• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.02a
• /
• pp.163-163
• /
• 2011

박막태양전지의 가장 큰 문제점인 stablity가 우수한 조건을 찾는 연구가 많이 진행되고 있다. 그 중 i-layer는 박막태양전지의 구조 중 가장 크게 degradation이 일어나는 부분으로 알려져 왔다. 이에 i-layer 부분을 서로 특성이 다른 두 개의 막을 사용함으로써 stability를 향상시키는 방법이 제시되었는데 이 방법을 사용하는 동시에 높은 효율을 확보하기위해 이 실험을 진행하였다. i-layer의 제작 조건을 가변하여 다양한 Bandgap Energy를 가지는 단일막을 확보하였고 이를 ASA simulation을 이용해 cell에 적용하여 높은 효율을 얻고자 하였다. 결과로 i-layer Bandgap Energy를 1.8eV와 1.75eV로 쌓았을 때 최적의 효율과 electric field를 가짐을 확인할 수 있었다. 본 연구를 통해 stability 향상시킨 구조인 double i-layer 박막태양전지에서의 고효율화를 구현해 볼 수 있었다.

• Journal of the Korean Electrochemical Society
• /
• v.16 no.2
• /
• pp.65-69
• /
• 2013

In order to improve capacitance of activated carbon for electric double layer capacitors, peptide bond was induced on the surface of the activated carbon by urea. Urea induced activated carbon has been stabilized through carbonization. Electrochemical characteristics was observed by cyclic voltammetry for specific capacitance, electrochemical impedance spectroscope for measuring resistance and charge-discharge for testing the cyclic ability. In the result, specific capacitance is increased about 22.9% than the activated carbon. And it shows excellent cycle performance and decreasing resistance with the introduction of nitrogen functional groups.

• Journal of the Korean Electrochemical Society
• /
• v.10 no.4
• /
• pp.252-256
• /
• 2007

A series of spherical porous carbons were prepared via resorcinol-formaldehyde (RF) sol-gel polymerization in the presence of cationic surfactant (CTAB, cetyltrimethylammonium bromide), wherein the carbon sphere size was controlled by varying the CTAB introduction time after a pre-determined period of addition reaction (termed as "pre-curing"). The sphere size gradually decreases with an increase in the pre-curing time within the range of 30-150 nm. The carbons possess two types of pores; one inside carbon spheres (intra-particle pores) and the other at the interstitial sites made by carbon spheres (inter-particle pores). Of the two, the surface exposed on the former was dominant to determine the electric double-layer capacitor (EDLC) performance of porous carbons. As the intra-particle pores were generated inside RF gel spheres by gasification, the pore diameter was similar for all these carbons, thereby the pore length turned out to be a decisive factor controlling the EDLC performance. The charge-discharge voltage profiles and complex capacitance analysis consistently illustrate that the smaller-sized RF carbons deliver a better rate capability, which must be the direct result of facilitated ion penetration into shorter pores.

• Journal of Electrochemical Science and Technology
• /
• v.1 no.1
• /
• pp.63-68
• /
• 2010

The $Li_4Ti_5O_{12}$/AC composite was prepared by sol-gel process with ultrasonication. The prepared composite was characterized by SEM, XRD and TG analysis, and their electrochemical behaviors were investigated by cyclic voltammetry, electrochemical impedance spectroscopy and charge-discharge test in 1M $LiBF_4$/PC electrolyte. From the results, the $Li_4Ti_5O_{12}$ particles coated on AC surface had an average particle size of 100 nm and showed spinel-framework structure. When the potential range of the $Li_4Ti_5O_{12}$/AC composite was extended from 0.1 to 2.5 V, redox peaks and electric double layer property were revealed. The initial discharge capacity of $Li_4Ti_5O_{12}$/AC composite was 218 mAh $g^{-1}$ at 1 C. The enhancement of discharge capacity was attributed to electric double layer of added activated carbon.

• Korean Journal of Materials Research
• /
• v.25 no.3
• /
• pp.132-137
• /
• 2015

The effects of the mixing of an active material and a conductive additive on the electrochemical performance of an electric double layer capacitor (EDLC) electrode were investigated. Coin-type EDLC cells with an organic electrolyte were fabricated using the electrode samples with different ball-milling times for the mixing of an active material and a conductive additive. The ball-milling time had a strong influence on the electrochemical performance of the EDLC electrode. The homogeneous mixing of the active material and the conductive additive by ball-milling was very important to obtain an efficient EDLC electrode. However, an EDLC electrode with an excessive ball-milling time displayed low electrical conductivity due to the characteristic change of a conductive additive, leading to poor electrochemical performance. The mixing of an active material and a conductive additive played a crucial role in determining the electrochemical performance of EDLC electrode. The optimal ball-milling time contributed to a homogeneous mixing of an active material and a conductive additive, leading to good electrochemical performance of the EDLC electrode.

• Korean Journal of Metals and Materials
• /
• v.49 no.5
• /
• pp.419-424
• /
• 2011

Carbon nanotubes (CNTs) were directly synthesized on a copper (Cu) plate as a current collector by the catalytic thermal vapor deposition method for an electric double-layer capacitor (EDLC) electrode. The diameters of vertically aligned CNTs grown on the Cu plate were 20~30 nm. From cyclic voltammetry (CV) results, the CNTs/Cu electrode showed high specific capacitance with typical profiles of EDLCs. Rectangularshaped CV curves suggested that the CNTs/Cu electrode could be an excellent candidate for an EDLC electrode. The specific capacitances were in a range of 25~75 F/g with a scan rate of 10~100 mV/s and KOH electrolyte concentration 1~6 M, and were maintained up to 1000 charge/discharge cycles due to strong adhesion between the Cu substrate and the CNTs.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2007.08b
• /
• pp.1344-1347
• /
• 2007

We have fabricated bottom gate TFTs with active layers of amorphous/microcrystalline Si double layers (DL). Dynamic electric stresses were applied to DL TFTs and a-Si TFTs to compare their degradation characteristics. The DL TFTs were more stable under dynamic stresses than a-Si TFTs.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
• /
• 2008.10a
• /
• pp.201-204
• /
• 2008

The use of the pulsed electro acoustic (PEA) method allowed us to perform the direct observations of spatio-temporal charge distributions in Electric double layer capacitors (EDLCs) based on polarizable nanoporous carbonaceous electrode. The negative charge density became the maximum, about 205 C/$m^3$ at the region where was near to collector layer in EDLCs for case $V_{DC}$ = 2.5 V, while the positively charged density became the maximum, about 61.1 C/$m^3$ at the region where it was located around the cathode layer. The PEA measurement used here is a very useful method to quantitively investigates the spatio-temporal charge distribution in EDLCs.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.465-465
• /
• 2013

Inorganic 물질인 SiO2 dielectric 위에 organic dielectric PVP (4-vinyphenol)를 spin coating으로 올려, inorganic/organic dielectric 형태의 double layer구조로 High-performance amorphous indiumgallium zinc oxide thin-film transistors (IGZO TFT)를 제작하여 보았다. SiO2 dielectric을 buffer layer로 80 nm, PVP는 10Wt% 400 nm로 구성하였으며, 200 nm single SiO2 dielectric과 동일한 수준의 leakage current 특성을 MIM Capacitor 구조를 통해서 확인할 수 있었다. 이 소자의 장점은 용액공정의 도입으로 공정 시간의 단축 및 원가 절감을 이룰 수 있으며, dielectric과 channel 사이의 균일한 interface의 형성으로 interface trap 개선 및 Yield 향상의 장점을 갖는다. 우리는 실험을 통해서 SiO2 buffer layer가 수직 electric field에 의한 leakage current을 제어하고, PVP dielectric은 interface를 개선하는 것을 확인하였다. Vth의 negative shift 및 slope의 향상으로 구동전압이 줄어들고, 균일한 I-V Curve 형성을 통해서 Process Yield의 향상을 확인하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2002.07b
• /
• pp.1140-1143
• /
• 2002

This work describes the effect of conducting composite on the characteristics of electric double layer capacitor. The cell, which was fabricated with conducting composite consisted of 50 wt.% of SPB and 50 wt.% of VGCF, exhibits the higher specific capacitance, the lower resistance and the better rate capability than those of the cells fabricated with each single electronic conductor. These enhanced properties could be related with the dense structure of electrode.