Fig. 2: The interaction mechanism between 5-AVA and perovskite.

a FTIR spectra of pure 5-AVA and 5-AVA+PbI2 mixture, where the characteristic C=O stretching vibration peak is marked by gray squares. b, c XPS spectra of (b) Pb 4 f and (c) I 3d for perovskite thin films w/ 5-AVA and w/o 5-AVA. d 13C NMR spectra of pure 5-AVA and 5-AVA+PbI2 mixture. The gray squares highlight the characteristic peaks of 5-AVA. e SCLC measurements of the only-hole devices. f The trap density of states (tDOS) spectra of perovskite thin films.