Carrier Lifetime Limitation of Industrial Ga-Doped Cz-Grown Silicon after Different Solar Cell Process Flows

Abstract

Gallium-doped silicon material has been rapidly gaining importance in the photovoltaic industry as a boron-oxygen defect-free material with promising minority carrier lifetime. We investigate the influence of different cell process flows [passivated emitter and rear cell tunneling-oxide-passivating contact, and a 'hot oxidation' process] on the bulk material quality of an industrial Ga-doped Cz-grown silicon material, as well as its light-and elevated temperature induced degradation degradation behavior under light at elevated temperature. We measure a generally high carrier lifetime level, which remains limited by an unknown recombination-Active defect after most processes. Hydrogenation seems to passivate this unknown defect. In addition, we demonstrate that such high-quality p-Type material can suffer noticeably by iron even for extremely low concentrations below 109 at/cm3.