TOPCon industry status: good device compatibility is favored by existing players.
Battery structure: Good compatibility with PERC production line
TOPCon is simply the use of silicon oxide, doped polysilicon to achieve passivation contact, is a kind of ultra-thin oxide layer as a passivation layer structure of high-efficiency solar crystalline silicon battery. In 1983, the "father of solar energy", Australian solar scientist Martin Green developed a cell structure that uses tunneling oxide layers and polycrystalline silicon layers. In 2014, the Fraunhofer ISE Institute in Germany announced the realization of a small-area battery based on tunneling passivation technology with an efficiency of 23%, and named the battery structure TOPCon.
Compared with PERC, TOPCon requires an additional 3 to 4 steps in the process, including the preparation of boron emitters, the growth tunneling of the oxide layer, the deposition of polysilicon and its doping, and cleaning after diffusion. Among them, the growth of tunneling through the oxide layer, the deposition of the intrinsic polycrystalline silicon layer, and the doped polycrystalline silicon are the three processes at the core. An ultra-thin tunneling oxide layer (1.5 nm) and a layer of highly doped polysilicon film are prepared on the frontal back of the cell, and the two together form a passivation contact structure and achieve surface passivation on the back side. The ultra-thin tunneling oxide layer allows polysonal electrons to tunnel into the polycrystalline silicon layer while blocking the oligosonous cavity recombination, which is conducive to increasing the open circuit voltage.
Core equipment: the core link is polysilicon deposition, and there are more process routes to choose
The TOPCon production line has good equipment compatibility with the existing mainstream battery technology PERC, and the increased equipment mainly revolves around the TOPCon core process. At present, the equipment investment of PERC is about 150 million yuan / GW, and for the upgrading of the production line, the increase in equipment investment is 50 million yuan to 70 million yuan.
In the preparation of the TOPCon process, the most important link is the deposition of polysilicon. The choice of different solutions involves different core equipment including LPCVD, PECVD, PVD, ALD, etc.
At present, the most mature scheme is the LPCVD route, which is grown by thermo-oxygen method to tunnel through the oxide layer, deposit the polycrystalline silicon layer through LPCVD, and then diffuse phosphorus. LPCVD coating uniformity is good, high density, but there is no advantage in efficiency, and the problem of sparing is also one of its main constraints.
The application of PECVD in TOPCon was first proposed by Meyer Burger, compared to LPCVD, in principle, it can be achieved without wrapping deposition, and slight wound plating is also easier to clean. PECVD deposition rate is fast and can be doped in situ. On the other hand, the uniformity of PECVD coating is not as good as that of LPCVD, and it is easy to burst the film.
The advantages of the PVD route are mainly reflected in the large production capacity and high degree of process integration; however, the amount of PVD silicon targets is large, and the replacement is relatively frequent, which increases the cost.
In addition to polysilicon deposition, in the preparation of THE TOPCon process, the tunneling oxide layer is also an incremental process step compared to PERC, and the main process methods include thermal oxidation method, PECVD, atomic layer deposition, wet chemical method, excimer source dry oxygen, etc., which correspond to the equipment thermal oxidation tube furnace, plate type PECVD/tubular PECVD, ALD, trough wet equipment, and trough wet equipment. The thickness of the tunneling oxide layer is one of the key characteristics, usually between 1.5 nm and 2 nm.
TOPCon equipment suppliers, according to the different technical routes of the deposition process, mainly include: LPCVD: Laplace, Pule New Energy, Jiejia Weichuang, SEMCO, Centrotherm, etc.; PECVD: Jinchen Shares, Jiejia Weichuang, Centrotherm, etc.; PVD: Jietai Optoelectronics, Pule New Energy, von Ardenne, etc.; PEALD: Jiangsu Microconductor, etc.; APCVD: Schmid, etc.
Laplace (Liancheng CNC Shareholding Company): Founded in May 2016, it launched the first LPCVD pilot product in 2017, and is committed to becoming a provider and leader of photovoltaic high-end equipment and solutions. At present, the company's core products are mainly thermal processes (diffusion, oxidation, annealing, etc.); coating (PECVD, LPCVD, ALD, etc.); and supporting automation equipment.
Jiangsu Micro-Guide: The photovoltaic division is mainly based on key vacuum coating and etching equipment, and the core technology is ALD, PEALD, PECVD, Diffusion/LP, RIE and other products. PEALD combines ALD with plasma-assisted deposition methods, and Jiangsu Microconductor was the first equipment supplier to introduce the technology, mainly used in TOPCon preparation.
Liancheng CNC: The products of the holding company Aihua (Wuxi) Semiconductor Technology Co., Ltd. are mainly used in the epitaxial growth of semiconductor thin films, and the core R&D team has been deeply engaged in the field of photovoltaic and semiconductor materials for many years. Participated in Shanghai Buchuan Intelligent Technology Co., Ltd., a supplier of photovoltaic and semiconductor wet process equipment.
Pule New Energy (Beijing Cree Holding Subsidiary): Pule New Energy was established in 2006, and its main business is currently the development and sales of LPCVD and other equipment based on TOPCon battery technology.
Jinchen Co., Ltd.: In 2019, it entered the development of TOPCon high-efficiency battery PECVD equipment, and the technical route is tubular PECVD. The company has carried out strategic cooperation with the Ningbo Institute of Materials of the Chinese Academy of Sciences in terms of TOPCon batteries, realized the preparation of TOPCon "ultra-thin silicon oxide" + "in situ doped amorphous silicon" with tubular PECVD, and entered the pilot efficiency improvement stage with JAO; the average efficiency of cooperation with Risen Energy exceeded 24%; and cooperated with Jinko to introduce the company's PECVD technology for the research and development of TOPCon cells.
Jiejia Weichuang: Jiejia Weichuang launched LPCVD and three-in-one tubular PECVD in the field of TOPCON, with the ability to supply the whole line equipment, and the company recently obtained the order for the whole line of Runyang 5GWTOPCon.
Otway: Plans to implement the layout of TOPCon battery equipment through fixed increases, mainly for the LPCVD route, but also including boron-doped equipment.
Conversion efficiency: the average efficiency of mass production of leading enterprises exceeded 24%
TOPCon mass production line conversion efficiency: In terms of mass production line efficiency, TOPCon is currently 0.5 to 0.8 pct higher than PERC+ on average. JinkoSolar Vice President Qian Jing said in an interview with reporters in October 2021 that Jinko introduced the mass production of TOPCon products in 2019, when the conversion efficiency was 23.5%, in 2020 it increased to 24.2%, and the average conversion efficiency of mass production in 2021 reached 24.5%. In response to investors' questions in 2021, Jolywood mentioned that the average conversion efficiency of the company's 166-size N-type TOPCon 1.0 battery mass production was 23.7%, and the efficiency of TOPCon 2.0 products based on POMPEID technology reached 24.2%.
TOPCon Laboratory Conversion Efficiency: The world record for TOPCon laboratory conversion efficiency is 26.0% (4cm in area) created by TOPCon inventor Fraunhofer in 2020. At present, the highest conversion efficiency of the domestic TOPCon laboratory is 25.53% (Voc=700.7 mV, Jsc=43.04 mA/cm2, FF=84.64%) released by the Ningbo Institute of Materials of the Chinese Academy of Sciences in November 2021, which was previously the domestic record of 25.4% released by JinkoSolar and Jolywood in October 2021. Ningbo Institute of Materials 25.53% Laboratory Conversion Efficiency TOPCon cells use PECVD (in collaboration with Jinchen) to prepare polysilicon layers.
3.2 Cost reduction and efficiency improvement: The cost of non-silicon is gradually approaching PERC, and silver consumption reduction and yield improvement are the key
Silicon wafers account for about 62% of the TOPCon battery cost component. The cost composition of TOPCon batteries mainly includes silicon wafers, slurries/wire meshes, equipment, etc. Assuming that the price of silicon wafers returns to a reasonable range, under normal circumstances, its proportion is 62%, 20%, 6%, and the cost of silicon wafers and slurry accounts for more than 80%.
The average non-silicon cost of PERC cells is about 0.18~0.22 yuan/W, and the non-silicon costs of TOPCon and PERC are gradually approaching. For TOPCon batteries, the cost of silicon is relatively limited, mainly due to the difficulty of thinning. For this reason, the cost reduction of TOPCon batteries mainly revolves around the cost of non-silicon, and the core lies in the reduction of silver paste consumption in the metallization link and the improvement of the yield rate of the production line.