Overview of Topcon photovoltaic module technology and ...

Overview of Topcon photovoltaic module technology and advantages

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TOPCon (Tunnel Oxide Passivated Contact) photovoltaic (PV) module technology represents the latest advancements in the solar industry for improving cell efficiency and reducing costs. The core of the TOPCon technology lies in its unique passivation contact structure, which effectively reduces carrier recombination at the cell surface, thereby enhancing the cell's conversion efficiency.

Technical Highlights

1. Passivation Contact Structure: TOPCon cells prepare a super-thin oxide silicon layer (1-2nm) on the back of the silicon wafer, followed by the deposition of a doped polycrystalline silicon layer. This structure not only provides excellent interface passivation but also forms a selective carrier transport channel, allowing majority carriers (electrons) to pass through while preventing minority carriers (holes) from recombining, thus significantly increasing the cell's open-circuit voltage (Voc) and fill factor (FF).

2. High Conversion Efficiency: The theoretical maximum efficiency of TOPCon cells is as high as 28.7%, significantly higher than the 24.5% of traditional P-type PERC cells. In practical applications, the mass production efficiency of TOPCon cells has exceeded 25%, with potential for further improvement.

3. Low Light-Induced Degradation (LID): N-type silicon wafers have a lower light-induced degradation, meaning that TOPCon modules can maintain a higher initial performance in actual use, reducing performance loss over the long term.

4. Optimized Temperature Coefficient: The temperature coefficient of TOPCon modules is better than that of PERC modules, which means that in high-temperature environments, the power generation loss of TOPCon modules is smaller, especially in tropical and desert regions where this advantage is particularly evident.

5. Compatibility: TOPCon technology can be compatible with existing PERC production lines, requiring only a few additional devices, such as boron diffusion and thin-film deposition equipment, without the need for backside opening and alignment, simplifying the production process.

Production Process

The production process of TOPCon cells mainly includes the following steps:

1. Silicon Wafer Preparation: First, N-type silicon wafers are used as the base material for the cell. N-type wafers have higher minority carrier lifetime and better weak light response.

2. Oxide Layer Deposition: A super-thin oxide silicon layer is deposited on the back of the silicon wafer. The thickness of this oxide silicon layer is usually between 1-2nm and is the key to achieving passivation contact.

3. Doped Polycrystalline Silicon Deposition: A doped polycrystalline silicon layer is deposited on the oxide layer. This polycrystalline silicon layer can be achieved through low-pressure chemical vapor deposition (LPCVD) or plasma-enhanced chemical vapor deposition (PECVD) technology.

4. Annealing Treatment: High-temperature annealing treatment is used to change the crystallinity of the polycrystalline silicon layer, thereby activating the passivation performance. This step is crucial for achieving low interface recombination and high cell efficiency.

5. Metallization: Metal grid lines and contact points are formed on the front and back of the cell to collect photo-generated carriers. The metallization process of TOPCon cells requires special attention to avoid damaging the passivation contact structure.

6. Testing and Sorting: After the cell manufacturing is complete, electrical performance tests are conducted to ensure that the cells meet the predetermined performance standards. The cells are then sorted according to performance parameters to meet the needs of different markets.

7. Module Assembly: The cells are assembled into modules, typically encapsulated with materials such as glass, EVA (ethylene-vinyl acetate copolymer), and backsheet to protect the cells and provide structural support.

Advantages and Challenges

The advantages of TOPCon technology lie in its high efficiency, low LID, and good temperature coefficient, all of which make TOPCon modules more efficient and have a longer lifespan in actual applications. However, TOPCon technology also faces cost challenges, especially in terms of initial equipment investment and production costs. With continuous technological advancements and cost reduction, it is expected that the cost of TOPCon cells will gradually decrease, enhancing their competitiveness in the photovoltaic market.

In summary, TOPCon technology is an important direction for the development of the photovoltaic industry. It improves the conversion efficiency of solar cells through technological innovation while maintaining compatibility with existing production lines, providing strong technical support for the sustainable development of the photovoltaic industry. With continuous technological progress and cost reduction, TOPCon photovoltaic modules are expected to dominate the photovoltaic market in the future.

TOPCon has become the buzzword in the solar world.

Several manufacturers such as Canadian Solar, RenewSys, and Longi have launched their own TOPCon panels, each flaunting highly competitive efficiency rates. Moreover, there&#;s a growing anticipation that, in the coming years, TOPCon could surpass the widespread popularity of PERC solar cells.

But what is this technology and what are the benefits it offers?

In this blog, we will dive into all you need to know about TOPCon technology and understand what makes it stand out among conventional solar panels.

Why TOPCon?

Manufacturers are constantly trying to increase the efficiency of the solar panels. Efficiency here means the amount of light that a solar cell can convert to electricity.

This quest has birthed several module technologies such as HJT (Heterojunction with Intrinsic Thin Layer) solar cells, IBC (Interdigitated Back Contact) solar cells, PERC (Passivated Emitter and Rear Contact) solar cells, and TOPCon (Tunnel Oxide Passivated Contact) solar cells.

Right now, PERC cells are the most popular, reaching up to 22% efficiency. However, raising this efficiency rate in a sustained manner has posed a challenge for researchers. While HJT and IBC solar cells showed high efficiency, they are difficult to manufacture which makes mass production relatively unfeasible.

One standout in this race is TOPCon. It&#;s like an upgraded version of PERC and has shown a lot of promise. Although TOPCon technology originated in Germany in , researchers began a detailed examination of it only in .

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How are TOPCon Modules Made?

To understand TOPCon, it is important to learn about the PERC cell. Let&#;s delve a little deeper into technicalities.

PERC modules have a passivated layer attached to the back of the solar cells. This layer helps in re-reflecting the electrons that passed through the cells, back to the cell. As a result, electrons get a second chance at electricity generation. PERC raises the efficiency of the panels by 1%.

However, researchers found that by adding a few more layers to the PERC solar cell, its efficiency could be raised even further. A tunnel oxide and an intrinsically polysilicon layer are added to the rear side and a passivation and anti-reflective layer are added to the front of the solar cell.

These additions raise the overall efficiency of the solar cell and improve its performance in various weather conditions. This upgraded PERC cell, with its additional layers, came to be known as TOPCon.

Advantages of TOPCon

There are 3 major advantages of TOPCon panels:

1. Adaptable Manufacturing

As we discussed, the manufacturing process of TOPCon solar panels involves the addition of a few extra layers to the PERC solar cells. This makes it easy for facilities to adapt the existing production line for the creation of a completely new technology and keep the cost increase in check.

Many manufacturers have already begun reserving spaces for upgrading the PERC modules into TOPCon in their production facilities.

2. High efficiency

Under test conditions, TOPCon solar panels have demonstrated remarkable efficiency rates, reaching as high as 29.43%! The maximum efficiency of PERC solar cells, on the other hand, is close to 24%.

Even in real-world conditions, TOPCon panels convert more sunlight into energy than traditional solar panels. Consequently, these panels can produce more electricity in the same space.

For example, globally leading solar manufacturers, Canadian Solar, recently announced the mass production of their TOPCon modules which boast a maximum efficiency of 25%. The rating of the modules will be up to 690 W.

3. Better Performance

Apart from these, TOPCon modules are known to display better PV performance. These modules experience lower first-year degradation and subsequent efficiency decline over the following 25 years compared to traditional solar panels currently available in the market.

Moreover, the TOPCon modules display higher efficiency even in hot temperatures and low-light situations, which raises the overall generation of the panels.

The Verdict

TOPCon is a technology that shows a lot of potential. Studies have shown that it is highly efficient and reliable and has the potential to overtake PERC modules

However, the current drawback lies in the higher manufacturing costs compared to existing market modules. Manufacturers are actively expanding their production facilities to integrate TOPCon and address the increasing demand for solar solutions.

Despite these challenges, TOPCon proves to be an excellent choice for urban areas where suitable land or rooftop space for solar panel installation is limited.

About Ornate Solar

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By not only partnering with the best-in-class solar brands but also developing our high-quality solutions, (panels, inverters, accessories, InRoof), we develop and deliver solutions that are modern, reliable, and effective.

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