• Title, Summary, Keyword: Material and Charge Balance

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Charge Balance in High Efficiency Blue Phosphorescent Organic Light Emitting Diodes

  • Chopra, Neetu;Lee, Jae-Won;So, Franky
    • 한국정보디스플레이학회:학술대회논문집
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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.

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Trends of Power Semiconductor Device (전력 반도체의 개발 동향)

  • Yun, Chong-Man
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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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.

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A study for gas distribution in separators of molten carbonate fuel cell (용융 탄산염 연료전지의 분리판 내 연료 분배 해석)

  • Park, Joonho;Cha, Suk Won
    • 한국신재생에너지학회:학술대회논문집
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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.

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A Review on Electrochemical Model for Predicting the Performance of Lithium Secondary Battery (리튬이차전지 성능 모사를 위한 전기화학적 모델링)

  • Yang, Seungwon;Kim, Nayeon;Kim, Eunsae;Lim, Minhong;Park, Joonam;Song, Jihun;Park, Sunho;Appiah, Williams Agyei;Ryou, Myung-Hyun;Lee, Yong Min
    • 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.

Selected growth of second phase on BiOBr facets via spatial charge separation towards enhanced photocatalysis activity

  • Liu, Zhiguo;Wang, Gang;Yang, Ping
    • Journal of Industrial and Engineering Chemistry
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    • v.66
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    • pp.262-268
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    • 2018
  • The recombination rate of electrons and holes determine the photocatalytic effect. Au nanoparticle (NPs) were loaded on the (110) plane of BiOBr via a ultrasonic method while $PbO_2$ NPs were loaded on the (001) plane. The ultrasound not only promoted the formation of the NPs but also resulted indirectionally transfer of electrons and holes in the different crystal planes, where electronsmainly exist in (110) planes while holes accumulate on (001) planes. Namely, ultrasonic waves caused BiOBr layer spacing to increase and destroy the balance of its built-in electric field. The loading of Au NPs enhanced the photocatalytic performance.

Effect of Cathode/anode Weight Ratio in $LiCoO_2/MPCF$ Cell ($LiCoO_2/MPCF$전지에서 정$\cdot$부극 중량비의 영향)

  • Kim Sang-Pil;Cho Jeong-Soo;Kim Hee-Je;Park Jeong-Hu;Yun Mun-Soo
    • 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 $2.0\~2.2$.

Optimization of Capacitance Balance for a Hybrid Supercapacitor Consisted of LiMn2O4/AC as a Positive and AC Negative Electrode

  • Cho, Min-Young;Park, Sun-Min;Lee, Jae-Won;Roh, Kwang-Chul
    • 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.

Study on the Design of DC-DC Converter for Super Junction MOSFET Battery Charger of Electric Vehicles (전기자동차 배터리 충전을 위한 DC - DC컨버터용 Super Junction MOSFET 설계에 관한 연구)

  • Kim, Bum June;Hong, Young Sung;Sim, Gwan Pil;Kang, Ey Goo
    • 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.

Extreme baking effect of interlayer on PLED's performance

  • Kim, Mu-Gyeom;Kim, Sang-Yeol;Lee, Tae-Woo;Park, Sang-Hun;Park, Jong-Jin;Pu, Lyong-Sun
    • 한국정보디스플레이학회:학술대회논문집
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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.

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Inverted CdSe@ZnS Quantum Dots Light-Emitting Diode using Low-Work Function Polyethylenimine Ethoxylated (PEIE) modified ZnO

  • Kim, Choong Hyo;Kim, Hong Hee;Hwang, Do Kyung;Suh, Kwang S;Park, Cheol Min;Choi, Won Kook
    • Proceedings of the Korean Vacuum Society Conference
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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]

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