Dual Effect of Superhalogen Ionic Liquids Ensures Efficient Carrier Transport for Highly Efficient and Stable Perovskite Solar Cells

Defect accumulation and nonradiative recombination at the interface of the electron-transport layer (ETL) and the photosensitive layer are inevitable obstacles to efficient and stable perovskite solar cells (PSCs). Herein, we reported a dual-effect interface modification strategy that employs potassium tetrafluoroborate (KBF4) molecules for the simultaneous passivation of the SnO2/perovskite interface and perovskite grain boundaries. The introduced highly electronegative BF4– enriched at the SnO2 surface and the chemical bond interaction between them can effectively reduce the hydroxyl (−OH) group defects on the surface of SnO2, improve electron mobility, and reduce nonradiative recombination. Meanwhile, partial K+ diffuses into the grain boundaries, causing the halogen ions to be uniformly distributed in the perovskite film and resulting in better crystallinity. Therefore, the performance of the experimental device was improved from 20.34 to 22.90% compared with the reference device, with a high electrical performance (JSC = 25.1 mA cm–2, VOC = 1.137 V). In particular, the unencapsulated target PSCs retained 85% of their original PCE after aging for 1000 h under ambient conditions (70 ± 10% RH) in the dark.