Figure 3.

(a) TRPL of the perovskite film with and without CEAI treatment. Photoelectron spectroscopy data: XPS core level signals of (b) the Pb 4f_7/2 and (c) N 1s of the perovskite film with (red) and without (black) CEAI treatment; in (c) the cation species are indicated from which the core level signals originate. (d) Combined UPS and IPES spectra of the perovskite film with and without CEAI treatment. The arrows indicate the onsets of the VB and CB. (e) Schematic energy level alignment between the perovskite and the 2D capping layer, extracted from the values determined in (d).