Simple Salt May Hold the Key to Stronger Solar Cells

A common laboratory salt may hold the key to making the next generation of solar panels more powerful, more durable, and cheaper to produce. Researchers at University College London (UCL) have discovered that guanidinium thiocyanate, a type of salt, can significantly improve the efficiency and stability of perovskite solar cells—a promising class of materials seen as the future of solar power.

The study, published in the Journal of the American Chemical Society, found that the salt helps control the way perovskite crystals form during fabrication. By slowing down crystal growth, the additive allows smoother, more uniform layers to develop. This reduces the number of microscopic flaws that would otherwise interfere with performance and shorten the lifespan of the solar cell.

Why Perovskites Are Game-Changers

For decades, silicon has dominated the solar industry. Silicon solar panels are reliable and efficient, with the best laboratory prototypes reaching around 27% efficiency and commercial panels on rooftops typically offering about 22%. However, silicon is expensive to process and relatively rigid, limiting its potential applications.

Perovskite solar cells, by contrast, are lightweight, flexible, and cheaper to manufacture because they can be made at lower temperatures with less energy. They are also highly versatile: by adjusting their chemical composition, scientists can tune them to absorb different parts of the sunlight spectrum. This makes them ideal for tandem solar cells, where two or more layers are stacked to harvest more light. In fact, laboratory-made all-perovskite tandem devices have already surpassed 30% efficiency—a world record in solar power generation.

Salt as a Secret Ingredient

The UCL study focused on mixed tin-lead perovskites, which are often used as the bottom layer in tandem devices. These materials are attractive for their ability to absorb infrared light, complementing upper layers that capture visible light. However, tin-based perovskites are notoriously unstable, and improving their performance has been a challenge.

The researchers discovered that adding guanidinium thiocyanate during fabrication gives them more control over the delicate process of crystal formation. Normally, perovskite crystals can form too quickly, leading to defects and rough surfaces. The salt slows this process, allowing the crystals to grow more evenly and produce smooth, high-quality films.

In laboratory tests, the team achieved an efficiency of 22.3% for the mixed tin-lead perovskite cells—very close to the highest ever reported for this material. The results suggest that incorporating guanidinium salts into tandem designs could push efficiencies even higher, potentially beyond the current 30% record.

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Expert Insights

Corresponding author Dr Tom Macdonald (UCL Electronic & Electrical Engineering) emphasized the practical significance of the work:

“Our approach provides a straightforward, effective way to enhance perovskite quality during manufacturing, delivering solar cells that are both higher performing and more stable—key requirements for commercial success.”

First author Yueyao Dong added that the study also provided valuable insight into how crystals grow:

“By modulating crystal formation in a controlled way, we were able to create much higher-quality films. That change translates directly into more efficient and longer-lasting devices.”

Co-author Dr Chieh-Ting Lin (National Chung Hsing University, Taiwan) highlighted the broader implications:

“This opens the door to fine-tuning the structure of perovskites for high-performance tandem solar cells, with the potential to significantly push the limits of efficiency.”

Beyond Efficiency: Durability and Cost

Perovskite solar cells are already praised for their ability to tolerate defects, but the fewer the flaws, the better the performance and durability. By reducing defects, guanidinium thiocyanate may help solve one of the biggest hurdles facing perovskites: their tendency to degrade under heat, moisture, or prolonged sunlight exposure.

Importantly, the salt is inexpensive and easy to incorporate into existing fabrication processes, making it a practical solution for scaling up. Earlier work by the UCL team, published in ACS Energy Letters, also showed that guanidinium can improve charge transport and reduce unwanted ion movement inside the cell—two additional improvements that support efficiency and longevity.

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Toward the Solar Panels of the Future

The rapid rise of perovskite technology over the past decade has been one of the most exciting developments in renewable energy. In just a few years, efficiencies have leapt from under 4% to over 30% in the lab, outpacing the decades-long progress of silicon. With continued refinements—like the use of guanidinium salts—perovskites are now seen as strong candidates to replace or complement silicon in the commercial market.

Looking ahead, perovskite-silicon tandems may dominate in the short term, combining the proven reliability of silicon with the tunability of perovskites. But all-perovskite tandems, boosted by techniques like salt-assisted growth, could eventually surpass them, offering lightweight, flexible, and ultra-efficient solar modules.

As global demand for clean energy surges, breakthroughs like this one highlight how even simple materials—such as a humble salt—can make a big difference. By improving efficiency, stability, and manufacturability, guanidinium thiocyanate could bring us a step closer to next-generation solar panels that are cheaper, more powerful, and built to last.