What is TOPCon?

TOPCon (Tunnel Oxide Passivated Contact) improves upon PERC by passivating both surfaces through an ultra-thin silicon oxide tunnel layer and doped polysilicon layer.

Technical mechanism

Carriers cross the ~1.5 nm tunnel oxide via quantum tunnelling while recombination is blocked — achieving near-ideal "passivating contact" behaviour. Result: higher Voc (690–710 mV vs 665–680 mV for PERC).

Commercial specs (2025)

• Cell efficiency: 23.5–24.5%
• Module power (182mm, 72-cell): 570–600 Wp
• Temperature coefficient (Pmax): −0.30 to −0.32%/°C
• Degradation rate: ~0.4%/year vs ~0.5%/year for PERC

India market context

TOPCon entered Indian commercial supply in 2024 at ~15–25% premium over PERC. ALMM-listed manufacturers including Waaree, Adani Solar, and RenewSys offer TOPCon modules as of 2025.