The Fabrication of Large-Area Upgraded Metallurgical Grade Multi-Crystalline Silicon Solar Cells in a Production Line

Abstract

Upgraded metallurgical grade (UMG) silicon has been researched both on the purification methods and its material properties for years, indicating that it is the most promising choice as low-cost feedstock for photovoltaics. In this work, UMG multi-crystalline silicon (mc-Si) prepared by cold crucible refining and electron beam melting was investigated. Solar cells based on such silicon wafers were fabricated in a 156 x 156 mm2 production line and their photovoltaic properties were characterized. Compared with the conventional mc-Si solar cells fabricated in the same commercial production line, the UMG mc-Si solar cells with two busbars presented higher average open circuit voltage (Voc) and average fill factor (FF), which were 628 mV and 78.6 % separately. Although the UMG mc-Si solar cells showed a lower shot-circuit current density (Jsc) of 32.7 A/cm2 in the average and an early reverse breakdown voltage at around 11 V which was due to higher impurities content. The average conversion efficiency of the UMG mc-Si solar cells reached 16.14 %, and the highest conversion efficiency was up to 16.31 %. In addition, the UMG mc-Si solar cells presented relatively low light induced degradation (LID) due to the material properties. Consequently, in consideration of low cost, our UMG mc-Si solar cells substantially met the requirements of commercial manufacturing and had a great potential application for photovoltaic industry.