• Journal of Electrical Engineering and information Science
• /
• 제2권5호
• /
• pp.65-71
• /
• 1997

We present heterojunction solar cells with a structure of metal/a-Si:H(n-i-p)/poly-Si(n-p)/metal for the terrestrial applications. This cell consists fo two component cells: a top n-i-p junction a-Si:Hi cell with wide-bandgap 1.8eV and a bottom n-p junction poly-Si cell with narrow-bandgap 1.1eV. The efficiency influencing factors of the solar cell were investigated in terms of simulation an experiment. Three main topics of the investigated study were the bottom cell with n-p junction poly-Si, the top a-Si:H cell with n-i-p junction, and the interface layer effects of heterojunction cell. The efficiency of bottom cell was improved with a pretreatment temperature of 900$^{\circ}C$, surface polishing, emitter thickness of 0.43$\mu\textrm{m}$, top Yb metal, and grid finger shading of 7% coverage. The process optimized cell showed a conversion efficiency about 16%. Top cell was grown by suing a photo-CVD system which gave an ion damage free and good p/i-a-Si:H layer interface. The heterojunction interface effect was examined with three different surface states; a chemical passivation, thermal oxide passivation, and Yb metal. the oxide passivated cell exhibited the higher photocurrent generation and better spectral response.

• 대한금속재료학회지
• /
• 제49권7호
• /
• pp.583-588
• /
• 2011

$Cd_xZn_{1-x}O$ thin films were grown on quartz substrates by using the sol-gel spin-coating method. The mole fraction, x, of the $Cd_xZn_{1-x}O$ thin films was controlled from 0 to 1 by changes in the content ratio of the cadmium acetate dehydrate [$Cd{(CH_3COO)}_2{\cdot}2H_2O$] and zinc acetate dehydrate [$Zn{(CH_3COO)}_2{\cdot}2H_2O$]. The effects of the mole fraction on the morphological, structural, and optical properties of the $Cd_xZn_{1-x}O$ thin films were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), and UV-visible spectroscopy. The $Cd_xZn_{1-x}O$ thin films exhibited the polygonal surface morphology and their grain size was increased ranging from 42.1 to 63.9 nm with the increase in the mole fraction. It was observed that the absorption bandgap of the $Cd_xZn_{1-x}O$ thin films decreased from 3.25 to 2.16 eV as the mole fraction increased and the Urbach energy ($E_U$) values changed inversely to the optical bandgap of the $Cd_xZn_{1-x}O$ thin films.

• 전기학회논문지
• /
• 제67권10호
• /
• pp.1370-1374
• /
• 2018

A heterojunction $SnS_2/p-Si$ photodetector was fabricated by RF magnetron sputtering system. $SnS_2$ was formed with 2-inch $SnS_2$ target. Al was applied as the front and the back metal contacts. Rapid thermal process was conducted at $500^{\circ}C$ to enhance the contact quality. 2D material such as $SnS_2$, MoS2 is very attractive in various fields such as field effect transistors (FET), photovoltaic fields such as photovoltaic devices, optical sensors and gas sensors. 2D material can play a significant role in the development of high performance sensors, especially due to the advantages of large surface area, nanoscale thickness and easy surface treatment. Especially, $SnS_2$ has a indirect bandgap in the single and bulk states and its value is 2 eV-2.6 eV which is considerably larger than that of the other 2D material. The large bandgap of $SnS_2$ offers the advantage for the large on-off current ratio and low leakage current. The $SnS_2/p-Si$ photodetector clearly shows the current rectification when the thickness of $SnS_2$ is 80 nm compared to when it is 135 nm. The highest photocurrent is $19.73{\mu}A$ at the wavelength of 740 nm with $SnS_2$ thickness of 80 nm. The combination of 2D materials with Si may enhance the Si photoelectric device performance with controlling the thickness of 2D layer.

• 한국전자파학회논문지
• /
• 제10권5호
• /
• pp.694-700
• /
• 1999

본 논문에서는 마이크로스트립 구조에서의 접지변에 식각된 패턴을 갖는 PBG(Photonic Bandgap) 구조의 S Slow-wave 특성을 이용한 전력 분배기 설계에 대해 연구하였다. 또한 제시된 PBG 구조는 전송선로의 특성 임피던스를 변화시켜 기존 구조에 비해 선로의 폭을 넓게 할 수 있고 Slow-wave 특성에 의해 소자의 크기가 감소된 Wilkinson 3 dB 전력 분배기를 설계하였다. 제시된 임의의 PBG 구조를 산란 파라미터로부터 전송선로의 특성 임피던스와 전기적 길이를 추출하여 응 용하는 방법을 제시하였고 같은 모양의 결손(defect)을 추가함으로써 그 영향을 고찰하였다. 제시된 방법으로 구현된 전력분배기의 측정 결과는 시율레이션 결과와 잘 일치함을 보였다.

• ETRI Journal
• /
• 제32권2호
• /
• pp.265-272
• /
• 2010

To supply a power distribution network with stable power in a high-speed mixed mode system, simultaneous switching noise caused at the multilayer PCB and package structures needs to be sufficiently suppressed. The uni-planar compact electromagnetic bandgap (UC-EBG) structure is well known as a promising solution to suppress the power noise and isolate noise-sensitive analog/RF circuits from a noisy digital circuit. However, a typical UC-EBG structure has several severe problems, such as a limitation in the stop band's lower cutoff frequency and signal quality degradation. To make up for the defects of a conventional EBG structure, a partially located EBG structure with decoupling capacitors is proposed in this paper as a means of both suppressing the power noise propagation and minimizing the effects of the perforated reference plane on the signal quality. The proposed structure is validated and investigated through simulation and measurement in both frequency and time domains.

• 한국전기전자재료학회논문지
• /
• 제24권7호
• /
• pp.584-588
• /
• 2011

The ZnO thin films doped with Ga and Ge (GZO:Ge) were prepared on glass substrate using RF sputtering system. Structural, morphological and optical properties of the films deposited in different temperatures were studied. Proportion of the element of using target was 97 wt% ZnO, 2.5 wt% Ga and 0.5 wt% Ge with 99.99% highly purity. Structural properties of the samples deposited in different temperatures with 200 w RF power were investigated by field emission scanning electron microscopy, FE-SEM images and x-ray diffraction XRD analysis. Atomic force microscopy, AFM images were able to show the grain scales and surface roughness of each film rather clearly than SEM images. it was showed that increasing temperature have better surface smoothness by FE-SEM and AFM images. Transmittance study using UV-Vis spectrometer showed that all the samples have highly transparent in visible region (300~800 nm). In addition, it can be able to calculate bandgap energy from absorbance data obtained with transmittance. The hall resistivity, mobility, and optical band gap energy are influenced by the temperature.

• 한국전기전자재료학회논문지
• /
• 제30권2호
• /
• pp.115-118
• /
• 2017

Highly photosensitive and wide bandgap amorphous silicon oxide (a-$SiO_x$:H) films were developed at low temperature ranges ($100{\sim}150^{\circ}C$) with employing plasma-enhanced chemical vapor deposition by optimizing $H_2/SiH_4$ gas ratio and $CO_2$ flow. Photosensitivity more than $10^5$ and wide bandgap (1.81~1.85 eV) properties were used for making the a-$SiO_x$:H thin film solar cells, which exhibited a high open circuit voltage of 0.987 V at the substrate temperature of $100^{\circ}C$. In addition, a power conversion efficiency of 6.87% for the cell could be improved up to 7.77% by employing a new n-type nc-$SiO_x$:H/ZnO:Al/Ag triple back-reflector that offers better short circuit currents in the thin film photovoltaic devices.

• Environmental Engineering Research
• /
• 제24권4호
• /
• pp.566-571
• /
• 2019

One-pot hydrothermal route was adopted to synthesize Al:BiVO₄, at 4 h and 8 h reaction durations, by adding 1% aluminiumoxide powder (w/v) to the precursors. The products were investigated using several characterization techniques that conform a significant morphological change and a decrease in bandgap energy of the materials upon Al modification of scheelite monoclinic bismuth vanadate matrix at both hydrothermal durations. Antibacterial experiments were performed against methicillin-resistant Staphylococcus aureus in visible light condition to harness the photoxidation property of Al-doped BiVO₄ and compare to that of unaltered BiVO₄. Minimum inhibitory concentration of the synthesized materials was identified. The results indicate that Al-doping on BiVO₄ has a significant effect on its photocatalytic antibacterial performance. Al:BiVO₄ synthesized at 8 h hydrothermal treatment parades excellent sunlight-driven photocatalysis compared to the one synthesized at 4 h.

• 한국전기전자재료학회논문지
• /
• 제27권11호
• /
• pp.760-765
• /
• 2014

MgZnO has attracted a lot of attention for flexible device. In the flexible substrate, the crystal structure of the thin films as well as the surface morphology is not good. Therefore, in this study, we studied on the effects of the oxygen pressure on the structure and crystallinity of $Mg_{0.3}Zn_{0.7}O$ thin films deposited on PES substrate by using pulsed laser deposition. We used X-ray diffraction and atomic force microscopy in order to observe the structural characteristics of $Mg_{0.3}Zn_{0.7}O$ thin films. The crystallinity of $Mg_{0.3}Zn_{0.7}O$ thin films with increasing temperature was improved, Grain size and RMS of the films were increased. UV-visible spectrophotometer was used to get the band gap energy and transmittance. $Mg_{0.3}Zn_{0.7}O$ thin films showed high transmittance over 90% in the visible region. As increased working pressure from 30 mTorr to 200 mTorr, the bandgap energy of $Mg_{0.3}Zn_{0.7}O$ thin film were decreased from 3.59 eV to 3.50 eV.

• 대한전자공학회논문지TC
• /
• 제38권12호
• /
• pp.39-48
• /
• 2001

본 논문에서는 마이크로스트립 라인에 포토닉 밴드갭(photonic bandgap: PBG) 구조를 구현할 경우 저지대역 내에 형성되는 통과대역의 부분대역폭(fractional bandwidth)을 효과적으로 조절할 수 있는 PBG 구조의 설계에 관하여 연구하였다. 이 구조는 결함을 갖는 통상적 PSG 구조의 기본 PSG 셀(cell)에 스텁(stub)을 더하여 구현한 것으로 PBG 셀에 첨가된 스텁 길이가 증가함에 따라 스컷(skirt) 특성이 현저하게 개선됨을 볼 수 있었다. 이때 차단주파수(cutoff- frequency), 저지대역 및 통과대역의 중심주피수는 저주파 쪽으로 이동하였고 통과대역폭은 감소하였다. 이러한 결과는 PBG 셀에 스텁을 활용함으로써 저지대역 내에 형성되는 통과대역의 부분대역폭을 효과적으로 조절할 수 있음을 보여준다. 또한 스텁을 갖는 PBG 구조를 응용하여 우수한 스컷 특성을 갖는 듀플렉서를 설계할 수 있음도 보였다.