JA Solar’s DeepBlue 5.0 module series reaches 24.1% efficiency – a first for a commercial TOPCon module to surpass the 24% threshold
Transitioning from half-cut to 1/3-cut cells reduces series resistance losses, delivering about 7 to 8 W higher output compared with conventional designs
JA Solar’s Gapless Flexible Interconnection and Full Screen layout increase cell coverage and active module area, adding roughly 7 to 8 W of additional power
Optimized circuit design boosts power output under shading conditions by up to 34%, while structural enhancements reduce mechanical stress and improve long-term durability
Innovations in photovoltaics are increasingly integrated; they can no longer be clearly bifurcated into cell- and module-level. This trend becomes clear when one looks at recent developments in TOPCon technology. Some of the latest process innovations, e.g., rear-side polyfingers and edge passivation, are implemented at the cell level but deliver much of their value at the module level.
Polyfingers, for example, contribute modest efficiency gains in the cell, but its impact in improving module bifaciality is quite significant. Similarly, effective edge passivation enables multi-cut cell architectures that can raise module power classes.
These innovations form the technological basis for JA Solar’s latest DeepBlue 5.0 series. This product platform also incorporates a few more configurational innovations. Importantly, these features are not merely technological concepts for the company, as the new module series is already set to ship in high volumes. With a rated power of 650 W and module efficiency of 24.1%, the product series is one among the first TOPCon modules to surpass the 24% threshold in the commercial arena. Meanwhile, the company also has a technology roadmap to raise the power of the DeepBlue 5.0 series further to 670 W with the efficiency 24.8% in this year.
With this as the backdrop, TaiyangNews had the opportunity to speak with JA Solar’s CTO, Zi Ouyang, about the key technical advancements associated with DeepBlue 5.0 that enabled this achievement. Emphasizing the importance of efficiency improvements amid current overcapacity, Ouyang said modules account for only about 17% of the total system cost, according to third-party data, with this figure expected to decline further in the coming years. On the other hand, module-level improvements play a critical role in pushing overall system performance and are an effective way to reduce the levelized cost of energy (LCOE). This allows developers to invest more in high-efficiency products.
The advances behind DeepBlue 5.0 are not based on a single disruptive invention but rather on a systematic effort to translate technological possibilities into scalable product solutions. “There are not many secrets down there,” Ouyang remarked, explaining that the key lies in realizing incremental efficiency improvements at the cell level while simultaneously optimizing the cell-to-module (CTM) ratio and maximizing the effective module area.
From a product perspective, DeepBlue 5.0 features both polyfinger and edge passivation technologies implemented at the cell level, with the latest module-level design features including multi-cut cells, gapless flexible interconnection (GFI), and a full-screen (FS) layout. Together, these innovations contribute roughly 20-25 W of additional module power, enabling the series to reach 650 W output levels and 24.1% efficiency, which Ouyang describes as “just the beginning.”
Starting at the cell level, the DeepBlue 5.0 series uses TOPCon cells based on rear polyfingers. That means the crux of the TOPCon structure – the silicon oxide and doped polysilicon stack – is limited to the area where the cell fingers are applied in the metallization. This improves the overall performance and results in a 3 W power gain at the module level. This approach also reduces parasitic absorption of sunlight in the polysilicon layers, thereby enhancing bifaciality. At 85%, the DeepBlue 5.0 series offers 5% additional bifaciality.
The most significant change is the transition from conventional half-cut cells to multi-cut (or 1/3-cut) cells. Cutting cells into smaller segments reduces the current per cell, thereby reducing series-resistance losses while increasing the operating voltage of the module string. According to JA Solar’s production testing, this configuration alone delivers an output 7-8 W higher than that of traditional half-cut modules.
Historically, multi-cut architectures faced challenges related to edge recombination caused by cell cutting. Ouyang noted that recent breakthroughs in edge passivation processes and manufacturing equipment, achieved over the past year, have finally resolved this limitation, making multi-cut designs viable for large-scale production.
The second innovation is JA Solar’s GFI technology. In this design, cells slightly overlap rather than leaving visible gaps between them. A thin film layer is inserted at the overlap region to provide cushioning. Beyond its distinctive all-black aesthetic, the gapless configuration increases the module’s effective cell coverage, improving the aspect ratio and contributing additional power output.
Complementing this is the FS design, which eliminates visible ribbon connections along the module edges. Similar to the narrow bezel designs seen in modern smartphones, the FS layout increases the module’s active area by reducing inactive margins. For a module measuring 2,382 × 1,134 mm, the combined effect of GFI and FS increases the active surface area by ~1.82%, resulting in an additional 7-8 W gain.
The circuit architecture of DeepBlue 5.0 also differs from conventional half-cell layouts. Instead of 2 symmetrical substrings, the module uses a 66-cell-based 3-substring configuration. This design eliminates the traditional central junction box and redistributes electrical connections across the module – 1 towards the bottom and 2 at the top end. This new configuration reduces mechanical stress on the rear glass, particularly important for tracker-mounted systems, by eliminating stress hotspots associated with drilled junction box openings. According to Ouyang, this design reduces mechanical stress on the back glass by 14-16%, depending on mounting conditions.
Further structural enhancements come from JA Solar’s Combined Structure Enhancement (CSE) approach, which uses a specialized encapsulant structure to improve thickness uniformity and edge sealing. This thickness uniformity helps distribute mechanical loads more evenly across the modules and eliminates the stress hot spots.
The module series also helps improve operational performance. The module’s optimized circuit design enhances performance under partial shading conditions. In common edge-shading scenarios, DeepBlue 5.0 modules can deliver up to 34% higher power output vis-à-vis conventional half-cell designs. The reason is that during shading from the front rows, the lower end represents only 1/3rd of the module with the 3-cut cell layout, rather than half, so only 1/3rd of the module will be inactive. The additional 5% bifaciality from adopting polyfingers also contributes to operational gains. Another important improvement in this area lowered the temperature coefficient by 0.03%, to 0.26%/°C. This, according to Ouyang, results in a power gain of nearly 1% compared to the previous DeepBlue 4.0 Pro series. Additional design elements relating to operational improvements include an anti-dust-accumulation structure with drain holes at the bottom.
Taken together, polyfinger metallization, advanced edge passivation, multi-cut architecture, and high-density module packaging result in a 20-25 W increase in power compared with the previous generation, enabling DeepBlue 5.0 to reach 650 W output and 24.1% efficiency in mass production. JA Solar kick-started the commercialization by shipping its DeepBlue 5.0 module series. It will also be featured in the TaiyangNews TOP SOLAR MODULES listing once it meets the qualification criterion for commercial modules. At the same time, the technology has already reached 670 W on pilot lines, according to Ouyang, indicating further headroom.