Influence of a gold seed in transparent V₂O_x/Ag/V₂O_x selective contacts for dopant-free silicon solar cells

Abstract

Dielectric/metal/dielectric structures based on vanadium pentoxide with a thin silver interlayer have been optimized to replace traditional transparent electrodes. As would be expected, there is a trade-off in the metal thickness to achieve simultaneously high transparency and low sheet resistance. It has been demonstrated that an ultrathin gold seed prevents the tendency of silver to form clusters. This wetting effect reduces the metal thickness needed to form a continuous film, which leads to a higher averaged transmittance and very low sheet resistance. On the other hand, vanadium pentoxide on silicon forms a high quality hole-selective contact. Thus, these structures can be used as an all-in-one transparent electrode and selective contact for a new kind of heterojunction solar cells. This concept has been proved in a 13.3% efficient solar cell fabricated on n-type silicon wafers. Besides dopant-free, the complete fabrication route did not require any sputtered transparent electrode.