion, decreasing internal resistances and with decreasing dark current. We conclude that transport within the electrolyte, as described by the model, appears to have no limiting effect on the current predicted by the model until large positive voltages. Additionally, we observe that the ultrafast injection from the excited dye molecules limits the interfacial reactions that affect the DSC current.
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Burton, Lee. "Phase stability and composition of tin sulfide for thin-film solar cells." Thesis, University of Bath, 2014. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.642045.
Full textAbstract:
This thesis details an investigation into the factors that could be restricting the performance of tin sulfide thus far. It is shown that there is confusion in the literature with respect to the assignment of different tin sulfide phases, and that the presence of these phases cannot easily be discerned with routine diffraction methods. In order to better understand the behaviour of tin sulfide in devices, it is important to isolate these materials as separate components and to consider the distinct properties of each. %Indeed, even a fundamental property such as the colour of SnS is still subject to conflicting reports. Herein, the targeted synthesis of SnS, SnS2 and Sn2S3 by chemical vapour transport is used to produce phase-pure single crystals, which are characterised in terms of structural, optical and electrical properties. These are compared directly with results from modern simulation methods as well as the work of others to explore fully the possible origins of performance losses. It is found that the work function of SnS is significantly lower than those of alternate successful photovoltaic materials, which means that novel device architectures are necessary in order to unlock the full potential of this promising photo-absorber. Concerns are also raised regarding the stability of the tin monosulfide phase with respect to degradation and defect formation over time, processes that undoubtedly affect device performance and lifetimes if sufficient safeguards are not put in place to suppress them. Further results of this 3 year research project also provide a broader platform for achieving sustainable light harvesting devices from the abundant and cheap elements, tin and sulfur.
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Cass, Michael Jeaffreson. "Simulations of electron transport at semiconductor electrodes and in dye sensitised solar cells." Thesis, University of Bath, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425886.
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Jadhav, Priyadarshani. "Singlet exciton fission, a multi-exciton generation process, in organic semiconductor solar cells." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/75635.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 107-115).
Organic semiconductor photovoltaics hold the promise of cheap production and low manufacturing setup costs. The highest efficiency seen in research labs, ~10% today, is still too low for production. In this work we explore implementations of a multiple exciton generation process, singlet exciton fission, to work around the Shockley-Queisser limit, according to which, all single junctions cells have a theoretical efficiency limit of 33.7%. This is the first implementation of a singlet fission photovoltaic. We measured a singlet fission efficiency of 72% at room temperature. We showed that singlet fission can be implemented in bulk heterojunction photovoltaics, which is an important result since some of the highest efficiency organic photovoltaics in the last 5 years have been bulk heterojunction structures. Secondly, we showed that the magnetic field effect can be used as a probe to investigate triplet dissociation in singlet fission devices. Thirdly, we implemented singlet fission photovoltaics, using the singlet fission material pentacene as donor and low bandgap infrared-absorptive lead chalcogenide quantum dots as acceptors. Singlet fission can enhance the efficiency of organic photovoltaics only if the fission material is paired with an absorptive low-energy-gap material. We find that pentacene triplet excitons dissociate at the pentacene/quantum dot heterojunctions with an internal quantum efficiency of 35%. Lastly, we investigate a series of materials to find a better acceptor in singlet fission photovoltaics using the methods and some results from the previous two investigations. We investigate device structures that pair pentacene and 6,13 diphenyl-pentacene as singlet fission donors with C60 , perylene diimides, PbS quantum dots and PbSe quantum dots as acceptors.
by Priyadarshani Jadhav.
Ph.D.
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Leventis, Henry C. "Transient optical studies of photoinduced charge transfer in semiconductor quantum dot solar cells." Thesis, Imperial College London, 2010. http://hdl.handle.net/10044/1/5576.
Full textAbstract:
Semiconductor quantum dots (also referred to as 'nanocrystals‘) are well suited as light-harvesting agents in solar cells because they are robust, have tuneable effective band gaps, and are easy to process. The research presented in this thesis is targeted towards the study of excitonic solar cells employing semiconductor nanocrystals as a light harvesting component. Gaining control of the interfacial charge transfer processes in operation in these devices forms a crucial part of any attempt to optimise their performance. In particular, the use of transient spectroscopic techniques reveals how efficient and long-lived charge separation can be achieved in these solar cell architectures. The primary focus of this research is to investigate the parameters influencing charge transfer in dye-sensitised solar cells (DSSCs) using colloidal quantum dots as light-absorbers. One aim is to study the impact of varying the thermodynamic driving forces provided for interfacial electron transfer on the yield of both the electron injection and hole regeneration reactions occurring within the DSSC; this can be achieved by varying the energetics of each component of the system (metal oxide, quantum dot and hole conductor) in turn. In addition, the interfacial morphology can be modulated by changing the passivating ligands present at the QD surface, and by modifying the structure of the redox mediator (or hole conductor). In doing so, we also attempt to improve our understanding of how charge carrier trapping in quantum dots impacts upon solar cell performance. Furthermore, new strategies towards solar cell design are presented, which show great potential as a result of their favourable photophysical properties. One of these approaches (presented in the final chapter) is to effect the in situ growth of CdS nanocrystals in a conducting polymer, a method which circumvents many of the processing issues associated with the use of nanocrystals in polymer blend solar cell architectures. It is hoped that the work presented in this thesis is used to develop design rules for the construction of semiconductor nanocrystal-based excitonic solar cells. By identifying which key parameters control the rates and yields of electron transfer at the nanocrystal interface, improvements in device efficiency can be realised. It is believed that these studies fill an important gap in our current understanding, and highlight some of the potential benefits and shortcomings of using semiconductor nanocrystals in cheap, solution-processed solar cells.
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Hey, Andrew Stuart. "Series interconnects and charge extraction interfaces for hybrid solar cells." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:f19e44a8-e394-4859-9649-734116bc22b8.
Full textAbstract:
This thesis investigates novel hole extraction interfaces and series interconnects for applications in organic photovoltaics, specifically in single junction solid-state dye-sensitized solar cells (DSSCs) and tandem DSSC/polymer bulk heterojunction solar cells. Improvements in hole extraction and device performance by using materials compatible with scalable deposition methods are presented, including tungsten- and molybdenum-disulphide (WS2 and MoS2), and p-type doped spiro-OMeTAD (2,2',7,7'-tetrakis-(N,N-di-p-methoxyphenylamine)9,9'-spirobifluorene) nanoparticle dispersions. WS2 and MoS2 hole extraction layers increase averaged short circuit currents by 20% and 16% respectively, and power conversion efficiencies by 19% and 14% respectively when compared with control devices. Similarly, doped spiro-OMeTAD nano-particle layers improved short circuit current densities by 32% and efficiencies by 9%. Tandem device interconnects using these novel hole extraction formats have been fabricated, but although devices did exhibit rectification, overall performance was poor. Possible reasons for their limited success have been analysed. Dye-sensitized solar mini-modules are also reported. In order to assure the scalability of DSSC technology, these larger area devices were constructed using doctor blade coating to deposit the hole transporter material. As well as achieving a respectable maximum power conversion efficiency of 2.6%, it has also been shown that the extent to which hole transporter infiltrates the mesoporous photoanode of these devices may be tuned by altering substrate temperature during deposition. It was found that an optimal coating temperature of 70 degrees C produced the best efficiency, with a corresponding pore-filling fraction of 41%.
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Icli, Kerem Cagatay. "Core-shell Type Nanocrystalline Fto Photoanodes For Dye Sensitized Solar Cells." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612328/index.pdf.
Full textAbstract:
Aim of this work is to construct dye sensitized solar cells employing core shell type nanocrystalline FTO/TiO2 photoanodes. Fluorine doped tin dioxide (FTO) nanoparticles were synthesized under hydrothermal conditions. Homogeneously precipitated SnO2 nanoparticles were dispersed in aqueous solutions containing NH4F as fluorine source and heat treated at 180oC for 24 hours. X-Ray analysis revealed that particles show rutile type cassiterite structure. Particles had 50 m2/g specific surface area measured by BET. Particle size was around 15-20 nm verified by XRD, BET and SEM analysis. Electrical resistivity of the powders measured with four point probe technique was around 770 ohm.cm for an F/Sn atomic ratio of 5, which showed no further decrease upon increasing the fluorine content of solutions. Thick films were deposited by screen printing technique and SEM studies revealed that agglomeration was present in the films which decreased the visible light transmission measured by UV-Visible spectrophotometry. TiO2 shell coating was deposited by hydrolysis of ammonium hexafluorotitanate and TiCl4 aqueous solutions. Efficiency of FTO nanoparticles was enhanced upon surface treatment where best result was 4.61 % for cells treated with TiCl4. Obtained photocurrent of 22.8 mA/cm2 was considered to be very promising for the future work. Enhancement
v
in efficiency was mostly attributed to suppressed recombination of photoelectrons and it is concluded that improved efficiencies can be obtained after successful synthesis of FTO nanoparticles having lower resistivity values and deposition of homogeneous shell coatings.
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Forsyth, Nicola M. "A study of Schottky barriers to CdS, and the CdTe : CdS heterojunction." Thesis, Cardiff University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375956.
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Liu, Piao. "Heterojunctions and Schottky Diodes on Semiconductor Nanowires for Solar Cell Applications." UKnowledge, 2010. http://uknowledge.uky.edu/gradschool_diss/77.
Full textAbstract:
Photovoltaic devices are receiving growing interest in both industry and research institutions due to the great demand for clean and renewable energy. Among all types of solar cells, cadmium sulfide (CdS) – cadmium telluride (CdTe) and cadmium sulfide (CdS) - copper indium diselenide (CuInSe2 or CIS) heterojunctions based thin film solar cells are of great interest due to their high efficiency and low cost. Further improvement in power conversion efficiency over the traditional device structure can be achieved by tuning the optical and electric properties of the light absorption layer as well as the window layer, utilizing nano template-assisted patterning and fabrication. In this dissertation, simulation and calculation of photocurrent generation in nanowires (NW) based heterojunction structure indicated that an estimated 25% improvement in power conversion efficiency can be expected in nano CdS – CdTe solar cells. Two novel device configurations for CdTe solar cells were developed where the traditional thin film CdS window layer was replaced by nanowires of CdS, embedded in aluminum oxide matrix or free standing. Nanostructured devices of the two designs were fabricated and a power conversion efficiency value of 6.5% was achieved. Porous anodic aluminum oxide (AAO) was used as the template for device fabrication. A technology for removing the residual aluminum oxide barrier layer between indium tin oxide (ITO) substrate and AAO pores was developed. Causes and remedies for the non-uniform barrier layer were investigated, and barrier-free AAO on ITO substrate were obtained. Also, vertically aligned nanowire arrays of CIS of controllable diameter and length were produced by simultaneously electrodepositing Cu, In and Se from an acid bath into the AAO pores formed on top of an aluminum sheet. Ohmic contact to CIS was formed by depositing a 100 nm thick gold layer on top and thus a Schottky diode device of the Au/CIS nanowires/Al configuration was obtained. Material properties of all these nanowires were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), absorption measurement. Current-voltage (I-V), capacitance-voltage (C-V) and low-temperature measurements were performed for all types of devices and the results were analyzed to advance the understanding of electron transport in these nano-structured devices.
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Khallaf, Hani. "Chemical Bath Deposition of Group II-VI Semiconductor Thin Films for Solar Cells Applications." Doctoral diss., University of Central Florida, 2009. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2101.
Full textAbstract:
Chemical bath deposition (CBD) is the analog in liquid phase of the well-known chemical vapor deposition technique in the vapor phase. In CBD, deposition of thin films takes place from aqueous solutions at low temperatures by a chemical reaction between dissolved precursors, with the help of a complexing agent. Among all techniques used to grow Group II-VI semiconductors, CBD has the advantage of being a simple, low temperature, and inexpensive large-area deposition technique. So far, its contribution in thin film solar cells industry has been mainly limited to growing n-type CdS and/or ZnS window layers for CdTe-based and CIGS-based solar cells. In this work we first optimize the CBD process of CdS using nitrilotriacetic acid and hydrazine as complexing agents as an alternative to ammonia. We then study the effect of the cadmium precursor on the optical/electrical properties, as well as crystal structure, morphology, and composition of CBD-CdS films. A better understanding of the CBD process of CdS as a whole has been achieved and high quality CBD-CdS films have been obtained. Next, we investigate in-situ doping of CBD-CdS with group III elements, such as B, Al, In, and Ga. The objective is to show that CBD is capable of not only growing CdS but also of doping it to reduce its resistivity and, as a result, facilitate its use in solar cells as well as other optoelectronic device fabrication. A four orders of magnitude drop of film resistivity has been achieved without a significant change in film bandgap, structure, or morphology. Finally, we test the possibility of using CBD to grow transparent conducting oxide (TCO) films, such as Al-doped ZnO films and cadmium stannate films. First, we study CBD of ZnO and later in-situ doping of ZnO using Al. High quality ZnO thin films have been grown using CBD with the help of four different complexing agents. Post heat treatment in argon ambient helped reduce resistivity of CBD-ZnO undoped films to ~ 10-1 Ω-cm. In-situ doping of such films using Al shows promising results. Such films could be an alternative to indium tin oxide (ITO) layers that are commonly used as TCO layers for solar cells. Another approach is to use CBD to grow CdO and SnO2 thin films, with the goal of obtaining Cd2SnO4 by later annealing of these two layers. Cadmium stannate is another TCO candidate that could replace ITO in the near future. We have succeeded in growing CBD-CdO thin films using three different complexing agents. Undoped CBD-CdO films with a resistivity as low as 1.01 x10-2 [omega]-cm and a carrier density as high as 2.59 x 1020 cm-3 have been obtained. SnO2 films have been successfully grown using CBD. Fabrication of Cadmium stannate thin films using CBD is investigated. In summary, our objective to expand the use of CBD beyond just growing CdS and ZnS, and to test the possibility of using it for in-situ doping of group II-VI semiconductors as well as TCO layers fabrication proved to be successful. We believe that this may have a significant impact on solar cells as well as other optoelectronic devices fabrication industry, due to the simplicity and the cost-effectiveness of CBD.Ph.D.
Department of Physics
Sciences
Physics PhD
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Jacobs, Sean Abraham. "Nanotip silicon surface for anti-reflection and multiple exciton generation of semiconductor solar cells." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 57 p, 2009. http://proquest.umi.com/pqdweb?did=1885519531&sid=10&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Abulikemu, Mutalifu. "Synthesis and Characterization of Colloidal Metal and Photovoltaic Semiconductor Nanocrystals." Diss., 2014. http://hdl.handle.net/10754/335794.
Full textAbstract:
Metal and semiconducting nanocrystals have received a great deal of attention from fundamental scientists and application-oriented researchers due to their physical and chemical properties, which differ from those of bulk materials. Nanocrystals are essential building blocks in the development of nanostructured devices for energy conversion. Colloidal metals and metal chalcogenides have been developed for use as nanocrystal inks to produce efficient solar cells with lower costs. All high-performing photovoltaic nanocrystals contain toxic elements, such as Pb, or scarce elements, such as In; thus, the production of solution-processable nanocrystals from earth-abundant materials using environmentally benign synthesis and processing methods has become a major challenge for the inorganic semiconductor-based solar field. This dissertation, divided into two parts, addresses several aspects of these emerging challenges.
The first portion of the thesis describes the synthesis and characterization of nanocrystals of antimony sulfide, which is composed of non-scarce and non-toxic elements, and examines their performance in photovoltaic devices. The effect of various synthetic parameters on the final morphology is explored. The structural, optical and morphological properties of the nanocrystals were investigated, and Sb2S3 nanocrystal-based solid-state semiconductor-sensitized solar cells were fabricated using different deposition processes. We achieved promising power conversion efficiencies of 1.48%.
The second part of the thesis demonstrates a novel method for the in situ synthesis and patterning of nanocrystals via reactive inkjet printing. The use of low-cost manufacturing approaches for the synthesis of nanocrystals is critical for many applications, including photonics and electronics. In this work, a simple, low-cost method for the synthesis of nanocrystals with minimum size variation and waste using reactive inkjet printing is introduced. As a proof of concept, the method was used for the in situ synthesis of gold nanoparticles as a model system. Relatively monodisperse gold nanoparticles were produced. The size and shape of gold nanoparticles can be controlled by the gold precursor and surfactant concentration in the ‘ink.’ This approach can be extended to the synthesis of other nanocrystals and is thus a truly impactful process for the low-cost synthesis of materials and devices incorporating nanocrystals.
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Fangsuwannarak, Thipwan Photovoltaic & Renewable Energy Engineering UNSW. "Electronic and optical characterisations of silicon quantum dots and its applications in solar cells." 2007. http://handle.unsw.edu.au/1959.4/44340.
Full textAbstract:
In this thesis, the structural, optical and electrical properties of crystalline silicon quantum dots (SiQDs) are examined for application to silicon based tandem cells. The approach has been to concentrate on all silicon devices by taking advantage of quantum confinement in low-dimensional Si. RF magnetron co-sputtering provided the capability of creating superlattice structures in conjunction with high temperature annealing, to form Si nanocrystals in an oxide matrix. Structural techniques, including Fourier transform infrared spectroscopy (FTIR), micro-Raman spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), and Secondary ion mass spectroscopy (SIM) were employed to gather structural information about the SiQD/SiO2 SLs. The result combine presents that the packing density of Si QDs, correlated to the oxygen content of the silicon rich oxide layer can be control independently. The effect of Si nanocrystallite density on Raman scattering is investigated. The preliminary results present that a decrease in the oxygen content (x) results in an increased sharpness of the Strokes-mode peak of nanocrystalline Si, attributed to an increase in the proportion of crystalline Si because of the increased number of SiQDs. However the influence of the surface region on the crystallite core intensity scattering becomes dominant, when SiQD size diameter is very small (less than 3 nm). The present work shows that a decrease in x-content leading to an increase of the SiQD concentration, initially results in the enhancement of the lateral conductivity in the SiQD superlattice material. In this work, the Al contacting scheme, using a prolonged heat treatment technique at elevated temperature less than the eutectic point of Al and Si (577C) has been successfully applied to making Ohmic contacts on both SiQD SLs in oxide and nitride matrices. Activation energy (Ea) of SiQDs, extracted from a linear Arrhenius plot is investigated in the present work in order to expand the understanding of engineering electrical injection in laterally active paths. It is found that a lower barrier height of dielectric matrix influences to the lateral electron transport of the SiQDs in such dielectric matrix. PL results confirm that the band gap of surface oxidized SiQDs widens due to quantum confinement. The present results reveal that the strong peak (Q-peak) due to quantum confinement is more effective in the emission with increasing SiQD concentration. The surface oxide is believed to play an important role in the reduction of SiQD luminescence due to a trapped exiciton. It is concluded that SiQDs surface oxide accompanied by a SiO2 matrix may not provide a good passivation in very small SiQD size. However the energy band gap and conductivity of the SiQDs are tunablity, in the optimum range of SiQD size and concentration. This observation may be important for future nanoelectronics applications.