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Clean energy can finally afford to be fully clean.
Clean energy can finally afford to be fully clean. Scientists have created a tin-based perovskite material equipped with a built-in defense against air and moisture, functioning much like a molecular raincoat for solar cells.
The advance is the result of a joint effort led by the University of Wisconsin–Madison, the National Laboratory of the Rockies, and partner institutions. 
Interestingly, this tin perovskites could become a promising eco-friendly alternative to hazardous lead-based cells. However, the previous iterations of tin-based materials typically degrade rapidly when exposed to air and water. This new “raincoat” solves this issue.
The collaborative team revealed a molecular redesign that gives tin-based solar cells built-in protection against these elements. It tackles the single largest obstacle preventing non-toxic perovskite photovoltaics from hitting the commercial market: durability.
“We wanted to find a way to protect these materials while preserving the properties that make them attractive for solar cells,” said Song Jin, a UW–Madison professor of Chemistry. 
With solar panels covering millions of acres, the risk of toxic leaks from damaged or discarded panels remains the biggest roadblock keeping lead-based cells off the market.
Tin perovskites possess superior light-absorbing and electronic properties, but degrade in a short time when exposed to air and moisture. 
Rather than adding a bulky physical layer over the solar cells, the team designed protection straight into the material’s microscopic structure. It all came down to atomic fine-tuning.
Song Jin and his team experimented with different halogen atoms (fluorine, chlorine, and bromine) to alter the material’s organic components. This study engineered a mixed-dimensional (2D/3D) heterostructure.
Interestingly, when the chlorinated version was introduced, something remarkable happened: the perovskite crystals packed together far more tightly than before.
That tight atomic packing acts as a molecular shield. Water and oxygen can’t squeeze inside, creating a protective barrier that keeps them out of the cells.
This structural shift improved both performance and durability. Compared to conventional materials, the new chlorinated tin perovskite maintained its integrity for months in open air. It even survived days fully submerged in water without dissolving.
Further, theoretical models confirmed the mechanism: the tight molecular structure physically blocks oxygen and water from seeping into the vulnerable tin core.
To test its practical viability, the team built working solar cells in partnership with researchers Lei Chen and Kai Zhu at the National Laboratory of the Rockies.
The devices achieved a 16.2 percent power-conversion efficiency, which makes them among the most efficient tin-based cells ever created.
After 1,600 hours sitting in dry air, the cells retained over 95 percent of their initial output. Under severe operational stress with continuous simulated sunlight at a blistering 55°C (131°F), the cells held onto 80 percent of their power after 1,000 hours.
Mostly, solar design meant choosing efficiency or durability. This material shows that companies don’t have to compromise.
“What is exciting is that a relatively small change in the material’s design produces such a large improvement in stability,” said Christopher T. Triggs, who recently received his doctorate in materials chemistry at UW–Madison. 
“It shows how designing the organic components and controlling the way perovskite structures pack together can provide powerful protection of the resulting perovskite materials from the surrounding environment,” the first author added. 
Recognizing the commercial potential of a lead-free, long-lasting solar cell, the Wisconsin Alumni Research Foundation and the National Laboratory of the Rockies have jointly filed a patent for the technology. 
The study was published in the journal Nature Materials. 
Mrigakshi is a science journalist who enjoys writing about space exploration, biology, and technological innovations. Her work has been featured in well-known publications including Nature India, Supercluster, The Weather Channel and Astronomy magazine. If you have pitches in mind, please do not hesitate to email her.
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