• Journal of the Korean Electrochemical Society
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• v.14 no.1
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• pp.1-8
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• 2011

Ionic liquids are room-temperature molten salts, composed of organic mostly of organic ions that may undergo almost unlimited structural variation. We approach the new aspects of ionic liquids in applications where the semiconductor nanoparticles used as sensitizers of solar cells. We studied the effects of ionic liquids as capping ligand and/or solvent, on the morphology and phase of the CdSe/ZnS nanoparticles. Colloidal CdSe/ZnS nanoparticles were synthesized using a series of imidazolium ionic liquids; 1-R-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([RMIM][TFSI]), where R = ethyl ([EMIM]), butyl ([BMIM]), hexyl ([HMIM]), octyl ([OMIM]). The average size of nanoparticles was 8~9 nm, and both zinc-blende and wurtzite phase was produced. We also synthesized the nanoparticles using a mixture of trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide ([$P_{6,6,6,14}$][TFSI]) and octadecene (ODE). The CdSe/ZnS nanoparticles have a smaller size (5.5 nm) than that synthesized using imidazolium, and with a controlled phase from zinc-blende to wurtzite by increasing the volume ratio of [$P_{6,6,6,14}$][TFSI]. For the first time, the phase and size control of the CdSe/ZnS nanoparticles was successfully demonstrated using those ionic liquids.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.531-531
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• 2012

So many groups have been researching the green quantum dots such as InP, InP/ZnS for overcoming the semiconductor nanoparticles composed with heavy metals like as Cd and Pb so on. In spite of much effort to keep up CdSe quantum dots, it does not reach the good properties compared with CdSe/ZnS quantum dots. This quantum dot has improved its properties through the generation of core/shell CdSe/ZnS structure or core/multi-shell structures like as CdSe/CdS/ZnS and CdSe/CdS/ CdZnS/ZnS. In this research, we try to synthesize the InP multi-shell structure by the successiveion layer absorption reaction (SILAR) in the one pot. The synthesized multi-shell structure has improved quantum yield and photo-stability. To generate white light, highly luminescent InP multi-shell quantum dots were mixed with yellow phosphor and integrated on the blue LED chip. This InP multi-shell improved red region of the LEDs and generated high CRI.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.148-148
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• 2015

Over the past several years, Colloidal core/shell type quantum dots lighting-emitting diodes (QDLEDs) have been developed for the future of optoelectronic applications. An inverted-type quantum-dot light-emitting-diode (QDLED), employing low work function organic material polyethylenimine ethoxylated(PEIE) (<10 nm)[1] modified ZnO nanoparticles (NPs) as electron injection and transport layer, was fabricated by all solution processing method, instead of electrode in the device. The PEIE surface modifier incorporated on the top of the ZnO NPs film, facilitates the enhancement of both electorn injection into the CdSe-ZnS QD emissive layer by lowering the workfunction of ZnO from 3.58eV to 2.87eV and charge balance on the QD emitter. In this inverted QDLEDs, blend of poly (9,9-di-n-octyl-fluorene-alt-benzothiadiazolo) and poly(N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine] are used as hole transporting layer (HTL) to improve hole transporting property. At the operating voltage of 7.5 V, the QDLED device emitted spectrally orange color lights with high luminance up to 11110 cd/m2, and showed current efficiency of 2.27 cd/A.[2]

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.2
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• pp.108-113
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• 2013

Chalcopyrite material $CuInSe_2$ (CIS) is known to be a very prominent absorber layer for high efficiency thin film solar cells. Current interest in the photovoltaic industry is to identify and develop more suitable materials and processes for the fabrication of efficient and cost-effective solar cells. Various processes have been being tried for making a low cost CIS absorber layer, this study obtained the CIS nanoparticles using commercial powder of 6 mm pieces for low cost CIS absorber layer by high frequency ball milling and cryogenic milling. And the CIS absorber layer was prepared by paste coating using milled-CIS nanoparticles in glove box under inert atmosphere. The chalcopyrite $CuInSe_2$ thin films were successfully made after selenization at the substrate temperature of $550^{\circ}C$ in 30 min, CIS solar cell of Al/ZnO/CdS/CIS/Mo structure prepared under various deposition process such as evaporation, sputtering and chemical vapor deposition respectively. Finally, we achieved CIS nanoparticles solar cell of electric efficient 1.74 % of Voc 29 mV, Jsc 35 $mA/cm^2$ FF 17.2 %. The CIS nanoparticles-based absorber layers were characterized by using EDS, XRD and HRSEM.

• Korean Chemical Engineering Research
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• v.50 no.4
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• pp.729-732
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• 2012

Herein we report the in-situ synthesis and direct decoration of chalcogenide naoparticles (NPs) onto multiwalled carbon nanotubes (MWCNTs) through an ionic liquid-assisted sonochemical method (ILASM). The as-obtained MWCNT/$BMimBF_4$/CdTe, MWCNT/$BMimBF_4$/ZnTe and MWCNT/$BMimBF_4$/ZnSe nanocomposites were characterized by TEM images and EDS spectra. In particular, the morphologies of nanocomposites such as bump-like, rough, and smooth core-shell structures were strongly influenced by the type of precursors and the interactions with MWCNT. This synthetic strategy opens a new way to directly synthesize and deposit semiconducting NPs (s-NPs) onto CNTs, which consist of binary components obtained from two precursors with different reaction rates.

• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.222-224
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• 2006

A non-vacuum process for $Cu(In,Ga)Se_2$ (CIGS) thin film solar cells from nanoparticle precursors was described in this work CIGS nanoparticle precursors was prepared by a low temperature colloidal route by reacting the starting materials $(CuI,\;InI_3,\;GaI_3\;and\;Na_2Se)$ in organic solvents, by which fine CIGS nanoparticles of about 20nm in diameter were obtained. The nanoparticle precursors were mixed with organic binder material for the rheology of the mixture to be adjusted for the doctor blade method. After depositing the mixture of CIGS with binder on Mo/glass substrate, the samples were preheated on the hot plate in air to evaporate remaining solvents ud to burn the organic binder material. Subsequently, the resultant (porous) CIGS/Mo/glass simple was selenized in a two-zone Rapid Thermal Process (RTP) furnace in order to get a solar ceil applicable dense CIGS absorber layer. Complete solar cell structure was obtained by depositing. The other layers including CdS buffer layer, ZnO window layer and Al electrodes by conventional methods. The resultant solar cell showed a conversion efficiency of 0.5%.

• Proceedings of the Korean Vacuum Society Conference
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• 2008.02a
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• pp.116-116
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• 2008

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.244.2-244.2
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• 2011

We introduce a novel and robust method for the preparation of nanocomposite multilayers, which allows the excellent photoluminescent (PL) properties as well as the accurate control over the composition and dimensions of multilayers. By exchanging the oleic acid stabilizers of CdSe@ZnS quantum dots (QDs) synthesized in organic solvent with 2-bromo-2-methylpropionic acid (BMPA) in the same solvent, these nanoparticles were be alternately deposited by nucleophilic substitution reaction with highly branched poly(amidoamine) dendrimer (PAMA) through layer-by-layer (LbL) assembly process. Our approach does not need to be transformed into the water-dispersible nanoparticles with electrostatic or hydrogen-bonding groups, which can deteriorate their inherent properties, for the built-up of multilayers. The nanocomposite multilayers including QDs exhibited the strong PL properties achieving densely packed surface coverage as well as long-term PL stability under atmospheric conditions in comparison with those of conventional LbL multilayers based on electrostatic interaction. Furthermore, we demonstrate that the flexible multilayer films with optical properties can be easily prepared using nucleophilic substitution reaction between bromo and amino groups in organic media. This robust and tailored method opens a new route for the design of functional film devices based on nanocomposite multilayers.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.105-106
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• 2013

Surface plasmon resonance (SPR) is classified into the propagating surface plasmon (PSP) excited on flat metal surfaces and the local surface plasmon (LSP) excited by metalnanoparticles. It is known that fluorescence signals are enhanced by these two SPR-fields.On the other hand, fluorescence is quenched by the energy transfer to metal (FRET). Bothphenomena are controlled by the distance between dyes and metals, and the degree offluorescence enhancement is determined by the correlation. In this study, we determined thecondition to achieve the maximum fluorescence enhancement by adjusting the distance of ametal nanoparticle 2D sheet and a quantum dots 2D sheet by the use of $SiO_2$ spacer layers. The 2D sheets consisting of myristate-capped Ag nanoparticles (AgMy nanosheets) wereprepared at the air-water interface and transferred onto hydrophobized gold thin films basedon the Langmuir-Schaefer (LS) method [1]. The $SiO_2$ sputtered films with different thickness (0~100 nm) were deposited on the AgMy nanosheet as an insulator. TOPO-cappedCdSe/CdZnS/ZnS quantum dots (QDs, ${\lambda}Ex=638nm$) [2] were also transferred onto the $SiO_2$ films by the LS method. The layered structure is schematically shown in Fig. 1. The result of fluorescence measurement is shown in Fig. 2. Without the $SiO_2$ layer, the fluorescence intensity of the layered QD film was lower than that of the original QDs layer, i.e., the quenching by FRET was predominant. When the $SiO_2$ thickness was increased, the fluorescence intensity of the layered QD film was higher than that of the original QDs layer, i.e., the SPR enhancement was predominant. The fluorescence intensity was maximal at the $SiO_2$ thickness of 20 nm, particularly when the LSPR absorption wavelength (${\lambda}=480nm$) was utilized for the excitation. This plasmonic nanosheet can be integrated intogreen or bio-devices as the creation point ofenhanced LSPR field.