• Current Photovoltaic Research
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• v.7 no.1
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• pp.9-14
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• 2019

Carrier selective solar cell structure has allured curiosity of photovoltaic researchers due to the use of wide band gap transition metal oxide (TMO). Distinctive p/n-type character, broad range of work functions (2 to 7 eV) and risk free fabrication of TMO has evolved new concept of heterojunction intrinsic thin layer (HIT) solar cell employing carrier selective layers such as $MoO_x$, $WO_x$, $V_2O_5$ and $TiO_2$ replacing the doped a-Si layers on either front side or back side. The p/n-doped hydrogenated amorphous silicon (a-Si:H) layers are deposited by Plasma-Enhanced Chemical Vapor Deposition (PECVD), which includes the flammable and toxic boron/phosphorous gas precursors. Due to this, carrier selective TMO is gaining popularity as analternative risk-free material in place of conventional a-Si:H. In this work hole selective materials such as $MoO_x$, $WO_x$ and $V_2O_5$has been investigated. Recently $MoO_x$, $WO_x$ & $V_2O_5$ hetero-structures showed conversion efficiency of 22.5%, 12.6% & 15.7% respectively at temperature below $200^{\circ}C$. In this work a concise review on few important aspects of the hole selective material solar cell such as historical developments, device structure, fabrication, factors effecting cell performance and dependency on temperature has been reported.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.3
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• pp.378-390
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• 2001

In this paper, it is analyzed that the error performance of a Multi-Carrier DS-CDMA system in a single cell with multipath Rician fading and multiple access interference (MAI) and the error performance of the system is compared with that of a Sing1e-Carrier DS-CDMA system. Moreover, the convolutional coding techniques with code rate of 1/2, 1/3, and 1/4 are adopted in order to improve the error performance degraded by the multipath fading and MAI and performance improvement through the coding techniques is analyzed. As a result, it is shown that the number of users in each system can be determined by the number of branches of the rake receiver in a Single-Carrier DS-CDMA system and the number of carriers in a Multi-Carrier DS-CDMA system. Furthermore, the convolutional coding should be chosen with considering the trade-off between coding gain and a power limitation in a Multi-Carrier DS-CDMA system. In case of increasing the number of carriers, the processing gain is decreased but the error performance is improved through the effect of frequency diversity and the system can be possibility implemented due to the low chip rate.

• Current Photovoltaic Research
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• v.6 no.2
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• pp.43-48
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• 2018

The traditional silicon heterojunction solar cells consist of intrinsic amorphous silicon to prevent recombination of the silicon surface and doped amorphous silicon to transport the photo-generated electrons and holes to the electrode. Back contact solar cells with silicon heterojunction exhibit very high open-circuit voltages, but the complexity of the process due to form the emitter and base at the backside must be addressed. In order to solve this problem, the structure, manufacturing method, and new materials enabling the carrier selective contact (CSC) solar cell capable of achieving high efficiency without using a complicated structure have recently been actively developed. CSC solar cells minimize carrier recombination on metal contacts and effectively transfer charge. The CSC structure allows very low levels of recombination current (eg, Jo < 9fA/cm2), thereby achieves high open-circuit voltage and high efficiency. This paper summarizes the core technology of CSC solar cell, which has been spotlighted as the next generation technology, and is aiming to speed up the research and development in this field.

• Journal of Power Electronics
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• v.16 no.2
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• pp.512-521
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• 2016

Cascaded H-bridge multilevel (CHBML) inverters usually include a large number of isolated dc-voltage sources. Some faults in the dc-voltage sources result in unequal cell dc voltages. Unfortunately, the conventional phase-shifted carrier (PSC) PWM method that is widely used for CHBML inverters cannot eliminate low frequency sideband harmonics when the cell dc voltages are not equal. This paper analyzes the principle of sideband harmonic elimination, and proposes an improved PSCPWM that can eliminate low frequency sideband harmonics under the condition of unequal dc voltages. In order to calculate the carrier phases, it is necessary to solve transcendental equations for low frequency sideband harmonic elimination. Therefore, an approach based on the artificial bee colony (ABC) algorithm is presented in this paper. The proposed PSCPWM method enhances the reliability of CHBML inverters. The proposed PSCPWM is not limited to CHBML inverters. It can also be applied to other types of multilevel inverters. Simulation and experimental result obtained from a prototype CHBML inverter verify the theoretical analysis and the achievements made in this paper.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.143-146
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• 2009

One of the most important issues of crystalline silicon solar cell is minimizing reflectance at the surface. Laser texturing is an isotropic process that will sculpt the surface of a silicon wafer, regardless of its crystallographic orientation. We investigated surface texturing process using Nd-YAG laser ($\lambda$=1064 nm) on multi-crystalline silicon wafer. Removal of slag formed after the laser process was performed using acid solution (HF : $HNO_3$ : $CH_3COOH$ : DI water). The reflectance and carrier lifetime of the samples were measured and analyzed using UV-Vis spectrophotometer and carrier lifetime tester. It was found that the minimum reflectance of the samples was 16.39% and maximum carrier life time was $21.8\;{\mu}s$.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.107-107
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• 2011

오늘 날 transparent conductive oxide는 다양한 분야에서 활용되고 있다. 최근에는 태양전지 분야에서도 많이 활용되고 있으며, 초기에는 transmittance 및 낮은 sheet resistance 특성을 가지는 ITO가 많이 활용되었지만 thin film solar cell와 같이 hydrogenation 공정에 약한 ITO보다는 Al-doped ZnO가 사용되기 시작하면서 많은 연구가 진행되고 있다. 본 연구에서는 thin film solar cell 및 silicon heterojunction solar cell에 적용 가능한 Al-doped ZnO에 관한 연구로써 a-Si:H의 Si-H bonds에 영향을 주지 않는 낮은 영역의 substrate temperature와 power로 Al-doped ZnO를 형성하고 상기 parameter에 따른 Al-doped ZnO의 특성 변화에 대해서 분석하였다. 특히 substrate temperature가 변화할수록 carrier concentration 및 sheet resistance가 많은 변화를 보였으며 이로 인하여 transmittance 특성이 온도에 따라 좋아지다가 너무 높은 온도에서는 오히려 좋지 않게 되었다. 이는 너무 높은 carrier concentration은 free carrier absorption에 의해 transmittance 특성을 오히려 좋지 않게 한다. 우리는 본 연구를 통해 92.677% (450 nm), 90.309% (545 nm), 94.333% (800 nm)의 transmittance를 얻을 수 있었다.

• Journal of Microbiology and Biotechnology
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• v.22 no.12
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• pp.1673-1680
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• 2012

In this study, DEAE-corncobs [delignified corncob grits derivatized with 2-(diethylamino)ethyl chloride hydrochloride ($DEAE{\cdot}HCl$)] were prepared as a carrier to immobilize yeast (Saccharomyces cerevisiae) for ethanol production. The immobilized yeast cell reactor produced ethanol under optimized $DEAE{\cdot}HCl$ derivatization and adsorption conditions between yeast cells and the DEAE-corncobs. When delignified corncob grit (3.0 g) was derivatized with 0.5M $DEAE{\cdot}HCl$, the yeast cell suspension ($OD_{600}$ = 3.0) was adsorbed at >90% of the initial cell $OD_{600}$. This amount of adsorbed yeast cells was estimated to be 5.36 mg-dry cells/g-DEAE corncobs. The $Q_{max}$ (the maximum cell adsorption by the carrier) of the DEAE-corncobs was estimated to be 25.1 (mg/g), based on a Languir model biosorption isotherm experiment. When we conducted a batch culture with medium recycling using the immobilized yeast cells, the yeast cells on DEAE-corncobs produced ethanol gradually, according to glucose consumption, without cells detaching from the DEAE-corncobs. We observed under electron microscopy that the yeast cells grew on the surface and in the holes of the DEAE-corncobs. In a future study, DEAE-corncobs and the immobilized yeast cell reactor system will contribute to bioethanol production from biomass hydrolysates.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.1
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• pp.99-108
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• 1999

In this paper, we propose $\pi$/4 QPSK scheme with block modulation algorithm, which can reduce preamble in order to transmit ATM cell efficiently in the uplink channel of LMDS, and also designed a new carrier recovery circuit which can improve carrier synchronization performance of block demodulation algorithm. The $\pi$/4 QPSK scheme employing the proposed block modulation algorithm achieved efficient frame transmission by making use of a few preamble when carrier synchronization, symbol timing synchronization and slot timing synchronization were performed by burst data of ATM cell in LMDS environment. For performance evaluation of the proposed method, a simulation analyzing the variation of carrier synchronization, symbol timing synchronization and slot timing synchronization using LMDS environment and burst mode condition was executed. In the simulation, the proposed method showed a good performance even though the reduced preamble as a few aspossible when carrier synchronization, symbol timing synchronization and slot timing synchronization is performed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.9
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• pp.1057-1063
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• 2007

To analyze the performance of mobile communication systems, the exact information of the carrier-to-interference ratio is important. Under the presence of an interferer in a cell, the carrier-to-interference ratio of the receiver is determined by the ratio between the informer-receiver distance$(d_0)$ and the receiver-interferer distance$(d_1)$. In this paper, we derive the carrier-to-interference distribution based on $d_0/d_1$ values using the geometric relation among the informer, interferer and receiver, and confirm its exactness using the simulation result. We also apply the derivation result to a system with the adjacent channel interference, and analyze the outage probability.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.6
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• pp.321-326
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• 2016

Minimizing the carrier recombination and electrical loss through surface passivation is required for high efficiency c-Si solar cell. Usually, $SiN_X$, $SiO_X$, $SiON_X$ and $AlO_X$ layers are used as passivation layer in solar cell application. Silicon oxide layer is one of the good passivation layer in Si based solar cell application. It has good selective carrier, low interface state density, good thermal stability and tunneling effect. Recently tunneling based passivation layer is used for high efficiency Si solar cell such as HIT, TOPCon and TRIEX structure. In this paper, we focused on silicon oxide grown by various the method (thermal, wet-chemical, plasma) and passivation effect in c-Si solar cell.