Identifying recombination parameters by injection-dependent lifetime spectroscopy on mc-silicon based on photoluminescence imaging

摘要

The minority carrier lifetime is a crucial material parameter in silicon (Si) wafers for use in solar cell applications, and precise measurements of carrier lifetime as a function of the excess carrier concentration (injection level) is of high importance. In this paper we present a method for extracting injection-dependent lifetime data with high spatial resolution, without the need for advanced time-resolved camera detection systems. This enables investigations of single grains, grain boundaries and structural defects in wafers with spatially non-uniform lifetime, such as high performance multicrystalline Si wafers. The local injection dependent lifetime curves are constructed from a series of photoluminescence images acquired using different steady state generation rates, carefully calibrated by a secondary quasi-steady state photoconductance measurement at a fixed light intensity. The local lifetime has been analyzed by linear parameterization of the Shockley-Read-Hall recombination model and solved for all combinations of defect parameters describing the observed recombination behavior. The recombination parameters found to dominate at high injection corresponds well with published recombination parameters due to Cr_i.