• Current Photovoltaic Research
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• v.1 no.1
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• pp.38-43
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• 2013

$Cu(In,Ga)_3Se_5$ is a candidate material for the top cell of $Cu(In,Ga)Se_2$ tandem cells. This phase is often found at the surface of the $Cu(In,Ga)Se_2$ film during $Cu(In,Ga)Se_2$ cell fabrication, and plays a positive role in $Cu(In,Ga)Se_2$ cell performance. However, the exact properties of the $Cu(In,Ga)_3Se_5$ film have not been extensively studied yet. In this work, $Cu(In,Ga)_3Se_5$ films were fabricated on Mo-coated soda-lime glass substrates by a three-stage co-evaporation process. The Cu content in the film was controlled by varying the deposition time of each stage. X-ray diffraction and Raman spectroscopy analyses showed that, even though the stoichiometric Cu/(In+Ga) ratio is 0.25, $Cu(In,Ga)_3Se_5$ is easily formed in a wide range of Cu content as long as the Cu/(In+Ga) ratio is held below 0.5. The optical band gap of $Cu_{0.3}(In_{0.65}Ga_{0.35})_3Se_5$ composition was found to be 1.35eV. As the Cu/(In+Ga) ratio was decreased further below 0.5, the grain size became smaller and the band gap increased. Unlike the $Cu(In,Ga)Se_2$ solar cell, an external supply of Na with $Na_2S$ deposition further increased the cell efficiency of the $Cu(In,Ga)_3Se_5$ solar cell, indicating that more Na is necessary, in addition to the Na supply from the soda lime glass, to suppress deep level defects in the $Cu(In,Ga)_3Se_5$ film. The cell efficiency of $CdS/Cu(In,Ga)_3Se_5$ was improved from 8.8 to 11.2% by incorporating Na with $Na_2S$ deposition on the CIGS film. The fill factor was significantly improved by the Na incorporation, due to a decrease of deep-level defects.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.346-349
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• 2007

치밀한 $CuInSe_{2}$ (CIS) 태양전지용 광흡수층을 제조하기 위해 상용되는 출발물질을 이용하여 비진공방식인 paste coating 법으로 CIS 막을 제조하였다. 먼저 치밀한 CIS 막 제조를 위해 $Cu_{2}Se$의 액상 거동을 관찰하였다. 이러한 $Cu_{2}Se_{2}$의 액상거동을 위해 Se 분위기에서 Se 증발온도, 기판온도, 열처리시간 등을 다양하게 변화 시켰으며, Se 증발온도 $450^{\circ}C$, 기판온도 $550^{\circ}C$, 열처리시간 30분 그리고 수송가스 ($N_{2}$)를 20 sccm으로 최적조건을 형성하였다. 이러한 최적조건을 바탕으로 치밀한 CIS막을 위해 two-zone RIP (rapid temperature process) 방법으로 Se 분위기 안에서 셀렌화를 위한 열처리를 행하였다. 셀렌화를 위해 다양한 열처리시간에 따라 형성된 CIS 막은 CIS 광흡수층과 Mo 박막 사이에서 $MoSe_{2}$ 층이 형성되었지만, 균일한 CIS 막을 얻었으며 업자성장과 치밀화 거동을 관찰 하였다. 또한, CIS 막의 치밀화를 위해 Se 증발온도와 열처리시간을 고정하고 기판온도를 $600^{\circ}C$로 증가시켜 $Cu_{2}Se$의 액상거동을 관찰하였다. $600^{\circ}C$에서 형성된 CIS 막은 기판온도 $500^{\circ}C$의 시편보다 입자성장과 치밀화가 되었으나 기판으로 사용하는 soda-lime glass의 휨 현상이 발생하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.398.1-398.1
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• 2014

The $Cu_2ZnSnSe_4$ (CZTSe) thin films solar cell is one of the next generation candidates for photovoltaic materials as the absorber of thin film solar cells because it has optimal bandgap (Eg=1.0eV) and high absorption coefficient of $10^4cm^{-1}$ in the visible length region. More importantly, CZTSe consists of abundant and non-toxic elements, so researches on CZTSe thin film solar cells have been increasing significantly in recent years. CZTSe thin film has very similar structure and properties with the CIGS thin film by substituting In with Zn and Ga with Sn. In this study, As-deposited CZTSe thin films have been deposited onto soda lime glass (SLG) substrates at different deposition condition using Pulsed Laser Deposition (PLD) technique without post-annealing process. The effects of deposition conditions (deposition time, deposition temperature) onto the structural, compositional and optical properties of CZTSe thin films have been investigated, without experiencing selenization process. The XRD pattern shows that quaternary CZTSe films with a stannite single phase. The existence of (112), (204), (312), (008), (316) peaks indicates all films grew and crystallized as a stannite-type structure, which is in a good agreement with the diffraction pattern of CZTSe single crystal. All the films were observed to be polycrystalline in nature with a high (112) predominant orientation at $2{\theta}{\sim}26.8^{\circ}$. The carrier concentration, mobility, resistivity and optical band gap of CZTSe thin films depending on the deposition conditions. Average energy band gap of the CZTSe thin films is about 1.3 eV.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.158-158
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• 2011

$Cu(In_xGa_{1-x})Se_2$ (CIGS) thin film solar cell is one of the most promising solar cells in photovoltaic devices. CIGS has a direct band gap which varied from 1.0 to 1.26 eV, depending on the Ga to In ratio. Also, CIGS has been studying for an absorber in thin film solar cells due to their highest absorption coefficient which is $1{\times}10^5cm^{-1}$ and good stability for deposition process at high temperature of $450{\sim}590^{\circ}C$. Currently, the highest efficiency of CIGS thin film solar cell is approximately 20.3%, which is closely approaching to the efficiency of poly-silicon solar cell. The deposition technique is one of the most important points in preparing CIGS thin film solar cells. Among the various deposition techniques, the sputtering is known to be very effective and feasible process for mass production. In this study, CIGS thin films have been prepared by rf magnetron sputtering method using a single target. The optical and structural properties of CIGS films are generally dependent on deposition parameters. Therefore, we will explore the influence of deposition power on the properties of CIGS films and the films will be deposited by rf magnetron sputtering using CIGS single target on Mo coated soda lime glass at $500^{\circ}C$. The thickness of CIGS films will be measured by Tencor-P1 profiler. The optical properties will be measured by UV-visible spectroscopy. The crystal structure will be analyzed using X-ray diffraction (XRD). Finally the optimal deposition conditions for CIGS thin films will be developed.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.404-405
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• 2011

Cu(InGa)$Se_2$ (CIGS) 박막 태양전지의 저가 및 대면적화를 위한 양산화 공정인 two-step process (sputter/selenization) 공정에서는 sputtering으로 형성한 metal precursor stack을 $H_2$ Se gas를 이용하여 selenization하는 공정을 주로 이용한다. 하지만 이러한 selenization 공정은 유독한 $H_2$ Se gas를 이용해야 한다는 점과 긴 시간 동안 열처리를 해야 하는 단점을 가지고 있다. 이에 metal precursor stack 위에 Se 막을 우선 증착하고, Rapid Thermal Process (RTP)를 이용하여 selenization하는 방법이 현재 많은 관심을 끌고 있다. 본 논문에서는 sputtering 이후 RTP를 이용한 CIGS 흡수층 제작에 대한 선행연구의 일환으로 co-evaporator 장비를 이용하여 다양한 구조의 precursor를 제작하고 RTP 조건에 따른 selenization 효과를 연구하였다. Co-evaporator를 이용하여 CIGS, CIG/Se, CuGa/In/Se, In/CuGa/Se 4가지 구조의 precursor stack을 Mo coated soda lime glass 위에 제작하였다. 이때 amorphous 상태의 precursor stack을 만들기 위하여 기판에 열은 가하여 주지 않았으며, 각각의 stack 구조에서 가지고 있는 Cu, In, Ga, Se의 총량을 동일하게 유지하기 위하여 각 stack의 증착 시간을 동일하게 유지하였다. Selenization을 위한 RTP 조건은 550, $600^{\circ}C$ 각각에 대하여 1, 5, 10분으로 split을 진행하였다. Precursor stack의 증착 후 관찰한 XRD 결과는 비정질 상태를 잘 나타내었으며, SEM 결과 CIGS precursor stack을 제외한 나머지 구조의 stack에서는 In 박막의 surface roughness로 인하여 박막의 평탄화가 좋지 않음을 확인하였다. CIGS precursor stack의 경우, RTP 온도와 시간 split와 상관없이 결정화가 잘 이루어졌으나 grain의 성장이 부족하였다. 이에 비하여 CIG/Se, CuGa/In/Se, In/CuGa/Se 구조의 precursor stack의 경우, $550^{\circ}C$ 열처리에서는 InSe의 결정상이 관찰 되었으며 $600^{\circ}C$, 5분 이상 열처리에서 CIGS 결정상이 관찰되었다. 이러한 결과는 Se이 metal 원소들과 함께 있는 CIGS 구조에 비하여 metal precursor stack 위에 Se을 증착한 stack 구조들의 경우는 CIGS 결정을 형성하기 위해 Se이 metal 층들로 확산되어 반응을 하여야 하므로 상대적으로 많은 열에너지가 필요한 것으로 이해할 수 있으며, RTP를 이용한 selenization 공정으로 CIGS 박막 태양전지의 흡수층 형성이 가능함을 확인하였다.

• Korean Journal of Materials Research
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• v.24 no.1
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• pp.60-65
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• 2014

Fe-based amorphous coatings were fabricated on a soda-lime glass substrate by the vacuum kinetic spray method. The effect of the gas flow rate, which determines particle velocity, on the deposition behavior of the particle and microstructure of the resultant films was investigated. The as-fabricated microstructure of the film was studied by field emission scanning electron microscopy (FE-SEM) and high resolution transmission electron microscopy (HR-TEM). Although the activation energy for transformation from the amorphous phase to crystalline phase was lowered by severe plastic deformation and particle fracturing under a high strain rate, the crystalline phases could not be found in the coating layer. Incompletely fractured and small fragments 100~300 nm in size, which are smaller than initial feedstock material, were found on the coating surface and inside of the coating. Also, some pores and voids occurred between particle-particle interfaces. In the case of brittle Fe-based amorphous alloy, particles fail in fragmentation fracture mode through initiation and propagation of the numerous small cracks rather than shear fracture mode under compressive stress. It could be deduced that amorphous alloy underwent particle fracturing in a vacuum kinetic spray process. Also, it is considered that surface energy caused by the formation of new surfaces and friction energy contributed to the bonding of fragments.

• Current Photovoltaic Research
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• v.3 no.4
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• pp.130-134
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• 2015

The high efficiency cell research processes through the KF post deposition treatment (PDT) of the $Cu(In,Ga)Se_2(CIGS)$ thin film has been very actively progress. In this study, it CIGS thin film deposition process when KF PDT 300 to the processing temperature, 350, $400^{\circ}C$ changed to soda-lime glass (SLG) efficiency of the CIGS thin film characteristics, and solar cell according to Na presence of diffusion from the substrate the effects were analyzed. As a result, the lower the temperature of KF PDT and serves to interrupt the flow of current K-CIGS layer is not removed from the reaction surface, FF and photocurrent is decreased significantly. Blocking of the Na diffusion from the glass substrate is significantly increased while the optical voltage, photocurrent and FF is a low temperature (300, $350^{\circ}C$) in the greatly reduced, and in $400^{\circ}C$ tend to reduce fine. It is the presence of Na in CIGS thin film by electron-induced degradation of the microstructure of CIGS thin film is expected to have a significant impact on increasing the hole recombination rate a reaction layer is formed of the K elements in the CIGS thin film surface.

• Applied Chemistry for Engineering
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• v.16 no.6
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• pp.760-767
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• 2005

The goal of this study was to find an application method of the waste soda-lime glass as the feed material for foamed glass by foaming of hydrated waste glass. The proper conditions for the foaming of hydrated waste glass were found to be: temperature of $92.5^{\circ}C$; reaction time of 10~20 min; particle size of -325 mesh as the unhydrated glass starting materials; and graphite weight to the hydrated glass ratio of 0.003 as the foaming agent. The resulting formed glass made from hydrated mixed waste glass under above mentioned conditions had the characteristics of density less than $0.2g/cm^3$ and thermal conductivity of $0.05kcal/mh^{\circ}C$.

• Nuclear Engineering and Technology
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• v.7 no.3
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• pp.213-222
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• 1975

Immobilization of the second-cycle radioactive liquid wastes from a Purex process was developed with the blown asphalt (manufactured by Kukdong Shell Oil Company Ltd) to eliminate the possibility that the radioactive materials will be redispersed into the environment. Attempts to incorporate these wastes directly into the asphalt martrices without any pretreatment were not successful, as it was observed that the sulphuric acid in the waste oxidised the asphalt. Hence, the waste was treated with caustic soda and made alkaline prior to bituminization, so that it was found that this pretreatment made the waste compatible to the asphalt matrices. The pure blown asphalt samples irradiated with doses of 4.0$\times$10$^{7}$ rad showed no evidence of volume increase. The suitable temperature for incorporation of the alkaline wastes into blown asphalt was 180-20$0^{\circ}C$. The Products containing 50 wt% salts represented the following good properties viz., volume reduction (about 1.4), homogeneity, teachability etc. During the period of 131 day $s^{l37}$Cs from products containing 40wt% salts was leached at rates ranging from 2.70$\times$10-4 to 8.27$\times$10-4g/cm2_day but the rate for $^{90}$ Sr was lower by one to two orders of magnitude by distilled water. The leaching rates for $^{137}$ Cs and $^{90}$ Sr by sea water were slightly lower than by distilled water. Both of the leaching rates decreased with increasing pH.H.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.6
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• pp.715-721
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• 2007

Residual calcium concentration is high, in general, at the effluent of the fluoride removal process in the electronics industry manufacturing semiconductor and LCD. To increase the stability of the membrane process incorporated for reuse of wastewater, the residual calcium is required to be pre-removed. Hyperkinetic Vortex Crystallization(HVC) process was installed in the electronics industry manufecturing semi conductor as a pilot scale for accelerating calcification of calcium ion. Compared to the conventional soda ash method, the 31% higher calcium removal efficiency was achieved when HVC was applied at the same sodium carbonate dosage. In order to maintain the economic calcium removal target of 70% preset by manufacturer, the dosing concentration of the soda ash was 530 mg/L based on influent flowrate. The seed concentration in the reactor was one of the critical factors and should be maintained in the range of $800\sim1,200mg$ SS/L to maximize the calcium removal efficiency. The calcite production rate was 0.30 g SS/g $Na_2CO_3$ in the average. The economic HVC passing time of the mixture was in the range of $2\sim5$ times. Relatively, stable calcium concentration was maintained in the range of $30\sim72$ mg/L(average 49 mg/L) although the calcium concentration in the feed was severely fluctuated with $74\sim359$ mg/L(average 173 mg/L). The HVC process was characterized as environment-friendly technology reducing chemical dosage and chemical sludge production and minimizing maintenance cost.