Figure 4.

Local Cl content in the MAPbI_3-xCl_x film: a-d) PTIR spectra obtained in selected color coded locations as indicated in Figure 3a as a function of annealing e) Local bandgaps (left axis) and local Cl % content (right axis) extrapolated from the linear fitting PTIR spectra from 9 different locations as a function of annealing: as prepared sample (A0, black squares), 95 °C for 5 min (A5, red circle), additional annealing at 95 °C for 5 min and at 110 °C for 10 min (A20, blue triangle) and after additional annealing at 110 °C for 10 min (A30, purple triangle). The as prepared sample has a large variability in the local bandgap and Cl molar fraction. Upon annealing the local bandgap and Cl content decreases at all locations, approaching the bandgap of the MAPbI₃ reference film (green horizontal line) for the longer annealing time. The light green rectangle and error bars represent a single standard deviation in the calculation of the local bandgap due to the linear fitting of the PTIR absorption spectra.