Stability of the regeneration of the boron–oxygen complex in silicon solar cells during module certification

• We investigate light-induced degradation on p-type Cz silicon.
• Passivated emitter and rear solar cells are fabricated and characterised.
• A degradation in conversion efficiency of 0.9%abs by LID is recovered by regeneration.
• Regeneration is stable upon moduling, degrades during accelerated aging as performed in common certification standards but is not annihilated completely.
• Regeneration of modules with p-type Cz–Si cells in the degraded state can occur during thermal cycling with simultaneous current injection.

Light-induced degradation in boron-doped p-type Czochralski silicon is caused by a boron–oxygen complex, which may be permanently deactivated by simultaneous illumination and heating leading to a permanent regeneration of carrier lifetime and solar cell performance. To date, the long-term stability of the regenerated state under thermal stress has not been fully investigated. In this work, we investigate whether the regeneration gain achieved on solar cell level is stable upon accelerated aging tests such as thermal cycling and damp-heat testing as applied during module certification according to IEC and UL standards. It is shown that regeneration is mostly conserved upon thermal cycling and cells in the degraded state may even be regenerated if current is injected during the treatment. Damp-heat testing at 85 °C in the dark for 1500 h decreases the regeneration-induced gain significantly but does not annihilate it completely.