Si samples produced by float-zoning (FZ) with controlled
levels of crystallographic defects were used to study effects on minority
charge-carrier lifetime and PV cell efficiency.
We have published studies on a wide
range of defects, including grain boundaries (see the examples shown at the
right), dislocations, Si self-interstitials, and vacancies.
The improved understanding
of defect control has allowed us to produce FZ crystals with record lifetimes > 20
have yielded solar cells with 22% efficiency.
Ciszek and T.H. Wang, “Silicon Defect and Impurity Studies Using
Float-Zone Crystal Growth as a Tool,” J. of Crystal Growth, 237-239
(P3) (2002) pp. 1685-1691.
T.F. Ciszek, Tihu Wang, and T. Schuyler, "Some Effects of
Crystal Growth Parameters on Minority Carrier Lifetime in Float-Zoned
Silicon," J. Electrochem. Soc. 136 (1989) 230