• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.91.1-91.1
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• 2010

There are some methods for increasing efficiency of crystalline silicon solar cells. Among them, It is important to reduce the recombination loss of surface for high efficiency. In order to reduce recombination loss is a way to use the BSF(Back Surface Field). The BSF on the back of the p-type wafer forms a p+layer. so, it is prevented to act electrons of the p-area for the rear recombination. As a result, the leakage current is reduced and the rear-contact has a good Ohmic contact. therefore, open-circuit-voltage and Fill factor(FF) of solar cells are increased. This paper investigates the formation of rear contact process comparing Aluminum-paste(Al-paste) with Aluminum-Metal(99.9%). It is shown that the Aluminum-Metal provides high conductivity and low contact resistance of $21.35m{\Omega}cm$ using the Vacuum evaporation process but, it is difficult to apply the standard industrial process because high Vacuum is needed and it costs a tremendous amount more than Al-paste. On the other hand, using the Al-paste process by screen printing is simple for formation of metal contact and it is possible to produce the standard industrial process. however, it is lower than Aluminum-Metal(99.9) of conductivity because of including mass glass frit. In this study, contact resistances were measured by 4-point prove. each of contact resistances is $21.35m{\Omega}cm$ of Aluminum-Metal and $0.69m{\Omega}cm$ of Al-paste. and then rear contact have been analyzed by Scanning Electron Microscopy(SEM).

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.53.2-53.2
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• 2010

In this study, we focused on our specialized electrode process for Si back-contact crystalline solar cell. It is different from other well-known back-contact cell process for thermal aspect and specialized process. In general, aluminum makes ohmic contact to the Si wafer and acts as a back surface reflector. And, silver is used for low series resistance metal grid lines. Aluminum was sputtered onto back side of wafer. Next, silver is directly patterned on the wafer by screen printing. The sputtered aluminum was removed by wet etching process after rear silver electrode was formed. In this process, the silver paste must have good printability, electrical property and adhesion strength, before and after the aluminum etching process. Silver paste also needs low temperature firing characteristics to reduce the thermal budget. So it was seriously collected by the products of several company of regarding low temperature firing (below $250^{\circ}C$) and aluminum etching endurance. First of all, silver pastes for etching selectivity were selected to evaluate as low temperature firing condition, electrical properties and adhesive strength. Using the nano- and micron-sized silver paste, so called hybrid type, made low temperature firing. So we could minimize the thermal budget in metallization process. Also the adhesion property greatly depended on the composition of paste, especially added resin and inorganic additives. In this paper, we will show that the metallization process of back-contact solar cell was realized as optimized nano-paste characteristics.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.39.2-39.2
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• 2010

In this work we have investigated electrical and optical properties of interface for ITO/Si with shallow doped emitter. The ITO is prepared by DC magnetron sputter on p-type monocrystalline silicon substrate. As an experimental result, The transmittance at 640nm spectra is obtained an average transmittance over 85% in the visible range of the optical spectrum. The energy bandgap of ITO at oxygen flow from 0% to 4% obtained between 3.57eV and 3.68eV (ITO : 3.75eV). The energy bandgap of ITO is depending on the thickness, sturcture and doping concentration. Because the bandgap and position of absorption edge for degenerated semiconductor oxide are determined by two competing mechanism; i) bandgap narrowing due to electron-electron and electron-impurity effects on the valance and conduction bands (> 3.38eV), ii) bandgap widening by the Burstein-Moss effect, a blocking of the lowest states of the conduction band by excess electrons( < 4.15eV). The resistivity of ITO layer obtained about $6{\times}10^{-4}{\Omega}cm$ at 4% of oxygen flow. In case of decrease resistivity of ITO, the carrier concentration and carrier mobility of ITO film will be increased. The contact resistance of ITO/Si with shallow doped emitter was measured by the transmission line method(TLM). As an experimental result, the contact resistance was obtained $0.0705{\Omega}cm^2$ at 2% oxygen flow. It is formed ohmic-contact of interface ITO/Si substrate. The emitter series resistance of ITO/Si with shallow doped emitter was obtained $0.1821{\Omega}cm^2$. Therefore, As an PC1D simulation result, the fill factor of EWT solar cell obtained above 80%. The details will be presented in conference.

• Applied Chemistry for Engineering
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• v.31 no.1
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• pp.25-29
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• 2020

In this study, a polymer/graphene hybrid composite was prepared by a simple roll-method and a simple sensor was produced by a convenient surface engineering procedure. The sensor performance was examined and the effect of graphene content on the sensing behavior was monitored. A polymer (polydimethylsiloxane, PDMS) paste containing graphene powder was prepared by a three-roll apparatus and polymer/graphene hybrid composite was produced by a two-roll technique. The sensing medium, cyclodextrin (CD) was introduced by a convenient bio-conjugation method. The efficacy of surface modification was confirmed by FT-IR spectroscopy and the ohmic relation was observed on composite surfaces. An analyte (e.g., methyl paraben, MePRB) at a 10 nM concnetration could be detected. When the graphene loading was low, the sensor performance was relatively poor. This was attributed to the absence of graphene alignments, which were observed for the composites having a high graphene loading. This indicates that the sensor performance was influenced by physical alignments of the filler. This article can provide important information for future research on developing sensing devices.

• Current Photovoltaic Research
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• v.8 no.3
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• pp.102-106
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• 2020

In this paper, the effect of MoSe₂ on the contact resistance (R_C) of the transparent conducting oxide (TCO) and Mo junction in the scribed P2 region of the Cu(In,Ga)Se₂ (CIGS) solar module was analyzed. The CIGS/Mo junction becomes ohmic-contact by MoSe₂, so the formation of the MoSe₂ layer is essential. However, the CIGS solar module has a TCO/MoSe₂/Mo junction in the P2 region due to structural differences from the cell. The contact resistance (R_C) of the P2 region was calculated using the transmission line method, and MoSe₂ was confirmed to increase R_C of the TCO/Mo junction. B doped ZnO (BZO) was used as TCO, and when BZO/MoSe₂ junction was formed, conduction band offset (CBO) of 0.6 eV was generated due to the difference in their electron affinities. It is expected that this CBO acts as a carrier transport barrier that disturbs the flow of current, resulting in increased R_C. In order to reduce the R_C caused by CBO, MoSe₂ must be made thin in a CIGS solar module.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.2
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• pp.212-216
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• 1999

SiC(3C) photodiodes (PDs) were fabricated on p-type Si(111) substrates using chemical vapor deposition (CVD) technique by pyrolyzing tetramethylsilane (TMS) with $H_{2}$ carrier gas. Electrical properties of SiC(3C) were investigated by Hall measurement and current-voltage (I-V) characteristics. SiC(3C) layers exhibited n-type conductivity. Ohmic contact was formed by thermal evaporation Al metal through a shadow-mask. The optical gain $(G_{op})$ of the SiC(3C)/Si PD was measured as a function of the incident wavelength. For the analysis of the photovoltaic detection of the Sic(3C) n/p PD, the spectral response (SR) has calculated by using the electrical parameters of the SiC(3C) layer and the geometric structure of the PD. The peak response calculated for properly chosen parameters was about 0.75 near 550 nm. We expect a good photoresponse in the SiC(3C) heterostructure for the wavelength range of 400~600 nm. The SiC(3C) photodiode can detect blue and near ultraviolet (UV) radiation.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.426.2-426.2
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• 2016

Numerous of researches are being conducted to improve the efficiency of $Cu_2ZnSnSe_4$ (CZTSe)-based photovoltaic devices, which is one of the most promising candidates for low cost and environment-friendly solar cells. In this work, we concentrate on the back contact of the devices. A proper thickness of $MoSe_2$ in back contact structure is believed to enhance adhesion and ohmic contact between Mo back contact and absorber layer. Nevertheless, too thick $MoSe_2$ layers that are grown during high-temperature selenization process can impede the current collection, thus resulting in low cell performance. By applying molybdenum nitride as a barrier in back contact structure, we were able to control the thickness of $MoSe_2$ layer, which resulted in lower series resistance and higher fill factor of CZTSe devices. The phase transformation of Mo-N binary system was systematically studied by changing $N_2$ concentration during the sputtering process. With a proper phase of Mo-N fabricated by using an adequate partial pressure of $N_2$, the efficiency of CZTSe solar cells as high as 8.31% was achieved while the average efficiency was improved by about 2% with respect to that of the referent cells where no barrier layer was employed.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.11a
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• pp.5.1-5.1
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• 2009

Organic photovoltaic (OPV)cells have attracted considerable attention due to their potential for flexible, lightweight, and low-cost application of solar energy conversion. Since a 1% power conversion efficiency (PCE) OPV based on a single donor-acceptor heterojunction was reported by Tang, the PCE has steadily improved around 5%. It is well known that a high parallel (shunt)resistance and a low series resistance are required simultaneously to achieve ideal photovoltaic devices. The device should be free of leakage current through the device to maximize the parallel resistance. The series resistance is attributed to the ohmic loss in the whole device, which includes the bulk resistance and the contact resistance. The bulk resistance originated from the bulk resistance of the organic layer and the electrodes; the contact resistance comes from the interface between the electrodes and the active layer. Furthermore, it has been reported that the bulk resistance of the indium tin oxide (ITO) of the devices dominates the series resistance of OPVs for a large area more than $0.01\;cm^2$. Therefore, in practical application, the large area of ITO may significantly reduce the device performance. In this work, we investigated the effect of sheet resistance ($R_{sh}$) of deposited ITO on the performance of OPVs. It was found that the device performance of polythiophene-fullerene (P3HT:PCBM) bulk heterojunction OPVs was critically dependent on Rsh of the ITO electrode. With decreasing $R_{sh}$ of the ITO from 39 to $8.5\;{\Omega}/{\square}$, the fill factor (FF) of OPVs was dramatically improved from 0.407 to 0.580, resulting in improvement of PCE from $1.63{\pm}0.2$ to $2.5{\pm}0.1%$ underan AM1.5 simulated solar intensity of $100\;mW/cm^2$.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.3
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• pp.41-47
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• 1999

Ion implanted GaAs MESFET with low resistive layer was fabricated using Si diffusion into GaAs from SiN. During the thermal annealing at 95$0^{\circ}C$ for 30s, Si diffused into ion implanted region of GaAs from SiN and they formed low resistive layer of 350$\AA$ thickness. The diffusion of Si decreased the sheet resistance of source and drain region from 1000$\Omega$/sq. to 400$\Omega$/sq. and the AuGe/Ni/Au ohmic contact resitivity from 2.5$\times$10sub -6$\Omega$-cmsup 2 to $1.5\times$10sup -6$\Omega$-cmsup 2. The fabricated lum gate length MESFET with Si diffused surface layer shows the transconductance of 360ms/mm, 8.5dB of associated gain and 3.57dB of minimum noise figure at 12GHz. These performances are better than that of MESFET without Si diffused layer.

• JSTS:Journal of Semiconductor Technology and Science
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• v.15 no.1
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• pp.41-47
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• 2015

In this paper, the effective electron Schottky barrier height (${\Phi}_{Bn}$) of the Ni silicide/n-silicon (100) interface was studied in accordance with different thicknesses of the antimony (Sb) interlayer for high performance n-channel MOSFETs. The Sb interlayers, varying its thickness from 2 nm to 10 nm, were deposited by radio frequency (RF) sputtering on lightly doped n-type Si (100), followed by the in situ deposition of Ni/TiN (15/10 nm). It is found that the sample with a thicker Sb interlayer shows stronger ohmic characteristics than the control sample without the Sb interlayer. These results show that the effective ${\Phi}_{Bn}$ is considerably lowered by the influence of the Sb interlayer. However, the current level difference between Schottky diodes fabricated with Sb/Ni/TiN (8/15/10 nm) and Sb/Ni/TiN (10/15/10 nm) structures is almost same. Therefore, considering the process time and cost, it can be said that the optimal thickness of the Sb interlayer is 8 nm. The effective ${\Phi}_{Bn}$ of 0.076 eV was achieved for the Schottky diode with Sb/Ni/TiN (8/15/10 nm) structure. Therefore, this technology is suitable for high performance n-channel MOSFETs.