Les diodes organiques électroluminescentes (OLEDs) représentent une évolution de la technologie des diodes électroluminescentes (LED) dans lesquelles l'émission de couleur provient de molécules organiques. Ce travail porte sur la synthèse et l'étude de nouvelles molécules dans le but de leur utilisation (i) comme couche active dans les OLED fluorescentes ou (ii) comme matériau hôte dans les OLEDs phosphorescentes (PhOLEDs). Tout d'abord, une introduction à ce domaine important de l'électronique organique est présentée et suivie de la synthèse de nouveaux semi-conducteurs organiques dérivés d'oligophénylènes d'architecture 3π-2spiro ou 2π-1spiro. L'analyse détaillée de leurs propriétés physico-chimiques est ensuite présentée. Les performances des OLEDs et/ou PhOLEDs bleues utilisant ces nouvelles matrices sont alors décrites et montrent l'intérêt des designs choisis pour les molécules. / Organic light emitting diodes (OLEDs) represent an evolution of the light emitting diode (LED) technology in which light is emitted from an organic molecule. This work is focused on the synthesis and the study of new molecules, which will be used (i) as emissive layer in fluorescent OLEDs, or (ii) as host material in phosphorescent OLED (PhOLED). First of all an introduction of the important field of organic electronics is presented, followed by the presentation of the synthesis of new organic semi-conductors (3π-2spiro or 2π-1spiro hydrocarbons). A detailed analysis of their properties was performed and after incorporation in the devices, the performances of blue OLEDs and PhOLEDs are compared. The performances recorded attests that this molecular design is of great interest.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22449号 / 工博第4710号 / 新制||工||1736(附属図書館) / 京都大学大学院工学研究科電子工学専攻 / (主査)教授 川上 養一, 教授 野田 進, 教授 山田 啓文 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

In the last decades, investigations of organic light-emitting diodes (OLEDs) have tackled several key challenges of this lighting technology and have brought the electron to photon conversion efficiency close to unity. However, currently only 20% to 30% of the photons can typically be extracted from OLED structures, as total internal reflection traps the major amount of the generated light inside the devices. This work focuses on the optimization of the optical properties of top-emitting OLEDs, in which the emission is directed away from the substrate. In this case, opaque materials, e.g. a metal foil or a display backplane can be used as substrate as well. Even though top-emitting OLEDs are often preferred for applications such as displays, two main challenges remain: the application of light extraction structures and the deposition of highly transparent materials as top electrode, without harming the organic layers below. Both issues are addressed in this work. First, top-emitting OLEDs are deposited on top of periodically corrugated light outcoupling structures, in order to extract internally trapped light modes by Bragg scattering and to investigate the basic scattering mechanisms in these devices. It is shown for the first time that the electrical performance is maintained in corrugated top-emitting OLEDs deposited on top of light extraction structures. Furthermore, as no adverse effects to the internal quantum efficiency have been observed, the additional emission from previously trapped light modes directly increases the device efficiency. It has been proven that the spectral emission of corrugated OLEDs is determined by the interference of all light modes inside the air light-cone, including the observation of destructive interference and anti-crossing phenomena. The formation of a coherently coupled mode pair of the initial radiative cavity mode and a Bragg scattered mode has been first observed, when grating structures with an aspect ratio > 0.2 are applied. There, the radiative cavity mode partially vanishes. The observation and analysis of such new emission phenomena in corrugated top-emitting OLEDs has been essential in obtaining a detailed insight on fundamental scattering processes as well as for the optimization and control of the spectral emission by light extraction structures. Second, the adverse impact of using only moderately transparent silver electrodes in white top-emitting OLEDs has been compensated improving the metal film morphology, as the organic materials often prevent a replacement by state-of-the-art electrodes, like Indium-tin-oxide (ITO). A high surface energy Au wetting layer, also in combination with MoO3, deposited underneath the Ag leads to smooth, homogeneous, and closed films. This allows to decrease the silver thickness from the state-of-the-art 15 nm to 3 nm, which has the advantage of increasing the transmittance significantly while maintaining a high conductivity. Thereby, a transmittance comparable to the ITO benchmark has been reached in the wavelength regime of the emitters. White top-emitting OLEDs using the wetting layer electrodes outperform state-of-the art top-emitting devices with neat Ag top electrodes, by improving the angular colorstability, the color rendering, and the device efficiency, further reaching sightly improved characteristics compared to references with ITO bottom electrode. The enormous potential of wetting layer metal electrodes in improving the performance of OLEDs has been further validated in inverted top-emitting devices, which are preferred for display applications, as well as transparent OLEDs, in which the brittle ITO electrode is replaced by a wetting layer electrode. Combining both concepts, wetting layer electrodes and light extraction structures, allows for the optimization of the grating-OLED system. The impact of destructive mode interference has been reduced and thus the efficiency increased by a decrease of the top electrode thickness, which would have not been achieved without a wetting layer. The optimization of corrugated white top-emitting OLEDs with a top electrode of only 2 nm gold and 7 nm silver on top of a grating with depth of 150 nm and period of 0.8 µm have yielded a reliable device performance and increased efficiency by a factor of 1.85 compared to a planar reference (5.0% to 9.1% EQE at 1000 cd/m2). This enhancement is comparable to common light extraction structures, such as half-sphere lenses or microlens foils, which are typically restricted to bottom-emitting devices. Overall, the deposition of top-emitting OLEDs on top of light extraction structures finally allow for an efficient extraction of internally trapped light modes from these devices, while maintaining a high device yield. Finally, the investigations have resulted in a significant efficiency improvement of top-emitting OLEDs and the compensation of drawbacks (optimization of the white light emission and the extraction of internal light modes) in comparison to the bottom-emitting devices. The investigated concepts are beneficial for OLEDs in general, since the replacement of the brittle ITO electrodes and the fabrication of roll-to-roll processing compatible light extraction structures are also desirable for bottom-emitting, or transparent OLEDs.

Indiana University-Purdue University Indianapolis (IUPUI) / The general aim of this study was to investigate the influence of the localized irradiance beam profiles from multiple light-emitting-diode (LED) light-curing units (LCUs) on the polymerization pattern within a resin-matrix composite (RMC). Irradiance beam profiles were generated from one quartz-tungsten-halogen and various single and multiple emission peak LED LCUs using a camera-based beam profiler system combined with LCU power measurements obtained using an integrating sphere/spectrometer assembly. The influence of distance on irradiance, radiant exposure (RE) and degree of conversion (DC) on the top and bottom surfaces of a RMC increment, using various LCUs, at two clinically relevant distances was investigated. Molar absorptivity of the photoinitiators present in the nano-hybrid RMC (Tetric EvoCeram bleaching shade-XL) assessed was using UV-spectrophotometry. The correlation among irradiance, RE and DC was explored. A mapping approach was used to investigate DC, microhardness and cross-link density (CLD) within 5×5×2 mm specimens at various depths; top, 0.5, 0.7, 0.9, 1.1, 1.3,1.5 mm and bottom. The localized irradiance correlation with its corresponding DC, microhardness and CLD was explored, and localized DC correlation with microhardness was assessed. The DC was measured using micro-Raman spectroscopy, and CLD was assessed by an ethanol-softening method (%KHN reduction) using an automated microhardness tester. Molar absorptivity of diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide was 20-fold higher than camphorquinone. Non-uniform LCU beam profiles caused localized polymerization discrepancies that were significant at specific depths and points within the specimens with respect to DC, microhardness and CLD, which did not follow a specific pattern regardless of the LCU or curing distance assessed. A moderate correlation was displayed among irradiance, RE and DC. The localized irradiance from the LCUs was weakly correlated with the corresponding DC, microhardness and CLD on the top surface of a RMC at both curing distances. The localized microhardness was moderately correlated with DC. In conclusion, polymerization within the RMC investigated was non-uniform and did not reflect the LCU irradiance pattern at the area assessed. Also, a mapping approach within the specimens provided a detailed polymerization pattern assessment occurring within a RMC increment. Therefore, the LCUs explored may potentially increase the risk of RMC fracture.

In this thesis we examine the feasibility of developing a white light source capable of producing colors between 2500 and 7500 Kelvin on the black-body radiator spectrum by simply adjusting amperage to a blue and ultraviolet (UV) light emitting diode (LED). The purpose of a lighting source of this nature is to better replicate daylight inside a building at a given time of day. This study analyzes the proposed light source using a 385 nm UV LED, a 457 nm blue LED, a 479 nm blue LED, a 562 nm peak cerium doped yttrium aluminum garnet (YAG:Ce) phosphor, and a 647 nm peak selenium doped zinc sulfide (ZnS:Se) phosphor. Our approach to this study initially examined optical performance of yellow-emitting phosphor (YAG:Ce) positioned at specific distances above a blue LED using polydimethylsiloxane (PDMS) as a substrate. An understanding of how phosphor concentration within the PDMS, the thickness of the PDMS, and how substrate distance from the LED die affected light intensity and color values (determined quantitatively by utilizing the 1931 CIE 2° Standard Observer) enabled equations to be developed for various lens designs to efficiently produce white light using a 457 nm peak wavelength LED. The combination of two luminescent sources (457 nm LED and YAG:Ce) provided a linear trend on the 1931 CIE diagram which required a red illumination source to obtain Kelvin values from 2500 to 7500. Red-emitting phosphor (ZnS:Se), selected to compliment the system, was dispersed with YAG:Ce throughout PDMS where they were stimulated with a blue LED thereby enabling all desired Kelvin values with differing concentration lenses. Stimulating ZnS:Se with the addition of a UV LED did not provide the ability to change the color value of the set up to the degree required. Many other factors resulted in the decision to remove the UV LED contribution from the multi-Kelvin light source design. The final design incorporated a combination of ZnS:Se and YAG:Ce stimulated with a blue LED to obtain a 2500 Kelvin value. A separate blue LED provides the means to obtain 7500 Kelvin light and the other color values in between, with a linear approximation, by adjusting the amperages of both LEDs. In addition to investigating the feasibility of obtaining the Kelvin values from 2500 to 7500, this thesis also examined the problem of ZnS:Se’s inability to cure in PDMS and a method to create a lens shape to provide equal color values at all points above a phosphor converted LED source. ZnS:Se was found to be curable in PDMS if first coated with a low viscosity silicon oil prior to dispersion within PDMS. The lens configuration consists of phosphors equally distributed in PDMS and cured in the shape of a Gaussian distribution unique to multiple factors in LED-based white light design.

The present thesis explores the possibilities of reducing electrical energy consumption in a greenhouse environment through the construction a demonstrator system. The demonstrator system is imagined to be used in a vertical farming setup and is fully automated. The system achieves two main actions. It maintains the artificial light source at a fixed distance above the canopy of the grown crops, and it measures the change in natural light exposure and regulates the artificial light to maintain light conditions while utilizing sunlight. These prove to be good methods for reducing the amount of electrical energy consumed by such a system. / Examensarbetet utforskar möjligheterna att minska elförbrukningen i en växthusmiljö genom att bygga ett demonstrationssystem. Demonstrationssystemet är tänkt att användas i en vertikal jordbruksuppsättning och är helautomatiserat. Systemet uppnår två huvudsakliga moment. Det håller den artificiella ljuskällan på ett fast avstånd ovanför de odlade grödorna, och det mäter förändringen i naturlig ljusexponering och reglerar det artificiella ljuset för att bibehålla ljusförhållandena samtidigt som solljuset utnyttjas. Dessa visar sig vara bra metoder för att minska mängden elektrisk energi som förbrukas av ett sådant system.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第24903号 / 工博第5183号 / 新制||工||1989(附属図書館) / 京都大学大学院工学研究科分子工学専攻 / (主査)教授 梶 弘典, 教授 関 修平, 教授 寺村 謙太郎 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

No description available.

Recently, as a promising lighting source, light-emitting diodes (LEDs) have become more and more attractive and have great opportunity to replace traditional lighting sources - incandescent, fluorescent and HID because of the advantages such as high luminous efficacy, long lifetime, quick on/off time, wide color gamut, eco-friendly etc. Based on the research from U.S. Department of Energy, over 30% of total electric consumption in U.S. each year is for lighting, 75% of which are for indoor lighting (including both residential and commercial buildings). In the indoor LED lighting application, to provide multiple current source outputs for multiple LED strings, traditional solutions usually adopt a two-stage structure, which is complicated and cost-ineffective. How to design a simple, low-cost and efficient LED driver with multiple current source outputs is in great demand and really challenging. In this thesis, a single-stage multi-channel constant current (MC3) LED driver structure has been proposed. Multiple transformer structure is utilized to provide multiple current source outputs. The current control scheme is also simple - only one LED string current is sensed and controlled; other strings' currents are cross regulated. Firstly, a PWM half bridge topology is chosen to implement the proposed single-stage MC3 LED driver concept. In order to analyze the current cross regulation, a general model is derived. The circuit has been simulated under various LED load conditions to verify its good current sharing capability. In order to further improve efficiency, simplify the driver's complexity and reduce cost, a LLC resonant topology is also investigated. LLC current gain characteristic has been derived by considering LED's i-v character and a design procedure is developed. A 100 kHz, 200 W, 4-string MC3 LLC LED driver is designed and tested. The experimental results show that the driver can maintain constant current output within the whole input and output variations, achieve good efficiency and realize current sharing under both balanced and unbalanced LED conditions. The dimming function can also be realized through frequency modulation method and burst mode control method. As a conclusion, a single-stage MC3 LED driver concept is proposed and implemented with two topologies. The proposed idea provides a simple, low-cost and efficient solution for indoor LED lighting application with multiple LED string configuration. It also has good current sharing capability and robustness to LED forward voltage variations or short failures. / Master of Science

近來LED在日常生活中的照明應用如火如荼，幾乎到處可見到它的蹤跡。由於不但輕薄短小，更具節能環保特性，因此發展潛力無限，已被視為取代傳統照明的明日之星。 從較小功率的訊號指示燈運用開始，隨著開發與製造技術的提升，逐漸擴展應用到液晶電視背光板，而後家用照明、商業照明，進而車用照明等更高發光效率、更大功率、更廣色域的運用領域，儼然已成照明主流。 然而，在車用領域，雖然照明的需求非常多，諸如方向燈、煞車燈、標示燈、儀表燈、閱讀燈、晝行燈、霧燈、頭燈等，都是LED潛在的應用市場，但各家車廠在追求時尚與科技感的同時，亦無法忽略安全與耐久性的考量。尤其是在同時具有高度車廠品牌識別功能的頭、尾燈及晝行燈照明方面。 因此，從LED照明供應商至車廠，無不花費巨資、卯足全力，競相研發、推廣，如何及時將LED新產品引進到車上，以能更快更多地擄獲潛在車主歡心，取得整體商品價值與銷售市占提升的相輔相成效果。 本研究之目的，正是針對引進新產品LED照明的國產小客車，以產業龍頭公司個案為例，探討如何結合產品、訂價、通路、促銷，以及人員、流程、有形展示等7Ps行銷組合(marketing mix)策略，達到促進LED新產品在國產小客車市場的擴大應用。 本研究除了將針對企業市場競爭策略，及行銷策略組合的理論基礎加以探討外，也將同時對LED小客車的產業環境，以及個案公司有關LED國產小客車市場競爭策略、行銷策略與業務規劃等一併進行了解與分析，冀望藉此進一步推移出未來國產小客車用照明市場中，LED新產品引進及銷售的提升與發展方向。