A Comprehensive Comparison: TOPCon, HJT, and PERC Solar Panels

In recent years, the solar panel market has made significant progress, with various technologies emerging to enhance the efficiency and performance of solar panels. Among these, TOPCon, HJT, and PERC solar panels stand out. This article will provide a detailed comparison of these three types of solar panels, helping you better understand their advantages and disadvantages to make informed decisions.

An Overview of TOPCon, HJT, and PERC Solar Panel Technologies

PERC (Passivated Emitter and Rear Cell): PERC technology, introduced in the 1980s, involves adding a dielectric passivation layer to the rear of traditional solar cells. This layer reflects unused light back into the cell and reduces electron-hole recombination, thereby improving efficiency and energy output by approximately 6-12% compared to conventional solar cells.

TOPCon (Tunnel Oxide Passivated Contact): Building on PERC technology, TOPCon solar cells feature an ultra-thin tunnel oxide layer and a doped polycrystalline silicon layer on the rear side of the silicon wafer. This structure not only provides excellent interface passivation but also acts as a selective carrier transport channel. The majority carriers (electrons) can pass through while the minority carriers (holes) are prevented from recombining, significantly increasing the cell’s open-circuit voltage and fill factor. The theoretical maximum efficiency of TOPCon cells is as high as 28.7%, surpassing the 24.5% of traditional P-type PERC cells.

HJT (Heterojunction Technology): HJT solar cells combine crystalline silicon (c-Si) with amorphous silicon (a-Si) thin-film layers to create a hybrid cell structure. The a-Si material not only passivates the surface but also offers a higher absorption coefficient in specific parts of the light spectrum, complementing the absorption capability of c-Si material. Due to their flexibility in architecture, HJT panels are generally designed as bifacial modules to further increase energy yield.

Efficiency Comparison

PERC Solar Panels: The efficiency of PERC solar cells typically ranges from 19% to 22%. With the continuous optimization of manufacturing processes and improvements in materials, the efficiency of PERC cells has been steadily increasing. However, compared to TOPCon and HJT cells, their efficiency ceiling is relatively lower.

TOPCon Solar Panels: The efficiency of TOPCon solar cells is higher than that of PERC cells. Real-world testing data shows that TOPCon modules can achieve efficiencies exceeding 25% in mass production. Some advanced TOPCon cells have demonstrated efficiencies of up to 26.1%. The higher efficiency allows solar arrays to generate more electricity while using less roof or ground space.

HJT Solar Panels: HJT solar cells are renowned for their high efficiency. Their efficiency typically ranges from 23% to 25%, with some advanced HJT cells achieving even higher efficiencies. For instance, Longi Green Energy’s HJT solar cells have reached an efficiency of 26.52% in laboratory settings. The HJT structure helps reduce carrier recombination losses, thereby improving conversion efficiency.

Temperature Performance Comparison

PERC Solar Panels: PERC solar cells exhibit a certain degree of efficiency loss at high temperatures. Generally, when operating above 25°C (77°F), their output can degrade by 3-5% or more. However, the rear passivation layer in PERC cells reflects more infrared light, which helps mitigate efficiency losses to some extent.

TOPCon Solar Panels: TOPCon solar cells demonstrate superior performance in hot weather conditions compared to PERC cells. Their unique cell structure allows them to maintain higher efficiencies at elevated temperatures. Studies have shown that TOPCon panels degrade less at higher temperatures compared to PERC panels. This makes TOPCon a better choice for installations in regions with extended periods of high temperatures.

HJT Solar Panels: HJT solar cells have a very low temperature coefficient, meaning they are less affected by temperature changes and can maintain stable power generation performance in high-temperature environments. This helps reduce the risk of power loss due to temperature rises and ensures more consistent energy.

Bifaciality Comparison

PERC Solar Panels: Conventional PERC solar panels typically have a bifaciality factor of around 70%, meaning they can generate a certain amount of electricity from the rear side. However, their bifacial generation capability is relatively limited compared to TOPCon and HJT panels.

TOPCon Solar Panels: TOPCon solar panels feature a high bifaciality factor, usually between 80% and 85%. Their advanced passivation structure enables them to more efficiently capture and convert light that hits both the front and back surfaces. This allows them to generate more electricity from reflected light, further enhancing their overall energy output.

HJT Solar Panels: HJT solar panels are inherently bifacial in design. Due to the symmetry of their structure and the high-transparency characteristics of the TCO layer, they can effectively utilize light from both sides. Their bifaciality factor typically ranges from 85% to 95%, enabling them to generate more electricity in applications where there is ample reflected light, such as over water or on light-colored ground surfaces.

Manufacturing Process and Cost Comparison

PERC Solar Panels: The production process for PERC solar cells is relatively mature and less complex, resulting in relatively low manufacturing costs. It requires only a few additional process steps compared to traditional solar cells, such as depositing the rear passivation layer and making laser contacts. This makes PERC panels more affordable and suitable for large-scale applications.

TOPCon Solar Panels: The manufacturing process of TOPCon solar cells is more complex than that of PERC cells. It involves additional steps such as forming the tunnel oxide layer and depositing the doped polycrystalline silicon layer. These additional processes and the use of advanced materials lead to higher production costs for TOPCon cells, which are approximately 10-15% higher than those of PERC cells. However, as the technology continues to develop and the production scale expands, the manufacturing costs of TOPCon panels are gradually decreasing.

HJT Solar Panels: The manufacturing process for HJT solar cells is highly complex. It requires the integration of crystalline silicon and amorphous silicon thin-film technologies, as well as the use of advanced equipment and processes. This results in relatively high equipment investment and production costs. Currently, the manufacturing costs of HJT panels are higher than those of TOPCon and PERC panels. However, the continuous improvement in mass production processes and the reduction in thin-film equipment costs may make HJT panels more economically viable in the future.

Stability and Durability Comparison

PERC Solar Panels: PERC solar panels have been extensively tested and proven in the market. They exhibit good stability and durability under various environmental conditions. However, due to the use of boron-doped P-type silicon wafers, PERC panels may experience light-induced degradation (LID) to some extent. Nevertheless, this issue is being continually mitigated through improvements in materials and processes.

TOPCon Solar Panels: TOPCon solar panels use N-type silicon wafers, which have a lower light-induced degradation rate than P-type silicon wafers. This means that TOPCon modules can maintain a higher initial performance in actual use, with reduced performance loss over the long term. Additionally, the tunnel oxide layer and doped polycrystalline silicon layer in TOPCon cells provide excellent passivation protection, enhancing the panels’ resistance to light and heat degradation. As a result, TOPCon panels typically offer longer warranties, often up to 30 years, ensuring long-term stable power generation.

HJT Solar Panels: HJT solar panels also use N-type silicon wafers, which inherently offer better stability and anti-degradation performance. The amorphous silicon thin film in HJT cells provides excellent passivation and protection for the crystalline silicon substrate, effectively reducing the impact of light, heat, and humidity on the cells. HJT panels exhibit excellent stability and durability under harsh environmental conditions and generally come with long-term warranties similar to TOPCon panels, providing reliable assurance for long-term power generation.

Application Scenarios Comparison

PERC Solar Panels: Due to their relatively low cost and good performance, PERC solar panels are widely used in various scenarios, including residential rooftops, commercial buildings, and utility-scale solar power plants. They are particularly suitable for projects where cost control is a priority and the installation environment is relatively mild.

TOPCon Solar Panels: TOPCon solar panels are ideal for applications where high efficiency and excellent performance in hot climates are required. Their high efficiency enables more power generation within limited space, making them suitable for residential installations with limited roof space or commercial projects aiming to maximize energy output. Additionally, their superior temperature performance makes them an excellent choice for regions with high temperatures.

HJT Solar Panels: HJT solar panels are well-suited for complex environments, such as high-temperature and high-humidity areas or regions with significant temperature fluctuations. Their high bifaciality and excellent temperature performance allow them to generate more electricity in scenarios with ample reflected light or in hot climates. Furthermore, HJT panels are a good option for high-end photovoltaic applications due to their high efficiency and stability, such as in distributed photovoltaic projects on building rooftops or near water bodies.