With the new back contact module Hi-MO X10, LONGi has hit the pinnacle of crystalline silicon

LONGi has unveiled the second generation of its Hybrid Passivated Back Contact (HPBC) technology, HPBC 2.0, establishing a new standard in solar innovation. Building on the success of its first generation back contact module, the Hi-MO 6, introduced in 2022, LONGi has invested over €260 million (¥2 billion RMB) in research and development and yielded nearly 200 patents to launch this next generation back contact upgrade, underscoring its commitment to advancing photovoltaic technology and driving the next stage of solar energy evolution.

Major breakthroughs in three areas

There are three innovative breakthroughs for HPBC cells in the areas of cell substrate, passivation technology and process technology. The result is a mass production cell efficiency of 26.6% - a 1% leap over the first generation and a true milestone. This will be the last time that crystalline silicon cell technology achieves a 1% jump in absolute efficiency which is why this evolution of back contact technology and the introduction of HPBC 2.0 is seen as the pinnacle of crystalline silicon.

The Hi-MO X10 now delivers a module efficiency of 24.8%, resulting in a 5% increase in power per unit area compared to the TOPCon. This makes it at least 30W more powerful than a TOPCon of the same size.

New TaiRay wafer is key to boosting efficiency

The wafer substrate is a major innovation in the X10. LONGi released the TaiRay wafer in March 2024. Not only do they show a 0.1% increase in efficiency per cell, they also have improved mechanical properties. Their tested bending is 16% higher than that of conventional wafers. As a result, they provide higher break resistance with a lower probability of cell breakage during production. In addition, the underlying TaiRay production process reduces the amount of oxygen and other impurities. Single crystal growth defects are all reduced, resulting in improved efficiency. The more impurities that can be removed, the greater the potential for improved cell efficiency.

The bending strength of the TaiRay wafer was of particular interest to the customer when we showed them the features of the new M11 rectangular wafer, as the wafer substrate itself is an important element in the design and production of a long-term reliable module.

Last but not least, the TaiRay wafer is stacked with single-line flat welding tape technology, which reduces the risk of hidden cracks by approximately 87 percent.

LONGi implemented the Zero Busbar structure (0BB) in back contact technology for the first time

The so-called 0BB (zero busbar) has also been implemented in the rear contact technology and in the Hi-MO X10 for the first time. Zero busbar technology is being explored and implemented in high-efficiency and premium solar modules, particularly where performance and aesthetics are critical. In crystalline silicon solar cells, busbars are metal conductors used to collect electricity, typically with multiple busbars. Zero-busbar technology eliminates these main bus bars. This design maximizes energy production in varying weather conditions by allowing more sunlight to reach the cell area, increasing efficiency even on cloudy days. Overall, the module delivers higher yields and lower LCOE, making it a valuable long-term investment. The result is a significant improvement in efficiency and a 5W increase in module power.

Addressing the increasing demand for more safety and anti-shading technology

The back contact module incorporates a new shading optimizer that reduces power loss by 70% compared to TOPCon, while using a bypass diode effect to avoid hot spots due to localized overheating when shaded. LONGi calls the overall design used here “Soft Breakdown Design”. This can better ensure the safety and reliability of the product, while bringing high power generation benefits to customers.

This safety feature is a milestone in enabling modules to operate safely, long-term and stable as solar installations are prone to hotspot fires. The soft breakdown design is able to reduce the localized temperature under shading by 28% compared to conventional cells.

At the same time, the operating temperature of the module is lower. Encapsulation technologies make them more resistant to UV light, humidity, heat, and thermal cycling.

Multiple layers enhance the module’s performance

Let’s look at the changes of the layers involved in HPBC 2.0 to enhance solar module efficiency and reliability. In the Hi-MO X10, we have a multi-layer structure designed for optimal performance:

• Light absorption layer: Featuring a multi-layer anti-reflection film, this layer improves short-circuit current by 2.25%. The additionally improved uniformity of the micro texture reduces the reflection of short-wave light by 12%. Therefore, more sunlight is effectively captured.
• Photovoltaic conversion layer: Leveraging Bipolar Hybrid Passivation Technology, this layer increases open-circuit voltage by 15mV to 745mV.
• Uniform passivation: The implemented uniform passivation significantly reduces UV-induced degradation and boosts long-term efficiency.
• Electric transmission layer: With the Bipolar Low Resistance Passivation Contacts and the inclusion of the shading optimizer technology, this layer is responsible for the mentioned reduced shading power losses.

Aesthetics matter in solar technology and the X10 is in no way inferior

In many parts of Europe, aesthetics play an important role in solar installations. Customers prioritize aesthetics in solar installations primarily due to cultural, architectural and social preferences. As visible elements on rooftops or facades, solar panels are expected to blend seamlessly with existing designs to maintain overall aesthetic harmony. The Hi-MO X10 is the ideal solution for this, whether in the full black or non-full black version. This is primarily made possible by the cell technology itself, as the back contact technology places all positive and negative contacts on the back of the cell - they are invisible. With the Hi-MO X10 and the additional introduction of a zero busbar structure, this design has been further enhanced. The result is a sleek and uniform appearance, making it ideal for applications where aesthetics is a priority.

Overall, the Hi-MO X10 combines all the features demanded by the distributed generation market. High aesthetics, safety, and reliability, as well as high performance and low degradation of 1% after the first year.

Stay tuned for more news to come on the new Hi-MO X10!