Thin silicon String Ribbon for high efficiency polycrystalline solar cells

Abstract

Silicon ribbon of 100 /spl mu/m thickness has been grown using the String Ribbon crystal growth method. Flat, low stress material has been grown using both a tunable active afterheater and a simplified passive afterheater. The material is polycrystalline, with grain size as large as 2 cm across. Research sized cells (1 cm/sup 2/) of over 15% efficiency have been made on this material. Effects of forming gas anneal, Al back contact thickness and BSF, and PECVD SiN/MgF/sub 2/ vs. ZnS/MgF/sub 2/ were studied as a function of efficiency. The internal quantum efficiency (IQE) of the cells shows an unusually high sensitivity to light bias. Further optimization is expected to lead to 16% cells in the near future.