Solar cells are entering the age of 24%+ mass production efficiency. TOPCon and HJT are considered to be the most promising next-generation cell technologies. 2021 is a critical period for the competition between TOPCon and HJT. The process route that takes the lead in obtaining obvious advantages in mass production efficiency, cost and market share will dominate the future technological development direction.
From the point of process technology, the metal electrode of traditional PERC cell is still in direct contact with the silicon substrate, the contact interface between metal and semiconductor will produce energy band bending due to the mismatch of work function, and generate a large number of minority carrier recombination centers, which will affect the efficiency of solar cells. The TOPCon cell technology uses a thin film to isolate the metal from the silicon substrate to reduce minority carrier recombination. A layer of ultra-thin silicon oxide is prepared on the back of the cell, and then a thin layer of doped silicon is deposited. The two layers form a passivation contact structure. The ultra-thin oxide layer can make many electrons tunnel into the polysilicon layer while blocking the recombination of minority carriers and holes, and then the electrons are transported laterally in the polysilicon layer and collected by the metal, which greatly reduces the metal contact recombination current as well as improves the open circuit voltage and short circuit current of the cell. Thereby improving the cell conversion efficiency.
The front silver paste of TOPCon is quite different from the existing front silver paste of P-type cell. The fine grid of the TOPCon front silver paste uses silver aluminum paste. Although the production process of the TOPCon front silver paste is similar to that of the P-type cell, the formula is quite different. Thus, the relevant paste companies need to increase investment in research and development.
Judging from the current mass production of TOPCon, the average mass production efficiency is mainly around 24%, and the highest efficiency reaches 24.5%-25%, with the potential for large-scale industrialization to reach 25%. Due to the simplification of the process, the improvement of equipment maturity and the decline of equipment prices, the competitiveness of TOPCon in 2022 will become more and more obvious, which is also the premise of its large-scale industrialization.
In 2022, TOPCon mass production will begin to accelerate, and PV cell manufacturers will begin to deploy large-scale TOPCon mass production lines. According to public information statistics, at present, mainstream cell manufacturers including LONGi, Tongwei, Trina, and Jolywood, etc. have planned to invest 86.5GW in TOPCon capacity in 2021. In addition, TOPCon technology can be compatible with PERC production lines to the greatest extent, and the production difficulty is much lower than other N-type technical routes. Among the PERC production lines exceeding 200GW in the industry, at least half of the production capacity can be upgraded to TOPCon. ASIACHEM predicts that China TOPCon cell production capacity is expected to reach 40GW in 2022.
PV cell silver paste is divided into high temperature silver paste and low temperature silver paste. P-type cells and TOPCon cells use high temperature silver paste, and HJT cells use low temperature silver paste. Silver paste accounts for a relatively high proportion of the cost of cells. At present, the consumption of front silver is mainly reduced by the multi-busbar technology and the reduction of the grid lines width. According to CPIA, in 2021, the consumption of P-type cells front silver is about 71.7mg/pce, and the consumption of back silver is about 24.7mg/pce; the average consumption of the silver (aluminum) paste (95% silver) used on the front side of TOPCon cells is about 75.1mg/pce, the back silver consumption of leading enterprises is about 70mg/pce; the double-sided low temperature silver paste consumption of HJT cells is about 190mg/pce.
The expansion of TOPCon continues to advance, and the process of low consumption of silver paste and localization is accelerated. For TOPCon cells, the cost of silver paste accounts for more than 40% of the non-silicon cost, which is still significantly higher than that of PERC cells. The cost reduction of silver paste has become an important part of the development of TOPCon mass production. On the one hand, the consumption of silver paste is reduced through thinning + multi-busbar, and leading enterprises already have ultra-fine grid + SMBB technology. On the other hand, the localization of silver paste has continued to reduce costs, which will be accelerated with the TOPCon cell production capacity increasing. ASIACHEM predicts that the output of TOPCon cells in 2022 will increase significantly compared with 2021, and the total market size of TOPCon silver paste will reach 563 tons.
In terms of market competition, TOPCon has good development prospects, attracting many companies to deploy. The cell efficiency and cost reduction have always been the concern topics. On March 22nd 2022, the 8th Solar Cell Paste and Metallization Forum hosted by ASIACHEM will be held in Changzhou, Jiangsu, China. The meeting will discuss TOPCon cells to further improve efficiency and reduce costs.
