Recently, two groundbreaking research achievements from LONGi Green Energy were published consecutively in the prestigious academic journal *Nature*, showcasing the company's latest progress in cutting-edge technologies.

On November 10, 2025, *Nature* published online a significant advancement in silicon-based tandem solar cell research by a research team from LONGi Green Energy, in collaboration with Soochow University and Xi'an Jiaotong University. The team's ultra-thin crystalline silicon-perovskite tandem solar cell achieved a small-area device efficiency of 33.4% certified by the U.S. National Renewable Energy Laboratory (NREL), and a commercial-size silicon wafer-level flexible tandem solar cell achieved an efficiency of 29.8% certified by the Fraunhofer Institute for Solar Energy Research (Fraunhofer ISE) in Germany. This is the first and only world record in the photovoltaic field to be certified by an internationally authoritative institution for the efficiency of flexible crystalline silicon-perovskite tandem solar cells. This breakthrough lays a solid foundation for the commercial development of flexible silicon-based tandem solar cells in lightweight/flexible high-power photovoltaic applications such as space photovoltaics and automotive photovoltaics.

On November 13, 2025, *Nature* published online the research results of LONGi Green Energy's collaborative team with Sun Yat-sen University and Lanzhou University on the amorphous-polycrystalline hybrid back contact structure (HIBC) solar cell. Previously, on April 11, 2025, LONGi Green Energy announced that its HIBC cell had broken the world record for single-crystal silicon cell efficiency with 27.81%. Based on LONGi's focused BC cell platform technology, the HIBC cell combines the advantages of high-temperature polycrystalline and low-temperature amorphous silicon cell technologies, representing a culmination of silicon-based solar cell technology. Its development is unprecedentedly challenging due to the need for its manufacturing process to accommodate both high-temperature and low-temperature cell processes. The team achieved a certified efficiency of 27.81% and a fill factor of 87.55% on LONGi's self-developed industrial-grade Terex silicon wafers, both setting new world records. It is worth noting that the hybrid back contact structure is a novel and validated high-efficiency cell technology pioneered by a Chinese team, possessing complete independent intellectual property rights and extremely high technological barriers. The team's laser-induced local crystallization technology and in-situ edge passivation technology are compatible with existing production lines, greatly promoting the high-quality industrialization of mass-produced silicon solar cells with higher efficiency and lower cost. According to the latest progress, modules based on HIBC cells have achieved a conversion efficiency of 25.9% and an output power of 700 W (2.7 square meter module).

Previously, in October 2024, *Nature* published back-to-back (2024, 635, pp. 596–603 and 604–609) two research results from the team on HBC and silicon-based tandem cells. This latest consecutive publication of two groundbreaking R&D achievements by the company in *Nature* demonstrates LONGi Green Energy's determination and strength in leading industry development and combating inefficiency through technological innovation.

Research Achievement 1: Crystalline Silicon Hybrid Back Contact Structure Solar Cell Achieves Conversion Efficiency Breakthrough of 27.81%

Back contact structure solar cells, by placing all N-type and P-type contact areas and electrodes on the back of the cell, minimize shading losses on the front side, making it an inevitable choice for the continuous breakthrough of conversion efficiency in crystalline silicon photovoltaics. However, key challenges such as the difficulty in simultaneously achieving the passivation performance and contact resistance of the P-type contact area, the difficulty in simultaneously controlling longitudinal carrier transport and lateral leakage, and the existence of recombination and leakage in the edge region severely limit the potential of this high-efficiency cell structure. To address these three challenges, the team innovatively developed an amorphous-polycrystalline hybrid back contact structure (HIBC) solar cell that integrates laser-induced crystallization and in-situ edge passivation.

The main innovations are threefold:

(1) Amorphous silicon contacts using a low-temperature process were employed in the P-type region, while polycrystalline silicon contacts using a high-temperature process were employed in the N-type region, resulting in excellent P-type and N-type passivated contacts, respectively.

(2) To address the challenge of poor vertical conductivity in the P-type amorphous silicon contact layer, a laser-induced local crystallization technique was developed. This technique transforms only the submicron-scale region at the pyramid tip into nanocrystalline silicon, significantly reducing the vertical contact resistivity while maintaining the lateral leakage performance of the original amorphous silicon film layer in other regions, which has a small polarity overlap area.

(3) An in-situ edge passivation technique was developed, simultaneously applying a robust passivation coating to the fragile cutting edges during battery manufacturing, effectively suppressing carrier recombination in the edge region. Based on the device's excellent fully passivated surface and electrical performance, the research team further constructed a new physical model that correlates the diode's ideal factor with the carrier loss mechanism. This model quantitatively describes the impact of different recombination mechanisms on the ideal factor and clarifies the constraints of bulk recombination and surface recombination on the fill factor, providing clear theoretical guidance for high-performance battery design. Research Achievement Two: Lightweight and Flexible Perovskite/Crystalline Silicon Devices with Full Silicon Wafer Dimensions

Perovskite/crystalline silicon tandem solar cell technology, by combining the advantages of two semiconductor materials, significantly increases theoretical efficiency and is recognized as a next-generation disruptive photovoltaic technology. Traditionally, monocrystalline silicon is considered a rigid and brittle material. However, the atomic structure of silicon possesses a certain degree of elastic deformation capability. When the silicon wafer thickness is reduced to tens of micrometers (traditional silicon wafers are typically around 120-200 micrometers thick), even with a bending radius of less than 2 centimeters, the surface stress of the silicon wafer remains below its intrinsic fracture threshold, preventing crack formation. Therefore, ultrathin silicon wafers can meet the deformation requirements of lightweight and flexible devices. However, the perovskite functional layer is highly susceptible to delamination and failure at the interface under repeated bending and temperature changes, leading to a significantly reduced lifespan.

To address this challenge, the team employed an innovative and optimized process structure design, constructing a loose yet dense dual-layer buffer layer. The carefully designed loose SnOx layer acts like a spring mattress, absorbing and dissipating strain energy, effectively mitigating mechanical stress caused by ion bombardment during fabrication and deformation during subsequent use. Meanwhile, the dense SnOx layer ensures efficient interfacial charge extraction and robust electrical connections.

This dual-layer structure precisely resolves the conflict between stress buffering and efficient power transmission at the micro- and nanoscale, ensuring that the stacked device achieves excellent bending resistance while maintaining superior power generation capabilities. The team achieved a power conversion efficiency of nearly 30% on an ultrathin all-silicon wafer stacked device only 60 micrometers thick. This ultrathin stacked device can be folded in half with a bending radius of 1.5 cm, weighs less than 4.4 grams, and boasts a power-to-weight ratio of 1.77 W/g. In a small-scale laboratory setting, the team also achieved an internationally recognized conversion efficiency record of 33.4%. This research fully demonstrates the superior efficiency and bending fatigue resistance of this stacked battery structure, as well as its future application potential.