Topcon solar cells vs Perc solar cells: a complete guide

Harnessing solar energy has become a vital component of our quest for sustainable power sources. As the solar industry continues to evolve, different technologies have emerged to make the most of our abundant sunlight. Three of the most prominent contenders in the solar cell arena are Topcon, HJT (Heterojunction Technology), and PERC (Passivated Emitter Rear Cell) solar cells. Each of these technologies offers distinct advantages and disadvantages, making it crucial for consumers and industry professionals alike to understand the differences between them.

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We&#;ll delve into the world of solar cells and explore the nuances that set Topcon, HJT, and PERC solar cells apart, helping you make informed decisions.

Comparison Between PERC Solar Cells and TOPCon Solar Cells Technology

When comparing PERC and TOPCon solar cell technologies, it&#;s worth noting that visually, they appear quite similar once installed wi

thin a module. However, there are key distinctions between them. TOPCon cells are crafted from n-doped silicon, which is a more complex material to work with during manufacturing. Nonetheless, this material enables TOPCon cells to attain higher levels of efficiency.

Another notable contrast lies in the meticulous passivation process applied to TOPCon cells. While it presents technical challenges, this process delivers significant benefits. Specifically, the application of a polycrystalline silicon layer to the cell&#;s rear side demands substantial technical expertise. However, it enables the solar cell to withstand higher voltages, ultimately leading to a notable increase in overall efficiency.

Comparing HJT Solar Cell and TOPCon Solar Cell Technologies

HJT panels excel in efficiency and bifaciality, but their manufacturing is complex and costly, and they&#;re susceptible to humidity.

In contrast, TOPCon panels offer a simpler, cost-effective manufacturing process with reduced sensitivity to humidity, but they trade off some efficiency and bifacial performance when compared to HJT panels.

Topcon Solar Panel

TOPCon, &#;Tunnel Oxide Passivated Contact,&#; represents an innovative leap in solar cell technology. This cutting-edge technology is making waves in the renewable energy industry due to its unique structure and remarkable efficiency gains. In a TOPCon solar cell, a delicate tunnel oxide layer is strategically placed between two crucial components: a transparent conductive oxide (TCO) layer and a p-doped crystalline silicon layer.

The TCO layer serves as the front contact of the solar cell, allowing sunlight to pass through and interact with the underlying layers. Meanwhile, the p-doped crystalline silicon layer functions as the absorber layer, absorbing the solar radiation and converting it into electrical energy. However, what truly sets TOPCon apart is the tunnel oxide layer&#;s role as a passivation layer.

This passivation layer plays a pivotal role in preventing the undesirable recombination of charge carriers at the solar cell&#;s surface. By mitigating this recombination, TOPCon solar panels achieve a higher level of efficiency, maximizing their ability to capture energy from the sun per unit of surface area.

Advantages of TOPCon Solar Panels

• Cost-Effective Manufacturing:

  No need for expensive machinery, making large-scale production easier.

• Higher Efficiency:

  Up to 28% efficiency, surpassing PERC cells for more power generation.

• Lower Degradation:

  Longer lifespan with minimal power degradation over time.

• Low-Temperature Sensitivity:

  Maintains efficiency even in hot climates.

• Enhanced Bifaciality:

  Generates electricity from both sides.

• Strong Low-Light Performance:

  Efficient even in low-light conditions.

Disadvantages of TOPCon Solar PV Module Technology

• Higher Production Costs:

  Additional materials and complexity can increase production expenses.

• Complex Manufacturing:

  Challenging to scale production to meet high demand.

• High-Temperature Processing:

  Elevated energy consumption, emissions, and potential cell damage.

• Sensitivity to Impurities:

  Prone to efficiency reduction or failure due to material impurities.

Uses of Topcon Solar Panels

• Utility-Scale Solar Farms:

  These panels excel in utility-scale solar power plants, maximizing electricity production within limited space thanks to their high efficiency.

• Agriculture and Farming:

  TOPCon panels prove valuable in agricultural settings, powering water pumps, irrigation systems, and crop drying processes, offering off-grid energy solutions to remote regions.

• Electric Vehicle Charging:

  Leveraging their capabilities, TOPCon solar panels drive electric vehicle charging stations, promoting clean and sustainable transportation options.

Perc Solar Panels

In recent years, there has been a surge in the popularity of Passivated Emitter and Rear Contact (PERC) solar panels within the solar industry due to their ability to enhance solar power efficiency. These panels utilize PERC solar cells, an upgraded iteration of traditional solar cells. With their innovative design, they can produce 6 to 12 % more energy compared to their conventional counterparts.

The acronym PERC stands for Passivated Emitter and Rear Cell. The distinctive feature of a PERC solar cell is the presence of a passivation layer on its rear side, which plays a pivotal role in reducing recombination losses and boosting light absorption. Essentially, the rear-side passivation layer acts as a light reflector, preventing sunlight that passes through the silicon cell from escaping without absorption. This reflective capability provides the solar cell with a second opportunity to absorb the light, resulting in a significant enhancement in overall efficiency.

Advantages of PERC Solar Panels

• Enhanced Energy Production:

  PERC panels boast higher efficiency, leading to a potential 5% increase in energy production for an entire (PV) stands for  Photovoltaic system.

• Improved Low-Light and High-Heat Performance:

  PERC panels excel in low-light and high-temperature conditions, delivering approximately 3% higher efficiency.

• Superior Area Efficiency:

  Thanks to their increased efficiency, PERC panels can achieve the same power output as traditional panels using fewer units, reducing the installation space required.

• Lower Balance of System (BOS) Costs:

  Fewer PERC panels can achieve equivalent output, resulting in reduced BOS costs, labor expenses, and soft costs like inverters and disconnects.

Disadvantages of PERC Solar Panels

• Higher Cost:

  PERC solar panels generally come at a higher price point compared to traditional panels.

• Shading Sensitivity:

  PERC panels are slightly more susceptible to shading issues than traditional solar panels.

• New Technology Uncertainty:

  As a relatively new technology, there may be some uncertainty regarding the long-term durability and performance of PERC solar panels.

Uses of Perc Solar Panels

• Commercial Buildings:

  Mono PERC solar panels find application in commercial structures like office buildings, shopping centers, and warehouses, helping cut electricity expenses and lower carbon footprint.

• Large-Scale Solar Farms:

  Mono PERC solar panels are deployed in utility-scale solar power plants, contributing to the generation of electricity on a grand scale.

HJT

Heterojunction (HJT) solar cell technology has emerged as a promising and relatively recent innovation in the field of solar cells, gaining significant traction in recent years due to its enhanced efficiency in converting sunlight into electricity.

Heterojunction solar panels are a specific type of photovoltaic panel characterized by a tri-layered structure, integrating two distinct technologies: crystalline silicon and amorphous &#;thin-film&#; silicon, synergistically optimizing electricity production.

HJT cells are composed of three key materials: Crystalline Silicon (c-Si), Amorphous Silicon (a-Si), and Indium Tin Oxide (ITO).

The initial layer, consisting of amorphous silicon, intercepts sunlight even before it reaches the crystalline layer, as well as any light that bounces off the underlying layers. The middle layer is composed of monocrystalline silicon, primarily responsible for converting the majority of sunlight into electricity. Finally, there is another amorphous thin-film silicon layer situated behind the crystalline silicon layer, capturing any remaining photons that have managed to penetrate the first two layers.

Through the harmonious combination of these two distinct technologies, heterojunction solar panels can harness more energy than either technology could achieve individually. These panels can achieve impressive efficiencies exceeding 25%, making them an increasingly attractive option for solar energy generation.

Advantages of HJT Solar Panels

• High Efficiency:

  HJT panels boast exceptional efficiency, reaching up to 30% for bifacial modules.

• Temperature Resilience:

  They perform well in high-temperature environments due to a favorable temperature coefficient.

• Bifacial Capability:

  HJT cells exhibit a high bifaciality factor of 92%, ideal for utility-scale projects.

• Stramlined Manufacturing:

  HJT modules require only 5-7 manufacturing steps, reducing production costs.

Disadvantages of HJT Solar Panels

• High Cost:

  HJT panels are pricier due to complex manufacturing and costly materials.

• Fragile Structure:

  Their thin, intricate design makes them susceptible to damage.

• Sensitivity to Moisture:

  HJT panels are moisture-sensitive, affecting efficiency and durability.

• Complex Production:

  Specialized equipment and expertise are needed for manufacturing.

• Limited Scale:

  Production is smaller, potentially increasing costs and limiting availability.

• New Technology:

  Installation and maintenance experience may be limited due to their recent introduction.

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Uses of HJT Solar Cell

• Building Integration:

  HJT solar panels seamlessly blend into building facades, roofs, and windows, adding both aesthetic appeal and energy efficiency to structures.

• Compact Applications:

  In space-limited scenarios like portable solar chargers, off-grid cabins, and small boats, HJT solar panels excel due to their compact size and impressive efficiency.

• Utility-Scale Solar Farms:

  HJT panels find a valuable role in large-scale solar power plants, particularly in regions with abundant solar irradiance, enhancing overall efficiency for these expansive energy projects.

Parting Thoughts

The world of solar cell technology is rapidly evolving, with TOPCon, HJT, and PERC solar cells emerging as prominent contenders. Each technology brings its own set of advantages and disadvantages to the table, catering to diverse applications and preferences.

When choosing among these technologies, it&#;s essential to consider factors such as cost, efficiency, environmental conditions, and specific application requirements. Ultimately, the decision depends on your goals and the unique circumstances of your solar energy project.

To continue advancing in the solar industry, it is crucial for Novergy to stay informed about cutting-edge technologies. This knowledge is essential to unlock the full potential of solar power for a sustainable future.

Our experienced team is ready to assist you in finding the best solar solution through services such as site evaluation, feasibility studies, and installation.

Contact us at for more information.

FAQ&#;s

Q- What is the full form of PERC?

Answer- Full form of PERC is &#;Passivated Emitter and Rear Cell.&#; It refers to a type of solar cell technology designed to improve the efficiency of photovoltaic (PV) cells.

Q- What is the meaning of PV

Answer- PV stands for &#;Photovoltaic,&#; a technology that converts sunlight into electricity.

Solar cell technology used to manufacture photovoltaic (PV) modules is constantly evolving as new, more advanced and more efficient technologies are developed. Tunnel oxide passivated contact (TOPCon) solar cell technology is a new development with the potential to replace passivated emitter and rear contact (PERC) and high-efficiency passivated emitter, rear totally-diffused (PERT) solar panels.

TOPCon solar cells represent an upgraded and more efficient technology compared to PERC/PERT solar cells, featuring a highly similar structure.

In this article, we will explain important details on this technology, going from the basics, structure and manufacturing, comparison against other popular technologies in the solar industry, advantages and disadvantages, and more.

Tiger Neo bifacial TOPCon solar panel - Source: Jinko Solar

TOPCon solar cell technology: Understanding the basics

TOPCon solar cell technology is one of the latest trends in the solar industry, developed as an upgraded and more advanced version of the PERC/PERT technology. One of the main advantages of TOPCon solar cells is that the structure is only slightly different from PERC/PERT solar cells, meaning that manufacturers can use practically the same production line with a few improvements to produce TOPCon solar cells.

TOPCon solar cell technology was first introduced as a concept in by the Fraunhofer ISE German PV research institute. The project designed to develop this technology took place from to , but it was not until that companies like Trina Solar scaled it to production. As TOPCon solar cell technology proved as a successful upgrade from PERC solar cells, many other companies including LONGi Solar, Suntech, Canadian Solar, and many others got interested in it.

The main setback of this new technology compared to PERC/PERT is that the TOPCon solar cells require a larger amount of silver (Ag) for production. This silver increase translates into a higher manufacturing price; however, new developments might prove successful in reducing the required amount of silver, while still delivering similar or even higher efficiencies and reducing production costs.

Structure and manufacturing of TOPCon solar cells

TOPCon solar cell technology features a similar structure and manufacturing process to PERC solar cells, featuring only a few additional steps. In this section, we explain how both of these work:

Structure of the TOPCon solar cell

TOPCon solar cells can be manufactured as n-type or p-type solar cells, but the n-type variation has proven to be more efficient and resistant to impurities. Because TOPCon solar cells are an upgrade from PERC/PERT solar cells, it is important to understand the structure of this new technology.

PERT solar cells are manufactured with an n-type crystalline silicon (c-Si) bulk layer because of its higher surface quality and it is coupled with a p+ emitter layer to create the p-n junction. The emitter layer is covered with an aluminum oxide (Al2O3) passivating layer and topped with a silicon nitride (SiNx) coating for its anti-reflecting properties. PERC solar cells replace the absorber layer with a p-type bulk layer and an n+ emitter for the p-n junction.

The lower part of the bulk region is doped with phosphorous to create the back surface field, and it is then coated with SiNx similar to the top of the cell. Both the top and bottom of the solar cell are equipped with silver (Ag) or aluminum (Al) contacts to close the circuit when the cell is being connected to the load or other cells at the time of manufacturing the PERC/PERT solar panel.

 TOPCon solar cell structure - Source: Scholarly Community Encyclopedia

The PERC/PERT solar cell structure has proven to be quite efficient since it was introduced to the market and implemented to manufacture PV modules, but researchers found ways to improve it and therefore created the TOPCon solar cell.

The TOPCon solar cell structure takes the base structure of the PERT solar cell but includes an ultra-thin silicon dioxide (SiO2) layer working as the tunnel oxide layer and replaces the back surface field layer with phosphorous-doped polycrystalline silicon (n+ Poly-Si) layer. These modifications have improved the efficiency by reducing the recombination process thanks to the passivation in the added layers.

Manufacture of a TOPCon solar cell

One of the best things about TOPCon solar cell technology is that the manufacturing process is so similar to that of PERT solar cells that manufacturers will only have to make a little investment to upgrade their existing production line. Most of the manufacturing equipment can remain the same. This makes TOPCon solar cells an excellent investment for PERC/PERT PV module manufacturers already in the market.

1. The first step to manufacturing a TOPCon solar cell is chemically texturing the wafer surface by using a potassium hydroxide (KOH) to remove saw damage from the cutting process of the c-Si wafer.
2. After cleaning the wafer, the diffusion method is used to form the emitter on the front side of the cell by applying a boron tribromide (BBr3) gas, but then the backside emitter is removed by applying a nitric acid and hydrofluoric acid (HF/HNO3) solution, and the ultra-thin oxide layer is produced through wet chemical dipping.
3. To grow the n+ Poly-Si layer, a phosphorous-doped amorphous silicon (n-a-Si:H) layer is grown through a plasma-enhanced chemical vapor deposition (PECVD) process. This is then transformed into the n+ Poly-Si layer after annealing at 900ºC.
4. The solar cell is cleaned further, and the passivation and coating layers are applied through PECVD.
5. Finally, the Ag/Al contacts are applied through screen printing for the metallization using a quick-firing method with a maximum temperature of 760ºC.

After the TOPCon solar cells are manufactured, I-V solar cell curve characterizations are performed to evaluate their performance.

There are only a few additional steps required to manufacture a TOPCon solar cell instead of the PERT solar cell, making this new technology financially attractive for the solar industry.

How do TOPCon solar cells compare against the most popular PV technology in the market?

Power degradation of TOPCon cell over its 30-Year lifespan - Source: Jinko Solar

TOPCon solar cell technology is quite promising, having the potential to rapidly grow within the solar industry. When considering a new rising technology like this one, it is important to analyze it against other popular PV technologies in the market. In this case, we will compare TOPCon solar cell technology against PERC and heterojunction (HJT) solar cell technologies.

Highest EfficiencyTemperature CoefficientBifaciality FactorMarket ShareTOPCon26.10%<0.3%/ºC85%8% ()PERC24.50%<0.4%/ºC70%75% ()HJT26.56%0.21%/ºC92%2.5% ()

PERC solar cell technology currently sits in the first place, featuring the highest market share in the solar industry at 75%, while HJT solar cell technology started to become adopted in , its market share was only 2.5% by . TOPCon, which is barely present in the market, already represents 8% of the PV market, but it might start to grow in as major manufacturers switch from PERC/PERT to TOPCon.

Considering the technical specs, PERC technology is left behind by both HJT and TOPCon solar cell technologies. While PERC features a 24.5% efficiency and 70% bifaciality factor, TOPCon takes the efficiency to 26.1% and the bifaciality factor to 85%, while HJT goes even further with an efficiency of 26.56% and bifaciality factor of 92%. The temperature coefficient for PERC solar cells is worse when compared to TOPCon with its 0.3%/ºC, while HJT solar cells go even lower than that to 0.21%/ºC.

HJT solar cells might look quite promising, but there are major setbacks to this technology because of the higher production cost for solar cells and the incompatible production line with current technologies. This is where TOPCon solar cells have a head start since the required production line for TOPCon solar cells is practically the same as PERC/PERT and the cost is also quite similar.

Considering the similarity between the technical specifications of HJT and TOPCon solar cells, but factoring in the setbacks of HJT technology, it is understandable why major manufacturers like Trina Solar, Jinko Solar, LONGi, and others, are opting for TOPCon solar cells instead of HJT.

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Advantages & disadvantages of TOPCon solar cells

TOPCon solar cells feature a few differences from PERC/PERT solar cells but greatly improve performance. In this section, we present the advantages and disadvantages of TOPCon solar cells.

Advantages

Little capital investments for PERC/PERT manufacturers

TOPCon solar cell technology is an upgrade of PERC/PERT solar cells, featuring two additional steps. This little difference between both technologies, allows manufacturers of PERC and PERT solar cells to upgrade to TOPCon by adding only a few pieces of equipment for a little investment.

Higher efficiency reported by several manufacturers

One of the main features of TOPCon solar panels is the higher efficiency achieved. According to the Fraunhofer ISE institute, efficiencies can go beyond 25%. This has already been proved by PV manufacturers like LONGi, Jinko Solar, and others, with a high efficiency of 26.1%.

Better performance as a result of a lower temperature coefficient

Traditional PV modules feature a temperature coefficient of 0.4%/&#;-0.5%/&#;, while PERC PV modules perform better by taking that coefficient slightly under the 0.4%/&#; frame. TOPCon PV modules manufactured by Jinko Solar, on the other hand, have already proven to take the temperature coefficient to less than 0.3%/&#;, highly improving their performance in many extreme weather scenarios.

15% higher bifacial factor

The bifacial factor for PERC PV modules has been determined on average to be at around 70%. TOPCon solar panels, on the other hand, have proven to take the bifacial factor up to 85%. This increased bifacial factor can increase power gains by as much as 2%.

Disadvantages

Several challenges in the manufacturing process

TOPCon solar cell technology is still facing several challenges in the manufacturing process. Some of these include different opinions on the best technique for boron deposition, different requirements for clean room conditions that have to be met, and the inability of the current selective emitter to apply to the TOPCon front emitter. For the solar industry to advance with TOPCon, these issues should be addressed.

There is little data about mass production, limiting the roadmap for the future

Different companies upgrading their PERC/PERT lines of production to TOPCon solar cells have taken different routes, but since there is limited mass production, the roadmap for this technology is still under development. As major companies like Trina Solar, LONGi, and others start to tackle major problems and find optimal ways to produce TOPCon solar cells, the roadmap will become clearer.

Higher silver requirement equals higher price

One of the major issues of TOPCon solar cells is a higher requirement of silver to print the contacts on the cell. The ideal option to reduce costs would be to increase efficiency while maintaining current costs. Lowering the costs for this technology is imperative to hit the market at reasonable prices.

Market trends featuring TOPCon solar cells

The market trends have shifted in the last decade from back surface fields (BSF) solar panels to PERC solar cell technology, and now it seems to be shifting to TOPCon solar panels. Initially, BSF solar panels ruled the market, but manufacturers began the adoption of PERC solar cell technology and the market share grew until hitting 40% in , and almost 75% by . Since TOPCon solar cell technology is a cost-efficient upgrade from PERC/PERT solar cells, this new technology may soon rule the market.

In , LONGi announced a new record for high-efficiency n-type solar panels at 25.21% featuring TOPCon solar cell technology. Little after that, Jinko Solar announced an even higher efficiency record at 25.4%. In , Trina Solar broke the record with an efficiency of 25.5%, while Canadian Solar also reached a high efficiency of 25.0% that same year. By the end of , Jinko Solar broke the record two times in a row, first reaching 25.7% and then 26.1%.

Many PV manufacturers will start to fill the market with TOPCon solar panels as they design and release their products. LONGi launched its bifacial TOPCon solar panels at the SNEC , and Suntech released its Ultra VPro Series in , but it seems that will be the year when most PV manufacturers release their products. Jinko Solar unveiled three different TOPCon solar panel variants with a  power rate going from 445W to 635W, Canadian Solar is also hitting the market with solar panels that go up to 690W, and Trina Solar unveiled its new TOPCon solar panels that go up to 445W.

These are only some of the largest manufacturers, but as the technology advances, other major companies in the solar industry will also release TOPCon solar panels. There is a considerable possibility that as TOPCon solar cell technology becomes more popular, PERC solar panels will start to give way to TOPCon to increase its market share and presence in the industry.

Present and future of TOPCon solar cells

TOPCon solar cell technology is a revolutionizing product that upgrades the design of the PERC/PERT solar panels.

This technology has already proven its worth by reaching efficiencies that approach the Shockley-Queisser limit for single p-n junction solar cells and deliver a better performance in general.

The solar industry is starting to get acquainted with TOPCon solar cell technology. LONGi already launched its bifacial modules in , but most manufacturers will be releasing their high-efficiency TOPCon solar panels from the second (Q2) to the last quarter (Q4) of .

It is possible that at first, TOPCon solar cell technology will have slightly more expensive costs than PERC/PERT solar panels, but analysts expect that the cost for TOPCon solar panels will fall lower than the current cost of PERC solar cell technology.

The path for TOPCon solar cell technology is also not entirely free from competition. There are other technologies featuring an interesting great potential to go against this newly upgraded technology, including HJT as it is further developed, and interdigitated back-contacted (IBC) solar cell technology.

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