Tin perovskite study points to more stable lead free solar cells

by Robert Schreiber
Berlin, Germany (SPX) Dec 04, 2025

Perovskite solar cells are under development as candidates for next generation photovoltaic modules, but commercial use remains limited by long term instability driven in part by migrating ions in the absorber layer. A team from Helmholtz-Zentrum Berlin (HZB) and the University of Potsdam has now measured ion densities in four widely used perovskite compounds and found substantial differences between lead and tin based materials.

Perovskite research over the past decade has focused mainly on organometallic compounds in which lead occupies the B site in the ABX3 crystal structure. Lead perovskite solar cells have achieved power conversion efficiencies that have risen from around 4 percent to more than 27 percent, but the use of toxic lead and limited device lifetimes remain major drawbacks.

The lead cation can be replaced by tin, a non toxic element, to remove lead from the device. Tin based perovskite solar cells currently show lower efficiencies than lead devices, yet this may reflect the early stage of research on tin systems rather than a fundamental limit. Dr Artem Musiienko, who leads an HZB research group, notes that "In purely theoretical terms, tin-based perovskite solar cells could even exceed the efficiency of lead-based perovskites."

The study addresses one of the main causes of instability in perovskite cells, the presence of mobile halide ions that move through the lattice, accelerate material degradation, and reduce efficiency during operation. Musiienko's team, together with the Antonio Abate group at HZB and the Felix Lang group at the University of Potsdam, examined four representative perovskite compositions and determined both the density of mobile ions and their migration behavior.

"We found not only that tin based perovskites have a lower concentration of mobile ions but also that they intrinsically exhibit a degradation time five times slower than that of lead based perovskites," says Musiienko. The tin perovskite materials were fabricated in the HZB Hysprint laboratory using two solvent systems: one composition synthesized with dimethyl sulfoxide (DMSO) and another produced with an alternative DMF DMI solvent. The solvent variation approach demonstrates a path to avoid tin oxidation linked to strong DMSO coordination, consistent with earlier investigations reported in Chemistry of Materials in 2022.

The measurements show that the lead based perovskite had the highest mobile ion density among the samples studied. Ion density was somewhat lower in the mixed lead tin perovskite and in a tin perovskite made with the conventional solvent. A major result came from the tin perovskite processed with the alternative solvent: "This was really unexpected: these FASnI3 solar cells have ten times fewer mobile ions than the Pb-based solar cells. We also found that they exhibited excellent stability during operation for over 600 hours," reports PhD researcher Shengnan Zuo from Musiienko's team.

The work strengthens the case for expanded research on tin based perovskites as candidates for stable, lead free thin film solar cells. "We are convinced that tin-based perovskites have enormous potential and that investigating these materials is a very good idea. There are chances to significantly increase their efficiency and stability. This study paves the way for the development of innovative, stable thin-film solar cells with suppressed ion migration," says Musiienko.