Electronic grade Czochralski and float zone silicon in the as grown state have a very low concentration of recombination generation centers (typically <1010 cm−3). Consequently, in integrated circuit technologies using such material, electrically active inadvertent impurities and structural defects are rarely detectable. The quest for cheap photovoltaic cells has led to the use of less pure silicon, multi‐crystalline material, and low cost processing for solar applications. Cells made in this way have significant extrinsic recombination mechanisms. In this paper we review recombination involving defects and impurities in single crystal and in multi‐crystalline solar silicon. Our main techniques for this work are recombination lifetime mapping measurements using microwave detected photoconductivity decay and variants of deep level transient spectroscopy (DLTS). In particular, we use Laplace DLTS to distinguish between isolated point defects, small precipitate complexes and decorated extended defects. We compare the behavior of some common metallic contaminants in solar silicon in relation to their effect on carrier lifetime and cell efficiency. Finally, we consider the role of hydrogen passivation in relation to transition metal contaminants, grain boundaries and dislocations. We conclude that recombination via point defects can be significant but in most multi‐crystalline material the dominant recombination path is via decorated dislocation clusters within grains with little contribution to the overall recombination from grain boundaries.

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Sixty-six joules has been extracted from a 22-l active volume, 5-atm laser mixture, in a 180-ns (FWHM) optical pulse. The best efficiency obtained under these conditions was 0.8%, based on the available energy stored in the double Blumlein. For the laser chamber geometry used in this experiment it was essential that the surface track path between the positive high-voltage electrode and any ground be a minimum of 3 times the interelectrode separation. The small-signal gain under these operating conditions was 6.0% cm−1 and the measured absorption at the peak of the gain was 0.4% cm−1. We observe that for both volumetric scaling and pulse length scaling the current rise time is of critical importance.