Gao, Xiao-XinDing, BinKanda, HiroyukiFei, ZhaofuLuo, WenZhang, YiShibayama, NaoyukiZuttel, AndreasTirani, Farzaneh FadaeiScopelliti, RosarioKinge, SachinZhang, BaoFeng, YaqingDyson, Paul J.Nazeeruddin, Mohammad Khaja2021-08-142021-08-142021-08-142021-07-2110.1016/j.xcrp.2021.100475https://infoscience.epfl.ch/handle/20.500.14299/180654WOS:000677677000001Organic-inorganic metal-halide perovskite solar cells (PSCs) have achieved a certified power-conversion efficiency (PCE) of 25.5%. However, long-term stability and air stability of the PSCs are still major concerns and hamper commercialization. Herein, we employ a 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 and the TFSI anion and is, additionally, able to form an extensive network of low-barrier H bonds, as an additive in perovskite-precursor solutions. Because of a combination of the Lewis-basic CN groups and the hydrophobic TFSI anion in the IL, highly crystalline perovskite films with large grain sizes are obtained. The IL-modified perovskite films afford PSCs with long-term stability and PCEs > 21%. The stability of unencapsulated devices retain >95% of their original efficiency after 1,000 h of aging. This study demonstrates the considerable potential of TFSI-based ILs to improve the performance of PSCs.Chemistry, MultidisciplinaryEnergy & FuelsMaterials Science, MultidisciplinaryPhysics, MultidisciplinaryChemistryMaterials SciencePhysicscrystal-structureshydrogen-bondefficientcoordinationpassivationenergeticsanionleadsalttext::journal::journal article::research article