The principle limitation of perovskite solar cells is related to their instability and, hence, their limited lifetime. Herein, we employ an imidazolium iodide dopant, 1-methyl-3-(1H,1H,2H,2H-nonafluorohexyl)-imidazolium iodide, containing a perfluorous appendage, which leads to prolonged (unencapsulated, under Ar atmosphere) device activities exceeding 100 days without compromising the power conversion efficiency and other photovoltaic parameters. The extended lifetime of the device can be attributed, at least in part, to the hydrophobic nature of the imidazolium iodide salt. The functionalization of the perovskite material was found to have negligible influence on the perovskite crystal structure.

Ionic liquids continue to find applications in an ever-increasing range of technologies. Here we describe some of the key routes used to prepare ionic liquids and then relate their properties to their applications. In particular, ionic liquids have been used to facilitate crystal growth and, for this reason, are emerging as useful solvents/additives in the preparation of perovskite films. The role of ionic liquids in these films and how they lead to perovskite solar cells with high efficiencies and stabilities is described.

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