As solar technology matured, one of the most effective ways to extract more energy from the same sunlight was to combine different material properties in a single cell. Heterojunction Technology (HJT) is a hybrid architecture that marries two kinds of silicon to squeeze extra electrical output from sunlight.
What is HJT?
HJT cells combine a crystalline silicon wafer with very thin layers of amorphous silicon (a different form of silicon with distinct electronic properties) on both the front and rear surfaces. This heterojunction — literally a junction between different semiconductor structures — provides excellent surface passivation and suppresses electron–hole recombination more effectively than conventional methods.
This structure has several consequences:
- Lower optical and electrical losses
- Higher open-circuit voltage
- Stronger performance under low light and diffuse conditions
What makes HJT special
- Temperature behaviour: HJT has one of the lowest temperature coefficients among commercial solar cell types. That means its power output declines less as the cell warms in hot weather — a significant advantage in many real-world climates.
- Degradation resistance: HJT cells handle light-induced degradation exceptionally well, adding to their long-term performance appeal.
Practical performance
- Commercial module efficiencies range from roughly 21.5% to 23.5%
- Excellent performance in cool, cloudy or diffuse light conditions — making HJT particularly interesting for northern climates
Upsides
- High performance: Close to the best that silicon can offer
- Excellent temperature resilience
- Low degradation: Great prospects for long operational life
Challenges
- More complex to manufacture than standard silicon cells
- Higher upfront production cost
- Requires new or modified factory infrastructure
HJT’s best uses
HJT sits in the premium segment of the silicon market: a higher-cost, higher-yield option that makes most sense where land or roof space is limited and long-term performance is a priority.
For regions with variable light conditions — think Scotland, Canada’s Atlantic provinces, Scandinavia — that extra performance and resilience can translate into meaningful gains over decades.
Boˆreal 