Efficient and stable industrial-size perovskite/silicon tandems with long-span bisphosphonic self-assembled molecules
This study introduces a long-span bisphosphonic self-assembled molecule (S2) that enables uniform, stable interfacial coverage on industrial-scale textured silicon, resulting in certified 32.6% efficient and highly durable perovskite/silicon tandem solar cells and modules.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
Solar energy has long been limited by a fundamental ceiling: a single layer of material can only capture a specific slice of sunlight, letting the rest pass through or turning it into wasted heat. To break this barrier, scientists have turned to stacking two different light-capturing layers on top of each other, creating a tandem cell. The top layer is designed to catch high-energy light, while the bottom layer, usually made of silicon, catches the lower-energy light that slips through. When these two work together, they can theoretically generate far more electricity than a standard solar panel. However, making these stacked cells work efficiently on a large, industrial scale has proven difficult. The bottom silicon layer is not flat; it is covered in tiny, jagged pyramids to help trap light. While this texture is good for capturing sunlight, it creates a rough landscape that is incredibly hard to coat evenly with the delicate chemical layers needed to make the top cell function. If the coating is uneven, the device fails, and the promise of high efficiency remains locked in the laboratory.
A team of researchers has now solved this coating problem by designing a new type of molecular layer that can drape perfectly over the rough silicon surface, leading to record-breaking efficiency for large solar panels. The core of their success lies in a custom-built molecule that acts as a self-assembling bridge between the silicon and the top light-capturing layer. Previous attempts to create these bridges used small molecules that could only grab onto the silicon at a single point. On the jagged peaks and ridges of the industrial silicon texture, these small molecules could not reach across to the next spot, leaving gaps and causing the film to break apart. Other researchers tried using long, chain-like molecules to cover more ground, but these tended to clump together in messy piles rather than forming a smooth sheet. The new design, developed by scientists from Peking University, Trina Solar, and other institutions, combines the best of both worlds. They created a molecule with a long, flexible backbone that can stretch across the sharp tips of the silicon pyramids, while its ends are equipped with two strong anchors instead of one.
The researchers found that this specific design allows the molecules to spread out evenly, covering every inch of the textured surface without clumping or leaving gaps. Because the molecules are so long and flexible, they can bend and conform to the shape of the silicon, reaching from one side of a pyramid to the other. The two anchors at the ends grip the surface tightly, ensuring the layer stays in place even under heat and stress. This uniform coverage is critical because it allows electricity to flow smoothly from the top layer to the bottom layer without getting stuck or leaking away. When the team tested this new molecule in a laboratory setting on a small piece of silicon, the resulting solar cell converted 34.3% of the sunlight hitting it into electricity. This is a significant jump from previous records for this type of small cell.
More importantly, the team proved that this approach works on the massive scale required for real-world power generation. They applied the same molecule to a large silicon wafer, roughly the size of a standard industrial solar panel, using a machine that coats the surface like a printer. The large panel achieved a certified efficiency of 32.6%, which is the highest efficiency ever recorded for a solar cell of that size. To ensure this technology is ready for the real world, the researchers subjected the panels to harsh conditions that mimic years of outdoor use. They baked the panels in high heat and humidity and cycled them through extreme temperature changes. After these tests, the panels retained more than 90% of their original power output. When they installed a module made of these large cells outdoors, it continued to produce consistent energy over the course of a month.
The study demonstrates that the key to unlocking the full potential of next-generation solar power is not just in the materials that capture light, but in how those materials are connected to the silicon beneath them. By engineering a molecule that is long enough to span the rough terrain of industrial silicon and strong enough to hold on, the researchers have removed a major bottleneck that had kept high-efficiency solar cells confined to small laboratory samples. This work suggests that the path to cheaper, more powerful solar energy is clear, provided the delicate interface between layers can be managed with the same precision as the light-capturing materials themselves. The results indicate that these tandem cells are no longer just a theoretical possibility but a viable technology ready for mass production.
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