Organic-inorganic hybrid nature enables efficient and stable CsPbI3-based perovskite solar cells

Summary

CsPbI₃-based perovskite solar cells (PSCs) have attracted intense research interest since the inorganic absorber layer has better thermal stability compared with hybrid perovskites. However, CsPbI₃ suffers from structural instability due to an easily induced phase transition from the photoactive phase to the photoinactive phase. Introducing (CH₃)₂NH₂I (dimethylammonium iodide [DMAI]) into the CsPbI₃ precursor solution stabilizes the tetragonal (β-phase) of CsPbI₃, but there is still debate about whether DMA⁺ is incorporated in the perovskite structure. Here, we report unambiguous evidence for the formation of tetragonal (β-) (DMA, Cs)PbI₃ by substituting the small ionic radius Cs⁺ with the large organic cation DMA⁺. The organic-inorganic hybrid β-(DMA, Cs)PbI₃ shows a better optoelectronic properties than inorganic orthorhombic (γ-phase) CsPbI₃. Consequently, PSCs based on β-(DMA, Cs)PbI₃ exhibit a champion power conversion efficiency of 19.76%. These observations suggest that hybrid β-(DMA, Cs)PbI₃, with a dominant inorganic composition, is preferable compared with inorganic γ-CsPbI₃ for efficient and stable PSCs.