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| TOPCon technical route and cost advantage analysis |
| Release time:2023-02-15 09:12:19| Viewed： |
TOPcon has certain economic advantages and will continue to expand.
1. TOPcon battery principle and technical route
N-type TOPcon (Tunnel Oxide Passivated Contact) battery is basically based on the infrastructure of PERC battery. The main changes are as follows:
First, the substrate is changed from P-type to N-type. The N-type semiconductor has a long minority carrier life, basically no boron-oxygen recombination, and has a higher tolerance for metal pollution;
Second, in the back structure, a 1-2 nm tunneling oxide layer SiOx is added first, and then a layer of doped polysilicon n poly Si is deposited to form the back passive contact structure. The tunneling oxide layer provides good chemical passivation performance, greatly reduces the interface recombination, and allows most carriers to effectively tunnel through the doped polysilicon layer. The doped polysilicon layer forms an n+/n high and low field with the substrate, which prevents minority carriers from moving to the surface and forms a selective passivation contact.
The difference of TOPCon process routes is mainly reflected in the growth of polysilicon and the preparation of oxide layer. At present, the mainstream technical solutions include LPCVD, PECVD, PVD, etc. (usually referred to as the preparation of polysilicon layer).
LPCVD scheme, that is, thermal oxygen is adopted for tunneling oxide layer, and LPCVD scheme (intrinsic+ion implantation/phosphorus expansion) is adopted for polysilicon layer. The technical process is relatively mature, and the passivation effect is good, but the film forming speed is slow, and the problem of winding plating needs to be solved additionally;
PECVD scheme, that is, PEALD scheme is adopted for tunneling oxide layer. The oxide layer is uniform, and PECVD forms a polysilicon layer. The film forming speed is fast, but H cannot be released. There is a problem of high H content and explosive film;
In the PVD scheme, the oxide layer is formed by PECVD, and the polycrystalline silicon deposition is completed by PVD. The film forming speed is fast and there is basically no influence on the coating.
2. Achieve substantial improvement in battery efficiency and power generation
Advantage 1: TOPCon has higher power generation efficiency, clear efficiency improvement path and large space.
TOPcon battery is based on N-type substrate and has longer minority carrier life. The selective transmission ability of the tunneling oxide layer greatly reduces the loss caused by carrier recombination. At the same time, with SMBB and other processes to reduce the front grid barrier, TOPcon battery efficiency has more than 1 pct advantage over PERC.
At the same time, TOPCon battery is still in the early stage of industrialization, with faster efficiency and speed. According to the CPIA, the efficiency of TOPcon battery has increased by 2.5 percentage points since 2018, and the efficiency of PERC has increased by 1.3 percentage points in the same period. The PERC battery is close to the theoretical limit in the middle and later stages of the cycle, and the efficiency improvement process is significantly lower than that of TOPcon. However, there is still a lot of room for optimization between the mass production efficiency of TOPCon and the theoretical limit of more than 28%, and the efficiency improvement path is also more clear.
Advantage 2: high double-sided rate, low attenuation, etc. to improve the full-cycle power generation
According to the white paper of Jingke energy products, the double-sided rate of N-type TOPcon battery can reach 85%, which is significantly higher than that of PERC about 70%, and roughly forms an efficiency advantage of about 1 pct when converted to comprehensive efficiency.
3. Better compatibility with PERC production line and process
1) High compatibility with existing PERC production line
From the aspect of silicon material/silicon wafer, TOPcon uses N-type substrate, which requires higher purity of silicon material than P-type. At present, the new production line of silicon material enterprises basically meets the demand of N-type. The drawing process of N-type silicon wafer requires lower impurity content of auxiliary materials such as thermal field, and the slice thickness is generally consistent with that of PERC. On the whole, equipment replacement is not involved in the upstream silicon material and silicon wafer heavy asset links;
From the aspect of battery preparation, the main equipment added/replaced by TOPCON compared with PERC are B diffusion, tunneling oxide layer and poly Si deposition equipment, and the other links are basically compatible with PERC production line;
From the perspective of component preparation, TOPcon usually cooperates with SMBB to reduce the amount of silver paste. At this time, the string welder is required to make corresponding adjustment (if the number of main grid lines is not changed, there is no need to adjust). TOPcon of high-temperature process is also suitable for the PERC production line at the component end.
In general, most of TOPcon and PERC processes are relatively close. Not only is there room for transformation and upgrading, but more importantly, existing industrial workers and mature processes can be fully utilized.
2) The investment intensity is gradually close to PERC, and the main consideration for reconstruction is to reserve space
According to the CPIA statistics, the investment of PERC production line in 2021 is about 194 million/GW, and that of TOPCON production line is 220 million/GW. The investment intensity of new production line has been close to that of PERC. According to the survey, the current actual investment in PERC production line has decreased to below 150 million/GW, while the investment in TOPcon production line has also decreased to around 200 million/GW. The difference in depreciation years caused by overlapping the life cycle of the production line and the difference in production scheduling caused by supply and demand. The new TOPcon production line has been evenly amortized to the single W depreciation amount has been close to PERC.
From the perspective of reconstruction, the increased investment (including boron expansion, deposition equipment, etc.) of PERC production line is about 40-600 million/GW, and the investment is not high. The main factors restricting the reconstruction of PERC production line are the technical scheme and reserved space (boron expansion is slower than phosphorus expansion, and equipment investment is increased). Most of the PERC production lines expanded after 2020 have reserved space for TOPCon's transformation, but according to the current statistical planning, the new TOPCon capacity in 2022 is mainly new capacity.
4. Economy has begun to show
1) On the revenue side, TOPcon has formed a premium: under the same version, TOPcon components provide 5-6% power increment compared with PERC, and the first-year attenuation, temperature coefficient and weak light performance are better, and the power generation in the whole life cycle is increased by about 4-5% compared with PERC (the amount is affected by the scenario), which means that under the same LCOE benchmark, TOPcon components will enjoy a premium compared with PERC.
Statically, referring to the current mass production efficiency of TOPcon 24-24.5%, it is estimated that the initial investment premium of TOPcon for single-sided components is about 0.1 yuan/W, and that for double-sided components is close to 0.15 yuan/W.
In dynamic consideration, the efficiency difference between TOPcon and PERC will increase. When the efficiency difference is increased to 2 pcts, the premium of N-type TOPcon at the end of single/double sided components will further close to 0.15/0.2 yuan/W.
Since the beginning of the year, the State Power Investment Corporation and China Nuclear Huineng have started bidding for N-type projects, and the State Power Investment Corporation has given a premium of 0.14 yuan/W for N-type components.
2) There is still room for cost reduction: from the perspective of cost increment, it is estimated that the total cost increment of TOPcon non-silicon+silicon is about 0.06-0.1 yuan/W.
Non-silicon cost: Non-silicon mainly comes from silver paste and depreciation: 1) At present, the consumption of silver paste on the front and back of 182 PERC is 70-80mg (about 1/3 of the back silver). In the past three years, the consumption of silver paste on the front and back of TOPCON has been significantly reduced, but it is still about 50mg (120-130mg/piece) higher than that of PERC. According to the current silver paste quotation, the increase of single-W non-silicon is roughly about 3 points. In the future, the line width will decrease and the processing cost will decrease. The consumption of TOPCon silver paste will still have a large space to decrease. The cost of non-silicon silver paste will be close to the increase of stacking efficiency. 2) The depreciation increase caused by equipment investment is about 1 point per unit. Considering the differences in technology, yield and production conditions (mainly affecting the energy consumption price) between enterprises, the current cost increment of non-silicon in TOPcon battery link is about 4-8 points/W.
Silicon cost: N-type silicon wafer is still 6% - 10% higher than P-type silicon wafer at present. According to the quotation of 182 silicon wafers, the increase of silicon cost is about 2-3 cents/W (at present, N-type silicon wafers have not been supplied in large quantities, and there is floating space).
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