Engineering long-term stability into perovskite solar cells via application of a multi-functional TFSI-based ionic liquid

Organic-inorganic metal-halide perovskite solar cells (PSCs) have achieved a certified power-conversion efficiency (PCE) of 25.5%. However, long-term stability and air the PSCs are still major concerns hamper commercialization. Herein, we employ multi-functional ionic liquid (IL), 1,3-bis(cyanomethyl)imidazolium bis(trifluoromethylsulfonyl)imide ([Bcim][TFSI]), which contains an imidazolium cation functionalized with nitrile (CN) groups TFSI anion is, additionally, able to form extensive network low-barrier H bonds, as additive in perovskite-precursor solutions. Because combination Lewis-basic CN hydrophobic IL, highly crystalline films large grain sizes obtained. The IL-modified afford PCEs > 21%. unencapsulated devices retain >95% their original after 1,000 h aging. This study demonstrates considerable potential TFSI-based ILs improve performance PSCs.