The P to N node has arrived, and the curtain of the photovoltaic revolution has begun (Part 2) Nov 26, 2021

The critical time for the P-type production line to switch to the N-type solar panel cell has arrived. N-type solar module cells have the advantage of increasing efficiency and reducing costs. The recent soaring raw materials will accelerate the transition to N-type solar module cells. Among them, TOPCon is the most cost-effective route. The solar panel cell conversion efficiency limit is higher, the equipment cost is low, and there is more room for mass production to increase speed.

For emerging capital and new entrants, they are more inclined to invest in HJT. Experts believe that this is a pseudo-propositional theory. Is photovoltaic so without manufacturing experience and process threshold? Can new equipment be closer to the workshop to produce good products? New capital and new players without accumulated experience will need longer time and a more tortuous learning curve to achieve theoretical advantages, and at that time, how did TOPCon's advantages reach the level it has reached today.

TOPCon solar panel cell technology, namely tunneling oxide layer passivation contact technology. Since the metal electrode of the PERC solar panel cell is still in direct contact with the silicon substrate, the contact interface between the metal and the semiconductor will bend the energy band due to the work function mismatch, and generate a large number of minority carrier recombination centers, which will have a negative impact on the efficiency of the solar cell. Therefore, some scholars have proposed that a thin film is used to isolate the metal from the silicon substrate in the solar panel cell design to reduce minority carrier recombination. A layer of ultra-thin silicon oxide is prepared on the back of the solar panel cell, and then a thin layer of doped silicon is deposited. A passivated contact structure. The ultra-thin oxide layer allows multi-carrier electrons to tunnel into the polysilicon layer while blocking the recombination of minority carrier holes. Then the electrons are transported laterally in the polysilicon layer and collected by the metal, which greatly reduces the metal contact recombination current and increases the open circuit voltage and short-circuit current of the solar panel cell. Thereby improving the conversion efficiency of the solar panel cell.

The development history of TOPCon is actually not long. Dr. Frank Feldmann of the Fraunhofer Institute in Germany first proposed the solar panel cell concept of TOPCon on the 28th EU-PVSEC in 2013. Since then, after a series of research institutes actively promoted the gradual maturity of the technology and the improvement of the theoretical conversion efficiency, the ultimate theoretical efficiency of the TOPCon solar panel cell reached 28.7%, which was higher than the 27.5% of HJT and 24.5% of PERC. At present, the average efficiency of crystalline silicon cell industrialization is about 2% lower than the laboratory efficiency, and there is a higher room for improvement in the efficiency of TOPCon cell industrialization. The conversion efficiency of N-type TOPCon solar panel cell has an advantage of 0.5% or more compared with the industry.

The efficiency of mass production has improved significantly, and the industrialization development will accelerate in 2021. According to the current situation of TOPCon mass production, the average mass production efficiency is mainly 24.5%, and the highest efficiency reaches 25%. The planned production capacity of mainstream solar panel cell manufacturers including Jinko has reached 15GW in 2021. At present, the efficiency of commercial TOPCon cells with monocrystalline silicon wafers has exceeded 25.4% for the first time, setting the latest world record.

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