This year, the expansion of HJT and TOPCon has accelerated, and leading companies have increased their deployment of N-type photovoltaic cells technology. What is the future development trend of photovoltaic battery technology? The following Wall Street knowledge and wisdom research will take you to deeply comb the characteristics of the photovoltaic cell industry and how will it evolve in the future?

Highlights of this article:

1. Review the development history 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 industry trends of N-type batteries, and predict short-term and mid- to long-term battery routes

The past and present of photovoltaic cells-the end of the P-type era and the start of the N-type era
The photovoltaic cell industry belongs to the middle reaches of the photovoltaic industry chain, and is made from silicon wafers through cleaning and texturing steps. Photovoltaic panels generate voltage and current under light to achieve photovoltaic power generation, which is essentially similar to low-end semiconductor manufacturing.

According to different raw materials and battery preparation technology, photovoltaic cells can be divided into P-type batteries and N-type batteries. P-type silicon wafer is made by doping boron in silicon material; N-type silicon wafer is made by doping phosphorus element in silicon material. P-type battery preparation technology has traditional AL-BSF (aluminum back field) and PERC technology. There are many manufacturing technologies for N-type batteries, including PERT/PERL, TOPCon, IBC, and HJT (heterojunction).

The development of photovoltaic cells in my country dates back to the 1950s. In 1958, my country developed the first monocrystalline silicon. In 1998, it began to pay attention to solar power generation in a real sense. A set of 3MW polycrystalline silicon cells and application system demonstrations were planned that year. project. In 2001, Suntech in Wuxi succeeded in establishing a 10MW solar cell production line, which is regarded as my country’s official start in the field of solar cells. After 6 years of development, my country became the country with the most solar cells in 2007.

2015 is the first year of technological change in photovoltaic cells. BSF batteries were the mainstream before 2015, accounting for 90% of the total market. In 2015, PERC completed the commercialization verification, and the battery mass production efficiency exceeded the BSF bottleneck by 20% for the first time, and officially entered the expansion stage. In the following two years, with the advancement of PERC technology, the improvement of efficiency, and the decline of non-silicon costs, the economic benefits of PERC cells have been reflected. The PERC battery market share reached 33% in 2018, and then the production capacity has exploded. By 2020, the market share has increased to 87%, which has basically beaten the BSF battery, but the efficiency limit of the PERC battery is 24.5%. The current conversion efficiency of the PERC battery Already close to the limit, in order to reduce costs and increase efficiency, battery companies must once again seek technological breakthroughs.

2021 is the turning point of the battery technology revolution. The only main theme of the photovoltaic industry is to reduce costs and increase efficiency. Due to the high conversion efficiency of N-type batteries, they have begun to gradually take the stage and are accepted by people. According to ISFH data, the theoretical limit efficiencies of PERC, HJT, and TOPCon batteries are 24.5%, 27.5%, and 28.7%, respectively.

On the whole, aluminum backfield BSF batteries dominated the mainstream before 2017, and PERC batteries have almost completely replaced aluminum backfield batteries since 2017. However, since PERC batteries have approached the theoretical limit efficiency of 24.5%, the room for improvement is limited. After 2021, N-type batteries will begin to develop rapidly, with TOPCon and HJT as the leading route, both of which are currently in the early stages of large-scale commercialization. The future potential technology route also includes HBC and perovskite tandem cells, which are equivalent to the upgrade after combining with HJT, so the conversion efficiency can achieve another leap.

What are the advantages and disadvantages of HJT “PK” TOPCon?
Although there are many types of N-type batteries, only TOPCon and HJT are commercially popular. The following will focus on the characteristics of TOPcon and HJT batteries:

1. HJT is more concise than TOPCon process

Because the metal electrode is in direct contact with the silicon substrate, the PERC battery will produce a large number of minority carrier recombination centers, which will have a negative impact on the efficiency. The TOPCon battery is to prepare an ultra-thin tunnel oxide layer and a highly doped polysilicon film in the metal electrode contact area to form a passivation contact structure, thereby improving power generation efficiency.

The disadvantage of TOPCon is that the process is too complicated. There are basically 9 processes in PERC; TOPCon has about 3 more processes on the basis of PERC, with a total of about 12 processes, mainly to increase the link in the production process.

The complexity of the process is a pain point of TOPCon, and the current technical route is not unified, and multiple technical routes are parallel. There are three main types, the first is LPCVD preparation of polysilicon film combined with the traditional full diffusion process; the second is LPCVD preparation of polysilicon film combined with boron expansion and ion implantation of phosphorus; the third is PECVD preparation of polysilicon film and in-situ doping process . Although PECVD is currently the mainstay, problems such as slow film formation are still pain points. The complicated process will bring the disadvantage of yield rate, and the added process technical route is not uniform and difficult. As a result, the overall yield rate of TOPCon is 93-95%; and the yield rate of PERC batteries is between 97-98%.

HJT battery is also called heterojunction battery, the substrate type is N-type silicon wafer. In 1990, Japan’s Sanyo Company successfully developed and applied for a patent. In 2015, the Sanyo patent protection period expired, and the HJT technology began to be fully promoted. Compared with PERC and TOPCon, HJT has fewer process steps, with only four steps, namely: texturing cleaning, amorphous silicon film deposition, TCO film deposition, and electrode metallization. In theory, fewer process steps can improve product yield and save part of the production cost, so HJT is better than TOPCon in this respect.


2. Compared with TOPCon, HJT has a higher short-term cost, and the medium and long-term cost reduction space is large

Compared with TOPCon, HJT has a higher short-term cost because the equipment cannot be modified on PERC, but new ones must be installed. The biggest attraction of TOPCon is that it can retain and utilize the traditional P-type battery equipment manufacturing process to the utmost extent. It can be upgraded on traditional PERC equipment, and the cost of a single GW transformation is about 60-80 million yuan. Therefore, traditional companies such as Longi, Jinko, and Trina 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, PERC’s single GW equipment investment is 120-150 million yuan; TOPCon is about 200-250 million yuan; HJT investment is about 4-450 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 relies on imports; the second is because of the high cost of silver paste. HJT uses low temperature silver paste, while PERC and TOPCon both use high temperature silver paste. Due to the difficult production process of low-temperature silver paste and the need for cold chain transportation, the price is usually 10-20% higher than that of conventional silver paste.

So currently, the biggest disadvantage of HJT is that the cost is higher than that of TOPCon. However, in the future, as the process matures, downstream demand increases, and the process of localization accelerates, low-temperature silver paste will gradually be localized, and the cost is expected to continue to decline. In 2019, the cost of low-temperature silver paste is 0.17 yuan/W, and it is expected to drop to 0.06 yuan/W in 2025. W.

3. HJT has a broader space for efficiency gains

In theory, the conversion efficiency of HJT is limited to 27.5%-29%. Mainly because it can form a stacked cell with a perovskite battery to achieve an efficiency of 29%; while TOPCon technology is difficult to form a stacked layer with a perovskite battery, so in the short term, TOPCon can continue to use the current production line and the cost of transformation is relatively low. , So that it has certain advantages, but in the medium term, TOPCon’s cost reduction and efficiency increase path is not as clear as HJT. Therefore, the mainstream of the current N-type battery market is more inclined to the HJT route.

Both TOPCon and HJT have accelerated their production expansion. Whose era will it be in the future?
The current industry mainstream view is that “TOPCon wins in the present, while HJT wins in the future.” Looking at the situation this year, the N-type technical routes represented by TOPCon and HJT have successively achieved breakthroughs this year, and the industrialization process has continued to accelerate.

According to PV Infolink data, it is estimated that the cell production capacity in 2021/2022 will be 454/549GW, of which the N-type cell production capacity will be 25/45GW respectively.

Because TOPCon can have better compatibility with PERC production line, old players in the industry are more willing to deploy TOPCon technology. The main domestic companies that deploy TOPCon include Longi, Zhonglai, Jinko, Trina Solar, and Oriental Risen. 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 layout progress, Zhonglai is one of the first companies to deploy TOPCon batteries, and currently its TOPCon batteries are mass-produced The average batch conversion efficiency is 24.2%, and some products reach 24.5%, leading the industry. According to PVInfoLink’s statistics, TOPCon’s production capacity will accelerate in the future. The industry-wide TOPCon production capacity is expected to exceed 40GW in 2022, and it is expected to reach a level of close to 80GW by the end of 2023. However, due to its various technical routes, although the most mature one is the LPCVD route, the overall technical route is an important risk point that restricts the mass production of TOPCon.

HJT is a technical route independent of PERC and TOPCon, and is currently the most concerned battery technical route in the industry. Compared with TOPCon, HJT has a more active layout for new players, because new players do not have the baggage of the old PERC equipment, so they are more inclined to deploy HJT. In terms of conversion efficiency, Longi announced on October 28 that, tested by the German Hamelin Institute of Solar Energy (ISFH), the conversion efficiency of its heterojunction cell is as high as 26.3%, which is currently the highest conversion efficiency in the laboratory. The conversion efficiency of mass production is currently up to 25.31%. In the second half of this year, the HJT production line bidding has been accelerated, and the pace of expansion has been significantly accelerated. Many battery factories have signed equipment purchase agreements with equipment manufacturers, and the pace of landing is expected to accelerate. Up to now, the planned production capacity of HJT globally has exceeded 100GW.

IBC battery is also a type of N-type battery. Compared with HJT and TOPCon, there are not many companies currently deployed. IBC battery is the most efficient among current battery technologies because of its excellent structure with interdigital back contact. , The average efficiency can reach more than 25%, but due to its disadvantages that the process is more complicated, more difficult, and more costly, short-term mass production will have certain difficulties, but why many companies are deploying research and development? Mainly because it has potential in the stacking process in the long run. For example, it can be combined with HJT to prepare HBC cells, which can continue to increase the efficiency to more than 26%. Therefore, compared with TOPCon and HJT, the layout of IBC is more layout. future. The main domestic companies that are currently deploying IBC are Aishu, SUNPOWER, etc. In June this year, Aishu launched the latest N-type ABC battery new product. It has two production capacities. One is the 6.5GWN battery production base planned to be built in Zhuhai in 2022. The second is the 2GW base in Zhejiang.

Wall Street’s knowledge and wisdom research believes that TOPCon may be more dominant in the short term, 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 TOPCon’s technical route, it also brings certain difficulties to mass production. Therefore, although the price is superior in the short term, 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. Its biggest pain point is cost. 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 Increasing the efficiency to 27%-29%, these characteristics are the reasons why the industry is more optimistic about HJT.

But for 2022, Wall Street’s knowledge and wisdom research believes that the iteration of photovoltaic cell technology will accelerate, TOPCon and HJT will continue to develop in parallel, and the bidding volume is expected to be substantially larger than this year. In the short term, there is no question of who is dominant. However, due to short-term In terms of the high cost of HJT, it is difficult to show an overwhelming advantage over TOPCon. Therefore, the mass production speed of HJT is likely to be inferior to TOPCon next year.