• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.1805-1808
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• 2006

In this paper, we describe a versatile use of fullerene(C60) as a charge transporting material for organic light-emitting diodes. The use of fullerene as a buffer layer for an anode, a doping material for hole transport layer, and an electron transport layer was investigated. Fullerene improved the hole injection from an anode to a hole transport layer by lowering the interfacial energy barrier and enhanced the lifetime of the device as a doping material for a hole transport layer. In addition, it was also effective as an electron transporting material to get low driving voltage in the device.

• Elastomers and Composites
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• v.56 no.4
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• pp.250-253
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• 2021

Polypyrrole is an organic thermoelectric material which has been receiving extensive attention in recent years. Polypyrrole is applicable in various fields because its electrical properties are controllable by its doping concentration. In this study, the effects of the polypyrrole doping state on its photoresponse were investigated. The degree of doping was controlled by ammonia solution treatment. Then, the chemical structure as a function of the doping states was observed by Raman analysis. Moreover, the photocurrent and photovoltage characteristics for various doping states were measured by an asymmetrically irradiated light source. As the degree of doping increased, the electrical conductivity increased, which affected the photocurrent. Meanwhile, the photovoltage was related to the temperature gradient caused by light irradiation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.1
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• pp.14-18
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• 2007

The electric property in the $GaAs-Al_{x}Ga_{1-x}$ quantum well with the Si ${\delta}-doping$ layer in a non-central position is studied through the effect of the electric field intensity on the electron distribution. The finite difference method is used for the calculation of the subband energy level and its wavefunction. In order to account for the change of the potential energy due to the charged particles, the self consistent method is employed. As the Si ${\delta}-doping$ layer becomes closer to the heterojunction interface, the electrons less affected by Coulomb scattering are greatly increased under the external electric field. Therefore, the high speed device is suggested due to the fact that the high mobility electrons can be increased by positioning the ${\delta}-doping$ layer in the quantum well and by applying the electric field intensity.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.300-304
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• 2002

We fabricated thick film monopole antennas using Mo-doped $BiNbO_{4}$ ceramics and investigated their electrical properties as a function of the Mo-doping concentration. Compared with undoped $BiNbO_{4}$ ceramics, 10 at.% Mo-doping improved microwave dielectric properties of ceramics by increased sintered density as well as decreased space charge density. Further increase in the Mo-doping concentration caused formation of $Bi_{2}MoO_{6}$ phases, resulting in deterioration of the microwave characteristics. The gain and bandwidth of the ceramic monopole antenna were also greatly affected by the Mo-doping concentration. When Mo-doping concentration was 10 at%, highest gain of ~0.7dBi with lowest bandwidth of 30% at 2.3GHz was obtained.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.177-180
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• 2004

발광층에 Alq3와 rubrene을 mixed host로 사용하고 DCJTB를 형광 dopant로 사용한 다층 박막 구조의 red OLEDs를 제작하였다. 소자의 구조는 $ITO:Anode(120nm)/{\alpha}-NPD:HTL(40nm)/Alq_3+Rubrene(mixed\;host\;1:1)+DCJTB(red\;dopant\;3%)+:EML(20nm)/Alq_3:ETL(40nm)/MgAg(Mg\;5%\;wt):Cathode(150nm)$ 로서 EML내부에 DCJTB를 Totally Doping Method와 Dotted-Line Doping Method의 두 가지 방법으로 도핑 하였다. Mixed host구조에 DCJTB를 6구간으로 나누어 Dotted Line Doping한 소자는 luminance yield가 $9.2cd/A@10mA/cm^2$ 이었다. 이 소자는 DCJTB만을 Totally Doping한 소자의 luminance yield $3.2cd/A@10mA/cm^2$에 비해 약 190%정도의 높은 효율 향상을 보였다. 또한 $10mA/cm^2$에 도달하는 전압은 5.5V Vs. 8.5V로서 mixed host를 사용한 소자에서 약 3V정도 구동전압이 낮아지는 효과가 있었다. 발광 스펙트럼의 Full Width Half Maximum(FWHM)은 각각 56.6nm와 61nm로서 rubrene을 mixed host로 사용한 소자에서 높은 색 순도를 얻을 수 있었다. 이러한 성능의 향상은 $Alq_3$와 혼합된 rubrene에 의한 낮은 전하주 입장벽, 높은 전류밀도에서 나타나는 발광감쇄현상의 감소, 그리고 발광층의 DLD구조에 의한 전하의 trap & confinement 에 따른 발광 exciton의 형성확률이 증가한데서 나타났다고 생각된다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.04a
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• pp.81-82
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• 2006

Doping is a well-known method for improving electroluminescent (EL) efficiency of organic light emitting diodes. In our study, doping with 2 materials simultaneously, we could achieve improved EL efficiency. The emission layer was tris-(8-hydroxyquinoline)aluminum, and the 2 dopants were N,N'-dimethyl-quinacridone (DMQA) and 10-(2-Benzothiazolyl)-2, 3, 6, 7-tetrahydro-1,1,7,7,-tetramethyl 1-1H, 5H, 11H-[1] benzopyrano [6,7,8-ij]quinolizin-11-one (C-545T). The EL intensity of co-doped device was nearly flat, it shows that co-doping technique could be a effective way to improve the EL efficiency. EL efficiency of Single-doped device based on DMQA and C-S45T were ~6.47Cd/A and ~7.45Cd/A, respectively. Co-doped device showed higher EL efficiency of ~8.30Cd/A.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.5
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• pp.285-290
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• 2015

The phase change memory material is an active element in phase change memory and exhibits reversible phase transition behavior by thermal energy input. The doping of the phase change memory material with Ga leads to the increase of its crystallization temperature and the improvement of its amorphous stability. In this study, we investigated the effect of GaGe sputtering power on the formation of the phase change memory material including Ga. The deposition rate linearly increased to a maximum of 127 nm and the surface roughness remained uniform as the GaGe sputtering power increased in the range from 0 to 75 W. The Ga concentration in the thin film material abruptly increased at the critical sputtering power of 60 W. This influence of GaGe sputtering power was confirmed to result from a combined sputtering-evaporation process of Ga occurring due to the low melting point of Ga ($29.77^{\circ}C$).

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.37 no.3
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• pp.332-336
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• 2024

High-energy bandgap material silicon carbide (SiC) is gaining attention as a next-generation power semiconductor material, and in particular, SiC-based MOSFETs are developed as representative power semiconductors to increase the breakdown voltage (BV) of conventional planar structures. However, as the size of SJ (Super Junction) MOSFET devices decreases and the depth of pillars increases, it becomes challenging to uniformly form the doping concentration of pillars. Therefore, a structure with different doping concentrations segmented within the pillar is being researched. Using Silvaco TCAD simulation, a SJ VVD (vertical variation doping profile) MOSFET with three different doping concentrations in the pillar was studied. Simulations were conducted for the width of the pillar and the doping concentration of N-epi, revealing that as the width of the pillar increases, the depletion region widens, leading to an increase in on-specific resistance (R_on,sp) and breakdown voltage (BV). Additionally, as the doping concentration of N-epi increases, the number of carriers increases, and the depletion region narrows, resulting in a decrease in R_on,sp and BV. The optimized SJ VVD MOSFET exhibits a very high figure of merit (BFOM) of 13,400 KW/cm², indicating excellent performance characteristics and suggesting its potential as a next-generation highperformance power device suitable for practical applications.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08b
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• pp.1411-1414
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• 2007

We have developed a top-emitting white organic electroluminescent device (TWOLED) incorporating a low-reflectivity molybdenum (Mo) anode and doped transport layers as well as a dual-layer architecture of doped blue and yellow emitters with the same blue host. The EL efficiency and operational lifetime of TWOLED can be enhanced by a factor of 1.2 and 3.4 than that of standard TWOLED, respectively, with a co-doping technology in yellow emitter by doping another blue dopant. The enhancement in device performances can be attributed to improve the energy transfer efficiency from blue host to yellow dopant through a blue dopant as medium in yellow emitter.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.437-438
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• 2008

박막태양전지에서 p-layer, i-layer, n-layer의 thickness와 doping concentration은 가장 기본이 되는 요소이다. 각 layer에서 위 두 가지 요소를 ASA simulator를 이용해서 높은 효율을 갖는 박막태양전지를 설계하기 위해 조절하였다. Simulation결과 p-layer의 thickness는 $9.5*10^{-9}m$, doping concentration은 0.2eV, i-layer의 thickness는 $4.535*10^{-7}m$, n-layer의 thickness는 $2*10^{-8}m$, doping concentration 은 0.1eV에서 최종 11.48%의 효율을 얻을 수 있었다. 본 연구를 통하여 높은 효율의 박막태양전지 설계 시에 도움이 될 수 있을 것이다.