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What Are TOPCon Solar Cells?

Manufacturers of photovoltaic (PV) modules are always trying to find new, more advanced alternatives to increase solar panel efficiencies. Efficiency improvements can be achieved by innovative cell manufacturing technologies, and now, there are a few competing in the Solar PV market. 

The latest module trend expects that the market growth will be centred on HJT and TOPCon solar cells. 

The report from International Technology Roadmap for Photovoltaic (ITRPV) shows some expected trends for the next 10 years:

&#;  PERC (Passivated Emitter Rear Contact) solar cell technology currently is the market leader with market share of around 75%. But the forecast is that the share of p-type mono-Si PERC cells will decrease to about 10% within the next 10 years. 

&#;  N-type TOPCon (Tunnel Oxide Passivated Contact) technology will gain market share from about 10% in up to 60% in , becoming the mainstream silicon wafer type. It&#;s predicted that the biggest increase will happen from . 

&#;  N-type HJT (Heterojunction solar cells) is expected to increase from about 9% () to over 25% share within the next ten years. The implementation of HJT cell technology still suffers difficulties because of the higher production costs for solar cells and the incompatible production line with current technologies. This process won&#;t be covered in this article. 

 

 

P-type PERC vs N-type TopCon 

PERC technology is a cost-effective compromise between efficiency and mass production. But increasing solar panel efficiencies using this method happens at a slow rate. Today&#;s mainstream P-type modules reach efficiencies of around 21.4% that will increase to 22.75% within the next 10 years. 

A N-type TOPCon solar cell installed in a PV module looks identical to a PERC cell. P-type and N-type solar cells are both made from a silicon wafer. The difference between them lies in the way the wafers are doped with chemicals to improve electricity production. 

In a nutshell, P-type cells are doped with boron, while N-type cells are doped with phosphorus. Comparatively, phosphorus degrades less than boron when exposed to oxygen. In addition, phosphorus doping adds free electrons to the wafer, which increases efficiency. 

So, N-type based modules can achieve higher efficiencies. Today&#;s efficiencies of close to 22.5% will increase up to 24% or so within the next 10 years according to estimates. 

The problem with the N-type manufacturing process is that it is still more expensive. 

Advantages of TOPCon technology? 

1- Manufacturing process 

TOPCon modules can be manufactured with practically the same machines as P-type modules, which means the employment of TOPCon cells doesn&#;t require high capital investment for manufacturers. 

2- Higher efficiency 

According to the Fraunhofer ISE institute, efficiencies can go beyond 25%. PERC cell maximum theoretical efficiency is around 24%. 

3- Lower degradation 

TOPCon modules have a lower power degradation power during the 1st year and during the 30 years of PV panels use, compared to PERC panels. 

4- Lower temperature coefficient 

TOPCon cells have a better resistance to extreme weather scenarios. 

5- Bifaciality rate 

The bifacial factor for PERC PV modules has been determined on average to be at around 70% compared to up to 85% for TOPCon panels. They collect more energy from the rear side compared to PERC bifacial modules, which is favourable for ground-mount utility projects. Aesthetically, they can also be more attractive than PERC solar panels. 

6- Low light performance 

TOPcon modules have a higher efficiency in low light condition, which extends the electricity generation period during the day and improve the performance of the installation over time. 

Disadvantages of TOPCon technology? 

One of the major issues of TOPCon cells compared to PERC cells is that they require a larger amount of silver (Ag) for production. 

Both TOPCon and PERC use silver paste during production. However, TOPCon uses silver paste on both sides of the cells. This means that costs will never go lower than that of PERC. 

New manufacturing processes might be effective in reducing the required amount of silver, while still delivering similar or higher efficiencies. Lower costs, in return, will allow this technology to hit the market at reasonable prices. 

There are other technical issues mentioned elsewhere: boron deposition, different requirements for clean room conditions that must be met, and the inability of the current selective emitter to apply to the TOPCon front emitter. These issues are beyond the scope of this article.

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The efficiency and performance of solar cells have been constantly improving in recent years, one such development that has gained a lot of attention in the industry is the TOPCon solar cells (Tunnel Oxide Passivated Contact).

Recently TOPCon cell has been unstoppable in getting a historic innovation breakthrough, In October , Jinko revealed that the efficiency of TOPCon solar cell has exceeded 26.89%, which is the most efficient solar cell in the world.

In this blog post, we will take a closer look at TOPCon solar cell from&#;

• Working Principle
• Advantages
• Cost Components
• Comparison with PERC Mono

What Is A TOPCon Solar Cell

?

TOPCON stands for Tunnel Oxide Passivated Contact, TOPCON solar cell is a type of solar cell that uses a tunnel oxide layer to passivate the contact between the front and rear layers of the cell. 

This passivation layer reduces the recombination of charge carriers, improving the cell&#;s efficiency. TOPCon solar cells are also known for their excellent spectral response and low-temperature coefficient, making them ideal for use in hot and humid climates.

N-Type TOPCon Silicon Cells

Cells built on an N-type silicon substrate offer improved performance over the more common P-type silicon due to a greater tolerance to impurities which increases overall efficiency. In addition, N-type cells have a lower temperature coefficient compared to both mono and multi-P-type cells. N-type cells also have a much lower rate of LID or light-induced degradation and do not generally suffer from LeTID (light and elevated temperature-induced degradation) which is a common problem with P-type cells.

TOPCon or Tunnel Oxide Passivated Contact refers to a specialized rear-side cell passivation technique that helps reduce the internal recombination losses in the cell and boosts cell efficiency. The process has been available for several years but is now becoming the new industry standard as manufacturers strive to increase efficiency and performance.

How Do TOPCon Solar Cells Work?

TOPCon solar cells work by using a combination of layers and materials to capture and convert sunlight into electricity. The front layer of the cell is usually made of a highly-doped silicon material, while the back layer is made of a low-doped silicon material. The tunnel oxide layer is placed between the front and back layers to passivate the contact.

When sunlight hits the cell, it creates electron-hole pairs in the front layer. These charge carriers are then separated by an electric field and collected by metal contacts on the front and back of the cell. The passivation layer reduces the recombination of the charge carriers, which improves the efficiency of the cell.

 

 

Why Are TOPCon Solar Cells Revolutionary?

TOPCon solar cells have several advantages over traditional solar cells. Firstly, they have a higher efficiency, which means that they can generate more electricity from the same amount of sunlight. This makes them ideal for use in large-scale solar power plants, where maximizing efficiency is crucial.

Secondly, TOPCon solar cells have a lower temperature coefficient than traditional solar cells. This means that their efficiency does not decrease as much in hot and humid climates. This makes them ideal for use in regions with high ambient temperatures, such as the Middle East and Africa.

Finally, TOPCon solar cells have an excellent spectral response. This means that they can generate electricity from a wider range of the solar spectrum, including the blue and green parts of the spectrum. This makes them ideal for use in areas with high levels of diffuse light, such as cloudy or overcast regions.

 

What Are the Advantages of  TOPCon Technology?

Manufacturing process: TOPCon cells are manufactured using the same machines as P-type cells, eliminating the need for high capital investment and reducing manufacturing costs.

High Efficiency: Compared to P-type solar cells, n-type solar panels TOPCon cells can convert sunlight more efficiently and achieve higher conversion efficiencies of up to 28%, which is higher than the maximum efficiency of PERC cells.

TOPCon cells use ultra-thin silicon oxide and silicon nitride as the tunneling layer, which can significantly reduce the surface compound loss and increase the open-circuit voltage, and its conversion efficiency has already exceeded 25%, with a theoretical efficiency upper limit comparable to or even higher than that of HJT.

Low Degradation: Compared to PERC cells, TOPCon cells have lower power degradation in the first year and after 30 years of use, extending the life of the module.

Low-temperature coefficient: TOPCon cells perform better at high temperatures with lower output power loss, giving them higher efficiency in hot climates.

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Bifacial power generation: TOPCon cells also support bifacial power generation, which further enhances system power generation. In bifacial solar panels, TOPCon cells provide a better power boost, contributing to improved bifacial module performance.

Low-light performance: N-type IBC solar panels show higher efficiency in low-light conditions, extending daytime power generation and improving long-term performance.

Compatibility: TOPCon technology has good compatibility with existing PERC production lines and can be retrofitted and upgraded at low cost, which helps to quickly realize large-scale production and reduce costs.

Cost reduction path: With the advancement of material and process technologies, such as wafer thinning, metallization paste improvement, and equipment localization, the cost of TOPCon cells is expected to further decrease.

Cost Components of  TOPCon Cells

Why are TOPCon cells the most expensive of the common cells on the market? Generally speaking, the cost composition of solar cells can include the following aspects. We have listed a few of the most significant cost factors in TOPCon&#;s cell manufacturing process, and you can learn more about their percentages in the chart below.

• Material costs: Semiconductor materials (e.g., silicon, chalcogenide, etc.), conductive materials, glass substrates, back sheets, etc., are required for manufacturing cells. Also POE film, EPE, EVA materials, and other auxiliary materials
• Manufacturing process costs The cost of equipment, labor, and energy in the manufacturing process.
• Design and R&D Costs: Involves the costs required for cell design and technology development, as well as testing and validation costs.
• Production Efficiency: The efficiency and throughput of the production process affect costs, and higher production efficiencies can often reduce manufacturing costs per unit of product.
• Management and operational costs: A range of expenses such as management, sales, and marketing.
• Governance and Regulatory Costs: Compliance with environmental regulations and industry standards may add some costs.

 

Encapsulation Options for TopCon Single-Glass Solar Panels

TopCon single-glass solar panels offer a variety of encapsulation options to meet diverse market needs. For cost-effective choices, they use standard EVA film, high-transparency EVA film, and high-efficiency TOPCon cells, complemented with a standard back sheet. If the requirement leans towards high efficiency, one can opt for EVA or EPE film, coupled with white EVA film to enhance reflectivity and incorporate TOPCon cells to ensure high power output. For aesthetically pleasing products, options include EVA or EPE film, special black infrared-reflective film to improve appearance, and TOPCon cells to ensure beauty and efficiency. These choices allow consumers to select the solar panel encapsulation that best suits their specific needs and budget

More Economical EVA Film, TOPCon Cells, High-Transparency EVA Film, Backsheet More Efficient EVA Film/EPE Film, TOPCon Cells, White EVA Film, Backsheet More Aesthetic EVA Film/EPE Film, TOPCon Cells, Black Infrared Reflective Film, Backsheet

TOPCon Solar Cell Vs. PERC Solar Cell

According to third-party organizations&#; overall forecasts and current TOPCon solar cell production, in the future TOPCon will become one of the three mainstream cells with PERC and HJT cells, as high power generation efficiency is the trend of the market. After the cost breakthrough, the TOPCon solar cell may even become the highest yield, the most widely used solar cell.

What is the difference between TOPCon and PERC solar cells? &Why is TOPCon better than perc? TOPcon offers higher efficiency and better bifacial performance but requires more silver, which can increase production costs. The competition and ongoing research and development in the solar industry will likely continue to shape the relative market positions of these two technologies in the coming years.

TOPCon and PERC are two different types of solar cells that are used in the photovoltaic industry. TOPCon stands for Tunnel Oxide Passivated Contact, while PERC stands for Passivated Emitter and Rear Cell.

Competitiveness

According to the Fraunhofer Institute study, TOPCon solar cells are making strides towards competing with PERC cells. However, to gain more market share, TOPCon needs to work on improving its efficiency and reducing production costs.

Efficiency

TOPCon solar cells have a higher efficiency rate compared to PERC cells. Specifically, TOPCon boasts an efficiency of 26.1%, while PERC has an efficiency of 24.5%. Higher efficiency is generally desirable because it means more electricity can be generated from the same amount of sunlight.

Bifaciality

Bifaciality is a measure of how effectively a solar cell can capture light from both the front and rear sides. TOPCon cells have a higher bifaciality factor, at 85%, than PERC cells with a 70% bifaciality factor. This can make TOPCon cells more versatile in certain applications where sunlight can be reflected onto the rear side of the cell.

Metallization

One important consideration is the amount of silver required in the metallization process for these cells. TOPCon cells require more silver, around 130-150mg per piece, while PERC cells use less silver, approximately 85mg per piece. This increased use of silver can contribute to higher production costs for TOPCon cells.

Solar Cell Type Formation Efficiency Cost Performance in High Temperatures Mono PERC Similar to mono-crystalline cells, with an added passivation layer at the rear Outperforms traditional mono-crystalline cells Marginally more expensive, justified by improved efficiency Demonstrates superior performance in high temperatures compared to traditional mono-crystalline cells TOPCon Utilizes a tunnel oxide layer to passivate contacts on the rear side Generally boasts higher efficiency This can be higher due to increased manufacturing complexity, offset by efficiency gains Displays commendable performance in high-temperature conditions HJT Integrates amorphous silicon layers with crystalline silicon, forming heterojunctions Often achieves higher efficiency Initially higher due to more intricate manufacturing processes, potential cost reduction over time due to economies of scale Generally excels in high-temperature conditions due to lower temperature coefficients

TOPcon VS Mono PERC Production Impact

TOPcon VS Mono PERC production impact is reflected in the following areas: the PERC Mono and TOPCon processes have different requirements for production equipment.  Although the PERC process and TOPCon are somewhat similar in principle, the production process and equipment cannot be fully shared, and generally only non-core equipment such as chemical treatment, flocking, and some testing can be shared.

Cell Structures

-PERC Cells: PERC cells have a passivated emitter rear contact structure. The passivation layer, oxide layer, and polysilicon layer are significant components of PERC cell structure.

-TOPCon Cells: TOPCon cells have a different structure, especially in terms of the passivation layer, oxide layer, and polysilicon layer.

Production Challenges

-Both PERC and TOPCon cells present challenges in the production process, such as difficult process preparation and high product discreteness.

-High requirements on process environment, technology, and industrial digital management are needed for both technologies.

Production Line Characteristics:

-The TOPCon cell process closely resembles semiconductor MOS (Metal-Oxide-Semiconductor) process characteristics.

-Clean room level requirements differ between TOPCon and PERC cell production lines.

Mono PERC cells have passivated contacts on the front side, while TopCon cells have passivated contacts on the back side. Due to the backside contact design, additional steps may be required to manufacture TopCon cells, which may impact production costs.

Equipment Requirements:

Due to the differences in cell structures and production processes, the equipment requirements for PERC and TOPCon cells are distinct.

While some principles may be similar, sharing is generally limited to non-core equipment, including chemical processing, velvet (possibly referring to wafer polishing), and some testing equipment.

Production Line Yield
-TOPCon is 98.5%, and now there is a big difference in what each company announces, from 90-95%.

-PERC is about 98%.

Number of Processes
-PERC consists of 11 processes

-TOPCon consists of 12 processes

Equipment Investment
-The investment cost for PERC is $ Million/kW

-TOPCon is $ Million/kW.

Conclusion

TOPCon solar cells have proven to be a game changer in solar energy, offering significantly higher efficiency and improved performance compared to traditional solar cells. With its potential to reduce the cost of solar energy, TOPCon technology has the potential to play a crucial role in the transition toward a more sustainable and carbon-neutral energy system. As research and development continue, we can expect to see even more impressive advancements in TOPCon technology, making solar energy an increasingly viable and attractive source of renewable energy for the future.

FAQs About TOPCon Solar Cell

Q: Why is TOPCon better than PERC?
A: TOPCon (Tunnel Oxide Passivated Contact) is an n-type solar cell with higher efficiency and voltage than PERC (Passivated Emitter Rear Cell), a p-type solar cell. TOPCon&#;s features include a thin tunnel oxide layer, reducing recombination, and a polycrystalline silicon layer on the rear side, improving passivation and reducing resistance.

Q: Is mono PERC more efficient than monocrystalline?
A: Yes, Mono PERC, a type of monocrystalline solar cell, is more efficient than conventional monocrystalline cells. It includes a thin dielectric layer on the rear side, enhancing light absorption and current. Additionally, Mono PERC cells have fewer impurities and defects, reducing recombination and increasing voltage.

Q: What are the benefits of mono PERC panels?
A: Mono PERC panels offer higher efficiency and power output, especially in challenging conditions. They have a lower degradation rate and longer lifespan than conventional monocrystalline panels. Moreover, Mono PERC panels have lower production costs and environmental impact, utilizing less silicon and energy.

Q: What is the advantage of TOPCon compared to HJT?
A: TOPCon has advantages over HJT (Heterojunction Technology), including lower production costs and simplicity. HJT, while efficient, involves a high production cost and complexity due to the use of amorphous silicon layers on both sides of the crystalline silicon wafer. HJT is also more sensitive to humidity and degradation than TOPCon.

Q: What is the efficiency of TOPCon vs PERC?
A: The theoretical efficiency of TOPCon cells is 28.7%, exceeding the theoretical efficiency of PERC cells, which is 24.5%. In mass production, TOPCon cells achieve greater than 24% efficiency, while PERC cells achieve around 23%.

Q: What is the difference between PERC and TOPCon?
A: The main difference lies in the silicon type and rear cell structure. PERC uses p-type silicon with a dielectric layer on the rear side, reflecting light. TOPCon uses n-type silicon with a tunnel oxide layer and polycrystalline silicon on the rear side, improving passivation and reducing resistance.

Q: What is the efficiency of mono PERC?
A: The efficiency of mono PERC cells varies based on factors like wafer size, quality, cell design, and environmental conditions. On average, mono PERC cells have around 22% efficiency, with the highest efficiency reaching approximately 25%.

Q: What is the difference between mono PERC and monocrystalline?
A: Mono PERC is a type of monocrystalline solar cell with higher efficiency. It includes a thin dielectric layer on the rear side, reflecting light back to the cell and reducing recombination. Mono PERC also has fewer impurities and defects compared to conventional monocrystalline cells.

Q: What are the disadvantages of monocrystalline panels?
A: Monocrystalline panels have drawbacks, such as higher production costs and environmental impact compared to polycrystalline or thin-film panels. They also exhibit lower performance and efficiency than n-type or bifacial panels, with higher sensitivity to shading and dirt. Monocrystalline panels have a lower tolerance to partial shading and are more prone to dust accumulation.

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