• 한국분말재료학회지
• /
• 제25권4호
• /
• pp.346-354
• /
• 2018

Over the last decade, the study of the synthesis of semiconductor colloidal quantum dots has progressed at a tremendous rate. Colloidal quantum dots, which possess unique spectral-luminescent characteristics, are of great interest in the development of novel materials and devices, which are promising for use in various fields. Several studies have been carried out on hot injection synthesis methods. However, these methods have been found to be unsuitable for large-capacity synthesis. Therefore, this review paper introduces synthesis methods other than the hot injection synthesis method, to synthesize quantum dots with excellent optical properties, through continuous synthesis and large capacity synthesis. In addition, examples of the application of synthesized colloid quantum dots in displays, solar cells, and bio industries are provided.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
• /
• pp.65-65
• /
• 2015

In this talk, I will introduce two topics. The first topic is the polymer light emitting diodes (PLEDs) using graphene oxide quantum dots as emissive center. More specifically, the energy transfer mechanism as well as the origin of white electroluminescence in the PLED were investigated. The second topic is the facile synthesis of eco-friendly III-V colloidal quantum dots and their application to light emitting diodes. Polymer (organic) light emitting diodes (PLEDs) using quantum dots (QDs) as emissive materials have received much attention as promising components for next-generation displays. Despite their outstanding properties, toxic and hazardous nature of QDs is a serious impediment to their use in future eco-friendly opto-electronic device applications. Owing to the desires to develop new types of nanomaterial without health and environmental effects but with strong opto-electrical properties similar to QDs, graphene quantum dots (GQDs) have attracted great interest as promising luminophores. However, the origin of electroluminescence (EL) from GQDs incorporated PLEDs is unclear. Herein, we synthesized graphene oxide quantum dots (GOQDs) using a modified hydrothermal deoxidization method and characterized the PLED performance using GOQDs blended poly(N-vinyl carbazole) (PVK) as emissive layer. Simple device structure was used to reveal the origin of EL by excluding the contribution of and contamination from other layers. The energy transfer and interaction between the PVK host and GOQDs guest were investigated using steady-state PL, time-correlated single photon counting (TCSPC) and density functional theory (DFT) calculations. Experiments revealed that white EL emission from the PLED originated from the hybridized GOQD-PVK complex emission with the contributions from the individual GOQDs and PVK emissions. (Sci Rep., 5, 11032, 2015). New III-V colloidal quantum dots (CQDs) were synthesized using the hot-injection method and the QD-light emitting diodes (QLEDs) using these CQDs as emissive layer were demonstrated for the first time. The band gaps of the III-V CQDs were varied by varying the metal fraction and by particle size control. The X-ray absorption fine structure (XAFS) results show that the crystal states of the III-V CQDs consist of multi-phase states; multi-peak photoluminescence (PL) resulted from these multi-phase states. Inverted structured QLED shows green EL emission and a maximum luminance of ~45 cd/m2. This result shows that III-V CQDs can be a good substitute for conventional cadmium-containing CQDs in various opto-electronic applications, e.g., eco-friendly displays. (Un-published results).

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2002년도 추계학술대회 논문집 Vol.15
• /
• pp.31-34
• /
• 2002

HgTe quantum dots were synthesized in aqueous solution at room temperature by colloidal method. The synthesized materials were identified to be zincblende cubic structured HgTe quantum dots by X-ray diffraction and transmission electron microscopy image revealed that these quantum dots are agglomerate of a individual particle. The colloidally prepared HgTe quantum dots have the sphere-like shape with a diameter of approximately 4 nm. The optical properties of the HgTe quantum dots were investigated with photoluminescence(PL). The PL appears in the near-infrared region, which represent a dramatic shift from bulk HgTe behavior. The analytic results revealed that HgTe quantum dots have the broad size distribution, as PL emission spectrum covers the spectral region from 900 to 1400 nm. In this study, the factors affecting PL of HgTe quantum dots and particle size distributiont are described.會Ā᐀䁇?⨀젲岒Ā㰀會Ā㰀顇?⨀끩Ā㈀會Ā㈀?⨀䡪ఀĀ᐀會Ā᐀䡈?⨀Ā᐀會Ā᐀ꁈ?⨀硫ᜀĀ저會Ā저?⨀샟ගऀĀ저會Ā저偉?⨀栰岒ఀĀ저會Ā저ꡉ?⨀1岒Ā저會Ā저J?⨀惝ග؀Ā؀會Ā؀塊?⨀ග嘀Ā切會Ā切끊?⨀⣟ගĀ搀會Ā搀ࡋ?⨀큭킢Ā저會Ā저恋?⨀桮킢Ā저會Ā저롋?⨀⣅沥ࠀĀࠀ會Āࠀ၌?⨀샅沥Ā저會Ā저桌?⨀壆沥ሀĀ저會Ā저쁌?⨀o킢瀀ꀏ會Āᡍ?⨀棤좗ĀĀĀ會ĀĀ灍?⨀å좗ĀĀĀ會ĀĀ졍?⨀飥좗ĀĀĀ會ĀĀ⁎?⨀?ꆟᤀ

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
• /
• pp.249.1-249.1
• /
• 2015

Quantum dots (QDs) are attracting growing attention for photovoltaic device applications because of their unique electronic, optical and physical properties. Lead sulfide (PbS) QDs are one of the most widely studied materials for the devices and known to have size-tunable properties. In this context, we investigated the relationship between the size of PbS QDs and two synthesizing conditions, a concentration of ligand, oleic acid in this work, and injection temperature. The inverted colloidal quantum dot solar cells based on the heterojunction of n-type zinc oxide layer and p-type PbS QDs were also fabricated. The size of the QDs and cell properties were observed to depend on both the QD synthesizing conditions, and hence the overall efficiency of the cell could vary even though the size of QDs used was same. The QD synthesizing conditions were finally optimized for the maximum cell efficiency.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2002년도 추계학술대회 논문집 Vol.15
• /
• pp.195-197
• /
• 2002

CdTe quantum dots(QDs) were synthesized in aqueous solution by colloidal method. Photoluminescence(PL) spectra of the synthesized CdTe QDs revealed the intensity of PL peaks was stronger as the condensation time was longer. This result was thought because annealing effect by thermal energy transferred during condensation eliminated defects which act as traps and recombination centers in CdTe particle. PL intensity has stron dependence of Te precursor concentration. It confirmed the ratio of Te ion to Cd ion added during synthesis affected the particle size and size distribution of the CdTe QDs. Finally, the synthesized CdTe QDs were identified to be cubic structured CdTe quantum dots by X-ray diffraction(XRD).

• 반도체디스플레이기술학회지
• /
• 제19권4호
• /
• pp.94-98
• /
• 2020

The core/shell of nanowires (NWs) with Cu-doped CdSe quantum dots were fabricated as an electron transport layer (ETL) for perovskite solar cells, based on ZnO/TiO2 arrays. We presented CdSe with Cu2+ dopants that were synthesized by a colloidal process. An improvement of the recombination barrier, due to shell supplementation with Cu-doped CdSe quantum dots. The enhanced cell steady state was attributable to TiO2 with Cu-doped CdSe QD supplementation. The mechanism of the recombination and electron transport in the perovskite solar cells becoming the basis of ZnO/TiO2 arrays was investigated to represent the merit of core/shell as an electron transport layer in effective devices.

• 한국세라믹학회지
• /
• 제44권2호
• /
• pp.89-92
• /
• 2007

PbSe, with a band gap in the mid-infrared and a samll effective mass, is an interesting material for optical and electrical applications in infrared region. Various colloidal synthetic routes for synthesizing PbSe quantum dot nanoparticles have been developed in the last couple of years. In this work, stable colloidal solutions containing crystalline PbSe particles in the order of 5-15 nm were synthesized using different amount of acetic acid in high boiling coordinating solvents. The size and shape of PbSe nanoparticles was greatly influenced by coexistence of acetic acid in synthetic medium. It was observed by TEM that the shape of PbSe nanoparticles with different amount of acetic acid was changed from spherical to cube or star types.

• 공업화학전망
• /
• 제23권6호
• /
• pp.14-24
• /
• 2020

최근 우수한 발광 특성을 갖는 양자점을 고해상도 디스플레이의 발광 소재로 도입하고자 하는 노력이 활발하다. 양자점을 활용한 디스플레이의 실현을 위해서는 콜로이드 상태인 다색의 양자점을 고해상도로 패터닝하는 기술의 확립이 필요하다. 본 연구에서는 ethane-1,2-diyl bis(4-azido-2,3,5,6-tetrafluorobenzoate)를 양자점용 가교제로 활용하여 용액공정을 기반으로 형성된 양자점 박막을 고해상도로 패터닝한 기술을 소개하고자 한다. 위 양자점용 가교제의 양 말단에는 아지드 그룹을 포함한 작용기가 존재한다. 아지드 기는 자외선에 의해 광 활성화되어 양자점 표면의 알킬 리간드와 가교 결합을 형성함으로써, 양자점 박막에 화학적 내구성을 부여한다. 본 기술을 기반으로, 적색, 녹색, 청색의 카드뮴 기반 양자점을 고해상도로 패터닝하고 정밀하게 배열하여 인치 당 화소 수 1400 이상의 픽셀 형성에 성공하였다. 또한 가교 반응 후에도 성능 저하가 없는 양자점 박막 및 자발광 양자점 다이오드를 개발하였다.

• 한국전기전자재료학회논문지
• /
• 제31권7호
• /
• pp.443-449
• /
• 2018

We investigated the temperature-dependent photoluminescence spectroscopy of colloidal InZnP/ZnSe/ZnS (core/shell/shell) quantum dots with varying ZnSe and ZnS shell thickness in the 278~363 K temperature range. Temperature-dependent photoluminescence of the InZnP-based quantum dot samples reveal red-shifting of the photoluminescence peaks, thermal quenching of photoluminescence, and broadening of bandwidth with increasing temperature. The degree of band-gap shifting and line broadening as a function of temperature is affected little by shell composition and thickness. However, the thermal quenching of the photoluminescence is strongly dependent on the shell components. The irreversible photoluminescence quenching behavior is dominant for thin-shell-deposited InZnP quantum dots, whereas thick-shelled InZnP quantum dots exhibit superior thermal stability of the photoluminescence intensity.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
• /
• pp.84-87
• /
• 2003

HgTe quantum dots(QDs) were synthesized in aqueous solution by colloidal method. The absorption and photoluminescence(PL) spectrum of the synthesized HgTe QDs revealed the strong exitonic peak in the IR region. And the photocurrent measurement of colloidal QDs are performed using IR light source. The lineshape of the wavelength dependent intensity of photocurrent was very similar to the absorption spectrum, indicating the charges generated by the absorption of photons give direct contribution to photocurrent. The channels of dark current are supposed $H_2O$ containing in thiol by the remarkable drop of current at the state of vacuum. It was thought that the proper passivation layer on the top of HgTe film reduce the dark current and the adequate choice of capping material improves the efficiency of the photocurrent in the HgTe QDs. This study suggests that HgTe QDs are very prospective materials for optoelectronics including photodetectors in the IR range.