Why do N-type?

First of all, why do you want to do N-type? The trend of component evolution and development, in short, is nothing more than the climb of power, and the traceability is directly linked to the efficiency of the cell. At present, the 23.38% conversion efficiency of Jinko's monocrystalline PERC solar panels cells has gradually approached its own efficiency limit (24.5%). On this basis, a major breakthrough in power can only be started from the cell size and module version. This will undoubtedly bring huge pressure on operation and maintenance costs and the matching of bracket inverters. The efficiency limit of N-type TOPCon photovoltaic pv cells is much higher than that of PERC cells (28.2%~28.7%). In addition to high conversion efficiency, N-type pv panels cells also have the advantages of high bifacial ratio, low temperature coefficient, no light decay, good low-light effect, and longer carrier life. In the long run, it has an absolute cost-effectiveness advantage. It can be said that the rise of N-type technology is an inevitable trend in the future.

At present, N-type solar module cell technology mainly includes TOPCon, HJT and IBC. JinkoSolar Vice President Qian Jing attended the 2nd "Belt and Road" Energy Ministers' Meeting recently. In the topic of "How the Next Generation Leading Photovoltaic Technology Can Promote the Energy Transformation of the Belt and Road", he discussed the efficiency, cost and process from various perspectives. Compare these three processes:

1) From the perspective of efficiency, the ultimate theoretical efficiency of TOPCon solar cells reaches 28.7%, which is higher than 27.5% of HJT and 24.5% of PERC. Judging from the current mass production efficiency, Jinko's latest TOPCon world record efficiency reaches 25.4%, and the mass production line efficiency exceeds 24%. Even so, there is still a certain gap from the limit efficiency, and there is still a lot of room for efficiency improvement;

2) From a process point of view, both TOPCon and HJT achieve power enhancement through passivation, but the former is through the tunnel oxide layer, and the HJT is through the deposition of amorphous silicon films. TOPCon needs to increase diffusion, etching and deposition equipment transformation in the PERC production line, and the cost increase is small; while the HJT cell process is the simplest and has the fewest steps (4 to 7 steps in the core process), but basically all the PERC production lines are replaced.

3) From the perspective of cost, the direct result of different processes is an increase in equipment cost of 240-400 million yuan/GW. The difference in the consumption of silver paste, based on the current data, the consumption of silver paste of HJT solar module cell is about twice that of TOPCon, and this rate will not be flattened in the short term. The difference in process leads to the difference in the commercialization cost of the two (about 0.3 RMB/W). With the increase in the cost of silver paste, the difference may be more than 0.3 RMB/W.

The critical moment has come

Qian Jing believes that the critical time has come for the P-type production line to switch to the N-type solar module cell. The advantages of N-type solar modules cells with greater efficiency and cost reduction space are reflected, and the recent soaring of raw materials will accelerate the transformation to N-type solar modules cells. Among them, TOPCon is the most cost-effective route, with high solar module cell conversion efficiency limit, low equipment cost, and greater room for mass production speedup.

As for emerging capital and new entrants, they are more inclined to invest in HJT. Qian Jing believes that this is a theory of false propositions. Is photovoltaics so lacking in manufacturing experience and process thresholds? Is it possible to produce good products with new equipment closer to the workshop? ?New capital and new players without accumulated experience will take longer and more tortuous learning curve to achieve theoretical advantages, and at that time, how could the advantages of TOPCon reach the level it has reached today.

TOPCon cell technology, namely the tunnel oxide 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 produce energy band bending due to work function mismatch and generate a large number of minority carrier recombination centers, which negatively affects the efficiency of solar cells. Therefore, some scholars have proposed the use of thin films to isolate the metal from the silicon substrate in the solar module cell design scheme to reduce minority carrier recombination. A layer of ultra-thin silicon oxide is prepared on the back of the solar module cell, and then a thin layer of doped silicon is deposited. The two together form Passivated contact structure. The ultra-thin oxide layer can make many electrons tunnel into the polysilicon layer while blocking the recombination of minority holes 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 and improves the open circuit voltage and short circuit current of the solar module cell. Thereby improving the solar module cell conversion efficiency.

The development history of TOPCon is actually not long. Dr. Frank Feldmann of the Fraunhofer Institute in Germany first proposed the solar module cell concept of TOPCon at the 28th EU-PVSEC in 2013. Since then, through the active research and development of a series of scientific research institutes to promote the gradual maturity of technical processes and the improvement of theoretical conversion efficiency, the ultimate theoretical efficiency of TOPCon cells has reached 28.7%, which is higher than 27.5% of HJT and 24.5% of PERC. At present, the average industrialization efficiency of crystalline silicon cells is lower than the laboratory efficiency by about 2 percentage points, and the industrialization efficiency of TOPCon cells has more room for improvement. The conversion efficiency of N-type TOPCon cells has an advantage of nearly 0.5% compared with the industry.

The efficiency of mass production has improved significantly, and the development of industrialization will accelerate in 2021. At present, the mass production of TOPCon shows that the average mass production efficiency is mainly 24.5%, and the highest efficiency reaches 25%. The planned production capacity of mainstream solar module cell manufacturers including Jinko has reached 15GW in 2021. At present, the efficiency of the commercial-sized TOPCon cell of monocrystalline silicon wafer has exceeded 25.4% for the first time, setting a new world record.