Efficient and Stable Mesoporous CsSnI3 Perovskite Solar Cells via Imidazolium-Based Ionic Liquid Additive

作者：Ban, Huaxia; Zhang, Zhiguo; Dai, Letian; Liu, Zhirong; Yu, Haixuan; Shen, Yan; Zhang, Xiao-Li; Zhu, Jun; Wang, Mingkui^*

来源：Solar RRL, 2022, 6(12): 2200827.

DOI：10.1002/solr.202200827

• CsSnI3
• defects
• ionic liquids
• solar cells
• surface undercoordinated Sn2+

Inorganic tin halide perovskite compound with its eco-friendly property has attracted tremendous attention of researchers in the field of lead-free perovskite solar cells. However, the trap-assisted nonradiative recombination caused by deep-level defects originating from surface undercoordinated Sn2+ cations significantly deteriorates the CsSnI3 device's performance. Herein, adding low concentrations of an ionic liquid 1-ethyl-3-methylimidazolium acetate (EMIMAc) shows promise in controlling deep-level defects in CsSnI3 perovskites. Both experimental observation and theoretical simulation reveal that EMIMAc can have strong electrostatic attraction and coordination interaction with the surface undercoordinated Sn2+ through the lone electron pairs of carboxyl functional groups and the donated pi electrons from electron-rich imidazole moieties, leading to a reduced deep-level defect density and a restrained nonradiative recombination. Consequently, the processed CsSnI(3 )perovskite solar cells based on a printable fluorine-doped tin oxide/compact-TiO2/mesoporous-TiO2/Al2O3/NiO/carbon framework achieve a power conversion efficiency as high as 8.54%, which is the champion efficiency among all the reported CsSnI3 mesoporous perovskite solar cells up to now. In addition, the unencapsulated devices have shown an impressive long-term stability with only approximate to 6% efficiency degradation after over 2000 h aging under nitrogen atmosphere.

• 单位
  华中科技大学; 郑州大学