Direct Observation of Carrier Trapping Processes on Fe Impurities in mc-Si Solar Cells

Abstract

n-situ Mössbauer studies on 57Fe solute atoms in Si solar cells are performed: (1) GeV-57Mn/57Fe implantation into Si solar cells, (2) 57Fe diffused n-type Si under light illumination; (3) 57Fe diffused solar cells under applying external voltages. The carrier trapping cross sections for the interstitial components with different charge states, Fei+ and Fei2+, can be successfully obtained by evaluating the dynamical charge fluctuations within a time scale of 100ns between Fei+ and Fei2+ which appear in the Mössbauer spectra of 57Fe doped mc-Si solar cells. We further measure the distributions of Fei+ and Fei2+ by a Mössbauer Microscope, which we have been developing. The present results provide us a possibility to clarify the carrier trapping process on an atomistic scale directly on the Fe impurities in Si-solar cells.