US team claims stability record for 16.19%-efficient 2D/3D tin perovskite solar cell

Researchers at the University of Toledo (UToledo) in the United States claim to have fabricated the most air-stable two-dimensional/three-dimensional (2D/3D) tin (Sn) perovskite solar cell to date as part of a research project aimed at identifying lead (Pb)-free perovskite materials for PV applications.

In 2D/3D perovskite solar cells, a 2D perovskite phase is combined with a conventional 3D perovskite absorber, typically at an interface or in a mixed-dimensional structure. The 2D layer can passivate defects, improve charge-carrier transport and extraction, and suppress ion migration. Cells incorporating 2D materials may also offer greater stability than conventional 3D devices due to the protective effect of their organic ligands.

The architecture may be particularly useful for lead-free tin perovskite solar cells, which continue to face stability challenges. A 2D/3D tin-halide perovskite device unveiled in 2025 achieved a certified efficiency of 16.65% and operated stably under continuous illumination for more than 1,500 hours. Such architectures could therefore help improve the stability of lower-toxicity tin-based absorbers, although their stability benefits are not exclusive to lead-free perovskites.

“Tin perovskites are considered the leading lead-free alternative, but a key drawback is that tin oxidizes readily when exposed to oxygen and moisture. Our research is significant because it points to a potential solution to this major challenge for tin-perovskite photovoltaics,” the research lead author, Jiahao Xie, told pv magazine.

“In general, Pb-based perovskites are currently more cost-effective than Sn-based perovskites because the lead source materials are less expensive than their tin-based counterparts,” said co-author Lei Chen. “However, Sn-based perovskites are more environmentally friendly than Pb-based perovskites. This consideration is particularly important when evaluating the long-term commercialization potential of perovskite solar cells.”

The current efficiencies of Sn-based perovskite solar cells remain well below their theoretical efficiency. However, the highest reported efficiency for Sn perovskite solar cells is around 17%, and the efficiency achieved in our study remains among the highest reported to date. Therefore, we believe that the results demonstrated in this work is highly competitive and satisfactory given the current state of the field.”

For the proposed solar cell design, the scientists used spacers based on phenethylammonium (PEA) and its halogenated derivatives to protect the perovskite surface, control crystal growth, reduce defects, and limit degradation caused by moisture and oxygen. By changing the halogen attached to PEA, the researchers could tune properties such as hydrophobicity and intermolecular interactions, which allowed them to determine which spacer produces the most crystalline and air-stable tin perovskite.

They identified 4-chlorophenethylammonium iodide (4ClPEA)) as the most effective spacer cation, reportedly producing 2D tin halide perovskites with tight interlayer packing, minimal structural distortion, and strongly reduced oxygen and water diffusion. Adding 4-chlorophenethylammonium to 3D formamidinium tin iodide (FASnI₃) perovskite material also improved film crystallinity, crystal orientation, and surface morphology.

The solar cell was built with a susbstrate made of indium tin oxide (ITO), a hole transport layer (HTL) made of PEDOT:PSS, the 2D-3D perovskite absorber, an electron transport layer (ETL) based on indene-C60 bisadduct (ICBA), abathocuproine (BCP) buffer layer, and a silver (Ag) metal contact.

The researchers added 5 mol% of different spacer salts to the tin halide perovskite layer, with 4ClPEAI delivering the strongest results. The 4ClPEAI device reached a power conversion efficiency of 16.19%, while average efficiency across 14 devices rose from 10.34% for the control to 15.88%.

The researchers attributed the improvement to enhanced film crystallinity, crystal orientation and morphology. Open-circuit voltage, short-circuit current density and fill factor also improved, while the bandgap remained around 1.44 eV.

The 4ClPEAI devices also showed the highest stability, retaining 95% of their initial efficiency for more than 1,600 hours in dry air. Under continuous one-sun illumination at 55 C in air, they retained 80% after 1,000 hours.

The scientists claim the cells are the most air-stable tin-perovskite of its kind to date.

“It’s just as important as the results that we are able to explain why it works to use a chlorinated molecule as the spacer,” Xie concluded. “This gives us a clear design principle for future lead-free perovskites.”

The novel cell concept was presented in “A chlorinated organic cation enables stable 2D/3D tin iodide perovskite photovoltaics,” published in nature materials. The research team comprised academics from University of Wisconsin–Madison, the National Laboratory of the Rockies, the University of Colorado Boulder, all based in the United States.

The post appeared first on pv magazine Global.