Rear-side All-by-Laser Point-contact Scheme for liquid-phase-crystallized silicon on glass solar cells

• Rear-side All-by-Laser Point-contact Scheme was developed for LPC poly-Si solar cells.
• Contact holes in back-reflector resist were formed by UV-laser marking and etching.
• Laser firing of phosphorus SOD on Ag resulted in low-resistance absorber contacts.
• Best solar cell efficiency obtained for a planar n-type Si absorber was 11.5%.

We report here on the development of a rear-side point-contact scheme for liquid-phase-crystallized silicon on glass solar cells, which uses laser for all structuring and contact-post-treatment steps. Our contact scheme is based on the procedure developed by CSG Solar and contains two main innovations. First, we demonstrate here that it is possible to form contact holes in the back-reflector resist layer by laser ablation instead of printing droplets of an etch solution with inkjet. The use of laser for forming holes in the resist holds promise for enhancing the precision and reliability of this process. Second, we show that for both p and n-type absorbers, laser firing at the absorber-point-contacts can be used to increase the doping concentration beneath the metal contact and thereby achieve low-resistance contacts. Using the All-by-Laser Point-contact Scheme (ALPS) we were able to reach a solar cell conversion efficiency of 11.5% for a planar n-type laser-crystallized silicon absorber with an amorphous/crystalline heterojunction structure.