Fig. 3: Chemical interaction between additives and perovskite precursors.

a 1H and b 19F NMR spectra of solutions with STFA or 18Cr6 and a combination of them (CrTFA). Obvious shifts of NMR peaks indicate interactions between the components. c IR spectra of an 18Cr6 films, an STFA films, as well as precursors with and without CrTFA. The peak shift indicates interaction between these components. d XPS spectra of the thin films. The shift of the Pb 4f peak shows the interaction between lead and the additives