Why has IBC battery technology not become the mainstream of the photovoltaic industry?

Recently, TCL Zhonghuan announced to subscribe for convertible bonds from MAXN, a shareholding company, for US$200 million to support the research and development of its Maxeon 7 series products based on IBC battery technology. On the first trading day after the announcement, the share price of TCL Central rose by the limit. And Aixu shares, which also uses IBC battery technology, with the ABC battery about to be mass-produced, the stock price has increased by more than 4 times since April 27.


As the photovoltaic industry gradually enters the N-type era, N-type battery technology represented by TOPCon, HJT, and IBC has become the focus of enterprises competing for layout. According to the data, TOPCon has an existing production capacity of 54GW, and an under-construction and planned production capacity of 146GW; HJT’s existing production capacity is 7GW, and its under-construction and planned production capacity is 180GW.


However, compared with TOPCon and HJT, there are not many IBC clusters. There are only a few companies in the area, such as TCL Central, Aixu, and LONGi Green Energy. The total scale of existing, under construction and planned production capacity does not exceed 30GW. You must know that IBC, which has a history of nearly 40 years, has already been commercialized, the production process has matured, and both efficiency and cost have certain advantages. So, what is the reason that IBC has not become the mainstream technology route of the industry?

Platform technology for higher conversion efficiency, attractive appearance and economy

According to the data, IBC is a photovoltaic cell structure with back junction and back contact. It was first proposed by SunPower and has a history of nearly 40 years. The front side adopts SiNx/SiOx double-layer anti-reflection passivation film without metal grid lines; and the emitter, back field and corresponding positive and negative metal electrodes are integrated on the back of the battery in an interdigitated shape. Since the front side is not blocked by grid lines, the incident light can be utilized to the maximum extent, the effective light-emitting area can be increased, the optical loss can be reduced, and the purpose of improving the photoelectric conversion efficiency can be achieved.


The data shows that the theoretical conversion efficiency limit of IBC is 29.1%, which is higher than 28.7% and 28.5% of TOPCon and HJT. At present, the average mass production conversion efficiency of MAXN’s latest IBC cell technology has reached over 25%, and the new product Maxeon 7 is expected to increase to over 26%; the average conversion efficiency of Aixu’s ABC cell is expected to reach 25.5%, the highest conversion efficiency in the laboratory The efficiency is as high as 26.1%. In contrast, the average mass production conversion efficiency of TOPCon and HJT disclosed by companies is generally between 24% and 25%.

Benefiting from the single-sided structure, IBC can also be superimposed with TOPCon, HJT, perovskite and other battery technologies to form TBC, HBC and PSC IBC with higher conversion efficiency, so it is also known as a “platform technology”. At present, the highest laboratory conversion efficiencies of TBC and HBC have reached 26.1% and 26.7%. According to the simulation results of PSC IBC cell performance conducted by a foreign research team, the conversion efficiency of 3-T structure PSC IBC prepared on the IBC bottom cell with 25% photoelectric conversion efficiency front texturing is as high as 35.2%.

While the ultimate conversion efficiency is higher, IBC also has strong economics. According to the estimates of industry experts, the current cost per W of TOPCon and HJT is 0.04-0.05 yuan/W and 0.2 yuan/W higher than that of PERC, and companies that fully master the production process of IBC can achieve the same cost as PERC. Similar to HJT, IBC’s equipment investment is relatively high, reaching about 300 million yuan/GW. However, benefiting from the characteristics of low silver consumption, the cost per W of IBC is lower. It is worth mentioning that Aixu’s ABC has achieved silver-free technology.

In addition, the IBC has a beautiful appearance because it is not blocked by grid lines on the front, and is more suitable for household scenarios and distributed markets such as BIPV. Especially in the less price-sensitive consumer market, consumers are more than willing to pay a premium for an aesthetically pleasing appearance. For example, black modules, which are very popular in the household market in some European countries, have a higher premium level than conventional PERC modules because they are more beautiful to match with dark roofs. However, due to the problem of the preparation process, the conversion efficiency of black modules is lower than that of PERC modules, while the “naturally beautiful” IBC does not have such a problem. It has a beautiful appearance and higher conversion efficiency, so the application scenario Wider range and stronger product premium capability.

The production process is mature, but the technical difficulty is high

Since IBC has higher conversion efficiency and economic advantages, why are so few companies deploying IBC? As mentioned above, only companies that fully master the production process of IBC can have a cost that is basically the same as that of PERC. Therefore, the complex production process, especially the existence of many types of semiconductor processes, is the core reason for its less “clustering”.


In the traditional sense, IBC mainly has three process routes: one is the classic IBC process represented by SunPower, the other is the POLO-IBC process represented by ISFH (TBC is of the same origin as it is), and the third is represented by Kaneka HBC process. The ABC technology route of Aixu can be regarded as the fourth technological route.


From the perspective of the maturity of the production process, the classic IBC has already achieved mass production. Data shows that SunPower has shipped a total of 3.5 billion pieces; ABC will achieve a mass production scale of 6.5GW in the third quarter of this year. Components of the “Black Hole” series of the technology. Relatively speaking, the technology of TBC and HBC is not mature enough, and it will take time to realize commercialization.


Specific to the production process, the main change of IBC compared with PERC, TOPCon, and HJT lies in the configuration of the back electrode, that is, the formation of interdigitated p+ region and n+ region, which is also the key to affecting battery performance. In the production process of the classic IBC, the configuration of the back electrode mainly includes three methods: screen printing, laser etching, and ion implantation, resulting in three different sub-routes, and each sub-route corresponds to as many processes as 14 steps, 12 steps and 9 steps.


The data shows that although the screen printing with mature technology looks simple on the surface, it has significant cost advantages. However, because it is easy to cause defects on the surface of the battery, the doping effect is difficult to control, and multiple screen printing and precise alignment processes are required, thus increasing the process difficulty and production cost. Laser etching has the advantages of low compounding and controllable doping types, but the process is complex and difficult. Ion implantation has the characteristics of high control precision and good diffusion uniformity, but its equipment is expensive and it is easy to cause lattice damage.


Referring to the ABC production process of Aixu, it mainly adopts the method of laser etching, and the production process has as many as 14 steps. According to the data disclosed by the company at the performance exchange meeting, the mass production yield rate of ABC is only 95%, which is significantly lower than the 98% of PERC and HJT. You must know that Aixu is a professional cell manufacturer with profound technical accumulation, and its shipment volume ranks second in the world all year round. This also directly confirms that the difficulty of the IBC production process is high.


One of the next-generation technology routes of TOPCon and HJT

Although the production process of IBC is relatively difficult, its platform-type technical features superimpose a higher conversion efficiency limit, which can effectively extend the technology life cycle, while maintaining the market competitiveness of enterprises, it can also reduce the operation caused by technological iteration. risk. In particular, stacking with TOPCon, HJT, and perovskite to form a tandem battery with higher conversion efficiency is unanimously regarded by the industry as one of the mainstream technology routes in the future. Therefore, IBC is likely to become one of the next-generation technology routes of the current TOPCon and HJT camps. At present, a number of companies have disclosed that they are conducting relevant technical research.


Specifically, the TBC formed by the superposition of TOPCon and IBC uses POLO technology for the IBC with no shield on the front, which improves the passivation effect and open-circuit voltage without losing current, thereby improving the photoelectric conversion efficiency. TBC has the advantages of good stability, excellent selective passivation contact and high compatibility with IBC technology. The technical difficulties of its production process lie in the isolation of the back electrode, the uniformity of the passivation quality of polysilicon, and the integration with the IBC process route.


The HBC formed by the superposition of HJT and IBC has no electrode shielding on the front surface, and uses an anti-reflection layer instead of TCO, which has less optical loss and lower cost in the short wavelength range. Due to its better passivation effect and lower temperature coefficient, HBC has obvious advantages in conversion efficiency at the battery end, and at the same time, the power generation at the module end is also higher. However, the production process problems such as strict electrode isolation, complex process and narrow process window of IBC are still the difficulties that hinder its industrialization.


The PSC IBC formed by the superposition of perovskite and IBC can realize the complementary absorption spectrum, and then improve the photoelectric conversion efficiency by improving the utilization rate of the solar spectrum. Although the ultimate conversion efficiency of PSC IBC is theoretically higher, the impact on the stability of crystalline silicon cell products after stacking and the compatibility of the production process with the existing production line are one of the important factors restricting its development.


Leading the “Beauty Economy” of the Photovoltaic Industry

From the application level, with the outbreak of distributed markets around the world, IBC module products with higher conversion efficiency and higher appearance have broad development prospects. In particular, its high-value features can satisfy consumers’ pursuit of “beauty”, and it is expected to obtain a certain product premium. Referring to the home appliance industry, the “appearance economy” has become the core driving force for market growth before the epidemic, while those companies that only focus on product quality have been gradually abandoned by consumers. In addition, IBC is also very suitable for BIPV, which will be a potential growth point in the medium to long term.


As far as the market structure is concerned, currently there are only a few players in the IBC field, such as TCL Zhonghuan (MAXN), LONGi Green Energy and Aixu, while the distributed market share has accounted for more than half of the overall photovoltaic market. Especially with the full-scale outbreak of the European household optical storage market, which is less price-sensitive, high-efficiency and high-value IBC module products are likely to be popular among consumers.

Post time: Sep-02-2022