This year, the expansion process of HJT and TOPCon has accelerated, and leading enterprises have increased the layout of N-type battery technology, what is the technical development trend of photovoltaic cells in the future? The following Wall Street Insights and Wisdom Research takes you to deeply sort out the characteristics of the photovoltaic cell industry and how will it evolve in the future?
Highlights of this article:
1. Review the development process of photovoltaic cells
2. Analyze the respective characteristics, advantages and disadvantages of TOPCon and HJT and the possibility of future battery development
3. Track the current industrial dynamics of N-type batteries, and predict the short-term and medium- and long-term battery routes
Photovoltaic cells in the past and this life---- the end of the P-type era, the beginning of the N-type era
The photovoltaic cell industry belongs to the middle reaches of the photovoltaic industry chain, which is made of silicon wafers through cleaning, fleece and other steps. Photovoltaic panels generate voltage and current under light, which in turn enables photovoltaic power generation, which is essentially similar to low-end semiconductor manufacturing.
According to the different raw materials and battery preparation technology, photovoltaic cells can be divided into P-type cells and N-type cells. P-type silicon wafers are made by doping boron elements in silicon materials; N-type silicon wafers are made by doping phosphorus elements in silicon materials. P-type battery preparation techniques include traditional AL-BSF (aluminum backfield) and PERC technology. There are many N-type battery preparation technologies, including PERT/PERL, TOPCon, IBC and HJT (heterojunction).
The development of photovoltaic cells in China began to be traced back to the 1950s, in 1958 China developed the first silicon monocrystalline, in 1998 began to pay real attention to solar power generation, that year planned to build a set of 3MW polycrystalline silicon cells and application system demonstration projects. In 2001, Wuxi Suntech established a 10MW solar cell production line successfully, which is the official opening of China's solar cell field. Subsequently, after 6 years of development, in 2007 China became the country that produced the most solar cells.
2015 is the first year of technological change for photovoltaic cells. Before 2015 BSF batteries were mainstream, accounting for 90% of the total market. In 2015, PERC completed commercial verification, and the battery mass production efficiency exceeded the BSF bottleneck by 20% for the first time, officially entering the expansion stage. In the following two years, with the advancement of PERC technology, the improvement of efficiency, and the decline in non-silicon costs, the economic benefits of PERC batteries were reflected. In 2018, the PERC battery market share reached 33%, followed by explosive growth in production capacity, and by 2020, the market share has increased to 87%, basically beating the BSF battery, but the efficiency limit of the PERC battery is 24.5%, and the conversion efficiency of the PERC battery is close to the limit, so in order to reduce costs and increase efficiency, battery companies must once again seek technological breakthroughs.
2021 is the inflection point of the battery technology change, the only main theme of the photovoltaic industry is to reduce costs and increase efficiency, N-type batteries due to high conversion efficiency, began to gradually appear on the stage, is accepted by people. According to ISFH data, the theoretical limit efficiency of PERC, HJT and TOPCon batteries is 24.5%, 27.5%, and 28.7%, respectively.
Overall, before 2017, aluminum backfield BSF batteries dominated, and PERC batteries have come close to completely replacing aluminum backfield batteries since 2017. However, due to the current PERC battery has approached the theoretical limit efficiency of 24.5%, the improvement space is limited. After 2021, N-type batteries began to develop rapidly, dominated by the two routes of TOPCon and HJT, which are currently in the early stages of large-scale commercialization. Future potential technology routes also include HBC and perovskite stacked batteries, which are equivalent to upgrades after combining with HJT, so the conversion efficiency can achieve another leap.
HJT "PK" TOPCon, what are the advantages and disadvantages?
Although there are many kinds of N-type batteries, only TOPCon and HJT are currently commercially popularized. Let's focus on what are the characteristics of TOPcon and HJT batteries:
1, HJT is more concise than the TOPCon process
PERC cells produce a large number of low-daughter composite centers due to the direct contact between the metal electrodes and the silicon substrate, which has a negative impact on efficiency. TOPCon batteries are prepared by preparing an ultra-thin layer of tunneling oxide layer and highly doped polycrystalline silicon film in the metal electrode contact area to form a passivation contact structure, thereby improving the power generation efficiency.
Pictured: TOPCon and HJT batteries
Source: Collation of publicly available information
The disadvantage of TOPCon is that the process is too complicated. The perc process is basically 9; TOPCon has about 3 more links on the basis of PERC, a total of about 12 processes, mainly to increase the link in the production of knots.
Complicated processes are the pain points of TOPCon, and the current technical routes are not uniform, and multiple technical routes are parallel. There are three main types, the first is LPCVD preparation of polycrystalline silicon film combined with the traditional full diffusion process; the second is LPCVD preparation of polycrystalline silicon film combined with amplified boron and ion implantation phosphorus process; the third is PECVD preparation of polycrystalline silicon film and in situ doping process. At present, although PECVD is the mainstay, problems such as slow film formation are still pain points. Complicated processes will bring yield disadvantages, coupled with the increased process technology route is not uniform and difficult. This results in an overall TOPCon yield of 93-95%; while the PERC battery yield is between 97-98%.
HJT batteries are also known as heterojunction batteries, and the substrate type is N-type silicon wafers. In 1990, Sanyo Company of Japan successfully developed and applied for a patent, and in 2015, the protection period of Sanyo patent expired, and HJT technology began to be fully promoted. Compared with PERC and TOPCon, HJT has fewer steps than PERC and TOPCon processes, with only four steps, namely: fleece cleaning, amorphous silicon film deposition, TCO film deposition, and electrode metallization. Theoretically, few process steps can improve product yield and save some production costs, so HJT is superior to TOPCon in this regard.
Figure: ToPcon & HJT route
Source: Publicly available information
2. Compared with TOPCon, HJT has higher short-term costs and large room for cost reduction in the medium and long term
HJT is more costly in the short term than TOPCon because the equipment cannot be retrofitted on PERC, but new. The biggest attraction of TOPCon is that it can retain and utilize the traditional P-type battery equipment process to the greatest extent, and can be upgraded on the traditional PERC equipment, and the cost of single GW transformation is about 0.6-0.8 billion yuan. Therefore, traditional enterprises such as LONGi, Jinko and TRW are relatively more active in the layout of TOPCon. TOPCon's main new equipment is LPCVD/PECVD equipment for amorphous silicon deposition and coating equipment.
At present, the investment in PERC single GW equipment is 120-150 million yuan; TOPCon is about 200-250 million yuan; and the investment in HJT is about 400-450 million yuan.
Why is the cost of HJT so high? The first is because of the high cost of equipment. In particular, PEVCD and PVD equipment mainly rely on imports; the second reason is because of the high cost of silver paste. HJT uses low-temperature silver paste, while PERC and TOPCon use high-temperature silver paste. Due to the difficulty of the low-temperature silver paste production process and the need for cold chain transportation, the price is usually 10-20% higher than that of conventional silver paste.
So the biggest drawback of HJT at present is that the cost is higher than THATCon. However, in the future, with the further maturity of the process, the downstream demand is released, the localization process is accelerated, the low-temperature silver paste will gradually be localized, and the cost is expected to continue to decline, and the cost of low-temperature silver paste in 2019 is 0.17 yuan / W, and it is expected to drop to 0.06 yuan / W in 2025.
3. HJT has a broader space for efficiency
Theoretically, the conversion efficiency limit of HJT is 27.5%-29%. Mainly because it can form a laminated battery with perovskite batteries and then achieve an efficiency of 29%; and TOPCon technology is difficult to form a stack with perovskite batteries, so in the short term, TOPCon can be used to follow the current production line, the cost of transformation is low, so that it has certain advantages, but in the medium term, the cost reduction and efficiency path of TOPCon are not as clear as HJT. Therefore, the current mainstream of the N-type battery market is more inclined to the HJT route.
BOTH TOPCon and HJT expansions are accelerating, whose era will it be?
At present, the mainstream view in the industry is that "TOPCon wins in the present, and HJT wins in the future". Looking at the situation this year, the N-type technology routes represented by TOPCon and HJT have been successively broken through this year, and the industrialization process has continued to accelerate.
According to PV Infolink data, the battery production capacity is expected to be 454/549GW in 2021/2022, of which the N-type cell capacity is 25/45GW respectively.
TOPCon can have better compatibility with the PERC production line, so the old players in the industry are more willing to lay out TOPCon technology, and the main domestic layout of TOPCon companies are LONGi, Zhonglai, Jinko, Trina Solar, Oriental Risheng and so on. At present, the highest laboratory conversion efficiency announced by TOPCon is 25.4% announced by JinkoSolar on October 13, 2021; from the perspective of the progress of the layout, Jolywood is one of the earliest enterprises to lay out the TOPCon battery, and the average conversion efficiency of its TOPCon battery mass production batch is 24.2%, and some products reach 24.5%, which is in the leading position in the industry. Battery capacity construction, according to PVInfoLink statistics, TOPCon's production capacity will accelerate in the future, in 2022 the industry's TOPCon production capacity is expected to exceed 40GW, is expected to reach the end of 2023, will reach a level close to 80GW. However, due to its variety of technical routes, although the most mature at present is the LPCVD route, but overall the problem of technical routes is an important risk point restricting the mass production of TOPCon.
Chart: TOPCon expansion (incomplete statistics)
HJT is a technology route independent of PERC and TOPCon, and it is also the most concerned battery technology route in the industry at present. HJT is more aggressive than TOPCon, as new players are more inclined to layout HJT because new players do not have the baggage of old PERC equipment. In terms of conversion efficiency, LONGi announced on October 28 that its heterojunction cell conversion efficiency was as high as 26.3% after being tested by the Hamelin Solar Energy Research Institute (ISFH) in Germany, which is the highest conversion efficiency in the laboratory. The conversion efficiency of mass production has reached a maximum of 25.31%. In the second half of this year, the bidding of HJT production lines began to accelerate, the pace of expansion was significantly accelerated, and many battery factories signed equipment purchase agreements with equipment manufacturers, and the landing speed is expected to accelerate. Up to now, the planned capacity of HJT worldwide has exceeded 100GW.
Figure: HJT capacity layout (incomplete statistics)
Source: Company announcements, public information collation
IBC battery is also as a kind of N-type battery, compared to HJT and TOPCon The current layout of the enterprise is not much, IBC battery because it is the excellent structure of fork finger back contact, so it is the highest efficiency in the current battery technology, the average efficiency can reach more than 25%, but because of its disadvantage is that the process is more complex, more difficult, the cost is higher, so short-term mass production will have certain difficulties, but why many companies are in the layout of research and development? Mainly because in the long run, it has potential in the superposition process, such as it can be combined with HJT, prepared into ANHBC battery, which can continue to improve efficiency to more than 26%, so compared to TOPCon and HJT, the layout of IBC is more about the layout of the future. In June this year, Aixu launched the latest N-type ABC battery new products, and its layout has two production capacities, one is the 6.5GWN battery production base planned to be built in Zhuhai in 2022, and the second is the 2GW base in Zhejiang.
Wall Street Insight Research believes that in the short term, TOPCon may be more dominant, because many battery companies are PERC production lines, and the cost of technological transformation and upgrading is lower than that of new construction. However, due to the uncertainty of the TOPCon technical route, it has also brought certain difficulties to mass production, so although the short-term cost performance is dominant, it is not as good as HJT in the medium and long term. HJT is currently a relatively more recognized technical route in the industry, and its biggest pain point is the cost problem, one is the cost of new equipment; the other is the cost of silver paste. However, with the localization of low-temperature silver paste and equipment, the cost will be greatly reduced; at the same time, the advantage of HJT is that it can be combined with IBC batteries to form HBC batteries; it can also be combined with compound batteries such as perovskites to form laminated batteries, which can increase the efficiency to 27%-29%, which are the reasons why the industry is more optimistic about HJT.
But for 2022, Wall Street insight research believes that the iteration of photovoltaic cell technology will accelerate, TOPCon and HJT will still develop in parallel, the tender volume is expected to be significantly higher than this year, there is no problem of who is absolutely dominant in the short term, but because the short-term HJT cost is still high, it is difficult to show an overwhelming advantage over TOPCon, so as far as next year, the mass production speed of HJT is not as likely as TOCon.
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