The 3rd and the final day of TaiyangNews High Efficiency Solar Technologies Conference on December 16, 2021 focused on TOPCon technology that's considered as one of the possible contenders—apart from HJT—to take over the mantle from PERC sometime in the future. In fact, TOPCon is generally considered as the line of extension of PERC in pursuit of higher efficiencies.
On day 2, the event had focused on the potential, challenges and technological outlook of heterojunction (HJT) solar cell technology (see Day 2: High Efficiency Solar Technologies).
TaiyangNews Head of Technology, Shravan Chunduri presented an overview of TOPCon technology developments, summarizing our latest TOPCon Solar Technology 2021 Report that was first launched in Chinese on December 7, 2021 during the recently concluded CSPV conference in China.
Touted as the natural successor to PERC, Chunduri found TOPCon as currently at the same development level as PERC was during its inception. It has a higher theoretical efficiency potential at 28.7%, that's even higher than HJT's 27.5%. However, TOPCon still faces some challenges in terms of application methods for applying tunneling oxide and even polysilicon layer doesn't come out that clear. Nearly every well-known deposition technology in PV such as PECVD, PVD. PEALD and LPCVD are currently under evaluation, while the latter has won most of the followers, at least during these early days. However, it is yet to be ascertained which mainstream deposition technology works best for TOPCon, Chunduri said, and of course the high use of silver, almost double that of PERC, is another disadvantage.
At the same time, TOPCon needs to fend off competition from PERC that continues to get better with all its high advancements, especially the rapid introduction of larger wafer formats in the space.
The report – in English and Chinese – is available for free download here.
As PERC cell technology reaches its peak efficiency limits, one obvious advantage of TOPCon as a possible contender is of course the similarity of production processes which means existing PERC equipment can be used to produce TOPCon as well, providing a major cost benefit for manufacturers compared to HJT cell technology. While the Managing Director of Advanced Cell Concepts and Member of Executive Committee ISC Konstanz, Dr. Radovan Kopecek believes PERC will continue to rule the market for next 4-5 years, manufacturers will be gearing up to shift to TOPCon.
He singled out India—one of the largest solar markets in the world now and in the near future—where due to government incentives under Production Linked Incentive (PLI) scheme, companies as Reliance Industries Limited, Tata Power, Adani, Shirdi Sai Electricals and Avaada Energy are set to undertake GW level manufacturing. While HJT is on their radar, Kopecek believes Indian companies are likely to go for PERC with possibility to move to TOPCon.
Kopecek has also provided details of ISC's TOPCon process called TOUCAN, which stands for Tunnel Oxide Under ContActs on N-type. The research center is mainly focusing on the PECVD deposition technology for applying the TOPCon structure on rear side of the deposition technology.
Nonetheless, going forward Kopecek believes all N-type wafer-based technologies, or nPV as HJT, IBC and TOPCon, will become the new 'emperor' of energy markets from 2025 onward.
A major proponent of industrial scale TOPCon through its flagship brand Tiger Neo, JinkoSolar's Senior Global Product Manager Leo Yu voted for it brings cost benefits with higher efficiency limits. According to Yu, HJT is too premature a technology to become mainstream anytime soon, while the advantages of TOPCon can already be realized for the final module product level. Enhanced reliability, low temperature coefficient of -0.30%/oC, high bifaciality of 85% lead to an overall gain above 3% for energy generation. Yu also presented an LOCE analysis for Tiger Neo modules, which estimated to favor a reduction of 1.18% in BOS costs, a 5.31% gain in IRR and finally reducing the LCOE by 6%. .
JinkoSolar said its Tiger Neo will be ready for mass production in early 2022 with capacity reaching 10 GW by the end of 2022.
Citing the same economics was Astronergy/Chint Solar's Cell R&D Deputy Director Sheng He who thinks over the next 5 years the N-type cell will mainly be TOPCon and HJT, but with advantage TOPCon. At the same time, N-type TOPCon has lower degradation, higher efficiency and a higher bifacial coefficient than PERC.
Under Phase III of its Haining production facility in China, Astronergy plans to realize 6 GW TOPCon module capacity in Q1/2022 and 2 GW Topcon cell production capacity in Q2/2022.
The pioneer in manufacturing of TOPCon technology that has been present in the space since 2019, Jolywood's Cell R&D Director Du Zheren aims to continue working on improving its efficiency level. Jolywood, for the first time has revealed that its PAPAID technology backing its J-TOPCon 2.0 that achieved 24.5% efficiency is based on PVD. In addition to providing several comparisons between PVD and other contemporary deposition technologies, the company presented its efficiency roadmap to realize between 25.5% to 27.0% efficiency for J-TOPCon 3.0 between 2021 and 2025.
Zheren added, "We will also develop a new cell structure aiming for hybrid TOPCon and IBC as J-TBC with 26.0% to 28.0% efficiency between 2021 and 2025. From 2024 onwards, we will also explore J-Tandem technology reaching up to 28% efficiency using IBC and perovskite technologies." When it comes to commercial products, Jolywood is mainly offering three module classes with power ratings of 430 W, 570 W and 700 W based on 182 mm size for the first two and 210 mm for the third product.
Ireland based solar equipment provider Nines Photovoltaics CTO Laurent Clochard presented his company's Atmospheric Dry Etching (ADE) technology that it is working to bring to the market for TOPCon solar cells. One of its solutions has been bought by Germany's largest solar institute Fraunhofer ISE.
As the name suggests, ADE introduces dry etching solution using F2, which Clochard underlined is the only fluorine containing gas with zero global warming potential. It would enable the industry to move away from a wet etching process, saving water thus bringing in sustainability angle. It works without the limitations of plasma or vacuum, leading to high throughput production of cells. Clochard stressed that it can be easily be used for upcoming cell technologies as well.
The tool has a very special application in TOPCon to remove the parasitic deposition of polysilicon from the front side. In fact, irrespective of the deposition technologies wraparound is inevitable, while the difference is if it is partial or full. The newly developed tool works for all kinds wraparounds.
Chinese metallization supplier Solamet Electronic Materials CTO Qije Guo shared technical challenges and solutions for metallization of high efficiency N-type TOPCon solar cells in his presentation. Solarmet has been a well known brand of metallization pastes from DuPont for many years. Recently, DuPont sold this metallization business to Jiangsu Suote Electronic Materials Co., Ltd. The division is now referred as Solamet.
With P-type PERC as the benchmark in terms of cost effectiveness and efficiency levels, metallization paste for N-type TOPCon needs to be optimized to work with deposition process. Guo highlighted several opportunities in new metallization paste innovations to help this cell technology realize higher cell efficiency and lower cost manufacturing. He believes for this to happen, metallization paste providers need to work closely with cell makers for the former to be able to provide customized solutions.
Guo emphasized that aluminum is the key ingredient to contact the boron doped emitter of the TOPCon cell, and improvements in Al/Ag paste such as composition design of glass frit and selection of aluminum powder, and a corresponding vehicle system can deliver significant gains in cell efficiencies.
Executive Panel
Moderated by TaiyangNews' Shravan Chunduri, the executive panel had panelists quite in agreement about TOPCon production achieving anywhere between 40 GW to 50 GW capacity by the end of 2022, despite not being as competitive as already established PERC. JinkoSolar's Leo Yu is confident that between 2023 and 2024, TOPCon will have more than 100 GW global production capacity.
On improving prospects for TOPCon, Dr. Radovan Kopecek of ISC Konstanz argues it is the PECVD equipment that needs to get better. Work on other aspects can continue to be undertaken in the future, the tool however remains primary consideration as it would ensure a high-quality product.
Even though the company is invested into TOPCon, Jolywood's Du Zheren was more accepting towards HJT and IBC saying solar cell makers learn from all technologies and that progress of one helps make the other better.
Solamet Electronic Materials Qije Guo admitted that there is room to improve metallization to give more power to TOPCon. Silver consumption needs to be reduced which will be the main differentiator, but till that happens manufacturers will continue making incremental reductions. Yet the fact remains that this technology is a natural upgrade to PERC.
Day 1 of the conference was dedicated to PERC where participants agreed that the world needs to reduce its dependence on China by establishing local supply chains to further bring down costs for PERC (see Day 1: High Efficiency Solar Technologies).
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