Investigation of lifetime limiting microdefects in polycrystalline silicon for photovoltaic applications

Electron microscopy techniques were applied to the study of intragranular microdefects in as-grown and intentionally Fe contaminated polycrystalline silicon solar cell material. Electron-energy-loss spectroscopy (EELS) imaging revealed bright contrasts in metal diffused samples and with smaller concentration in as-grown material, probably due to metal precipitates. High-resolution and analytical electron microscopy identified Cu- and Fe-silicide particles in the contaminated specimen. These results demonstrate that intragranular microdefects exist in polycrystalline Si which act as nucleation sites for metal contaminants and lend support to the model that metal-decorated microdefects are decisive lifetime killers in as-grown material.