Figure 5: Imaginary parts of the dielectric functions computed without SOC at the GGA-level for CH3NH3PbI3 (a) and (C5H11NH3)2PbI4 (b). The results are given for light polarizations along the three crystallographic axes (1–3) or for a polycrystalline sample in the case of CH3NH3PbI3 (a) and for TE or TM (perpendicular to the stacking axis) polarizations for (C5H11NH3)2PbI4 (b).