Solar has earned its prominence due to the undeniable cost-performance ratio and the variability the technology brings to the table. For a solar panel, a key part of the final system product for the end customer, efficiency and rated power are two important performance governing parameters, more so the latter. While the industry used to rely mainly on high efficiency cell architectures for improving module power in recent times, quickly increasing and module formats of the contemporary state-of-the-art PERC cell technology have helped boost module power significantly. However, it is not without its limits, and more apparently so of late with its improvement potential PERC module efficiencies seem to have hit a plateau. As can be observed in the TaiyangNews TOP MODULES listing published monthly on our website (check latest graphs HERE), several PERC based module series with efficiencies of around 21.5% are available today. And that, without the need to adopt high efficiency cell architectures. Such architectures, however, become unavoidable when trying to breach the 21.6% level. PERC, in general, is no longer able to support module efficiencies above 21.6%. Almost all of the leading cell/module makers' commercial modules with efficiencies above 21.6% are based on high-efficiency cell architectures such as IBC, TOPCon or heterojunction (HJT). And as can be seen, when checking the tables of our ranking in recent months, the number of high-efficiency products is increasing as the global PV industry has renewed its interest in advanced cell architectures.
Among these technologies, TOPCon and HJT are currently the two mainstream high efficiency cell technologies, as two variants of IBC – the longtime efficiency champion in the commercial space developed by SunPower and an industrial-scale approach promoted by European research center ISC Konstanz – have limited followers. SunPower's IBC technology (now produced by its spin-off Maxeon) is a high-price premium product with limited range, while commercial Zebra modules, a lower-cost and efficiency IBC product, manufactured by China's SPIC, is rather new to the market. However, TOPCon and even the Zebra IBC from ISC are mainly promoted as line extensions of PERC, it is HJT with its completely different production line design that stands out. Although TOPCon is estimated to have a higher theoretical efficiency potential, HJT is the platform with the best crystalline silicon cell efficiency so far with 26.7% achieved by Kaneka back in 2017. This world record cell with a size of 79 cm2 is based on the fusion of an interdigitated back contact (IBC) cell and a HJT platform. In June 2022, LONGi reported to have achieved 26.5% power conversion efficiency for its silicon heterojunction (HJT) solar cells, on M6 (274.2 cm2) full size monocrystalline silicon wafers, a world record for 6-inch cells that comes close to Kaneka's 179 cm2 based 26.6% record for commercial size cells.
Covering the important developments in the HJT segment, TaiyangNews has published two editions of its HJT report in 2019 and 2020, and the segment as such has seen several notable developments since then. HJT is now clearly quickly marching from research to industrial scale. In China, Tongwei and Huasun have started commercial production, while several leading companies including LONGi, JA Solar and Canadian Solar are operating HJT pilot lines. In Europe, Meyer Burger and Enel also add to the success story of entering commercial production with HJT – and both are already working on expansion of their facilities. An ever-growing number of companies are evaluating or already announced plans for their entry or expansion with HJT technology. At about 80 GW, HJT still tops in terms of "expression of interest." Among those are some very serious and big corporates too. India's Reliance Industries Limited (RIL) is the latest among them. Having acquired Singapore based REC last year, RIL has ordered 4.8 GW of HJT tools from Maxwell. A little earlier, Enel Green Power announced a new 3 GW HJT production line, having secured a grant from the European Commission.
The next sign of improvement in this segment is seen in how its efficiency has progressed. The phase that HJT is in right now somewhat harkens back to the early days of PERC development. At the time, several mainstream companies were in a race to achieve record efficiencies on the commercial size, as they are in the field of HJT today. While 2020 was rather muted, as many as 6 record efficiency levels were announced in 2021, and all by big commercial vertically integrated module producers. Even equipment makers like Maxwell from China have also taken part in this efficiency progression. There are a variety of categories that top efficiencies are announced in, such as HJT on p-type, low/free indium and so on, while LONGi takes the top honors 26.5%, which it announced in June for a M6 cell (274.4 cm2), getting very close to Kaneka's overall HJT cell record but for a much smaller size of 79 cm2. Not just record efficiencies, even average efficiencies at several manufacturers exceeded 24%, though most of them are in the pilot phase (see Progress Of Heterojunction Technology).
There is also increased activity in the production equipment area with a greater number of companies developing tools for HJT. Even process consumables, notably silver pastes, are getting better and better with time, which means HJT is now getting ready for prime time on a larger scale.
This is the intro chapter of the 3rd edition of TaiyangNews' Heterojunction Technology 2022 report, which provides an overview on the most recent HJT developments as the technology is entering the GW scale production level and can be accessed free of charge here.
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