Towards Lead-free Stable Perovskite Solar Cells
HZB collaboration adds phenylethylammonium chloride (PEACl) to perovskite layers
An international cooperation led by Antonio Abate, at Helmholtz-Zentrum Berlin (HZB), and Zhao-Kui Wang, at 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 published the results in the journal ACS Energy Letters.
The team still use tin instead of lead but have created a 2D 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 2D perovskite crystals," explains first author Meng Li. Li is a postdoc in Abate's group and has organised the close cooperation with the Chinese partners. At the Shanghai Synchrotron Radiation Facility (SSRF), they were able to precisely analyse the morphology and crystal characteristics of the perovskite films after different annealing treatments.
The illustration shows the changes in the structure of FASnI3:PEACl films during treatment at different temperatures.
The best of these lead-free perovskite solar cells achieved an efficiency of 9.1 percent 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 oxidising. "This work paves the way for more efficient and stable lead-free perovskite solar cells," Abate is convinced.
'Tin halide perovskite films made of highly oriented 2D crystals enable more efficient and stable lead-free perovskite solar cells' by Meng Li et al; ACS Energy Lett. 2020