19% efficient screen- printed cells using a passivated transparent boron back surface field

Boron back surface field is a promising replacement for the industry standard screen-printed Aluminum. However, the use of boron back surface fields is largely confined to laboratory scale solar cells. In order to increase its industrial applicability, we present a method for achieving a high quality boron back surface field using a cheap and safe boron source and short diffusion time. Metal contacts are fabricated using screen-printing, and degradation of rear passivation after contact firing is minimized through optimized screen-printing of local (point) contacts on the rear. On p-type silicon wafers, this process technology has been utilized to achieve, on 4 cm² cells, efficiency of up to 19.1% with open-circuit voltage of 650 mV.