Key takeaways:
JA Solar’s Djamel Mansour outlined how new TOPCon module designs combine cell-level and module-level changes, such as multi-cut cells and rear-side polyfingers
Dividing cells into 3 or 4 slices reduces resistive losses, while overlapping cell layouts increase active area and improve module output
Structural changes, including laminate design adjustments, modified junction box openings, and drainage features, target improved reliability and field performance
PV manufacturers always find ways to optimize the technology, pushing the limits to squeeze out every last drop. For example, even though TOPCon is currently the mainstream technology, there are still developments at the cell and module levels, such as using rear-side polyfingers and multi-cut cell cells. JA Solar has incorporated these developments in its latest TOPCon module, branded DeepBlue 5.0.
At the TaiyangNews High-Efficiency Solar Technologies Conference 2025, Djamel Mansour from JA Solar discussed the cell- and module-level developments in the DeepBlue 5.0 module. The presentation focused on how these design changes in n-type TOPCon modules aim to improve efficiency, reliability, and overall system value.
The new module can reach a maximum power output of 670 W with module efficiency approaching 24.8%, according to Mansour. Bifaciality has also increased to around 85%, while the temperature coefficient of power is about -0.26%/°C and the annual degradation rate is approximately 0.35%. These improvements result from several design changes, including more uniform wafers with higher resistivity, improvements in passivating contacts, and rear-side polyfinger designs that enhance bifacial performance.
A central design change discussed in the presentation is the shift from conventional half-cut cells to multi-cut cell technology. Instead of splitting cells into 2 halves, cells are cut into 3 or 4 smaller pieces. This approach reduces current in each segment and, therefore, lowers resistive losses. However, increasing the number of cuts also introduces manufacturing challenges such as additional cutting losses and more complex edge passivation. According to Mansour, an optimal balance appears to exist with 3 or 4 slices per cell, in which total power losses from resistance, cutting, and manufacturing yield are minimized.
Another structural change involves how the cells are interconnected within the module. Traditional designs leave gaps of roughly 1.5-2 mm between cells. More recent designs reduced the gap to about 0.7 mm, especially after the adoption of rectangular wafers such as M10R and G12R. The newer design introduces overlapping interconnections that effectively create a ‘negative gap’ between cells. By eliminating inactive spacing and creating a nearly full-screen cell layout, more of the module area is used for power generation. This approach increases the active cell area and improves module output without changing the overall module dimensions. In practice, this layout with multi-cut cells contributes to roughly 15 W additional power and improves module efficiency by about 0.56%, according to JA Solar.
Beyond power improvements, the presentation also focused on reliability. One feature introduced is a composite structure enhancement (CSE) design in the module laminate. In conventional modules, the encapsulant thickness can vary between the center and edges, which may make the edges more vulnerable to moisture ingress in glass-glass modules. The additional encapsulant layer used in this design helps equalize thickness across the module and improves resistance to environmental stress, particularly in damp heat conditions.
Mechanical reliability was also addressed by modifying the rear glass opening for junction box installation. Traditional layouts use a centralized arrangement of the openings, which can concentrate the mechanical stress. The results presented showed that the updated design, with a triangular dispersed layout that spreads the opening further apart, reduces stress concentration and improves resistance to glass breakage under mechanical loads.
Mansour also discussed the module’s shading behavior. With an optimized circuit layout, partial shading at the bottom of the module affects a smaller portion of the electrical circuit compared to traditional designs. In the example presented, the optimized design produced about 34% higher power output under certain shading conditions compared with a conventional layout under shading.
The presentation also introduced a simple mechanical design intended to reduce dust accumulation. Small drainage openings in the lower frame allow water and dust to pass through more easily. This reduces the buildup of dirt along the lower edge of modules, which can otherwise block light and lower performance. Field observations suggested this design could provide small but measurable gains in output, typically around 0.2-1%, depending on installation conditions.
Finally, the impact of these design changes was illustrated through simulations and early field comparisons. Combining higher module power, improved bifaciality, better temperature behavior, and lower degradation results in higher lifetime energy yield. System-level simulations indicated gains in first-year energy production along with reductions in balance-of-system costs and LCOE.
