Each solar cell structure has its own efficiency limit that can be reached, so the iteration of photovoltaic technology is a historical necessity, just as we have experienced PERC cells have replaced aluminum back field (BSF) cells. The mass production efficiency of p-type PERC (Passivated Emitter and Rear Cell, passivated emitter and back cell) is getting closer and closer to its theoretical limit, although some major manufacturers claim that the mass production efficiency of PERC can reach 24% by the end of this year. But this is still too slow for the photovoltaic industry, which urgently needs to minimize the cost of electricity. This brings unprecedented development opportunities to n-type TOPCon. According to industry experts, n-type TOPCon Technology will usher in a bright moment in 2022.

TOPCon process is mature

According to CPIA data from China Photovoltaic Industry Association, the investment in the PERC production line in 2021 is about 194 million/GW, and the TOPCon production line is 220 million/GW, which are very close. Newly launched PERC production lines generally reserve TOPCon upgrade space. According to industry insiders, the equipment cost of upgrading the TOPCon process route per GWPERC is around 50-60 million.

From the perspective of battery preparation, the main equipment added/replaced by TOPCon compared with PERC is B diffusion, tunnel oxide layer and poly Si deposition equipment, and the rest of the links are basically compatible with the PERC production line. Photovoltaic equipment experts introduced that the old PERC capacity reconstruction and expansion of TOPCon can use tubular LPCVD + phosphorus expansion; or PECVD in-situ doping technology route. In the past two years, large-scale PERC production lines have been newly built, and TOPCon space is generally reserved, and the PECVD/PVD in-situ doping technology route can be used.

According to a new energy introduction, the difficulty of the current TOPCon cell process lies in thinning the thickness of the polysilicon layer and increasing the doping concentration to improve the passivation effect and increase the long-wavelength spectral response. At the same time, enlarging the process window and ensuring the stability of the mass production process while ensuring efficiency is the biggest challenge in current mass production. A new energy continues to optimize the LPCVD equipment and process to ensure the reliability and stability of the products. Through process optimization and control, controlling the uniformity of the ultra-thin oxide layer and polysilicon layer, optimizing the boron diffusion conditions, and controlling the oxygen content of the silicon wafer, the yield rate of a new energy n-type cell can reach a level similar to that of PERC.