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Tang X.,Catholic University of Louvain | Tang X.,Industrial Research Ltd. | Francis L.A.,Catholic University of Louvain | Gong L.,Industrial Research Ltd. | And 7 more authors.
Solar Energy Materials and Solar Cells | Year: 2013

A new technique for the directional solidification growth of multi-crystalline silicon (mc-Si) ingot was developed by GCL-POLY Energy Holdings Ltd. This technique is called as S2 and has been used recently for industrial production. The average conversion efficiency of the solar cells fabricated by S2 mc-Si wafers is increased by 0.62% compared with the traditional mc-Si solar cells using conventional solar cell processing. In order to understand the origin of the high cell performance, ensure the process reproducibility and further improve the technique, this paper analyzes the grain structures of the S2 mc-Si wafers by light microscopy and scanning electron microscopy supported with electron back scatter diffraction. Our analysis indicates that the increased performance of the S2 mc-Si solar cells is contributed to low dislocation density, uniform and highly oriented grains with high percentage of electrically inactive grain boundary (Σ3 grain boundary). © 2013 Elsevier B.V.

Gong L.,Industrial Research Ltd. | Wang F.,Industrial Research Ltd. | Cai Q.,Industrial Research Ltd. | You D.,Jiangsu GCL Silicon Material Technology Development Co. | Dai B.,Industrial Research Ltd.
Solar Energy Materials and Solar Cells | Year: 2014

Cell efficiency distribution of mono-like silicon ingot was investigated. And a long low-efficiency tail was found in the efficiency distribution chart, which degraded the cost-effectiveness of this material. Highly spatial resolved photoluminescence and electron back-scattered diffraction characterizations of the mono-like silicon wafers were performed to investigate the low-efficiency reasons. In the experiments, we found that lots of sub-grains, invisible with naked eyes, formed by low angle grain boundaries and high density of dislocations. Relationship of low angle grain boundaries, dislocations and cell efficiency were also investigated and calculated. It is found that the density of dislocations and low angle grain boundaries increase rapidly in the directional solidification of mono-like silicon ingot. Wafers from the top side of the ingot had high density of dislocations and low angle grain boundaries, which led to low-efficiency cell performance and long low-efficiency tail distribution. © 2013 Elsevier B.V.

Zhang H.,Jiangsu GCL Silicon Material Technology Development Co. | You D.,Jiangsu GCL Silicon Material Technology Development Co. | Huang C.,Zhejiang University | Wu Y.,Jiangsu GCL Silicon Material Technology Development Co. | And 2 more authors.
Journal of Crystal Growth | Year: 2016

An effective method for ingot quality control in directional solidification by using artificially designed quartz coating as seed is demonstrated in this paper. Quartz powders sprayed at the bottom of the crucible provided numerous nucleation points for the silicon grain growth. The quartz seeded growth ingot showed a large number of small and uniform silicon grains at the bottom, although the grain size increased with crystal growth. Comparatively less dislocation agglomerates and multiplication rate through bottom to top were observed through photoluminescence (PL) analysis. Crystals produced by quartz seeded method showed a higher and more uniform minority carrier lifetime distribution compared to that produced from normal method without seed, and shorter low lifetime area length at the bottom compared to that produced from mc-Si seed-assisted growth method, indicating larger production yield under the same feedstock charging weight. An enhanced average solar cell conversion efficiency of as high as 0.52% in absolute value was obtained compared to that made from seedless method under the same cell manufacture process line, very close to that made from mc-Si seed-assisted growth method. © 2015 Elsevier B.V. All rights reserved.

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