• Title/Summary/Keyword: quantum dot

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NMR analysis of organic ligands on quantum-dots

  • Kim, Jin Hae
    • Journal of the Korean Magnetic Resonance Society
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    • v.23 no.2
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    • pp.51-55
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    • 2019
  • Quantum dot (QD) is an emerging novel nanomaterial that has wide applicability and superior functionality with relatively low cost. Nuclear magnetic resonance (NMR) spectroscopy has been contributed to elucidate various features of QDs and to improve their overall performance. In particular, NMR spectroscopy becomes an essential analytical tool to monitor and analyze organic ligands on the QD surface. In the present mini-review, application of NMR spectroscopy as a superb methodology to appreciate organic ligands is discussed. In addition, it was recently noted that ligands exert rather greater influence on diverse features of QDs than our initial anticipation, for which contribution of NMR spectroscopy is briefly reviewed.

Quenched Fano effect due to one Majorana zero mode coupled to the Fano interferometer

  • Wang, Qi;Zhu, Yu-Lian
    • Current Applied Physics
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    • v.18 no.11
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    • pp.1275-1279
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    • 2018
  • We investigate the change of the Fano effect by considering one Majorana zero mode to couple laterally to the single-dot Fano interferometer. It is found that the Majorana zero mode quenches the Fano effect thoroughly and causes the conductance to be independent of the dot level, the dot-lead coupling, and the increase of the Majorana-dot coupling. As a result, the linear conductance becomes only related to the interlead coupling and the magnetic-flux phase factor. These results can be helpful for the detection of Majorana zero mode.

Optical Characteristic of InAs Quantum Dots in an InGaAs/GaAs Well Structure (광학적 방법으로 측정된 양자우물 안의 InAs 양자점의 에너지 준위)

  • Nam H.D.;Kwack H.S.;Doynnette L.;Song J.D.;Choi W.J.;Cho W.J.;Lee J.I.;Cho Y.H.;Julien F.H.;Choe J.W.;Yang H.S.
    • Journal of the Korean Vacuum Society
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    • v.15 no.2
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    • pp.209-215
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    • 2006
  • We investigated the optical property and the electronic subband structure of InAs quantum dots in an InAsGa/GaAs well structure utilizing photoluminescence (PL), PL excitation (PLE) and near infrared transmission spectroscopy. From transmission and PLE spectra, we found three bound states in the InAs quantum dot and two bound states in InGaAs/GaAs quantum well, and correlated to the results of intersubband transitions observed in photocurrent spectrum.

Improved charge balance in quantum dot light-emitting diodes using self-assembled monolayer (자기조립단분자막을 이용한 양자점 발광다이오드의 전하 균형도 개선)

  • Sangwook Park;Woon Ho Jung;Yeyun Bae;Jaehoon Lim;Jeongkyun Roh
    • Journal of IKEEE
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    • v.27 no.1
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    • pp.30-37
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    • 2023
  • To improve the efficiency and stability of colloidal quantum dot light-emitting diodes (QD-LEDs), it is essential to achieve charge balance within the QD emissive layer. Zinc oxide (ZnO) is widely used for constructing an electron transport layer in the state-of-the-art QD-LEDs, but spontaneous electron injection from ZnO often results in excessive electrons in QDs that significantly deteriorate the performance of QD-LEDs. In this study, we demonstrated the improved performance of QD-LEDs by modifying the electron injection property of ZnO with self-assembled monolayer (SAM)-treatment. As a result of improved charge balance, the external quantum efficiency and maximum luminance of QD-LEDs with SAM-treatment were improved by 25% and 200%, respectively, compared to the devices without SAM-treatment.

Anchoring Cadmium Chalcogenide Quantum Dots (QDs) onto Stable Oxide Semiconductors for QD Sensitized Solar Cells

  • Lee, Hyo-Joong;Kim, Dae-Young;Yoo, Jung-Suk;Bang, Ji-Won;Kim, Sung-Jee;Park, Su-Moon
    • Bulletin of the Korean Chemical Society
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    • v.28 no.6
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    • pp.953-958
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    • 2007
  • Anchoring quantum dots (QDs) onto thermodynamically stable, large band gap oxide semiconductors is a very important strategy to enhance their quantum yields for solar energy conversion in both visible and near-IR regions. We describe a general procedure for anchoring a few chalcogenide QDs onto the titanium oxide layer. To anchor the colloidal QDs onto a mesoporous TiO2 layer, linker molecules containing both carboxylate and thiol functional groups were initially attached to TiO2 layers and subsequently used to capture dispersed QDs with the thiol group. Employing the procedure, we exploited cadmium selenide (CdSe) and cadmium telluride (CdTe) quantum dots (QDs) as inorganic sensitizers for a large band gap TiO2 layer of dye-sensitized solar cells (DSSCs). Their attachment was confirmed by naked eyes, absorption spectra, and photovoltaic effects. A few QD-TiO2 systems thus obtained have been characterized for photoelectrochemical solar energy conversion.