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 (SiCx) layers, which provide excellent and thermally stable passivation, as well deposited by PECVD. Solar cells with SiCx layers as rear passivation led to efficiencies of up to 20.2%.