Evolution of The Solar Industry With Mono PERC, HJT & TOPCon Technology

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Difference between HJT , TOPCon & PERC solar panels

Solar panel manufacturing technology has come a long way over the years, and there have been significant advancements recently with the introduction of mono PERC, Topcon and HJT technology. These new technologies have led to improvements in solar panel efficiency, durability, and overall performance, thus, making them a more viable and cost-effective option for renewable energy production. Let us discuss each solar PV module technology and understand the differences.

PERC Solar PV Modules

In recent years, Passivated Emitter and Rear Contact (PERC) solar panels have been gaining popularity in the solar panel industry as a viable option for creating more efficient solar power. These solar panels use PERC solar cells, an improved version of conventional solar cells. Their modified design allows them to generate 6 to 12 per cent more energy than their traditional counterparts.

About PERC Technology

PERC stands for Passivated Emitter and Rear Cell. The PERC solar cell has a presence of a passivation layer at the back side of the cell, which helps to minimize recombination losses and increase light absorption. The key role of the rear-side passivation layer is to reflect light that passes through the silicon cell without being absorbed back into the silicon. By reflecting this light, the passivation layer gives the solar cell a second chance at absorbing it, resulting in significant improvement in efficiency.

Advantages of PERC Solar Panels

PERC panels offer several benefits over traditional solar panels, which make them a popular choice for solar installers and customers. Here are the key advantages:

    • Increased Energy Production: PERC solar panels have higher efficiency compared to traditional panels, resulting in increased power generation. It can add up to a 5% increase in energy production for a full PV system.
    • Increased Low-light and High-heat Performance: PERC panels perform exceptionally well in low-light and high-heat environments, providing an increased efficiency of around 3%.
    • High Area Efficiency: Because PERC panels are more efficient, they can achieve the same power output as traditional panels with fewer panels. This means a solar power system using PERC panels will need a lesser amount of space for installation.
    • Reduced BOS Costs: With PERC panels, fewer panels can achieve the same output, resulting in reduced balance of system (BOS) costs, labour costs, and other soft costs such as inverters and disconnects.

Disadvantages of PERC solar panels

    1. PERC solar panels are generally more expensive than traditional solar panels.
    2. PERC solar panels are slightly more sensitive to shading than traditional solar panels.
    3. PERC solar panels are a relatively new technology, there may be some uncertainty about their long-term durability and performance.

Applications of PERC solar panels

    1. Residential rooftops: Mono PERC solar panels are a popular choice for residential rooftops due to their high efficiency, which allows homeowners to generate more electricity from a smaller roof space.
    2. Commercial buildings: Mono PERC solar panels can also be used on commercial buildings, such as office buildings, shopping malls, and warehouses, to offset electricity costs and reduce carbon emissions.
    3. Large-scale solar power plants: Mono PERC solar panels can be used in large-scale solar power plants to generate electricity on a utility scale.

TOPCon Solar Panels

Tunnel oxide passivated contact (TOPCon) solar technology is a relatively new type of solar cell technology. TOPCON stands for “Tunnel Oxide Passivated Contact”. 

About TOPCon Technology

The TOPCon solar cell structure consists of a thin tunnel oxide layer sandwiched between a transparent conductive oxide (TCO) layer and a p-doped crystalline silicon layer. The TCO layer acts as a front contact for the solar cell, while the p-doped layer acts as the absorber layer. The tunnel oxide layer acts as a passivation layer, preventing the recombination of charge carriers at the surface of the solar cell. Increased efficiency enables the solar panel to capture a greater amount of energy per unit area.

Advantages of TOPCon Solar Panels

The adoption of TOPCon technology has gained popularity due to several benefits associated with it. Here are some of the key advantages of using TOPCon solar cell technology:

  1. Manufacturing process: TOPCon solar cells can be manufactured with the same machines as P-type solar cells, i.e. manufacturers don't need to make any high capital investment to adopt this technology, making it easier and more cost-effective to produce TOPCon solar panels on a large scale.
  2. Higher efficiency: TOPCon cells are more efficient in converting sunlight into electricity than P-type cells. The maximum efficiency of TOPCon cells is around 28%, which is higher than the maximum efficiency of about 24% for PERC cells. This higher efficiency results in more electricity generation from a given surface area.
  3. Lower degradation: TOPCon modules have a lower power degradation during the first year and over the 25 years of use, compared to PERC solar PV modules. Hence, they will maintain their efficiency for a longer time, resulting in a longer lifespan of the solar panels.
  4. Lower temperature coefficient: The temperature coefficient of TOPCon solar panels is lower than that of PERC solar panels. It means that TOPCon solar panels can maintain their efficiency at higher temperatures, which is particularly important in hot climates.
  5. Bifaciality rate: TOPCon cells have higher bifaciality than PERC cells. It means that TOPCon solar panels can generate electricity from both the front and the back of the solar panel.
  6. Low light performance: TOPCon solar modules have higher efficiency in low-light conditions than PERC modules. It means that TOPCon solar panels can generate more electricity even when there is not enough sunlight. 

    Disadvantages of TOPCon Solar PV Module Technology

    Here are some potential challenges before TOPCon solar cell technology

      1. Cost: TOPCon solar cells can be more expensive to produce than traditional solar cells due to the additional materials and manufacturing steps required to create the thin-film layers needed for the cell.
      2. Complexity: The manufacturing process for TOPCon cells is more complex than for traditional cells, which can make it more difficult to scale up production to meet high demand.
      3. High-temperature processing: The production of TOPCon cells requires high-temperature processing steps, which can lead to increased energy consumption and carbon emissions, as well as the risk of defects or damage to the cell.
      4. Sensitivity to impurities: TOPCon cells are more sensitive to impurities in the materials used to create them, which can lead to reduced efficiency or even complete failure of the cell.

    Comparison Between PERC and TOPCon Solar Technology

    When compared to a PERC solar cell, a TOPCon solar cell appears visually identical once installed in a module. However, Unlike PERC cells, TOPCon cells are made from n-doped silicon, which is more challenging to manufacture. However, this material allows TOPCon cells to achieve higher degrees of efficiency.

    Another significant difference is the more laborious passivation process used for TOPCon cells. Despite being more technically challenging, this process achieves a greater effect. Specifically, applying a layer of polycrystalline silicon to the rear side of the cell requires significant technical effort but allows the solar cell to handle higher voltages, resulting in an increase in overall efficiency.

    Applications of TOPCon Solar Panels

      1. Utility-scale solar power plants: TOPCon solar panels are often used in utility-scale solar power plants due to their high efficiency, which allows for more electricity to be generated from a smaller area.
      2. Agriculture and farming: TOPCon solar panels can be used for agricultural applications such as water pumping, irrigation, and crop drying, providing off-grid electricity to remote areas.
      3. Electric vehicle charging stations: TOPCon solar panels can be used to power electric vehicle charging stations, allowing for clean and sustainable transportation.

    HJT Solar PV Module 

    Heterojunction (HJT) solar cell technology is a relatively new type of solar cell that has been gaining popularity in recent years. The design and structure of HJT allow for a more efficient conversion of sunlight into electricity.

    About HJT Solar Panel Technology

    Heterojunction solar panels are a type of photovoltaic panel that consists of three layers of photovoltaic material. These panels incorporate two distinct technologies: crystalline silicon and amorphous "thin-film" silicon, which work in harmony to produce electricity.

    HJT cells consist of three main materials: Crystalline Silicon (c-Si), Amorphous Silicon (a-Si) and Indium Tin Oxide (ITO)

    The first layer, made of amorphous silicon, captures sunlight before it reaches the crystalline layer, as well as any light that reflects off the underlying layers. The middle layer is composed of monocrystalline silicon, which is primarily responsible for converting most of the sunlight into electricity. The final layer is another amorphous thin-film silicon layer, located behind the crystalline silicon, which captures any remaining photons that have passed through the first two layers.

    By combining these two technologies, heterojunction solar panels can generate more energy than either technology could produce independently. These panels can achieve efficiencies of 25% or higher, making them an attractive choice for solar energy generation.

    Advantages of HJT Solar Panels

    Here are the major benefits of Heterojunction (HJT) solar panels summarized into short points:

      1. High Efficiency: HJT solar panels have a conversion efficiency of 26.07% for monofacial modules and over 30% for bifacial, making it one of the most efficient solar technologies in the industry.
      2. Good Temperature Coefficient: HJT cells are less affected by changes in temperature, making them great for use in high-temperature locations.
      3. High Bifaciality: HJT cells have a high bi-faciality factor of 92%, making them a great choice for utility-scale applications that can take advantage of the albedo resource.
      4. Easy Manufacturing Process: The HJT solar PV module manufacturing process only involves 5-7 steps, and the cost of equipment is constantly being reduced, making it a cost-effective and promising technology for the future of solar energy.

    Disadvantages of HJT Solar Panels

    Heterojunction (HJT) solar panels offer several advantages, but they also have some drawbacks. Here are the main disadvantages of HJT solar panels:

      1. High Cost: HJT panels are more expensive due to the additional steps in manufacturing and costly materials.
      2. Fragility: HJT panels are thin and have a complex structure, making them more vulnerable to damage.
      3. Sensitivity to Humidity: HJT panels are sensitive to moisture, which can reduce their efficiency or damage the panel.
      4. Complexity of Production: The manufacturing process for HJT panels requires specialized knowledge and equipment.
      5. Low Manufacturing Scale: HJT panels are produced at a lower scale than traditional panels, which can make them more expensive and harder to find.
      6. New Technology: HJT panels are a relatively new technology, and experience with installation and maintenance may be limited.

    Comparison Between HJT and TOPCon Solar PV Module Technology

    TOPCon and HJT solar panels are two advanced solar technologies that offer high efficiency and reliability. Here are some general features where two solar panels can differ:

    1. HJT panels have higher efficiency and bi-faciality, but are more complex and expensive to manufacture, and are sensitive to humidity.
    2. TOPCon panels have a simpler manufacturing process, lower cost, and are less sensitive to humidity, but have lower efficiency and bi-faciality compared to HJT panels.

    Applications of HJT Solar Panels

    1. Building-integrated photovoltaics (BIPV): HJT solar panels can be integrated into building facades, roofs, and windows to generate electricity while also providing architectural design and energy-saving benefits.
    2. Space-constrained applications: HJT solar panels are a good choice for space-constrained applications such as portable solar chargers, off-grid cabins, and small boats, due to their high efficiency and compact size.
    3. Utility-scale solar power plants: HJT solar panels can be used in large utility-scale solar power plants, especially for projects with higher solar irradiance, which increases the efficiency of the HJT panels.


    In summary, HJT panels offer the highest efficiency and bi-faciality, but are the most complex and expensive to manufacture and are sensitive to humidity. TOPCon solar panels have a simpler manufacturing process and are less sensitive to humidity, but have lower efficiency and bifaciality compared to HJT panels. Mono PERC panels have a simpler manufacturing process than both HJT and TOPCon panels but have lower efficiency and bifaciality compared to HJT panels.

    In India, PERC (Passivated Emitter and Rear Cell) technology is widely used and is considered a good choice for most applications. Moreover, Mono PERC solar panels are known for their reliability, durability, and longevity. Topcon panels are relatively expensive and may not be cost-effective for all applications. Both TOPCon & HJT solar panels are also relatively expensive and  Both TOPCon & HJT may not be widely available in India.

    We can conclude Mono PERC panels are a good choice for most solar applications in India, but the suitability of a particular technology ultimately depends on a variety of factors. It is best to consult with a reputable solar energy company to determine the most appropriate technology for your specific needs and budget.


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