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Yang Y.M.,Sino American Silicon Productions Inc. | Yu A.,Sino American Silicon Productions Inc. | Hsu B.,Sino American Silicon Productions Inc. | Hsu W.C.,Sino American Silicon Productions Inc. | And 2 more authors.
Progress in Photovoltaics: Research and Applications

The low cost and high quality of multicrystalline silicon (mc-Si) based on directional solidification has become the main stream in photovoltaic (PV) industry. The mc-Si quality affects directly the conversion efficiency of solar cells, and thus, it is crucial to the cost of PV electricity. With the breakthrough of crystal growth technology, the so-called high-performance mc-Si has increased about 1% in solar cell efficiency from 16.6% in 2011 to 17.6% in 2012 based on the whole ingot performance. In this paper, we report our development of this high-performance mc-Si. The key ideas behind this technology for defect control are discussed. With the high-performance mc-Si, we have achieved an average efficiency of near 17.8% and an open-circuit voltage (Voc) of 633mV in production. The distribution of cell efficiency was rather narrow, and low-efficiency cells (<17%) were also very few. The power of the 60-cell module using the high-efficiency cells could reach 261 W as well. Copyright © 2013 John Wiley & Sons, Ltd. Source

Li T.F.,National Taiwan University | Yeh K.M.,National Taiwan University | Hsu W.C.,Sino American Silicon Productions Inc. | Lan C.W.,National Taiwan University | Lan C.W.,Industrial Technology Research Institute of Taiwan
Journal of Crystal Growth

We report on an idea for grain control during directional solidification using a crucible with notches at the bottom for mc-Si solar materials. It was observed that with a proper notch size, the initial grain competition could be controlled with a proper cooling rate. The notch could enlarge the grains induced by the spot cooling method and the grains became dominant at the later stage of solidification. Furthermore, the crystals grown from the notch showed a higher minority carrier lifetime and a larger area of twins, with a much lower dislocation density as well. The electron back scattered diffraction (EBSD) analysis for the controlled crystals further indicated that the region near the notch had almost the same {1 1 2} orientation from the notch. The proposed method can be easily implemented in commercial ingot production. © 2010 Published by Elsevier B.V. All rights reserved. Source

Wong Y.T.,National Taiwan University | Hsu C.,Sino American Silicon Productions Inc. | Lan C.W.,National Taiwan University
Journal of Crystal Growth

Development of grain structures of multi-crystalline silicon from small spherical seeds with random orientations in directional solidification was investigated. The electron backscattered diffraction (EBSD) analyses of the grains at different pulling rates, i.e., 1, 5, and 20 cm/h, were carried out. It was found that {112}/{111} orientations were dominant at the low crucible pulling speed, while {111} at the high pulling speeds. The percentage of {100} grains was found very low near the top of the ingots. The percentage of non-Σ grain boundaries was around 70% at the beginning and decreased with the solidification distance, while Σ3 grain boundaries or twins increased indicating the importance of twin formation during the development of grain structures. The mechanisms for grain competition and selection were further discussed. © 2013 Elsevier B.V. Source

Yeh K.M.,National Taiwan University | Hseih C.K.,Sino American Silicon Productions Inc. | Hsu W.C.,Sino American Silicon Productions Inc. | Lan C.W.,National Taiwan University | Lan C.W.,Industrial Technology Research Institute of Taiwan
Progress in Photovoltaics: Research and Applications

We report simple ideas for grain control by using active cooling and crucible insulation for high-quality multi-crystalline silicon (mc-Si) growth for solar cells. The method employed an active cooling spot to induce initial dendrite growth, and the solidification front was controlled to be slightly convex through crucible insulation. It was found that the percentage of grains having twins was significantly increased by the present approach. The dislocation density for those grains was also significantly lower. More importantly, the successful improvement showed that the grain size and the minority carrier lifetime increased along the growth direction. And the laser beam induced current (LBIC) measurement also showed muchhigher quantum efficiency for the twin area. Copyright © 2010 John Wiley & Sons, Ltd. Source

Lan C.W.,National Taiwan University | Lan W.C.,Sino American Silicon Productions Inc. | Lee T.F.,National Taiwan University | Yu A.,Sino American Silicon Productions Inc. | And 4 more authors.
Journal of Crystal Growth

Directional solidification (DS) has become the major process for growing multi-crystalline silicon (mc-Si) for solar cells in the photovoltaic industry. The control of grains, as well as the grain boundaries, is particularly important to the crystal quality, and thus the solar cell efficiency. In this paper, we review the progress in the grain control of DS mc-Si from lab-scale to industrial-scale experiments. The control of the growth front was found effective in improving the grain size, but the grain size was found decreased with growth due to the sub-grain formation. With a better control of nucleation and grain competition by increasing the undercooling through enhanced uniform or spot cooling, grains with more Σ3 or twin boundaries were obtained. As the grain size increased with height, the growth of dislocations was found much slower than that without grain growth. The conversion efficiency of the solar cells fabricated from the wafers with grain control was significantly improved. Moreover, the seeded growth was also discussed. © 2012 Elsevier B.V. Source

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