• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.184-187
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• 2009

In this paper, we study effect of charge balance on performance of blue phosphorescent organic light emitting diodes (OLEDs). Charge balance determines the location of recombination zone in the OLEDs. By tuning the charge balance in iridium (III) bis[(4,6-difluorophenyl)-pyridinate-N,C2']picolinate (FIrpic) based blue phosphorescent organic light-emitting devices (PHOLEDs) with a high mobility and high triplet energy electron transporting material, we were able to achieve a high current efficiency of 60 cd/A which is a 3X improvement over previous devices with 3,5'-N,N'-dicarbazole-benzene (mCP) host.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.3-6
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• 2004

Power semiconductor devices are being compact, high performance and intelligent thanks to recent remarkable developments of silicon design, process and related packaging technologies. Developments of MOS-gate transistors such as MOSFET and IGBT are dominant thanks to their advantages on high speed operation. In conjunction with package technology, silicon technologies such as trench, charge balance and NPT will support future power semiconductors. In addition, wide band gap material such as SiC and GaN are being studies for next generation power semiconductor devices.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.82.2-82.2
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• 2011

A channel design which is closely related with the mass transport overpotential is one of the most important procedures to optimize the whole fuel cell performance. In this study, three dimensional results of a numerical study for gas distribution in channels of a molten carbonate fuel cell (MCFC) unit cell for a 1kW class stack was presented. The relationship between the fuel and air distribution in the anode and cathode channels of the unit cell and the electric performance was observed. A charge balance model in the electrodes and the electrolyte coupled with a heat transfer model and a fluid flow model in the porous electrodes and the channels was solved for the mass, momentum, energy, species and charge conservation. The electronic and ionic charge balance in the anode and cathode current feeders, the electrolyte and GDEs were solved for using Ohm's law, while Butler-Volmer charge transfer kinetics described the charge transfer current density. The material transport was described by the diffusion and convection equations and Navier-Stokes equations govern the flow in the open channel. It was assumed that heat is produced by the electrochemical reactions and joule heating due to the electrical currents.

• Journal of the Korean Electrochemical Society
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• v.22 no.1
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• pp.43-52
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• 2019

As the application area of lithium secondary batteries becomes wider, performance characterization becomes difficult as well as diverse. To address this issue, battery manufacturers have to evaluate many batteries for a longer period, recruit many researchers and continuously introduce expensive equipment. Simulation techniques based on battery modeling are being introduced to solve such difficulties. Various lithium secondary battery modeling techniques have been reported so far and optimal techniques have been selected and utilized according to their purpose. In this review, the electrochemical modeling based on the Newman model is described in detail. Particularly, we will explain the physical meaning of each equation included in the model; the Butler-Volmer equation, which represents the rate of electrode reaction, the material and charge balance equations for each phase (solid and liquid), and the energy balance. Moreover, simple modeling processes and results based on COMSOL Multiphysics 5.3a will be provided and discussed.

• Journal of the Korean Electrochemical Society
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• v.2 no.2
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• pp.75-80
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• 1999

Li-ion cells employ lithium transtion metal oxide as the cathode material and carbon as anode material. To manufacture Li-ion cell with higher capacity and better cycle life, the utilization of electrode materials should be as high as possible without lithium deposition onto the carbon surface during charging. A careful design of cell balance between cathode and anode materials as well as a proper charge method is a key factor to design Li-ion cell with long cycle life. In this study, we investigated the effect of cathode/anode weight ratio on the performance of $LiCoO_2/MPCF$ cell. First we evaluated the charge-discharge behaviours of half-cells. And cylindrical Li-ion cells were fabricated using graphitized MPCF anode and $LiCoO_2$ cathode. The voltage profiles for each half-cell in $LiCoO_2/MPCF$ cell were measured by using lithium metal as a reference electrode. Also, we evaluated the cyclic performance of $LiCoO_2/MPCF$ cells according to weight ratio. From the result of experiment $LiCoO_2$ cathode utilization was independent of weight ratio, but MPCF anode utilization was dependant on weight ratio. Also, the optimal weight ratio of $LiCoO_2/MPCF$ cell was found to be $2.0\~2.2$.

• Journal of Electrochemical Science and Technology
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• v.2 no.3
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• pp.152-156
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• 2011

A hybrid supercapacitor is fabricated using a composite material from $LiMn_2O_4$ (LMO) and activated carbon (AC) as the positive electrode and AC as the negative electrode to form the (LMO + AC)/AC system. Volume ratio (positive : negative) of electrodes is controlled to investigate of the power and energy balance. The (LMO + AC)/AC system shows better performances than the LMO/AC system. Especially, electrochemical impedance spectra, rate charge.discharge and cycle performance testing show that the (LMO + AC)/AC system have an outstanding electrochemical performance at volume ratios of (LMO + AC)/AC = 1 : 1.7 and 1 : 2. Electric double layer capacitor (EDLC) capacitance between AC of the positive electrode and AC of the negative electrode improves power density without loss of capacitance. Stable capacitance is achieved by lowering the positive electrode resistance and balancing the energy and power densities between the positive and negative electrodes by the addition of AC to the positive electrode at high current density.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.8
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• pp.587-590
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• 2013

Release competition and development of eco-friendly vehicles have been conducted violently also automaker, it will be a high growth industry of the charger and battery, which is the driving source of the motor of an electric vehicle. Reduces the on-resistance power elements DC - DC converter for battery charger for electric vehicles, must minimize switching losses. Should have a low on-resistance power than existing products. Compare the Super Junction MOSFET and Planar MOSFET, As a result, super junction MOSFET improve on about 87.4% on-state voltage drop performance than planar MOSFET.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.1775-1778
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• 2006

Through baking process on an interlayer, known as hole transporting layer, varying baking temperature up to 300 degree, which is considered as extremely high for polymer light emitting device (PLED) system, we found interesting relationship between packing density and morphology affecting device performance. Granular morphology shows that as temperature increases, grain size is getting smaller to pack closely and make interlayer harden. Such denser interlayer has temperature dependency of its own mobility, even without clear evidence of degradation of material itself. Its fact proven in a single film also reflects on multilayered PLED's performance like IVL, efficiency, lifetime. It's found that, especially, to enhance lifetime is related with thermal stability of interlayer and its mobility dependency to meet better charge balance. Therefore, it gives us understanding not only baking effect of interlayer, but also material & device designing guide to enhance lifetime.

• Transactions on Electrical and Electronic Materials
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• v.15 no.6
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• pp.333-337
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• 2014

In this study, the use of a discharging process for charged particles is proposed to achieve an ideal electrical balance or neutralization and to improve the electrical and optical properties of a reflective electronic display. Here, negatively charged particles (white) and positively charged particles (black) are used. The q/m (charge per mass for a particle) values of the black and white particles are $+4.5{\mu}C/g$ and $-4.5{\mu}C/g$, respectively. We compared the movement of the charged particles by varying their discharging time. Stable movement of the charged particles is obtained with an appropriate discharging time, which resulted in improvements of the optical properties of the panel.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.8
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• pp.711-715
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• 2007

Properties of organic light-emitting diodes (OLEDs) with aluminum-doped zinc oxide (ZnO:Al) anodes showed different behaviors from OLEDs with indium tin oxide (ITO) anodes according to driving conditions. OLEDs with ITO anodes gave higher current density and luminance in lower voltage region and better EL and power efficiency under lower current density conditions, However, OLEDs with ZnO:Al anodes gave higher current density and luminance in higher voltage region over about 8V and better EL and power efficiency under higher current density over $200mA/cm^2$. These seemed to be due to the differences in conduction properties of semiconducting ZnO:Al and metallic ITO. OLEDs with ZnO:Al anodes showed nearly saturated efficiency under high current driving conditions compared with those of OLEDs with ITO anodes. This meant better charge balance in OLEDs with ZnO:Al anodes. These properties of OLEDs with ZnO:Al anodes are useful in making bright display devices with efficiency.