Resurgence of Heterojunction (HJT) Solar Panels

After being overlooked initially for many years, there has been a resurgence of interest in Heterojunction technology (HJT) in the last couple of years. From Reliance to Goldi Solar, many private players in India have shown a growing interest in HJT solar technology.

It is intriguing that the Indian market is witnessing an escalating interest in HJT solar panels, even as other popular and successful solar technologies exist today. Before we get to that, let’s understand what is a heterojunction solar panel.

Heterojunction (HJT) Solar Panels

Heterojunction technology solar panels work just like other PV modules – under the photovoltaic effect. The main difference, however, is that this technology uses three layers of absorbing materials.

HJT solar cells combine two different technologies into one cell – a crystalline silicon cell sandwiched between two layers of amorphous “thin-film” silicon. It is believed that the arrangement increases the efficiency of the panels with more energy being harvested when compared to conventional silicon solar panels.

The silicon film on top captures some sunlight before it hits the crystalline layer, as it also absorbs sunlight that bounces off the layers below. Due to its thin thickness, it let through much of the sunlight to the middle layer. Further, the sunlight that passes through the middle, that is the crystalline layer, is absorbed by another thin amorphous layer on another side.

The HJT production concept was first developed by SANYO Electric in the 1980s (SANYO was acquired by Panasonic in 2009). Yet, the technology has only got traction in recent years. A notable manufacturer was of course the REC group, now acquired by Reliance .

Let’s understand why it is gaining momentum now.

Why Manufacturers are Pushing for HJT Solar Panels?

HJT is fast emerging as a competition for PERC, the current workhorse for the global PV industry. Amorphous silicon is thin-film silicon. Unlike crystalline silicon, it does not have a regular crystalline structure. Instead, the silicon atoms are randomly ordered, resulting in lesser manufacturing costs than solar panels made with crystalline silicon – either monocrystalline or polycrystalline. HJT solar takes advantage of this by building a solar panel out of three different layers of photovoltaic material.

A phenomenon called surface recombination occurs in standard c-Si PV modules, limiting their efficiency. The HJT cells reduce surface recombination, ultimately increasing the efficiency of the module by as high as up to 26 per cent.

Advantages of HJT Panels

The solar industry produced 5GW in heterojunction solar panels in 2019, making HJT technology hold around 5% of the retail market. The largest manufacturers were Tesla in the US and Panasonic in Malaya and Japan. As per International Technology Roadmap for Photovoltaic (ITRPV), with an expected price of $0.19/W for 2029-2030, HJT technology could hold 15% of the retail market compared to around 5% of the retail market it held in 2019.

We know that the Bifacial cells trump monofacial solar panels with better performance, better durability, and reduced PID, the former remains the favourite for the growth in solar. HJT solar panels have a similar structure to bifacial solar panels, which helps them reduce resurface combinations, and increase efficiency. Moreover, HJT cells can be designed for mono-facial or bifacial usage, which reduces the reasons to compare them against each other since they can be combined to create superior bifacial HJT solar panels. There are multiple benefits to using HJT solar panels.

Further, its ability to collaborate with other technologies makes it famous for its high efficiency. It gives over 26 per cent solar conversion efficiency for monofacial modules and more than 30 per cent for bifacial. Thanks to a high bifaciality factor of 92 per cent, HJT delivers a mighty performance as a bifacial module. This makes it convenient for limited space applications and areas requiring large generation capacities. Its popular applications in limited space are the manufacturing of solar shingles and Building Integrated Photovoltaic (BIPV) products. Tesla roofs are among the most popular shingles using this technology, which greatly increases the solar efficiency of a home with photovoltaics.

High temperatures can negatively affect the performance of standard c-Si modules. However, in the case of HJT modules, temperature changes don’t affect much. Thus, it can be used in regions of high temperatures without concern.

Private Indian Firms Pushing for HJT Modules

Owing to the prospects of HJT mentioned above, several firms in India are also treading toward technology to improvise the existing solar PV panels. Reliance made a move last year, acquiring REC Solar Holdings, a module manufacturer of HJT technology, for $771 million. For the Indian major, that was just the beginning with HJT. Earlier this year, Reliance signed up with Maxwell Technology to purchase a 4.8 GW total annual capacity of HJT cells. Recently, REC Group also signed a supply agreement with Maxwell Technologies for HJT solar cell and module manufacturing equipment. Maxwell will supply 600 MW of manufacturing equipment for REC’s latest HJT innovation, REC Alpha Pure-R.

Another leading solar brand in India, Goldi Solar, announced its entry into HJT, infusing over INR 5,000 crores as a part of its business expansion plans. Goldi Solar claims to be the first Indian manufacturer to announce a 710 Wp module based on the latest Heterojunction technology. It plans to open up a cell manufacturing facility in Gujarat by 2023.

A major reason for the adoption of HJT is also the fact that the market for private sector owned solar is expected to expand in a big way, and in this case, it is not always lowest cost, but overall efficiency and longevity that also matters. REC Group, which had been serving this market in India too, had seen significant success with such C&I category clients.

As India pushes to enlarge domestic solar manufacturing, endorsement of technologies like HJT by industrial leaders is set to diversify the array of solar panels in India.