21%-efficient PERL Solar Cells with Plated Front Contacts on Industrial 156 mm p-type Crystalline Silicon Wafers

Abstract

We have achieved 21% large-area conversion efficiency with PERL (passivated emitter, rear locally diffused) solar cells featuring plated front contacts. Industrial 156mm p-type Czochralski single-crystalline silicon wafers were used as substrates. Our cells employ a single-side texture, a single-side emitter, and a double-layer anti-reflective coating composed of PECVD silicon nitride and thermal silicon oxide layers. The rear side is passivated with a dielectric stack (Al2O3–SiOxNy), and the rear contacts are formed through laser-ablated openings by screen-printing and firing an aluminum electrode. The nickel–silver or nickel–copper–silver contacts are plated on the front side by light-induced plating (LIP). The champion batch shows average values of 669mV open-circuit voltage, 40.0mA/cm2 short-circuit current density, and 77.3% fill factor. The efficiency of our PERL cell is currently limited by the series resistance. Implementing small (1–2μm) and uniform pyramids and thermally annealing the cells after plating show promising results for future improvements.