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

CsPbI3 all-inorganic perovskite has attracted much attention due to its improved thermal stability compared with organic-inorganic hybrid counterparts. The shallow conduction band of CsPbI3 leads to an energy band mismatch between it and the widely used electron transport material SnO2, causing a severe loss in the performance. As a result, most high-efficiency inorganic perovskite solar cells are based on high-temperature sintered TiO2 with better energy band alignment. To exploit the potential of SnO2 in inorganic perovskite solar cells, SnO2 nanocrystals were complexed with ethoxylated polyethyleneimine (PEIE). This strategy affords continuous adjustment of SnO2 band structure by varying PEIE content, leading to an ideal energy band alignment with CsPbI3. The introduction of PEIE also promotes the growth of CsPbI3 films, resulting in larger grains. Moreover, improved charge extraction is achieved after PEIE introduction. As a result, the power conversion efficiency of CsPbI3 all-inorganic perovskite solar cells significantly increases from 11.61 % to 13.89 %. Our work provides a simple strategy to produce high-performance CsPbI3 all-inorganic perovskite solar cells with low-temperature solution process. [Display omitted] •PEIE incorporation enables continuous adjustment of SnO2 band structure.•Favorable energy band alignment is achieved between PEIE-SnO2 and CsPbI3.•PEIE improves SnO2 charge transport and facilitates CsPbI3 crystal growth.•PEIE-SnO2 boosts the PCE of low-temperature processed CsPbI3 PSC to 13.89 %.