HJT Technology: the future of photovoltaic panels ✨

Heterojunction technology (HJT) is a solar panel manufacturing method that has been on the rise since the last decade. It is currently the most effective process in the solar industry to increase efficiency and performance to the highest level.

Since the HJT manufacturing process requires four fewer steps than PERC technology, there is potential for significant cost savings. While PERC has been a popular option in the industry for many years, its complex manufacturing process cannot compete with HJT.

According to a 2019 ITRPV report, HJT cells are expected to gain 12% market share by 2026 and 15% by 2029.

How HJT technology works
Heterojunction solar panels are composed of three layers of photovoltaic material. HJT cells combine two different technologies into one: crystalline silicon and amorphous "thin-film" silicon.

The top layer of amorphous silicon captures sunlight before it hits the crystalline layer, as well as light that is reflected from the layers below.

However, single-crystalline silicon, the middle layer, is responsible for converting most of the sunlight into electricity.

Finally, behind the crystalline silicon, there is another layer of amorphous thin-film silicon. This last layer captures the remaining photons that have passed through the first two layers.

Using these technologies together allows more energy to be harvested than when used alone, achieving efficiencies of 25% or more.

HJT panel structure

Substrate:The construction of a solar cell starts with the substrate, which is usually made of crystalline silicon. The substrate provides structural support and serves as the foundation for the following layers.

N-type layer: A thin layer of amorphous n-type (negative type) silicon is deposited on the substrate. This layer serves as the emitter of the solar cell and allows electrons to flow.

Intrinsic layer: Next, an intrinsic (non-alloyed) layer of amorphous silicon is deposited on the n-type layer. This layer is responsible for absorbing photons from sunlight and generating electron-hole pairs.

P-type layer: A thin layer of p-type amorphous silicon (positive type) is deposited on top of the intrinsic layer. This layer acts as a back-side electric field (BSF) and facilitates the collection of holes.

Transparent conductive oxide (TCO) layer: A layer of transparent conductive oxide such as indium tin oxide (ITO) or fluorine doped tin oxide (FTO) is deposited on the p-type layer. This layer allows light to pass through while providing a conductive pathway for the generated charge carriers.

Front metal contacts: Metal contacts, usually made of silver or aluminum, are placed on the TCO layer to collect electrons generated by sunlight. These contacts allow the extraction of electric current from the solar cell.

Rear metal contacts: Similarly, metal contacts are placed on the back side of the substrate to collect the holes generated by sunlight. These contacts complete the circuit and allow current to flow.


Advantages og HJT Technology

Higher efficiency
Most HJT panels currently on the market have efficiencies ranging from 19.9%-21.7%. This is a huge improvement over other conventional monocrystalline cells.

Cost savings
Amorphous silicon used in HJT panels is a cost-effective solar energy technology. This thin-film solar panel requires a shorter manufacturing process compared to other technologies.
Due to the simplified manufacturing process, HJT has the potential to be more affordable than alternative solutions.

Durability and adaptability
This technology has been developed for high performance even in extreme weather conditions.
HJT panels have a lower temperature coefficient than conventional solar panels, ensuring high performance at higher outdoor temperatures.

Lifetime
The average lifespan of thin-film PV modules is up to 25 years, while HJT solar cells can remain fully operational for more than 30 years.