Bifacial p-type silicon PERL solar cells with screen-printed pure silver metallization and 89% bifaciality

We present 6-inch bifacial p-type Czochralski-grown silicon passivated emitter and rear locally-diffused (PERL) solar cells with ""pPassDop"" layer stack on the cell's rear side. The ""pPassDop"" layer stack consists of an aluminum oxide and a boron-doped silicon nitride layer serving as both surface passivation and doping source. Local laser processing introduces boron and aluminum atoms from the ""pPassDop"" layer stack into the silicon. The electrical contacting of the formed line-shaped p-doped back surface field is realized by screen-printed and fired pure silver contacts (i.e. without aluminum). The fabricated PERL solar cells reach high bifaciality of up to 89%. The monofacial peak front side energy conversion efficiency, measured with contact bars on both sides on a black non-conducting chuck, is given by 19.8%. Fill factors of more than 79% and specific contact resistances in the single-digit mOcm²- range prove the successful low-resistance contacting on both sides. It is important to stress that the same commercial state-of-the-art firing-through pure silver screen-printing paste is used for the cell's front and rear side metallization. A special alignment procedure ensures that the rear silver grid with finger widths of about 65 mm is placed over the whole wafer on top of the about 37 mm-wide laser-doped and opened structures.