Surface recombination velocity of phosphorus-diffused silicon solar cell emitters passivated with plasma enhanced chemical vapor deposited silicon nitride and thermal silicon oxide

TLDR

The study compared three passivation schemes—stoichiometric PECVD silicon nitride, forming‑gas‑annealed thermal silicon oxide, and aluminum‑annealed thermal silicon oxide—on phosphorus‑diffused emitters with sheet resistances from 30 to 430 Ω/□ (planar) and 50 to 380 Ω/□ (random‑pyramid). PECVD silicon nitride yields surface recombination velocities of 1,400–25,000 cm/s, while thin thermal oxides—especially aluminum‑annealed ones—achieve superior passivation with Sp ranging from 250 to 21,000 cm/s, and the optimized PECVD films remain adequate for most silicon solar cells.

Abstract

The emitter saturation current density (JOe) and surface recombination velocity (Sp) of various high quality passivation schemes on phosphorus-diffused solar cell emitters have been determined and compared. The passivation schemes investigated were (i) stoichiometric plasma enhanced chemical vapor deposited (PECVD) silicon nitride (SiN), (ii) forming gas annealed thermally grown silicon oxide, and (iii) aluminum annealed (alnealed) thermal silicon oxide. Emitters with sheet resistances ranging from 30 to 430 and 50 to 380 Ω/□ were investigated for planar and random-pyramid textured silicon surfaces, which covers both industrial and laboratory emitters. The electronic surface passivation quality provided by PECVD SiN films was found to be good, with Sp values ranging from 1400 to 25 000 cm/s for planar emitters. Thin thermal silicon oxides were found to provide superior passivation to PECVD SiN, with the best passivation provided by an alnealed thin oxide (Sp values between 250 and 21 000 cm/s). The optimized PECVD SiN films are, nevertheless, sufficiently good for most silicon solar cell applications.