• Journal of the Korean Vacuum Society
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• v.15 no.1
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• pp.81-88
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• 2006

Laterally self-aligned InGaAs/GaAs quantum-dots (QDs) have been fabricated by using a multilayer stacking technique. For the growth optimization, we vary the number of stacks and the growth temperature in the ranges of 1-15 periods and $500-540^{\circ}C$. respectively, Atomic force microscope (AFM) images and photoluminescence (PL) spectra reveal that the lateral alignment of QDs is enhanced in extended length by an increased stack period, but severely degrades into film-like wires above a critical growth temperature. The morphological and the photoluminescence characteristics of laterally self-aligned InGaAs QDs have been analyzed through mutual comparisons among four samples with different parameters. An anisotropic arrangement develops with increasing number of stacks, and high-temperature capping allows isolated QDs to be spontaneously organized into a one-dimensionally aligned chain-like shape over a few ${\mu}m$, Moreover, the migration time allowed by growth interruption plays an additional important role in the chain arrangement of QDs. The QD chains capped at high temperature exhibit blue shifts in the emission energy, which may be attributed to a slight outdiffusion of In from the InGaAs QDs.

• Current Photovoltaic Research
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• v.2 no.4
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• pp.157-167
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• 2014

Colloidal quantum dot (CQD) solar cells have attracted great attention due to their cost-effectiveness and solution-processability, as well as their size-dependent optical and electrical properties. The power conversion efficiency of CQD solar cells has rapidly increased up to ~8.6%, which corresponds to the 3 - 4 fold improvement during the last 3 - 4 years. Up to now, there have been many pioneering results in CQD solar cells. Here, we review the recent progress of CQD solar cells including CQD synthesis strategy and device structure engineering.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.135.2-135.2
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• 2014

Photon conversion technology for thin film solar cells is reviewed. The high-energy photons which are hardly absorbed in solar cells can be transformed the low energy photon by the photon conversion process such as down conversion or down shift, which can improve the solar cell efficiency over the material limit. CdSe-based quantum dot materials commonly used in LED can be used as the photon conversion layer for Si thin film solar cells. The photon conversion structure of CdSe-based quantum dot for Si thin film solar cells will be presented and the pros and cons for the Si thin film solar cells integrated with the photon conversion layers will be discussed.

• ETRI Journal
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• v.34 no.2
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• pp.284-287
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• 2012

Quantum-dot cellular automata (QCA) is one of the few alternative computing platforms that has the potential to be a promising technology because of higher speed, smaller size, and lower power consumption in comparison with CMOS technology. This letter proposes an optimized full comparator for implementation in QCA. The proposed design is compared with previous works in terms of complexity, area, and delay. In comparison with the best previous full comparator, our design has 64% and 85% improvement in cell count and area, respectively. Also, it is implemented with only one clock cycle. The obtained results show that our full comparator is more efficient in terms of cell count, complexity, area, and delay compared to the previous designs. Therefore, this structure can be simply used in designing QCA-based circuits.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.3
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• pp.151-155
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• 2014

We have developed quantum dot light emitting diodes (QD-LEDs) using a InP/ZnSe/ZnS multi-shell QD emission layer. The hybrid structure of organic hole transport layer/QD/organic electron transport layer was used for fabricating QD-LEDs. Poly(4-butylphenyl-diphenyl-amine) (poly-TPD) and tris[2,4,6-trimethyl-3-(pyridin-3-yl)phenyl]borane (3TPYMB) molecules were used as hole-transporting and electron-transporting layers, respectively. The emission, current efficiency, and driving characteristics of QD-LEDs with 50, 65 nm thick 3TPYMB layers were investigated. The QD-LED with a 50 nm thick 3TPYMB layer exhibited a maximum current efficiency of 1.3 cd/A.

• Journal of the Optical Society of Korea
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• v.18 no.1
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• pp.65-70
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• 2014

This paper presents the simulation and design of an all-optical subtractor using a quantum-dot semiconductor optical amplifier Mach-Zehnder interferometer (QD-SOA MZI) structure consisting of two cascaded switches, the first of which produces the differential bit. Then the second switch produces the borrow bit by using the output of the first switch and the subtrahend data stream. Simulation results were obtained by solving the rate equations of the QD-SOA. The effects of QD-SOA length, peak power and current density have been investigated. The designed gate can operate at speeds of over 250 Gb/s. The simulation results demonstrate a high extinction ratio and a clear and wide-opening eye diagram.

• Current Photovoltaic Research
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• v.3 no.4
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• pp.126-129
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• 2015

Over the last two decades, quantum dot (QD) solar cells have attracted much attention due to the unique properties of QDs, including band gap tunability, slow hot electron cooling, and multiple exiton generation effect. However, most of the QDs employed in photovoltaic devices contain toxic heavy-metals such as cadmium or lead, which may limit the commercial application. Therefore, recently, heavy-metal-free QDs such as Cu-In-S or Cu-In-Se have been developed for application in solar cells. Here, we review the research trends in heavy-metal-free QD solar cells, mainly focusing on Cu-In-Se QD-sensitized solar cells (QDSC).

• Food Engineering Progress
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• v.14 no.1
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• pp.21-26
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• 2010

C-Reactive protein (CRP), which is an 118 kDa pentameric protein, was secreted by the liver is an important biomarker for coronary disease, hypertension and inflammation. In this study, a method for CRP detection exploiting quantum dot (Qdot)-antibody conjugate was developed according to an indirect-competitive immunosensing protocol. For this purpose, a streptavidin-bound $Qdot_{605}$ was linked with a separately prepared biotinylated monoclonal antirat CRP antibody to produce a Qdot-antibody conjugate. The immunosensing was performed at 0.1 and 20 nM of the coating antigen and conjugate, respectively. The current method was found very sensitive in CRP detection, judging from the concentration-dependent fluorescence emission.

• Applied Chemistry for Engineering
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• v.32 no.2
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• pp.214-218
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• 2021

We investigated the optimal stacked structure from the perspective of process architecture (PA) through emission spectrum analysis according to the wavelength of quantum dot (QD)-organic light-emitting diodes (OLED). We confirmed that the blue-light leakage through the QD can be minimized by increasing the QD filling density above a critical value in the red QD (R-QD) layer. In addition, when the thickness of red-color filter (R-CF) at the upper part of the R-QD increased to more than 3 ㎛, the leakage of blue light through the R-CF was effectively blocked, and a very sharp emission spectrum in the red wavelength band could be obtained. According to these outstanding results, we expect that the development of QD-OLED displays with very excellent color gamut can be possibly realized.

• Asian Journal of Innovation and Policy
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• v.8 no.2
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• pp.274-287
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• 2019

Governments are asking policymakers to quantify the economic and social impact of those advanced technologies they support, including nanotechnology. National policymakers and researchers who participated in OECD activities cooperated to develop a model for the economic impact assessment of nanotechnology with a relevant case study. The present research contributing to some recommendations from the OECD WPN (Working Party on Nanotechnology) finds a successful example of market creation by nanotechnology, and assesses the resulting economic impact of the DEFRA (Department of Environment, Food & Rural Affairs of UK) model. This study investigates the economic impact of Quantum-dot (Qdot) nanotechnology on flat panel TV manufacturers, which is an ideal case to apply the DEFRA model for the analysis of product innovation based on nanotechnology. Findings show that Qdot nanotechnology is expected to create an economic value of $3.32 billion for Korean TV manufacturers over the next decade.