Mass-production of high quality polycrystalline silicon sheets by the new spin cast process

Abstract

A novel spin-cast process to produce high-quality polycrystalline silicon sheets for low-cost solar cells has been developed, and the equipment for mass production has been constructed. High-quality silicon sheets, 10 cm*10 cm and 0.4 mm thick, were produced at a production rate of 15 s/sheet using this process. The best solar cell efficiency achieved was 13.2% (10*10 cm, AM 1.5, 100 mW/cm/sup 2/). In a previous process, silicon sheets were formed in the cavity of the mold modules using the centrifugal force effect of the spin-cast zone. The crystals were formed while the mold modules were spinning. In order to obtain a higher production rate, a higher crystal growth rate was necessary. A higher growth rate, however, generally results in an increase in crystal defects and stresses. The goals of high production rate and high quality seemed to be in direct opposition. The new spin cast process and the equipment for mass production were constructed to solve this problem. >