Recent developments in rear-surface passivation at Fraunhofer ISE

Fraunhofer ISE has a long experience in the field of surface passivation for crystalline silicon wafers. Novel rear-surface passivation layer systems have led to excellent results. Using a low-temperature passivation stack of hydrogenated amorphous silicon and plasma-enhanced chemical vapor deposition (PECVD) silicon oxide an efficiency of up to 21.7% has been achieved. Thermally stable passivation can be proven with all-PECVD stacks of silicon oxide, silicon nitride, and silicon oxide (PECVD-ONO), i.e. after contact firing. Solar cell efficiencies of up to 20.0% have been reached with PECVD-ONO. In parallel, Fraunhofer ISE is working on silicon carbide (SiC x ) layers, which provide excellent and thermally stable passivation, as well deposited by PECVD. Solar cells with SiC x layers as rear passivation led to efficiencies of up to 20.2%.