Dissertations / Theses on the topic 'Light conducting'

A system consisting of a sphere sitting on a clean mirror was modeled as a two particle system: the real sphere and its image sphere, treating the mirror as a conducting plane. When the system was irradiated with a plane-polarized collimated laser beam with varying angles of incidence, the scattering from each particle was assumed to follow Mie's solution for light scattering by a sphere. Phase difference between the scattering by the real sphere and the one by its image sphere was assessed by the geometry of the model. The far field solutions from each of the spheres were added to yield a phase dependent intensity function. Another model assumed no phase correlation between the two and the intensities from each spheres were added. Also discussed is the Double Interaction Mode, which takes the mirror-sphere separation into consideration. These theoretical results were converted to Bidirectional Reflectance Distribution Functions (BRDF). The theoretical as well as the empirical surface scattering from a good quality optical surface was introduced. The BRDF values thus calculated were added to the background scattering by the mirror since no interaction was assumed between the spheres and the rough metallic surface of the mirror. The test sample was prepared with polystyrene spheres with the nominal diameter of 0.984 μm on a high quality aluminum mirror. The BRDF data from this sample with 6328Å and 4416Å were compared with the one obtained with the model described above. The comparison strongly indicated that there existed no phase correlation between the scatterings by the two spheres. Determination of the sphere size and practical applicability for estimating the sphere number density on the surface are also discussed.

Solar cells involving two different perovskites were manufactured and analyzed. The perovskites were (CH3NH3)PbI3 and (CH3NH3)SnI3. Both perovskites have a shared methyl ammonium group (MA) and are used as both light absorbing material and hole conducting material (HTM) in this project. The preparation procedures for the complete device were according to previous attempts to make stable organic-inorganic hybrid perovskites and involved different layers and procedures. Both perovskites were manufactured by mixing methyl ammonium iodide with either lead iodide or tin iodide in different concentrations. This was then deposited on a 600nm thick mesoporous TiO2 layer. Deposition of the hole-transporting material (HTM) was done by spin-coating 2,2´,7,7´-tetrakis-(N,N-dip-methoxyphenylamine) 9,9´-spirobifluorene, also called spiro-OMeTAD. Lastly thermal evaporation was used to deposit a silver electrode. Different measurements were done on the light absorbing materials. The lead perovskite solar cell device was subjected to illumination with Air Mass 1.5 sunlight (100mW/cm2) which produced an open circuit voltage Voc of 0.645 V, a short circuit photocurrent Jsc of about 7 mA/cm2, and a fill factor FF of 0.445. This resulted in a power conversion efficiency (PCE) of about 2% and an incident photon to current efficiency (IPCE) of up to 60%. The tin perovskite has not been used in solar cells before and the initial results presented here shows low performance using the same device construction as for the lead perovskite. However, the incident photon to electron conversion affirms that there is a current in the visible region, and IPCE of 12.5 % was observed at 375nm. UV-visible NIR measurement was used to analyze the light absorption of the perovskite structures and a broader light absorption was observed for the lead perovskite compared to the tin perovskite. X-ray diffraction (XRD) analyzing was done on both perovskite materials using different concentrations and both with and without nanoporous TiO2 film. Both perovskites demonstrate very similar peaks with some exceptions. Photo-induced absorption (PIA) measurement was used for the purpose of showing the magnitude of charge separation or hole transfer in the light absorbing material, both when using the perovskites as a light absorber and a hole conductor. This is measured by analyzing the hole injection from the excited light absorber into the HTM. Hole transfer was observed for the lead perovskite (when used as light absorber) and tin perovskite (when used as hole conductor).

Det här projektet handlar om att utveckla en metod för real driving emission (RDE). RDE är ett komplement till Worldwide Light Duty Test Procedure (WLTP) som kommer att ersätta New European Driving Cycle (NEDC). Dessa cykler och metoder används för att mäta personbilars avgaser. Huvudanledningen till varför NEDC ska bytas ut är för att körcyklerna inte längre är realistiska och reflekterar inte hur en bil presterar egentligen. Detta har lett till att bilar har högre bränsleförbrukning och högre avgasutsläpp när dom körs i trafiken jämfört med resultaten från NEDC.Metoden utvecklades genom hänvisningar till den officiella WLTP rapporten. Tillsammans med Vehicle Emission gruppen från AVL fastställdes en komplett steg för steg metod.Utrustningen som användes förseddes av AVL och flera tester av varje steg av metoden genomfördes för att förfina metoden så mycket som möjligt. Bilen som användes var en SAAB 9-5 2.0l bensin.Resultaten visade att både bilen och testet inte mötte kriterierna för RDE och godkändes inte av programmet som användes för att utvärdera testet. Detta var delvis för att kriterierna för RDE är strikta och delvis för att ingen pre och post test genomfördes eftersom det tar mycket tid för att dom testerna ska bli godkända.I överlag ger WLTP och RDE potentiella bilköpare en bättre detaljerad sammanfattning av hur bra bilen presterar i trafiken jämfört med NEDC.
This project is about developing a method for real driving emission (RDE). RDE is a complement to Worldwide Light Duty Test Procedure (WLTP) which will replace the New European Driving Cycle (NEDC). These cycles and procedures are used for measuring emissions for light duty vehicles. The main reason why NEDC is being replaced is because the driving cycles does not reflect how vehicles are normally driven. This has resulted in vehicles having higher fuel consumption and emitting more poisonous gases when driven on actual roads compared to the results from the NEDC.The method was developed by referring to the laws of the official WLTP report written by EU. Together with the Vehicle Emissions team at AVL a complete step by step method was established.All the equipment and instruments were provided by AVL and several tests of each step of the method was made to perfect the method as much as possible. The vehicle that was used was a 2005 SAAB 9-5 2.0l petrol.The results displayed that the car and the test did not meet the criteria for RDE and was not passed by the evaluating software. This was partly because the driving criteria for RDE are strict and can be difficult to achieve and partly because no pre and post test was made since it can take several tries before those tests are passed.Overall, WLTP and RDE give buyers a more detailed and better conclusion of how a car performs on the road compared to NEDC.

The objective of this work was to study two different light management approaches to enhance the efficiency of thin film Si solar cells and these were the manipulation of the light path (light trapping) and changing the incoming photon energy (upconversion). In the first approach the light path was manipulated by creating either periodic or random textured interfaces. Periodic patterns were created at the front AZO by means of direct laser ablation. Amongst all the patterns assessed, the best result was achieved with a linear pattern of 10 lam of pitch and 360 nm of groove depth, that yielded to an Rs of 11 SI/sq and a haze of 12.7% at 600 nm. However structures in the sub-micrometer range cannot be created because the minimum period is limited by the laser spot. By means of the Aluminum Induced Texturing method (AIT) random textures were performed on glass substrates. In this method, a thin Al film is deposited onto a glass substrate and a redox reaction between the Al and the SiO2 of the glass is induced by high temperature annealing. The reaction products are wet-etched and the result is a uniform and rough glass surface. The process parameters were varied in order to control the resultant glass roughness and it was found that the most critical was the Al deposition method. By using evaporation smooth U-shaped craters morphology and roughness up to 90 nm were created, whereas the sputtered films resulted in rough and porous textures with roughness until 145 nm. AZO grown over the U-shape crater morphology led to a double texture with haze values above 10% at 600 nm, transparency above 84%, and Rs-7 SI/sq whereas AZO over very rough glass resulted in a cauliflower-like surface with haze values >32% at 600 nm, Rs around 9.5 SI/sq and transmittance of 74%. A-Si:H solar cells were deposited on different AIT textures and an improvement of the short circuit current, as well as a reduction of the device reflectivity was achieved in all cases in comparison to the cells deposited on smooth glass textures. The second approach was to create a transparent and conducting upconverter to be used on top of the rear reflector of a thin film Si solar cell. For that purpose, ZnO was doped with Er and Yb ions and was post-annealed under different treatments. The unique spectral properties of rare earth (RE) elements due to their electronic configuration occur as a result of their intra 4f-4f shell transitions. In the case of Er, its excitation takes places at 1500 nm and 980 nm and the upconverted photons are emitted within the Si absorption range. Moreover, codoping with Yb can enhance the Er visible emission because they cooperate together due to the matching of their energy levels for k=980 nm. As deposited ZnO doped with rare earths (RE) was found to be transparent and conducting but not luminescent. RE ions need to be surrounded by 6 oxygen in a distorted octahedron to be optically active and REs replacing zinc in the ZnO lattice do not present this symmetry; hence, a post deposition treatment is needed. When the films were post-annealed in air, visible upconversion (UC) was seen at 660 nm under 980 nm laser excitation, however, the films become almost insulating. When the films were annealed in vacuum, lower UC luminescence was achieved, and the resistivity increased 1 order of magnitude. By using CW laser radiation, the electrical properties were maintained and high UC was observed. UC came from clusters of RE06 as well as from RE203 inside or outside the matrix. When annealing in air, in vacuum or by laser radiation, oxygen from the atmosphere bound to the RE to form RE oxides and/or RE06 complexes but just laser annealing was able to preserve the conductivity while producing optically active centers.
L'objectiu d'aquesta tesi és la millora de l'eficiència de les cèl•lules solars de silici en capa prima mitjançant l'estudi de nous mètodes per a l'aprofitament de la llum solar al dispositiu. El primer mètode consisteix en texturar el substrat de vidre per dispersar la llum incident i així incrementar l'absorció en la capa activa. El mètode emprat es la texturització induïda per alumini (AIT); que es basa en una reacció de reducció no uniforme entre el vidre i una capa prima d'alumini gràcies a un tractament tèrmic. Posteriorment els productes de la reacció s'eliminen mitjançant una solució basada en àcid i el resultat és un vidre transparent i texturat. S'ha fet un estudi de la rugositat en funció dels paràmetres del procés i s'ha aconseguit obtenir rugositats controlades i uniformes en superfícies de fins a 10x 10 cm2. Diferents textures s'han provat en cèl.lules solars de silici amorf i s'ha demostrat l'eficàcia d'aquestes en la millora del corrent respecte a les mateixes cèl•lules dipositades sobre vidre pla. El segon mètode estudiat és el fenomen de l'up-conversion que consisteix en la conversió de fotons de baixa energia (EEg) que podran ser absorbits en la zona activa; així doncs s'ha intentat fer una capa conductora, transparent i amb propietats d'up-conversion per utilitzar com a contacte per a cèl• lules solars. Per aquest propòsit s'han estudiat capes conductores i transparents d'òxid de zinc dopat amb erbi i iterbi dipositades per polvorització catòdica sobre vidre. Com que les terres rares han d'estar envoltades d'oxigen per actuar com a centres òptics actius, i en les capes de ZnO:Er:Yb no es dóna aquesta configuració, les capes s'han hagut de sotmetre a diferents tractaments tèrmics, com escalfament en aire, en buit o escalfament amb làser. Escalfant en aire o en buit s'aconsegueix obtenir up-conversion però la conductivitat disminueix notablement, en canvi, escalfant amb radiació làser es possible de mantenir les propietats elèctriques i a més, activar òpticament les terres rares.

>Magister Scientiae - MSc
Applications of electrochemiluminescent conjugated polymers offer promising solutions in addressing the problem of light emitting devices. However, the challenging problems that hamper their application in light emitting devices are loss of signal due to diffusion of the electrochemiluminescence (ECL) reagent out of the detection zone, limited ability to repeatedly cycle an individual luminophore and high reagent consumption. In this work, the main objective was to produce conducting polymers with enhanced electrochemiluminescence by tuning the properties of the polymer itself. The electrochemical and photophysical properties of films of polyaniline (PANI) and poly(8-anilino-1- naphthalene sulfonic acids) (PANSA) synthesized through electro- and chemical polymerization methods were also investigated. The electrosynthesis of PANSA undoped and doped with anthracene sulfonic acid (ASA), 1,2-naphthaquinone-4-sulfonic acid (NSA) and carbon nanotubes (CNT) in acid medium was investigated and the cyclic voltammograms (CV) showed the growth of the polymer during polymerization. The CV multiscan characterization displayed that the growth of the polymer was dependent of the scan rate and the three redox couples were observed as indicative of the three redox states of typical polyaniline and its derivatives. The results also showed that the peak currents were diffusion controlled and the electron charge transport coefficient (De) of the electrosynthesized polymers was found to range between 10⁻⁸ and 10⁻⁹ cm² s⁻¹ for PANSA, PANSA-ASA, PANSA-NSA and PANSA-CNT. The De value indicates that the movement of electrons along the polymer chain was averagely fast. The transmission electron microscopy (TEM) was used to investigate the electronic morphology of the polymers and the TEM images showed an intertwinement of tubings which aggregate into a ring with a mixture of tubings and plastic sheets. The chemical synthesis of PANI, PANSA and PANI-NSA was carried out by using monomers analine, 8-anilino-1-naphthalene sulfonic acid, and aniline with 1,2- naphthaquinone-4-sulfonic acid, respectively, using oxidants. All chemically synthesized polymers exhibited quinoid and benzoid bands typically see in polyaniline FTIR and Raman spectra confirmed the successfully formation of polymers. The CV characterization of these polymers showed distinctive redox peaks. This proved that the polymers were electroactive, conductive and exhibited reversible electrochemistry. The De of the electrosynthesized polymers was found to be ~10⁻⁵ cm² s⁻¹ for chemically synthesized polymers. The electric conductivity measurement showed to increase from 10⁻⁴ to 10⁻² when aniline was polymerized with NSA dopant, this might be related to the process of electron transfer from dopant to polymer. Scanning electron microscopy for external morphology showed that the polymers were made of different nano- rods polymeric structures. Photophysical properties of electro- and chemically synthesized PANSA and PANI were investigated through UV-vis absorption, fluorescence behaviour, and lifetime. The UV-vis absorption spectra of these polymers showed that they exhibited absorption bands corresponding to the polyemeraldine redox state of typical polyaniline. The effect of dopants resulted in the increase in solubility of the polymers with a small shift of absorption bands due to incorporation of dopants in to the backbone of the polymer. The fluorescence emission spectra of the electrochemically synthesized PANSA with and without dopants were observed to be similar and mirror image of the excitation spectra and corresponding to the electronic band of the benzoid ring in the polyemeraldine form confirming that the fluorescing molecule in these polymers were the benzoid rings. However, the emission spectra of the chemically synthesized PANSA and PANI were different to excitation spectra due to loss of symmetry upon excitation. The effects of chemically synthesized PANI, PANSA and PANI-NSA addition on the photophysical properties of [Ru(bpy)₂(picCOOH)]²⁺.(ClO₄⁻)₂) were investigated in order to understand the interaction of polymer and [Ru(bpy)₂(picCOOH)]²⁺.(ClO₄⁻)₂. The analysis revealed that the presence of polyaniline and its derivatives enhanced the [Ru(bpy)₂(picCOOH)]²⁺.(ClO₄⁻)2 absorption band, photoluminescence and fluorescence lifetime. The enhancement observed from interaction of [Ru(bpy)₂(picCOOH)]²⁺.(ClO₄⁻)₂ with polyaniline and its derivatives might be due to the excited state electron transfer from the PANI and PANSA excited state to the [Ru(bpy)₂(picCOOH)]²⁺.(ClO₄⁻)₂. It was further demonstrated in this work that it is possible to form polyaniline and PANSA doped with [Ru(bpy)₂(picCOOH)]²⁺.(ClO₄⁻)₂ films on ITO electrode using potentiostatic growth method to favour ECL production. The results showed that all films generated ECL in the presence of Tripropylamine (TPA) as a co-reactant and their emission properties depend on time used to prepare the film. The enhancement of ECL signal was due to a positive electron transfer from the conducting polymer (PANI and PANSA) to [Ru(bpy)₂(picCOOH)]²⁺.(ClO₄⁻)₂ complex. The results highlighted the potential of these polymeric luminophores usage in the manufacturing of the ECL devices.

The Joint Light Tactical Vehicle (JLTV) was among the first defense programs to require a competitive prototyping acquisition strategy under the 19 Sep 07 USD (AT&L) policy Memorandum, Prototyping and Competition. At Milestone A, the program was directed to inform the requirements process, validate technology maturity, assess commonality of components across a family of vehicles, and assess manufacturing risks. As a result, the joint program office simultaneously executed three weapon system prototyping contracts in a continuously competitive environment while meeting cost, schedule, and performance objectives. The goal of the JAP was to describe the program management strategy used in the JLTV Technology Development (TD) phase. The resulting document is a firsthand perspective from working within the Product Manager (PM). It discusses how TD acquisition phase program objectives were addressed and several unique management solutions. The focus is an account of planning and managing three contracts from Sep 2008 until May 2010. Information from the JLTV TD phase has significantly changed the requirements for the EMD phase. In addition to informing requirements, the program leveraged the competitive environment by maintaining constant emphasis on the contractors to meet cost and schedule. The results demonstrated that competitive prototyping can work.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2010.
Includes bibliographical references.
Difficulties with traditional methods of synthesis and film formation for conducting polymers, many of which are insoluble, motivate the development of CVD methods. Indeed, conjugated polymers with rigid linear backbones typically crystallize readily and overcoming the resultant heat of crystallization makes them difficult to dissolve. Poly(3,4-ethylenedioxythiophene) (PEDOT) thin films were obtained through oxidative chemical vapor deposition (oCVD) by using a new oxidant- bromine. The use of bromine eliminates any post processing rinsing step required with other oxidants like iron chloride and hence makes the process completely dry. Accelerated aging experiments show longer retention of electrical conductivity for the PEDOT films obtained using bromine as the oxidant. Conductivities as high as 380 S/cm were obtained for PEDOT films deposited using bromine as the oxidant at 80 'C, which is significantly higher than that for PEDOT films deposited using iron chloride as the oxidant at the same temperature. Cross-sectional SEM of the PEDOT films deposited using bromine on silicon trench wafers demonstrates high conformal deposition of the films. All the results show the possibility of depositing highly conducting, conformal PEDOT films on any substrate including silicon, glass, paper, plastic. One of the many applications of conducting polymer is as hole-transport layer in light emitting diode. To be competitive in the LED market, improvements in hybrid-LED quantum efficiencies as well as demonstrations of long-lived HLED structures are necessary. In this work, we consider improvement in the stability of the HLED. The device fabricated can be configured as ITO/ Poly (EDOT-co-TAA)/CdSe (ZnS)/ Au. All the materials used in the device synthesis are stable in ambient conditions and all the synthesis steps on ITO substrate are done either in air or in very moderate pressure conditions. This significantly reduces the cost of the device fabrication by obviating the need of packaging layers and ultrahigh vacuum tools. The operating voltage as low as 4.3 V have been obtained for red-LEDs. We believe that with optimization of various layers in the device, further improvements can be made. For green LEDs we obtained the characteristic IV curve of a diode, but we still need to work on getting a functioning green LED.
by Hitesh Chelawat.
S.M.

This work demonstrates an approach to develop low-cost, semi-transparent, long-term stable, and efficient organic photovoltaic (OPV) cells and organic light-emitting diodes (OLEDs) using various alternative electrodes such as conductive polymers, doped ZnO, and carbon nanotubes. Such electrodes are regarded as good candidates to replace the conventional indium tin oxide (ITO) electrode, which is expensive, brittle, and limiting the manufacturing of low-cost, flexible organic devices. First, we report long-term stable, efficient ITO-free OPV cells and transparent OLEDs based on poly(3,4-ethylene-dioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) electrodes by using a solvent post-treatment or a structure optimization. In addition, a high performance internal light out-coupling system for white OLEDs based on PEDOT:PSS-coated metal oxide nanostructures is developed. Next, we demonstrate highly efficient ITO-free OPV cells and OLEDs with optimized ZnO electrodes doped with alternative non-metallic elements. The organic devices based on the optimized ZnO electrodes show significantly improved efficiencies compared to devices with standard ITO. Finally, we report semi-transparent OPV cells with free-standing carbon nanotube sheets as transparent top electrodes. The resulting OPV cells exhibit very low leakage currents with good long-term stability. In addition, the combination of various kinds of bottom and top electrodes for semi-transparent and ITO-free OPV cells is investigated. These results demonstrate that alternative electrodes-based OPV cells and OLEDs have a promising future for practical applications in efficient, low-cost, flexible and semi-transparent device manufacturing
Die vorliegende Arbeit demonstriert einen Ansatz zur Verwirklichung von kostengünstigen, semi-transparenten, langzeitstabilen und effizienten Organischen Photovoltaik Zellen (OPV) und Organischen Leuchtdioden (OLEDs) durch die Nutzung innovativer Elektrodensysteme. Dazu werden leitfähige Polymere, dotiertes ZnO und Kohlenstoff-Nanoröhrchen eingesetzt. Diese alternativen Elektrodensysteme sind vielversprechende Kandidaten, um das konventionell genutzte Indium-Zinn-Oxid (ITO), welches aufgrund seines hohen Preises und spröden Materialverhaltens einen stark begrenz Faktor bei der Herstellung von kostengünstigen, flexiblen, organischen Bauelementen darstellt, zu ersetzten. Zunächst werden langzeitstabile, effiziente, ITO-freie Solarzellen und transparente OLEDs auf der Basis von Poly(3,4-ethylene-dioxythiophene):Poly(styrenesulfonate) (PEDOT:PSS) Elektroden beschrieben, welche mit Hilfe einer Lösungsmittel-Nachprozessierung und einer Optimierung der Bauelementstruktur hergestellt wurden. Zusätzlich wurde ein leistungsfähiges, internes Lichtauskopplungs-System für weiße OLEDs, basierend auf PEDOT:PSS-beschichteten Metalloxid-Nanostrukturen, entwickelt. Weiterhin werden hoch effiziente, ITO-freie OPV Zellen und OLEDs vorgestellt, bei denen mit verschiedenen nicht-metallischen Elementen dotierte ZnO Elektroden zur Anwendung kamen. Die optimierten ZnO Elektroden bieten im Vergleich zu unserem Laborstandard ITO eine signifikant verbesserte Effizienz. Abschließend werden semi-transparente OPV Zellen mit freistehenden Kohlenstoff-Nanoröhrchen als transparente Top-Elektrode vorgestellt. Die daraus resultierenden Zellen zeigen sehr niedrige Leckströme und eine zufriedenstellende Stabilität. In diesem Zusammenhang wurde auch verschiedene Kombinationen von Elektrodenmaterialen als Top- und Bottom-Elektrode für semi-transparente, ITO-freie OPV Zellen untersucht. Zusammengefasst bestätigen die Resultate, dass OPV und OLEDs basierend auf alternativen Elektroden vielversprechende Eigenschaften für die praktische Anwendung in der Herstellung von effizienten, kostengünstigen, flexiblen und semi-transparenten Bauelement besitzen

Observando o atual interesse em polímeros organometálicos para diversas aplicações, foi feita a síntese de uma série de polímeros conjugados contendo ferroceno na cadeia principal visando à investigação de suas propriedades, em especial fenômenos magnetorresistivos, magneto-ópticos e de óxido-redução. Os polímeros preparados pelo método de McMurry foram os seguintes: PFV: poli(1,1\'-ferrocenilenovinileno) e PFV-DOPPV-M: poli[1,1\'-ferrocenilenovinileno-alt-(2,5-di-n-octilóxi)-1,4-fenilenovinileno]. Outros dois polímeros foram preparados utilizando o método de polimerização de Wittig, o PFV-DOPPV-W: poli[1,1\'-ferrocenilenovinileno-alt-(2,5-di-n-octilóxi)-1,4-fenilenovinileno] e o PFV-DMPPV: poli[1,1\'-ferrocenileno-vinileno-alt-(2,5-dimetóxi)-1,4-fenilenovinileno]. A síntese de polímeros contendo segmentos π-conjugados equenos e bem definidos separados por segmentos não-conjugados é uma das melhores stratégias para a obtenção de polímeros emissores de luz azul. Com base nesse argumento foi feita a síntese de uma série de polímeros contendo um derivado metoxilado de bisfenol-A (BPA) na cadeia principal, alternando-se com unidades de PPV ou PFV que apresentam segmentos conjugados bem definidos. Os polímeros preparados foram os seguintes: BPA-DOPPV:poli[2,2-bis(4-metoxifenil)-propano-alt-2,5-(di-n-octilóxi)-1,4-divinilbenzeno]; BPA-PPV: poli[2,2-bis(4-metoxifenil)-propano-alt-1,4-ivinilbenzeno]; BPA-DMPPV: poli[2,2-bis(4-metoxifenil)-propano-alt-2,5-dimetóxi-1,4-ivinilbenzeno]; BPA-DBPPV: poli[2,2-bis(4-metoxifenil)-propano-alt-2,5-dibromo-1,4-divinilbenzeno] e BPA-PFV: poli[2,2-bis(4-metoxifenil)-propano-alt-1,1\'-divinil-ferroceno]. Todos os polímeros obtidos foram caracterizados por métodos espectroscópicos (UV-VIS, IR, RMN), análises térmicas, SEC, entre outras. Algumas aplicações foram estudadas para esses polímeros, tais como a construção de um eletrodo de ORP modificado, a produção de diodos orgânicos emissores de luz (OLEDs) e a determinação da resposta \"olfativa\" de sensores de gases.
Owing to the current interest in organometallic polymers and their applications, a group of conducting polymers containing ferrocene in the main chain was synthesized aiming the study of their magnetoresistive, magneto-optic and redox properties. The following polymers were prepared via McMurry method: poly(1,1\'-ferrocenylenevinylene) (PFV) and poly[1,1\'-ferrocenylenevinylene-alt-(2,5-di-n-octiloxy)-1,4-phenylenevinylene] (PFV-DOPPV-M). Two other polymers were synthesized via Wittig method: poly[1,1\'-ferrocenylenevinylene-alt-(2,5-di-n-octiloxy)-1,4-phenylenevinylene] (PFV-DOPPV-W) and poly[1,1\'-ferrocenylene-vinylene-alt-(2,5-dimethoxy)-1,4-phenylenevinylene] (PFV-DMPPV). The synthesis of polymers with well-defined small π-conjugated segments separated by non-conjugated segments is one of the best strategies to obtain blue light emitting polymers. Based on this statement the synthesis of several polymers formed by methoxylated bisphenol-A (BPA) alternated with PPV or PFV units was performed. The prepared polymers were the following: poly[2,2-bis(4-methoxyphenyl)-propane-alt-2,5-(di-n-octiloxy)-1,4-divinylbenzene] (BPA-DOPPV), poly [2,2-bis(4-methoxyphenyl)-propane-alt-1,4-divinylbenzene] (BPA-PPV), poly[2,2-bis(4-methoxyphenyl)-propane-alt-2,5-dimethoxy-1,4-divinylbenzene] (BPA-DMPPV), poly[2,2-bis(4-methoxyphenyl)-propane-alt-2,5-dibromo-1,4-divinylbenzene] (BPA-DBPPV) and poly[2,2-bis(4-methoxyphenyl)-propane-alt-1,1\'-divinylferrocene] (BPA-PFV). All the synthesized polymers were characterized by spectroscopic methods (UV/VIS, IR, NMR), thermal analysis, SEC, among others. Some applications to these polymers were studied: a modified ORP electrode, organic light emitting devices (OLEDs) and gas sensors.

As interessantes propriedades eletrônicas, mecânicas e óticas dos materiais orgânicos conjugados fizeram emergir diversas aplicações tecnológicas e comerciais em dispositivos baseados nesses materiais, tais como sensores, memórias, células solares e diodos emissores de luz poliméricos (LEDs). Neste sentido, o tema central desta tese é o estudo das propriedades elétricas e morfológicas e os mecanismos de transporte eletrônico de cargas no PEDOT:PSS, uma blenda polimérica que consiste de um policátion condutivo, o poli(3,4- etilenodioxitiofeno) (PEDOT) e do poliânion poli(estirenosulfonado) (PSS). PEDOT:PSS é amplamente usado como material de eletrodo em aplicações na área de eletrônica plástica, como mencionado anteriormente. Apesar da condutividade elétrica dos filmes finos de PEDOT:PSS possa variar várias ordens de grandeza, dependendo do método pela qual é processado e transformado em filme fino, as razões para este comportamento é essencialmente desconhecido. Esta tese descreve um estudo detalhado do transporte eletrônico de cargas anisotrópico e sua correlação com a morfologia, as condições e as dimensões da separação de fase entre os dois materiais, PEDOT e PSS. Antes de abordar as propriedades do PEDOT:PSS, uma camada de filme fino inorgânica usada para aumentar o tempo de vida de dispositivos orgânicos é descrita no Capítulo 2. Um importante mecanismo de degradação em LEDs poliméricos é a fotooxidação da camada ativa. Assim, isolar a camada ativa da água, oxigênio e luz, torna-se crucial para o aumento do tempo de vida. Um sistema de deposição química a partir da fase de vapor estimulada por plasma (PECVD) é usado para depositar filmes finos de nitreto de carbono em baixas temperaturas, menores que 100 °C, sobre PLEDs com a intenção de aumentar o tempo de vida destes dipositivos e diminuir a fotodegradação do poli[2-metoxi-5- (2-etil-hexiloxi)-p-fenileno vinileno] (MEH-PPV) em ambiente atmosférico. O filme fino de nitreto de carbono possui as características de um material que pode bloquear a umidade e que tem espessura e flexibilidade adequados para a nova geração de PLEDs flexíveis. As características dos filmes finos de nitreto de carbono e MEH-PPV foram investigadas usando-se técnicas de espectroscopia ótica, com particular ênfase no processo de degradação do MEHPPV sob iluminação. Os resultados mostraram que o filme fino de nitreto de carbono protege o filme polimérico e diminui consideravelmente a fotooxidação. Para avaliar o efeito do encapsulamento em dispositivos reais, LEDs poliméricos foram fabricados e pelas curvas de corrente-tensão um aumento no tempo de vida é confirmado quando a camada de nitreto de carbono é presente. O tempo de vida desejado, maior que 10.000 horas, para aplicações comerciais não foi atingido, entretanto, o encapsulamento pode ser melhorado otimizando as propriedades da camada de nitreto de carbono e combinando-as com camadas de outros materiais orgânicos e inorgânicos. Os capítulos seguintes deste trabalho aborda os estudos realizados com o PEDOT:PSS, uma vez que é amplamente usado em eletrônica orgânica, mas relativamente tem recebido pouca atenção com respeito ao transporte eletrônico de cargas, bem como sua correlação com a morfologia. No Capítulo 3, experimentos com microscopia de varredura por sonda (SPM, Scanning Probe Microscopy) e medidas de condutividade macroscópica são utilizados para estudar e obter um modelo 3D morfológico completo que explica, qualitativamente, a condutividade anisotrópica observada nos filmes finos de PEDOT:PSS depositados pela técnica de spin coating. Imagens topográficas de microscopia de varredura por tunelamento (STM) e imagens da seção transversal observadas com o microscópio de forca atômica (X-AFM) revelaram que o filme fino polimérico é organizado em camadas horizontais de partículas planas ricas em PEDOT, separadas por lamelas quasi-contínuas de PSS. Na direção vertical, lamelas horizontais do isolante PSS reduzem a condutividade e impõe o transporte eletrônico a ser realizado por saltos em sítios vizinhos próximos (nn-H, nearest-neighbor hopping) nas lamellas de PSS. Na direção lateral, o transporte eletrônico via saltos 3D em sítios a longas distâncias (3D-VRH, variable range hopping) ocorre entre as ilhas ricas em PEDOT que são separadas por barreiras muito mais finas de PSS, causando um aumento da condutividade nesta direção. Esta discussão é estendida ao Capítulo 4 com uma descrição quantitativa do transporte eletrônico de cargas predominantes. Particularmente, é demonstrado que o transporte de cargas via saltos 3D em sítios a longas distâncias ocorre entre ilhas ricas em PEDOT e não entre segmentos isolados de PEDOT ou dopantes na direção lateral, enquanto que na direção vertical o transporte de cargas via saltos em sítios vizinhos próximos ocorre dentro das lamelas do quasi-isolante PSS. Em algumas aplicações, faz-se necessário usar PEDOT:PSS com alta condutividade elétrica. Isso pode ser feito adicionando-se sorbitol à solução aquosa de PEDOT:PSS. Após um tratamento térmico, e dependendo da quantidade de sorbitol adicionado, a condutividade aumenta várias ordens de grandeza e as causas e consequências de tal comportamento foram investigadas neste trabalho. O Capítulo 5 investiga as várias propriedades tecnológicas do PEDOT:PSS altamente condutivo tratado com sorbitol, tais como a própria condutividade, os efeitos dos tratamentos térmicos e exposição à umidade. É observado que o aumento da condutividade elétrica, devido à adição de sorbitol na solução aquosa, é acompanhado por uma melhoria na estabilidade da condutividade elétrica em condições atmosféricas. Surpreendentemente, a condutividade elétrica do PEDOT:PSS, sem tratamento com sorbitol (~ 10-3 S/cm), aumenta mais de uma ordem de grandeza sob ambiente úmido de 30-35 % umidade relativa. Este efeito é atribuido a uma contribuição iônica à condutividade total. Análise Temogravimetrica (TGA), espectrometria de massa com sonda de inserção direta (DIP-MS) e análise calorimétrica diferencialmodulada (MDSC) foram usadas como técnicas adicionais para o entendimento dos estudos deste Capítulo. No Capítulo 6, microscopia de varredura por sonda-Kelvin (SKPM) foi empregada para medir o potencial de superfície dos filmes finos de PEDOT:PSS tratados com diferentes concentrações de sorbitol. Mostra-se que a mudança no potencial de superfície é consistente com uma redução de PSS na superfície do filme fino. Para estudar o transporte eletrônico nos filmes finos de PEDOT:PSS altamente condutivos tratados com sorbitol, o Capítulo 7 usa medidas de temperatura e campo elétrico em função da conduvitidade correlacionados com analises morfológicas realizadas por STM. É observado que o transporte eletrônico por saltos, na direção lateral, muda de 3D-VRH para 1D-VRH quando o PEDOT:PSS é tratado com sorbitol. Esta transição é explicada por uma auto-organização das ilhas ricas em PEDOT em agregados 1D, devido ao tratamento com sorbitol, tornando-se alinhadas em domínios micrométricos, como observado pelas imagens de STM.
Employing the unique mechanical, electronic, and optical properties of the conjugated organic and polymer materials several technological and commercial applications have been developed, such as sensors, memories, solar cells and light-emitting diodes (LEDs). In this respect, the central theme of this thesis is the electrical conductivity and mechanisms of charge transport in PEDOT:PSS, a polymer blend that consists of a conducting poly(3,4-ethylenedioxythiophene) polycation (PEDOT) and a poly(styrenesulfonate) polyanion (PSS). PEDOT:PSS is omnipresent as electrode material in plastic electronics applications mentioned above. Although the conductivity of PEDOT:PSS can vary by several orders of magnitude, depending on the method by which it is processed into a thin film, the reason for this behavior is essentially unknown. This thesis describes a detailed study of the anisotropic charge transport of PEDOT:PSS and its correlation with the morphology, the shape, and the dimension of the phase separation between the two components, PEDOT and PSS. Before addressing the properties of PEDOT:PSS, a new barrier layer is described in Chapter 2 that enhances the lifetime of organic devices. An important degradation mechanism in polymer LEDs is photo-oxidation of the active layer. Hence, isolating the active layer from water and oxygen is crucial to the lifetime. Plasma-enhanced chemical vapor deposition (PECVD) is used to deposit a thin layer of carbon nitride at low deposition temperatures, below 100 °C, on a polymer LED that uses poly[2-methoxy-5-(2´-ethylhexyloxy)-1,4- phenylene vinylene] (MEH-PPV) as active layer. A thin layer of carbon nitride acts as barrier for humidity, but is still sufficiently bendable to be used in flexible polymer LEDs. The characteristics of carbon nitride and MEH-PPV films have been investigated using optical spectroscopy, with particular emphasis on the degradation process of MEH-PPV under illumination. The measurements show that the carbon nitride coating indeed protects the polymer film and diminishes the photo-oxidation considerably. To study the effect of the encapsulation in real devices, polymer LEDs were made and their current-voltage characteristics confirm the enhanced lifetime in the presence of a carbon nitride barrier layer. However, the target, a lifetime of more than 10,000 hours for commercial applications, was not achieved. The remaining chapters of this thesis describe the investigations of PEDOT:PSS. PEDOT:PSS is widely used in organic electronics. So far, relatively little attention has, been paid to the mechanisms of charge transport in this material and the correlation of those properties to the morphology. In Chapter 3, scanning probe microscopy (SPM) and macroscopic conductivity measurements are used to obtain a full 3D morphological model that explains, qualitatively, the observed anisotropic conductivity of spin coated PEDOT:PSS thin films. Topographic scanning probe microscopy (STM) and cross-sectional atomic force microscopy images (X-AFM) reveal that the thin film is organized in horizontal layers of flattened PEDOT-rich particles that are separated by quasi-continuous PSS lamella. In the vertical direction, the horizontal PSS insulator lamellas lead to a reduced conductivity and impose nearest-neighbor hopping (nn-H) transport. In the lateral direction, 3D variable-range hopping (3D-VRH) transport takes place between PEDOT-rich clusters which are separated by much thinner barriers, leading to an enhanced conductivity in this direction. This discussion is extended in Chapter 4, where a quantitative description of the length scales of the predominant transport is obtained. Particularly, it is demonstrated that the hopping process takes place between PEDOT-rich islands and not between single PEDOT segments or dopants in the lateral direction, whilst in the vertical direction the current limiting hopping transport occurs between dilute states inside the quasi-insulating PSS lamellas. By a post-treatment it is possible to modify PEDOT:PSS to raise its conductivity, by orders of magnitude. Typically, the addition of sorbitol to the aqueous dispersion of PEDOT:PSS that is used to deposit thin films via spin coating leads to an enhancement of the conductivity after thermal annealing. The causes and consequences of such behavior were investigated in detail. Chapter 5 describes the various properties of the highly conductive sorbitol-treated PEDOT:PSS, such as the conductivity itself, and the effects of thermal annealing and exposure to moisture. It is found that the conductivity enhancement upon addition of sorbitol is accompanied by a better environmental stability. Surprisingly, the electrical conductivity of PEDOT:PSS thin films without sorbitol treatment is increased by more than one order of magnitude in an environment with more than 30-35 % relative humidity. This effect is attributed to an ionic contribution to the overall conductivity. Thermal gravimetric analysis (TGA), direct insert probe-mass spectrometry (DIP-MS) and modulation differential scanning calorimetry (MDSC) were used as additional tools to demonstrate that, after thermal treatment, the concentration of sorbitol in the final PEDOT:PSS layer is negligibly small. In Chapter 6, scanning Kelvin probe microscopy (SKPM) is employed to measure the surface potential and work function of this PEDOT:PSS films that were deposited from water with different sorbitol concentrations. It is shown that work function of PEDOT:PSS is reduced with increasing sorbitol concentration. This shift can be explained by and is in agreement with- a reduction in the surface enrichment with PSS of the film. To study the charge transport properties of the highly conductive sorbitoltreated PEDOT:PSS films, temperature dependent and electric field dependent measurements are correlated with morphological analysis by STM in Chapter 7. It is found that by sorbitol treatment the hopping transport changes from 3DVRH to 1D-VRH. This transition is explained by a sorbitol-induced selforganization of the PEDOT-rich grains into 1D aggregates that are aligned within micrometer sized domains, as observed in STM images.

Thesis (Ph.D)--Mechanical Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Graham, Samuel; Committee Member: Garimella, Srinivas; Committee Member: Kippelen, Bernard; Committee Member: Melkote, Shreyes; Committee Member: Ready, Jud. Part of the SMARTech Electronic Thesis and Dissertation Collection.

The cardiac conduction system is vital for the initiation and maintenance of the heartbeat. Over the recent years, the zebrafish (Danio rerio) has emerged as a promising model organism to study this specialized system. The embryonic zebrafish heart’s unique accessibility for light microscopy has put it in the focus of many cardiac researchers. However, imaging cardiac conduction in vivo remained a challenge. Typically, hearts had to be removed from the animal to make them accessible for fluorescent dyes and electrophysiology. Furthermore, no technique provided enough spatial and temporal resolution to study the importance of individual cells in the myocardial network. With the advent of light sheet microscopy, better camera technology, new fluorescent reporters and advanced image analysis tools, all-optical in vivo mapping of cardiac conduction is now within reach. In the course of this thesis, I developed new methods to image and manipulate cardiac conduction in 4D with cellular resolution in the unperturbed zebrafish heart. Using my newly developed methods, I could detect the first calcium sparks and reveal the onset of cardiac automaticity in the early heart tube. Furthermore, I could visualize the 4D cardiac conduction pattern in the embryonic heart and use it to study component-specific calcium transients. In addition, I could test the robustness of embryonic cardiac conduction under aggravated conditions, and found new evidence for the presence of an early ventricular pacemaker system. My results lay the foundation for novel, non-invasive in vivo studies of cardiac function and performance.

Esta tese de doutorado é o resultado de um estudo dos mecanismos de operação de dispositivos poliméricos emissores de luz, com um particular enfoque nos processos de injeção e transporte de portadores de carga em polímeros derivados do poli(p-fenileno vinileno), PPV. Para tanto, se fez necessário o domínio de todas as etapas de produção e caracterização, desde a síntese química dos polímeros até a fabricação propriamente dita dos dispositivos, as quais são brevemente descritas neste trabalho. Basicamente, dois tipos diferentes de dispositivos foram caracterizados: diodos poliméricos emissores de luz (PLEDs), nos quais a camada ativa é composta por um filme fino (100-500 nm de espessura) do polímero eletroluminescente puro, e células eletroquímicas emissoras de luz (LECs), compostas por blendas do polímero conjugado com um eletrólito polimérico condutor iônico. As propriedades ópticas dos dispositivos foram analisadas através dos espectros de absorção óptica na região do ultravioleta/visível e de emissão (foto e eletroluminescência) enquanto as propriedades de injeção e de transporte de carga foram exploradas através de medidas elétricas de corrente-voltagem (I-V), espectroscopia de impedância no domínio da freqüência (condutividade ac), espectroscopia de fotocorrente e ressonância magnética detectada eletricamente (EDMR). A influência de parâmetros como a estrutura dos dispositivos, os metais utilizados como eletrodos e a temperatura permitiram uma análise mais detalhada de alguns modelos teóricos utilizados na interpretação dos resultados experimentais, fornecendo, dessa forma, um maior conhecimento das propriedades físicas dos materiais estudados.
This PhD thesis is an extensive study of the operation mechanisms of polymeric light-emitting devices, with a particular focus on the injection and transport properties of charge-carriers in poly(p-phenylene vinylene), PPV, derivatives. Therefore, it was necessary to dominate all the processes of fabrication and characterization of such devices, from the chemical synthesis of the polymers to the device fabrication, which are briefly described along this work. Two different kinds of devices were studied: polymeric ligh-emitting diodes (PLEDs) composed by a single thin layer (100-500 nm thick) of the pure electroluminescent polymer, and light-emitting electrochemical cells (LECs), which active layers are formed by a blend of the conjugated polymer and an ionic conductive polymeric electrolyte. The optical properties of the devices were analyzed by optical absorption in the ultraviolet-visible range and emission (photo- and electroluminescence) spectra. The charge injection and transport properties were studied by electrical measurements like current-voltage (I-V) curves, impedance spectroscopy in the frequency domain (ac conductivity), photocurrent spectroscopy and electrically detected magnetic resonance (EDMR). The influence of parameters like the device structure, the electrodes work function and the temperature allowed a detailed analysis of some theoretical models commonly used in the interpretation of the experimental results, providing more information about the physical properties of the studied conjugated polymers.

In this work, we demonstrate an inimitable liquid crystalline template strategy for the preparation of water dispersible electrically conducting poly(3,4-ethylenedioxythiophene) nanospindles (PEDOTSs). PEDOTSs were formed during the polymerization of the spindle shaped liquid crystalline phase of “EDOT–PDPSA” which was formed by the specific interactions of 3,4-ethylenedioxythiophene (EDOT) with 3-pentadecyl phenol-4-sulphonic acid (PDPSA). Liquid crystalline phases were characterized by Polarized Light Microscopic (PLM) analyses, rheology and XRD. Morphology and solid state ordering of conducting nanospindles were characterized by SEM, TEM and XRD. PEDOTSs exhibited an electrical conductivity of ~2.79 S cm⁻¹ and a good thermal stability (~300 °C), which suggests their applicability in fabricating high temperature electronic devices. Furthermore, electrochemical studies of PEDOTS modified glassy carbon electrodes (GCEs) showed an oxidation peak of ascorbic acid at a lower potential of 0.046 V with a peak current about 10 times (91.68 µA) higher than that of the bare GCE with excellent electrode stability, proposing that it can be used as a steady electrode for the electro-catalytic oxidation of similar molecules.

This thesis presents a comparative study between two silver nanoparticle inks that were deposited using a Drop-on-Demand (DoD) inkjet printer, aiming at finding a functional ink that can be used to print electrodes in Light-emitting Electrochemical Cells (LECs). To achieve this, a DoD inkjet printer was installed and an acquaintance with the printer was attained. Among the two inks, one was employed as received while the other was reformulated, and successful deposition of both the inks was observed. During the reformulation process, it was seen that the highly volatile tetrahydrofuran (THF) solvent can be used to improve the ink properties, in contrast to what is recommended. After that, the inks were deposited on UV-ozone treated glass substrates, sintered at an elevated temperature under ambient conditions, and their specific resistances and thicknesses were measured. Finally, the inks were used to print the anode in a structured sandwich-cell LEC. The performance comparison was conducted by observing the emitted light of the LECs. The results indicate that the reformulated ink performs better, probably due to the lower silver concentration that results in flatter surface, which in turn effectively alleviates shorts.

We present a novel top-electrode spray-coating process for the solution-based deposition of silver nanowires (AgNWs) onto vacuum-processed small molecule organic electronic solar cells. The process is compatible with organic light emitting diodes (OLEDs) and organic light emitting thin film transistors (OLETs) as well. By modifying commonly synthesized AgNWs with a perfluorinated methacrylate, we are able to disperse these wires in a highly fluorinated solvent. This solvent does not dissolve most organic materials, enabling a top spray-coating process for sensitive small molecule and polymer-based devices. The optimized preparation of the novel AgNW dispersion and spray-coating at only 30 °C leads to high performance electrodes directly after the deposition, exhibiting a sheet resistance of 10.0 Ω □−1 at 87.4% transparency (80.0% with substrate). By spraying our novel AgNW dispersion in air onto the vacuum-processed organic p-i-n type solar cells, we obtain working solar cells with a power conversion efficiency (PCE) of 1.23%, compared to the air exposed reference devices employing thermally evaporated thin metal layers as the top-electrode.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
Daylight can provides human health and well-being, as well as economic benefits. Daylight can creates interesting interiors supportive of human health and energy can be saved by dimming down or switching off electric lighting that are not needed. The surrounding, the building design and the daylight system are key elements of the greater or lesser possibility of use of the natural light. This Master s dissertation aims to study the potential use of the natural light, considering the minimum window size required on João Pessoa Paraíba Brazil legislation (JOÃO PESSOA, 1971) for residential spaces illuminated by pass-through and conduction components. A series of computer simulations were used in evaluating the daylight availability, provided by Daysim. There were carried on 480 simulations by associating five residencial rooms living room/bedroom 01; bedroom 02; maid s room; kitchen and bathroom and six design variants opaque and transparent sill; protruding and enclosed balcony; balcony s depth (1,20; 1,50; 2,00; 2,50 e 3,00 m), maximum plot ratio allowed; floor level (ground level and fourth floor); and North, East, South, and West facade orientations. Daylight Autonomy (DA) and Useful Daylight Illuminance (UDI) are the performance indicators used to predict the rooms performance using dynamic daylight simulations. Around 40% of the models have fell-short levels of Useful Daylight Illuminance. Protruding or enclosed balcony, opaque or transparent sill, and floor level affects the levels of natural lighting in rooms.
O uso da luz natural como fonte de iluminação além dos impactos positivos no bem-estar físico e mental do homem possui vantagens econômicas. A possibilidade de economia de energia elétrica depende da obtenção do nível de iluminamento requerido, de forma total ou complementar. O entorno e a edificação, através dos componentes de passagem e condução da luz, são elementos determinantes da maior ou menor possibilidade de aproveitamento da luz natural. Nesse aspecto, este trabalho tem como objeto de estudo o potencial de aproveitamento da luz natural, considerando as dimensões mínimas permitidas pelo Código de Obras de João Pessoa, em ambientes residenciais com sistema de iluminação natural composto de componentes de passagem associados a componentes de condução. O método para a análise do comportamento da luz natural foi simulação computacional, tendo sido o utilizado o software Daysim. Foram realizadas 480 simulações para cinco ambientes sala/quarto 01, quarto 02, quarto de empregados, cozinha e banheiro , associando três variáveis no componente de condução peitoril transparente e opaco; componente de condução saliente e encravado; e profundidade do componente de condução (1,20; 1,50; 2,00; 2,50 e 3,00 m) e três variáveis associadas ao entorno entorno construído a partir do critério de máxima ocupação do solo; altura do pavimento (térreo e 4º pavimento); e orientação (Norte, Leste, Sul e Oeste). Os parâmetros de análise foram a Iluminância Natural Útil (INU) e a Autonomia da Luz Natural (ALN). Considerando as variáveis e os parâmetros adotados, aproximadamente 40% dos modelos simulados apresentam iluminação natural insuficiente. Os fechamentos laterais (saliente ou encravado), a transparência desses fechamentos e o pavimento destacam-se como variáveis que interferem significativamente nos níveis de iluminação natural.

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Although the low level light therapy (LLLT) irradiation is indicated for a variety of musculoskeletal disorders like muscle fatigue, tissue repair and as anti-inflammatory agent, its effects on muscle activity are still poorly understood. The objective of this study was to evaluate the immediate effect of LLLT of irradiation on the nerve conduction velocity and electromyographic activity of the muscle upper trapezius (UT) in healthy subjects. Twenty healthy women (mean age 23.54  2.51) were included in this study, cross-over, controlled, randomized, double blind. Each volunteer has received two types of treatment with continuous LLLT (LLLT) and the other one with LLLT placebo (LLLTP). The treatment order was randomized by raffle, being included an interval of 7 days between each laser intervention (wash-out) to prevent residual effects. The surface electromyography (EMG) was used to verify the nerve conduction velocity (CV) and muscle activity UT during shoulder elevation in isometric contraction to 5 different levels of contraction (10, 15, 20, 25, 30% of maximum voluntary contraction), via visual feedback provided through a driving line. The collects of the EMG signal were performed before and after 30 minutes of treatment (LLLT or LLLTP). In the analysis of variance for repeated measures (ANOVA) it was possible to observe a significant decrease in the amplitude of the EMG signal to treatment with LLLT (p = 0.0001) but not to the placebo treated group (p < 0.05). Regarding of the CV, no change was observed for both treatments (LLLT: p > 0.05; LLLTP: p > 0.05 - ANOVA). In this study it could be observed an immediate effect of LLLT irradiation on the amplitude of the electromyographic signal of the trapezius muscle descending fibers in healthy individuals, but not on the nerve conduction velocity.
Embora a irradiação com laser de baixa potência (LBP) seja indicada para vários tipos de disfunções musculoesqueléticas como fadiga muscular, reparo tecidual e como agente anti-inflamatório, seus efeitos sobre a atividade muscular ainda são pouco conhecidos. O objetivo desse estudo foi avaliar o efeito imediato da irradiação do LBP sobre a velocidade de condução nervosa e a atividade eletromiográfica do músculo trapézio fibras descendentes (TFD) em indivíduos saudáveis. Vinte mulheres saudáveis (idade média: 23,54  2,51) foram incluídas nesse estudo, cruzado, controlado, randomizado duplo cego. Cada voluntária recebeu 2 tipos de tratamento com LBP (LBP) contínuo e outra com LBP placebo (LBPP). A ordem de tratamento foi randomizada por sorteio, sendo incluído um intervalo de 7 dias entre cada intervenção de laser (wash-out) para evitar efeitos residuais. A eletromiografia (EMG) de superfície foi utilizada para verificar a velocidade de condução nervosa (VC) e atividade no músculo TFD durante a elevação do ombro em contração isométrica em 5 diferentes níveis de contração (10, 15, 20, 25, 30% da contração voluntária máxima), por meio de feedback visual proporcionado por uma linha de treino. As coletas do sinal EMG foram realizadas antes e após 30 minutos do tratamento (LBP ou LBPP). Na análise de variância para medidas repetidas (ANOVA) foi possível observar diminuição significativa na amplitude do sinal EMG para o tratamento com LBP (p = 0,0001) porém não para o grupo tratado com LBPP (p < 0,05). Em relação à VC, nenhuma alteração foi observada para ambos os tratamentos (LBP: p > 0,05; LBPP: p > 0,05 - ANOVA). Nesse estudo foi possível observar um efeito imediato da irradiação com LBP sobre a amplitude do sinal eletromiográfico do músculo trapézio fibras descendentes em indivíduo saudáveis, porém, não sobre a velocidade de condução nervosa.

The dissertation thesis deals with optimization of the scintillation detector for efficient detection of low energy signal electrons in a specimen chamber of a scanning electron microscope. The solution was based on the study of signal electron energy loss mechanisms during their interaction with a conductive layer and a scintillator that can be studied using simulations based on the stochastics Monte Carlo methods. Based on test simulations and their comparison with experimental data, the ideal Monte Carlo software was chosen and used for the study of signal electron energy losses during their transport through the conductive layer as well as following interaction with scintillator, in dependency on the signal electron energy. Simulation results allowed to define criteria for the optimization of the conductive layer. According to these parameters, the optimized layers were deposited on the surface of different scintillators and experimentally tested in the scintillation detector of the scanning electron microscope. Experimental measurements allowed to verify accomplished simulations and provide new information about impact of materials and thicknesses of conductive layers in combination with materials of scintillators and light guides. The increase of the detection efficiency of the scintillation detector equipped with optimised conductive layers and its capability to detect low energy signal electrons were experimentally proved.

Ce travail de thèse a porté sur l'élaboration de nanoparticules et de couches minces d'oxydes spinelles mixtes de MxCo2-xMnO4 (M = Ni, Cu, Zn ; x = 0, 0,15, 0,30, 0,60) semi-conducteurs, absorbants de lumière avec d'intéressantes applications potentielles pour la photo-catalyse et le photovoltaïque. Le premier chapitre présente tout d'abord une vue globale du contexte énergétique à l'échelle mondiale et des ressources d'énergie renouvelables, alternatives aux énergies fossiles les plus répandues. Une revue détaillée est ensuite faite des différents matériaux et systèmes employés dans la fabrication de cellules solaires, en portant une attention plus particulière à un nouveau type de cellules photovoltaïques en couches minces, dites " Tout-oxyde ", basées notamment sur l'utilisation d'oxydes de type spinelle utilisés comme absorbeurs solaires. Le deuxième chapitre présente les techniques expérimentales de synthèse et de caractérisation utilisées lors de ce travail de thèse. Le procédé de polycondensation inorganique, optimisé au laboratoire, utilisé pour synthétiser les poudres d'oxydes à basse température (T < 120 °C) sans agent organique complexe est décrit. Ensuite, les méthodes de préparation de dispersions colloïdales à l'ambiante dans l'éthanol et de films minces homogènes d'oxydes par trempage-retrait sont explicitées. Le troisième chapitre présente les résultats détaillés des structures atomiques et électroniques des matériaux de base à l'étude, issus de calculs par la méthode Density Functional Theory (DFT), réalisés en collaboration avec le laboratoire CEMES de Toulouse. Les résultats des calculs de densités électroniques et détermination de structures de bandes, réalisés pour la première fois à notre connaissance, sur l'ensemble de la solution solide MnxCo3-xO4 (0 = x = 3), sont comparés à nos données expérimentales, obtenues notamment sur les largeurs de bande interdite (gap) à partir de mesures optiques faites sur couches minces. Un gap de 0,8 eV est calculé, qui serait dû à des transitions inter-métalliques en sites B. Deux gaps à 1,5 et 2,2 eV, obtenus expérimentalement dans l'UV-VIS, qui augmentent avec la quantité de manganèse, correspondraient à des transitions respectives B-A et O-B, respectivement. Les propriétés magnétiques de ces matériaux sont également discutées. Le quatrième chapitre présente l'élaboration et la caractérisation (micro-)structurale des poudres et des couches minces d'oxydes de type spinelle. Toutes les compositions (Co2MnO4 dopé au Ni, Cu ou Zn) cristallisent dans une phase cubique. Les nanoparticules sont sphériques avec la taille variant entre 20 et 50 nm. Les couches minces homogènes ont été déposées sur quartz, alumine, nitrure de titane et platine afin de mesurer leurs propriétés électriques et optiques. Une température de frittage environ de 1000 °C sous air a été déterminée par dilatométrie et les couches sont stables jusqu'à 900 °C quel que soit le substrat. En revanche, seules les couches déposées sur platine permettent d'atteindre la température de frittage sous air (et d'accroitre la compacité donc la conductivité des couches) sans réaction avec le substrat. Le chapitre cinq présente les variations des propriétés optiques et électriques des couches minces avec le frittage. Les propriétés d'absorbance de lumière des couches minces ainsi préparées, mesurées sur une gamme de longueurs d'ondes du domaine spectral UV-visible, montrent deux bandes d'absorbance, correspondantes à deux valeurs de gap pour chaque composition. La propriété d'absorbance des couches minces augmente dans la gamme du visible après frittage et les gaps diminuent. Les couches minces sont plus compactées. La résistivité des couches minces diminue de 105 à 102 Omega.cm avec l'augmentation de la température de 20 à 300 ºC. Une étude parallèle, basée sur la préparation de films minces absorbants de lumière de Co2MnO4 et Cu2O par la technique de Pulsed Laser Deposition (PLD) est également présentée
The present thesis deals with the synthesis and structural characterization of transition metals doped cobalt and manganese based spinel oxides MxCo2-xMnO4 (with M = Ni, Cu, Zn and x = 0, 0.15, 0.30, 0.60), in relationships with their conduction and optical properties. These materials are good p-type semiconductors and light absorbers in the UV and visible regions, therefore interesting for photo-catalysis and photovoltaics. The first chapter is a brief overview of the energy context and nature of global warming, renewable energy resources and a literature review of materials used for solar cells including the newly studied system type based on all-oxide photovoltaics. Chapter two presents all the experimental methods and characterization techniques used for this research work. The inorganic polycondensation method optimized in our laboratory and used for synthesizing spinel oxide powders at low temperature (T < 120 °C) without complex organic agents is described. Then, the preparation of colloidal dispersions stabilized at room temperature using an azeotrope solution based on absolute ethanol and water only is described, in order to obtain homogenous oxide thin films by the dip-coating technique. The third chapter presents detailed results on the atomic and electronic structures of the materials under study performed by using a full density functional theory investigation thanks to a collaboration with the CEMES. First principles electronic structure calculations were performed for the first time to our knowledge over the whole spinel oxide solid solution range MnxCo3-xO4 (0 = x = 3), and compared with our experimental data. A small band gap of ~ 0.8 eV is calculated, due to metal-metal transitions in B sites. The experimental band gaps observed at 1.5 and 2.2 eV, which increase with the amount of manganese, would correspond to B-A and O-B transitions, respectively. The magnetic properties of these materials are also discussed. Chapter four shows the experimental details of the preparation and characterization of the spinel oxide powders, colloidal dispersions and thin films. All samples (Ni, Cu or Zn-doped Co2MnO4) are well crystallized with a single cubic spinel oxide phase. Nanoparticles are spherical and their diameters vary from 20 to 50 nm, doping with Zn, Ni to Cu, mainly due to steric effects. Homogenous oxide thin films were deposited on quartz, alumina, titanium nitride and platinum in order to measure their optical and electrical properties, and to increase the film compactness (thus electrical conductivity and light absorbance) after thermal treatment. Thin films are well preserved up to 900 °C in air and can handle higher temperatures (up to 1000 ºC) on platinum without reaction with the substrate. Chapter five deals with the optical and electrical properties of thin films before and after sintering. The optical properties were measured over a wide range of wavelengths (UV-VIS). The optical properties of spinel oxide thin films show two strong absorption band gaps for each composition at the UV front and close to 700 nm in wavelength. These band gaps are direct and mostly lower than 2 eV for the first band. Both band gaps increase with further doping and decrease after annealing. Thin film resistivity is about 105 .cm at room temperature and decreases with increasing temperature (a few tens of 20cm at 300 ºC). In parallel to the soft chemistry method and dip-coating technique used to prepare our spinel oxide thin layers, Pulsed Laser Deposition technique was used to prepare pure Co2MnO4 and Cu2O dense thin films. Their structural and optical main features are discussed

Thin film solar cells, if film thickness is thinner than the optical absorption length, typically give lower cell performance. For the thinner structure, electric current loss due to light penetration can offset the electric current gain obtained from higher built-in electric field. Light trapping schemes can increase the effective optical absorption length and thus enhance the electric current for thinner solar cells. Here a new light trapping scheme based on light trapping transparent conducting oxide layer (LT-TCO) is proposed to enhance the performance of thin film solar cells. Three different configurations of integrating the LT-TCO layer in solar cells are proposed and evaluated. This research aims to develop the LT-TCO layer with surface texture and good conductivity by pulsed laser deposition (PLD) technique at low temperature. The LT-TCO layer is fabricated by PLD deposition of Al-doped ZnO to achieve multilayer films by tuning of oxygen pressure. The light trapping effect is examined by optical transmittance measurement and the surface texture is characterized by transmission electron microscopy (TEM) technique. The conductivity of LT-TCO layer is measured by resistivity measurement. Thin film CdTe/CdS solar cells are fabricated by PLD technique to develop baseline solar cells for integration of LT-TCO layer. The as-deposited thin film solar cells show relatively low performance and are further processed with various post-deposition treatments to seek efficiency enhancement. The effects of different processes on cell performance are examined by electrical, optical, and microstructure studies. Air annealing of CdS layer and CdCl2 treatment of CdTe layer combined are found to yield the best cell performance. The fabrication issues that limit the cell performance are discussed and future optimizations in fabrication processes are suggested.

碩士
國立臺灣師範大學
物理學系
104
Graphene is a two-dimensional carbon material which consists of hexagonal array of carbon atoms, and offers exceptional characteristics such as high transparency, low sheet resistance, suppleness, etc. In this study, we show that chemical vapor deposition grown graphene on copper foil and transfer it on p-GaN as light-emitting-devices transparent conducting electrode. To decrease Schottky barrier between graphene and p-GaN interface, we deposit Ni nanolayer on p-GaN substract as a buffer layer between graphene and p-GaN. After deposited 3 nm thickness nickel (Ni thin film) on p-GaN surface, followed by placing the sample in an oxygen-containing gas to 400°C thermal annealing for 3 minutes, so that the nickel layer is converted into nano nickel oxide (NiOx) dots. NiOx dots haave high transparency at blue light and UV light region. Follow the graphene transferred to do a thermal anneal make graphene with NiO / p-GaN close contact, in order to reduce the Schottky barrier between graphene and the p-GaN thus forming an ohmic contact on nickel oxide. Finally, using a circular transmission line model (CTLM) for electrical resistance measurements.

碩士
國立成功大學
微電子工程研究所碩博士班
96
The purpose of this research is to lower the forward turn-on voltage of the GaN-based LED by using In2O3 as the contact layer to p-GaN, and then improve the luminous intensity of the GaN-based LEDs. Although the ITO has broadly applied to GaN-based LEDs as the transparent current spreading layer, however, ITO on p-GaN shows poor ohmic characteristics, which increases the specific contact resistance and makes the forward turn-on voltage of GaN-based LEDs larger, and consequently lowers the luminous intensity of the GaN-based LEDs. In2O3, with features such as high transmittance, and high band gap, is an excellent material for current spreading layer. This experiment used E-beam as the deposition technology to deposit the In2O3 and ITO on p-GaN, respectively, as the transparent current spreading layer of GaN-based LEDs. In this thesis, we compare the GaN-based LEDs with In2O3/ITO and ITO p-electrodes. From the results of the experiment, the LED with In2O3/ITO electrodes shows lower operation voltage and higher luminous intensity. Moreover, we create the 3 μm hole-diameter, 3 μm spacing and 47 nm depth pattern by using photolithography and wet-etching process in order to extract more light out diffuse. Compared with the planar LED, the hole-patterned LED shows higher EL intensity but higher operation voltage.

碩士
國立交通大學
顯示科技研究所
94
Recently, polarized polymer light-emitting diodes (PLEDs) have been studied extensively because of their great potential to replace the backlight module and the linear polarizer of thin-film transistor liquid crystal displays (TFT-LCDs). In order to fabricate highly polarized PLEDs, in this thesis, we firstly focus on the analysis of several factors which affect the arrangement of polyfluorenes, such as the concentration of solutions, spin rates, annealing time, and annealing temperature. It is found that polyfluorenes align more ordered while the concentration of polymer solution is lower. The spin rates should be optimized to achieve the best alignment of polymer chains while using different concentration of solutions. On the other hand, the solvent effect should be considered since it will affect the morphology of polyfluorenes. Moreover, at low annealing temperature, the alignment of polymers will be improved apparently by increasing the annealing time. However, it becomes almost independent at higher annealing temperature. Then, highly polarized PLEDs adopting a novel conducting alignment layer, consisting of PEDOT:PSS and PVA, have been successfully accomplished. For PF2/6, a high dichroic ratio can not be obtained while using conventional mechanical-rubbing method and neat PEDOT:PSS (Al 4071) as the alignment layer. After blending PVA with PEDOT:PSS as alignment layer, the maximum dichroic ratio and its integral value in visible region of photoluminescence are 7.11 and 6.58, respectively. In addition, the maximum dichroic ratio and its integral value of electroluminescence (at 548 nm) are 16.2 and 16.1, respectively. They are seven and sixteen times larger than those while using neat PEDOT:PSS as the alignment layer, respectively.

Conducting metallopolymers have been investigated for a variety of applications due to their ability to take advantage of both the mechanical processability of the polymer material, as well as the optical and electronic properties of the metal. Our project goal is to design, synthesize and characterize novel iridium(III)-containing conducting metallopolymers for use as the active layer in polymer light-emitting diodes. We have utilized thiophene functionalized ligands that can be readily electropolymerized into conducting polymer thin films and can be easily incorporated into a device structure. Iridium(III) was chosen as the metal center due to its promising photophysical properties, as similar complexes have demonstrated high luminescent quantum yields and short phosphorescent lifetimes. The coordination environment around the metal can be altered synthetically to tune the emission wavelength across the visible spectrum. The synthetic control over the polymer backbone, as well as the iridium(III) ligand environment, allowed us to independently vary each component, which has provided a variety of materials. The materials are characterized through 1H and 13C NMR, mass spectrometry, elemental analysis, electrochemistry, X-Ray diffraction and X-Ray Photoelectron Spectroscopy. The photophysical properties of the materials are studied through UVvii Visible absorption spectroscopy, UV-Vis-NIR spectroelectrochemistry and steadystate/ time-resolved emission spectroscopy.
text

碩士
國立成功大學
電機工程學系專班
100
Zinc oxide as a wurtzite structure of the wide band gap semiconductor has a significant c-axis growth orientation, transparency and piezoelectric pressure light effect which is widely used in optoelectronic materials. The resistivity of the zinc oxide is generally high and its conductivity is mainly governed by the oxygen vacancies and interstitial zinc atoms. The electrical conductivity and light transmittance of zinc oxide is influenced by the preparation parameters. Therefore, Aluminum doped ZnO developed to improve the optical and electrical properties and thus replacing the traditional ITO material recently. In order to study the impact and applications of this special crystalline ZnO thin films, ZnO:Al film deposited on the glass substrate and deposition has been coated with zinc oxide thin films to explore the RF power, chamber pressure and film thickness as the experimental parameter tested, the final and intermediary layer of ZnO is used in OLED in order to improve the overall optical and electrical properties.

碩士
國立成功大學
光電科學與工程研究所
95
In this study, transparent and conductive AZO:Y2O3 (AZO:Y) thin films are performed as the potential transparent contact layer on nitride-based light emitting diodes. When the DC power of 150W, it showed a lowest resistivity of 6.89×10-4 Ω-cm and a carrier concentration of 3.61×1020 cm-3 and a mobility of 25.1 cm2/V-s that the thermal annealing at 700�aC for 1 min in nitrogen ambient. And the AZO:Y films showed high transmittance (>85%) in the visible wavelength range after thermal annealing. We had demonstrated the AZO:Y films and ITO films as ohmic contacts on p-type GaN . The I-V characteristic of AZO:Y contact on p-GaN was not a perfect ohmic property after thermal annealing. And the ITO contact on p-GaN was an ohmic property after thermal annealing at 600°C for 5min in nitrogen ambient. The lowest specific contact resistance of AZO:Y and ITO contact on p-GaN was 1.45×10-1 and 7.8×10-2Ω-cm2, respectively. GaN-based LEDs with ITO and AZO:Y contact layers were fabricated for the optoelectrical characteristics study. The forward voltage (light output power) was 3.375 V (3.59mW) and 3.55 V (3.96mW) for the LEDs with ITO and AZO:Y contact layer under 20mA current injection, respectively. The forward voltage of the LED with AZO:Y contact layer was slightly higher 0.2V than the LED with ITO contact under 20mA current injection. However, the light output power of the LED with AZO:Y contact layer is larger 10% than the LED with ITO contact under 20mA current injection. Inserting the ITO contact layer between p-GaN and AZO:Y can be improved the electrical properties of LEDs. The forward voltage of LED with ITO/AZO:Y contact layer was 3.2V under 20mA current injection and was successfully 0.35V lower than the LED with AZO:Y contact. These results revealed that the AZO:Y film is promising as alternative to ITO for transparent electrode application on GaN-based light-emitting diode.

Yip Hin-lap = 以PEDOT:PSS為本的高份子發光器件中銦的擴散之研究 / 葉軒立.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2003.
Includes bibliographical references (leaves 113).
Text in English; abstracts in English and Chinese.
Yip Hin-lap = Yi PEDOT:PSS wei ben de gao fen zi fa guang qi jian zhong yin de kuo san zhi yan jiu / Ye Xuanli.
Abstract --- p.ii
論文摘要 --- p.iv
Acknowledgements --- p.v
Table of Contents --- p.vi
List of Figures --- p.x
List of Tables --- p.xii
Chapter CHAPTER 1 --- INTRODUCTION --- p.1
Chapter 1.1 --- Overview --- p.1
Chapter 1.2 --- Conjugated Polymer --- p.3
Chapter 1.2.1 --- Electronic and Geometric Configuration --- p.3
Chapter 1.2.2 --- Charge Carriers --- p.7
Chapter 1.2.3 --- Concept of Doping --- p.9
Chapter 1.2.4 --- Electrical Conductivity and Charge Transport Mechanisms --- p.15
Chapter 1.3 --- "Poly(3,4-ethylenedioxythiophene) [PEDOT]" --- p.16
Chapter 1.4 --- Polymer Light Emitting Diodes --- p.20
Chapter 1.4.1 --- Device Fabrication --- p.21
Chapter 1.4.2 --- Material Design and Properties --- p.23
Chapter 1.4.3 --- Interface and surface of PLED --- p.25
Chapter 1.5 --- """Chemistry"" and Diffusion at Interface" --- p.27
Chapter 1.6 --- Surface/Interface Modification with Self-Assembled Monolayers --- p.30
Chapter 1.7 --- Aims of This Thesis --- p.33
References --- p.34
Chapter CHAPTER 2 --- INSTRUMENTATION --- p.38
Chapter 2.1 --- X-ray Photoelectron Spectroscopy --- p.38
Chapter 2.1.1 --- Fundamental Theory of XPS --- p.39
Chapter 2.1.2 --- Qualitative Analysis using XPS --- p.43
Chapter 2.1.2.1 --- Chemical Shifts --- p.43
Chapter 2.1.2.2 --- Shake-up satellites --- p.45
Chapter 2.1.2.3 --- Valence band structure --- p.45
Chapter 2.1.3 --- Quantitative Analysis Using XPS --- p.46
Chapter 2.1.4 --- Depth Profiling --- p.47
Chapter 2.1.4.1 --- Non-Destructive Method Using Angled-Resolved XPS --- p.47
Chapter 2.1.4.2 --- Destructive Method Using Ion Sputtering --- p.49
Chapter 2.1.5 --- Instrumental Setup of XPS --- p.49
Chapter 2.2 --- PLED Fabrication and Characterization System --- p.51
Chapter 2.3 --- Current-Voltage-Luminescence (I-V-L) Measurement --- p.53
Chapter 2.4 --- Electrical Measurement --- p.54
Chapter 2.5 --- Kelvin Probe Measurement --- p.55
Chapter 2.6 --- pH Measurement --- p.56
Chapter 2.7 --- Film Thickness Measurement --- p.56
Chapter 2.8 --- Contact Angle Measurement --- p.57
References --- p.60
Chapter CHAPTER 3 --- STABILITY OF PEDOT:PSS/ITO INTERFACE --- p.61
Chapter 3.1 --- Introduction --- p.61
Chapter 3.2 --- Sample Preparation --- p.62
Chapter 3.3 --- Results and Discussion --- p.63
Chapter 3.3.1 --- XPS of Core levels in PEDOT:PSS --- p.63
Chapter 3.3.1.1 --- XPS of S 2p Core Level --- p.64
Chapter 3.3.1.2 --- XPS of O Is Core Level --- p.66
Chapter 3.3.1.3 --- XPS of C Is Core Level --- p.68
Chapter 3.3.2 --- Composition Analysis of PEDOT:PSS Films --- p.71
References --- p.80
Chapter CHAPTER 4 --- ELECTRICAL AND ELECTRONIC PROPERTIES OF PEDOT:PSS WITH DISSOLUTED INDIUM --- p.81
Chapter 4.1 --- Introduction --- p.81
Chapter 4.2 --- Sample Preparation --- p.81
Chapter 4.2.1 --- Four-Point Probe Measurement --- p.82
Chapter 4.2.2 --- Current-Voltage Measurement --- p.82
Chapter 4.2.3 --- Work Function Measurement --- p.83
Chapter 4.2.4 --- XPS Experiment --- p.83
Chapter 4.3 --- Results and Discussion --- p.85
Chapter 4.3.1 --- Electrical Properties of PEDOT:PSS --- p.86
Chapter 4.3.2 --- Electronic Properties of PEDOT:PSS --- p.89
References --- p.97
Chapter CHAPTER 5 --- BLOCKING REACTIONS BETWEEN ITO AND PEDOT:PSS WITH A SELF-ASSEMBLY MONOLAYER --- p.98
Chapter 5.1 --- Introduction --- p.98
Chapter 5.2 --- Sample Preparation --- p.99
Chapter 5.3 --- Result and Discussion --- p.103
Chapter 5.3.1 --- In Diffusion Blocking Effect by SAM --- p.103
Chapter 5.3.2 --- PLED Devices Performance --- p.107
References --- p.113
Chapter CHAPTER 6 --- CONCLUSION --- p.114
Chapter CHAPTER 7 --- FURTHER WORKS --- p.116

碩士
國立成功大學
光電科學與工程研究所
96
In this study, the conductive transparent AZO:Y2O3 (AZO:Y) thin films were deposited by electron-beam evaporator. The resistivity of the as deposited AZO:Y film by sputter is more than 1.00×10-2Ω-cm. However, the resistivity of AZO:Y thin films deposited at 350oC without any thermal annealing could be lowered to 6.95×10-4Ω-cm and had optical transmittance more than 90% in visible regions. We had demonstrated the electrical properties and the optoelectrical characteristics of AZO:Y and ITO transparent contact layers (TCL) onto p-GaN and LEDs, respectively with different thermal annealing temperatures. The AZO:Y/p-GaN and ITO/p-GaNcontacts exhibited a Ohmic electrical characteristic without thermal annealing. The specific contact resistance of as-dopsited AZO:Y and ITO contact on p-GaN were 3.36×10-2 and 2.95×10-2 Ω-cm2, respectively. The specific contact resistance of AZO:Y/p-GaN was almost the same as the same as deposited AZO:Y/p-GaN after thermal annealing in 500~800 oC for 1 min in N2 ambient. The AZO:Y thin films contact onto p-GaN shows the better thermal stability than the ITO/p-GaN. The forward voltage(Vf) at 20mA of the LEDs with AZO:Y TCL with annealing temperatures of as-deposit, 500, 600, 700 and 800 were 3.3V, 3.31V, 3.32V, 3.31V, 3.29V, respectively. And the output power of LED with AZO:Y TCL decreased with increasing the annealing temperature. The LED with ITO TCL were processed to compare with the LED with AZO:Y TCL. The Vf (output power) at 20mA of the AZO:Y and ITO TCL LEDs were 3.30V(5.49mW) and 3.27V(4.93mW), respectively. The Vf of the LED with AZO:Y TCL was almost the same as the LED with ITO TCL under 20mA current injection. However, the light output power of the LED with AZO:Y TCL is 11.4% higher than the LED with ITO TCL under 20mA current injection. The improvement of the output power of LED with AZO:Y could be from the fact that the light transmittance of AZO:Y thin film is higher than which of ITO thin film. It is highly probable and promising that the AZO:Y thin film deposited by electron-beam evaporator could be a replacement to ITO thin film for transparent electrode application on GaN-based light-emitting diode.

博士
國立中興大學
材料科學與工程學系所
107
In this dessirtation, the atomic layer deposition (ALD) was employed to deposite the zinc oxide (ZnO) and Al-doped ZnO (AZO) thin films on the glass substrates. Various Zn:Al cycle ratios of precursors were utilized to control the Al composition of the AZO thin film during the ALD process. In our experimental range, the Zn:Al cycle ratios of AZO thin films were ranged from 25:1 to 15:1, where the electrical properties of the polycrystalline AZO thin films showed strong dependence on the Al composition. When increasing the Al concentration, the AZO films crystallized referentially along the [100] direction to cause the d-spacing decreased. It could be due to the Al atoms incorporate into substitution for Zn lattice sites. A lowest resistivity of 8.0410−4 -cm was observed for AZO thin film (Zn: Al=20:1) with Al-doping of 3.77 at. %. Transmittances of ZnO and AZO thin films with various Zn:Al cycle ratios were higher than 85 % in the visible region. The contact properties of the ZnO/p-GaP:C and AZO/p-GaP:C were found to be significantly altered from Schottky contact to ohmic contact after the 350 C/1 min rapid thermal annealing treatment. The contact behavior between ZnO/p-GaP:C and AZO/p-GaP:C was further characterized by the analyses of secondary ion mass spectrometer and x-ray photoelectron spectroscopy. In our experiments, the optimum specific contact resistance of the AZO thin film (Zn: Al=20:1) contacted with p-GaP:C was achieved to be 6.310−3 /cm2. The atomic diffusion behavior of ZnO/p-GaP:C and AZO/p-GaP:C was also characterized by the angle-resolved X-ray photoelectron spectroscopy. After the thermal annealing process, the Zn-atom in the ZnO and AZO layers markedly diffused into the p-GaP:C layers. Meanwhile, the Ga-atom diffused out from the p-GaP:C layer. Then, Zn atoms occupy the Ga vacancies. It not only increased the doping concentration in the near-surface region of p-GaP:C but also reduced the depletion region width of the semiconductor region. Therefore, numerous carriers will be tunneling through the reduced Schottky barrier and form the ohmic contact. Finally, the ZnO and AZO thin films act as current spreading layer to fabricate phosphide LEDs. The ZnO and AZO thin films with different Zn:Al cycle ratio of 25:1, 20:1 and 15:1 were grown by ALD on the top of p-GaP:C window layer for comparison. The droop efficiency and junction temperature of the LEDs were improved AZO thin films which result in increasing the light output power and thermal stability of the LEDs. The droop efficiency of LED with ZnO and AZO thin films with Al composition of 2.87 %, 3.77 %, and 4.06 % were 41 %, 31 %, 15 % and 39 % respectively. The junction temperature of LEDs with ZnO thin film was 58.1 oC. The junction temperature of LEDs with AZO thin films for Zn:Al cycle ratio of 25:1，20:1 and 15:1 were 51.7 oC, 39.6 oC and 55.5 oC under 700 mA injection current. Based on these results, the performance of the p-side-up thn-film AlGaInP LED structure can be further improved with the ALD-AZO current spreading layer with optimum Al composition.

碩士
國立成功大學
光電科學與工程研究所
96
In this study, We focused on the mechanism for Ohmic contact of AZO:Y formation on as-grown and as etched differently doped n-GaN.The specific contact resistance of the AZO on n-GaN was reduced by the Cl2 plasma treatment on n-GaN in inductive coupled plasma etcher. The Cl2 plasma treatment on n-GaN might generate the nitrogen (N) vacancies on the surface of plasma damaged n-GaN layer and lead to reduce the specific contact resistance of the AZO on plasma damaged n-GaN layer. The ohmic characteristics of the AZO on n-GaN could be affected by the thermal annealing. We found that the specific contact resistance would increase with increasing annealing temperature when the thermal annealing temperature higher than 600�aC The annealing temperature to form a good ohmic contact of AZO on p-GaN was not higher than 600�aC. That means we could deposit the AZO on p-GaN and n-GaN at same time as the transparent contact of the n and p-type GaN of the LEDs The light output power of the LED could be improved by changing pattern of the n-electrode and light extraction with AZO transparent n-contact. We use simple fabrication method and an innovative geometrical design on n type electrode pattern for GaN- based light-emitting diodes(LEDs) were investigated based on current spreading phenomenon and light output power . GaN-based LEDs with conventional and AZO:Y finger light- emitting diodes(LEDs) were fabricated for the optoelectrical characteristics study. The forward voltage (light output power) was 3.46V (2.31mW) and 3.47 V (2.39mW) under 20mA current injection, respectively. It was found that light output power was enhanced around 3.5%.

The byproducts of human engineered energy production are increasing atmospheric CO2 concentrations well above their natural levels and accompanied continual decline in the natural reserves of fossil fuels, necessitates the development of green energy alternatives. Solar energy is attractive because it is abundant, can be produced in remote locations and consumed on site. Specifically, thin-film silicon-based photovoltaic (PV) solar cells have numerous inherent advantages including their availability, non-toxicity, and they are relatively inexpensive. However, their low-cost and electrical performance depends on reducing their thickness to as great an extent as possible. This is problematic because their thickness is much less than their absorption length. Consequently, enhanced light trapping schemes must be incorporated into these devices. Herein, a transparent and conducting photonic crystal (PC) intermediate reflector (IR), integrated into the rear side of the cell and serving the dual function as a back-reflector and a spectral splitter, is identified as a promising method of boosting the performance of thin-film silicon-based PV. To this end a novel class of PCs, namely selectively transparent and conducting photonic crystals (STCPC), is invented. These STCPCs are a significant advance over existing 1D PCs because they combine intense wavelength selective broadband reflectance with the transmissive and conductive properties of sputtered ITO. For example, STCPCs are made to exhibit Bragg-reflectance peaks in the visible spectrum of 95% reflectivity and have a full width at half maximum that is greater than 200nm. At the same time, the average transmittance of these STCPCs is greater than 80% over the visible spectrum that is outside their stop-gap. Using wave-optics analysis, it is shown that STCPC intermediate reflectors increase the current generated in micromorph cells by 18%. In comparison, the more conventional IR comprised of a single homogeneous transparent conducting oxide film increases the current generated in the same cell by just 8%. Moreover, the benefit of using STCPC IRs in building integrated photovoltaics is also presented.

碩士
國立中央大學
光電科學研究所
96
In this study, we adopt E-Gun evaporation system to deposit Gallium doped Zinc Oxide (GZO). We analyze the optical and electrical properties of GZO thin film and also discuss the contact property on p-GaN. Finally, we compare the electrical and optical characteristics of GZO TCL LEDs with conventional ITO TCL LEDs. At the Ga content of 6At.%, we obtained the lowest resistivity (ρ) was 2.44×10-4 ohm-cm which was at the same order of ITO thin film (1×10-4 ohm-cm) and the transmittance was the above 90% at visible range which was comparable with ITO thin film. We prepared two as-deposited GZO films on p-GaN and LEDs of different resistivities, 6.31×10-4 ohm-cm (P-1) and 3.56×10-4 ohm-cm (P-2), to study the electrical contact property and compared with ITO film with resistivity of 1.73×10-4 ohm-cm (P-ITO). The specific contact resistances (ρc) of P-1, P-2 and P-ITO were 7.49×10-1 ohm-cm2, 1.48×10-1 ohm-cm2 and 2.61 ×10-2 ohm-cm2, respectively. After the chip process, we characterized the electrical and optical properties of GZO-LEDs and ITO-LEDs at the injection current of 20mA. The forward voltage of GZO LED-1, GZO LED-1 and ITO-LED were 3.89 V, 3.47 V and 3.35 V, respectively. The forward voltage of GZO-LEDs exhibited 0.54V and 0.12V higher than that of ITO-LED. The output powers were 2.02mW, 1.98mW, and 1.7mW for GZO LED-1, GZO LED-2 and ITO LED, respectively. The output powers were enhanced by 19% and 16% for GZO LED-1, GZO LED-2 compared with that of ITO-LED. On the other hand, the external quantum efficiency were 3.63% and 3.55% for GZO LED-1, GZO LED-2 which showed 18.6% and 16% enhancement compared with that of ITO-LED,3.06%. We also did annealing process for GZO films and then did the chip process. However, we found that? ρ and ρc would be deteriorated after annealing process. At 20mA injection current, the forward voltages were higher than those as-deposit and degradations of EQE and output powers were also observed.

碩士
國立成功大學
光電科學與工程研究所
97
In this study the conductive and transparent In-doped ZnO (IZO) thin films were deposited by electron-beam evaporator to be the transparent contact layers for nitride-based light emitting diodes. We focus on the optimization of the electrical and optical properties of IZO films by varying the deposition conditions. It was found that the resistivity of as-deposited IZO thin films deposited at 250℃ with oxygen flow rate 5sccm could be as low as 1.32×10-3 Ω-cm and the optical transmittance is about 75%~82% in visible spectrum regions. It was also found that the specific contact resistance of IZO contact on p-GaN was 3.61×10-2 Ω-cm2. After thermal annealing in 500℃~800℃ for 1 min in N2 ambient, the optical transmittance of IZO thin films were increased about 10%. In contrast, the resistivity of IZO was increase with increasing the annealing temperature. It was found that the resistivity of IZO was 3.76x10-2 Ω-cm2 at 800℃ annealing temperature. Besides the forward voltage(Vf @20mA) of the IZO TCL LEDs with different annealing temperatures of as-deposit, 500, 600, 700 and 800℃were 3.78V, 4.15V, 5.99V, 3.81V and 3.34V, respectively. The output power of IZO LED annealed at 800oC is about 14% less than that of as-deposited IZO LEDs even though the low Vf of 3.34V of 800oC annealing IZO LED was reached. The deteriorated output power of the 800oC annealing IZO LED might be attributed to the worse current spread of the increased IZO TCL resistivity with 800oC annealing.

碩士
國立成功大學
微電子工程研究所碩博士班
94
In the mid-1990s, nitride-based material was first successfully grown on sapphire by Shuji Nakamura of Nichia co. using Metal Organic Chemical vapor deposition (MOCVD) technology. Up to now, lots efforts have been made in the promotion of light extraction and efficiency of blue GaN-based LEDs. Owing to its advantageous of small volume, long life, fast responding time, low power consumption, lasting, better quality of reliability, smaller flexible lighting fixtures, intrinsically safety, and no mercury added, a novel solid-state white lighting source, so called " new generation lighting source " has been proposed using blue GaN-based LEDs and yellow phosphor powder or direct combination of lights emitting from RGB color LEDs. However, challenging issues of GaN-based LEDs including poor light conversion efficiency and poor thermal conducting caused by the sapphire substrate, and non-scalable light output with respect to the chip size, etc., are still open questions. This thesis aims to tackle the challenging issues of present GaN-based LEDs. Various methods including replacing the sapphire substrate with an electroplating substrate by patterned laser lift-off (patterned LLO) technology, depositing a sputtered-Indium-Zinc Oxide film as a current spreading layer atop n-GaN layer for the fabricating of 40 mil-high power vertical-structured metallic GaN-based LEDs (VM-LEDs) were proposed. Using a KrF excimer laser (248 nm) and nickel electroplating, it takes about 10 min for the transfer of GaN epi-layer from 2” sapphire substrate to Ni substrate with an acceptable yield(>50%). According to the material analysis and optoelectronic characterizations, the measured optoelectronic performances of VM-LEDs reveal a great improvement as compared to that of conventional lateral-structured LEDs. In experiments, the use of inductive coupling plasma (ICP) dry-etching to increase the carrier concentration of n-GaN layer and sputtered-IZO as a transparent conducting layer to enhance current spreading was demonstrated and discussed. As compared to regular-LEDs under an injection current of 350 mA, the series resistance of VM-LEDs was lowered by about 60% and forward voltage drop was also decreased by 0.3 ~ 0.5 V, and the increase in light output power (LOP) is about 97% have been obtained. It is expected that the use of LLO in conjunction with Ni substrate and optimum-thickness IZO TCL would make possible the fabrication of VM-LEDs with even larger area, higher power and better efficiency.

碩士
國立交通大學
應用化學系碩博士班
101
A new process of HTLs made by poly(triphenylamine-carbazole-uracil) (PTC-U) has been successfully constructed. In this study, the new method for solution process of PTC-U increase the solvent resistance of PTC-U and make the trilayer device to be 1.8 times higher than the commercial product PEDOT:PSS-based devices. Most of all, we still prove that physically cross-linked structure is important for HITM. In addition, we successfully synthesized a thermal-cross-linked HITM, poly(fluoren-carbazol-benzoxazine) (PFC-Bz) which has good thermal, electronic property. Moreover, PFC-Bz can undergo thermal-cross-liking at low temperature to enhance the resistance of solvent and not to destroy others structure.

The global lighting source energy consumption accounts for about 22% of the total electricity generated. New high-efficiency solid-state light sources are needed to reduce the ever increasing demand for energy. Single-phased emitter-based composed of transparent conducting oxides (TCOs) nanocrystals and fluorescent dyes can potentially revolutionize the typical composition of phosphors, the processing technology founded on the binding of dye acceptors on the surface of nanocrystals, and the configurations of the light-emitting diodes (LEDs) and electroluminescence devices. The hybrid white-light-emitting nanomaterial is based on the expanded spectral range of the donor-acceptor pair (DAP) emission originated from the γ-gallium oxide nanocrystals via Förster resonance energy transfer (FRET) to the surface-anchored fluorescent dyes. The emission of the nanocrystals and the sensitized emission of the chromophore act in sync as an internal relaxation upon the excitation of the γ–gallium oxide nanocrystals. It extends the lifetime of the secondary fluorescent dye chromophore and the internal relaxation within this hybrid complex act as a sign for a quasi single chromophore. The model system of white-light-emitting nanostructure system developed based on this technology is the γ–gallium oxide nanocrystals-Rhodamine B lactone (RBL) hybrid complex. The sufficient energy transfer efficiency of 31.51% within this system allowed for the generation of white-light emission with the CIE coordinates of (0.3328, 0.3380) at 5483 K. The relative electronic energy differences of the individual components within the hybrid systems based on theoretical computation suggested that the luminance of the nanocomposite comprised of RBL is dominantly mediated by FRET. The production of white-light-emitting diode (WLED) based on this technology have been demonstrated by solution deposition of the hybrid nanomaterials to the commercially available ultraviolet (UV) LED due to the versatility and chemical compatibility of the developed phosphors.

Membrane filtration has revolutionised water treatment, enabling safer provision of drinking water due to its high efficiency to block human infectious pathogens commonly present in raw water sources. Accumulation of substances on membrane surfaces and pores during operation, referred to as fouling, is considered one of the biggest barriers to wider adoption of membrane technology in water treatment. Maintaining continuous low-pressure filtration requires significant amounts of chemicals to clean off the accumulated fouling substances. Chemical use comes with economic and environmental costs associated with acquisition, transportation, storage, usage and disposal of chemicals, especially in disadvantaged and remote communities. By conservative estimates, supply of household water to a remote community of 100 people using a membrane system would require continuous supply of at least 10 L of polyaluminium chloride coagulant and 4 L of sodium hypochlorite (in concentrated form) every month. The main aim of this thesis is to demonstrate a sustainable, innovative, low cost membrane solution harnessing conveniently available solar energy to offset these chemical demands. Coating membrane substrates with semiconductor photocatalysts such as titanium dioxide (TiO2) is an effective method for mitigating fouling in membranes through induced superhydrophilicity, enabling cleaning from the available water without chemicals. TiO2 also enables water contaminant degradation and pathogen inactivation through reactive oxygen species (ROS) facilitated advanced oxidation. Despite these well- known effects, a major challenge limiting practical adoption comes from light absorption and scattering by the turbid contaminants in the feed stream before reaching the TiO2. This thesis proposed a novel solution to this challenge by transmitting light to the TiO2 through cheap porous borosilicate glass substrates with between 10% and 80 % transmission in the 340-400 nm wavelength range relevant to activating commercial Degussa P25 TiO2 photocatalyst. The concept novel membrane was produced using commercial glass substrates modified by simply dip- coating and heat sintering Degussa P25. The formed asymmetric membrane’s mean pore size was measured at 0.5 μm, which classifies the membrane as a microfiltration (MF) membrane, which are utilised in the industry as a barrier to water-borne pathogens such as protozoa and bacteria, and partially to viruses. To demonstrate the membrane’s photocatalytic ability, photocatalytic reactions stimulated by a UV lamp (365 nm peak) facing the glass substrate side in an ex-situ setup led to a 52% degradation of methyl orange in aqueous solution, being only slightly lower than the 58% degradation when the TiO2 active layer faced the UV light source. The membrane was then operated in-situ using a custom module with a quartz window and UV LED installed on the permeate side, enabling simultaneous microfiltration of model fouling solutions. Results showed significant reductions in trans-membrane pressure (TMP) rise rates directly linked to UV light application. Specifically, UV light was responsible for up to 3.0-fold reduction in total filtration resistance and up to 4.2-fold reduction in irreversible fouling indices. Testing continued on simulated indirect solar light with a real non-potable water. The membrane itself showed up to 94% turbidity removal and up to 80% total organic carbon (TOC) rejection. The sunlight was directly responsible for an 8-fold reduction in the irreversible fouling index. The significant practical findings were followed by an investigation to confirm the fundamental basis for improvement. Analysis by scanning electron microscopy (SEM) coupled with fouling modelling showed the beneficial photocatalytic fouling reduction effects during microfiltration stemmed from reduced intrusion of organic fouling material inside the TiO2 membrane pores, as well as reduced cake layer resistance. Analysis of results and photocatalysis mechanisms from literature led to the conclusion this was due to both superhydrophilicity minimising organic attractions to the surface and photocatalytic oxidation of organics approaching the surface. The potential for advanced oxidation to participate in reacting with organic matter surfaces attracted to the membrane was confirmed from a measurable increase in the presence of hydroxyl radicals using para-chlorobenzoic acid (pCBA) probe experiments. The practical benefits for industry towards chemical consumption and energy reduction were also measured. For example, a 4.5-fold extension to the time needed for a clean-in-place (CIP) was realised when the membrane was operated in photocatalytic mode. A 50% reduction in filtration pump electricity demand was also calculated, which translates to a reduction in height of the feed water for a flux of 300 L/m2/h from 8.6 m to 3.7 m over a 5 hour run. Future work suggested includes using recycled glass to improve affordability and minimise glass manufacture environmental impact, as well as experimentally establishing the relationship hydroxyl radical concentration and TOC reduction. Optimisation of the glass material for enhancing light transmission efficiency and development of porous glass monoliths like current commercial ceramic membranes for full-scale use, as well as optimisation to increase contaminant degradation are also suggested.

Les matériaux conjugués ont fait l’objet de beaucoup de recherches durant les dernières années. Les nouveaux matériaux présentent des propriétés intéressantes que ce soit au niveau optique, électrique, mécanique ou même les trois en même temps. La synthèse reste la difficulté principale dans la fabrication de dispositifs électroniques. Les méthodes utilisées pour y parvenir sont l’électropolymérisation, le couplage de Suzuki ou de Wittig. Ces techniques comportent encore de nombreuses contraintes et s’avèrent difficilement réalisables à grande échelle. Les thiophènes, les pyrroles et les furanes ont démontré une bonne conductibilité et une bande de conduction basse due à une conjugaison accrue. L’objectif ici est de synthétiser des oligomères principalement composés de thiophènes dans le but d’en caractériser les propriétés spectroscopiques, électrochimiques et de conduction. La synthèse est souvent l’étape délicate de la fabrication de matériaux conjugués. Nous présentons ici une méthode de synthèse simple par modules avec des unités hétérocycliques. Les modules complémentaires sont attachés par condensation entre un aldéhyde et une amine menant à la formation d’un lien robuste, l’azomethine. Les résultats des propriétés photophysiques et électrochimiques de ces matériaux conjugués seront présentés. En ayant recours à différents groupes électrodonneurs et électroaccepteurs, en variant le degré de conjugaison ou en utilisant différents hétérocycles, les propriétés spectroscopiques, électrochimiques et de bande de conduction peuvent être adaptées à volonté, ce qui en fait des matériaux aux propriétés modelables. Ces nouvelles molécules seront analysées pour en déceler les propriétés recherchées dans la fabrication d’OLED. Nous explorerons les domaines de l’oxidation electrochimique réversible et de la polymérisation menant à la fabrication de quelques prototypes simples.
Conjugated materials have received much attention recently as they show promise for industrial applications. These materials are interesting because of the many new possibilities for devices combining unique optical, electrical and mechanical properties. The synthesis is the major difficulty in the fabrication of electronic devices. Usual methods to do so are electropolymerisation, Suzuki or Wittig coupling. Those techniques are full of constraints and are difficult to scale-up. Thiophenes, pyrroles and furans demonstrated good conductibility and low band-gap due to increased conjugation. Our main goal is to synthesize oligomers made principally of thiophene to characterize their spectroscopic, electrochemical and conduction properties. Synthesis is the most important step in the making of conjugated material. A synthetically simple and modular route to novel conjugated material consisting of heterocyclic units is presented. These complementary modules are linked by condensing aldehydes and amines leading to robust azomethine bonds. The resulting photophysical and electrochemical properties of these conjugated materials will be presented. Through the use of different electron donor and acceptor groups, degree of conjugation or by using different heterocycles, the spectroscopic, electrochemical and band-gap properties can be tailored leading to materials with tunable properties. Those new molecules will be analysed to detect properties suitable for OLED fabrication. This presentation will also address the electrochemical reversible oxidation and polymerization of these compounds leading to the making of simple devices.

碩士
國立臺灣師範大學
物理學系
105
Graphene is a two-dimensional material in which the carbon atoms are arranged in a hexagonal lattice. It has many advantages such as low resistivity, high carrier mobility, good thermal properties and mechanical properties, among which the high transmittance in the UV region is more promising for use in deep ultraviolet light emitting diodes as the material of the transparent conductive electrode. However, the high contact resistivity of graphene and the top material of deep ultraviolet light-emitting diode is the largest obstacle to the application. In this experiment, we propose a method to reduce the Schottky barrier by using nickel oxide which is made by atomic layer chemical vapor deposition as a buffer layer to improve the poor contact. In the graphene process, this experiment usess the plasma-enhanced chemical vapor deposition to directly grow graphene on the substrate. The system improves the high-temperature process and transfer process of conventional low-pressure chemical vapor deposition, so that makes large area production of graphene be feasible. Finally, we directly grow about five layer graphene on the top of the the p-AlGaN layer. With the use of NiO as the buffer layer, we get the contact resistance is equal to (4.29 ± 0.46) × 10-1Ω-cm2 and have transmittance about 50% at 280 nm. This material has the potential to replace indium tin oxide (ITO) as a transparent conductive electrode.

碩士
國立海洋大學
光電科學研究所
88
In this study, we use Ni/Au and NiCr alloy, the highly conductive and transparent Ni/Au（3nm/7nm） and NiCr（10nm） films were deposited by thermal evaporator. The optimum Ni / Au contact on P-GaN film ohmic contact, and light transparence have light transmittance is around 88.6% at 450 nm. The composition of NiCr targets were 80% Nickel and 20% Chromium. The optimum NiCr alloy contact on P-GaN film ohmic contact, the contact specific resistance ρc is 4.83×10-2 ohm-cm2 by circular transmission line model (CTLM), and the light transmittal was measured to be around 92.6% at 450nm. The device have been fabricated for Ni / Au contact on p-electrode of GaN LED, it has output power of bare chip is about 1.2mW at 20mA injection current and the forward voltage is about 4.2V for Ni / Au and external quantum efficiency is about 2.2% at 450 nm. The NiCr alloy suggested fabricate electrodes and transparent conductive layers (TCL) with application to gallium nitride blue light-emitting diodes. KEYWORDS: transparent conductive layers（TCL）, gallium nitride, circular transmission line model (CTLM)