Complete recovery of light induced degradation of Cz silicon solar cells with rapid thermal processing

Abstract

This paper reports on the use of rapid thermal processing (RTP) IR belt furnace to completely and permanently regenerate the effective minority carrier lifetime in Czochralski (Cz) crystalline silicon (cSi) solar cell after light induced degradation (LID). The average effective carrier lifetime of ∼33μs (19.2% efficiency) degraded to ∼25μs (18.8% efficiency) after 96 hours light soaking. Subsequent annealing on IR belt furnace at 310 inch per minute (ipm) at ∼ 760°C peak temperature with a ramp up and down rates of >100°C/sec resulted in complete recovery of the effective lifetime and efficiency. This total recovery is attributed to a combination of heat from the IR lamps and hydrogen from the SiN x :H antireflection coating (ARC). The recovery is permanent because the B-O defects are fully hydrogen passivated. Thus a fast ramp down rate of ∼100°C/sec is critical in hydrogen retention, which is the key to effective defects passivation.