Evaluation of Process Damage Induced by Sputtering of Transparent Conductive Oxide Films for Crystalline Silicon Solar Cells

Abstract

We evaluated the damage to crystalline silicon caused by sputtering deposition of transparent conductive oxide films (TCO). We confirmed that direct deposition of TCO on the crystalline silicon deteriorates the carrier lifetime. Also, the difference in discharge voltage during the TCO sputtering has an influence on plasma damage and damage penetration depth to the crystalline silicon. We consider that the carrier lifetime is reduced because of the surface recombination posed by the damage. Furthermore, photoluminescence (PL) spectroscopy was performed, and the so-called “irradiation-induced defects,” defects that are formed typically after electron beam and ion irradiation, were observed at deep levels of 0.789 eV, 0.767 eV, and 0.714 eV. These irradiation-induced defects act as recombination centers and may cause the deterioration of the conversion efficiency in crystalline silicon solar cells. We believe understanding and controlling these defects are important for improving the conversion efficiency of solar cells.