PERC (Passivated Emitter and Rear Cell), the passivated emitter and back cell technology, was first proposed by Australian scientist Martin Green in 1983 and is now becoming a new generation of conventional technology for solar cells. PERC's efficiency record has been continuously updated in recent years and will become the most cost-effective technology in the next three years.
 
PERC technology increases conversion efficiency by adding a dielectric passivation layer on the back side of the cell. A better level of efficiency in standard cell structures is limited by the tendency of photogenerated electrons to recombine. The PERC solar cell maximizes the potential gradient across the P-N junction, which allows for more stable flow of electrons and reduces electronic recombination for higher efficiency levels.
 
The advantages of PERC technology are also reflected in the compatibility with other high-efficiency solar cell and component technologies, and the potential for continuous improvement in efficiency and power generation. Through the superposition of multiple main gates, selective emitters and TOPCon technology, PERC solar cell efficiency can be further improved; combined diamond wire cutting and black silicon technology can improve the cost performance of polycrystalline cells. The double-sided PERC solar cell realizes double-sided power generation with almost no increase in cost, and achieves 10%-25% power generation gain on the system side, which greatly enhances the competitiveness and future development potential of PERC technology.


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PERC solar cell efficiency record
1. Comparison of PERC solar cell technology and conventional solar cell efficiency
Photoelectric conversion efficiency is the most important parameter of crystalline silicon solar cells. In 2017, the conversion efficiency of conventional polycrystalline silicon cells produced by China's industrial production reached 18.8%, and the conversion efficiency of single crystal silicon cells reached 20.2%.
Compared with conventional solar cells, the advantages of PERC solar cells are mainly two aspects:
(1) The inner panel reflection is enhanced to reduce the optical loss of long waves;
(2) High-quality back passivation, which makes the open circuit voltage (Voc) and short-circuit current (Isc) of the PERC solar cell significantly higher than that of the conventional solar cell, so that the solar cell conversion efficiency is higher.
 
At present, PERC technology has become the main method for increasing the efficiency of P-type solar cells, but the performance of PERC technology on polycrystalline and monocrystalline cells is different. After the introduction of PERC technology, the single crystal cell production line can increase the absolute value of conversion efficiency by more than 1%, that is, the industrial efficiency of single crystal PERC can reach 21%, and some leading companies can increase the efficiency to 21.5%; The efficiency of the polycrystalline cell has an absolute value of 0.6% or more, and the industrial efficiency of the PERC polycrystalline solar cell can reach 19.5%. In addition, if the black silicon technology is superimposed on the polycrystalline PERC solar cell, the industrialization efficiency can reach more than 20%.
 
2, PERC solar cell technology efficiency development
PERC solar cells are the main technical contributors to the solar cell efficiency record that has been broken again and again. In the first half of 2018, the PERC solar cell efficiency was recorded at 23.95%, which was created by Jinko on May 9, 2018.
As a large number of PV companies enter PERC production and actively promote technological innovation, solar cell efficiency is rapidly increasing.
 
PERC solar cell capacity
1. Actual situation of global PERC capacity (2018)
Downstream of silicon wafers, industry leaders have launched high-efficiency cell/component expansion plans, and monocrystalline cells are expanded to monocrystalline PERC. At the end of 17th, the global single crystal PERC solar cell capacity exceeded 30GW. According to the current expansion plan, it is expected to reach 60GW by the end of 18th.
2. Percentage of PERC products in all application products
According to the report released by ITRPV-2018, the market share of PERC components in all applications will increase significantly.
3, 2018 ~ 2021 PERC solar cell capacity forecast
As the maturity of PERC technology continues to increase, the cost gap between conventional single crystal and single crystal PERC is gradually narrowing. It is expected that from 2018, PERC will gradually replace conventional single crystal and become the standard for single crystal production line. On the basis of polycrystalline, on the basis of the diamond-cut polysilicon wafer with black silicon technology to greatly reduce the cost and efficiency, superimposed PERC technology can achieve the effect of "1+1>2". It is expected that solar cell manufacturers will start from 2018. Do the upgrade of polycrystalline black silicon + PERC technology. According to PV infolink, the annual production capacity of PERC will gradually increase from 2018 to 2021, reaching 55GW, 77GW, 91W and 96GW, respectively, as shown in the following figure. Single crystal PERC will still occupy a major share of the PERC market.
 
PERC solar cell technology outlook
PERC solar cells also have a lot of room for efficiency improvement, and there is room for optimization of the emitter, back aluminum back field, main grid, and wafer quality. It is expected that in 2025, single crystal PERC cells can achieve conversion efficiency of up to 24%, and the market share will be further improved.
With the advancement of technology, the maturity of the double-sided PERC process not only broadens the application scenarios of the PERC solar cell, but also achieves higher power generation gain.
 
Various PERC technical routes
At present, the mass production efficiency of the leading single crystal PERC solar cell can reach 21.5%, and the mass production efficiency of polycrystalline PERC can reach 19.7%. As of now, the world's highest efficiency of single crystal PERC and polycrystalline PERC has reached 23.6% and 22.04%, respectively, created by Longji Leye and Jingke Energy. It can be seen that the PERC solar cell still has a lot of room for efficiency improvement.
The PERC solar cell efficiency is further improved in the following directions:
(1) fine grid metallization technology to reduce frontal occlusion, such as applying 5BB or MBB technology;
(2) Selective emitters on the front side to reduce surface recombination loss;
(3) Advanced trapping techniques, such as multi-layer anti-reflection technology;
(4) Reducing the recombination of the back metal contact areas, such as local B doping
(5) using high-quality silicon wafers, such as increasing the minority lifetime of silicon wafers; (6) double-sided PERC solar cells.
 
Author: Carrie Wong
From WSL Solar Co., Ltd.
 
WSL Solar has been a quality and professional manufacturer of custom solar panels (or custom PV modules) and solar solution provider in China since 2006. With our in-house R&D team and management team for over 10 years' experience in solar industry, we are able to design and develop a customized solar module in a variety of sizes, shapes and outputs to meet our client's specific requirement, and provide solution support start from initial product development stage. For more detail, please visit https://www.wsl-solar.com/