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Dissertations / Theses on the topic 'Electroluminescence'
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1
Mackay, Ian. "Thin film electroluminescence /." Online version of thesis, 1989. http://hdl.handle.net/1850/10551.
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O'Brien, Diarmuid Francis. "Conjugated polymer electroluminescence." Thesis, University of Sheffield, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266004.
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Greenham, Neil Clement. "Electroluminescence in conjugated polymers." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296643.
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Metsios, Ioannis. "Electroluminescence and inorganic phosphor science." Thesis, University of Hull, 2007. http://hydra.hull.ac.uk/resources/hull:5856.
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The research is focussed on wide bandgap 11-VI semiconductors, and more specifically on ZnS and CdS, with applications as thin film electroluminescent displays in the expanding display device market. The science of electroluminescent semiconductors and inorganic salt precipitation is combined with a unique, thin film laser processing technique known as laser induced forward transfer or direct writing (the later terminology used mostly in the case of metal films). Zinc sulfide and cadmium zinc sulfide films with a thickness ranging between 70 and 400 nin have been prepared in an aqueous chemical bath, on optically smooth, silica, or silica based, substrates. The chemical bath contained zinc and cadmium chlorides, thioacetamide, and urea, and the most successful combination of concentrations was found to be 2.6 mM, 56.36 mM and 167.71 mM, respectively. The solution was only slightly acidic, with a pH between 5 and 6.5, and a bath temperature of 90 to 92°C (as measured at I cm from the water surface of the bath) was found to be the most efficient. The films were doped with impurities, such as Cu, Ag and Mn in order to achieve specific luminescent characteristics. A KrF excimer laser at 248 nin was used to transfer the films from their original substrate to a new one. The laser pulse was focussed on the chemically deposited films through the back of the transparent silica substrate. The detached film was transported across a gap of 15 µm and attached to the new substrate. A fluence between 0.5 and 0.7 jCM⁻² was found to give the best transfers, and also able to achieve multiple layer transfers over the same area of the target substrate. The transfers were performed in an argon atmosphere of 4x 10⁻² mbar pressure. Ellipsometry and film reflectivity measurements were used to model and determine the film thickness of the chemically deposited films and the values obtained were confirmed by scanning electron microscopy. Ile latter, together with optical microscopy, atomic force microscopy and interferometry were exploited to investigate the structure of the chemically deposited and laser transferred films. It was found that a very thin ZnO film initially adhered to the substrate in the bath, on which the ZnS or CdZnS main film was attached as homogenously grown cluster beads or grown via ion by ion deposition. The homogeneously grown beads had a phase separation, containing the sulfide with the lowest Ksp in the centre, enclosed by highest Ksp sulfides, with the highest one as a shell. The phase separation between CuS and ZnS was also confirmed by extended X-ray absorption fine structure. The elemental composition of the chemically-prepared and laser-transferred films was investigated by energy dispersive X-ray analysis (EDX), inductively coupled plasma mass spectrometry and Raman microspectrometry, while the EDX and Raman methods also helped to confirm the phase separation between US and ZnS. Cathodoluminescence and photoluminescence measurements were employed to investigate the luminescence properties of the films, and the Mn doped films that were annealed at 700°C were found to be the most efficient cathode ray excited phosphors, while the Cu doped phosphors came next in efficiency, performing equally well under an electron or a UV laser beam (from a HeCd laser at 325 rim). Smaller luminescence peaks were also detected in Ag doped films. Transferred films showed similar luminescent properties to their original films, but with lower intensity. Thus the chemical bath deposition and laser transferring were successful, but the methods can be further improved.
5
Mills, David H. "Electroluminescence and ageing of polyethylene." Thesis, University of Southampton, 2012. https://eprints.soton.ac.uk/338950/.
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Electrical insulation is known to age when under electrical stress. One cause of this is thought to relate to the movement and build up of charge within the insulation. The emission of a low level of light from polymeric materials when under electrical stressing is shown to occur before the onset of currently detectable material degradation. This light is termed electroluminescence (EL)and under an ac electric field is thought to relate to the interaction of charge in close proximity to the electrode-polymer interface. Understanding the cause of this light emission gives a very high resolution way of monitoring charge interaction and its influence on material ageing. This report presents the improvement to a system to measure changes in EL emission during the cycle of the applied field (point on wave measurements) under various electric fields. To investigate the relationship between EL and ageing, 100 �m, low-density polyethylene (LDPE) films were ultraviolet (UV) aged in 3 and 7 day intervals up to 17 days. The samples were aged in both air and nitrogen environments to separate the affect of photo-oxidation from photo irradiation reactions on charge movement. Changes as a result of ageing were characterised in terms of optical, chemical and electrical properties. These were investigated using ultraviolet and visible (UV-Vis) and Fourier transform infrared (FTIR) spectroscopy, ac ramp breakdown measurements and dielectric spectroscopy. The accumulation of space charge (SC) was then investigated using the pulsed electro acoustic (PEA) technique. This collection of results were used to explain changes in EL in terms of intensity and phase difference. A model using the bipolar charge recombination theory was then developed using trends shown in the characterising measurements to explain changes in EL. Results support the use of EL as a tool to investigate changes in charge movement very near the electrode-polymer interface.
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Weaver, Michael Stuart. "Electroluminescence from organic light emitting diodes." Thesis, University of Sheffield, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265610.
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Bedrich, Karl G. "Quantitative electroluminescence measurements of PV devices." Thesis, Loughborough University, 2017. https://dspace.lboro.ac.uk/2134/27303.
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Electroluminescence (EL) imaging is a fast and comparatively low-cost method for spatially resolved analysis of photovoltaic (PV) devices. A Silicon CCD or InGaAs camera is used to capture the near infrared radiation, emitted from a forward biased PV device. EL images can be used to identify defects, like cracks and shunts but also to map physical parameters, like series resistance. The lack of suitable image processing routines often prevents automated and setup-independent quantitative analysis. This thesis provides a tool-set, rather than a specific solution to address this problem. Comprehensive and novel procedures to calibrate imaging systems, to evaluate image quality, to normalize images and to extract features are presented. For image quality measurement the signal-to-noise ratio (SNR) is obtained from a set of EL images. Its spatial average depends on the size of the background area within the EL image. In this work the SNR will be calculated spatially resolved and as (background independent) averaged parameter using only one EL image and no additional information of the imaging system. This thesis presents additional methods to measure image sharpness spatially resolved and introduces a new parameter to describe resolvable object size. This allows equalising images of different resolutions and of different sharpness allowing artefact-free comparison. The flat field image scales the emitted EL signal to the detected image intensity. It is often measured through imaging a homogeneous light source such as a red LCD screen in close distance to the camera lens. This measurement however only partially removes vignetting the main contributor to the flat field. This work quantifies the vignetting correction quality and introduces more sophisticated vignetting measurement methods. Especially outdoor EL imaging often includes perspective distortion of the measured PV device. This thesis presents methods to automatically detect and correct for this distortion. This also includes intensity correction due to different irradiance angles. Single-time-effects and hot pixels are image artefacts that can impair the EL image quality. They can conceivably be confused with cell defects. Their detection and removal is described in this thesis. The methods presented enable direct pixel-by-pixel comparison for EL images of the same device taken at different measurement and exposure times, even if imaged by different contractors. EL statistics correlating cell intensity to crack length and PV performance parameters are extracted from EL and dark I-V curves. This allows for spatially resolved performance measurement without the need for laborious flash tests to measure the light I-V- curve. This work aims to convince the EL community of certain calibration- and imaging routines, which will allow setup independent, automatable, standardised and therefore comparable results. Recognizing the benefits of EL imaging for quality control and failure detection, this work paves the way towards cheaper and more reliable PV generation. The code used in this work is made available to public as library and interactive graphical application for scientific image processing.
8
Alshawa, Amer. "AC electroluminescence in thulium-doped zinc sulfide." Ohio : Ohio University, 1988. http://www.ohiolink.edu/etd/view.cgi?ohiou1182778578.
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Dhillon, S. S. "Terahertz intersubband electroluminescence from quantum cascade heterostructures." Thesis, University of Cambridge, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.598519.
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Mid-infrared quantum cascade lasers (QCLs) have been extensively developed since their realisation in 1994, with a spectral range covered from 3.4μm (88THz) to 24μm (12.5THz). This is a direct result of advances in molecular beam epitaxy and band-structure engineering. QCLs are fabricated from multi-quantum well semiconductor heterostructures in which an appropriate engineering of the thickness and composition of the semiconductor layers adjusts the intersubband transition energies, offering considerable design flexibility of the band profile. By application of a suitable electric field and stacking together successive active regions, each injected electron cascades through the device, generating a number of photons. QCLs have shown considerable advances in performance with high powers and room temperature operation demonstrated. Extension of this quantum cascade scheme to the far-infrared, or terahertz (THz) range, is now being investigated, where the lack of sources remains acute. Specifically, operation is sought at energies smaller than the characteristic LO phonon energy of the semiconductor material, where currently no lasing has been shown (<36meV, 9 THz). The dynamics of this spectral range, however, are considerably different to those in the mid-infrared. LO phonon emission is effectively forbidden for subband spacings less than the phonon energy but increases in electron-electron scattering are expected to dominate. Although THz electroluminescence has been shown from cascade structures, systematic investigations into key parameters have not been reported. This dissertation reports a comprehensive study of THz electroluminescence from n-type A1GaAs/GaAs quantum cascade emitters as a basis for understanding the radiative and scattering mechanisms that occur in this spectral range, forming the foundations of the development of a THz semiconductor laser. The electroluminescence was correlated thoroughly with band structure calculations, along with the structural and electrical properties of the samples. The many features observed in the far-infrared were characterised, with the intersubband peaks investigated extensively to confirm their origin.
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Fuhrer, Markus Franz. "Electroluminescence Spectroscopy of Quantum Well Solar Cells." Thesis, Imperial College London, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.516978.
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Marsland, Lucy Clare. "Electroluminescence and electrochemical surface treatment of aluminium." Thesis, University of Cambridge, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620210.
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Li, Zheng Ph D. Massachusetts Institute of Technology. "Photonic crystal enhanced LED for electroluminescence cooling." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/108997.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 97-102).
An light-emitting diode (LED) consumes low-entropy electrical power and emits incoherent photons. In this process, the lattice heat also contributes to the output power if the LED operates at voltages below the photon energy (qV < h[omega]). Therefore, an LED can potentially cool itself, and the phenomenon is referred to as electroluminescence cooling (ELC). Although researchers recently reported LEDs with net cooling in various wavelength, the cooling power was not sufficient to compensate the heat flux from the ambient and thus no temperature drop is observed. In this thesis, we design and fabricate a photonic crystal (PhC) enhanced unencapsulated LED for direct observation of ELC. The PhC pattern and the structure of the device are optimized to achieve approximately 76% extraction efficiency and 300 [mu]W/cm2 net cooling power. The LED is designed to have smaller surface area and thermal mass compared to an encapsulated one to eliminate overwhelming convection heat flux. According to our thermal models, such an LED should exhibit temperature by 0.1 K and 0.5 K in air and vacuum, respectively. We also present preliminary fabrication processes and results. The critical steps include a flip-chip process with metal-metal bonding, substrate etching, and interference lithography for the PhC pattern.
by Zheng Li.
S.M.
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Malinowski, Tuhiti. "Electroluminescence à l'échelle du contact métallique ponctuel." Thesis, Aix-Marseille, 2016. http://www.theses.fr/2016AIXM4030/document.
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Cette thèse expérimentale traite de l'électroluminescence de contacts atomiques en or. Les contacts métalliques ponctuels sont formés et pilotés à l'aide d'un dispositif de jonction brisée contrôlée mécaniquement. Les contacts sont formés à partir d'un fil d'or et sont étudiés à la température ambiante.L'électroluminescence est observée dans le visible au travers d'un microscope optique. Le détecteur est une caméra sensible en silicium. Pour l'analyse du spectre émis, un dispositif dispersif en ligne a été spécifiquement développé. Pour l'infrarouge, le détecteur photovoltaïque monocanal est en InAsSb.Nos mesures électriques et optiques simultanées permettent de sonder la physique des interactions entre électrons et photons à l'échelle nanométrique. L'électroluminescence est attribuée à l'émission spontanée d'un nanogaz à haute température d'électrons chauds, conséquence des fortes densités de courant. Cette haute température électronique est fonction des conditions opératoires. Pour ces nanojonctions d'or, nos expériences nous permettent d’en proposer une expression analytique simple.Ces travaux complètent des expériences similaires menées depuis le début des années 2000. Ils sont discutés dans le cadre d'un modèle développé pour expliquer l'émission d'électrons chauds à partir de films métalliques granulaires. Nous discutons de la physique d’échauffement du gaz d’électron en rapprochant nos résultats d'expériences pompe/sonde femtoseconde interrogeant la dynamique des électrons hors équilibre dans des nanobilles d'or ainsi que d'expériences de transport en physique mésoscopique menées à très basse températureThis experimental thesis deals with electroluminescence from gold atomic point contacts. Metallic point contacts are formed and driven with a home-made mechanically controlled break junction device. The nanojunctions are made from gold wires. Experiments are performed at room temperature and in air.Electroluminescence is observed in the visible range with an infinity corrected inverted optical microscope. The detector is a high sensitivity silicon camera. To perform spectral analysis, a dispersive on-line device has been developed to be inserted directly within the microscope. A reflective objective collects infrared photons and focuses them onto an InAsSb photovoltaic cooled detector.Our simultaneous electrical and optical measurements allow us to investigate the physics of electrons and photons interactions at the nanometric scale. Electroluminescence is explained by the spontaneous emission of a hot electron nano-gas favoured by huge current densities. This high electron temperature depends on operating conditions. For gold ballistic nanojunctions, our results lead us to propose a simple expression of this temperature. This work extends similar electroluminescence studies performed since the early 2000’s. The results are discussed in this context and in the framework of a model first introduced to account for hot electron emission from thin granular metallic films. Moreover, we discuss the physics leading to the hot electron gaz with the support of pump/probe femtosecond experiments probing the nonequilibrium electron dynamics in gold nanosphere and with the support of low temperature mesoscopic transport experiments
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Ng, Po-king. "Molecular and polymeric metal complexes for electroluminescence applications." Hong Kong : University of Hong Kong, 1999. http://sunzi.lib.hku.hk/hkuto/record.jsp?B20979435.
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Barlow, Iain Alistair. "Transient electroluminescence from conjugated polymer light-emitting diodes." Thesis, University of Sheffield, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.489368.
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伍寶琼 and Po-king Ng. "Molecular and polymeric metal complexes for electroluminescence applications." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1999. http://hub.hku.hk/bib/B29866303.
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Jones, A. P. C. "Electroluminescence in epitaxial thin film ZnS and ZnSe." Thesis, Durham University, 1987. http://etheses.dur.ac.uk/6783/.
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The application of the metalorganic chemical vapour deposition technique to the production of II-VI compound semiconductor electroluminescent devices is discussed. Both low field MIS minority carrier injection devices and high field impact excitation structures are considered, and comparisons are drawn with more commiercially orientated electroluminescent displays. The epitaxial growth of ZnS and ZnSe onto (100) orientated GaAs substrates, using the reactions between dimethyl zinc and the hydrides HgS and H2Se, is described. Details are given of a novel epitaxial MISi device processing technology, in which a ZnS I-layer also acts as an etch-stop, thus enabling chemical removal of the GaAs substrate. Metal electrodes deposited directly onto the ZnS and ZnSe allow the electrical and electroluminescent characteristics of these epitaxial II-VI compound layers to be investigated in the absence of any influence from the substrate material. X-ray diffraction and reflection high energy electron dififraction confirm that the structures are epitaxial and of excellent crystallinity. It is demonstrated in an electron beam induced current study that conduction in the epitaxial MIS devices is highly uniform, and this is manifested in a uniform spatial distribution of electroluminescence. A description is given of high field impact excitation electroluminescent devices, in which the ZnS layer is doped with manganese during MOCVD growth. The spatial distribution of EL in these devices is shown to be non-uniform, and thus indicative of filamentary conduction in the ZnS:Mn, in accordance with a recently proposed dielectric breakdown model of instability. It is demonstrated that the transient characteristics of the epitaxial structures correlate with those of commercial polycrystalline devices, and are also consistent with the predictions of a dynamic model of instability. As a result of filamentary conduction, both epitaxial and polycrystalline devices are prone to degradation through localised dielectric breakdown. These breakdown events generally result in a gradual erosion of the active electrode area, although, under certain operating conditions, mobile filaments can cause rapid destruction of epitaxial structures. The columnar microstructure of sputtered devices appears to prevent such filament mobility, and it is concluded that, although filamentary conduction is a result of the carrier injection mechanism and is independent of the crystallinity, the associated damage is strongly influenced by the microstructure of the device.
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Bentley, Philip. "Synthesis and characterisation of materials for polarised electroluminescence." Thesis, University of Sheffield, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310820.
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Rennie, J. "Dosimetry and electroluminescence properties of doped calcium sulphide." Thesis, Robert Gordon University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382850.
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Wang, Yunzhang. "Ring-containing conjugated polymers : charge transport and electroluminescence /." The Ohio State University, 1996. http://rave.ohiolink.edu/etdc/view?acc_num=osu1343235117.
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Ayling, Stephen Gerard. "Cross-sections and electron distributions relating to hot electron impact excitation efficiencies." Thesis, University of St Andrews, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328092.
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Boggess-Machado, Farrah Shantell. "AC frequency dependence of electroluminescent ZnS phosphor panel color." Huntington, WV : [Marshall University Libraries], 2004. http://www.marshall.edu/etd/descript.asp?ref=440.
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Thesis (M.S.)--Marshall University, 2004.Title from document title page. Document formatted into pages; contains viii, 54 p. including illustrations. Includes bibliographical references (p. 47-49).
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Bhat, Shrivalli. "Electroluminescence in ion gel gated organic polymer semiconductor transistors." Thesis, University of Cambridge, 2011. https://www.repository.cam.ac.uk/handle/1810/239339.
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This thesis reports the light emission in ion gel gated, thin film organic semiconductor transistors and investigates the light emission mechanism behind these devices. We report that ion gel gated organic polymer semiconductor transistors emit light when the drain source voltage is swept slightly beyond the energy gap of the polymer divided by the elementary charge (Vds > Eg/e). In particular, the light emission in poly(9,9'-dioctylfluorene-co-benzothiadiazole)(F8BT) polymer semiconductor, with 1-ethyl-3-methylimidazoliumbis (trifluoromethylsulfonyl)imide/ poly(styrene-block-ethylene oxide-block-styrene) (EMIM TFSI/ SOS) ion gel as dielectric material is reported. The current-voltage characteristics corresponding to the light emission, where the systematic increase of the drain current, correlated with light emission is reported. In low voltage regime, (Vds < Eg/e), well saturated transistor characteristics are observed. By charge modulation spectroscopy (CMS) study we show that there is a prominent electrochemical doping occurring with gate voltages. Further, owing to the movement of ions with voltages,irrespective of the location of electrodes, we show that the ion gel, bilayer planar devices emit light in Vds > Eg/e regime (without any gate voltages), at room temperature. Based on thelocation of the recombination zone in the proximity of electron injecting electrode and CMS results showing prominent di ffusion of negative ions into the polymer layer, we conclude that the light emitting mechanism is akin to light emitting electrochemical cells (LECs). Even in the the transistor regime, where Vds << Eg/e, with the signatures of increasing drain current for fixed Vg and Vds values, we show that the transistor can not be of purely electrostatic operation alone. We study the fluorescence quenching of an operating bilayer device under a constant bias over a period of time and compare the results with the electroluminescence of the device and show that the formation of the p-n junction within the polymer layer due to the penetrated ions from the gel dielectric into the polymer semiconductor layer on the application of the voltage is the cause behind the light emission. We show that diffusivity of the cation (EMIM) is very low compared to the anion (TFSI). This is consistent with the fact that the recombination zone is near theelectron injecting electrode in these devices. We have developed a theoretical model for the ions movement within the semiconductor polymer matrix governed by both diffusion and drift independently, for the bilayer, polymer ion gel planar, light emitting electrochemical cells. We have further developed a 2- dimensional numerical modelbased on the theoretical model and have compared the results of the numerical model with theresults of a fluorescence probing of the bilayer device with time, at constant potential across the bilayer LEC and report that the drift coefficient of 1x10⁻¹³ cm²/V.s and a diffusion coefficient of 1 x 10⁻¹⁵cm²/V.s for TFSI ions in F8BT matrix.
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Castelino, Judith Andrea. "Estimating mobility values from electroluminescence measurements on organic polymers." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/35470.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1995.Includes bibliographical references (leaves 73-74).
by Judith Andrea Castelino.
M.Eng.
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Zhao, Junwei. "Dynamics of space charge and electroluminescence modelling in polyethylene." Thesis, University of Southampton, 2012. https://eprints.soton.ac.uk/337550/.
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Space charge has been recognized as an important factor contributing to the electrical failure of the cable insulation. Extensive efforts have been made to investigate space charge dynamics within polymeric insulations under electric stresses. Basic information about space charge has been recognized resorting to modern charge mapping techniques but the underlying mechanisms for charge transport, charge trapping characteristics are not yet well understood. Hence theoretical modelling and numerical simulation are employed to simulate the space charge and provide an insight into the charge distribution in dielectrics. This thesis comprises the quantitative analysis of space charge through numerical modelling and experimental investigations of charge trapping in polymeric insulation materials. A bipolar charge transport model which involves bipolar charge injection from the electrodes, charge transport with trapping and recombination in the bulk has been developed to simulate the dynamics of space charge in polyethylene. The build-up of space charge in polyethylene under dc electric fields has been modelled. The influence of parameters related to the properties of polyethylene on the formation of space charge has been recognized. Furthermore, this model is introduced to simulate the dynamics of corona charge decay in polyethylene. The formation of charge packets in polyethylene is also investigated using a numerical modelling approach. A fast pulsed electro-acoustic system along with a data processing program has been developed to investigate the behaviour of space charge in polyethylene under ac voltages. The understanding of space charge under ac stresses has also been simulated using the further developed bipolar charge transport model. Experiments and simulation have also been expanded into understanding electroluminescence, which is an indication of pre-aging of polymers under ac stress.
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Venter, Petrus Johannes. "Reach Through Hot Carrier Silicon Electroluminescence In Standard Cmos." Thesis, University of Pretoria, 2013. http://hdl.handle.net/2263/79204.
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Halim, Mounir. "Light-emission from conjugated dendrimers and polymers." Thesis, Durham University, 1999. http://etheses.dur.ac.uk/4297/.
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This thesis reports the photophysical and electroluminescence studies undertaken on two types of material: polymeric and dendritic. The dendritic architecture is a recent concept adopted to develop new materials for light-emitting diodes. The dendritic structure offers a combination of properties of both polymers and small organic molecules whilst having their own interesting characteristic of optimising processibility, charge transport, and optical properties independently. The dendritic structure consists of functional surface groups, conjugated dendrons and a conjugated core. Initial optical (absorption and photoluminescence) studies revealed that the dendrimer emission originates from the core and is independent of excitation wavelength. This was investigated further in distyrylbenzene based dendrimers where the effect of dendrimer generation number on photoluminescence and electroluminescence properties was studied. All dendrimers emit blue electroluminescence with, in some cases, reasonable electroluminescence quantum efficiency in the range of 0.09 % and brightness up to 150 Cd m(^-2). Having established that the furmel effect, where excitation is successfully transferred to the dendrimer core in both PL and EL, different chromophores were incorporated in the dendrimer structure. Colour control was thus demonstrated in EL devices of the different dendrimers, showing the possibility of using a large number of chromophores in a processible form for EL applications. Conjugated polymers were also studied to investigate the nature of the emitting species (poly(p-pyridine)) and the effect of side- chains (poly(p-phenylenevinylene)). In poly(p-pyridine) the emission was found to be strongly dependent on pyridyl ring rotation affecting the emission and its quantum yield while the side-chains in the poly(p-phenylenevinylene) derivatives were found to affect polymer properties such as degree of conversion of non-conjugated to conjugated polymer. The PL quantum yield system was set-up and proved useful in assessing synthesis of new materials.
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Perumal, Ajay Kumar. "Alternating current electroluminescence (AC-EL) with organic light emitting material." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-89750.
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We demonstrate a new approach for fabricating alternating current driven organic electroluminescent devices using the concept of doping in organic semiconductors. Doped charge transport layers are used for generation of charge carriers within the device, hence eliminating the need for injecting charge carriers from external electrodes.
The device is an organic-inorganic hybrid: We exploit the mechanical strength and chemical stability of inorganic semiconductors and combine it with better optical properties of organic materials whose emission color can be chemically tuned so that it covers the entire visible spectrum. The device consists of an organic electroluminescence (EL) layer composed of unipolar/ambipolar charge transport materials doped with organic dyes (10 wt% ) as well as molecularly doped charge generation layers enclosed between a pair of transparent insulating metal oxide layers. A transparent indium doped tin oxide (ITO) layer acts as bottom electrode for light outcoupling and Aluminium (Al) as top reflective electrode. The electrodes are for applying field across the device and to charge the device, instead of injection of charge carriers in case of direct current (DC) devices. Bright luminance of up to 5000 cd m-2 is observed when the device is driven with an alternating current (AC) bias. The luminance observed is attributed to charge carrier generation and recombination, leading to formation of excitons within the device, without injection of charge carriers through external electrodes.
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Swift, Michael Joseph Robert. "Aspects of single crystal and thin film high field electroluminescence." Thesis, University of Hull, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304437.
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Staple, Alan John. "Some novel aspects of DC and AC powder electroluminescence (DCEL)." Thesis, University of Greenwich, 2007. http://gala.gre.ac.uk/6308/.
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A comparison of phosphor preparation methods was carried out. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and photoluminescence measurements were used to evaluate the methods. The most suitable for DC electroluminescence (DCEL) was found to be a thioacetamide synthesis. The DCEL forming process was investigated using Laser-Raman spectroscopy. This showed no changes in copper concentration in the formed layer of a DCEL device following the forming process, suggesting that the forming process may be due to oxidation. Indium tin oxide (ITO) conductive-coated plastic was used successfully as a replacement for ITO-coated glass in DCEL devices and methods were developed for the use of cross-linked linseed oil as a binder in DCEL panels, producing a very flexible phosphor/binder layer. The feasibility of producing infra-red emitting electroluminescent devices for particular applications was investigated. ZnCdS: Cu layers were incorporated into DCEL, and ACEL devices. The DCEL devices showed a strong photoelectric effect. The ACEL devices produced infra-red emission. Further investigation of the photoelectric effect in DCEL and ACEL devices was carried out and work functions were determined for a variety of systems.
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Wong, Kiing Ing. "Study of early electrical aging of polyethylene using electroluminescence technique." Thesis, University of Southampton, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.397733.
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DeVito, David Michael. "Electroluminescence from zinc sulfide thin films doped with erbium trifluoride." [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0013835.
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Wilson, Nicholas. "Low-cost Defect Detection of Solar Cells by Electroluminescence Imaging." Thesis, Wilson, Nicholas (2017) Low-cost Defect Detection of Solar Cells by Electroluminescence Imaging. Honours thesis, Murdoch University, 2017. https://researchrepository.murdoch.edu.au/id/eprint/40010/.
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Solar panels experience a reduction in efficiency as they age due to the variable physical conditions they are exposed to throughout their lifetime, transport and installation. This exposure, due to a combination of effects such as thermal cycling and moisture, can cause a number of defects in the panels, including: cracks in, and non-uniform degradation of, the photoactive material; breakages in the current collectors; and contact finger interruptions (Mansouri 2012, Spertino, Ciocia et al. 2015).
It is therefore of great interest to detect and monitor this degradation process in order to be able to determine with greater precision, the total lifetime of the cells, as the trend of cell cost as a fraction of the module cost declines (Blakers 2015).
Several technologies exist to assess the degradation of solar panel, I-V curves, lock-in-thermography imaging and its derivatives and electroluminescence (EL) imaging. I-V curves are generated by flashing the panel with light and recording the power output that results. Lock-in-thermography looks at the heat generated by the panel and those areas that are defective, such as local short circuits, that dissipate onto the module some of the power generated (Breitenstein, Bauer et al. 2007).
EL works by reversing the role of the panel by putting power through it and making it behave as a light emitting diode instead of a photodiode (Petraglia and Nardone 2011). A typical EL setup is shown in Figure 1.1. The power is supplied by a current source(A) and Norton Resistance (B) to the solar panel (photodiode, C). The camera (D), operates on an independent circuit.
EL imaging, while an effective method of fault detection, is expensive due in part to the camera sensor technologies used, such as thermally stabilised charge coupled devices (CCD) and Indium-Gallium-Arsenide sensors (Petraglia and Nardone 2011, Parlevliet 2016).
This thesis presents a low cost apparatus for EL imaging of standard silicon solar panels and the image post processing techniques necessary to interpret the panel defects.
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Lee, Tae-Hee. "Silver nanocluster single molecule optoelectronics and its applications." Diss., Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-01302004-144007/unrestricted/lee%5Ftaehee%5F200405%5Fphd.pdf.
Full textAbstract:
Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2004.Srinivasarao, Mohan, Committee Member; Sherrill, C. David, Committee Member; Orlando, Thomas, Committee Member; EL-Sayed, Mostafa, Committee Member; Dickson, Robert, Committee Chair. Vita. Includes bibliographical references (leaves 136-159).
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Wielgosz, R. I. "Electrochemical studies of porous silicon." Thesis, University of Bath, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296302.
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Daik, Rusli. "Synthesis and characterisation of poly(arylene vinylene)s." Thesis, Durham University, 1997. http://etheses.dur.ac.uk/5037/.
Full textAbstract:
The synthesis of a series of poly(arylene vinylene)s via transition metals catalysed polycondensation with a view to producing well defined and clean samples for study , particularly for the incorporation of the material in light emitting devices has been described. Initially the McMurry reaction was applied in the synthesis of poly(4,4'-diphenylene diphenylvinylene). The reaction conditions have been optimised and relatively high molecular weight polymers with narrow molecular weight distributions were produced by fractionating the polymer. The feasibility of the McMurry reaction was established in the synthesis of related polymers; including poly(l,3-phenylene diphenylvinylene), poly(l,3-phenylene dimesitoylvinylene) and poly(4,4'-diphenylene-l,2-bis(pentafluorophenyl)vinylene). In other attempts the Yamamoto and Suzuki polycondensations were applied in the synthesis of structurally defined poly(arylene vinylene)s which could not be made via the route used earlier. Studies on UV-visible absorption, photoluminescence and electroluminescence properties of polymers produced were carried out and correlation between polymer structure and electro-optical properties of the polymer, particularly photoluminescence has been established.
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HEIKENFELD, JASON CHARLES. "RARE EARTH-DOPED GALLIUM NITRIDE FLAT PANEL DISPLAY DEVICES." University of Cincinnati / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1003428694.
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Chaichimansour, Mohammad. "Electro-optical characterization of alternating-current thin-film electroluminescence (ACTFEL) devices." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/15502.
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Edelmann, Kevin [Verfasser]. "Electroluminescence from Plasmonic Excitations in a Scanning Tunnelling Microscope / Kevin Edelmann." Karlsruhe : KIT Scientific Publishing, 2019. http://d-nb.info/1189357720/34.
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Yao, Jizhong. "Studies of recombination in organic and hybrid solar cells using electroluminescence." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/52668.
Full textAbstract:
The performance of solution processed solar cells such as organic bulk heterojunction (OPV) devices is limited by strong recombination. However, the mechanisms are still unclear. In this thesis, I develop a toolbox using steady-state spectroscopy measurements to explore the recombination mechanisms in a range of solution-processed solar cells. In the first results chapter, I use the reciprocity relation between light absorption and light emission to explore theoretical and practical performance limits for solar cells based on organic semiconductors and perovskites and compare the results with data for state-of-the-art photovoltaic cells made from GaAs, c-Si, and CIGS. In OPV systems, I show that the energetic losses due to the mismatch of the bandgap have been significantly reduced through optimisation of the donor polymer, but the non-radiative recombination losses remain the same and become the major barrier to higher performance. In the next two chapters, I use light intensity dependence of open-circuit voltage measurement (suns-VOC) and electroluminescence – injection current measurement (EL-J) to disentangle recombination mechanisms in OPV and perovskite cells, respectively. First, I identify the present of Shockley-Read-Hall recombination and surface recombination in OPV devices. I intentionally control the sample geometry to modulate the amount of surface recombination and demonstrate that surface recombination can significantly affect the device performance. In the following chapter, I analyse time dependent suns-VOC and EL-J measurements on perovskite cells with different architectures and pre-conditioning regimes used. I identify the changes in recombination mechanisms with delay time and pre-conditions. The effects of ion migration are used to interpret the results. In the final chapter, I apply luminescence spectroscopy techniques to investigate the degree of fullerene crystallinity in polymer:fullerene blends. Charge-transfer state emission is used to probe the onset of the crystallisation of fullerenes in an amorphous polymer. I relate the CT peak shift directly to the change in microstructure of a blend film.
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Tenev, Tihomir Genchev. "Modeling of electroluminescence in InSb quantum wells and inversion asymmetric effects." Thesis, Lancaster University, 2010. http://eprints.lancs.ac.uk/54013/.
Full textAbstract:
The main focus of the dissertation is description, modeling and understanding of the mechanisms underpinning electroluminescence from quantum wells. The dissertation contains original contribution of methodological and phenomenological character. We have described in detail the eight band model within the envelope function approximation(EFA) using the Löwd in perturbation method used for band structure calculations. Although not novel, a detailed derivation of this is rarely done in the literature. We have derived a theoretical expression for electroluminescence spectral emittance based entirely on quantum mechanical model, unlike the more usual semi classical models used in semiconductor physics. The final expression for the spectral emittance has a different dependence compared to the semi classical expression, namely the prefactor in the newly derived expression is proportional to 2 . We use the combination of 8 band EFA method and the newly derived expression for spectral emittance to interpret experimental measurements on unpolarized spectral emittance from several InSb/AlxIn1-xSbquantum wells. We do that using slightly novel procedure and identify several transitions unreported in InSb/AlxIn1-xSb material system up to now. In simplified models these are regarded as forbidden. We show that in 8 band EFA model there aren’t any forbidden transitions. Instead all transitions are allowed and we discuss the product of momentum matrix elements and 2D density of states, to which we refer as "generalized selection rule", as the quantity which determines the strength of the individual transitions in different energy ranges. Furthermore we discuss three groups of mechanisms which determine various properties of the electroluminescence spectrum. These groups are entirely general to electroluminescence from all sorts of quantum wells. They are: (i) band structure embodied in the "generalized selection rules" ; (2) broadening effects and (3) statistical effects. Very important are the effects of structure inversion asymmetry (SIA) on the "generalized selection rules" and the spectral emittance, which we describe and explain. Finally we discuss aspects of two other major themes related to the two characteristic properties of InSb:(i) the broken space inversion invariance and (ii) the relativistic correction of spin-orbit coupling.
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Kwong, Chin Fai. "Molecularly doped organic electroluminescent diodes." HKBU Institutional Repository, 2000. http://repository.hkbu.edu.hk/etd_ra/254.
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Cariou-Saintemarie, Nathalie. "Initiation of electrical degradation in high voltage polymeric cable insulation : electroluminescence detection." Thesis, University of Southampton, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342808.
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Keir, Paul D. "Fabrication and characterization of ACTFEL devices." Thesis, 1999. http://hdl.handle.net/1957/33252.
Full textAbstract:
The goal of this thesis is the identification and synthesis of high-luminance,
primary color alternating-current thin-film electroluminescent (ACTFEL) devices.
Special attention is paid to the synthesis of primary color green ACTFEL devices because
of the lack of an adequate primary green ACTFEL phosphor and the dominance
of green wavelengths in the response of the human eye. The sulfide materials family
is the focus of this investigation of ACTFEL phosphor hosts due to its importance in
the field of electroluminescence, although oxide and selenide phosphor hosts are also
considered. Particular attention is paid to the coactivation of the SrS:Cu ACTFEL
phosphor because of the ability to control the emission spectrum with coactivators.
Green ACTFEL devices exhibiting a high-luminance, high-efficiency, saturated green
color are demonstrated via the coactivation of SrS:Cu with alkali metals. In addition,
Zn���GeO���:Mn is demonstrated as a potentially bright and stable ACTFEL phosphor.
Finally, the "phosphor sandwich" technique of ACTFEL fabrication is presented as
a means of depositing highly-stable, high-luminance ACTFEL phosphors.
The fabrication techniques presented in this thesis are subsequently employed
to deposit custom ACTFEL devices for characterization studies aimed at determining
fundamental physical properties of ACTFEL phosphors. A method for establishing
the relative hot electron distributions inside operating ACTFEL phosphor hosts is
presented. In addition, the fabrication of SrS:Cu ACTFEL devices for characterization has allowed new insight into the density and physical basis of phosphor space charge. This insight is gained by monitoring the electrical and optical characteristics of SrS:Cu ACTFEL devices coactivated with various non-isovalent impurities to assess the influence of native defects and extrinsic impurities on space charge related behavior. It is found that native sulfur vacancies are not the physical basis for dynamic space charge in SrS:Cu ACTFEL devices.Graduation date: 2000
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Chen, Hung-Chun, and 陳虹君. "Synthesis, Energy transfer, Electroluminescence and Electroluminescence of Iridium Complexes with Polyphenyl Ligands." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/46163701798476494182.
Full textAbstract:
碩士國立臺灣大學
化學研究所
94
Phosphorescent materials of iridium complexes had been attracted much attention in recent years. The device performance of the pure organic compounds could be scarcely comparable to the inorganic complexes. The red and green materials have progressed in OLED, while the results of blue materials were unsatisfied. The research topic in this article is to tune the color of phosphorescent material of C^N2Ir(LX)b by using various C^Na ligand. Modification of the functional group, by replacing the hydrogen atom to fluoro group at the 2,4 position or CF3 at the 3,5 position on the phenyl ring, we could get emission from green to blue . We also introduce the polyphenyl group for the goal of energy transfer, and increase the steric hindrance to avoid the self quenching between iridium complexes. In the results of the physical and chemical properties of these emitting materials, we observed: (1) They have good thermal stability between 200℃-300℃ by thermogravimetry analysis. (2) They also have good reversibility by the test of cyclic-voltammetry. (3) We could clearly distinguish the 1MLCT from 3MLCT absorption by the result of Ir(III)’s strong spin-orbital coupling effect. (4) In the photoluminescence, we found the emission could be tuned from green (510 nm) to blue (485 nm) by the modification of the substituents. a：C^N = cyclometalating ligand b：LX = monoanionic and bidentate ancillary ligand
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Shih, Pei-Tzong, and 石倍宗. "Electroluminescence from nc-SiNX:H." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/65373399843976873673.
Full textAbstract:
碩士中興大學
電機工程學系所
94
Abstract In this thesis, we design three experiments. The amorphous silicon nitride (SiNX) films were deposited by plasma-enhanced chemical vapor deposition (PECVD), while the RF power, deposition conditions of pressure, substrate temperature, and diluting gas Ar/H2 flow rate for a-SiNX:H films were fixed. We control three kinds of parameters separately, different SiH4/NH3 gas ratio to modulate the nitrogen to silicon atom ratio (N/Si), different annealing time to modulate the size of nc-Si and different film thickness to observe the relation between thickness and light emitting property. After post annealing, a part of nitrogen and silicon atoms are bonded and formed Si3N4, so that the other silicon atoms are crystallized, bonded together, and separated from Si3N4. The crystal size of these silicon atoms are also confined to form a nanocrystal embedded in silicon nitride film with uniform size and great number of crystals. We measure the photoluminescence (PL) property to study the influence the N/Si ratio to PL spectrum, and then apply to make a electric device to reach the goal, electroluminescence. The deposition conditions of pressure, SiH4/Ar/H2 flow rate, RF power, substrate temperature were fixed at 1 torr、12 /160 /80 sccm、5 W及250℃, respectively. The thickness of the silicon nitride films and the annealing duration are fixed the same at 100 nm and 1.5 hours. Experiment one, The NH3 flow, which is used to control the nitrogen ratio in the amorphous silicon nitride, was changed from 12, 24, 36, to 48 sccm. Experiment two, the annealing duration was changed from 1, 1.5, to 2 hours, while fixing the NH3 flow at 60 sccm. Experiment three, the thickness of the films was changed from 5, 20, 50, to 100 nm. The structure bonding are measured by Fourier Transform Infrared spectrometer. The N/Si ratio of nc-SiNx film and crystal structure and size are measured by Auger Electron Spectroscopy and Raman spectrum. And the light emitting property was measured by PL spectrum. The result of AES spectrum indicates that N/Si atom ratio increases from 0.42 to 0.69 times. After the proportions of NH3 and SiH4 are increased to more than 5 times, N/Si atoms ratio begins to decrease to 0.65 times. The FTIR spectrum before annealing indicates that there is a larger Si-N intensity and much higher nitrogen atom ratio with increasing the NH3 flow. Due to the larger flow volume of NH3, Si-H groups becomes weaker, this is how there is little Si and more hydrogen atoms in the films. The FTIR spectrum of the films after being annealed indicated that annealing enables the film to rearrange, the disappearing of Si-H and N-H bonding indicates that annealing gets rid of hydrogen atoms, making the structure of the films to be changed. Compare the Raman spectrum before and after annealing, the samples before annealing are composed of amorphous silicon. After annealing, the Raman spectrum of all the samples got a great intensity at 520 cm-1where is the position of single crystal. That also indicates that the light emitting mechanism comes from the recombination of electron hole pairs in nc-Si. From the spectrum of photoluminescence, we know that the photoluminescence intensity can be increased with increasing the N/Si ratio in the films. Causing the main reason that luminous intensity changes mainly is because the change of the proportion of crystallization. Comparing the affect of different annealing time to the light emitting property, we presume that each sample has its best annealing duration to rearrange that cause better light emitting properties. However, as we know, the intensity of peak increases with the increasing of the film thickness. But it’s not always a direct proportion. The sample of 50 nm has higher emitting intensity than the sample of 100 nm.
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Taso, Wen-Fang, and 曹文芳. "The Characteristic of Electroluminescence." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/46483e.
Full textAbstract:
碩士國立臺北科技大學
材料及資源工程系所
93
With civil universal scientific products, phosphor applied to so much. Such as fluorescent lamps, traffic lights, Light Emitting Diode, billboard, monitor ( Cathode Ray Tube, Liquid Crystal Display, Vacuum Fluorescent Display, Electroluminescent Display ), cell phone. This paper studies discuss with the characteristic of Electroluminescence phosphor applied. It producted by scanning-printting. Insulation layer Search for Al2O3、BaCO3、BaTiO3 . Epoxy and gum is the binder. Then we discuss to driving voltage and high luminescent efficiency. Experiment result, device light higher with 10Vol% Al2O3、5Vol% BaCO3、20Vol% BaTiO3. But 20Vol% BaTiO3 luminescent device the most. The electric field intensity of insulation layer is 80KV/cm , it reaches to a threshold of phosphor emission. In the experiment, conduction layer costs too expensive and using carbon glue mix with gum in place of Ag glue. The result, 10 wt% carbon has lower resistivity. But it is relative light too lower yet. To conjecture when devise-resistivity lower、increase electric current, relative luminescence intensity with 10 wt% carbon devise is higher than with Ag glue conduction.
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Bender, Jeffrey P. "Manufacture and characterization of novel ACTFEL materials and devices." Thesis, 2003. http://hdl.handle.net/1957/30103.
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陳郁如. "Electroluminescence measurements of memory devices." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/van3ab.
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Chen, Kuan-Ting. "Electroluminescence Characteristics of Si/SiGe Superlattice." 2004. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-0807200416551900.
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