Fig. 4. (a) XRD pattern of an x = 0.6 film before (black) and after (red) white-light soaking for 5 minutes at ∼50 mW cm–2, and after 2 h in the dark (blue). The XRD pattern of an x = 0.2 film (green) is offset for comparison. (b) The 200 XRD peak of an x = 0.6 film before (black) and after (red) white-light soaking for 5 minutes at ∼50 mW cm–2. XRD patterns of an x = 0.2 film (dashed green) and an x = 0.7 film (dashed brown) are included for comparison. (c) Williamson–Hall plot of the XRD peak full width at half maximum (B) for the minority (green, larger lattice spacing) and majority (brown, smaller lattice spacing) phases observed in (MA)Pb(Br0.6I0.4)3 (x = 0.6) thin films under illumination. θ is the diffraction angle and λ = 1.54060 Å (copper Kα1) is the X-ray wavelength. The points are labeled with their crystallographic indices. Linear regressions to the data are plotted and the equations are listed. The minority phase was fit assuming the same crystallite size in the 100 and 110 directions but different amounts of strain disorder.
