HJT Solar Cell Technology Introduction

HJT Solar Cell Technology Introduction

Make Solar Energy More Efficient

What Is Heterojunction(HJT) Solar?

HJT is the acronym for hetero-junction solar cells. Introduced by Japanese company Sanyo in the 1980s, then acquired by Panasonic in 2010s, HJT is considered as a potential successor to the popular PERC solar cell as of the time of writing, besides other technologies such as PERT and TOPCON.

Due to HJT’s fewer number of cell processing steps, and a much lower cell processing temperatures, this architecture has the potential to simplify the current solar cell manufacturing lines that are currently heavily based on PERC technology.

How does HJT work?

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 catches sunlight before it hits the crystalline layer, as well as light that reflects off the below layers. However, monocrystalline silicon, the middle layer, is responsible for turning most of the sunlight into electricity. Lastly, behind the crystalline silicon is another amorphous thin-film silicon layer. This final layer captures the remaining photons that surpass the first two layers.

Figure 1: p-type PERC vs n-type HJT solar cell

As shown figure 1, HJT is very different to the popular PERC structure. As a result, manufacturing processes between these two architectures are very different. Compared to n-PERT or TOPCON, which can be upgraded from the current PERC lines, HJT requires significant capital investment in new equipment to start mass productions.

HJT demonstrates high solar cell efficiency thanks to the high quality hydrogenated intrinsic amorphous Si (a-Si:H in Figure 1) that can provide impressive defect passivation to both the front and rear surface of Si wafers (both n-type and p-type polarity).

The use of ITO as transparent contacts also improves current flows, while also acting the anti-reflection layer to provide optimal light capturing. Moreover, ITO can also be deposited via sputtering at low temperature, thus avoiding the re-crystallisation of the amorphous layer that will impact the passivation quality of the materials on the bulk Si surface.

In spite of its processing challenges and high capital investments, HJT is still an attractive technology. This technology demonstrates the ability to achieve >25% solar cell efficiency, compared to ~22% shown by TOPCON, PERT and PERC technologies.

Advantages of Heterojunction Solar Cells

Here are a few key advantages of using HJT solar cells for your building:

  • Higher efficiency

    JG Solar HJT panels that are currently on the market have efficiencies ranging from 21.0%–22.8%. This is a massive improvement compared to other conventional monocrystalline cells. It is by far the highest solar panel efficiency of HJT mass production.

  • Cost savings

    The amorphous silicon used in HJT panels is a cost-effective photovoltaic technology. This thin-film solar requires shorter manufacturing compared to other technologies. Because of its simplified manufacturing process, HJT has the potential to be more affordable than alternative solutions.

  • Resilience and adaptability

    This technology was developed for excellent production capabilities, even in extreme weather conditions. HJT panels have lower temperature coefficient than conventional solar panels, ensuring high performance at elevated external temperatures.

  • Life expectancy

    On average, thin-film photovoltaic modules have a life expectancy of up to 25 years, while HJT solar cells can remain fully functioning well over 30 years.

The Future of HJT Solar

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

Given the several advantages of HJT solutions, it is likely that more companies will continue to adopt this technology in the near future. Because 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. In addition, PERC does not offer HJT’s high temperature performance benefit.

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