High-efficiency large area ion-implanted n-type front junction Si solar cells with screen-printed contacts and SiO2 passivated boron emitters

This paper presents high-efficiency ion-implanted n-type front junction Si solar cells with SiO₂ passivated boron emitter and screen-printed contacts on 239 cm² Cz substrate. Starting with the baseline cell, we improved (a) emitter saturation current density (J_oe) via controlled etching of implanted boron emitter, (b) front contact by optimized firing, (c) bulk lifetime via optimized anneal conditions, (d) back passivation and escape reflectance via planarization with optimized back surface field profile, (e) back metallization formed by laser opening and physical vapor deposition, and (f) front metallization via enhanced aspect ratio of screen-printed grid, and optimized screen design. The combined effect of these technical improvements increased the cell efficiency from 19.1% to 20.7% for large area fully ion-implanted n-type front junction Si solar cells.