Dissertations / Theses on the topic 'Photovoltaics'
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Lund, Miguel. "photovoltaics." Thesis, Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-4412.
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Solcellsteknik med nätanslutning är relativt nytt i Sverige och lagarna är oklara vad gäller anläggningar på bostadshus villor och offentliga hus. I analysen redovisas den ekonomiska aspekten av producerad solcellsel och konsumtionen av denna. Solcellsanläggningen på kommunhuset i Mönsterås har studerats, varvid följande resultat har framkommit: från de installerade solcellerna (210 kvm), får man 10 % av den totala energiförbrukningen i byggnaden. Kostnaden för solcellerna och installationen av dem är subventionerade av staten med 70 %. För den resterande kostnaden skulle solcellerna vara i bruk i 24 år för att täcka kostnaden. Produktionen och förbrukningen i kommunhuset i Mönsterås har jämförts med två solcellsanläggningar i Malmö och Göteborg (hur stor del av den el som förbrukats av Malmö kårhus och av äldreboendet i Göteborg har utgjorts av el från solcellsanläggningarna). Det visade sig att även Malmös och Göteborgs solceller, stod för cirka 10 % av deras totala energiförbrukning, vilket visar att den teoretiska beräkningen av Mönsterås solceller stämmer. Lennart Söders förslag om nya bestämmelser är till för att utveckla och stödja utbyggnaden av nya förnybara källor. Det har visat sig att det är för stor skillnad mellan stora (större än 1500 kW)och små (max 1500 kW) anläggningars kostnader för anslutning och elöverföring till nätbolag. Elbolagens höga kostnader för elmätning, som krävs för elcertifikat har gjort att många valt att inte skaffa dessa elcertifikat. Elcertifikaten är till för att stödja utvecklingen av förnybara energianläggningar. Därför har Söder även gett föreslag till ett skäligt sätt att läsa av sin egen mätare enklare. Lennart Söder föreslår att avgiften för de små anläggningarna ska vara 3öre/kWh plus en fast kostnad för mätning, beräkning och rapportering av nätkoncessionshavarens nät under max. 10 år från produktionsstart. Från 2015 betalar alla full årlig nätavgift. Anläggningar med max 63 amperes säkringsnivå och som är anslutna till lågspänningsnät ska inte behöva rapportera timvis utan månadsvis. De ska dessutom själva kunna göra mätning och rapportering för elcertifikat. De lagar som diskuteras i denna analys är 4 § (2003:113) som handlar om ändring i elcertifikat och ellag (4 kap. 10 § 1997:857). Lönsamheten av en investering i en solcellsanläggning är beroende av tre faktorer; elpriset på elmarknaden, solcellernas pris på marknaden och bestämmelserna om mätningskostnaden av förnybar energi. leder Det kan inte bli lönsamt förrän elpriset har stigit och solcellsystemen har sjunkit i pris, så att de ligger i samma prisklass som inköp av el från ett elbolag.
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Lee, Jiye. "Singlet fission photovoltaics." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/79496.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 131-151).
The efficiency of a solar cell is restricted by the "single junction limit," whereby photons with energy higher than the bandgap lose energy by thermalization. Singlet exciton fission splits a high-energy molecular excitation ("singlet" exciton) into a pair of lowenergy ones ("triplet" excitons). In solar cells, it promises to generate two electrons per photon, potentially overcoming the singlet junction efficiency limit. In this thesis, we present singlet-fission-based photovoltaic cells that generate more than one electron per photon. We first demonstrate organic photodetectors with quantum efficiencies reaching 100% by exploiting singlet exciton fission. Through study of the magnetic field dependence of the fission process, we find an optimum thickness of singlet fission layers that guarantees the nearly 100% conversion of a singlet into two triplets. By employing an exciton blocking layer and a light trapping scheme to the solar cell, we demonstrate the peak external quantum efficiency exceeding 100% in the visible spectrum. It is the first time that any solar cell has generated more than one electron per photon outside the UV spectrum. We also build a simple model that predicts the rate of singlet fission through intermolecular coupling, enabling rational designs of singlet fission molecules and devices. Finally, we propose a future direction-generating three electrons per photon. As a step toward this goal, we demonstrate singlet exciton fission in hexacene, whose energetics may allow a singlet to split into three triplets.
by Jiye Lee.
Ph.D.
3
Taymur, Eyup. "Photovoltaics Systems Sizing." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1259684298.
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McDonald, Calum James. "Alternative perovskites for photovoltaics." Thesis, Ulster University, 2017. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.722581.
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This thesis explores new types of perovskite and perovskite-like materials for photovoltaics, with a view towards demonstrating novel and low-cost materials such as metal oxide perovskites for photovoltaics. The first part explores the prototypical organometal halide perovskite CH3NH3Pbl3, where CH3NH3 = methylammonium (MA). MAPbl3 has been studied by the partial replacement of its organic component, MA, with the larger molecule ethylenediammonium (EDA), with the chemical formula NH3(CH2)2NH3. This in turn introduces vacancies into EDA-containing MAPbl3, which has allowed the study of a non-stoichiometric organometal halide perovskite. This work observed that the partial replacement of the MA molecule with a larger molecule reduced the hysteresis. Following this, the low-cost perovskite-like material methylammonium iodo bismuthate has been studied. Methylammonium iodo bismuthate has the chemical formula MA3Bi2lg (MABI), and forms a zerodimensional network of Bi2lg bioctahedra with quantum confinement. MABI has been characterised and used to fabricate solar cells. This bulk material with an ordered zero-dimensional internal structure exhibits carrier multiplication, and this thesis has demonstrated the fabrication of MABI solar cells. The structure has also been shown to favourably accommodate a small quantity of quantum confined silicon nanocrystals, opening up an avenue of possible hybrid devices which can be explored. Building on this knowledge, this thesis then explores two perovskite oxide materials which have not previously been demonstrated in photovoltaics. Both perovskite oxides exhibit strong and broad visible light absorption which extends into the near-infrared spectrum. One of which, Sr-deficient strontium niobate (Sro.gNb03), exhibits metallic conduction, and has been demonstrated in a photovoltaic cell for the first time. This work demonstrates the possibility of extracting excited carriers in a metal oxide with metallic conduction. The metal oxide perovskite calcium manganite, Ca2Mn2O5, has also been explored for photovoltaics. Ca2Mn2O5 is a plasmonic metal oxide and is therefore highly attractive material for photovoltaics. Solar cells were successfully fabricated using Ca2Mn2O5, and these results demonstrate the possibility of carrier extraction and highlight great opportunities for solar energy harvesting.
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Dissanayake, Mudiyanselage Nanditha Madujith. "Semiconductor nanocrystal hybrid photovoltaics." Thesis, University of Surrey, 2008. http://epubs.surrey.ac.uk/844501/.
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Semiconductive organic polymer and small molecule materials are widely researched for the fabrication of low cost, large area and flexible organic photovoltaic devices. Semiconductor nanocrystals which demonstrate size tuneable optical bandgaps, can be incorporated with organic materials to enable wider spectral absorption and consequently improve the power conversion efficiency (n) of organic photovoltaics. Hybrid systems fabricated with wide bandgap (CdSe, CdTe) nanocrystals have reported promising results to this end. However, in order to further increase the spectral absorption of solar irradiation, particularly in the energy rich near infrared region, narrow bandgap nanocrystal systems must be utilised in hybrid photovoltaic fabrication. Attempts of using Pb chalcogenide (PbS and PbSe) nanocrystals in hybrid architectures have not yet been completely successful. The aim of this project was to design, fabricate and characterise novel organic (fullerene) and PbS-nanocrystal based hybrid photovoltaic systems for broadband light harvesting. Small molecule organic materials (pentacene and tetracene) and C60 were used as the organic and fullerene materials together with PbS-nanocrystals synthesised in-house. Three primary device architectures were investigated, where PbS-nanocrystals were used as an electron donor, acceptor and also as a tandem layer. A PbS-nanocrystal/C60 hybrid photovoltaic device in which the nanocrystals act as charge donors demonstrated a thirty fold increase in short circuit current density (Jsc) upon removal of the as-synthesised oleic acid ligands studied using X-ray photoelectron spectroscopy (XPS) and thermogravimetric methods. XPS analysis demonstrated a shift in the binding energy of Pb4f7/2 orbital, attributed to the removal of oleic ligands. Furthermore, photosensitivity up to 1600 nm was demonstrated with an external quantum efficiency (EQE) of 0.025%, together with a maximum EQE of 3.3% at 450 nm. The PbS-nanocrystal/C60 hybrid photovoltaic architecture was optimized by exchanging the as- synthesised oleic ligands in PbS-nanocrystals to shorter butylamine ligands, characterised by photoluminescence and infrared spectroscopy, which improved charge carrier mobility. It was seen using atomic force microscopy that butylamine capped nanocrystals formed smooth non-porous films on the conductive substrates which enabled deposition of thinner nanocrystal films (100 nm) further improving charge extraction. An eight fold improvement of n was observed as compared to oleic capped based hybrid nanocrystal photovoltaics. Furthermore, it was found that carrier mobility of a PbS-nanocrystal film was improved by soaking in anhydrous methanol. Consequently, the hybrid photovoltaic fabricated after methanol treatment demonstrated a Jsc of 5 mAcm-2 and an n of 0.44%, which is the highest reported for a hybrid photovoltaic incorporating narrow bandgap nanocrystals, A maximum EQE of 35% at 400 nm and up to 5% EQE within the near infrared region was also demonstrated from this device. Further optimization of this photovoltaic system is discussed by modelling the maximum expected Jsc and by inferring properties controlling the open circuit voltage and fill factor. PbS-nanocrystals were also used as electron acceptors incorporated with acenes. Photoinduced electron transfer between tetracene/PbS-nanocrystals was seen to be more efficient as opposed to pentacene/PbS-nanocrystals, studied using photoluminescence quenching and EQE measurements. This phenomenon was explained using an interfacial effect between the pentacene/PbS-nanocrystals attributed to the permanent dipole moment of the nanocrystals. Furthermore, the possibility of using PbS-nanocrystals as a donor-acceptor tandem layer was investigated by fabrication of a multifunctional hybrid photovoltaic using tetracene and C60, which demonstrated up to two orders greater EQE in both the ultraviolet and near infrared. Device operations for all above architectures were justified by direct measurement of the PbS-nanocrystal energy levels using ultraviolet photoelectron spectroscopy and cyclic voltammetry measurements. It is concluded that with suitable optimisations the novel photovoltaic systems studied here could be explored as a viable thin film photovoltaic technology.
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Wang, Wentao, and 王文韬. "Novel ferroelectric-semiconductor photovoltaics." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/206435.
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Solar cells have been traditionally developed for optimizing three key steps for charge carriers: generation, separation, and transport. Conventional solar cells are essentially PN junction based, and utilize the internal electric field near the junction interface for realizing charge carrier separation. However, this kind of structure limits material choices and device fabrication to form a working junction due to issues such as lattice mismatch, doping, and band alignment. Ferroelectric photovoltaic devices with typical capacitor structure have been developed to overcome the junction caused disadvantage but suffer from the poor charge transport issue. In this work, novel ferroelectric-semiconductor photovoltaic devices were developed and investigated in detail with experimental results and theoretical simulation. This type of solar cell is fundamentally different with traditional PN junction based solar cells, utilizing ferroelectric polarization for charge separation in semiconductor layer. Systematical works have been conducted on: (1) device working principle and mechanism study; (2) effect of electrode; (3) influence of device key dimension parameters. The new cells showed the rectifying behavior and effective photovoltaic effect after specific asymmetric polarization. Furthermore, the device performance has been improved through adjusting electrode design and semiconductor layer thickness, which is mainly due to the optimized electric field strength and distribution resulting from polarization.
As low cost commercial semiconductor, the multicrystalline silicon (mc-Si) has great potential application in the novel ferroelectric-semiconductor photovoltaic devices. However, the grain boundaries with high density of defects limit the material electric properties. In order to improve the multicrystalline silicon transport property, a polar molecules system was developed to play the role in grain boundaries passivation. The small polar molecule composition and solution passivation process were carried out to optimize the passivation effect. The result showed the developed ZK series solutions reduced the Rsheet across large-angle grain boundaries by up to more than one order to be close to the bulk Rsheet. Also, the correlation between the grain misorientation and passivation effectiveness was built up.published_or_final_version
Mechanical Engineering
Doctoral
Doctor of Philosophy
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Mapel, Jonathan King. "Organic photovoltaics and concentrators." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/44904.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2008.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 158-169).
The separation of light harvesting and charge generation offers several advantages in the design of organic photovoltaics and organic solar concentrators for the ultimate end goal of achieving a lower cost solar electric conversion. In this work, we explore two new device architectures. In antenna organic solar cells, we utilize external energy transfer mediated by surface plasmon polaritons to increase the efficiency of existing organic photovoltaic devices limited in performance by the exciton diffusion bottleneck. This unique architecture is analyzed for its functionality and the efficiencies of each added step is quantified. Although the introduction of additional energy transduction will ultimately introduce more losses, bypassing the exciton diffusion bottleneck offers the potential for increased efficiency through judicious device design. We also seek to enable the use of high efficiency inorganic solar cells in organic solar concentrators which aim to exploit high performance of the PV cells in low cost, nontracking configurations. By utilizing thin films of organic chromophores on high refractive index glass substrates, we are able to apply the recent advances of organic optoelectonics to the fluorescent concentrator platform, including near field energy transfer, solid state solvation, and phosphorescence. By reducing self-absorption losses, we demonstrate optical flux gains an order of magnitude greater than previously published results and thereby reduce the effective cost of inorganic solar cells by at least a factor of ten. Combined with the potential for low cost solution processing, the high flux gains and power efficiencies realized here should enable a new source of inexpensive solar power.
by Jonathan King Mapel.
Ph.D.
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Droessler, Laura Melanie. "Lead oxides for photovoltaics." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:8a0216a2-3efe-4de4-a853-d5b6ec53eeee.
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This thesis investigates lead oxides as photovoltaic materials. Vacuum deposition methods and ex-situ annealing are used to produce different stoichiometries of lead oxide. The relationship between structure and the optoelectronic properties is then investigated. Following this, a number of photovoltaic devices are prototyped and a Kelvin probe used to determine and understand the band structure of devices. Thin films of PbO produced via air annealing of thermally evaporated lead consist of a mixture of two phases, orthorhombic and tetragonal, that determine the materials properties and effectiveness as absorber layer in a Schottky device. Films of higher tetragonal content are more photoactive, showing lower series resistance. Kelvin probe reveals that with an increasing work function of the PbO with increasing duration of the annealing, the Schottky barrier between PbO and Al increases, which results in a higher VOC. This trend is inverted when the Fermi level of PbO drops below that of ITO, creating an opposing junction. Reactively sputtered PbO2 films are highly conductive degenerate semiconductors. Increasing oxygen flow rate during deposition leads to increased resistivity and decreased mobility, resulting from a decrease in grain size. Alongside this an increase in carrier concentration is observed as the material gets less ordered at higher oxygen flow rates, which results in an increase in Fermi level. Due to its high conductivity the material is not photoactive, and the high work function between -5.6 and -5.8 eV does not allow the formation of a Schottky junction or a p-n junction with the evaporated p- type PbO. Post deposition annealing of the sputtered films leads to the formation of the more resistive Pb3O4 phase. This material shows lower carrier concentration and mobility, however, work functions are similarly high. The changes induced by the heat treatment are not substantial enough to be able to create a junction between the as-deposited and the annealed material, as is revealed by Kelvin probe and Hall Effect measurements. Heterojunctions between P3HT and Pb3O4 were made to test predictions made by KP measurements. A heat treatment on P3HT improved its electronic properties and raised the Fermi level, resulting in the transformation of a diode in to a photovoltaic device and a decrease in dark current.
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Flicker, Jack David. "Three dimensional carbon nanotube based photovoltaics." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41155.
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Photovoltaic (PV) cells with a three dimensional (3D) morphology are an exciting new research thrust with promise to create cheaper, more efficient solar cells by allowing for a "bottom up" approach to texturing thin film solar cells. This work introduces a new type of 3D PV device based on carbon nanotube (CNT) arrays. These arrays are paired with the thin film heterojunction, CdTe/CdS, to form a complete 3D carbon nanotube PV device (3DCNTPV). A complete theory for the power increase at off-normal angles of solar flux is developed for these cells. Marriage of a complicated 3D structure with production methods traditionally used for planar CdTe solar cell is challenging. This work examines the problems associated with processing these types of cells and systematically alters production methods of the semiconductor layers and electrodes to increase the short circuit current, eliminate parasitic shunts, and increase the open circuit voltage.
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Albarghouthi, Mohammad Talha. "Optimization of hydraulics and photovoltaics in a solar water heater with photovoltaic-powered pump." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ31541.pdf.
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Mallick, Tapas K. "Optics and heat transfer for asymmetric compound parabolic photovoltaic concentrators for building integrated photovoltaics." Thesis, University of Ulster, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288897.
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Kim, Yongjin. "Experimental investigation of the interfacial fracture toughness in organic photovoltaics." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/47605.
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The development of organic photovoltaics (OPVs) has attracted a lot of attention due to their potential to create a low cost flexible solar cell platform. In general, an OPV is comprised of a number of layers of thin films that include the electrodes, active layers and barrier films. Thus, with all of the interfaces within OPV devices, the potential for failure exists in numerous locations if adhesion at the interface between layers is inherently low or if a loss of adhesion due to device aging is encountered. To date, few studies have focused on the basic properties of adhesion in organic photovoltaics and its implications on device reliability. In this dissertation, we investigated the adhesion between interfaces for a model multilayer barrier film (SiNx/PMMA) used to encapsulate OPVs. The barrier films were manufactured using plasma enhanced chemical vapor deposition (PECVD) and the interfacial fracture toughness (Gc, J/m2) between the SiNx and PMMA were quantified. The fundamentals of the adhesion at these interfaces and methods to increase the adhesion were investigated. In addition, we investigated the adhesive/cohesive behavior of inverted OPVs with different electrode materials and interface treatments. Inverted OPVs were fabricated incorporating different interface modification techniques to understand their impact on adhesion determined through the interfacial fracture toughness (Gc, J/m2). Overall, the goal of this study is to quantify the adhesion at typical interfaces used in inverted OPVs and barrier films, to understand methods that influence the adhesion, and to determine methods to improve the adhesion for the long term mechanical reliability of OPV devices.
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Oliver, Mark. "The viability of solar photovoltaics : with specific reference to building integrated photovoltaics cladding systems." Thesis, University of Surrey, 1999. http://epubs.surrey.ac.uk/853/.
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Tautz, Raphael. "Charge separation in organic photovoltaics." Diss., lmu, 2013. http://nbn-resolving.de/urn:nbn:de:bvb:19-153053.
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Wu, Yupeng. "Thermal management of concentrator photovoltaics." Thesis, University of Warwick, 2009. http://wrap.warwick.ac.uk/3218/.
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Photovoltaic Concentrator systems, which increase the solar radiation intensity on the photovoltaic cells, may reduce the system cost, if the cost of the concentrator is less than the photovoltaic material displaced. An Asymmetric Compound Parabolic Photovoltaic Concentrator (ACPPVC) for building façade integration with a solar concentration ratio of 2.0 has been designed, fabricated and experimentally characterised. The truncated ACPPVC has acceptance half angles of 0° and 55° and an absorber width of 125mm. Phase Change Materials (PCM) have been integrated to the rear of the PV panel to moderate the temperature rise of the PV and maintain good solar-electrical conversion efficiency. The thermal behaviour of a Fresnel lens PV Concentrator (FPVC) has also been studied in this work. A two-dimensional ray trace technique has been used to predict the optical performance and the angular acceptance of the ACPPVC system. The predicted highest optical efficiency was 88.67% for the ACPPVC-55 system. Extensive indoor experimental characterisation of a number of PV systems was undertaken for a range of incident solar radiation intensities using a highly collimated solar simulator developed specifically for this project. Experimental results showed that the electrical output from the ACPPVC-55 was approximately 1.8 of that of a non-concentrating PV system with similar solar cells area. The electrical conversion efficiency for the ACPPVC-55 system was further increased, when RT27 PCM was incorporated to its rear.
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Nismy, Nasrul A. "Organic-carbon nanotube hybrid photovoltaics." Thesis, University of Surrey, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.583325.
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The conversion of solar energy into electricity through the photovoltaic effect could be a viable approach to supply the global energy requirements with minimal detrimental effects on the enviromnent. Recent research on photovoltaics has focussed on organic photovoltaics (OPVs) which utilises organic materials due to their ease of processing, high light absorption coefficient and potential for low cost thin film device fabrication compared to its inorganic counterparts. The work presented in this Thesis is focussed on enhancing the photo-generated CUlTent of OPV s based on conjugated polymers and fullerene derivatives through the incorporation of multi wall carbon nanotubes (MWCNTs). Initial studies focus on the identification of suitable conditions for the fabrication of efficient reference devices (photo-active layer composed of poly(3-hexylthiphene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (C6o-PCBM)) in order to observe any improvements upon addition of MWCNTs into the active layer. Deteriorated device characteristics are achieved with pristine MWCNTs (p- MWCNTs) incorporated P3HT:PCBM active layer devices due to the poor thin film morphology of the P3HT:p-MWCNTs:PCBM active layer films. This is identified as being due to the poor dispersion of nanotubes in organic solvents that hampers the formation of good interpenetrating networks at the nano-scale. Therefore, to improve the dispersion of MWCNTs in 1,2 dichlorobenzene (DCB) solvent acid functionalisation of MWCNTs is carried out. These dispersible acid functionalised MWCNTs (O-MWCNTs) in DCB are characterised by Raman and infrared spectroscopy, for verification of attachment of functional groups. An enhanced device performance is achieved through the incorporation of 0- MWCNTs in to the P3HT:PCBM system. Optimisation ofP3HT:0-MWCNTs:PCBM solar cells is observed to lead to devices with higher short circuit current densities (Jsc). Investigations towards understanding the enhancement of Jsc from P3HT:0- MWCNTs:PCBM is carried out through external quantum efficiency (EQE) measurements and photoluminescence (PL) spectroscopy. Higher EQE values of P3HT:O-MWCNTs:PCBM active layer devices, in particularly the higher collection probability in the blue and green region of the electromagnetic spectrum suggests an efficient charge separation at donor/acceptor (D/A) heterojunction, reduced recombination, and improved charge carrier mobility as the reasons affecting the increase in the net photo-generated current. The Jsc is shown to increase from 8.0 mAcm-2 in the reference device to 8.34 mAcm-2 in the O-MWCNTs incorporated device. Furthermore, the drastic PL quenching suggests enhanced exciton dissociation in the system and is in agreement with the results achieved from EQE measurements. Analysis of these observations lead to the conclusion that O-MWCNTs are responsible for creating additional charge generating sites (exciton dissociation centres, EDCs) in the active layer. Favourable charge generation at P3HT/O- MWCNTs is observed due to the efficient exciton dissociation at the nano- heterojunction. A hypothesis of "O-MWCNTs as EDCs" is formulated on considering these observations and further investigation ofthe hybrid OPV system is carried out. The dielectric constant (ε) for the composite systems of P3HT:PCBM and P3HT:O- MWCNTs:PCBM are estimated from a space charge limited current (SCLC) model and compared. A 1.23 times increase in the e of P3HT:O-MWCNTs:PCBM composite compared to P3HT:PCBM indicates a lower Coulombic attraction which leads to a lower binding energy. Charge transport analysis conducted through a SCLC model is used to understand the effect of addition of the tertiary component to the existing system and hole mobility is estimated. The addition of O-MWCNTs is favourable in lowering the ε , minimising the exciton binding energy and enhancing the exciton dissociation process in the P3HT:O- MWCNTs:PCBM system. The Jsc achieved for this system is higher than the existing P3HT:PCBM system and the calculated higher hole mobility of this system supports the improved charge transport process. As a result of these achievements, the role of O-MWCNTs in the OPV system is recognised as beneficial for charge generation.
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Stavrinadis, Alexandros. "Inorganic semiconductor nanoparticles for photovoltaics." Thesis, University of Oxford, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.526119.
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Shi, Wenda. "Fullerene isomers for organic photovoltaics." Thesis, Queen Mary, University of London, 2017. http://qmro.qmul.ac.uk/xmlui/handle/123456789/25945.
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The as-produced isomer mixture of the organic photovoltaic device acceptor material bisPC62BM has been purified into its constituents by peak-recycling HPLC, and those individual isomers were characterised by UV-Vis absorption spectroscopy and cyclic voltammetry. A total of 18 isomers were purified from the mixture to a standard exceeding 99.5% with respect to other isomers. The HOMOs, LUMOs, and HOMO-LUMO gaps of the purified isomers vary from (-5.673 to -5.402 eV), (-3.901 to -3.729 eV), and (1.664 to 1.883 eV), respectively. We also find a correlation between HPLC retention time and the relative positions of the addends; in that generally the closer the addends are to each other the longer the retention time of the isomer, and vice versa. The OPV acceptor molecule PC71BM was also purified into its constituent isomers to a standard of at least 99%. The total three purified isomers were each characterized by 13C NMR and UV-vis spectroscopy, and cyclic voltammetry. These characterizations were supported by HF/DFT ab-initio calculations. All three isomers are methano-fullerenes. The most abundant isomer (85% of the mixture) exists as a racemate involving the 8-25 bond of C70. The other two isomers both involved the 9-10 bond of C70, but are distinguished by opposing orientations of the addend with r and s pseudo-asymmetry about carbon atom 71. The r and s isomers comprised 9% and 6% of the as-produced of the mixture, respectively. In order of decreasing abundance, the LUMO levels of the isomers were -3.9316, -3.9194 and -3.9197 eV and the HOMO-LUMO gaps were 1,772, 1.754 and 1.748 eV.
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Kavlak, Goksin. "Drivers of photovoltaics cost evolution." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/115605.
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Thesis: Ph. D. in Engineering Systems, Massachusetts Institute of Technology, School of Engineering, Institute for Data, Systems, and Society, 2018.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 99-109).
Photovoltaics (PV) have experienced notable development over the last forty years. PV module costs have declined 20% on average with every doubling of cumulative capacity, while global PV installations have increased at an average rate of 30% per year. However, costs must fall even further if PV is to achieve cost-competitiveness at high penetration levels and in a wide range of locations. Understanding the mechanisms that underlie the past cost evolution of PV can help sustain its pace of improvement in the future. This thesis explores the drivers of and constraints to cost reduction and large-scale deployment of PV. By developing novel conceptual and mathematical models, we address the following questions: (1) What caused PV's cost to fall with time? (2) How may materials constraints influence PV cost and deployment? These questions are addressed in the analyses presented in Chapters 2-4. Chapter 2 assesses the causes of cost reduction observed in PV modules since 1980. We develop a new model that identifies the causes of improvement at the engineering level and links these to higher-level mechanisms such as economies of scale. The methodology advanced can be used to evaluate the causes of improvements in any technology. By developing a model of PV modules, we find that in the early stages of the technology (1980-2001), improvements in the material usage and module conversion efficiency played an important role in reducing module cost. These improvements were mainly driven by research and development (R&D) efforts. As the PV technology matured (2001-2012), economies of scale from larger manufacturing plants resulted in significant gains. Both market-expansion policies and public R&D stimulated cost reduction, with the former contributing the majority of the cost decline from 1980 to 2012. Chapter 3 turns to assessing the materials constraints to PV cost reduction. We ask how fast metals production should be scaled up to match the increasing demand by the PV sector, if installations grow to meet a significant portion of energy demand. Unlike previous studies, which primarily used inherently uncertain factors such as reserves to estimate limits to technology scalability, we use past growth rates of a large set of metals as a benchmark for future growth rates. This analysis shows that thin-film PV technologies such as CIGS and CdTe that employ rare metals would require unprecedented growth rates in metals production even for the most conservative PV growth scenarios. On the other hand, crystalline silicon PV can provide 100% of global electricity without silicon exceeding the historical growth rates observed by all metals in the periodic table. Chapter 4 assesses the risks that material inputs bring to technologies today. This study develops cost-riskiness metrics based on the price behavior of metals along two dimensions: average price and price volatility. We first compare a large set of metals using these cost-riskiness metrics. We observe that metals obtained as byproducts have higher risk than major metals. We then apply these metrics to different PV technologies by treating them as a portfolio of metals. We find that designs such as CIGS and CdTe, which use byproduct metals with high average prices and price volatilities, show signals of cost-riskiness. The approach advanced here can serve as an assessment of the cost-riskiness of technologies introduced by their materials inputs.
by Goksin Kavlak.
Ph. D. in Engineering Systems
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Sussman, Jason M. (Jason Michael). "Reducing recombination in organic photovoltaics." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/69673.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2011.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 55-65).
In this thesis, I consider two methods to improve organic photovoltaic efficiency: energy level cascades and promotion of triplet state excitons. The former relies on a thin layer of material placed between the active layers of a photovoltaic device to destabilize excitons. If the interfacial material is chosen properly, it can significantly improve device performance. The second method proposes to use quantum mechanical rules to reduce the rate of loss in organic photovoltaic devices. An electron in a triplet state cannot directly drop to the ground state by emitting a photon, so triplet excitons have longer lifetimes, and are thus more likely to diffuse to an interface to be dissociated. But this work suggests that, once they are at the interface, they are less likely to be dissociated than a singlet.
by Jason M. Sussman.
S.M.
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Blondel, Paul. "Photovoltaics in positive energy buildings." Thesis, KTH, Tillämpad termodynamik och kylteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-181961.
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This paper deals with the usage of photovoltaics in positive energy buildings. The European Union published in 2010 a directive about the energy performance of buildings in which article 9 states that all member States shall ensure that by the end of 2020 all new buildings should be “nearly zero-energy” buildings (by the end of 2018 for public buildings). This kind of nearly zero-energy buildings is starting to develop in France under the name “BEPOS” (which stands for POSitive Energy Building, in French), and this is the name that will be used in this document. 288 projects have been certified “BEPOS” as of 2012, according to the ADEME which published a map of all the BEPOS buildings in France (the ADEME is a French agency for the environment and the energy utilization, which is a major actor in the French energy policy, often deciding where to allocate funds). To be a BEPOS, these buildings need to produce electricity on site and photovoltaics are often considered as one of the most mature and competitive technology to do so, also the most used. The purpose of this study is to demonstrate that photovoltaics are an economically viable means to reach the BEPOS quality label, and to provide data to quantify the cost and performance of a photovoltaic system. To achieve that, the technological and market conditions of photovoltaics in France are reviewed, and techno-economic calculations are made using data provided by solar and construction companies.
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Saravanapavanantham, Mayuran. "Large-area lightweight organic photovoltaics." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/128347.
Full textAbstract:
Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, February, 2020Cataloged from PDF version of thesis.
Includes bibliographical references (pages 75-77).
Lightweight conformable electronics enabled by organic materials and thin-film processing techniques present an avenue towards novel device applications. Imperceptible integration of such devices presents an opportunity towards reimagining how any surface around us can be made electronically active for purposes of sensing, computing, lighting, energy-harvesting, sound generation, etc. Critical to this would be availability of manufacturing techniques amenable for large-area coverage and material sets with sufficient mechanical resilience to withstand day-to-day human handling. Herein, we present vapor-deposited fabrication of large-area ultra-lightweight organic photovoltaics, reinforcement of such large-area devices with lamination to light weight composite fabrics, and present solution-coating approaches of organic photovoltaics as a step towards realizing all-printed lightweight electronics. Solution-coated devices are also evaluated for their use in low-light performance for indoor energy-harvesting applications.
by Mayuran Saravanapavanantham.
S.M.
S.M. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science
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Zacco, Gabriele. "Plasmonic Nanostructures for Enhanced Photovoltaics." Doctoral thesis, Università degli studi di Padova, 2012. http://hdl.handle.net/11577/3422189.
Full textAbstract:
The aim of this work is to investigate the role of optical resonances supported in different layouts of solar cells integrating metallic plasmonic gratings. A simplified ideal model was first developed in order to clarify the role and the potentialities that all the optical resonances involved in such structures have in remodulating light absorption. In a further analysis, a global optimization of both geometrical parameters of the grating (period, thickness, slit width) as well as the dielectric environment has been performed, considering different solar cell layouts, in order to obtain a gain in absorption over the widest bandwidth of solar spectrum. Following the simulation and optimization results, a nanofabrication process for the integration of metal nanostructures on top of large area c-Si solar cells has been designed. A new Laser Interference Lithography system, useful for the fabrication of large area plasmonic structures has been designed, constructed and tested. Several processes have been designed and performed and new materials have been also developed (e.g. Hybrid Organic-Inorganic solgel sinusoidal gratings). System performances are still growing toward the control of the full set of geometric parameters of the structures that can be fabricated. After nanofabrication, performances of solar cells integrating plasmonic crystals have been verified by electro-optic characterizations. Polarization resolved Specular Reflectance measurements of patterned solar cell samples were performed and results validate the model. Figures of merit of devices integrating plasmonic crystals, current density (JV) as well as External Quantum Efficiency (EQE), have been also measured. JV characteristics show a significant improvement in conversion efficiency for cells integrating the Ag nanostructures compared to flat reference cells. Such improvement is mainly due to the enhancement in short circuit current due to the light trapping effect provided by the plasmonic crystals. The EQE spectra of cells with gratings show an enhancement in near infra-red response for TM polarization, as expected from optical simulations, and also an unexpected measured improved absorption in the visible. The latter is a further indication of effectiveness of plasmonic nanostructures in light harvesting.Negli ultimi anni, la comunità scientifica ha largamente riconosciuto la possibilità di impiegare i fenomeni legati alle risonanze plasmoniche nei metalli, sfruttandone le particolari caratteristiche per il miglioramento delle performance di dispositivi optoelettronici. Tali soluzioni sono spesso ampiamente vantaggiose, ad esempio nel campo della sensoristica, in termini di miglioramento dell’efficienza nella rivelazione di specie chimiche e biologiche. Un altro campo di crescente attenzione è l’applicazione delle plasmonica al fotovoltaico. In tal caso, la capacità dei reticoli plasmonici di rimodulare lo spettro della radiazione solare incidente consente di migliorare l’efficienza di conversione energetica. In questo contesto si colloca questo lavoro, incentrato nel corso di questi tre anni, nello studio, nella realizzazione e nella caratterizzazione di reticoli plasmonici con l’intento di integrarli in dispositivi più complessi, come le celle fotovoltaiche a silicio cristallino. In primo luogo, si è proceduto sviluppando un modello semplificato di reticolo metallico, posto al di sopra di uno strato semi-infinito di silicio, al fine di chiarire il ruolo e le potenzialità delle risonanze ottiche che si generano quando il dispositivo viene irradiato dall’alto da una sorgente monocromatica polarizzata. Successivamente, è stata condotta una ulteriore analisi di ottimizzazione globale dei parametri geometrici e dei materiali su diverse configurazioni di celle solari, al fine di individuare le caratteristiche tecniche migliori che garantissero un guadagno in assorbimento, integrato sulla più ampia porzione di spettro solare. Le fasi di simulazione e ottimizzazione sono state infine seguite dal design di un processo di nanofabbricazione che permettesse l’integrazione delle nanostrutture metalliche ottimizzate su celle solari a silicio cristallino. Parte del lavoro è stato mirato alla progettazione e realizzazione di un sistema di litografia per la nanofabbricazione di reticoli plasmonici su grandi aree, chiamato Litografia Interferenziale che, dai primi mesi del 2010 è operativo presso l’Istituto IOM – CNR di Trieste. Mediante l’utilizzo di questa tecnica sono stati messi a punto diversi processi di nanofabbricazione, tra i quali quello per la realizzazione di reticoli con profilo sinusoidale e la loro integrazione in un biosensore per la rivelazione di DNA e lo studio delle potenzialità in termini litografici di materiali di tipo solgel ibridi organici\inorganici. Il processo per la realizzazione dei reticoli sulle celle solari è stato messo a punto e i campioni realizzati sono stati analizzati mediante misure morfologiche (SEM, AFM) e ottiche. Infine, le celle solari ottenute sono state caratterizzate mediante le misure delle principali figure di merito, tra cui le caratteristiche di densità di corrente-tensione (JV) e l’efficienza quantica esterna (EQE). Dalle misure JV è stato riscontrato un significativo aumento di efficienza per le celle integranti i reticoli plasmonici, in confronto a quelle convenzionali usate come riferimento, principalmente dovuto all’aumento della densità di corrente di corto circuito. Gli spettri di EQE mostrano un aumento nella regione del vicino infrarosso, per luce incidente polarizzata in modo tale da eccitare anche risonanze plasmoniche, come atteso dai risultati del modello sviluppato. I risultati raggiunti e presentati in questa tesi dimostrano l’effettiva possibilità dell’uso di nanostrutture metalliche per il rimodulazione e altresì il controllo del fenomeno di assorbimento della luce all’interno delle celle fotovoltaiche a silicio cristallino. I risultati soddisfano ampiamente le ipotesi in quanto aprono una nuova frontiera per l’applicazione anche ad altri tipologie di celle quali ad esempio quelle a film sottile o organiche. In tali dispositivi, infatti, la riduzione del materiale assorbente, al fine di massimizzare la raccolta della carica e di ridurre i costi, rende di primaria importanza la ricerca di queste nuove soluzioni per il miglioramento dell’assorbimento della luce. La direzione verso cui si stanno concentrando enormi sforzi di ricerca negli ultimi anni è quella della realizzazione di dispositivi “spessi dal punto di vista della luce incidente e sottili per la raccolta della carica generata”.
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Howells, Calvyn T. "Material and device design for organic photovoltaics." Thesis, University of St Andrews, 2015. http://hdl.handle.net/10023/6810.
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This thesis presents novel materials for photovoltaic conversion. The materials described are solution-processable organic semiconductors and have been used in the fabrication of organic photovoltaic cells (OPVs). The widely used PEDOT:PSS layer was investigated in P3HT and PTB7 photovoltaics. By doping, the efficiencies recorded were amongst the highest reported in the field using a conventional architecture. Two low band-gap BODIPY-based polymers were introduced and shown to have properties favourable for optoelectronics. Photovoltaics consisting solely of the polymers as the active component surpassed the performance expected without the use of an acceptor, indicating ambipolar behaviour, which was verified by charge carrier mobility measurements. When blended with an acceptor, the devices demonstrated a short-circuit current density similar to that of P3HT, a well-studied and successful OPV material. They also revealed a broad spectral response and were shown to operate as photodiodes. Two small molecules containing diketopyrrolopyrrole (DPP) and BODIPY were introduced and characterised. The addition of thiophenes red shifted the absorption but did not result in a sufficient bathochromic shift. Instead, a propensity to aggregate limited the performance. PLQY measurements showed the aggregation to quench luminescence. The study demonstrated the importance of controlling aggregation for efficient devices. Two solution-processable small molecules with a germanium-bridged spiro centre were investigated, and the molecular, electrochemical and optical properties discussed. The small molecule with shorter conjugation length exhibited an interesting packing motif shown to be favourable for charge transport. The mobility measurements were an order of magnitude higher than those reported for sexithiophene, a small molecule analogue, and the same order of magnitude as P3HT. The two-dimensional charge transporting nature of the material was verified with two independent techniques: time of flight (TOF) and organic field-effect transistor (OFET) measurements. The mobility of the material was found to vary with annealing, a result of morphological changes. These were studied with optical, electron and scanning probe microscopies. By controlling the morphology with the implementation of a well-defined annealing method, it was possible to improve the performance of OFETs and planar-heterojunction OPVs. Solution-processed bulk-heterojunction OPVs were fabricated, characterised and optimised with Ge spiro molecules. A PCE similar to that of P3HT, 2.66 %, was achieved for the one, whilst a PCE of 1.60 % was obtained for the other. The results are encouraging, and there is scope for improvement by increasing the overlap between the absorption and solar spectrum, for example.
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Tominaga, Miwa. "Opportunities for thin film photovoltaics in Building Integrated photovoltaics (BIPV)with a focus on Australia." Thesis, Tominaga, Miwa (2009) Opportunities for thin film photovoltaics in Building Integrated photovoltaics (BIPV)with a focus on Australia. Masters by Coursework thesis, Murdoch University, 2009. https://researchrepository.murdoch.edu.au/id/eprint/2081/.
Full textAbstract:
Building Integrated Photovoltaic (BIPV) products can not only generate electricity but also provide structural stability, thermal insulation, shading, natural lighting, protection from water and other elements. Thin film photovoltaic cells are favoured over crystalline cells in BIPV applications, due to their physical flexibility, wide ranging options for installation, comparably low cost and aesthetics. Of the total worldwide PV market, thin film technologies contribute only about 10%. However, this is set to change.
Third generation thin film PV has the advantages of their flexible substrate and the ability to perform in dim or variable lighting. Their low temperature roll-to-roll manufacturing methods make them economical for large surface areas such as BIPV roofing and facades. First and second generation PV have proven themselves in BIPV installations in products such as tiles, laminates, slates and glazing. Much excitement surrounds Canberra based thin film solar cell company Dyesol and their partnership with strip steel sheeting manufacturers Corus. Together they plan to provide the world with a possible 35GW of BIPV generated energy per annum.
There is great potential for BIPV in Australia, with the average Australian residential household being able to generate almost three times their average daily energy use. The $/m2 costs for BIPV products in Australia are fast approaching cost competitiveness with conventional building materials. Some types of thin film PV have already broken through the $1/W manufacturing cost barrier and are speeding towards grid parity with conventional fossil fuel generated electricity. However, there are still many barriers to increasing the use of BIPV which must also be addressed.
Government support is critical for BIPV to achieve the potential that it can and to create a level playing field against Australia's well established coal and fossil fuel industries. Some of the measures that the Australian government could introduce in support of BIPV are:
• One Australia-wide gross feed-in tariff with extra incentives for BIPV generated electricity, paying 5times the standard rate for electricity. This would also remove the administrative burden on state and territory governments, each with different schemes.
• Mandate for all new buildings to be zero emissions by 2016.
• Encourage the use of on-site renewables.
• Fund large-scale public projects to showcase the BIPV technology.
• Support and coordinate with independent regulators so the approval process for the importation of BIPV products is transparent and straight forward.
• Provide educational programs that train architects and builders to design BIPV installations.
• Fund R&D into thin-film PV technologies and their commercialisation in BIPV applications.
• Support cooperation between BIPV manufacturers and others in the value chain.
• Support the PV manufacturing industry to attract new facilities to Australia. This provides more green jobs, a highly skilled workforce and supports the PV industry for future generations.
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Ho, Andrea. "Creating preliminary specifications for printed photovoltaics." Click here to view, 2010. http://digitalcommons.calpoly.edu/grcsp/16/.
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Thesis (B.S.)--California Polytechnic State University, 2010.Project advisor: Malcolm Keif. Title from PDF title page; viewed on Apr. 20, 2010. Includes bibliographical references. Also available on microfiche.
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Thomsen, Elizabeth Alice. "Characterisation of materials for organic photovoltaics." Thesis, St Andrews, 2008. http://hdl.handle.net/10023/462.
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Dörling, Bernhard. "Conjugated materials for thermoelectrics and photovoltaics." Doctoral thesis, Universitat Autònoma de Barcelona, 2017. http://hdl.handle.net/10803/405360.
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Esta tesis explora cómo las interacciones entre materiales orgánicos pueden ser aprovechadas para obtener funcionalidad adicional de una manera sencilla, sin necesidad de procesamiento complejo. Los resultados obtenidos tienen aplicaciones en el campo de la fotovoltaica y termoeléctrica orgánica.
El trabajo se centra en materiales tales como polímeros conjugados y nanotubos de carbono, y procesos de deposición desde disolución simples, como el recubrimiento por cuchilla.
La primera parte presenta resultados sobre la caracterización elipsométrica de las propiedades ópticas de los polímeros conjugados y sus mezclas con fullerenos o dopantes. La elipsometría espectroscópica de ángulo variable se utilizó no sólo para caracterizar las constantes ópticas de nuevos polímeros altamente absorbentes, sino también para investigar el efecto de los aditivos disolventes sobre el grado de segregación vertical de fase en mezclas de polímero:fullereno.
La segunda parte detalla el trabajo sobre nanocompuestos de polímeros conjugados y nanotubos de carbono, una prometedora clase de materiales termoeléctricos orgánicos. Debido a que los polímeros conjugados permiten desenredar los manojos de nanotubos de carbono de manera eficiente, estos nanocompuestos se pueden preparar fácilmente. Presentan tanto una buena conductividad eléctrica como una baja conductividad térmica, que son requisitos necesarios para un buen rendimiento termoeléctrico.
De particular interés son los compuestos de tipo n que contienen nanotubos de carbono dopados con nitrógeno, así como métodos de procesamiento que permiten cambiar el tipo de portador mayoritario.
La tercera parte se centra en técnicas sencillas de fabricación de dispositivos fotovoltaicos orgánicos, con el objetivo particular de obtener capas orientadas de polímeros conjugados.
Esto se logró controlando localmente la evaporación del disolvente para influir en la cristalización epitaxial direccional de polímeros conjugados en un aditivo disolvente cristalino.
El método desarrollado permite preparar dos tipos distintos de películas.
Si la nucleación del aditivo se limita a la línea de contacto unidimensional durante el recubrimiento con cuchilla, se obtienen entonces películas uniaxialmente orientadas con una morfología fibrilar.
Al limitar la nucleación a un punto, se puede crecer una superestructura cristalina circular conocida como esferulita en cualquier lugar deseado de la película.
Los dispositivos fotovoltaicos orgánicos que se prepararon a partir de estas películas orientadas tienen aplicaciones como detectores del estado de polarización de la luz.This thesis explores ways of how interactions between organic materials can be exploited to obtain additional functionality in a simple manner, without the need for complex processing. The obtained results have applications in the field of organic photovoltaics and thermoelectrics. The work focuses on materials such as conjugated polymers and carbon nanotubes, and simple solution-based deposition processes such as blade coating. The first part presents results on the ellipsometric characterization of the optical properties of conjugated polymers and their blends with fullerenes or dopants. Variable angle spectroscopic ellipsometry was used not only to characterize the optical constants of new, highly absorbing polymers, but also to investigate the effect of solvent additives on the degree of vertical phase segregation in polymer:fullerene blends. The second part details the work on nanocomposites of conjugated polymers and carbon nanotubes, a promising class of organic thermoelectric materials. Because conjugated polymers allow for efficient debundling of carbon nanotubes, these nanocomposites can be prepared readily. They exhibit both a good electrical conductivity and a low thermal conductivity, which are necessary requisites for good thermoelectric performance. Of particular interest are n-type composites containing nitrogen-doped carbon nanotubes, as well as processing methods that allow to change the majority carrier type. The third part focuses on simple fabrication techniques for organic photovoltaic devices, with the particular objective of obtaining oriented layers of conjugated polymers. This was achieved by locally controlling solvent evaporation to influence the directional epitaxial crystallization of conjugated polymers on a crystalline solvent additive. The developed method allows to prepare two distinct types of films. If the nucleation of the additive is confined to the one-dimensional contact line during blade-coating, then uniaxially oriented films with a fibrillar morphology are obtained. By confining the nucleation to a point, a circular crystalline superstructure known as a spherulite can be grown at any desired location in the film. The organic photovoltaic devices that were prepared from these oriented films have applications as detectors of the polarization state of light.
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Löper, Philipp [Verfasser]. "Silicon Nanostructures for Photovoltaics / Philipp Löper." Aachen : Shaker, 2014. http://d-nb.info/1053904584/34.
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Gianferante, Nicholas F. (Nicholas Frank) 1964. "The application of photovoltaics for buildings." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/80151.
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Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1999.Includes bibliographical references (leaves 83-84).
by Nicholas F. Gianferante.
M.Eng.
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Schmidt-Mende, Lukas Johannes. "Photovoltaics from discotic liquid crystalline materials." Thesis, University of Cambridge, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620728.
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Stec, Helena M. "Metal window electrodes for organic photovoltaics." Thesis, University of Warwick, 2013. http://wrap.warwick.ac.uk/57652/.
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The work presented in this thesis focuses on the development ultra-thin metal film electrodes for organic photovoltaics (OPVs) with the aim of boosting device performance, lowering the cost and/or extending the range potential application. Chapter 1 gives a general overview of OPVs, including the materials used for their fabrication and the fundamental processes underpinning OPV’s operation. The experimental techniques and equipment used are described in Chapter 2. Chapter 3 describes the development of a solvent free method for the fabrication of highly transparent ultra-thin Au films on glass based on co-deposition of a mixed molecular adhesive layer prior to Au thermal evaporation. By integrating microsphere lithography into the fabrication process the transparency could be improved via the incorporation of a random array of micron-sized circular apertures into the film. In Chapter 4 it is shown that these films are amenable to rapid thermal annealing to realise highly crystalline window electrodes with improved transparency and conductivity. By capping these films with a very thin transition metal oxide layer their thermal stability can be dramatically improved, whilst at the same time improving their far field transparency. In Chapter 5 the molecular adhesive method for the fabrication of ultra-thin Au films on glass is translated to the technologically important flexible substrates and extended to the lower cost coinage metals Ag and Cu. In Chapter 6 a lithography-free approach to fabricating thin Au and Ag films with a dense array of sub-wavelength apertures is reported. These electrodes support surface plasmon resonances which couple strongly with visible light concentrating it near to the electrode surface, thereby increasing light harvesting. Chapter 7 shows how the electrodes developed in Chapter 3 can be used to investigate a fundamental question of importance in OPV research and indicates the direction of future work. The results of chapters 3, 5 and 6 have been published in peer reviewed scientific journals.
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Pegg, Lara-Jane. "Controlling hole extraction in organic photovoltaics." Thesis, University of Warwick, 2012. http://wrap.warwick.ac.uk/55114/.
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The work in this thesis focuses on the process of hole extraction in OPVs both in terms of the development of new hole extracting materials and understanding the factors that determine the efficiency of hole extraction to enable the intelligent design of these electrodes. In Chapter 1 an overview of organic semiconductors and organic photovoltaic (OPV) devices is given including details of the fundamental processes that underpin the operation of OPVs. In Chapter 2 an overview of the experimental techniques used in this thesis is presented. Chapter 3 reports the use of surface oxidised Au nanoparticles (AuNPs) as an efficient hole-extracting material in molecular OPVs. This class of hole-extracting material is unusual in that it is remarkably effective even at low surface coverage and offers the advantage over conventional hole-extracting materials of solution processing from a pH neutral solution. The effectiveness of oxidised AuNPs as a hole extracting material is attributed to the very high work function of these particles and geometric electric field enhancement effects. Chapters 4 and 5 describe experiments designed to determine how nanoscale geometric electric field enhancement and electrode work function affects the efficiency of hole-extraction in OPVs, respectively. From these latter chapters generic electrode design rules are proposed. Finally, in Chapter 6 an overview of future work is given. With the exception of the final part of Chapter 5, the results of chapters 3, 4 and 5 have been published in peer reviewed scientific journals.
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Lafta, Abbas Jassim Attia. "New materials for photocatalysis and photovoltaics." Thesis, University of Glasgow, 2013. http://theses.gla.ac.uk/4105/.
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Photocatalytic processes are of widespread interest. Among different types of photocatalytic material TiO2 is the generally considered amongst the best due to its favourable physical and chemical properties. In recent decades, photovoltaic devices have been widely studied to provide alternative routes to energy and reduce dependency upon fossil fuel. Solar photovoltaic are cells capable of harvesting of sunlight into electrical power. This technology is one of the most promising routes in the search for sustainable and renewable sources of energy. The study presented in this thesis relates to the preparation and characterization of a range of different materials which can be applied in photocatalytic processes and for photovoltaic devices. The photocatalysis work has been focused mainly upon modification of the various phases of titanium dioxide. This has been undertaken via doping with nitrogen by treatment with ammonia at different temperatures. In addition, samples containing Al, Co and Cu dopants, as well as their N doped counterparts, have been prepared, characterized and tested. The photocatalytic activity was screened by following photocatalytic decomposition of an aqueous solution of methylene blue using a light source containing various components in the UV and visible regions. For selected samples, the photocatalytic activity for polymerization of methyl methacrylate and styrene has been determined with the aim of producing composites. In terms of potential photovoltaic materials, the synthesis of novel viologen compounds and polymerization via electrochemical and chemical means has been undertaken. Different viologen monomers have been synthesized with various moieties in conjugation to a phenanthroline core to afford novel push-pull systems. These compounds have incorporated both TCNE and TCNQ moieties as strong electron acceptors and hence yield chromophore with large dipole moments. In addition, novel ruthenium complexes were prepared featuring bipyridine and phenanthroline ligands. The optical and redox properties of these materials have been investigated. DSSCs have been fabricated form some of these systems and their properties have been compared to dye 719.
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Sutton, Rebecca J. "Towards stable perovskite materials for photovoltaics." Thesis, University of Oxford, 2018. http://ora.ox.ac.uk/objects/uuid:4cc567a2-9c2f-44c8-9fdf-b2d0493683d3.
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This thesis explores a range of photoactive metal halide perovskite materials for use in photovoltaic applications. These materials are of huge interest due to their outstanding optoelectronic properties which result in high photovoltaic power conversion efficiencies. In particular, this thesis discusses perovskites with stoichiometry ABX3 where A is a singly charged cation, for example methylammonium (MA), B is predominantly lead (Pb2+), and X is iodide (I-) and/or bromide (Br-). At present the commercial applications of these materials are limited by the chemical instability of the A-site cation. In this thesis, the effect of chemical substitution of the A-site is investigated as a way to increase the stability of the perovskite material. Full replacement with the inorganic cation caesium (Cs+) is shown to significantly improve the chemical stability. However, the inorganic lead halide perovskites with ideal bandgaps for photovoltaic applications exhibit structural instability. Routes to achieve both chemical and structural stability for these perovskites are discussed. Consequently, this thesis represents pioneering work in the field of inorganic halide perovskites and will greatly assist the development of stable inorganic perovskite materials for optoelectronic applications such as tandem photovoltaics and LEDs. Chapters 1 and 2 of this thesis present the motivation for perovskite materials to be used in solar cells, along with relevant background information about these materials and solar cell operation in general. Chapter 3 details the methods utilised in the experimental results chapters which follow. The first experimental results chapter, Chapter 4, shows how incorporation of Br- in place of I- in CsPbI3 leads to increased ambient stability of the perovskite structure, and the first solar cells with CsPbI2Br as the absorbing photovoltaic material are reported. Chapter 5 remedies the deficit of information about the optoelectronic properties of the CsPbI3-xBrx (0 ≤ x ≤ 3) perovskites through magneto-optical measurements on thin-films. These measurements raise questions about the room temperature perovskite structure of the CsPbI3-xBrx compositions with small x, previously thought to be cubic perovskite, which is shown in Chapter 6 to be an orthorhombic perovskite polymorph. This finding motivates preliminary work presented in Chapter 7 aimed at chemical stabilisation of this orthorhombic perovskite polymorph. Finally, Chapter 8 summarises the work presented in this thesis, and recommends further research for the development of stable perovskite materials for photovoltaics.
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Kaplan, Abram Walden. "Energy Sustainability: The Case of Photovoltaics." Oberlin College Honors Theses / OhioLINK, 1985. http://rave.ohiolink.edu/etdc/view?acc_num=oberlin1503314549048876.
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Yi, Chao. "SOLUTION-PROCESSED POLYMERIC THERMOELECTRICS AND PHOTOVOLTAICS." University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1472639791.
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Hutter, Oliver S. "Nanostructured copper electrodes for organic photovoltaics." Thesis, University of Warwick, 2015. http://wrap.warwick.ac.uk/71005/.
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This thesis describes a body of original research focused on the development of a viable alternative to the indium-tin oxide (ITO) glass window electrode used in organic photovoltaic (OPV) devices, based on the use of ultra-thin Cu films. The first results chapter describes a low cost, robust Cu | Al bilayer window electrode that simultaneously functions as the low work function electron-extracting electrode and as a sink for oxygen/water molecules in OPVs. When the electrode is exposed to air, an ultra-thin oxide layer forms at its surface without any increase in surface roughness, and the sheet resistance of the electrode actually decreases. However, this electrode has the disadvantage of a lower far-field transparency than ITO glass. The second results chapter describes how the transparency of ultra-thin Cu films can be increased to a level comparable to that of ITO glass across most of the spectrum over which OPVs harvest light using an overlayer of tungsten sub-oxide (WO3-x) which is spontaneously doped with Cu, increasing both its refractive index and electrical conductivity. Unfortunately these electrodes are not air stable. The third results chapter describes how the developments described in the previous two chapters might be integrated to realise an electrode that is both air-stable and highly transparent. The final results chapter describes a very different approach to coupling light into an OPV based on a Cu electrode with a dense array of sub-optical wavelength apertures. These electrodes absorb light strongly, concentrating it as surface plasmon excitations. It is shown that this trapped light can be absorbed by the light harvesting organic semiconductor in organic photovoltaics so that electrodes with very low far-field transparency can perform as well as more transparent electrodes.
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Bristow, Noel. "Outdoor stability studies in organic photovoltaics." Thesis, Bangor University, 2017. https://research.bangor.ac.uk/portal/en/theses/outdoor-stability-studies-in-organic-photovoltaics(47de6824-7d4f-4d3c-8b00-82704f252d45).html.
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This thesis focuses on the outdoor monitoring of organic photovoltaics (OPVs) with the aim of improving the stability and performance of OPVs under real world conditions. This is important as in order for OPVs to become commercially viable they must make the transition from small laboratory cells to larger modules. Over the course of several outdoor monitoring campaigns various types of OPV modules have been benchmarked against a number of other technologies: polycrystalline silicon, cadmium indium diselenide and dye sensitised solar cells. The principal performance parameters are examined in detail, analysing their dependence on irradiance and temperature. OPVs were shown to have positive temperature coefficients for efficiency, ISC and fill factor and a negative temperature coefficient for VOC. One of the main causes of degradation is ingress of water and oxygen into the module and subsequent photo-oxidation of the active layer and it was shown that UV filtering would improve stability. To improve the yield of OPVs outdoors, modules were laminated to different corrugated substrates and subjected to indoor characterisation and outdoor monitoring. The corrugated modules were shown to have three advantages: the effective area of the module, allowing for curvature, is reduced which leads to an improvement in the power conversion efficiency per unit area; substantial enhancement at high angles of incidence led to increased output during early morning and evening; under diffuse irradiance performance improved by up to 25%. Outdoor measurements on larger module strips showed that corrugated strips outperformed flat strips by 7.5% with a 14.8% enhancement under diffuse conditions. An alternative technique to improve the yield of OPVs is the use of luminescent down-shifting coatings which were investigated as alternatives to UV filters and have the added benefit of improving stability. The use of both discrete and multiple-dye blends dispersed in poly(methyl methacrylate) led to improvements in performance of up to 8% and a six-fold extension of operational lifetime. Dyes were systematically selected by examining their absorption and photoluminescence spectra and matching these to the spectral performance of P3HT:PC61BM OPV devices. In doing so optimised multiple-dye blends were made possible.
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Yandt, Mark. "Characterization and Performance Analysis of High Efficiency Solar Cells and Concentrating Photovoltaic Systems." Thesis, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/20535.
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As part of the SUNRISE project (Semiconductors Using Nanostructures for Record Increases in Solar-cell Efficiency), high efficiency, III-V semiconductor, quantum-dot-enhanced, triple-junction solar cells designed and manufactured by Cyrium Technologies Inc. were integrated into OPEL Solar, MK-I, Fresnel-lens-based, 550x concentrating modules carried on a dual axis tracker.
Over its first year of operation 1.8 MWh of AC electrical energy was exported to the grid. Measurements of the direct and indirect components of the insolation, as well as the spectral irradiance of light incident on the demonstrator in Ottawa, Canada are presented. The system efficiency is measured and compared to that predicted by a system model to identify loss mechanisms so that they can be minimized in future deployments.
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Wu, Yuechen, and Raymond K. Kostuk. "Two-junction holographic spectrum-splitting microconcentrating photovoltaic system." SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS, 2017. http://hdl.handle.net/10150/623284.
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Spectrum-splitting is a multijunction photovoltaic technology that can effectively improve the conversion efficiency and reduce the cost of photovoltaic systems. Microscale PV design integrates a group of microconcentrating photovoltaic (CPV) systems into an array. It retains the benefits of CPV and obtains other benefits such as a compact form, improved heat rejection capacity, and more versatile PV cell interconnect configurations. We describe the design and performance of a two-junction holographic spectrum-splitting micro-CPV system that uses GaAs wide bandgap and silicon narrow bandgap PV cells. The performance of the system is simulated with a nonsequential raytracing model and compared to the performance of the highest efficiency PV cell used in the micro-CPVarray. The results show that the proposed system reaches the conversion efficiency of 31.98% with a quantum concentration ratio of 14.41x on the GaAs cell and 0.75x on the silicon cell when illuminated with the direct AM1.5 spectrum. This system obtains an improvement over the best bandgap PV cell of 20.05%, and has an acceptance angle of +/- 6 deg allowing for tolerant tracking. (C) 2017 Society of Photo-Optical Instrumentation Engineers (SPIE)
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Kijovský, František. "Fotovoltaický on-grid systém s akumulací." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2012. http://www.nusl.cz/ntk/nusl-219414.
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This thesis deals with processing the current issue of trends in on-grid photovoltaic system with accumulation. It examines the posibility of accumulation of photovoltaic systems, analyzing their strengths and weaknesses in the practical deployment. It compares the different storage technologies based on indicators of cycles, durability and price ranges. The practical part deals with the technical design of hybrid power system and then comparing with the standard on-grid system in technical and economical point of view.
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Dvořák, Vít. "Návrh fotovoltaické elektrárny pro rodinný dům v okrese Jihlava." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2021. http://www.nusl.cz/ntk/nusl-442514.
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This diploma thesis deals with the design of a photovoltaic solar power station for a specific family house in the Jihlava region. The aim of the work was to get acquainted with technologies about the production of solar systems, evaluate the market in the Czech Republic and create a design of photovoltaic solar power station. Three designs of power stations were created with the help of the PV * SOL design system. Each design uses different photovoltaic cell technology. The result of each power station design is a complete finished project, which is based on many factors such as the efficiency of the entire system in a certain location, financial analysis, return on investment and more. In addition, these projects meet the conditions for the preparation of the subsidy program Nová zelená úsporám. At the end of the work, all three designed power stations are evaluated and with the help of multicriteria analysis, the best and most advantageous power station design for the given locality is determined. In the end, the idea of further development of the project is presented.
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Annegren, Emma, David Hällqvist, and Salander Karin. "Optimization of a Photovoltaic System at an Office Complex : A Case Study of Photovoltaics at PLAN4 Uppsala Sweden." Thesis, Uppsala universitet, Institutionen för teknikvetenskaper, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-225560.
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Photovoltaics is a method for converting sunlight into electricity by using PV devices. This report focuses on a pilot project of a PV system installed at the rooftop of an office complex, PLAN4 in Uppsala. The PV system has been evaluated with respect to the produced electricity and economic profitability. The report examines the possibility to optimize the facility in order to better match the electricity load profile at PLAN4. The optimization is done by changing the tilt angle and azimuth of the modules. A comparison between the existing and an improved system is done in order to determine the best match for the electricity demand. The electric power production was calculated with simulations in the software PVSYST, based on solar irradiation data and temperature from the year 2013. The result showed that the existing system has an annual production of 28 % of the electric power used at PLAN4. However, during midday on clear days, the production sometimes exceeds the demand and the produced electric power is used by someone else in the building, and does not generate any economic value for the office. This overproduction represents 17% of the total production, resulting in a self-sufficiency of 22%. The self-sufficiency represents the share of the electric consumption that comes from the PV production, calculated on an hourly basis. An optimization of the system would result in a small increase in self-sufficiency but the excess production would increase significantly. An optimization of the system does not generate enough savings to justify the investment required, although more electric power would be produced.
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Olson, Jeremy D. "Novel photovoltaics : an introduction to basic characterization /." Diss., Digital Dissertations Database. Restricted to UC campuses, 2009. http://uclibs.org/PID/11984.
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Aeberhard, Urs. "A microscopic theory of quantum well photovoltaics /." Zürich : ETH, 2008. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17966.
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Attygalle, Muthuthanthrige Lilani C. "Theoretical modeling of polycrystalline thin-film photovoltaics /." Connect to full text in OhioLINK ETD Center, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1204144362.
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Mohamamd, Ali Mahmoudzadeh Ahmadi Nejad. "Carbon nanotubes for biomolecular sensing and photovoltaics." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/2609.
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A computational investigation of some optoelectronic applications of carbon nanotubes (CNT) is presented, including CNT-based solar cells and biosensors. The results could be used to evaluate the performance of CNT devices and clarify the necessity of further experimental research in this area. A coaxially-gated CNT field-effect transistor (CNFET) forms the basic structure of the devices modeled in this thesis. Diffusive transport is present in long-channel devices, as in our case, while the quantum mechanical effects are mainly present in the form of tunneling from Schottky-barrier contacts at the metal-CNT interfaces. Band-to-band recombination of electron-hole pairs (EHP) is assumed to be the source of electroluminescence. In a first-order approximation, protein-CNT interactions are modeled as the modification of the potential profile along the longitudinal axis of CNTs due to electrostatic coupling between partial charges, in the oxide layer of the CNFET, and the nanotube. The possibility of electronic detection is evaluated. The electroluminescence of the CNT is proposed as an optical detection scheme due to its sensitivity to the magnitude and the polarity of the charge in the oxide. The validity of the model is argued for the given models. A value for the minimum required size of a computational window in a detailed simulation is derived. The structure of an electrostatically gated p-i-n diode is simulated and investigated for photovoltaic purposes. The absorbed power from the incident light and the interaction between the nanotubes is modeled with COMSOL. The results are interpreted as a generation term and introduced to the Drift-Diffusion Equation (DDE). We have observed behavior similar to that in an experimentally-realized device. The performance of CNT-based solar cells under standard AM 1.5 sunlight conditions is evaluated in the form of an individual solar cell and also in an array of such devices.
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Eiffert, Patrina. "An economic appraisal of building-integrated photovoltaics." Thesis, Oxford Brookes University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.264530.
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Schumann, Stefan. "Interface modification in organic and hybrid photovoltaics." Thesis, University of Warwick, 2011. http://wrap.warwick.ac.uk/38432/.
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With the growing importance of organic photovoltaics (OPVs) as an attractive, low cost and sustainable energy source the field has been investigated intensively, showing high potential for commercialisation. To further improve device performance, different routes of development have been explored targeting interfaces that play a crucial role in device performance including the donor (D)/acceptor (A) and electrode/photoactive layer interfaces, as well as incorporation of new materials. Vertical co-deposition of water-soluble small molecule copper(II) phthalocyaninetetrasulfonic acid tetrasodium salt (TSCuPc) and polymeric sodium poly[2-(3- thienyl)ethoxy-4-butylsulfonate] (PTEBS) with polystyrene (PS) nanospheres to template, followed by solvent vapour sphere removal, is shown as an excellent method to generate three-dimensionally ordered macroporous large area thin films of sub-100 nm pore size. After a subsequent infiltration by the electron acceptor phenyl-C61-butyric acid methyl ester (PCBM), three-dimensionally (3D) interdigitated D-A composite structures are generated which are further implemented in complete OPV devices. PTEBS based 3D nanostructured D-A composite devices reached a comparable performance to planar reference devices but did not show the expected photocurrent improvement. This is most likely due to the complexity of this multistep fabrication method and the large probability if impurities in the films. However, it demonstrates a new approach towards nanoengineered 3D interdigitated organic D-A composite OPV devices. For this templating technique monodisperse sub-100 nm PS nanospheres were synthesised by radical initiated surfactant-free emulsion polymerisation controlling different parameters with particular focus on styrene-4-sulfonic acid sodium salt (NaSS) co-monomer concentration. Furthermore, planar heterojunction OPV devices from TSCuPc and PTEBS were studied in detail and optimised for further understanding of the 3D D-A composite devices. A substantial increase in device performance and operational stability in solution processed inverted bulk heterojunction (BHJ) OPVs is demonstrated by introducing a zinc oxide (ZnO) or titanium oxide (TiOx) interlayer between the electron collecting bottom electrode and the photoactive blend of poly(3-hexylthiophene) (P3HT) and PCBM. The introduction of transition metal oxide (TMO) interlayers resulted in a remarkable increase in power conversion efficiency (PCE) with a maximum value of 4.91 %. The structure and morphology of the dense, planar ZnO layers was controlled either by electrodeposition or spray pyrolysis techniques. Organic/inorganic hybrid OPVs combine the advantages of both types of semiconductors and offer an alternative to replace fullerene based electron acceptor materials. The small molecule organic semiconductor, boron subphthalocyanine chloride (SubPc), is a promising donor material for fabrication of inverted planar hybrid solar devices using TiOx as the electron acceptor. The TiOx/SubPc cells demonstrate performance characteristics comparable to the best-reported polymer/TiOx hybrid cells. A relatively high photocurrent and a maximum external quantum efficiency (EQE) of 20 % lead to a PCE of 0.4 % under AM1.5 solar illumination.