Perovskite solar cells (PSCs) could be a lower-cost alternative to solar cells based on silicon. The efficiency of PSCs has risen considerably over the past years, up to over 25 %. However, their stability is still insufficient, particularly in the presence of moisture and oxygen. Defects in the perovskite films can lessen their stability and decrease their performance. Two-dimensional (2D) materials can be used to improve the properties of PSCs.

Mingdeng Wei, Fuzhou University, China, and Jiangsu Collaborative Innovation Center of Photovoltaic Science and Engineering, Changzhou, China, and colleagues have used ZnIn₂S₄ nanosheets to passivate the defects of a perovskite film. These nanosheets feature a large number of lone-electron pairs and dangling bonds of S atoms on the surface. Thus, they can interact strongly with the surface and grain boundaries of a perovskite film.

The team synthesized ZnIn₂S₄ nanosheets from zinc nitrate, indium nitrate, and L-cysteine via a hydrothermal method. The perovskite films were prepared via a deposition method from a precursor solution containing HC(NH₂)₂I (formamidinium iodide, FAI), CH₃NH₃I (methylammonium iodide, MAI), CsI, PbI₂, and PbBr₂. A solar cell that contains the perovskite film with ZnIn₂S₄ passivation achieved an efficiency of 20.55 %. The device showed excellent stability in air with a relative humidity of around 15 % for 60 days.

• Defect passivation of a perovskite film by ZnIn₂S₄ nanosheets for efficient and stable perovskite solar cells,
  Jianting Huang, Jinting Li, Linqi Zheng, Guohui Zhong, Yafeng Li, Junming Li, Mingdeng Wei,
  Chem. Commun. 2021.
  https://doi.org/10.1039/d1cc06071f