Guided by the strategy of parity on-grid in 2020, the dark tide of iteration of photovoltaic power generation technology is endless.

 

Before 2015, silicon-based solar cells were dominated by BSF (aluminum back-field) batteries. After 2015, P-PERC (passivated emitter and backside technology) batteries began to increase. Currently, PERC batteries have become the mainstream battery in the market. After the conversion efficiency improved, it began to slow down gradually.

 

So, who is the next generation of solar cells? Heterojunction cells based on N-type silicon wafers have attracted particular attention in the past two years, and capital is being densely distributed.

 

Heterojunction with Intrinsic Thin Film (HIT for short, others also referred to as HJT or HDT or SHJ), the full name is crystalline silicon heterojunction solar cell. This technology deposits an amorphous silicon thin film on crystalline silicon. It combines the advantages of crystalline silicon cells and thin film batteries, with high potential for improving photoelectric conversion efficiency, greater cost reduction space, higher double-sided rate, and can effectively reduce Features such as heat loss, lower photoinduced attenuation, and simple preparation process are one of the hot spots for next-generation solar cell investment.

 

Since last year, a number of listed companies have stated in the announcement that they are paying attention to or have deployed the HIT field, including Tongwei, Aikang Technology, GCL Integration, Xinte Energy, Jinko Energy, Shanmei International, Oriental Risheng And many other energy companies.

 

HIT has become a new outlet in the solar cell industry. Will solar cells switch from P-type PERC cells to N-type HIT cells? When will this turn be achieved? What challenges does HIT mass production face?

 

Why did HIT become a vent?

 

According to the substrate material, solar cells can be divided into organic solar cells and inorganic solar cells.

 

Among them, inorganic solar cells can be divided into crystalline silicon solar cells and thin film solar cells, and crystalline silicon solar cells can be divided into single crystal silicon solar cells and polycrystalline silicon solar cells. At present, crystalline silicon solar cells, especially monocrystalline silicon solar cells, have become the mainstream of the market due to their high efficiency, strong reliability, and large potential for cost reduction.

 

According to the doping type of the base silicon wafer, single crystal silicon solar cells can be subdivided into P-type cells and N-type cells. In P-type batteries, PERC technology has gradually become mainstream, and SE (selective emitter) technology has been superimposed to gradually improve battery efficiency. However, P-type batteries have their limits in conversion efficiency, and N-type batteries will become the direction of high conversion efficiency in the future, mainly including PERT (emission junction passivation and back-field full diffusion), TOPCon (tunneling oxidation passivation contact), IBC (full Back electrode contact), HIT (heterojunction) four technology paths.

 

Among these four technology paths, PERT can achieve mass production, the technical difficulty is not large, and the equipment investment is small, but there is no cost-effective advantage compared with the double-sided P-PERC, which has proven to be an uneconomical technical route; the back of TOPCon is closed. Poor, mass production is very difficult. Currently companies with layouts include LG, REC, Zhonglai, etc .; IBC has the highest efficiency, which can reach 23.5% to 24.5%, but the technology is extremely difficult, the equipment investment is high, and the cost is high. Achieving mass production, the current layout of companies include LG, Zhonglai, Sunpower, etc .; HIT efficiency can reach 23% to 24%, fewer processes, mass production can be achieved, currently there are Panasonic, Tongwei, Jinneng, Zhongzhi, Jun The layout of companies such as Shi and the realization of mass production have become the future development direction of high-efficiency batteries, but the biggest obstacle currently is that the equipment investment is more expensive.

 

Compared with traditional solar cells, HIT adopts the structure of single crystal silicon substrate and amorphous silicon thin film heterojunction, and has the advantages of single crystal silicon and amorphous silicon cells, including high efficiency improvement potential, lower It has six advantages, such as large cost space, higher double-sided rate, can effectively reduce heat loss, lower light-induced attenuation, and simple preparation process. Among them, the first two advantages are particularly worthy of attention. In terms of efficiency improvement, the N-type silicon wafer used by HIT has a higher minority lifetime, and the symmetrical structure of amorphous silicon passivation can also obtain a lower surface recombination rate, so the open circuit voltage of silicon heterojunction solar cells is much higher than The efficiency potential of traditional monocrystalline silicon solar cells is 1.5% to 2% higher than the current PERC cells using P-type silicon wafers.

 

The current P-type single crystal PERC battery's conversion record is 23.95% created by JinkoSolar, while the HIT conversion record is 26.63% created by Japan's Kaneka Corporation. If HIT is superimposed with other technology routes, there will be more room for improvement in battery efficiency.

 

In terms of cost reduction, HIT combines the advantages of low-temperature manufacturing of thin-film solar cells, avoiding the traditional high-temperature process, which not only greatly saves fuel energy, but also the low-temperature processing environment is conducive to achieving HIT thinning, reducing the use of silicon, and reducing silicon. Raw material costs. The HIT process is relatively simplified, and the entire production process can be completed in only four steps. In order to achieve a conversion efficiency of 23.9%, P-PERC needs to stack multiple technologies. The process steps are up to 8 steps, which results in higher costs. .

 

Of course, the shortcomings of HIT are also obvious, mainly due to strict process requirements, low-temperature component packaging processes, high equipment investment, high cost of transparent conductive films, and ultimately higher overall battery costs.

 

According to PVInfoLink research data, in November 2019, the production cost of HIT cells was 1.65 yuan / watt, which is much higher than the 0.93 yuan / watt of single crystal PERC.

 

Planned production capacity has exceeded 35 GW

 

From the perspective of industry, it has been nearly 20 years of industrialization in the world to enter HIT, and the layout of domestic enterprises has basically been in the past five years.

 

HIT was first developed by Japan's Sanyo Corporation. In 1991, Sanyo first applied intrinsic amorphous silicon films to silicon heterojunction solar cells, reducing the density of interface defect states, reducing carrier recombination, and achieving heterojunction interfaces. The passivation effect results in an intrinsic thin film heterojunction battery with a conversion efficiency of 18.1%.

 

Since then, the conversion efficiency of HIT has been continuously improved. In 2003, Sanyo optimized the heterojunction, reduced optical loss, and increased the effective battery area to make the HIT laboratory efficiency reach 21.3%. In 2010, Sanyo announced the expansion of HIT module production scale and was acquired by Panasonic in 2012. In 2013, Panasonic developed a HIT battery with a thickness of only 98 μm, with an efficiency of 24.7%. In 2014, Panasonic adopted IBC technology to improve the conversion efficiency of HIT batteries to 25.6%.

 

From a global perspective, Japan's Sanyo, which has an existing capacity of 1 GW and a mass production efficiency of 23%, is the leader in this segment.The leading companies in HIT technology include the American photovoltaic company REC Solar, the Japanese photovoltaic company Kaneka, and the US Solarcity Big business.

 

Due to the high technical threshold of HIT and its long-term control in the hands of Japanese companies represented by Panasonic and Kaneka, the research on HIT technology in China lags significantly behind Japan. After 2015, Panasonic's HIT patents have expired, and technical barriers have been eliminated, which provides a historic opportunity for China to vigorously develop HIT technology.

 

According to relevant statistics, more than 10 enterprises in China have deployed HIT, and the total production capacity has been planned to exceed 35 GW.

 

Among them, in 2016, Junshi Energy completed the first domestic 100MW high-efficiency heterojunction battery production line with independent intellectual property rights, with a conversion efficiency exceeding 23%. In May 2019, Jun Shi Energy acquired Panasonic's Malaysia HIT plant, with a controlling stake of 90%. In 2019, Junshi Energy's production capacity exceeds 600 MW, the average efficiency of the production line is 23%, and the efficiency of the new production line under construction will exceed 25%.

 

In 2016, Jinneng Technology initially planned a 2 GW production capacity. In 2017, the HIT pilot line was put into operation. The existing capacity is 100 MW. The highest efficiency of HIT mass production is 23.85%, and the average yield of mass production is 98.29%. The planned capacity is 1 GW, and equipment is being purchased.

 

In May 2018, Tongwei Co., Ltd. announced that it will jointly build and plan a 2 GW HIT capacity project with Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, and Three Gorges Capital. The first ultra-efficient HIT was successfully rolled out in June 2019, and the cell conversion efficiency reached 23%. The entry of Three Gorges Capital as a shareholder means that state-owned assets are optimistic about HIT technology.

 

In May 2018, Rainbow New Energy Co., Ltd., a subsidiary of China Electronics Group, announced that it plans to build a 2 GW HIT project in Jiaxing, Zhejiang.

 

In July 2018, Aikang Technology's HIT project in Changxing County, Zhejiang has a planned production capacity of 5 GW, which is implemented in phases. The first phase of the first plant has completed the main construction and was originally planned to be put into production by the end of 2019.

 

In July 2019, Shanmei International Energy Group signed a cooperation agreement with Junshi Energy, and the two parties will jointly build a HIT production base of up to 10 GW. This is the largest HIT production plan in mainland China.

 

On August 19, 2019, Dongfang Risheng's HIT battery and module production project with an annual output of 2.5 GW was officially started. The project is planned to form an annual production capacity of 2.5 GW battery cells and 2.5 GW modules, and is expected to be completed in 2021.

 

As a result, the domestic photovoltaic industry can be described as a scramble for HIT layout, and is booming.

 

Major challenges in mass production

 

Although the domestic planned HIT has exceeded 35 GW, according to statistics from the photovoltaic industry media PV, the actual production capacity is only 1.3 GW. Why is HIT landing so slow?

 

According to the research of photovoltaics, in addition to Jinneng, Junshi, and CIIC, which entered the HIT field earlier, achieved mass production of 100 MW production lines, and Taiwan's joint renewable energy 50 MW, Jiaxing Shangpeng 40 MW small-scale mass production In addition, others are basically in the process of pilot production or capacity construction. The entire industry is still in the early demonstration stage and has not yet achieved mass production.

 

From the demand side, the reason for the above phenomenon is mainly due to the high cost of HIT, resulting in insufficient demand in domestic and foreign markets. In this regard, Lin Yanrong, chief analyst of PV InfoLink, introduced that after the "531" policy in 2018, the price of P-type products fell faster, opening a larger price gap with N-type products, and the sales of N-type products were more difficult. Therefore, most of the HIT plans are delayed or postponed, and basically only Jun Shi continues to stabilize and mass-produce.

 

From the supply side, it is mainly due to the high cost of HIT production equipment, which has not achieved large-scale mass production, and the cost performance advantage is not obvious. At present, HIT needs to build a new production line, and cannot use the original production line. The initial investment is very high. The imported production equipment is about 800 million to 1 billion yuan / GW, and the domestic equipment is about 500 million to 800 million yuan / GW. It is PERC. 2 to 3 times the production line.

 

Yang Liyou, general manager of Jinneng Technology, publicly stated that HIT needs to meet three requirements at the same time to enter large-scale mass production: conversion efficiency must reach 24.5%, cost cannot be higher than 15% of single crystal PERC, and initial investment of equipment cannot exceed 1.25 times of single crystal PERC .

 

According to this standard, HIT is still in a small-scale demonstration stage, and there is still a long way to go before mass production. In response, the third-party agency International "PV Technology Circuit Line" (TRPV) predicts that the HIT market share will increase from 3% in 2018 to 10% in 2025.

 

The world's leading Swiss solar equipment company Meyerberg predicts that HIT's market share will reach 8% in 2020 and 10% in 2023.

 

Jun Shi Energy, the earliest HIT in China, predicts that the installed capacity of HIT will increase by 10 GW from 2021 to 2023, and the market share of HIT is expected to reach 20% by 2025.