An international collaboration led by Antonio Abate, HZB, and Zhao-Kui Wang, Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University, China, has achieved a breakthrough that opens up a path to non-toxic perovskite-based solar cells that provides stable performance over a long period.

They use tin instead of lead but have created a two-dimensional structure by inserting organic groups within the material, which leads to so-called 2D Ruddlesden-Popper phases.

"We use phenylethylammonium chloride (PEACl) as an additive to the perovskite layers. Then we carry out a heat treatment while the PEACl molecules migrate into the perovskite layer. This results in vertically ordered stacks of two-dimensional perovskite crystals" explains first author Dr Meng Li. Li is a postdoc in Abate's group.

At the Shanghai Synchrotron Radiation Facility (SSRF), they were able to precisely analyze the morphology and crystal characteristics of the perovskite films after different annealing treatments.

The best of these lead-free perovskite solar cells achieved an efficiency of 9.1% and high stability values, both under daytime conditions and in the dark. The PEACl molecules accumulate between the crystalline perovskite layers as a result of the heat treatment and form a barrier that prevents the tin cations from oxidizing. "This work paves the way for more efficient and stable lead-free perovskite solar cells," Abate is convinced.

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