Fig. 1
Structural characterization of modulated perovskite films. a Plane-view (top) and cross-sectional (bottom) SEM images of the pristine (control) and modulator-containing (N, S, and SN) perovskite films deposited on the mesoporous-TiO2/compact-TiO2/FTO. Scale bar represents 200 nm. b Cathodoluminescence (CL) mapping of the pristine (control) and additive-containing (N, S, and SN) perovskite films deposited on the ITO (1 mm) glass substrates. The spatial distribution of green and red light emission, recorded from 530 to 590 nm and from 700 to 800 nm, respectively, reveals the microscopic distribution of PbI2 phase in the perovskite films. Scale bar represents 1 µm. c Structure of N, S, and SN modulators employed in the study, with the corresponding tautomeric forms of SN (the geometries optimized by DFT calculations at B3LYP/6-31 G(d) level of theory are provided in Supplementary Figure 1, whereas the corresponding NMR spectra are shown in Supplementary Figures 2–5 that reveal the predominance of the thione tautomeric form and the interaction with the perovskite and PbI2 phase). ITO: indium tin oxide, FTO: fluorine-doped tin oxide
