• Journal of the Korean Institute of Telematics and Electronics D
• /
• v.35D no.11
• /
• pp.55-61
• /
• 1998

Organic light emitting devices from a single layer thin film with a hole transport polymer, poly(N-vinylcarbazole) (PVK) doped with 2-(4-bi phenyl)-5-(4-t-butyl-phenyl) -1,3,4-oxadiazole (Bu-PBD) as electron transporting molecules and Coumurine 6(C6), 1,1,4,4-tetraphenyl-1,3-butadiene (TPB), Rhodamine B as a emitter dye were fabricated. The sing1e layer structure and the use of soluble materials simplify the fabrication of devices by spin coating technique. The active layer consists of one polymer layer that is simply sandwiched between two electrodes, indium-tin oxide (ITO), and aluminum. In this structure, electron and hole inject from the electrodes to the PVK : Bu-PBD active layer. Respectively, Blue, green and orange colored emission spectrum by the use of TPB, C6, Rhodamine B dye emitted at 481nm, 500nm and 585nm were achieved during applied voltages. PVK materials can be useful as the host polymer to be molecularly doped with other organic dyes of the different luminescence colors. And EL color can be tuned to the full visible wavelength.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.27 no.4
• /
• pp.232-237
• /
• 2014

We have fabricated white organic light-emitting diodes (OLEDs) by co-doping of red and blue phosphorescent guest emitters into the single host layer. Tris(2-phenyl-1-quinoline) iridium(III) [$Ir(phq)_3$] and iridium(III)bis[(4,6-di-fluorophenyl)-pyridinato-$N,C^{2^{\prime}}$]picolinate (FIrpic) were used as red and blue dopants, respectively. The effects of dopant concentration on the emission, carrier conduction and external quantum efficiency characteristics of the devices were investigated. The emissions on the guest emitters were attributed to the energy transfer to the guest emitters and direct excitation by trapping of the carriers on the guest molecules. The white OLED with 5% FIrpic and 2% $Ir(phq)_3$ exhibited a maximum external quantum efficiency of 19.9% and a maximum current efficiency of 45.2 cd/A.

• Structural Engineering and Mechanics
• /
• v.34 no.4
• /
• pp.449-474
• /
• 2010

A smart hollow cylinder consisting of a host functionally graded elastic core layer and two surface homogeneous piezoelectric layers is presented in this paper. The bonding between the layers can be perfect or imperfect, depending on the parameters taken in the general linear spring-layer interface model. The effect of such weak interfaces on free vibration and steady-state response is then investigated. Piezoelectric layers at inner and outer surfaces are polarized axially or radially and act as a sensor and an actuator respectively. For a simply supported condition, the state equations with non-constant coefficients are obtained directly from the formulations of elasticity/piezoelasticity. An approximate laminated model is then introduced for the sake of solving the state equations conveniently. It is further assumed that the hollow cylinder is embedded in an elastic medium and is simultaneously filled with compressible fluid. The interaction between the structure and its surrounding media is taken into account. Numerical examples are finally given with discussions on the effect of some related parameters.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2014.02a
• /
• pp.227-227
• /
• 2014

OLED 소자에 사용되는 유기물들은 대부분 전자에 비해 정공의 이동속도가 매우 빨라 소자 효율의 손실이 일어난다. 본 연구에서는 이러한 전하 이동도의 불균형에 의한 OLED 소자 성능의 감소를 개선하기 위해 HBL (hole blocking layer) 물질로 BCP (HOMO : 6.5 eV, LUMO : 2.83 eV)를 도입하였다. 그러나 BCP의 LUMO 값이 약 3 eV를 가지기 때문에 전자의 이동에 영향을 미치는 것으로 예상되어 더 높은 효율을 가지는 소자를 제작하기 위해 host 물질을 상용물질(PGH02)로 교체하였다. PGH02의 HOMO 값은 약 5.86 eV로 소자에 사용된 HTL (hole transport layer)의 HOMO 값(5.54 eV)에 비해 높은 값을 가지기 때문에 HBL의 역할 역시 가능하여 소자의 성능이 상당히 개선되는 것을 확인할 수 있었다. 또한 전하 이동도의 균형을 맞추기 위해 ETL 물질로는 기존에 많이 사용되고 있는 Alq3 (${\mu}{\sim}10-5cm2/Vs$)에 비해 이동도가 10배 이상 빠른 Bebq2 (${\mu}{\sim}10-4cm2/Vs$)를 사용하였다. HTL (hole transport layer) 물질로는 상용물질(LHT 259)를 사용하였고, LHT 259의 전하 이동도는 FET (field effect transistor)를 제작하여 측정하였다. 이를 기반으로 하여 ETL과 HTL의 두께를 조절하여 전하 이동도가 균형을 이루는 OLED 소자를 제작하기 위해 실험을 진행하였다.

• Proceedings of the KIEE Conference
• /
• 2002.07d
• /
• pp.2325-2327
• /
• 2002

포항 가속기연구소(PAL)에서는 포항방사광가속기(PLS)가 가동을 시작한 1994년 이후 현재까지 사용되어 온 기존의 제어 시스템을 새로운 환경인 EPICS(Experimental Physics and Industrial Control System) 시스템으로 개발하고 있다. EPICS 시스템의 구성은 IOC(Input/Ouput Controller) 와 OPI(Operator Interface)의 2-Layer로 구성되며 이는 MIU(Machine Interfaces Unit), SCC(Subsystem Computer Control System) 그리고 HMI(Human Machine Interface)로 이어지는 기존의 3-Layer 단계 중 SCC단계를 줄여 2-Layer로 구성된다. 이들 두 계층간의 통신은 Client(OPI)/Server(IOC) 구조의 Channel Access를 통해서 이루어진다. 개발중인 EPICS 시스템은 Open Architecture 구조로 IOC와 OPI 각 부분에서 개발시에 사용된 운영체제나 Hardware 를 사용하지 않고 다른 운영체제나 Hardware를 사용하더라도 하나의 공통부분 즉, Channel Access만 있으면 이를 통해 서로 다른 Subsystem IOC의 데이터를 Access할 수 있다. 전체 EPICS 제어시스템 중 저장링 운전의 핵심이 되는 BPM(Beam Position Monitoring) 및 MPS(Magnet Power Supply) 시스템은 IOC부분에 MVME5100(Target Machine) 보드와 vxWorks(Operating System)를 이용하고 OPI부분에는 SUN Workstation(Host Machine)와 Solaris(Operating System)을 사용하여 개발하고 있다. 본 논문에서는 IOC 및 OPI의 설치 절차와 설치 방법에 대해 기술하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2008.06a
• /
• pp.182-183
• /
• 2008

We fabricated a pentacene thin film transistor with Poly-vinylalcohol (PVA) as a dielectric. And we used Poly(9-vinylcarbazole) (PVK) as a buffer layer to improve the electrical characteristics. PVK is a material used often host material for OLED device, as it has good film forming properties, large HOMO-LUMO(highest occupied molecular orbital-lowest unoccupied molecular orbital) bandgap. The performance of a OTFT device with PVA gate dielectric was improved by using the PVK. Field effect mobility, threshold voltage, and on-off current ratio of device with PVK layer were about 0.6 $cm^2$/Vs, -17V, and $5\times10^5$, respectively.

• Korean Journal of Materials Research
• /
• v.26 no.3
• /
• pp.117-122
• /
• 2016

White organic light-emitting diodes with a structure of indium-tin-oxide [ITO]/N,N-diphenyl-N,N-bis-[4-(phenylm-tolvlamino)-phenyl]-biphenyl-4,4-diamine [DNTPD]/[2,3-f:2, 2-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile [HATCN]/1,1-bis(di-4-poly-aminophenyl) cyclo -hexane [TAPC]/emission layers doped with three color dopants/4,7-diphenyl-1,10-phenanthroline [Bphen]/$Cs_2CO_3$/Al were fabricated and evaluated. In the emission layer [EML], N,N-dicarbazolyl-3,5-benzene [mCP] was used as a single host and bis(2-phenyl quinolinato)-acetylacetonate iridium(III) [Ir(pq)2acac]/fac-tris(2-phenylpyridinato) iridium(III) $[Ir(ppy)_3]$/iridium(III) bis[(4,6-di-fluoropheny)-pyridinato-N,C2] picolinate [FIrpic] were used as red/green/blue dopants, respectively. The fabricated devices were divided into five types (D1, D2, D3, D4, D5) according to the structure of the emission layer. The electroluminescence spectra showed three peak emissions at the wavelengths of blue (472~473 nm), green (495~500 nm), and red (589~595 nm). Among the fabricated devices, the device of D1 doped in a mixed fashion with a single emission layer showed the highest values of luminance and quantum efficiency at the given voltage. However, the emission color of D1 was not pure white but orange, with Commission Internationale de L'Eclairage [CIE] coordinates of (x = 0.41~0.45, y = 0.41) depending on the applied voltages. On the other hand, device D5, with a double emission layer of $mCP:[Ir(pq)_2acac(3%)+Ir(ppy)_3(0.5%)]$/mCP:[FIrpic(10%)], showed a nearly pure white color with CIE coordinates of (x = 0.34~0.35, y = 0.35~0.37) under applied voltage in the range of 6~10 V. The luminance and quantum efficiency of D5 were $17,160cd/m^2$ and 3.8% at 10 V, respectively.

• Journal of Information Display
• /
• v.2 no.3
• /
• pp.1-5
• /
• 2001

The effect of doping on the energy transfer and charge carrier trapping processes has been studied in organic light-emitting diodes (OLEDs) doped with a fluorescent laser dye. The devices consisted of N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1-biphenyl-4,4'-diamine (TPD) as a hole transporting layer, tris(8-hydroxyquinoline) aluminum ($Alq_3$) as the host, and a fluorescent dye, 4-dicyanomethylene-2-methyl-6-[2-(2,3,6,7-tetrahydro-1 H,5H-benzo[i,j]quinolizin-8-yl) vinyl]-4H-pyran) (DCM2) as the dopant. Temperature dependence of the current-voltage-luminescence (I-V-L) characteristics, the electroluminescence (EL) and photoluminescence (PL) spectra are studied in the temperature ranging between 15 K and 300 K. The emission from DCM2 was seen to be much stronger compared with the emission from $Alq_3$, indicative of efficient energy transfer from $Alq_3$ to DCM2. In addition, the EL emission from DCM2 increasd with increasing temperature while the emission from the host $Alq_3$ decreased. The result indicates that direct charge carrier trapping becomes efficient with increasing temperature. The EL emission from DCM2 shows a slightly sublinear dependence on the current density, implying the enhanced quenching of excitons at high current densities due to the exciton-exciton annihilation.

• Proceedings of the KAIS Fall Conference
• /
• 2008.11a
• /
• pp.201-203
• /
• 2008

ITO 투명전극을 양극으로 사용하고 PEDOT:PSS 고분자 물질위에 PVK와 Ir(ppy)3를 각각 host와 dopant로 사용하여 고분자 발광다이오드를 제작하였다. 전자 수송층의 역할로 TPBI, 음극으로 Al을 증착하여 최종적으로 ITO/PEDOT:PSS/PVK:Ir(ppy)3/TPBI/LiF/Al 구조를 갖는 녹색 인광 고분자 유기발광소자(PhPLED)를 제작하였다. 제작 된 소자의 발광부 dopant인 Ir(ppy)3도핑 농도에 따른 전기적 광학적 특성을 평가하였다. PVK:Ir(ppy)3를 host와 dopant system으로 dopant Ir(ppy)3의 도핑 양을 0.5 wt%에서2.5 wt%까지 씩 변화시키면서 최적의 농도를 찾고자 하였다. TPBI를 전자 수송층으로 사용 하였을 경우 최대 휘도는 약 8600 cd/$m^2$ (at 8V)이고, 전류밀도는 337mA/$cm^2$ 를 나타내었다.

• Journal of Microbiology and Biotechnology
• /
• v.30 no.12
• /
• pp.1870-1875
• /
• 2020

Probiotics are often infused into functional foods or encapsulated in a supplement form to maintain a healthy balance between the gut microbiota and their host. Because there are milk-based functional foods such as yogurt and cheese on the market, it has been suggested that milk-based probiotics could be incorporated into skim milk proteins in a liquid capsule. Skim milk is mainly composed of casein and whey protein, which create a strong natural barrier and can be used to encapsulate probiotics. In this study, we compared the encapsulated probiotics prepared with milk-based concentrated cell mixtures using commercial probiotics. Probiotic capsules were emulsified with skim milk proteins using vegetable oil to form a double coating layer. The product was heat-stable when tested using a rheometer. The survival rate of the milk-based probiotic cells in the lower gastric environment with bile was significantly higher than commercial probiotics. Thus, milk-encapsulated probiotics exhibited greater efficacy in the host than other types of probiotics, suggesting that the former could be more viable with a longer shelf life under harsh conditions than other form of probiotics. Our findings suggested that, compared with other types of probiotics, milk-based probiotics may be a better choice for producers and consumers.