- HJT solar cell technology is growing its clout in mass production, albeit at a slower pace than TOPCOn
- Further efficiency improvement may be on the anvil, but cost considerations are equally important when scaling up
- Metallization and wafer thickness are major factors where cost reduction is possible
From being talked about in one breath with TOPCOn as a potential contender to replacing PERC till about a year back, heterojunction (HJT) solar cell technology has carved a niche for itself since then. Several manufacturers, not just in Asia but also in Europe, have launched their production lines—some at pilot level—despite HJT carrying the ‘expensive’ tag.
On day 2 of TaiyangNews High Efficiency Solar Technologies Conference, we tried to understand from players in the solar value chain about how HJT can have a stronger presence as a high efficiency solar cell technology.
In his keynote address, ITRPV Steering Committee Chair Dr. Markus Fischer shared the new maturity update of the 13th edition of the roadmap with an overview of the global solar PV technology market. Technological advancements are leading to further cost reduction for the industry. In 2021, the world shipped 183 GW solar modules for $0.24 per W spot market price, but this year analysts expect the shipments to swell to over 250 GW for a cost of $0.23 per W.
Global cumulative production capacity by 2022-end should grow to 600 GW, with 95% of it being c-Si based. Going forward by 2032, Fischer said PERC will continue to remain the workhorse of the PV industry with TOPCon by its side, while silicon heterojunction (SHJ) will expand its presence among cell technology market share for its high efficiency properties.
At present, the average HJT module efficiency is 22% in 2022, and likely to grow to 24% in a decade, he added.
In another keynote, in particular for HJT, the Head of R&D Department of Research Center Jülich, Dr. Kaining Ding presented the latest HJT technology progress with the optimism that there it has a lot of scope for further cost improvement. It can be achieved by using up to 85% less indium or even going 100% indium free which may lead to some efficiency loss in the absence of a suitable alternative. Efficiency being the important attribute of HJT, Ding noted that achieving efficiencies above 25% with cost-effective methods is possible.
There is growing demand among manufacturers around the globe that are taking HJT seriously with the biggest of them being India’s Reliance Industries Limited (RIL) that acquired HJT producer REC Group and taking the technology to India for its Gigafactory plans (see Reliance Bets On Heterojunction Production).
Italy’s Enel Green Power’s (EGP) 3 GW HJT production fab in Europe is expected to come online in 2023. It is now also taking the same technology to the US as recently announced by the company (see More Europeans Heading To US For Solar Manufacturing).
China remains strong compared to its peers elsewhere as, according to Ding, the country has more than 8 GW of installed SHJT production capacity, but another 218 GW is under construction or planned. “We don’t know how much of it will be realized but this shows the interest is high among investors,” added Ding. It also has a growing number of suppliers that’s helping bring the cost down.
Being one of the earliest adopters of the HJT technology, Risen Energy is raising its stakes. The company currently operates 500 MW cell and module capacity each for its HJT Hyper-ion solar modules. According to Risen Energy’s General Manager, HJT, BU, Po-Chuan Yang by H1/2023, it aims to expand the same to 5 GW each, eventually scaling it up to 15 GW each by 2023-end.
It uses a patented 24BB technology for Hyper-ion modules using G12 half wafer+120um and a 4-step production process. Using an ultra-thin wafer will save silicon material greatly and thus bring down its carbon footprint, Yang pointed out.
R&D Director of solar cells at Huasun, Su Zhou’s presentation was focused on mass production status and future trend of HJT solar cells. The Chinese company’s Q2/2022 production capacity of HJT solar cells and modules was 2.7 GW each. It claims to have reduced the use of silver in its production process.
According to the company’s HJT cell efficiency roadmap, it targets to grow from 25.2% in 2022 when it produces G12 and 132 cell based half cut module having 720W output, to 745W module with 26.0% efficiency in 2024.
Further on, the aim is for 28.0% efficiency with a tandem cell of HJT and perovskite in 2025, shared Zhou.
Chinese HJT solar PV production equipment supplier Maxwell’s VP, Overseas Sales, Peter Wolf shared that the company continues to optimize its equipment in terms of metallization and other measures. It has been able to increase mass production HJT solar cell efficiency with n-nanocrystalline to 25.0%, and with further improvements targets to go up to 26.0% in 2023. As to reducing the usage of indium while Wolf sees no immediate need, Maxwell has developed a platform that supports adaptation of no or low indium based TCO deposition. Maxwell is also looking into possibilities for copper plating which it admits will push up costs, but lead to better efficiencies.
Talking about wet chemical innovations in SHJ and TOPCon cell processing, RENA Technologies’ Senior R&D Manager Solar & Battery, Damian Brunner said his company has cost-effective, proven high throughput solution for SHJT texture. It offers 2 validated options for SHJ inline plating, namely mask and inline plating directly on TCO with no seed, and plate on silver seed layer with SiNX cover-layer masking.
However, RENA’s HJT solutions are still at the R&D stage while it caters to TOPCOn customers, but Brunner said the wet chemical solutions provider remains open to industry partnerships in this space.
During the conference, Vice President of Technology, Overseas for Solamet, Kaien Chang listed ‘pain points’ for HJT metallization process as limited cost reduction potential compared to mono PERC and TOPCon. Additionally, it has low printing speed and not applicable to fine line screen, leading higher paste laydown. To deal with this, Solamet developed several paste platforms the latest of which could successfully address the key bottlenecks such as fineline printability and high laydown.
The company has also developed an ultra-low temperature cured paste for perovskites based tandem cell that can be cured at 130 0C and keeps the resistivity at par with the pastes cured at higher temperatures. However, these latest generation of pastes require little more tweaking immunity from moisture as indicated by peeling after hot water test. A better module encapsulant can also provide a superior barrier.
Hangzhou First’s R&D Engineer Kevin Wu deliberated on high quality encapsulation solutions for HJT. The challenges in this process of the production process range from poor adhesion between cell and film, to water ingress, and UV-induced degradation. Wu said his company has developed solutions as high adhesion encapsulation, edge sealant and moisture resistant backsheet, to improve the bonding strength between film and TCO and overcome these concerns. He also presented an innovative UV light conversion film to convert the UV light into visible range that improves the portion of light that helps in power generation.
Moderated by TaiyangNews’ Head of Technology Shravan Chunduri, the executive panel on day 2 had panelists discussing what’s in for SHT technology today.
Forschungszentrum Jülich’s Dr. Kaining Ding reinforced the fact that since TOPCon’s production processes are closer to the current incumbent PERC, switching to the technology doesn’t burn a hole in the pocket. This continues to remain the main consideration for all manufacturers.
If HJT is to compete with TOPCon, it has to become cost-competitive. Of course, there is still a learning curve it needs to go through, but it eventually boils down to the cost per W.
However, Ding did point out that most newcomers to the solar manufacturing are seen as more interested in HJT than TOPCon. During their risk and opportunity assessments, they pick HJT primarily because they don’t have experience with other technologies and see the technology purely for its long-term growth.
Huasun’s Su Zhou argued that while wafer thickness is the most significant factor that can help bring down HJT’s cost, it is not the sole factor. The quality of silicon material used also plays its part. Metallization is another area where efforts can be made as well.
Agreeing with Ding, Maxwell’s Peter Wolf said HJT modules are preferred by those who want the highest power output, despite the cost limitation. Yet, in the short term, it is the LCOE that determines how fast it can grow vis-à-vis its peers. Next 24 months will see dynamic changes in the industry in terms of technological advancements so there may be a growth curve in HJT as well on the anvil.
It is now 2 down, 1 more to go. Day 3 of the TaiyangNews High Efficiency Solar Technologies Conference on November 25, 2022, will reflect on global solar market and cell technology trends with an interesting line of presentations from industry leaders and market experts. It will end with an interview of LONGi Green Energy Technology’s Founder and President Li Zhenguo and the company’s Vice President for Dr. Xu Xixiang regarding the company’s new solar cell world record. Registrations to the event are free and can be done here.
Day 1 of the conference on November 23, 2022 was exclusively devoted to TOPCon technology (see TaiyangNews High Efficiency Solar Technologies 2022 Event Day 1 Sees Amazing Progress For TOPCon).