Fig. 2

Optical characterization of the PbI₂ film with perovskite seeds. a Dynamic light scattering spectra of the pure PbI₂ solution (0.00028 M), pure perovskite precursor solution (0.00028 M), and the PbI₂ solution mixed with perovskite precursor solution (0.00028 M for PbI₂ and 0.00004 M for perovskite precursor). The size indicates the colloidal particle size in solution. b Illustration of the colloids of perovskite precursor in PbI₂ solution. c, d The absorption and PL spectra of pure PbI₂ film, perovskite seed film with a composition of Cs_0.10FA_0.78MA_0.12PbI_2.55Br_0.45, and PbI₂ film with perovskite seeds (seed concentration 14 vol.%). e–f Confocal PL mapping of the intensity (e) and peak position (f) on the PbI₂ film with perovskite seeds