Yash
The Heterojunction (HJT) solar cell was first introduced in the early 1980s by Sanyo and later by Panasonic of Japan.
The product cost of the HJT solar cells has reduced significantly in the last decade.
This technology is becoming one of the top choices of manufacturers for making solar panels with increased efficiency.
What is a Heterojunction solar cell?
The HJT solar cell is made by sandwiching the N-type crystalline silicon between the thin layers of amorphous silicon.
Hence, it uses both crystalline and thin-film technology.
The thin films of amorphous silicon ( ̴120 micro-meter) are pasted on both sides of n-type crystalline silicon. HJT solar cell is made.
The thin-film amorphous silicon and crystalline silicon work complementary.
On the one hand, crystalline silicon absorbs most of the sunlight.
While on another hand, a-silicon prevents electron-hole recombination due to its passivation property.
This dual effect increases the harvesting power of the HJT cell that you do not find in a traditional solar cell.
Benefits of Heterojunction Solar panels
Anti-LID
N-type Heterojunction (HJT) solar cells are more immune to the Light-Induced Degradation (LID) effect.
LID is the loss in the panel output within the first few hours of its exposure to sunlight.
The P-type (boron-doped) solar cells are more prone to the LID effect.
During its manufacturing, the oxygen atoms get trapped in the cells.
And
When exposed to sunlight, the oxygen reacts with the boron to form a complex boron-oxygen compound.
This complex compound makes its free electrons difficult to produce a photovoltaic effect.
Thereby you see power loss in the solar panels based on p-type (boron-doped) solar cells.
But
There is no such compound formed in the HJT solar cells when exposed to sunlight.
Therefore, they are more immune to the LID effect.
And
You see less degradation in the solar panels based on this technology.
Water-resistant
The HJT cells are encapsulated in a highly resistant polymer back sheet and laminated in anti-reflective glass.
Due to this, it is difficult for water and humid air to penetrate the cells. Therefore, they can be used in hot and humid climates.
More power even at high temperatures
They have a lower temperature coefficient of power.
When the electron leaves its excited state and drops into the hole, it is called recombination. In this process, energy is released.
And
It can be in the form of heat.
The ultra-thin amorphous silicon layer is very effective in preventing electron-hole recombination.
The HJT solar cells have a lower temperature coefficient of power because of their property to check heat generation.
Please see the part of the datasheet of REC Alpha series solar panels.
They are based on HJT cell technology.
We see that they have -0.26%/°C as the temperature coefficient of power.
This value is one of the lowest in the market.
Assuming, the solar cells are operating at 45 °C, the power loss would be:
Power loss (%) = (cell temperature – 25 °C) x temperature coefficient of power
= (45 °C – 25 °C) x -0.26%/°C
= 5.2% of power is lost at 45 °C
HJT solar panels work effectively in hot climates.
Read: Best Solar Panels for Hot Climates
You get extra current
Heterojunction solar cells are bi-facial by nature.
They produce current from the rear side too.
And
you get 15-20% more energy than the traditional mono-facial solar panels.
In case, you have space constraints then use HJT solar panels.
They produce current from both sides and you meet your energy demands with fewer panels,
Top Heterojunction Solar Panels manufacturers
- REC Solar: Norway/Singapore
- CSI Solar: Canada
- Huasun: China
- AE Solar: Germany
- SONM: Egypt
- UZON PV: China
- Akcome Optronics Science & Technology: China
Conclusion
If you already have a PERC module plant, shifting to the Heterojunction solar cell technology would be financially unattractive.
When you are starting from scratch, setting up an HJT plant is profitable as they are more efficient than the other traditional panels.
I expect many more manufacturers to come up with new HJT production lines.
As a homeowner, if the benefits of HJT solar panels outweigh the cost involved.
It is an excellent option to go for the solar power system on the roof.
Why not try Solar Feasibility Spreadsheet to know the return from your solar power system?
It designs the complete solar power system and finds the financial feasibility beforehand.
In that way, you make an informed solar decision.
Yash has over a decade of experience in Solar PV technology and is the founder of Solar with Yash.
Check out his Youtube Channel Solar Design and Payback with Yash
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