Browsing by Subject "CdSe/ZnS"
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Item Open Access Electric field effects on optical properties of semiconductor nanorods(2009-05) Gurinovich L. I.; Lutich, A. A.; Stupak, A. P.; Prislopskii, S. Va.; Artemyev, M. V.; Rusakov, E. K.; Demir, Hilmi VolkanWe studied electric field effects on optical properties of CdSe/ZnS nanorods integrated in thin films sandwiched between transparent electrodes. It was demonstrated that P-polarized component of the photoluminescence of CdSelZnS nanorods is quenched stronger by external electric field than the S-polarized component. Quantum dots are more sensitive to external electric field than the nanorods. A mechanism of external electric field influence on the luminescence spectrum of semiconductor nanorods is discussed.Item Open Access Förster resonance energy transfer enhanced color-conversion using colloidal semiconductor quantum dots for solid state lighting(American Institute of Physics, 2009-10-15) Nizamoglu, S.; Demir, Hilmi VolkanIn this paper, we present Förster resonance energy transfer (FRET)-enhanced color-conversion using colloidal semiconductor quantum dot nanocrystals (NCs) to make reddish-orange light-emitting diodes for use in ultraefficient solid state lighting. To achieve FRET enhancement at 614 nm, we use an energy gradient hybrid structure made of cyan- and orange-emitting CdSe/ZnS NCs (λPL =492 and 588 nm in solution, respectively). This enables recycling of trapped excitons using FRET and achieves a relative quantum efficiency enhancement of 15.1% in reddish-orange full color-conversion for the integrated hybrid cyan-orange NC layer with respect to the case of full color-conversion using only orange NCs without FRET.Item Open Access Highly efficient nonradiative energy transfer using charged CdSe/ZnS nanocrystals for light-harvesting in solution(American Institute of Physics, 2009-07-20) Mutlugün, E.; Nizamoğlu, S.; Demir, Hilmi VolkanWe propose and demonstrate highly efficient nonradiative Förster resonance energy transfer (FRET) facilitated by the use of positively charged CdSe/ZnS core-shell nanocrystals (NCs) for light-harvesting in solution. With rhodamine B dye molecules used as the acceptors, our time-resolved photoluminescence measurements show substantial lifetime modifications of these amine-functionalized NC donors from 18.16 to 1.88 ns with FRET efficiencies >90% in solution. These strong modifications allow for light-harvesting beyond the absorption spectral range of the acceptor dye molecules.Item Open Access Nanocrystal hybridized white light sources integrated on near UV leds(World Scientific Publishing, 2007) Nizamoğlu, Sedat; Demir, Hilmi VolkanWe report on CdSe/ZnS core-shell nanocrystal (NC) based white light sources integrated on near-UV InGaN/GaN light emitting diodes (LEDs). We present the design, epitaxial growth, fabrication, integration and characterization of such hybrid NC-LEDs that incorporate the dual combinations of cyan and yellow nanocrystals (λPL=500-580 nm) and the trio combinations of cyan, green, and red nanocrystals (λPL=500-540-620 nm).Item Open Access Nanocrystal LEDs with enhanced external quantum efficiency enabled by the use of phosphorescent molecules(IEEE, 2013) Mutlugün, Evren; Abiyasa, A.P.; Güzeltürk, Burak; Gao, Y.; Leck, K.S.; Sun X.W.; Demir, Hilmi VolkanWe report efficiency enhancement in quantum dot (QD) based LEDs with the aid of excitonic energy transfer from co-doped TCTA:Ir(ppy)3 layer to CdSe/ZnS QDs while providing spectrally pure emission. © 2013 IEEE.Item Open Access 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 Open Access 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 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.