Bulk passivation of perovskite films utilizing halide anion ionic liquids

Chemical additives to perovskite precursors constitute a predominant route to passivate defects in perovskite films and improve carrier charge dynamics. In this work, ionic liquids (ILs) with chloride and iodide anions are used as additives for bulk passivation of perovskite films. The ionic liquids in the form of 1‑butyl‑4-methylpyradinium iodide (IL-I) and 1-ethylimidazolium chloride (IL-Cl) are mixed individually with a precursor of Cesium Formamidinium Lead Triiodide and Methylammonium Chloride (CsFAPbI3−MACl). The decay of charge carriers within the perovskite film before and after passivation with ILs was measured by Time Resolved Photoluminescence Spectroscopy (TRPL). The effect of added ILs on the recombination rate of the photocarriers was investigated by analyzing the decay of the TRPL signal in all samples. The average lifetimes obtained within one day of preparations were 79 ns, 73 ns and 275 ns for pristine perovskite, IL-I passivated perovskite and IL-Cl passivated perovskite films, respectively. These values show that the presence of the IL with chloride anion greatly improves the average lifetime of the charge carrier by around 250%, while IL with iodide anion decreased the lifetime by 32% as compared with the pristine perovskite sample. This finding renders the IL-Cl passivated perovskite films as a valuable resource in applications ranging from photoelectric to hydrogen generation devices. © 2023