Ion-implant doped large-area n-type Czochralski high-efficiency industrial solar cells

This paper discusses the design and fabrication of ion-implanted, high-efficiency, light-stable, 156 mm square, screen-printed solar cells on n-type Czochralski (Cz) silicon with full industrial processing. Doping by ion implantation provides a significant advantage over conventional furnace-based doping by providing uniform, full-area emitter and back-surface field (BSF) regions, and can eliminate four process steps over the conventional n-type cell process. Low emitter saturation current density (J_oe) values of 50 fA/cm² were achieved on boron implanted test structures passivated by an in-situ thermal oxide. Complete solar cells were fabricated with high values of short-circuit current density (J_sc), which is attributed to high lifetime of n-type base and also a superior phosphorous BSF compared to the conventional aluminum BSF (Al-BSF).