The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
Hilmi Volkan Demir - One of the best experts on this subject based on the ideXlab platform.
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highly efficient Nonradiative Energy Transfer from colloidal semiconductor quantum dots to wells for sensitive noncontact temperature probing
Advanced Functional Materials, 2016Co-Authors: Burak Guzelturk, Murat Olutas, Yusuf Kelestemur, Hilmi Volkan Demir, Kivanc GungorAbstract:This study develops and shows highly efficient exciton-Transferring hybrid semiconductor nanocrystal films of mixed dimensionality comprising quasi 0D and 2D colloids. Through a systematic study of time-resolved and steady-state photoluminescence spectroscopy as a function of the donor-to-acceptor molar concentration ratio and temperature, a high-efficiency Nonradiative Energy Transfer (NRET) process from CdZnS/ZnS core/shell quantum dots (QDs) directed to atomically flat CdSe nanoplatelets (NPLs) in their solid-state thin films is uncovered. The exciton funneling in this system reaches Transfer efficiency levels as high as 90% at room temperature. In addition, this study finds that with decreasing temperature exciton Transfer efficiency is increased to a remarkable maximum level of ≈94%. The enhancement in the dipole–dipole coupling strength with decreasing temperature is well accounted by increasing photoluminescence quantum yield of the donor and growing spectral overlap between the donor and the acceptor. Furthermore, NRET efficiency exhibits a highly linear monotonic response with changing temperature. This makes the proposed QD–NPL composites appealing for noncontact sensitive temperature probing based on NRET efficiencies as a new metric. These findings indicate that combining colloidal nanocrystals of different dimensionality enables efficient means of temperature probing at an unprecedented sensitivity level at nanoscale through almost complete exciton Transfer.
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Nonradiative Energy Transfer in a layered metal dielectric nanostructure mediated by surface plasmons
Proceedings of SPIE, 2015Co-Authors: Sepideh Golmakaniyoon, Hilmi Volkan DemirAbstract:Nonradiative Energy Transfer (NRET) has been applied in various applications of Nanosensors, Raman scattering, color tuning, light harvesting and organic light emitting structures. Due to the small range of donor-acceptor separation distance that NRET is effective, the improvement in Energy Transfer (ET) efficiency for thicker structures seems necessary. The plasmons resonance Energy Transfer (PRET) has been successfully employed to improve the NRET efficiency. The conventional plasmonic configuration consists of donor-metal nanostructure-acceptor shows remarkable improvement of PRET efficiency from the excited donor dipole to the acceptor molecule in longer separation distance. We report the first successful cascaded plasmons coupling in planar structure of donor/acceptor thin film that significantly gives rise to enhancement of ET efficiency. Moreover, the theoretical analysis shows an enhancement in induced electric field due to stratified metal-dielectric configuration compared to simple metal thin film. We observed ET efficiency increases more than 100% by applying dielectric layer between two metal films in plasmonic structure.
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Nonradiative Energy Transfer in a layered metal-dielectric nanostructure mediated by surface plasmons
Proceedings of SPIE, 2015Co-Authors: Sepideh Golmakaniyoon, Hilmi Volkan DemirAbstract:ABSTRACT Nonradiative Energy Transfer (N RET) has been applied in various applicati ons of Nanosensors, Raman scattering, color tuning, light harvesting and organic light emitting structures. Due to the small range of donor-acceptor separation distance that NRET is effective, the improvement in Energy Transfer (ET) efficiency for thicker structures seems necessary. The plasmons resonance Energy Transfer (PRET) has been successfully employed to improve the NRET efficiency. The conventional pl asmonic configuration consists of donor-met al nanostructure-acceptor shows remarkable improvement of PRET efficiency from th e excited donor dipole to the acceptor mol ecule in longer separation distance. We report the first successful cascaded plasmons coupling in planar structure of donor/acceptor thin film that significantly gives rise to enhancement of ET efficiency. Moreover, the theoreti cal analysis shows an enhancement in induced electric field due to stratified metal-dielectric configuration compared to simple metal thin film. We observed ET efficiency increases more than 100% by applying dielectric layer between two metal films in plasmonic structure. KEYWORDS: Surface plasmons, plasmonic Energy tr ansfer, silver film, organic dyes.
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Nonradiative Energy Transfer in colloidal cdse nanoplatelet films
Nanoscale, 2015Co-Authors: Burak Guzelturk, Murat Olutas, Savas Delikanli, Yusuf Kelestemur, Onur Erdem, Hilmi Volkan DemirAbstract:Nonradiative Energy Transfer (NRET) has been extensively studied in colloidal nanocrystal (quantum dots) and nanorod (quantum wires) assemblies. In this work, we present the first account of spectroscopic evidence of NRET in solid thin films of CdSe based colloidal nanoplatelets (NPLs), also known as colloidal quantum wells. The NRET was investigated as a function of the concentration of two NPL populations with different vertical thicknesses via steady state and time resolved spectroscopy. NRET takes place from the NPLs with smaller vertical thickness (i.e., larger band gap) to the ones with a larger vertical thickness (i.e., smaller band gap) with efficiency up to ∼60%. Here, we reveal that the NRET efficiency is limited in these NPL solid film assemblies due to the self-stacking of NPLs within their own population causing an increased distance between the donor–acceptor pairs, which is significantly different to previously studied colloidal quantum dot based architectures for Nonradiative Energy Transfer.
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forster type Nonradiative Energy Transfer for assemblies of arrayed nanostructures confinement dimension vs stacking dimension
Journal of Physical Chemistry C, 2014Co-Authors: Pedro Ludwig Hernandezmartinez, Alexander O Govorov, Hilmi Volkan DemirAbstract:Forster-type Nonradiative Energy Transfer (NRET) provides us with the ability to Transfer excitation Energy between proximal nanostructures with high efficiency under certain conditions. Nevertheless, the well-known Forster theory was developed for the case of a single donor (e.g., a molecule, a dye) together with single acceptor. There is no complete understanding for the cases when the donors and the acceptors are assembled in nanostructure arrays, though there are special cases previously studied. Thus, a comprehensive theory that models Forster-type NRET for assembled nanostructure arrays is required. Here, we report a theoretical framework of generalized theory for the Forster-type NRET with mixed dimensionality in arrays. These include combinations of arrayed nanostructures made of nanoparticles (NPs) and nanowires (NWs) assemblies in one-dimension (1D), two-dimension (2D), and three-dimension (3D) completing the framework for the Transfer rates in all possible combinations of different confinement ...
Sedat Nizamoglu - One of the best experts on this subject based on the ideXlab platform.
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observation of selective plasmon exciton coupling in Nonradiative Energy Transfer donor selective versus acceptor selective plexcitons
Nano Letters, 2013Co-Authors: Tuncay Ozel, Sedat Nizamoglu, Onur Akin, Pedro Ludwig Hernandezmartinez, Evren Mutlugun, Ilkem Ozge Ozel, Qing Zhang, Qihua Xiong, Hilmi Volkan DemirAbstract:We report selectively plasmon-mediated Nonradiative Energy Transfer between quantum dot (QD) emitters interacting with each other via Fo resonance Energy Transfer (FRET) under controlled plasmon coupling either to only the donor QDs (i.e., donor-selective) or to only the acceptor QDs (i.e., acceptor-selective). Using layer-by-layer assembled colloidal QD nanocrystal solids with metal nanoparticles integrated at carefully designed spacing, we demonstrate the ability to enable/disable the coupled plasmon-exciton (plexciton) formation distinctly at the donor (exciton departing) site or at the acceptor (exciton feeding) site of our choice, while not hindering the donor exciton-acceptor exciton interaction but refraining from simultaneous coupling to both sites of the donor and the acceptor in the FRET process. In the case of donor-selective plexciton, we observed a substantial shortening in the donor QD lifetime from 1.33 to 0.29 ns as a result of plasmon-coupling to the donors and the FRET-assisted exciton Transfer from the donors to the acceptors, both of which shorten the donor lifetime. This consequently enhanced the acceptor emission by a factor of 1.93. On the other hand, in the complementary case of acceptor-selective plexciton we observed a 2.70-fold emission enhancement in the acceptor QDs, larger than the acceptor emission enhancement of the donor-selective plexciton, as a result of the combined effects of the acceptor plasmon coupling and the FRET-assisted exciton feeding. Here we present the comparative results of theoretical modeling of the donor- and acceptor- selective plexcitons of Nonradiative Energy Transfer developed here for the first time, which are in excellent agreement with the systematic experimental characterization. Such an ability to modify and control Energy Transfer through mastering plexcitons is of fundamental importance, opening up new applications for quantum dot embedded plexciton devices along with the development of new techniques in FRET-based fluorescence microscopy.
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Strong Nonradiative Energy Transfer from the nanopillars of quantum wells to quantum dots: Efficient excitonic color conversion for light emitting diodes
2012 Conference on Lasers and Electro-Optics (CLEO), 2012Co-Authors: Burak Guzelturk, Sedat Nizamoglu, Dae-woo Jeon, Hilmi Volkan DemirAbstract:Efficient Nonradiative Energy Transfer is observed from nanopillars of InGaN/GaN quantum wells to colloidal CdSe/ZnS quantum dots up to 83% efficiency. Nanostructured architecture is shown to promote excitonic color conversion for LED applications.
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Förster-type Nonradiative Energy Transfer directed from colloidal quantum dots to epitaxial quantum wells for light harvesting applications
CLEO: 2011 - Laser Science to Photonic Applications, 2011Co-Authors: Sedat Nizamoglu, Emre Sari, Jong-hyeob Baek, Hilmi Volkan DemirAbstract:We report on Forster-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.
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efficient Nonradiative Energy Transfer from ingan gan nanopillars to cdse zns core shell nanocrystals
Applied Physics Letters, 2011Co-Authors: Sedat Nizamoglu, Burak Guzelturk, Dae-woo Jeon, Hilmi Volkan DemirAbstract:In this study, we propose and demonstrate efficient electron-hole pair injection from InGaN/GaN multiple quantum well nanopillars (MQW-NPs) to CdSe/ZnS core/shell nanocrystal quantum dots (NQDs) via Forster-type Nonradiative Energy Transfer. For that we hybridize blue-emitting MQW-NPs with red-emitting NQDs and the resultant exciton Transfer reaches a maximum rate of (0.192 ns)−1 and a maximum efficiency of 83.0%. By varying the effective bandgap of core/shell NQDs, we conveniently control and tune the excitonic Energy Transfer rate for these NQD integrated hybrids, and our measured and computed exciton Transfer rates are found to be in good agreement for all hybrid cases.
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Efficient Nonradiative Energy Transfer from InGaN/GaN nanopillars to CdSe/ZnS core/shell nanocrystals
Applied Physics Letters, 2011Co-Authors: Sedat Nizamoglu, Burak Guzelturk, Dae-woo Jeon, Hilmi Volkan DemirAbstract:In this study, we propose and demonstrate efficient electron-hole pair injection from InGaN/GaN multiple quantum well nanopillars (MQW-NPs) to CdSe/ZnS core/shell nanocrystal quantum dots (NQDs) via Forster-type Nonradiative Energy Transfer. For that we hybridize blue-emitting MQW-NPs with red-emitting NQDs and the resultant exciton Transfer reaches a maximum rate of (0.192 ns)−1 and a maximum efficiency of 83.0%. By varying the effective bandgap of core/shell NQDs, we conveniently control and tune the excitonic Energy Transfer rate for these NQD integrated hybrids, and our measured and computed exciton Transfer rates are found to be in good agreement for all hybrid cases.
Burak Guzelturk - One of the best experts on this subject based on the ideXlab platform.
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highly efficient Nonradiative Energy Transfer from colloidal semiconductor quantum dots to wells for sensitive noncontact temperature probing
Advanced Functional Materials, 2016Co-Authors: Burak Guzelturk, Murat Olutas, Yusuf Kelestemur, Hilmi Volkan Demir, Kivanc GungorAbstract:This study develops and shows highly efficient exciton-Transferring hybrid semiconductor nanocrystal films of mixed dimensionality comprising quasi 0D and 2D colloids. Through a systematic study of time-resolved and steady-state photoluminescence spectroscopy as a function of the donor-to-acceptor molar concentration ratio and temperature, a high-efficiency Nonradiative Energy Transfer (NRET) process from CdZnS/ZnS core/shell quantum dots (QDs) directed to atomically flat CdSe nanoplatelets (NPLs) in their solid-state thin films is uncovered. The exciton funneling in this system reaches Transfer efficiency levels as high as 90% at room temperature. In addition, this study finds that with decreasing temperature exciton Transfer efficiency is increased to a remarkable maximum level of ≈94%. The enhancement in the dipole–dipole coupling strength with decreasing temperature is well accounted by increasing photoluminescence quantum yield of the donor and growing spectral overlap between the donor and the acceptor. Furthermore, NRET efficiency exhibits a highly linear monotonic response with changing temperature. This makes the proposed QD–NPL composites appealing for noncontact sensitive temperature probing based on NRET efficiencies as a new metric. These findings indicate that combining colloidal nanocrystals of different dimensionality enables efficient means of temperature probing at an unprecedented sensitivity level at nanoscale through almost complete exciton Transfer.
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Nonradiative Energy Transfer in colloidal cdse nanoplatelet films
Nanoscale, 2015Co-Authors: Burak Guzelturk, Murat Olutas, Savas Delikanli, Yusuf Kelestemur, Onur Erdem, Hilmi Volkan DemirAbstract:Nonradiative Energy Transfer (NRET) has been extensively studied in colloidal nanocrystal (quantum dots) and nanorod (quantum wires) assemblies. In this work, we present the first account of spectroscopic evidence of NRET in solid thin films of CdSe based colloidal nanoplatelets (NPLs), also known as colloidal quantum wells. The NRET was investigated as a function of the concentration of two NPL populations with different vertical thicknesses via steady state and time resolved spectroscopy. NRET takes place from the NPLs with smaller vertical thickness (i.e., larger band gap) to the ones with a larger vertical thickness (i.e., smaller band gap) with efficiency up to ∼60%. Here, we reveal that the NRET efficiency is limited in these NPL solid film assemblies due to the self-stacking of NPLs within their own population causing an increased distance between the donor–acceptor pairs, which is significantly different to previously studied colloidal quantum dot based architectures for Nonradiative Energy Transfer.
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excitonic enhancement of Nonradiative Energy Transfer to bulk silicon with the hybridization of cascaded quantum dots
Applied Physics Letters, 2013Co-Authors: Aydan Yeltik, Burak Guzelturk, Pedro Ludwig Hernandezmartinez, Shahab Akhavan, Hilmi Volkan DemirAbstract:We report enhanced sensitization of silicon through Nonradiative Energy Transfer (NRET) of the excitons in an Energy-gradient structure composed of a cascaded bilayer of green- and red-emitting CdTe quantum dots (QDs) on bulk silicon. Here NRET dynamics were systematically investigated comparatively for the cascaded Energy-gradient and mono-dispersed QD structures at room temperature. We show experimentally that NRET from the QD layer into silicon is enhanced by 40% in the case of an Energy-gradient cascaded structure as compared to the mono-dispersed structures, which is in agreement with the theoretical analysis based on the excited state population-depopulation dynamics of the QDs.
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evidence for Nonradiative Energy Transfer in graphene oxide based hybrid structures
Journal of Physical Chemistry C, 2013Co-Authors: Aydan Yeltik, Burak Guzelturk, Yusuf Kelestemur, Gokce Kucukayandogu, Somayeh Fardindoost, Hilmi Volkan DemirAbstract:Solution processed graphene variants including graphene oxide (GO) and reduced graphene oxide (RGO) are promising materials for potential optoelectronic applications. To date, efficiency of the excitation Energy Transfer into GO and RGO thin layers has not been investigated in terms of donor–acceptor separation distance. In the present work, we study Nonradiative Energy Transfer (NRET) from CdSe/CdS quantum dots into single and/or double layer GO or RGO using time-resolved fluorescence spectroscopy. We observe shorter lifetimes as the separation distance between the QDs and GO or RGO decreases. In accordance with these lifetimes, the rates reveal the presence of two different mechanisms dominating the NRET. Here we show that excitonic NRET is predominant at longer intervals while both excitonic and nonexcitonic NRET exist at shorter distances. In addition, we find the NRET rate behavior to be strongly dependent on the reduction degree of the GO-based layers. We obtain high NRET efficiency levels of ∼97 an...
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Phonon-assisted Nonradiative Energy Transfer from colloidal quantum dots to monocrystalline bulk silicon
IEEE Photonics Conference 2012, 2012Co-Authors: Aydan Yeltik, Burak Guzelturk, Pedro Ludwig Hernandez Martinez, Hilmi Volkan DemirAbstract:Silicon is one of the most dominant materials in photovoltaics. To increase optical absorption of silicon solar cells, colloidal quantum dots (QDs) have been proposed as a good sensitizer candidate owing to their favorably high absorption cross-section and tunable emission and absorption properties. To this end, QD sensitization of silicon has previously been studied by mostly facilitating radiative Energy Transfer (RET) [1,2]. Although RET based sensitization has achieved a considerable increase in conversion efficiencies in silicon photovoltaics, RET is fundamentally limited due to the effective coupling problem of emitted photons to silicon. Alternatively, Nonradiative Energy Transfer (NRET), which relies on near field dipole-dipole coupling [3], has been shown to be feasible in sensitizer-silicon hybrid systems [4–8]. Although colloidal QDs as a sensitizer have been used to facilitate NRET into silicon, the detailed mechanisms of NRET to an indirect bandgap nonluminecent material, together with the role of phonon assistance and temperature activation, have not been fully understood to date. In this study, we propose a QD-silicon nanostructure hybrid platform to study the NRET dynamics as a function of temperature for distinct separation thicknesses between the donor QDs and the acceptor silicon plane. Here, we show NRET from colloidal QDs to bulk Si using phonon assisted absorption, developing its physical model to explain temperature-dependent lifetime dynamics of NRET in these QD-Si hybrids.
Murat Olutas - One of the best experts on this subject based on the ideXlab platform.
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highly efficient Nonradiative Energy Transfer from colloidal semiconductor quantum dots to wells for sensitive noncontact temperature probing
Advanced Functional Materials, 2016Co-Authors: Burak Guzelturk, Murat Olutas, Yusuf Kelestemur, Hilmi Volkan Demir, Kivanc GungorAbstract:This study develops and shows highly efficient exciton-Transferring hybrid semiconductor nanocrystal films of mixed dimensionality comprising quasi 0D and 2D colloids. Through a systematic study of time-resolved and steady-state photoluminescence spectroscopy as a function of the donor-to-acceptor molar concentration ratio and temperature, a high-efficiency Nonradiative Energy Transfer (NRET) process from CdZnS/ZnS core/shell quantum dots (QDs) directed to atomically flat CdSe nanoplatelets (NPLs) in their solid-state thin films is uncovered. The exciton funneling in this system reaches Transfer efficiency levels as high as 90% at room temperature. In addition, this study finds that with decreasing temperature exciton Transfer efficiency is increased to a remarkable maximum level of ≈94%. The enhancement in the dipole–dipole coupling strength with decreasing temperature is well accounted by increasing photoluminescence quantum yield of the donor and growing spectral overlap between the donor and the acceptor. Furthermore, NRET efficiency exhibits a highly linear monotonic response with changing temperature. This makes the proposed QD–NPL composites appealing for noncontact sensitive temperature probing based on NRET efficiencies as a new metric. These findings indicate that combining colloidal nanocrystals of different dimensionality enables efficient means of temperature probing at an unprecedented sensitivity level at nanoscale through almost complete exciton Transfer.
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Nonradiative Energy Transfer in colloidal cdse nanoplatelet films
Nanoscale, 2015Co-Authors: Burak Guzelturk, Murat Olutas, Savas Delikanli, Yusuf Kelestemur, Onur Erdem, Hilmi Volkan DemirAbstract:Nonradiative Energy Transfer (NRET) has been extensively studied in colloidal nanocrystal (quantum dots) and nanorod (quantum wires) assemblies. In this work, we present the first account of spectroscopic evidence of NRET in solid thin films of CdSe based colloidal nanoplatelets (NPLs), also known as colloidal quantum wells. The NRET was investigated as a function of the concentration of two NPL populations with different vertical thicknesses via steady state and time resolved spectroscopy. NRET takes place from the NPLs with smaller vertical thickness (i.e., larger band gap) to the ones with a larger vertical thickness (i.e., smaller band gap) with efficiency up to ∼60%. Here, we reveal that the NRET efficiency is limited in these NPL solid film assemblies due to the self-stacking of NPLs within their own population causing an increased distance between the donor–acceptor pairs, which is significantly different to previously studied colloidal quantum dot based architectures for Nonradiative Energy Transfer.
Jong-hyeob Baek - One of the best experts on this subject based on the ideXlab platform.
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Förster-type Nonradiative Energy Transfer directed from colloidal quantum dots to epitaxial quantum wells for light harvesting applications
CLEO: 2011 - Laser Science to Photonic Applications, 2011Co-Authors: Sedat Nizamoglu, Emre Sari, Jong-hyeob Baek, Hilmi Volkan DemirAbstract:We report on Forster-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.
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Nanocrystal integrated light emitting diodes based on radiative and Nonradiative Energy Transfer for the green gap
2009 IEEE LEOS Annual Meeting Conference Proceedings, 2009Co-Authors: Sedat Nizamoglu, Emre Sari, Jong-hyeob Baek, Hilmi Volkan DemirAbstract:Recently the photometric conditions for ultra-efficient solid-state lighting have been discussed [1–2]. These studies show that a luminous efficacy of optical radiation at 408 lm/W opt and a color rendering index (CRI) of 90 at a correlated color temperature (CCT) of 3000 K are achievable at the same time. For this purpose light emitting diodes (LEDs) emitting in blue, green, yellow, and red colors at 463, 530, 573, and 614 nm with relative optical power levels of 1/8, 2/8, 2/8, and 3/8, are required, respectively [1–2]. Although In x Ga 1−x N material system is capable to cover the whole visible by changing the In composition (x), it is technically extremely challenging to obtain efficient green/yellow light emitting diodes especially at those wavelengths (i.e., at 530 nm and 573 nm, respectively) due to reduced internal quantum efficiency [2–4]. Furthermore, by using the (Al x Ga 1−x ) 1−y In y P quaternary alloy it is also possible to cover from 650 nm to 580 nm. However, the efficiencies significantly decrease towards green. Therefore, there exists a significant gap in the green-yellow spectral regions (known as “the green gap”) to make efficient light emitting diodes. To address this green gap problem, we propose and demonstrate proof-of-concept nanocrystal (NCs) hybridized green/yellow light emitting diodes that rely on both radiative Energy Transfer and Nonradiative Energy Transfer (i.e., FRET- Forster resonance Energy Transfer) for color conversion on near-ultraviolet (near-UV) LEDs.
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green yellow solid state lighting via radiative and Nonradiative Energy Transfer involving colloidal semiconductor nanocrystals
IEEE Journal of Selected Topics in Quantum Electronics, 2009Co-Authors: Sedat Nizamoglu, Emre Sari, Jong-hyeob Baek, Volkan H DemirAbstract:LEDs made of InxGa1-xN and (AlxGa1-x)1-yInyP suffer from significantly reduced quantum efficiency and luminous efficiency in the green/yellow spectral ranges. To address these problems, we present the design, growth, fabrication, hybridization, and characterization of proof-of-concept green/yellow hybrid LEDs that utilize radiative and Nonradiative [Forster resonance Energy Transfer (FRET)] Energy Transfers in their colloidal semiconductor nanocrystals (NCs) integrated on near-UV LEDs. In our first NC-LED, we realize a color-converted LED that incorporate green-emitting CdSe/ZnS core/shell NCs (lambdaPL = 548 nm) on near-UV InGaN/GaN LEDs (lambdaEL = 379 nm). In our second NC-LED, we implement a color-converted FRET-enhanced LED. For that, we hybridize a custom-design assembly of cyan- and green-emitting CdSe/ZnS core/shell NCs (lambdaPL = 490 and 548 nm) on near-UV LEDs. Using a proper mixture of differently sized NCs, we obtain a quantum efficiency enhancement of 9% by recycling trapped excitons via FRET. With FRET-NC-LEDs, we show that it is possible to obtain a luminous efficacy of 425 lm/W opt and a luminous efficiency of 94 lm/W, using near-UV LEDs with a 40% external quantum efficiency. Finally, we investigate FRET-converted light-emitting structures that use Nonradiative Energy Transfer directly from epitaxial quantum wells to colloidal NCs. These proof-of-concept demonstrations show that FRET-based NC-LEDs hold promise for efficient solid-state lighting in green/yellow.
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Green/Yellow Solid-State Lighting via Radiative and Nonradiative Energy Transfer Involving Colloidal Semiconductor Nanocrystals
IEEE Journal of Selected Topics in Quantum Electronics, 2009Co-Authors: Sedat Nizamoglu, Emre Sari, Jong-hyeob Baek, Hilmi Volkan DemirAbstract:LEDs made of InxGa1-xN and (AlxGa1-x)1-yInyP suffer from significantly reduced quantum efficiency and luminous efficiency in the green/yellow spectral ranges. To address these problems, we present the design, growth, fabrication, hybridization, and characterization of proof-of-concept green/yellow hybrid LEDs that utilize radiative and Nonradiative [Forster resonance Energy Transfer (FRET)] Energy Transfers in their colloidal semiconductor nanocrystals (NCs) integrated on near-UV LEDs. In our first NC-LED, we realize a color-converted LED that incorporate green-emitting CdSe/ZnS core/shell NCs (lambdaPL = 548 nm) on near-UV InGaN/GaN LEDs (lambdaEL = 379 nm). In our second NC-LED, we implement a color-converted FRET-enhanced LED. For that, we hybridize a custom-design assembly of cyan- and green-emitting CdSe/ZnS core/shell NCs (lambdaPL = 490 and 548 nm) on near-UV LEDs. Using a proper mixture of differently sized NCs, we obtain a quantum efficiency enhancement of 9% by recycling trapped excitons via FRET. With FRET-NC-LEDs, we show that it is possible to obtain a luminous efficacy of 425 lm/W opt and a luminous efficiency of 94 lm/W, using near-UV LEDs with a 40% external quantum efficiency. Finally, we investigate FRET-converted light-emitting structures that use Nonradiative Energy Transfer directly from epitaxial quantum wells to colloidal NCs. These proof-of-concept demonstrations show that FRET-based NC-LEDs hold promise for efficient solid-state lighting in green/yellow.
