Light-induced lifetime degradation of commercial multicrystalline silicon wafers

Abstract

Light-induced lifetime degradation of conventional cast (CAST), electromagnetic cast (EMC) and heat exchanger method (HEM) multicrystalline silicon wafers have been extensively studied. Results show that samples with lower resistivities have high normalized defect concentration compared to samples with higher resistivities due to their higher boron concentrations. Gettered samples with higher lifetimes degrade more rapidly from their initial values within the first 30 min. The normalized defect concentration has been improved by a factor of 2 indicating the effect of P-diffusion and hydrogen passivation. It is clear that the carrier lifetimes of boron-doped EMC, HEM and CAST silicon wafers degrade as CZ silicon wafers. However, EMC and cast fabricated solar cells show a slight degradation of I/sub sc/, V/sub /spl prop// and efficiencies compared to wafer lifetime degradation. The degree of lifetime degradation depends on boron content and crystal quality suggesting the boron-oxygen complex model as a mechanism for lifetime degradation.