Browsing by Subject "Light-harvesting"

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    Förster-type nonradiative energy transfer directed from colloidal quantum dots to epitaxial quantum wells for light harvesting applications
    (Optical Society of America, 2011) Nizamoğlu, Sedat; Sarı, Emre; Baek J.-H.; Lee I.-H.; Demir, Hilmi Volkan
    We report on Frster-type nonradiative energy transfer directed from CdSe/ZnS core/shell quantum dots to InGaN/GaN quantum wells with 69.6% efficiency at 1.527 ns-1 rate at room temperature for potential light harvesting and solar cells applications. © 2011 OSA.
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    Förster-type resonance energy transfer (FRET): Applications
    (Springer Verlag, 2017) Demir, Hilmi Volkan; Hernández Martínez, Pedro Ludwig; Govorov, Alexander
    In this chapter, we present several applications of Förster-type nonradiative energy transfer (FRET) related phenomena. In particular, we review light generation and light harvesting applications as well as bio-applications. © 2017, The Author(s).
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    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 Volkan
    We 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.
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    Light harvesting with Ge quantum dots embedded in SiO2 or Si3N4
    (A I P Publishing LLC, 2014) Cosentino, S.; Ozen, E. S.; Raciti, R.; Mio, A. M.; Nicotra, G.; Simone, F.; Crupi, I.; Turan, R.; Terrasi, A.; Aydınlı, Atilla; Mirabella, S.
    Germanium quantum dots (QDs) embedded in SiO2or in Si3N4have been studied for light harvesting purposes. SiGeO or SiGeN thin films, produced by plasma enhanced chemical vapor deposition, have been annealed up to 850°C to induce Ge QD precipitation in Si based matrices. By varying the Ge content, the QD diameter can be tuned in the 3-9 nm range in the SiO2matrix, or in the 1-2 nm range in the Si3N4matrix, as measured by transmission electron microscopy. Thus, Si3N4matrix hosts Ge QDs at higher density and more closely spaced than SiO2matrix. Raman spectroscopy revealed a higher threshold for amorphous-to-crystalline transition for Ge QDs embedded in Si3N4matrix in comparison with those in the SiO2host. Light absorption by Ge QDs is shown to be more effective in Si3N4matrix, due to the optical bandgap (0.9-1.6 eV) being lower than in SiO2matrix (1.2-2.2 eV). Significant photoresponse with a large measured internal quantum efficiency has been observed for Ge QDs in Si3N4matrix when they are used as a sensitive layer in a photodetector device. These data will be presented and discussed, opening new routes for application of Ge QDs in light harvesting devices. © 2014 AIP Publishing LLC.
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    Photovoltaic nanopillar radial junction diode architecture enhanced by integrating semiconductor quantum dot nanocrystals as light harvesters
    (American Institute of Physics, 2010-09-03) Güzeltürk, B.; Mutlugün, E.; Wang, X.; Pey, K. L.; Demir, Hilmi Volkan
    We propose and demonstrate colloidal quantum dot hybridized, radial p-n junction based, nanopillar solar cells with photovoltaic performance enhanced by intimately integrating nanocrystals to serve as light harvesting agents around the light trapping pillars. By furnishing Si based nanopillar photovoltaic diodes with CdSe quantum dots, we experimentally showed up to sixfold enhancement in UV responsivity and ∼13% enhancement in overall solar conversion efficiency. The maximum responsivity enhancement achieved by incorporation of nanocrystals in the nanopillar architecture is found to be spectrally more than four times larger than the responsivity enhancement obtained using planar architecture of the same device.