fig1

Figure 1. Top-view SEM images of pristine perovskite films (A). Top-view SEM images of perovskite films modified by PI solution with different concentrations: (B) 0.5 wt%; (C) 1.0 wt%; (D) 1.5 wt%; and (E) 2.0 wt%. The corresponding water contact angles based on the above perovskite films: (F) for (A); (G) for (B); (H) for (C); (I) for (D); and (J) for (E). SEM: Scanning electron microscopy. PI: polyimide.