TOPCon

What Is TOPCon?

TOPCon (Tunnel Oxide Passivated Contact) is a high-performance cell technology considered the successor to the PERC cell. It uses an ultra-thin tunnel oxide layer (approx. 1.5 nm SiO2) and a doped polycrystalline silicon layer on the rear to drastically reduce recombination losses.

How It Works

The tunnel oxide layer is so thin that electrons can pass through it via quantum mechanical tunnelling, while it simultaneously acts as a passivation layer. The overlying n-doped polysilicon layer forms a selective contact that efficiently collects charge carriers.

Key Specifications

Property	Value
Cell efficiency	24—26%
Module efficiency	22—24%
Temperature coefficient	approx. -0.29%/°C
Bifaciality	80—85%
Market share (2024)	approx. 30% (rising sharply)

Advantages over PERC

• Higher efficiency (+1—2 percentage points)
• Better temperature coefficient
• Higher bifaciality (power generation also from the rear)
• Lower degradation (LID and LeTID)
• Compatible with existing PERC production lines

Practical Tip

TOPCon modules currently offer the best performance-to-price ratio for new installations. They are particularly attractive when roof space is limited and maximum yield is desired.