Cost reduction and efficiency enhancement are the key to the sustainable development of the photovoltaic industry. With continuous efficiency improvement and cost reduction pressure, photovoltaic cell and module technologies are rapidly updated and iterated. At present, PERC batteries are quite cost-effective, but as their efficiency potential is gradually approaching the limit, it is obviously more difficult to make a breakthrough. Therefore, in order to further promote cost reduction and increase efficiency, and occupy a place in the bidding market, it is necessary to seek higher efficiency battery module technology.

From the perspective of the industry, the study pointed out that the photovoltaic power generation technology route will start the trend of iteration from P-type to N-type this year. As the most promising N-type representative, heterojunction (HJT) battery is expected to exceed 30% in limit efficiency. It can not only form stacked batteries with IBC and perovskite, but also has high efficiency, high reliability, and double-sided power generation. , Low-temperature process, thin silicon wafer application, good temperature characteristics, no LID and PID effects, etc., have attracted close attention from many photovoltaic companies at home and abroad.

Leading enterprises scrambling for layout

The iterative history of photovoltaic technology is a history of continuous cycles of innovation-elimination-upgrade-reinnovation. It is both cruel and charming. Every round of technological revolution will reshape the original competition pattern and give birth to new industry leaders.

A new round of subversive technological changes in photovoltaics will take place in the battery sector, and heterojunction will thus stand on the limelight and become one of the most popular technology routes for next-generation N-type batteries. Industry newcomers and traditional giants have entered the market one after another, greatly accelerating the cost reduction and efficiency improvement and industrialization process of heterojunction.

Throughout the country, from the early days of Aikang, State Power Investment Corporation, Jinneng Group, CIIC Power, and Caihong Group, more and more companies such as Shanxi Coal International, Risen Energy, and Tongwei have joined the heterojunction industry. camp.

According to the statistics of “Global Photovoltaic”, more than 20 companies have already deployed heterojunction, the existing production capacity planning has reached 71.9GW, and the conversion efficiency of battery mass production has already exceeded 25%.

Prior to this, Huasheng New Energy accelerated the expansion of 10GW production capacity, and LONGi repeatedly broke the world record for photoelectric conversion efficiency of heterojunction cells. Heterojunction has won the favor of many parties and massive capital support due to its technological advantages.

Data show that the Wind heterojunction battery index has increased by as much as 230% in two years. Based on the stock price after reinstatement, the stock price of one of the constituent stocks of the index, Heterojunction Equipment Co., Ltd. (300751.SZ), has soared more than 25 times since its listing. The company’s one-hour investor conference call on August 26 attracted 779 institutional investors, which shows how popular it is.

Looking overseas, REC Group, a photovoltaic module integration manufacturer, launched its latest module product – Alpha Pure-R household heterojunction module during Intersolar.

The Alpha Pure-R series of REC products adopts heterojunction (HJT) cells and G12 large-scale module design. It will provide three output powers of 410Wp, 420Wp and 430Wp, and the power guarantee period is 25 years. The module weighs 21.5kg and measures 1730x1118x30mm. REC plans to start production at its Singapore factory in August, which will double the production capacity of REC’s Alpha product line from 600MW to 1.2GW.

However, recently REC suddenly announced that it is ready to ship TOPCon to the US market. The TOPCon module model that REC is about to ship to the US market is the “N-Peak 3 Black” series, with a nominal output power of 400W and the use of n-type TOPCon technology. It is reported that it has been produced in the Singapore factory and is scheduled to be shipped in January 2023 . The change comes two months after the start of production of its innovative REC Alpha Pure-R heterojunction modules.

However, industry insiders also mentioned that REC’s TOPCon technology was upgraded in the PERC production line. Through the tunneling oxide layer passivation contact technology developed on the basis of N-type battery technology, it can be upgraded based on the existing PERC production line. However, the backside of TOPCon cells has poor light absorption, and its yield rate is generally below 95%. Mass production is very difficult and the cost is also high.

In addition, the disadvantage of TOPCon is that the process is too complicated. There are basically 9 processes in PERC; TOPCon has about 3 more links on the basis of PERC, a total of about 12 processes, mainly in the process of knot making.

The complicated process is the 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 to prepare polysilicon film combined with traditional full diffusion process; the second is LPCVD to prepare polysilicon film combined with boron expansion and ion implantation phosphorus process; the third is PECVD to prepare polysilicon film and in-situ doping process . Although PECVD is the main method at present, problems such as slow film formation speed 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%; while the yield rate of PERC cells is between 97-98%.

Compared with PERC and TOPCon, the heterojunction process has fewer steps, only four steps, namely: texture cleaning, amorphous silicon film deposition, TCO film deposition, and electrode metallization. In theory, fewer process steps can improve product yield and save some production costs, so HJT is superior to TOPCon in this respect.

Obviously, as the second-generation cell technology, TOPCon technology can be transformed on the traditional PERC production line, and the biggest advantage of heterojunction technology is its high efficiency, higher bifaciality and better compatibility with Perovskite stacks possible.

Heterojunction(HJT) has obvious advantages in cost and application value

For the development of new energy in my country, photovoltaic power generation is undoubtedly the most important part. Focusing on the interior of the photovoltaic industry, improving power generation efficiency and reducing costs has always been the core that determines the lifeline of the industry.

At present, with the continuous development of technology, the photovoltaic industry seems to have reached a new inflection point. Now the industry generally believes that the third technological change in photovoltaics is most likely to occur in the field of solar cells, and PERC batteries are currently the mainstream battery technology in the photovoltaic industry.

In order to break through the bottleneck of the industry, the market began to call for new photovoltaic technologies with higher power. On August 18, nine ministries and commissions including the Ministry of Science and Technology, the Development and Reform Commission, and the Energy Bureau issued the “Science and Technology Support Carbon Peak Carbon Neutralization Plan”, pointing out that the focus should be on “developing high-efficiency silicon-based photovoltaic cells”.

The so-called “silicon-based photovoltaic cells” generally include P-type cells and N-type cells. The former has a simple manufacturing process and low equipment construction costs, and has always been the most cost-effective battery technology route. Whether it is the mainstream aluminum back field battery (BSF) of the previous generation or the PERC battery that is currently the main force in the market, they all belong to the P-type battery sequence. But on the other hand, the current P-type battery is approaching its theoretical power generation efficiency limit, leaving little room for cost reduction and efficiency increase.

The N-type battery is enough to replace the P-type battery in the market and become the mainstream of the market. Its technology routes are many and clear, and its development is relatively mature. The photoelectric conversion efficiency of various technologies has exceeded 24%, with huge application potential and considerable commercialization space.

At present, there are three main types of N-type batteries, namely TOPCon, IBC and heterojunction. From the perspective of the industry, the mainstream of the photovoltaic market in the future will most likely emerge from these three technologies.

According to industry analysts, among the three technologies, TOPCon has the lowest barriers to early production. The biggest feature of this technology is that the production line does not need to be built separately, only the existing PERC production line needs to be modified, and the initial production cost is low. But its photoelectric conversion efficiency is low, and the current laboratory limit is 26% (ISE, double-sided contact), which is better than PERC and lower than heterojunction and IBC. In addition, the process of TOPCon is too complicated – ordinary photovoltaic cells generally only need to go through 9 production processes, while TOPCon’s process is as high as 12-13, which greatly increases the difficulty of mass production, and the yield rate is therefore extremely difficult to grasp.

As for the IBC battery, it is the one with the best power generation efficiency among all battery technologies at present, and the laboratory limit efficiency has reached 26.63%. But the technology is also the most immature, the processing cost is extremely high, the production equipment is expensive, and it is still far away from commercialization.

In contrast, the performance of heterojunction cells is more in line with market requirements, and is considered to be the most promising technology route for the next generation of mainstream cells. According to the empirical data released by CPIA, at present, compared with P-type batteries, heterojunction batteries have an absolute advantage in power generation, and the power generation per kilowatt can increase by 6-10%. The highest photoelectric conversion efficiency in the laboratory is about 26.5%, which is higher than that of PERC and TOPCon cells, and the process is the least, with only 4 steps. The production steps are highly controllable and the yield rate is the highest.

Development prospects should not be underestimated

At present, heterojunction (HJT) technology has entered the development period from the exploration and preparation period. Some photovoltaic companies that have entered the heterojunction technology track are actively expanding their production scale. Large-scale production is driving the investment in heterojunction equipment and reducing material prices. Industry cases The data are also corroborated.

According to data from a certain project, the yield per watt of heterojunction bifacial modules is 7.5% higher than that of PERC bifacial modules, and the yield per watt is 14.4% higher than that of PERC single-facial modules. Therefore, considering power generation and cost, heterojunction products already have power station application value (heterojunction LCOE and PERC components are basically close at present).

With the significant reduction in cost of localization of equipment and materials, and the increase in product supply and market, the cost of heterojunction cells is expected to reach 0.65 yuan/M by 2023.

Industry experts said that low temperature coefficient, low attenuation, high conversion efficiency, and simple process are the main advantages of N-type heterojunction technology. The structure of the heterojunction battery determines that it can generate electricity on both sides naturally. The process flow only has four steps: cleaning and texturing, amorphous silicon film deposition, conductive film deposition, and silk screen curing, which is greatly simplified compared with the PERC battery with 8 processes. In terms of technology extension, with the gradual maturity of heterojunction technology, it is expected to become a platform technology in the future, combining with perovskite to form stacked cells.

According to REC Group CEO Jan Enno Bicker, future R&D work will be entirely focused on heterojunction technology.

“We know this is one of the most promising technologies for the next few years to really improve power density and make modules more and more efficient.”

“The REC Alpha Pure-R really hits the sweet spot in terms of size, weight, power output and handling,” Bicker said. Owners can achieve higher energy independence and contribute to the global energy transition.” At the same time, in order to improve the sustainability of the products, this series of products does not use lead, which complies with RoHS standards and has less impact on the environment. REC Alpha Pure is one of very few lead-free solar modules on the market.

It is worth noting that, according to CPIA’s previous estimates, it is assumed that the global installed capacity in 2021-2025 will be 170, 225, 270, 300, and 330GW respectively, and the heterojunction penetration rate will be 5%, 12%, and 26% in 2021-2025, respectively. , 42%, 60%. It can be seen that the market prospect of heterojunction should not be underestimated.

Promoting technological iteration and developing photovoltaic module products with higher power, higher efficiency, and higher power generation are always the key for photovoltaic companies to meet the needs of the end market. In the future, more outstanding companies will continue to be driven by innovation, further increase investment in research and development of heterojunction products, realize existing technology and product updates, develop more new technologies and new products, and simultaneously improve photovoltaic cells , Photovoltaic modules and related product capacity layout to meet wider market demand and accelerate the development process of carbon neutrality.