HJT technology differs from other technologies, such as TOPCon, in its cell topology and certain electrical and structural characteristics. Among the many advantages of HJT technology over TOPCon, the energy yield stands out, which can be up to 6% higher in some regions with high irradiance and high temperatures. This means that, for each kWp installed in a project, HJT delivers up to 6% more generated energy (kWh).
HJT cells feature hydrogenated amorphous silicon layers deposited on the front and back surfaces of the cell, which act as passivation layers, enabling these cells to achieve higher efficiencies and better performance under low irradiance. Risen Energy's HJT cells achieved 26,61% efficiency, enabling the company to mass-produce modules with up to 740 Wp.
Furthermore, the surface of the HJT cell is coated with a transparent conductive oxide (TCO) film and has no insulating layer. Therefore, there is no possibility of the surface layer being charged, which prevents PID from occurring.
This layer, which uses ITO (indium-tin oxide) material, in addition to mitigating PID losses in these cells, makes them HJT cells preferred for the construction of Tandem cells, due to the ease of connection with perovskite cells, precisely because it is conductive.
HJT cells cannot be produced on the same production lines as TOPCon cells, requiring high investments in new production lines by manufacturers, since it is not possible to take advantage of pre-existing lines of PERC or TOPCon technologies.
For this reason, few manufacturers have the production capacity for this technology, with an estimated global production capacity of 120 GW in 2025, compared to more than 1000 GW of global production capacity for TOPCon technology.
Furthermore, HJT modules require different and specific manufacturing processes due to their single-cell topology, as they are highly sensitive to exposure to high temperatures, as in conventional half-cell cutting, mesh printing and interconnection processes between cells, which results in aesthetic differences in the modules and cells.
In this way, it is possible to differentiate an HJT module from a TOPCon module by evaluating its electrical characteristics and visual aspects.
Electrical parameters: evaluation of technical data sheets
HJT modules perform better under real operating conditions, as their Pmax temperature coefficient is lower than that of TOPCon modules, being only -0,24%/ºC.
Furthermore, power degradation over 30 years is only 0,30% per year, allowing HJT modules to reach 30 years with 90,3% of their nominal power. Their bifaciality is 90%. These differences directly impact the modules' energy yield.
Finally, the open circuit voltages (Voc) of HJT modules are higher when compared to TOPCon modules of the same power.
Visual aspects
Module Back Color
The symmetrical structure of HJT cells, combined with the ITO film deposition process, in which all cells are positioned horizontally, results in homogeneous and uniform coloration between the back and front surfaces. Thus, the color on both surfaces is virtually identical, and all cells have the same hue.
In the case of TOPCon modules, the cells' blue coloration is a result of the passivation film called SiNx (silicon nitride). Different thicknesses of this film result in color variations, ranging from light blue to dark blue. Typically, the front surface ranges from blue to black, while the back surface displays lighter, unevenly colored shades of blue.
The high reflectivity of the tunneling oxide layer and the polysilicon layer on the back of TOPCon, combined with the deposition process in which the cells are positioned vertically, back to back, inside a quartz tube, makes it difficult to control the film thickness on both sides. This results in color inconsistency between the front and back of the module, as well as a lack of uniformity between cells.
Therefore, the difference in coloration of the back and front faces, as well as the lack of color uniformity between cells, is a striking feature of TOPCon modules.
Chamfered cell corners
HJT technology requires low-temperature production processes, reaching maximum temperatures of 200°C, while in TOPCon production temperatures of up to 800°C are observed.
To avoid cell damage and ensure high-quality HJT cells, leading manufacturers and HJT technology leaders, such as Risen, perform half-cell slicing directly on the ingot before wafer slicing, avoiding cell slicing under high temperatures. This results in wafers already in the half-cell format, with all four corners chamfered, resulting in HJT cells with all corners chamfered, as shown in Figure 2.
In the case of TOPCon modules, the industry mostly uses whole wafers to manufacture the cells, which are only split in half after completion, just before module assembly. For this reason, TOPCon half-cells have only two chamfered corners and two straight corners, as can also be seen in Figure 2.
HJT (right) with 4 chamfered corners
Conclusion
HJT technology stands out for its high energy efficiency, excellent thermal stability, low power degradation over years of operation, and high bifaciality — characteristics that result in superior energy performance.
Risen has developed an innovative cell interconnection technology, called Hyperlink, which operates at low temperatures and without the application of stress. thermal. Furthermore, it uses ultra-thin OBB cells, only 90 μm thick, which are screen-printed with a stencil screen to form the conductive mesh with greater precision.
Advances in HJT cell and module manufacturing processes ensure high reliability by preventing thermal and mechanical damage to the cells, in addition to providing a different aesthetic appearance compared to TOPCon cells and HJT cells from other manufacturers — such as, for example, color uniformity and the absence of visible solder points on the conductors.
In an increasingly competitive market where manufacturers seek to optimize costs, understanding HJT technology, its electrical characteristics, and manufacturing processes is important to ensure that the modules purchased offer high reliability and excellent performance.
Furthermore, the technical and visual differences between HJT and TOPCon technologies are essential for integrators, distributors, and investors to make decisions about which technology to use in their projects and what results to expect.
The opinions and information expressed are the sole responsibility of the author and do not necessarily represent the official position of the author. Canal Solar.
