Extended Data Fig. 8: In-situ optical spectra and SEM images of tin perovskite films with or without SnF₂+Trp additives.

a-b, Contour plots (a) and line plots (b) of in-situ absorption of tin perovskite films with or without SnF₂+Trp additives measured during the spin-coating process. Before nucleation, the absorption observed at ∼350 nm can be assigned to the [SnI₃]_n^n- cluster formed in precursor solutions (Supplementary Fig. 4) (ref. ⁴). c, In-situ PL spectra of the films measured during the spin-coating process. The arrows indicate the crystallization evolution direction as the spin-coating time increases. d, In-situ absorption spectra of the films measured during the annealing process. e, Cross-sectional and top-view SEM images of the tin perovskite film without additives. The enlarged top-view SEM image shows that the ITO substrate is exposed at perovskite boundaries. All scale bars represent 1 μm. f, PL (front/back side excitation) spectra of the perovskite film without additive.