Perovskite solar cells are often described as the future of solar technology because they can be made cheaply, are lightweight, and have shown impressive efficiency gains.
But despite more than a decade of rapid development, they still face a major obstacle: long-term instability. One of the biggest causes of this instability is the movement of ions inside the material, which gradually damages the semiconductor and lowers performance.
A new study from researchers at the Helmholtz-Zentrum Berlin (HZB) and the University of Potsdam offers promising news.
The team discovered that tin-based perovskites made with an alternative solvent show dramatically lower ion density—only one-tenth that of common lead-based perovskites.
Their findings, published in ACS Energy Letters, suggest that tin perovskites could pave the way for solar cells that are both stable and environmentally friendly.
Most perovskite research so far has focused on materials that use lead as a key component. These lead-based perovskites have reached efficiencies above 27%, a huge jump from 4% when they were first studied.
But lead is toxic, and the materials degrade quickly, which limits commercial adoption.
Tin is a safer alternative, and in theory could match or even surpass the efficiency potential of lead. However, tin perovskite research is still relatively new, and their efficiency has not yet caught up.
One of the biggest issues affecting both lead and tin perovskites is the presence of mobile halide ions, which can wander through the material over time.
As these ions move, they cause chemical changes that slowly degrade the solar cell. To better understand this, the HZB and Potsdam researchers measured the concentration and movement of ions in four widely used perovskite formulations.
They found that tin perovskites already have fewer mobile ions than lead perovskites. Even more striking was what happened when the researchers used a different solvent during production. Tin perovskite made with a DMF-DMI solvent, rather than the commonly used DMSO solvent, showed a dramatic drop in ion density—ten times lower than in lead perovskites. This material also lasted over 600 hours in operation without noticeable degradation.
These results point to a simple but powerful idea: the choice of solvent during fabrication can greatly improve stability. Using the alternative solvent helps avoid unwanted chemical reactions that normally cause tin to oxidize and destabilize the material.
Dr. Artem Musiienko, who led the study, says that the findings strengthen the case for investing more in tin perovskite research. With fewer mobile ions and slower degradation, tin-based perovskites could become a strong candidate for future commercial solar cells. He believes that improving their efficiency is achievable, especially now that a major stability challenge may have a solution.
The study opens the door to developing next-generation thin-film solar cells that are efficient, stable, and free of toxic heavy metals—bringing the world one step closer to cleaner, safer solar energy.
