PEIE-complexed SnO2 enabled low-temperature solution fabrication of high-performance CsPbI3 all-inorganic perovskite solar cells

CsPbI ₃ all-inorganic perovskite has attracted much attention due to its improved thermal stability compared with organic-inorganic hybrid counterparts. The shallow conduction band of CsPbI ₃ leads to an energy band mismatch between it and the widely used electron transport material SnO ₂ , causing a severe loss in the performance. As a result, most high-efficiency inorganic perovskite solar cells are based on high-temperature sintered TiO ₂ with better energy band alignment. To exploit the potential of SnO ₂ in inorganic perovskite solar cells, SnO ₂ nanocrystals were complexed with ethoxylated polyethyleneimine (PEIE). This strategy affords continuous adjustment of SnO ₂ band structure by varying PEIE content, leading to an ideal energy band alignment with CsPbI ₃. The introduction of PEIE also promotes the growth of CsPbI ₃ films, resulting in larger grains. Moreover, improved charge extraction is achieved after PEIE introduction. As a result, the power conversion efficiency of CsPbI ₃ all-inorganic perovskite solar cells significantly increases from 11.61 % to 13.89 %. Our work provides a simple strategy to produce high-performance CsPbI ₃ all-inorganic perovskite solar cells with low-temperature solution process.