The impact of indium tin oxide deposition and post annealing on the passivation property of TOPCon solar cells

Abstract

In this paper, the influence of indium tin oxide (ITO) deposition on the passivation quality of tunnel oxide passivated contact solar cells was investigated. Both phosphorous-doped poly-Si/SiOx (n-TOPCon) and boron-doped poly-Si/SiOx (p-TOPCon) stacked films were fabricated on crystalline Si substrate, and ITO thin films were deposited by radio frequency (RF) magnetron sputtering system with various temperatures and RF powers, followed by post annealing. Effective minority carrier lifetime (τeff) of all the samples degraded drastically after ITO deposition. After post annealing, τeff of p-TOPCon samples exhibited significant recovery, while τeff of n-TOPCon samples only recovered partially. In addition, the deposition of ITO at lower RF power or room temperature leads to more effective recovery of τeff. The τeff recovery after ITO deposition thus depends on the types of TOPCon, which may be related to the film quality improvement of poly-Si during the post-annealing. The conversion efficiency of the top/rear TOPCon solar cells was decreased severely due to the sputtering damage during ITO deposition, and it can be improved by post-annealing at relatively high temperature.