Browsing by Subject "Bulk silicon"

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    Computer-generated holograms embedded in bulk silicon with nonlinear laser lithography
    (IEEE, 2016) Turnalı, Ahmet; Tokel, Onur; Makey, Ghaith; Pavlov, Ihor; İlday, Fatih Ömer
    Recently, we have showed a direct laser writing method to form subsurface structures inside silicon by exploiting nonlinear interactions. Here, we demonstrate utilization of this phenomenon to create computer-generated holograms buried in silicon.
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    Enhanced exciton transfer from the cascaded bilayer of green-and red-emitting CdTe quantum dots into bulk silicon
    (Optical Society of America, 2013) Yeltik, Aydan; Güzeltürk, Burak; Demir, Hilmi Volkan
    We show enhanced transfer of excitons from the energy-gradient of bilayered green/red-emitting quantum dots into silicon using cascaded nonradiative energy with an overall enhancement factor of 1.3 at room temperature for solar cell sensitization. © 2013 The Optical Society.
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    Excitonic enhancement of nonradiative energy transfer to bulk silicon with the hybridization of cascaded quantum dots
    (AIP, 2013) Yeltik A.; Guzelturk, B.; Hernandez-Martinez, P. L.; Akhavan S.; Demir, Hilmi Volkan
    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. © 2013 AIP Publishing LLC.
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    Phonon-assisted nonradiative energy transfer from colloidal quantum dots to monocrystalline bulk silicon
    (IEEE, 2012) Yeltik, Aydan; Güzeltürk, Burak; Hernandez-Martinez, Pedro L.; Demir, Volkan Demir
    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. © 2012 IEEE.