As solar technology evolves to keep up with the increasing adoption to help lower manufacturing costs and increase the efficiency of solar modules, Indian solar module manufacturers have been leaning towards the latest TOPCon (Tunnel Oxide Passivated Contact) module technology over its other mainstream rival – HJT (Heterojunction).

In the Indian solar market, where the p-type mono PERC is well established, manufacturers are looking at the next big technology to replace it to achieve higher efficiency rates.

TOPCon and HJT are both N-type technologies and have minimal efficiency differences at the manufacturing level. HJT, however, is said to perform better in terms of degradation rate and temperature coefficient.

According to  Balachander Krishnan, Chief Operating Officer at Indosol Solar, a special purpose vehicle of Shirdi Sai Electricals, the only advantage that HJT can claim is the temperature coefficient, which is -0.25%/°C. TOPCon is -0.30%/°C, due to which HJT technology gives higher power output, especially in hotter countries.

“TOPCon is veering towards Bi-poly or double poly and further towards back contact, and HJT will eventually move towards back contact if it’s successful.”

Vasanthi Sreeram, Chief Technical Officer and Director at Websol Energy System claims that even if HJT has higher efficiency than TOPCon, the efficiency levels in TOPCon can be enhanced by adding back contact and other structures.

Cost & Availability

One of the major factors giving TOPCon the edge over HJT technology is its easy availability and cheaper installation and production costs.

The CAPEX required for HJT production is almost three times higher, and OPEX is 2.5 times higher compared to ToPCoN technology. The CAPEX for the HJT production line is about $70 million per GW, whereas for TOPCON, it is $40 million per GW.

Sreeram said, “The major factor distinguishing TOPCon and HJT is the availability factor. The HJT modules tend to have ~50% higher CAPEX and ~30% higher OPEX as compared to TOPCon. The cost factor impacts the demand and, consequently, the availability of the TOPCon modules. Substantial research goes into TOPCon technology, making it more readily available. Whereas, the companies investing in HJT technology are the ones who wish to cater to the niche market and stand out from the crowd.”

The widely installed mono PERC production lines can be transformed into TOPCon lines with ease, which otherwise would require high capital infusion.

Due to its complexity, HJT manufacturing equipment is difficult to procure at scale, limiting the options to very few globally. Since TOPCon manufacturing equipment is more readily available in the market than HJT, the demand is relatively higher.

According to Krishnan, even though HJT claims to have a lesser number of steps, when it comes to the cost, TOPCoN is a clear winner, both in terms of CAPEX and OPEX.

He said, “The succession from PERC to TOPCon was relatively easy by adding a few pieces of equipment. China alone has 700 GW of manufacturing, while HJT still has not crossed 40 GW. Considering the overall cost, people are still not keen towards moving into mass manufacturing.”

“Unless HJT CAPEX and OPEX, especially the overall silver laydown and replacement of Indium Tin Oxide with Aluminium doped Zinc Oxide, come down, it’s going to be difficult. As in the past, solar manufacturing is always dictated and driven by cost. Apart from this, the BOM (bill of materials) required for HJT is extremely different from the traditional technologies, so the supply chain has not matured, and competitive cost advantages are not likely to happen anytime soon,” he added.

In India, where cost is a significant factor, consumers look at the cost saved per unit of energy when installing newer technology. The decision ultimately comes down to the per-watt price.

Avinash Hiranandani, Global CEO and Managing Director at RenewSys said, “As far as technologies go, mono-PERC and TOPCon will exist parallelly for a while, as everything depends on the price and per watt price of these products. Consumers prefer the one that is cheaper and has a wider price gap. One gives 545W power and the other 580W. If the price gap in the sale is too much, people would then prefer per watt price.”

At an ingot/wafer level, TOPCon and HJT technologies cost the same at ~$0.115/Wp, whereas at the cell level, HJT costs $0.079/Wp, compared to $0.042/Wp for TOPCon.

Cost and availability factors continue to be the primary reasons for most manufacturers in India to choose TOPCon technology.

Technology Outlook

While both technologies continue to scale and reach higher efficiencies, Indian solar module manufacturers are leaning towards TOPCon for now.

However, manufacturers continue to remain cautious when choosing newer technologies.

Hiranandani said, “The P-type technology, from which PERC is derived, has been stable, and everyone in the market has used it for the last couple of years. TOPCon N-type is a newer technology, and one has to be cautious while using any new technology.”

Mercom had reported on how the Indian government effectively eliminated polycrystalline modules, whose efficiencies have peaked at 17-18% from being listed in the Approved List of Models and Manufacturers. The step was to impose the use of newer technologies such as mono PERC and others in the Indian solar landscape.

Many have even raised questions about how long TOPCon would survive the cost-sensitive Indian market.

According to Sreeram, “TOPCon is expected to continue in the market for at least the next five years, and it is only going to improve considering the technological investments in it. Mono-PERC, however, will not go away from India because of its price advantage and ease of production. In China, they have moved on to TOPCon and HJT completely in terms of production because of the efficiency; in India, however, it will stay on for a few more years.”

A senior executive at a renowned module manufacturing company, on the condition of anonymity, expressed that even though his company is one of the few to install HJT lines, they are yet to scale the production given the increased demand for TOPCon in the market at the moment.

While talking about the future of the two top technologies, Krishnan says HJT can match TOPCon if the cost factor is mitigated by replacing silver with copper in mass manufacturing.

He said, “While the cost of CAPEX could come down when the capacity is increased, it must be competitive enough with TOPCon. The expectation is that after three to four years, both may have equal advantages. However, in the cost-sensitive Indian market, it will take even longer for HJT to gain traction.” He expected this to happen after 5- 6 years, provided the issues with HJT were sorted.

The success of either of these two technologies in India will be based on their overall performance, efficiency, and reliability with the lowest cost $/Wp, which is what Indian solar manufacturers considered when transitioning from multi to mono-PERC, and the same is likely to happen from P-type to N-type as well.

“Module manufacturers must closely track the direction of module technologies and strategically plan future investments based on anticipated technological shifts expected in the next 3 to 5 years to avoid the fate of many smaller polycrystalline manufacturers in India who failed to adapt to changing trends on time, and suffered as a result,” said Raj Prabhu, CEO of Mercom Capital Group.