In recent years, photovoltaic power generation technology is in rapid development, of which the most basic photovoltaic cell technology is a hundred flowers.
From simple polycrystalline and monocrystalline cells, to black silicon cells, high-efficiency monocrystalline cells, to PERC cells, HJT cells, N-type cells, different types of high-efficiency cells are emerging. The continuous improvement in efficiency has shown the vitality of PV power generation and the huge potential of PV power generation in the future.
In addition, PERC cells can also be stacked with half-sheet, double-glass and other process technologies, and the future development prospects are broad. Some expert analysis suggests that high-efficiency PERC cells will remain mainstream in the next two to three years.
PERC cells are developing at a feverish pace, while n-PERT cells, which were originally thought to have the potential to compete with PERC, are gradually being forgotten. Due to the difference in doping processes, PV cells are divided into P-type cells and N-type cells. P-type silicon wafers are simple to make and less expensive, while N-type silicon wafers usually have a larger lifespan of fewer subs and can be made more efficient, but the process is more complex. N-type cells, represented by n-PERT cells and HIT cells, have long been taken as the necessary path for the future development of crystalline silicon cells. But the emergence of P-type PERC cells has put N-type cells in an awkward position.
The efficiency advantage of n-PERT cells has been lost due to the increase in efficiency of PERC cells. PERC, the representative of P-type cells, is in full swing, while the N-type cell family, which has always been known as “high efficiency”, is in a quandary. A new type of battery has emerged that seems to give hope to N-type batteries again.
TOPCon battery comes out of nowhere
During SNEC 2019, the TOPCon cell was introduced across the board and received the spotlight of the industry.TOPCon technology involves preparing an ultra-thin tunneling oxide layer and a thin layer of highly doped polycrystalline silicon on the back of the cell, which together form a passivated contact structure. The structure can block the oligon hole compound and enhance the open circuit voltage and short circuit current of the cell.
In terms of process, TOPCon technology requires only additional thin film deposition equipment and is well compatible with current mass production processes. At the same time, TOPCon cells also have the scope to further improve conversion efficiency and are expected to be the entry point for the next generation of industrialised N-type high-efficiency cells. According to theoretical calculations, the potential efficiency of passivated contact solar cells (28.7%) is closest to the theoretical limit efficiency of crystalline silicon solar cells (29.43%).
It can be seen that, similarly to PERC cells, TOPCon cells also use a passivated contact structure on the back side to enhance cell performance. And in terms of process, the TOPCon cell achieves a larger efficiency increase at a smaller cost. In addition, the TOPCon cell has huge scope for future efficiency increases and is one of the cells closest to the theoretical efficiency values of crystalline silicon cells.
With the above advantages, the TOPCon battery undoubtedly has a broad development prospect. In addition, TOPCon cells are expected to become the entry point for N-type cells, opening up a path for the development of N-type cells.
At present, the mass production efficiency of TOPCon cells is between 22.5~23%, and there is still a lot of room for upward movement. TOPCon cells have already caused the layout of many photovoltaic enterprises, and Zhonglai and Trina Solar have announced the mass production of TOPCon. Among them, the full-size N-type monocrystalline bifacial passivated contact cell efficiency of Zhonglai shares reached 23.3%; Trina Solar developed a passivated contact cell efficiency of 24.58%; JinkoSolar developed a large-area TOPCon cell conversion efficiency of 24.2%.
It is reported that Martin Green, the “father of solar energy”, has said that the laboratory efficiency of PERC series cell technology should be able to increase to more than 26%. The current record efficiency of monocrystalline PERC cells is already close to 24%, and there is still room to rise, but not much. The current laboratory and mass production efficiencies of TOPCon cells are comparable to those of monocrystalline PERC cells, but there is a wider scope for efficiency increases.
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