Fig. 1

Solvent-controlled growth (SCG) for CsPbI₃ deposition. a Schematic illustration of CsPbI₃-perovskite crystallization procedures via solvent-controlled growth (SCG). b Normalized absorption of CsPbI₃-precursor films with and without SCG, inset shows the precursor film images without and with SCG. c X-ray diffraction (XRD) pattern of CsPbI₃-precursor films without and with solvent-controlled growth (SCG). Without SCG, the diffraction peaks are mainly from the δ-phase CsPbI₃, while after SCG, part of δ- phase CsPbI₃ was transferred into β-phase CsPbI₃ (a slight distorted α-phase CsPbI₃). The diffraction peaks labeled as “*” are the diffraction peaks from the β-phase CsPbI₃. d, e Scanning electron microscopy (SEM) image of CsPbI₃ perovskite precursor film without and with SCG, respectively, scale bar: 5 μm. f, g SEM images of annealed CsPbI₃ perovskite precursor films without and with SCG, respectively, scale bar: 20 μm