It has been nearly 70 years since the first photovoltaic cell was born, and by 2019, monocrystalline PERC cells will be the mainstream technology in the PV industry, with their good photoelectric conversion efficiency performance becoming a key factor in driving solar power to "parity" with traditional energy sources. However, the current industry PERC cell mass production efficiency has generally exceeded 23%, getting closer to its theoretical limit of about 24.5%, and laboratory records have not been broken for a long time. Therefore, the industry has focused on the development of the new generation of mainstream battery technology, and the new generation of battery technology of major leading companies will be introduced to the market one after another during the year, with different routes.

Mainstream high-efficiency PERC cells use a variety of surface passivation methods. N-type TOPCon and HJT are the most popular emerging high-efficiency cell technologies in recent years, but the main problem of industrialization is the high cost and insufficient economy. Since this year, the leading companies in module integration have started large-scale production and expansion of the former, marking the "first year" of mass production of N-type technology cells, while the mass production of the latter is also accelerating.

TOPCon cells are the emerging representative of passivated contact technology and are more compatible with existing production lines. Even if only backside passivation is applied, the theoretical efficiency of TOPCon cells can still reach 27.1%. From the perspective of laboratory research and development, leading companies and famous research institutions in the industry have been able to develop TOPCon cell efficiency to more than 25% in recent years, and this year, Trina and JinkoSolar have set new records for large-area cells one after another, which can now reach 25.7%. level.

The certain structural similarity between TOPCon and PERC cells also brings about compatibility in equipment and processes. The front side of the former and the back side of the latter have the same coating and metallization method, and both sides have the same silicon nitride reverse passivation layer on the outermost side, as well as the same cleaning and fleece production process in the front channel. The compatibility of the production line is an important advantage of TOPCon cells in industrialization, especially in the current industry where there is a large amount of stock PERC capacity, which only requires upgrading the production line and the investment is much smaller than the new production line, so the original enterprises have more incentive to invest and breakthrough in technology. The advantages and potential of TOPCon batteries have attracted a large number of enterprises to invest in industrial R&D. At present, the industry is generally dominated by the original senior enterprises, but there are also some new enterprises that have invested heavily and continue to make important breakthroughs.

At present, the R&D efficiency of leading companies in the industry has reached over 25%, and the efficiency of mass production lines has basically exceeded 24.5%. In terms of production capacity, according to our statistics, there are about 183GW of new production capacity under construction and in the pipeline, and the leading companies have already built large-scale mass production lines of over 10GW, while other companies are also advancing rapidly. The construction of new scale production capacity is expected to accelerate as the technology continues to mature and the economics of the terminals are reflected.

JinkoSolar, one of the world's four largest module integrators, launched Tiger Neo, a module using N-type TOPCon cells, in November last year. The company has invested in TOPCon technology with relative certainty in recent years and has made rapid breakthroughs, breaking the world record for conversion efficiency several times. The efficiency of the mass production line also reached over 24.5%. In terms of large-scale capacity construction, JinkoSolar has 16GW of TOPCon capacity and is building and preparing for 19GW of new capacity, a big step ahead of the industry. The company has established a 900MW pilot line in 2019, and last year started the construction of two production bases in Haining Jianshan and Hefei, Anhui Province, with 8GW each in Phase I. Both projects were put into operation in Q1 and are now at full capacity, while the company started the 11GW Phase II project in Jianshan at the end of June and the Phase II cell project in Hefei is also under preparation. In terms of marketing, JinkoSolar TOPCon modules have won at least seven bids from central state-owned enterprises this year, making it a pioneer in the first year of N-type cells.

Trina Solar started the development of TOPCon cells as early as 2015, and released its module product i-TOPCon with this cell technology in 2019, followed by a pilot line scale of 500MW. The efficiency of the mass production line is also above 24.5%. In terms of large-scale production capacity, Trina launched its 8GW TOPCon project in Suqian in April this year and expects to put it into production within the year.

    In May, JA launched the DeepBlue 4.0 X module with a TOPCon cell called "Bycium+", which can reach a mass production efficiency of over 24.8%. In fact, by 2020, the company's TOPCon cell efficiency will be close to 24%. In terms of scale capacity, Ningjin's 1.3GW TOPCon cell capacity is expected to be put into operation in the near future, and the company is expected to have 6.5GW capacity by the end of the year. In addition, the company announced two new 10GW cell projects in Qujing and Yangzhou in May and June respectively.

Battery leader Tongwei also announced a new 32GW high-efficiency crystalline silicon battery project in early April, which will be built in two phases, with no clear technology yet.

In addition, Zhonglai is the leader in the module backsheet industry. In 2019, the company began to vigorously research and develop new cell and module business, and selected the TOPCon technology route, and achieved a mass production efficiency of 23.5% in the same year, and the current mass production conversion efficiency of TOPCon2.0 cells developed by itself can also reach 24.5%. The company has already shipped a total of 5GW of TOPCon modules. In terms of production capacity, the Company has completed about 7.6GW, including 3.6GW of production capacity at its Taizhou base, while 16GW of cell projects in Shanxi are under construction, with 4GW of the first phase of 8GW coming on stream at the end of June this year. (2) Together New Energy was established in 2018 and is a representative of a fast-growing emerging battery component company. The company has taken N-type technology as the core of its layout since its inception, and the experimental efficiency of TOPCon battery can reach 25.5% and the mass production efficiency is over 24.6%. The company has completed 1.2GW of TOPCon capacity in 2019 and will reach 6GW by the end of 2021 and 20/30GW by the end of 2022/23. Recently, the company won the tender for the project of Huaneng Group, a central enterprise, and has officially signed the contract, and launched three series of new high-efficiency N-type modules under the brand of "DAON" to the market.

From the perspective of economics and marketing, the manufacturing cost of TOPCon cells is still higher than that of PERC, mainly in terms of equipment cost and silver consumption of paste, but the difference is relatively small, and it is the most advanced among the major new cell technologies.

The high conversion efficiency of HJT cells is mainly related to their combination of two different materials and good surface passivation effects: 1HJT cells' high efficiency potential has attracted many institutions at home and abroad to make research breakthroughs, and from the results of laboratory research in recent years, the conversion efficiency of large-area cells has easily exceeded 25%, and the open-circuit voltage has generally approached or exceeded 750mV. Another advantage of HJT cells is their outstanding power generation gain, which is mainly reflected in: 1) the temperature coefficient is significantly lower than other major battery technologies, i.e., the power generation capacity is stronger at high temperature because of the higher open circuit voltage; 2) the outstanding power generation capacity of bifacial cells is mainly due to their natural symmetrical cell structure; 3) the strong response to low light is mainly due to their combination of the characteristics of thin film cells. It is a combination of the characteristics of thin film cells, amorphous silicon materials on the weak light absorption effect of strong manufacturing costs are still being addressed, equipment, silver consumption, silicon wafers and targets for the key breakthrough direction. From a comprehensive point of view, the industry-wide HJT capacity is expected to exceed 10GW, but the capacity of single companies is still not large, and the capacity under construction and planning has reached about 190GW, but the actual projects under construction and stable progress are relatively limited.

On the other hand, if innovations are made in the cell structure, focusing on the reduction of optical losses, even if the passivation technology related to PERC cells is used, it can still lead to a breakthrough in conversion efficiency, the most typical type of which is the back contact (BC) cell with all electrodes transferred to the backlight surface, which actually opens up possibilities for the next development of P-type cells. The core feature of IBC cell is that there is no metal grid line on the front surface, which can absorb sunlight without blocking the whole area, so that the frontal conversion efficiency can reach a high value, which is achieved by placing the emitter in the back area of the cell to form a spaced band. This is achieved by placing the emitters on the back side of the cell to form spaced bands, while the positive and negative fine grid electrodes are crossed on the back side. On the other hand, since the grid lines are on the back side, a larger width or density can be used to reduce the series resistance and further improve efficiency. Currently, commercially available IBC cells can already reach 25% efficiency. In addition, for cells with PN junctions on the backside, there is an important advantage in that the substrate wafer can be thinned more easily, which is related to the carrier collection rate, currently around 130 μm for IBC cells.

The unique structure of the BC cell makes it much more difficult and costly to produce. The key is to create spaced p- and n-doped regions on the back surface and to form metallized contacts and grids on them.

Back-contact cells, represented by IBCs, fit the differentiation characteristics of distributed PV. On the one hand, the strong single-sided power generation capacity and high cell packing density can generate more electricity with limited area and number of modules, on the other hand, the front side without grid lines is more in line with the aesthetic characteristics and can be better integrated into the architectural design. The distributed market is booming and the space is vast, which provides good conditions for the promotion of back-contact cells. In recent years, the global distributed PV market has been developing relatively rapidly. According to IEA data, the annual installed capacity of rooftop PV has increased from less than 35% in 2018 to nearly 45% in 2021, meaning that distributed PV has reached about half of the overall market. In the domestic sector, distributed PV growth is also strong, last year in the overall installed capacity for the first time in history exceeded the centralized, and has continued since this year, the first half of the year is more than 60%, which is mainly due to the lower cost of distributed systems, in the current silicon supply shortage resulting in high prices, the module price acceptance is relatively high, but in the long term distributed has become a major market alongside the centralized In the long run, however, distributed has become a major market alongside centralized. As for domestic enterprises conducting independent research: 1) Trina Solar, which jointly developed IBC cells with overseas academic institutions in 2011 and set a world record with a conversion efficiency of 24.4% in 2014, the large-area N-type IBC cells developed independently in 2018 became the first domestic battery with an efficiency of over 25% certified by a third party authority. In February this year, it announced that the mass production efficiency of IBC cells exceeded 24.1%. 3) Aixu, which launched its newly developed ABC cells at SNEC in June last year, adopts the back contact structure without grid lines on the front side, and the mass production efficiency can reach 25.5%. (4) JA Tech also exhibited IBC cells at SNEC 2019, and Hailun PV has also made a mark in IBC cells in the early days.

It is worth mentioning that Longi Green Energy, the leading integrated module manufacturer, has repeatedly stated this year that it will launch new products for the distributed application market, which, combined with previous analysis, are likely to be back contact cells similar to IBCs. It is expected that with the continuous research and development of domestic and foreign enterprises, especially the leading companies, the back contact battery is expected to move further into a broader mass market. If combined with the tunneling/polycrystalline passivation layer in the TOPCon cell, it can become a TBC cell (or POLO-IBC). The laboratory conversion efficiency of both types of cells has exceeded 26%, with Kaneka Japan developing a large-area HBC cell with an efficiency of 26.63% in 2017, which is the highest level of efficiency currently developed for crystalline silicon solar cells.

From the perspective of industrialization, although the superposition of multiple technologies brings about an increase in conversion efficiency, the cost will also increase significantly, such as the need to use equipment from multiple technologies at the same time, and the process will become more cumbersome and complicated, and the problem will be more prominent when the production cost of IBC and HJT is already much higher than that of mainstream PERC cells. Therefore, it is expected that HBC and TBC cells will reach mass production only when each independent technology route is already economical and ready for industrialization.

Finally, in the longer term, the superposition of multiple technologies may be the fundamental way for PV cells to move towards higher conversion efficiency levels, and an important direction that has attracted much attention is the combination of crystalline silicon cell technology and chalcogenide cell technology, both of which can form upper and lower two-layer or even multi-layer stacked cells that can make greater use of the solar spectrum to achieve a conversion efficiency of over 29%. The efficiency bottleneck of mainstream PERC cells has become more and more obvious, and the new generation of mass production technology represented by TOPCon and BC has shown good momentum during the year, which is expected to bring another leap in conversion efficiency, and the industrialization is expected to be accelerated under the continuous enhancement of economy. The smooth upgrade of cell technology is expected to accelerate the replacement of traditional energy by PV and further open up the growth space of the industry as a whole.