Fig. 1: Synthesis and characterization of CBz-PAI molecule.

a, Synthetic route of CBz-PAI. b, The UV–Vis absorption spectra of PbI2, CBz-PAI and CBz-PAI/PbI2 with molar ratio 2:1. The inset shows a digital image of PbI2 film, CBz-PAI/PbI2 film. c, CV of CBz-PAI in acetonitrile with 0.1 M LiTFSI (EFcHOMO = −5.13 V versus vacuum). d, Energy level diagram. The levels for perovskite (FAPbI3) and spiro-OMeTAD were taken from literature49; the ones for CBz-PAI were determined from CV shown in c.