This manuscript concerns the application of infrared birefringence imaging (IBI) to quantify macroscopic and microscopic internal stresses in multicrystalline silicon (mc-Si) solar cell materials. We review progress to date, and advance four closely related topics. (1) We present a method to decouple macroscopic thermally-induced residual stresses and microscopic bulk defect related stresses. In contrast to previous reports, thermally-induced residual stresses in wafer-sized samples are generally found to be less than 5 MPa, while defect-related stresses can be several times larger. (2) We describe the unique IR birefringence signatures, including stress magnitudes and directions, of common microdefects in mc-Si solar cell materials including: and microdefects, twin bands, nontwin grain boundaries, and dislocation bands. In certain defects, local stresses up to 40 MPa can be present. (3) We relate observed stresses to other topics of interest in solar cell manufacturing, including transition metal precipitation, wafer mechanical strength, and minority carrier lifetime. (4) We discuss the potential of IBI as a quality-control technique in industrial solar cell manufacturing.
Infrared birefringence imaging of residual stress and bulk defects in multicrystalline silicon
Vidya Ganapati, Stephan Schoenfelder, Sergio Castellanos, Sebastian Oener, Ringo Koepge, Aaron Sampson, Matthew A. Marcus, Barry Lai, Humphrey Morhenn, Giso Hahn, Joerg Bagdahn, Tonio Buonassisi; Infrared birefringence imaging of residual stress and bulk defects in multicrystalline silicon. J. Appl. Phys. 15 September 2010; 108 (6): 063528. https://doi.org/10.1063/1.3468404
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