Browsing by Subject "White light"
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Item Open Access Novel hybrid light emitting diodes with multiple assemblies of nanocrystals to generate and tune white light(2007) Nizamoğlu, SedatToday approximately one third of the world population (about two billion people) in under-developed countries has no access to electricity and relies on unhealthy, costly and low-quality fuel-based lighting for home illumination. In the rest of the world, lighting consumes a large portion (20%) of the total electricity production, which significantly contributes to global warming problem. Also given limited resources, such large energy consumption needs to be reduced for sustainable economic growth. Solid state lighting provides remedy to these problems for the entire globe. Therefore, the advancement of white light emitting diodes (WLEDs) becomes a key point for development of human civilization. To this end, the strong demand for the development of high quality WLEDs around the globe motivates our research work on the investigation of white light generation with high color rendering index. In this thesis, we develop and demonstrate nanocrystal hybridized light emitting diodes with high color rendering index. By the hybridization of multiple layer-by-layer assemblies of CdSe/ZnS core-shell nanocrystals on blue and near ultraviolet (n-UV) InGaN/GaN light emitting diodes, we show white light generation with highly tunable optical properties such as tristimulus color coordinates, correlated color temperature, and color rendering index. Additionally, by using dual hybridization of nanocrystals in combination with conjugated polymers, we obtain white light sources with high color rendering indices exceeding the requirements of the future solid state lighting applications. In this thesis, we present design, growth, fabrication, experimental characterization and theoretical analysis of these hybrid white LEDs.Item Open Access Semiconductor nanocrystals as rare-earth alternatives(Macmillan Publishers, 2011) Erdem, T.; Demir, Hilmi VolkanItem Unknown Technique for reconstructing a surface shape for measuring coordinates(OSA, 2006) Sainov, V. K.; Kharizanova, Z. I.; Stoikova, E. V.; Özaktaş, Haldun M.; Onural, LeventThis paper describes a method of projecting interference fringes as one of the most accessible techniques for measuring the coordinates of objects and scenes that can be used when solving inverse problems in dynamic holographic display, where the coordinates need to be measured in order to compute diffraction structures when reconstructing three-dimensional images. A comparative analysis is presented of the experimental results obtained with successive projections of interference patterns with two different periods, using a Mach-Zehnder interferometer in coherent light and a micromirror projector with digital generation of fringes in white light. The use of the method is limited by the size of the objects and scenes. The possibilities of using more refined methods, including the holographic approach to phase reconstruction, are discussed. © 2006 Optical Society of America.Item Unknown Tunable white light generating nanocyrstal-hybridized LEDs(IEEE, 2007) Demir, Hilmi Volkan; Nizamoğlu, SedatWe hybridize CdSe/ZnS core-shell nanocrystals on InGaN/GaN near-UV/blue LEDs to generate light widely tunable across the visible spectral range and within the white region of the chromaticity diagram with adjustable tristimulus coordinates. We present the design, growth, fabrication, and characterization of these nanocrystalhybridized LEDs. © 2007 Optical Society of America.Item Unknown Ultrafast on-site selective visual detection of TNT at sub-ppt level using fluorescent gold cluster incorporated single nanofiber(Royal Society of Chemistry, 2015) Senthamizhan, A.; Celebioglu A.; Uyar, TamerIn this communication, a fluorescent gold cluster incorporated electrospun nanofibrous membrane and single nanofiber for selective and sensitive detection of TNT at sub-ppt level are demonstrated.Item Unknown White light generating nonradiative energy transfer directly from epitaxial quantum wells to colloidal nanocrystal quantum dots(Optical Society of America, 2009) Nizamoğlu, Sedat; Sarı, Emre; Baek J.-H.; Lee I.-H.; Demir, Hilmi VolkanWe present white light generating nonradiative Förster resonance energy transfer at a rate of (2ns)-1 directly from epitaxial InGaN/GaN quantum wells to CdSe/ZnS heteronanocrystals in their close proximity at chromaticity-coordinates (x,y)=(0.42,0.39) and correlated-color-temperature CCT=3135K. ©2009 Optical Society of America.Item Unknown White light generating semiconductor nanocrystal luminophors with high photometric quality(IEEE, 2008-12) Demir, Hilmi VolkanWe proposed and demonstrated warm white light generating combinations of semiconductor nanocrystal quantum dot emitters with high photometric quality including high color rendering index (~80) on LED platforms to meet requirements of future lighting. Additionally, we developed and demonstrated plasmon coupling of these nanocrystal luminophors with metal nanoparticles to control and enhance their spontaneous emission in the solid state film.Item Open Access White light generation with CdSe/ZnS core-shell nanocrystals and InGaN/GaN light emitting diodes(IEEE, 2006) Nizamoğlu, Sedat; Özel, Sedat; Sarı, Emre; Demir, Hilmi VolkanWe present hybrid white light sources that integrate CdSe/ZnS core-shell nanocrystals on blue InGaN/GaN light emitting diodes (LED). We report on the demonstrations of white light generation using yellow nanocrystals (λPL=580 nm) hybridized on a blue LED (λEL= 440 nm) with tristimulus coordinates of x=0.37 and y=0.25, correlated color temperature of Tc=2692 K, and color rendering index of R a=14.6; cyan and red nanocrystals (λPL=500 nm and 620 nm) on a blue LED (λEL=440 nm) with x=0.37, y=0.28, T c=3246 K, and Ra=19.6; and green, yellow, and red nanocrystals (λPL=540 nm, 580 nm, and 620 nm) on a blue LED (λEL=452 nm) with x=0.30, y=0.28, Tc =7521 K, and Ra=40.9. © 2006 IEEE.