• Journal of Information Display
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• v.9 no.4
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• pp.30-34
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• 2008

Field emitter arrays (FEAs) were developed using carbon nanotubes (CNTs) as electron emission sources. The CNTs were grown using a selective-positioning technique with a resist-protection layer. The light emission properties were studied through the electron emission of the CNTs on patterned islands, which were modulated with island diameter and spacing. The electron emission of CNT arrays with $5{\mu}m$ diameters and $10{\mu}m$ heights increased with increased spacing (from $10{\mu}m$ to $40{\mu}m$). The electron emission current of the $40-{\mu}m$-island-spacing sample showed a current density of 1.33 mA/$cm^2$ at E = 11 V/${\mu}m$, and a turn-on field of 7 V/${\mu}m$ at $1{\mu}A$ emission current. Uniform electron emission current and light emission were achieved with $40{\mu}m$ island spacing and $5{\mu}m$ island diameter.

• Journal of Information Display
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• v.11 no.3
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• pp.123-127
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• 2010

Fluorescent white organic light-emitting diodes showing high color-rendering indices (CRIs) of up to 81 was demonstrated, with a silicon-cored anthracene derivative (PATSPA) doped with DPAVBi utilized as the deep-blue host and dye materials, and the commercial dyes rubrene and DCM2 utilized as the orange- and red-light-emitting dyes. The devices, consisting of three emissive layers, showed bright-white-light emission, but the ratio of the blue peak to the orange and red peaks changed with the current density and the thickness of the blue emissive layer. A high CRI was achieved with the use of a deep-blue emitter doped in a novel host and by optimizing the blue-layer thickness. The device with a blue-layer thickness of 10 nm showed the Commission Internationale de l'Eclairage (CIE) color coordinate of (0.33, 0.35), a high CRI of 81, and a moderate external quantum efficiency of 2% at a current density of $2.5\;mA/cm^2$.

• Proceedings of the KIEE Conference
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• 2000.11c
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• pp.437-439
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• 2000

The internal quantum efficiency of EL devices using fluorescent organic materials is limited within 25% because of the triplet excitons which can hardly emit light. So there has been considerable interest in finding ways to obtain light emission from triplet excitons. One approach has been to add phosphorescent compounds to one of the layers in an EL device. Then triplet excitons can transfer to these phosphorescent molecules and emit light. In this study, multilayer organic light-emitting devices with phosphorescent emitter, tris (2-phenylpyridine)iridium ($Ir(ppy)_3$) were prepared. The device exhibited power luminous efficiency of 1.07 1m/W at the luminance of $61.6\;cd/m^2$ diriven at the voltage of 9 V and current density of $1.9mA/cm^2$. At the luminance of $100\;cd/m^2$, the luminous efficiency was obtained 1.05 lm/W with the voltage of 9.5 V and the corrent density of $2.8\;mA/cm^2$.

• Bulletin of the Korean Chemical Society
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• v.24 no.7
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• pp.961-966
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• 2003

A quantum-chemical study of conformations and electronic structures of polyheterocyclic derivatives with vinylenediheteroatom substituents at the 3- and 4-positions was performed to search for novel blue-lightemitting conjugated polymers. Conformational potential energy curves of the polymers were constructed as a function of the helical angle (a) through semiempirical Hartree-Fock band calculations at the Austin model 1 level. It is found that poly(3,4-vinylenedioxythiophene) possesses a quite flat curve in the range of α = 51.4°- 120°. Replacing S atoms for O atoms greatly increases repulsion between the neighboring units, and thereby the units become perpendicular to one another. Because of the hydrogen bonding between O and NH, poly(3,4- vinylenedioxypyrrole) is predicted to be anti-coplanar and poly(3,4-vinylenediaminofuran) to be nearly anticoplanar. According to the modified extended Huckel band calculations, the HOMO-LUMO gaps (HLGs) of the polymers, unless the polymer chains are twisted, are close to or slightly smaller than those of their respective mother polymers. Among the polymers, poly(3,4-vinylenedioxythiophene) is presumed to be the most probable candidate for a blue-light emitter because its HLG is within the range of the electronic requirement for blue-light emitters.

• Bulletin of the Korean Chemical Society
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• v.26 no.1
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• pp.19-31
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• 2005

During the last decade, the exploration of nanoscale device and circuitry based on molecules has gained increasing interest. In parallel with this, considerable effort is being devoted to the development of molecular photonic/electronic materials based on various porphyrin arrays. This involves light as an input/output signal and excitation energy migration as a mechanism for signal transmission. Absorption of a photon at the light collector end of the porphyrin array yields the excited state, which migrates among the intervening pigments until reaching the emitter, whereupon another photon is emitted. As a consequence, it is relevant to understand the excitation energy transfer (EET) processes occurring in various forms of porphyrin arrays for the applications as artificial light harvesting arrays and molecular photonic/electronic wires. Since the excitonic (dipole) and electronic (conjugation) couplings between the adjacent porphyrin moieties in porphyrin arrays govern the EET processes, we have characterized the EET rates of various forms of multiporphyrin arrays (linear, cyclic, and box) based on various time-resolved spectroscopic measurements. We believe that our observations provide a platform for further development of molecular photonic/electronic materials based on porphyrin arrays.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.724-726
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• 2004

Highly efficient blue organic light-emitting devices (OLEDs) utilizing the idea of copper phthalocyanine (CuPc)/N,N'-bis-(1-naphthyl)-N,N'-diphenyl,1,1'-biphenyl- 4,4'-diamine (NPB) composite hole transport layer (CPHTL) have been fabricated. The effect of inserting CPHTL upon the performance of blue OLEDs with 2-methyl-9,10-di(2-naphthyl)anthracene (MADN) as the blue emitter has been investigated. Compared with the luminous efficiency of the standard blue device without CPHTL (1.33 cd/A), that of the device with 40:60 CuPc/NPB CPHTL has been increased by more than twice up to 2.96 cd/A with a Commission Internationale d'Eclairage (CIE) coordinates of(x = 0.15, y = 0.10) and a power efficiency of 1.46 lm/W (20 mA/$cm^2$) at 6.39 V. The increased device efficiency is attributed to an improved balance between hole and electron currents arriving at the recombination zone.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2007.05a
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• pp.3-6
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• 2007

The Light brightness is to enhance the luminescence efficiency of phosphor including conductive material. In preparing the anode layer, phosphors mixed with conductive material prepared with pastes of polymer resin using by screen printing method. When the prepared anode layer bombarded by cold electron from emitter of cathode, it give rise to form the secondary electron from those of conductive materials such as ITO powder. Furthermore, we are expect to enhance the luminescence efficiency more than without conductive material.

• Ceramist
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• v.21 no.1
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• pp.98-111
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• 2018

The lead-based perovskite (CH3NH3PbI3) material has a high molar coefficient, high crystallinity at low temperature, and long range of balanced electron-hole transport length. In addition, PCE of perovskite solar cells (PSCs) has been dramatically improved by over 22% by amending the electronic quality of perovskite and by using state-of-the-art hole transporting materials (HTMs) such as tetrakis(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (spiro-OMeTAD) due to enhanced charge transport toward the electrode via properly aligned energy levels with respect to the perovskite. Replacing the spiro-OMeTAD with new HTMs with the desired properties of appropriate energy levels, high hole mobility in its pristine form, low cost, and easy processable materials is necessary for attaining highly efficient and stable PSCs, which are anticipated to be truly compatible for practical application. Furthermore, Recently Pb-free perovskite materials much attention as an alternative light-harvesting active layer material instead of lead based perovskite in photovoltaic cells. In this work, we demonstrate a Pb-free perovskite material for the light harvesting and emitter as optoelectronic devices.

• Current Photovoltaic Research
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• v.6 no.4
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• pp.94-101
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• 2018

Light elevated temperature induced degradation (LeTID) was noted as an issue in multi-crystalline silicon solar cells (MSSC) by Ram speck in 2012. In contrast to light induced degradation (LID), which has been researched in silicon solar cells for a long time, research about both LeTID and the mechanism of LeTID has been limited. In addition, research about LeTID in single-crystalline silicon solar cells (SSSC) is even more limited. In order to improve understanding of LeTID in SSSC with a passivated emitter rear contact (PERC) structure, we fabricated four group samples with boron and oxygen factors and evaluated the solar cell characteristics, such as the cell efficiency, $V_{oc}$, $I_{sc}$, fill factor (FF), LID, and LeTID. The trends of LID of the four group samples were similar to the trend of LeTID as a function of boron and oxygen.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.04b
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• pp.57-60
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• 2002

In generally, the guest-emitter doped system has been reported to give a bright electroluminescence(EL). The purpose of using doped system is to improve for increasing lifetime and efficiency, and tuning multicolor light. This indicates an enhanced electron-hole recombination rate in emitting layer. The purpose of this study is to obtain the high performance EL devices for flat panel display with red emission. We fabricated EL devices using the guest-host system. where DCM derivatives were taken as a dopant. The devices are fabricated in multilayer system with various concentration of the dopant (red light emitting dye). We measured the I-V characteristics and EL spectra from these devices. and we compared with photoluminescence(PL) quantum yield among the DCM derivatives. The emission mechanism of devices is participated in energy transfer. The energy transfer from these hosts to DCM generates luminescence spectra that vary from yellow red to red, depending on DCM derivatives. Absorption and emission spectra of organic materials composing the devices depend on the emission materials doped with the DCM derivatives. We demonstrated that the high EL efficiency can be achieved by doping host material with DCM derivatives and molecular steric structures