HJT (Heterojunction)

What Is HJT?

HJT (Heterojunction Technology) is an advanced solar cell technology that combines crystalline silicon (c-Si) with ultra-thin layers of amorphous silicon (a-Si). This combination of different material structures (heterojunction) enables excellent passivation and high efficiencies.

Structure

An HJT cell is symmetrically composed of:

1. Transparent conductive oxide layer (TCO)
2. Amorphous silicon layer (n-doped)
3. Intrinsic amorphous layer (i-a-Si)
4. Crystalline silicon wafer (n-type)
5. Intrinsic amorphous layer
6. Amorphous silicon layer (p-doped)
7. Transparent conductive oxide layer

Key Specifications

Property	Value
Cell efficiency	24—26.5%
Module efficiency	22—24%
Temperature coefficient	approx. -0.24%/°C (best value)
Bifaciality	85—95%
LID	No LID

Advantages

• Excellent temperature coefficient — ideal for warm locations
• No light-induced degradation (LID)
• High bifaciality — more yield from rear-side utilisation
• Fewer process steps in manufacturing

Practical Tip

HJT modules are especially worthwhile at high ambient temperatures and for tilt-mounted systems where the high bifaciality provides additional yield. They are currently slightly more expensive than TOPCon.