Harnessing chemical functions of ionic liquids for perovskite solar cells

The remarkable ramping of record power conversion efficiencies in perovskite solar cells (PSCs) has stimulated the growth of this technology towards commercialization. However, there remain challenges and opportunities for further improving their efficiency and stability. Featuring the variety of functional group in the constituting ions, ionic liquids (ILs) exhibit versatile properties and functions that can be leveraged to the development of improved PSCs. Herein with a systematic review on the recent progress in the application of ILs to PSCs, we show that based on the different roles of ILs in the film and device settings, IL can facilitate the thin-film synthesis of perovskites, improve the properties of charge-transport layers, and ameliorate the interfacial energetics at device interfaces. In particular, the ILs-perovskite interactions of two different types (Lewis acid-base interaction and hydrogen bonding) are the essential chemistries underpinning observed efficiency and stability improvements in PSCs, which represent a vast research paradigm in the field of energy chemistry.