Trihydrazine Dihydriodide‐Assisted Fabrication of Efficient Formamidinium Tin Iodide Perovskite Solar Cells.

The deposition of a uniform and dense tin‐based perovskite layer with low defect‐caused background carrier density is crucial for achieving efficient tin perovskite solar cells (PSCs). These defects are mainly caused by the rapid oxidation of Sn2+ to Sn4+ in tin perovskite during device fabrication. Herein, trihydrazine dihydriodide ((N2H4)3(HI)2) is used as an additive for solution deposition of a formamidinium tin iodide (FASnI3) perovskite layer. The resultant FASnI3 layer is homogeneous with full surface coverage; moreover, the content of Sn4+ is significantly reduced in the film from the SnI2 precursor owing to the reductive property of (N2H4)3(HI)2. With the high‐quality FASnI3 layer as a light absorber, planar‐heterojunction perovskite solar cells are fabricated, exhibiting a maximum power conversion efficiency of 8.48% and good reproducibility. This work opens new possibilities for achieving efficient lead‐free tin‐based perovskite solar cells. [ABSTRACT FROM AUTHOR]