Backing back contact

#WhoisAiko from pv magazine Global 2023-05

Backing back contact

23.6%?is the conversion efficiency of Aiko’s 54-cell, M10- wafer ABC module

While most manufacturers embrace tunnel oxide passivated contact (TOPCon) solar for higher efficiency, Aiko Solar is developing all back contact (ABC) technology, as the company’s director of products, Cris Lu, told pv?magazine at the PV Expo Japan trade show.

Aiko Solar is one of a few manufacturers investigating back contact technology at the moment – can you tell us a bit about your progress in this area?

We estimate that this year the entire PV market will amount to between 320 GW and 350 GW, and that back contact technologies will take up 5% to 10% of this. On the market side, it really depends on how we and our competitors who are also working on back contact technologies, are promoting ourselves and influencing industry trends. So far, the ABC cell has taken us three to four years to develop. The technology is another innovation on top of back contact. In 2021, we had achieved 25.5% efficiency in mass production and last year we were able to push that up to 26.2%. This year we have already reached 26.5%. So you can see by these numbers that development is proceeding smoothly. In module efficiency, we have reached 23.6%. For a 54-cell, M10 ABC module, our average power is between 450 W and 460 W, and for the 72-cell module it is around 610 W. And, according to our development plans, by the second half of this year we expect to increase this further. Back contact technology is an excellent platform for development, and one where the market expects to see improved products. In the coming years, we are confident that we will be able to achieve ABC cell efficiencies of 27% and higher.

How do production costs for ABC cells compare to passivated emitter, rear contact (PERC) cells or TOPCon or heterojunction (HJT) cells, for example?

Compared with PERC today, we do have considerably higher costs for ABC. The process for back contact cells is more complex and takes a lot longer – if we take a PERC cell from the very beginning, production time is about eight to nine hours. For our ABC cell, the total time is about 20 hours. As for TOPCon and HJT, we don’t have a specific analysis to compare the costs. We do see some differences, but we are confident that with our high module efficiency we can be competitive. In past years, the development of the PV industry has been very focused on reducing costs and now the industry is quite cost effective. Today, more and more companies are realizing that they need to invest more in technology to increase the efficiency rather than simply reducing the cost. We strongly believe that back contact and our ABC technology are the most competitive among all those that different players are focusing on.

When it comes to bringing down the cost of back contact technology, what are the specific things that need to change?

We have calculated that every 1% increase in module efficiency can reduce the electricity cost by 5% to 7%. Therefore, at the current stage, improving the conversion efficiency of ABC cell and modules through technology is what makes us technologically more competitive. Eliminating silver is another focus for us. This is a big part of the cell cost and as the PV industry enters the era of terawatt-scale production, it will become difficult for many companies to secure a supply of silver. So we want to remove it from our production and we are investigating other materials that will bring down the cost. We also find that cutting silver out of our cells can increase their reliability. Silver processing requires high temperatures, and the metallization lines can be broken very easily. When we switch to other, more stable metals, we find that the lines aren’t as easy to break and that’s another reason why we want to remove silver.

And is it copper that you are investigating as a replacement for silver?

We have made significant achievements in developing silver-free ABC cells. We have our own unique technology. We can’t share any more information at this stage. Which markets will you initially target with back contact products? Now we’re focused on the distributed markets and our attention is on rooftop installations. As we improve the technology, we’ll focus more on large-scale projects as well. In the distributed-generation (DG) rooftop market, customers want the highest generation from their limited space and the only way to compete is to increase efficiency, and that’s why we are really confident about the ABC technology. Aesthetics are important in this market as well and, based on market feedback, especially from Europe and Japan, we have found that users are happy to pay more to buy all-black modules. Without grid lines on the front, our module is especially suited to this – making it a better fit for the market need.

Is back contact now Aiko’s main focus, or will you continue to work on other cell technology as well?

Aiko is a big player and we expect to maintain our position among the biggest cell manufacturers, in production capacity terms. We have investments in research and development for a lot of different cell and module technologies and aim to respond to market requirements. In 2022, our entire R&D investment was nearly CNY 1.4 billion ($203 million), almost 4% of our entire revenue for the year. Also, 23% of our global employees, around 2,100 people, are employed in research and development across two different centers, one in Freiburg, Germany, where they focus largely on n-type technologies, and one close to our headquarters in China, which is more focused on further developing the ABC technology.

“ We have made significant achievements in developing silver-free ABC cells” Cris Lu

Interview by Mark Hutchins