Efficiency enhancement of i-PERC solar cells by implementation of a laser doped selective emitter

• 0.4% absolute efficiency enhancement by the incorporation of a laser doped selective emitter into a PERC cell structure.
• Peak efficiency of 20.5% obtained.
• Faster processing speeds (>2m/s) observed to cause less bulk damage than slower processing speeds.

In this work, we present the incorporation of a laser doped selective emitter into the i-PERC platform at Imec using large area magnetically confined boron-doped Czochralski grown silicon wafers. Cells were fabricated with self-aligned plated n-type contacts with a comparison between the use of a homogenous emitter with contact openings formed by picosecond laser ablation and a selective emitter formed by laser doping with a mode-locked UV laser using various processing speeds. Without modification to other processes in the i-PERC platform, improvements in efficiency of approximately 0.4% absolute were obtained with the inclusion of the selective emitter structure through improvements in open circuit voltage, fill factor and reduced series resistance. This resulted in peak efficiencies of 20.5% using a processing speed for laser doping of 5 m/s.