LONGi Solar highlighted its latest Hi-MO X10 series HPBC 2.0 back-contact cell technology based module's advanced features for full-lifecycle reliability
This module, featuring a back-contact cell structure, offers innovative soft breakdown technology to mitigate potential risk of hotspot formation
The advanced front-side uniform passivation and rear-side bipolar hybrid passivation reduces the risk of UVID and high current loss
The latest high-efficiency n-type cell technology-based PV modules, designed to provide guaranteed power output for up to 30 years, must withstand various environmental and mechanical stresses throughout their lifecycle. This challenge is particularly critical for distributed generation (DG) application modules, which face a higher likelihood of hotspot formation and other environmental stress factors. Mitigating these potential degradation issues begins at the design stage, with a focus on wafer selection, cell technology structure, and high-quality encapsulation.
At the TaiyangNews Reliable PV Module Design Conference 2024, Dante Zeng, Product Marketing Manager at LONGi Solar – one of China's leading PV module manufacturers – introduced the recently launched Hi-MO X10 series back-contact modules designed for DG applications (see LONGi's presentation here). These modules, equipped with HPBC 2.0 back-contact cell technology, offer up to 24.8% efficiency and 670 W power output, emphasizing full-lifecycle reliability.
Mr. Zeng began by explaining the correlation between common degradation modes and environmental stress factors, such as hotspot formation from shading, potential-induced degradation (PID) from damp heat (DH), thermal cycling (TC) effects, ultra-violet-induced degradation (UVID), and mechanical breakage. He noted that shading – a common issue in DG applications caused by dust, bird droppings, shadows, or cell defects – can lead to localized hotspots, resulting in high temperatures that damage modules and reduce efficiency. In severe cases, these hotspots can cause fire hazards and the potential burndown of installed plants.
Moisture-rich environments exacerbate PID, which is driven by vapor ingress and negative bias voltage across module frames and cells, leading to electrical failure, efficiency losses, and encapsulation defects. UVID, caused by prolonged exposure to high irradiance and temperatures, destabilizes the cell structure, while mechanical stresses such as impacts during transport, installation, and operation – as well as hail and wind – can lead to breakages and hidden microcracks, further compromising performance.
According to LONGi Solar, addressing these reliability challenges must begin at the module design phase. Mr. Zeng emphasized the importance of selecting advanced technologies like HPBC 2.0 cell architecture, superior wafer materials, and high-quality encapsulation, all of which are crucial for ensuring the Hi-MO X10 module’s long-term reliability.
The Hi-MO X10 module, featuring HPBC 2.0 back-contact cell technology with positive and negative contacts on the backside, incorporates advanced soft breakdown technology to mitigate hotspot risks. This innovation leverages the internal diode characteristics of each cell and the unique back-contact cell structure to bypass individual cells rather than an entire substring under shading conditions. According to LONGi Solar, this approach reduces power losses by over 70% in cases of single-cell shading compared to conventional TOPCon modules.
Additionally, the soft breakdown feature effectively prevents fire hazards caused by localized overheating by allowing blocked current to bypass the shaded area. It also reduces localized temperatures by more than 28% compared to conventional cells, resulting in a significantly lower maximum hotspot temperature of under 110°C compared to the standard 170°C. This enhancement ensures improved module reliability.
LONGi Solar has also incorporated an anti-dust frame design to further enhance module performance. By eliminating shorter-length frames, the uniform height of the frame and glass minimizes dust sedimentation, reducing maintenance needs and preserving efficiency.
After addressing hotspot risks, LONGi Solar highlighted the Hi-MO X10 module’s advanced HPBC 2.0 cell technology, which is designed to withstand potential degradation modes such as PID and UVID.
The HPBC 2.0 cell features advanced front-side passivation with more than 2% uniformity compared to conventional TOPCon cells, which rely on high-temperature boron diffusion without advanced passivation. This improvement significantly enhances the module’s resistance to UVID. On the rear side, the back-contact cell structure employs uniform bipolar hybrid passivation, reducing current losses at both positive and negative electrodes and boosting open-circuit voltage (Voc) by over 15 mV, outperforming the unipolar rear-side passivation of TOPCon cells.
In addition to cell technology, LONGi Solar emphasized the importance of high-quality packaging materials. The use of a high-density POE-type encapsulant, which resists acetic acid formation, effectively reduces moisture ingress into the module lamination. The adoption of aluminum-free pure silver paste for both positive and negative electrodes further mitigates corrosion risks. Moreover, the module operates at a temperature 0.5°C lower than conventional designs, improving the long-term aging rate of module materials and films.
LONGi Solar has validated these reliability-enhancing features through in-house extended reliability tests, including damp heat (DH3000), UV (UV180), and thermal cycling (TC800), demonstrating the durability and performance of the Hi-MO X10 module under extreme conditions.
LONGi claims the Hi-MO X10 series module effectively addresses the risks of hidden cell cracks and mechanical breakage by incorporating its TaiRay wafer, which offers up to 16% higher maximum rupture strength compared to industry peers. According to LONGi Solar, the module’s full back-contact online soldering structure, combined with the TaiRay wafer’s thickness of up to 10 µm greater than standard wafers, significantly enhances resistance to cell cracking by reducing stress on cell edges.
Additionally, the integration of busbarless (0BB) metallization improves impact resistance by dispersing external mechanical forces through the sub-grids instead of relying on traditional busbars. This design ensures more uniform stress distribution and superior durability compared to conventional super multi-busbar cells.
Several additional factors contribute to the Hi-MO X10 module’s full-lifecycle reliability. These include LONGi Solar’s robust financial stability, a globally integrated R&D and service team, stringent incoming raw material quality control (IQC), and quarterly enhanced reliability testing protocols.