• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.297-297
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• 2010

Precise control of the position and density of doping elements at the nanoscale is becoming a central issue for realizing state-of-the-art silicon-based optoelectronic devices. As dimensions are scaled down to take benefits from the quantum confinement effect, however, the presence of interfaces and the nature of materials adjacent to silicon turn out to be important and govern the physical properties. Utilization of visible light is a promising method to overcome the efficiency limit of the crystalline Si solar cells. Si quantum dots (QDs) have been proposed as an emission source of visible light, which is based on the quantum confinement effect. Light emission in the visible wavelength has been reported by controlling the size and density of Si QDs embedded within various types of insulating matrix. For the realization of all-Si QD solar cells with homojunctions, it is prerequisite not only to optimize the impurity doping for both p- and n-type Si QDs, but also to construct p-n homojunctions between them. In this study, XPS and SIMS were used for the development of p-type and n-type Si quantum dot solar cells. The stoichiometry of SiOx layers were controlled by in-situ XPS analysis and the concentration of B and P by SIMS for the activated doping in Si nano structures. Especially, it has been experimentally evidenced that boron atoms in silicon nanostructures confined in SiO2 matrix can segregate into the Si/$SiO_2$ interfaces and the Si bulk forming a distinct bimodal spatial distribution. By performing quantitative analysis and theoretical modelling, it has been found that boron incorporated into the four-fold Si crystal lattice can have electrical activity. Based on these findings, p-type Si quantum dot solar cell with the energy-conversion efficiency of 10.2% was realized from a [B-doped $SiO_{1.2}$(2 nm)/$SiO_2(2\;nm)]^{25}$ superlattice film with a B doping level of $4.0{\times}10^{20}\;atoms/cm^2$.

• Korean Journal of Optics and Photonics
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• v.32 no.4
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• pp.163-171
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• 2021

Conventional white light-emitting diodes (LEDs) for lighting applications consist of blue LEDs and yellow phosphors, the spectrum of which lacks deep red. To improve the color-rendering characteristics of white LEDs, a red quantum-dot film was applied to the diffuser plate of LED lighting. The mean free paths of the quantum dots and the concentration of the TiO₂ particles in the diffuser plate were adjusted to optimize the optical structure of the lighting. The color-rendering index (CRI) was greater than 90 for most conditions, which demonstrates that adoption of the red quantum-dot film is an effective way for improving the color-rendering properties of conventional white LEDs. The angular dispersion of color coordinates could be removed by utilizing the optical cavity formed between the diffuser plate and the reflector on the bottom of the lighting, where multiple passages of the light through the quantum-dot film reduced the differences in optical path length depending on the viewing angle.

• Bulletin of the Korean Chemical Society
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• v.26 no.11
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• pp.1803-1806
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• 2005

Formation of octahedral shaped PbSe quantum dots at higher synthesis temperature is being reported in this paper. The synthesis includes the reaction between lead oleate and trioctylphosphine selenide under inert gas conditions to produce PbSe. TEM, SEM, XRD and EDS were used to characterize the samples. The SEM exhibited the formation of spherical shaped nanocrystals at temperature below 140 ${^{\circ}C}$ and octahedral shaped nanoparticles at higher temperatures. Moreover, the TEM also showed the well resolved (111) lattice fringes proving that the nanocrystals were crystalline in nature. Synthesis of highly pure PbSe nanocrystals was another interesting aspect of this research.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.323-323
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• 2016

솔루션 공정을 이용하여 제작된 유기물 나노 입자를 포함한 유기물 나노 복합재료를 기반으로 제작한 비휘발성 메모리 소자들은 저렴한 가격, 간단한 공정, 저전력 소비의 장점으로 차세대 메모리 소자로서 많은 연구가 진행 되고 있다. 비휘발성 메모리 소자는 poly(3-hexylthiophene) (P3HT) 층과 polymethylsilsesquioxane (PMSSQ)와 graphene quantum dots (GQD)를 혼합한 층을 사용 하여 구성하였다. 세척된 indium-tin-oxide (ITO) 기판 위에 혼합된 PMSSQ/GQD를 스핀코팅 방법으로 증착한 후 열처리 하였다. Chlorobenzene 속에서 혼합된 P3HT를 스핀코팅 방법으로 증착한 후 열처리 하였다. 알루미늄 전극을 상부 전극으로 증착하였다. 제작된 소자의 300 K에서의 전류-전압을 측정 결과는 윈도우 마진이 크게 나오는 것을 알 수 있었다. 누설전류의 감소와 내구성 및 유지성에 대한 성질을 특정한 결과 소자가 안정적으로 동작하는 것을 확인할 수 있었다.

• Ceramist
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• v.21 no.3
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• pp.270-282
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• 2018

The increasing importance of biomedical imaging technology has led to the development of a variety of luminescent materials, including molecular fluorophores, fluorescent proteins, and quantum dots. Owing to their inherent disadvantages, such as insufficient chemical stability and limited biocompatability, their utilization has been limited with imaging only under highly optimized and controlled conditions. Recently, a new class of luminescent nanoparticles, upconversion nanoparticles (UCNPs), have been emerging as a practically useful nanoprobe for various bioimaging applications. The detailed synthesis, functionalization, properties and in-vitro / in-vivo applications of the UCNPs are introduced and discussed in this Review.

• Proceedings of the Optical Society of Korea Conference
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• 2009.02a
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• pp.499-500
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• 2009

• Proceedings of the Korean Vacuum Society Conference
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• 2007.02a
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• pp.104-104
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• 2007

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.179-179
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• 2009

For the deposition of the semiconductor nanocrystals or quantum dots, it is required to have the substrates with smooth surface roughness. Slot-die coating method wad adopted and optimized varying the processing parameters like coating speed, gap distance, solution concentration, etc to get the smooth coated films on flexible substrates. The coating speed in slot-die method was varied from 1 m/min to 2.5 m/min focusing especially on its industrial usage. The gap distance between the substrate surface and slot-die lip was changed also to control mainly the thickness of coated films.

• Proceedings of the Korean Vacuum Society Conference
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• 2009.08a
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• pp.165-165
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• 2009

• Proceedings of the Korean Vacuum Society Conference
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• 2009.08a
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• pp.162-162
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• 2009