Brief description of PERC battery

At the beginning of May 2018, Tongwei Solar independently developed a super-420W high-efficiency shingle component. Its 72-piece module has a maximum power output of 421.9W, breaking the world record of PERC components, and obtaining quality supervision and inspection of Chengdu's national PV products. Central test verified that the component conversion efficiency could reach 20.7%, which fully meets and greatly exceeds the technical leader limit of "Technology Front Runner".

Tongwei Solar double-sided PERC shingle components can reach 460W. At the same time, the components passed all the stability and reliability tests of the new IEC61215 & IEC61730 standards, and obtained the new standard certification of tiling components IEC61215 & IEC61730 issued by T?VNORD.

Every time the technology research and development can bring people surprises, this news is more to see the brilliant future of the photovoltaic industry technology development. Technology is always the first productive force. The improvement of technology means higher product performance, and it represents the trend of the future technology field. We may wish to review the history of photovoltaic technology, the predecessor of photovoltaic PERC technology under the popular science...

What is PERC technology?

PERC technology: Passivation of the back surface with Al2O3 film can effectively reduce back surface recombination, increase open circuit voltage, increase back surface reflection, improve short circuit current, and improve battery efficiency.

A 1% efficiency improvement can achieved on P-type single crystal silicon, and a 0.6% efficiency improvement can achieved on polysilicon. Due to its relatively simple process and low cost increase, PERC batteries are capable of achieving 1% efficiency improvement on P-type single crystal silicon at present and in the future, and 0.6% efficiency improvement on polysilicon. PERC batteries are the current and future main flow production processes due to their relatively simple process and low cost increase.

Advantages of PERC batteries

1) High photoelectric conversion efficiency can reduce the BOS cost of the system.

2) Low attenuation can guarantee the project's power generation.

3) The mechanical properties are not bad, and the cracking will not increase significantly.

4) High power generation can increase the revenue of the project.

Currently several types of PERC technology single crystal P type and N type

The manufacturing process is different, they are different technical routes, P-type is a relatively mature process, and the advantage is that the price is lower, N-type is the latest technical route, and the advantage is higher efficiency and longer life.

At present, P-type crystalline silicon batteries occupy an absolute share of the crystalline silicon battery market. Compared with the conventional P-type single crystal silicon, the N-type single crystal silicon has the advantages of high minority lifetime, small photoinduced attenuation, and the like, and has a larger space for efficiency improvement.

PEC technology for P-type batteries

PERC technology represents a better premium advantage and development space in the field of single crystal cells. The PERC technology increases the conversion efficiency of single crystal cells by 1 percentage point, while the polycrystalline battery is only 0.5 percentage points. From a premium point of view, the benefits of PERC technology for single crystal cells are more pronounced, and the premium of polycrystalline batteries offset by the depreciation of new equipment.

PERT technology for N-type batteries

The PERT battery is an emitter junction passivated fullback field diffusion cell, which characterized by a full coverage of the back surface diffusion to reduce the back contact resistance and recombination rate of the battery. Different processes, mainly including tube diffusion, epitaxial growth method, ion implantation method and the like, can realize the backfield diffusion of the back surface.

Double-sided power generation technology for N-type batteries

Different from the conventional p-type battery, the n-type battery has a passivation film covering on both sides, and the metallization completed by screen-printing. Since the front and back grid lines are all conventional H-types, the battery can absorb light not only on the front side. Its back surface also absorbs incident light to generate additional power. Maximum power output performance increased by 10%-15%.

At present, Yingli Panda double-sided power generation components can output up to 330W.

From 2016 to 2017 alone, the efficiency gains of PERC components have far exceeded the industry's original expectations. Based on the above four main reasons, the PERC component has become the standard in the "Leader" project and the mainstream technology in the next few years, which will accelerate the advent of affordable Internet access and achieve the most efficient use of land.

Which companies are focusing on PERC battery technology?

At present, component companies such as TRW and Le Ye have been focusing on P-type battery technology manufacturing components. Yingli, Jingao and other component companies are focusing on N-type battery technology.

Tracking the predecessor of the PERC battery

The PERC battery (Passivated Emitterand RearCell) originated in the 1980s. In 1989, the Martin Green research team of the University of New South Wales in Australia officially reported the structure of the PERC battery at the Applied Physics Letter, which achieved a laboratory battery efficiency of 22.8%.

The PERL battery in the 1999 laboratory study created a world record of 25% conversion efficiency. Photolithography, evaporation, thermal oxygen passivation, electroplating and other techniques employed.

In 2006, the passivation effect of the passivated AlOx dielectric film on the backside of the P-type PERC battery attracted attention, and the PERC technology began to gradually become industrialized.

Around 2013, manufacturers began to introduce PERC battery production lines. In recent years, PERC batteries have attracted more and more attention from the industry, and their production capacity has expanded rapidly.

In 2017, the global new production capacity expected to be 6.5GW, 2.5GW from the existing standard battery line. It expected that by the end of 2017, the global PERC battery capacity would reach 20GW.

It is worth mentioning that 2017 will be a turning point in the market share of PERC batteries and conventional batteries. With the expansion of PERC battery capacity, the market share of conventional batteries will gradually decline.

Current development trend

At present, 80% of the global components are in the polycrystalline component market, with high cost performance, stable performance and low attenuation rate. However, as the cost of single crystal modules decreases, and the technical routes of P-type and N-type batteries continue to deepen, the proportion of single crystal modules in the market is gradually increasing.

Trina Solar's energy production is 21.15% positive and 12.27% on the back. Longji Leye reported a component power of 225W on the back of the 300W front.

1) The development of PERC technology exceeded expectations. The industrialization efficiency of monocrystalline cells reached 21.5%. The industrialization efficiency of polycrystalline PERC cells has reached more than 20% after the superposition of black silicon technology. It expected to achieve 21% polycrystalline PERC cells next year. Effectiveness. Compared with conventional batteries, PERC batteries show a good efficiency advantage, which can increase the absolute efficiency of 1-1.5% efficiency compared with conventional battery industrialization efficiency. Compared with high-performance PERT, HJT and other technologies, PERC battery industrialization efficiency is close, but has a better cost advantage.

4) The emergence of PERC double-sided batteries has once again increased the competitiveness of PERC batteries. At present, the double-sided rate of the double-sided PERC battery is about 75%, and the manufacturing cost is low. The double-sided PERC battery not only broadens the application scenario of the PERC battery, but also obtains higher power generation gain. The power generation of a large number of PERC double-sided component-power generation projects was collected and compared. In the case of different power generation seasons, different climate zones, and different backing surfaces, the power generation gain of 5 to 46% (including tracking) was reported.

PERC battery potential analysis

PERC batteries also have a lot of room for efficiency improvement. In the future, there will be room for optimization of the emitter, back aluminum backfield, main grid, and wafer quality. It is expected that even without important breakthrough technologies, single-crystal PERC batteries can achieve conversion efficiency of up to 24% around 2025, and the production line reaches 23%, which means that from now to 2025, there will be about 0.4% of absolute value per year. Efficiency has increased, and with the expansion of the PERC battery industry and technology optimization, it expected that the cost would reduce to half by 2025.

1) The development of PERC technology exceeded expectations and brought great impact to other types of crystalline silicon battery technology. The industrialization efficiency of single crystal cells has reached 21.5%. The industrialization efficiency of polycrystalline PERC cells has reached more than 20% after superimposing black silicon technology, and it expected to achieve 21% polycrystalline PERC battery efficiency next year. At the same time, PERC batteries have a cost advantage, and their cost is close to that of conventional batteries.

Compared with conventional batteries, PERC batteries show a good efficiency advantage, which can increase the absolute efficiency of 1-1.5% efficiency compared with conventional battery industrialization efficiency.

Compared with high-performance PERT, HJT and other technologies, PERC battery industrialization efficiency is close, but has a better cost advantage.

2) The single crystal polycrystal of the PERC battery is more of a dispute between high quality silicon wafers and low quality silicon wafers. In order to improve efficiency of battery conversion, whether it is PERC, PERT, PERL or HJT, IBC battery technology, more and more attention paid to the passivation of the battery surface. With the continuous improvement of the passivation quality, the influence of the composite defects in the silicon wafer will become more and more obvious, and the influence of the quality of the silicon wafer on the battery efficiency will be greater. Regardless of single crystal silicon or polycrystalline silicon, the future improvement of the crystal pulling/ingot process, the improvement of the quality of the silicon wafer, and the manufacture of high quality monocrystalline silicon wafers and high quality polycrystalline silicon wafers will be the development direction of PERC and other high-efficiency batteries.

3) The outdoor test results in Qinghai and Datong Evidence Base indicate that the single crystal PERC battery has certain power generation advantages and better unit power generation (kwh/kw). Sunlight irradiance, incident angle, temperature, and wind speed are key environmental parameters for component power generation testing. The comparison and analysis of outdoor power generation performance of different batteries is still in progress.

4) The emergence of PERC double-sided batteries has once again increased the competitiveness of PERC batteries. At present, the double-sided rate of the double-sided PERC battery is about 75%, and low manufacturing cost. The double-sided PERC battery not only broadens the application scenario of PERC battery, but also obtains higher power generation gain. The power generation of a large number of PERC double-sided component-power generation projects was collected and compared. In case of different power generation seasons, different climate zones, and different backing surfaces, the power generation gain of 5 to 46% (including tracking) was reported.

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