Fig. 3

Investigation of the origin of perovskite modulation by NMR spectroscopy. a–d ¹⁴N solid-state MAS NMR spectra at 11.7 T, 298 K and a, b 3 kHz, c, d, 20 kHz MAS of bulk mechanochemical a, α-FAPbI₃ and b, α-FAPbI₃ doped with 4 mol% SN. c, d, shows the corresponding close-up views of the center band. The triplet is caused by the ¹H-¹⁴N J-coupling. e–j, ¹³C CP and ¹⁵N CP solid-state MAS NMR spectra at 11.7 T, 105 K and 10 kHz MAS of bulk mechanochemical e, g α-FAPbI₃ and f, h α-FAPbI₃ doped with 4 mol% SN (intensity normalized to the peak of α-FAPbI₃). i, j ¹³C CP solid-state MAS NMR spectra at 11.7 T, 105 K, and 10 kHz MAS of i, bulk mechanochemical α-FAPbI₃ doped with 4 mol% SN (scaled 64 times to highlight the SN resonances) and j neat SN powder. k Schematic representation of the structure of molecular modulators N (purple), S (gray), and SN (purple-gray), and the interaction of the bifunctional molecular modulator SN with Pb²⁺ ions (gray sphere) and perovskite crystal structure (general formula FAPbI₃, where FA is represented by the central blue sphere, while Pb²⁺ and I^– are shown as gray and bright purple spheres, respectively). MAS: magic angle spinning, CP: cross-polarization