• 신재생에너지
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• 제8권1호
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• pp.24-34
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• 2012

The main issue of boron doped p-type czochralski-grown silicon solar cells is the degradation when they are exposed to light or minority carriers injection. This is due to the meta-stable defect such as boron-oxygen in the Cz-Si material. Although a clear explanation is still researching, recent investigations have revealed that the Cz-Si defect is related with the boron and the oxygen concentration. They also revealed how these defects act a recombination centers in solar cells using density function theory (DFT) calculation. This paper reviews the physical understanding and gives an overview of the degradation models. Therefore, various methods for avoiding the light-induced degradation in Cz-Si solar cells are compared in this paper.

• 한국결정성장학회지
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• 제1권2호
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• pp.1-14
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• 1991

비균질 용융을(incongruent melting behavior)보이는 단결정제조에 있어 화학성분을 일정성분비로 유지하는 것은 매우 어렵다. $LiNbO_3$는 이러한 성질을 보이는 대표적인 예인데 넓은 고용(固溶)영역에서 일정성분비를 유지하기 힘들다 . 정밀전기/ 광학장치에 있어 이런 변수는 치명적이라 할 수 있다. 결정의 조성과 질을 결정하는 방법으로 굴절율(n)을 측정하는 광학적 방법이 수행되어 왔다. 이 방법으로 성장결정의 광학적 균질성과 화학조성을 알아낼 수 있다. 여기서는 그런 특성분석에 사용 되는 기술을 설명하고 그 결과들을 제시해 보았다

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2009년도 추계학술발표대회 논문집
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• pp.350-355
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• 2009

The crysralline silicon solar cell where the solar cell market grows rapidly is occupying of about 85% or more high efficiency and low cost endeavors many crystalline solar cells. The fabricaion process of high efficiency crystalline silicon solar cells necessitate complicated fabrication processes and Ti/Pd/AG contact, This metal contacts have only been used in limited areas in spite of their good srability and low contact resistance because of expensive materials and process. Commercial solar cells with screen-printed solar cells formed by using Ag paste suffer from loe fill factor and high contact resistance and low aspect ratio. Ni and Cu metal contacts have been formed by using electroless plating and light-induced electro plating techniques to replace the Ti/Pd/Ag and screen-printed Ag contacts. Copper and Silver can be plated by electro & light-induced plating method. Light-induced plating makes use the photovoltaic effect of solar cell to deposit the metal on the front contact. The cell is immersed into the electrolytic plating bath and irradiated at the front side by light source, which leads to a current density in the front side grid. Electroless plated Ni/ Electro&light-induced plated Cu/ Light-induced plated Ag contact solar cells result in an energy conversion efficiency of 16.446 % on 0.2~0.6${\Omega}$ cm, $20{\times}20mm^2$, CZ(Czochralski) wafer.

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1997년도 Proceedings of the 12th KACG Technical Meeting and the 4th Korea-Japan EMGS (Electronic Materials Growth Symposium)
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• pp.197-201
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• 1997

The momentum, heat and mass trasfer phenomena in the silicon melt of the Czochralki crystal growth system are calculated using a three dimensional numerical simulation thechnique. Even though axisymmetrical boundary conditions are imposed to all calculations in a 3cm diameter crucible, several types of non-axisymmetric profiles of velocities, temperature and oxygen concentration appeared in the melt. Because of the non-axisymmetric profiles of velocities, temperature and oxygen concentration appeared in the melt. Because of the non-axisymmetric profiles and rotations of fluid induced by the crucible rotation, temperatures and oxygen concentrations in the silicon melt fluctuate. The rotating velocity of the profile is calculated from the phase shift of the data of temperature or oxygen at two different points which have same radius from center but 90 degree angular difference. From this calculation, it is found that the rotating veolocity of the oxygen and temperature is different from the crucible rotation rates. Therefore the frequencies of the oscillating temperature and oxygen concentrations are not same to the frequencies of the crucible rotations. Futhermore, the components of the frequencies of the temperature and oxygen concentration at the same point are not same. The fluctuation behaviors of the temperature or oxygen themselves are also different when the points are different. The calculation show that the temperature and the oxygen concentration near the interface also fluctuate. The results suggest that the striation pattern found in the grown silicon single crystals may ben generated by the oxygen concentration and the temperature oscillations of the melt occurred near the interface.

• 한국재료학회지
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• 제22권12호
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• pp.711-716
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• 2012

Tungsten bronze structure $Sr_{1-x}Ba_xNb_2O_6$ (SBN) single crystals were grown primarily using the Czochralski method, in which several difficulties were encountered: striation formation and diameter control. Striation formation occurred mainly because of crystal rotation in an asymmetric thermal field and unsteady melt convection driven by thermal buoyancy forces. To optimize the growth conditions, bulk SBN crystals were grown in a furnace with resistance heating elements. The zone of $O_2$ atmosphere for crystal growth is 9.0 cm and the difference of temperature between the melt and the top is $70^{\circ}C$. According to the growth conditions of the rotation rate, grown SBN became either polycrystalline or composed of single crystals. In the case of as-grown $Sr_{1-x}Ba_xNb_2O_6$ (x = 0.4; 60SBN) single crystals, the color of the crystals was transparent yellowish and the growth axis was the c-axis. The facets of the crystals were of various shapes. The length and diameter of the single crystals was 50~70 mm and 5~10 mm, respectively. Tungsten bronze SBN growth is affected by the temperature profile and the atmosphere of the growing zone. The thermal expansion coefficients on heating and on cooling of the grown SBN single crystals were not matched. These coefficients were thought to influence the phase transition phenomena of SBN.

• 한국결정학회지
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• 제5권2호
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• pp.67-77
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• 1994

융액인상법으로 육성된 Y3-3xNd3xAl5O12단결정으로부터 결함을 검출하고 1)광학적 불균질상의 발생원인과 2)금속입자 함유물과 기포의 동반 발생 기구 및 3)core와 facet의 발생기구에 대해 분석하였다. 성장방향에 평행한 박 편을 제조한 후 편광현미경으로 광탄성 효과를 이용하여 결함을 분석하였으며, 결함을 etching한 후 광학적 결함 과 비교하였다. 융액유동의 변동에 의해 부분적인 고액계면의 불안정이 발생되면 부분적으로 성장속도가 크게 증가되어 편재 된 기포가 발생되었다. 반면 조성적 과냉이 발생되면 전체적으로 성장속도가 증가되어 고액계면에 평행하게 균일 분포로 기포가 발생되었다. 이때 기포 발생과 함께 고밀도로 전위가 생성되며 전위의 응력장으로 인해 광학적 불 균질상이 발생되었다. 기상의 IrO2각는 응액속에서 분해되며, 산소가 금속입자의 거친 표면에 부착되어 함께 유동 하면서 입 성장하고, 그 후 기공 또는 고액계면에 포획되는 것이 보다 가능한 금속입자 함유물 발생 기구라고 판단 되었다. Y3-3xNd3xAl5O12단결정에서 core와 facet은 정벽에 의해 발생되며, 고액계면의 접선과 성장방향 간의 각도에 영향을 받았다.

• 한국결정성장학회지
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• 제9권2호
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• pp.141-148
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• 1999

Ir 도가니에서 PbO와 $WO_{3}$를 50 %~50 % 혼합한 시료로 부터 쵸코랄스키 성장방법에 의해 고품질의 순수한 $PbWO_{4}$와 Nb 도핑한 $PbWO_{4}$를 성장 시켰다. 결정은 성분의 선택적 결손에 부합하는 화학양론적 변화는 $PbWO_{4}$의 노란색 형성에 원인이 되었다. X선 회절 실험을 통해서 각 $PbWO_{4}$ 결정의 격자상수 변화를 조사하였으며 광발광, 광흡수 및 라만 스펙트럼에 대한 특성들에 대해 조사를 하였다. 광발광은 10 K~300 K 온도 영역에서 측정 되었으며 낮은 온도 영역에서는 미흡한 온도의존성을 보였으며 200 K 온도 이상에서는 열적소광에 의한 광발광 강도의 감소를 보였다. PL 강도와 반치폭의 온도 의존성으로 부터 각 PWO 시료에 대한 활성화 에너지, Huang-Rhys 결합상수, 비균질선폭계수를 구하였다.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2009년도 춘계학술발표대회 논문집
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• pp.214-219
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• 2009

In high-efficiency crystalline silicon solar cells, If high-efficiency solar cells are to be commercialized. It is need to develop superior contact formation method and material that can be inexpensive and simple without degradation of the solar cells ability. For reason of plated metallic contact is not only high metallic purity but also inexpensive manufacture. It is available to apply mass production. Especially, Nickel, Copper and Silver are applied widely in various electronic manufactures as easily formation is available by plating. The metallic contact system of silicon solar cell must have several properties, such as low contact resistance, easy application and good adhesion. Ni is shown to be a suitable barrier to Cu diffusion as well as desirable contact metal to silicon. Nickel monosilicide(NiSi) has been suggested as a suitable silicide due to its lower resistivity, lower sintering temperature and lower layer stress than $TiSi_2$. Copper and Silver can be plated by electro & light-induced plating method. Light-induced plating makes use the photovoltaic effect of solar cell to deposite the metal on the front contact. The cell is immersed into the electrolytic plating bath and irradiated at the front side by light source, which leads to a current density in the front side grid. Electroless plated Ni/ Electro&light-induced plated Cu/ Light-induced plated Ag contact solar cells result in an energy conversion efficiency of 14.68 % on $0.2{\sim}0.6{\Omega}{\cdot}cm,\;20{\times}20mm^2$, CZ(Czochralski) wafer.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집
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• pp.62-66
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• 2002

The conventional floating zone(FZ) crystal and Czochralski(CZ) silicon crystal have resistivity variations longitudinally as well as radially The resistivity variations of the conventional FZ and CZ crystal are not conformed to requirement of dopant distribution for power devices and thyristors. These resistivity variations in conventional cystals limits the reverse breakdown voltage that could be achieved and forced designers of high power diodes and thyristors to compromise the desired current-voltage characteristics. So to produce high Power diodes and thyristors, Neutron Transmutation Doping(NTD) technique is the one method just because NTD silicon provides very homogeneous distribution of doping concentration. This procedure involves the nuclear transmutation of silicon to phosphorus by bombardment of neutron to the crystal according to the reaction $^{30}$ Si(n,${\gamma}$)longrightarrow$^{31}$ Silongrightarrow(2.6 hr)$^{31}$ P+$\beta$$^{[-10]}$ . The radioactive isotope $^{31}$ Si is formed by $^{31}$ Si capturing a neutron, which then decays into the stable $^{31}$ P isotope (i.e., the donor atom), whose distribution is not dependent on the crystal growth parameters. In this research, neutron was irradiated on FZ silicon wafers which had high resistivity(1000~2000 Ω cm), for 26 and 8.3hours for samples of HTS-1 and HTS-2, and 13, 3.2, 2.0 hours for samples of IP-1, IP-2 and IP-3, respectively, to compare resistivity changes due to time differences. The designed resistivities were approached, which were 2.l Ωcm for HTS-1, 7.21 Ω cm for HTS-2, 1.792cm for IP-1, 6.83 Ωcm for IP-2, 9.23 Ωcm for IP-3, respectively. Point defects were investigated with Deep Level Transient Spectroscopy(DLTS). Four different defects were observed at 80K, 125K, 230K, and above 300K.

• 한국세라믹학회지
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• 제39권8호
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• pp.795-800
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• 2002

융액인상법으로 질소분위기 하에서 $Yb^{3+}$ 이온이 20at% 고용된 $Yb:YCa_4O(BO_3)_3$ (Yb:YCOB) 단결정을 이리듐 도가니를 사용하여 성장시켰다. 양질의 단결정을 성장시키기 위한 인상속도와 회전속도는 각각 1.5∼2 mm/h와 10∼20 rpm이었다. 분광물성 측정 결과, 흡수단이 236 nm에 있었으며, 전형적인 $Yb^{3+}$ 이온의 흡수 스펙트럼이 관찰되었다. Yb:YCOB의 열팽창계수는 320∼650 K의 측정범위에서 결정학적 축 a, b 그리고 c에 대해 12.1×$10^{-6}$ /K, 5.9${\times}10^{-6}$/K, 12.9${\times}10^{-6}$이었다. 비열은 330 K에서 0.162 $cal/g{\cdot}K$이었다.