Understanding of the annealing temperature impact on ion implanted bifacial n-type solar cells to reach 20.3% efficiency

Adeline Lanterne (1, 2, 3) , Jerome Le Perchec (1, 2, 3) , Samuel Gall (3) , Sylvain Manuel (3) , Marianne Coig (4) , Aurélie Tauzin (4) , Yannick Veschetti (3, 2, 1)

1 INES - Institut National de L'Energie Solaire
2 DTS - Département des Technologies Solaires
3 LITEN - Laboratoire d'Innovation pour les Technologies des Energies Nouvelles et les nanomatériaux
4 CEA-LETI - Commissariat à l'énergie atomique et aux énergies alternatives - Laboratoire d'Electronique et de Technologie de l'Information

Ion implantation has the advantage of being a unidirectional doping technique. Unlike gaseous diffusion, this characteristic highlights strong possibilities to simplify solar cell process flows. The use of ion implantation doping for n-type PERT bi-facial solar cells is a promising process, but mainly if it goes with a unique co-annealing step to activate both dopants and to grow a SiO 2 passivation layer. To develop this process and our SONIA cells, we studied the impact of the annealing temperature and that of the passivation layers on the electrical quality of the implanted B-emitter and P-BSF. A high annealing temperature (above 1000°C) was necessary to fully activate the boron atoms and to anneal the implantation damages. Low J 0BSF (BSF contribution to the saturation current density) of 180 fA/cm 2 was reached at this high temperature with the best SiO 2 passivation layer. An average efficiency of 19.7% was reached using this simplified process flow ("co-anneal process") on large area (239 cm 2) Cz solar cells. The efficiency was limited by a low FF, probably due to contaminations by metallization pastes. Improved performances were achieved in the case of a "separated anneals" process where the P-BSF is activated at a lower temperature range. An average efficiency of 20.2% was obtained in this case, with a 20.3% certified cell.

Keywords: silicon solar cells; ion implantation; n-type; thermal annealing; phosphorus BSF; boron emitter

Domains: Engineering Sciences [physics]; Electric power; Materials; Micro and nanotechnologies/Microelectronics; Optics / Photonic

Adeline Lanterne, Jerome Le Perchec, Samuel Gall, Sylvain Manuel, Marianne Coig, et al.. Understanding of the annealing temperature impact on ion implanted bifacial n-type solar cells to reach 20.3% efficiency. Progress in Photovoltaics, 2015, 23 (11), pp.1458-1465. ⟨10.1002/pip.2574⟩. ⟨cea-02570664⟩