Fig. 4: Surface morphology and device architecture.

Scanning electron microscopy (SEM) images of (a, b) pure 3D and (c, d) C18 perovskite-coated 3D perovskite film, respectively. Contact angle made by a water droplet on the surface of thin films of (e) pure 3D perovskites and (f) C14-, (g) C16-, (h) C18-coated 3D perovskite measured after stabilizing the water droplet for 10 s. Cross-sectional SEM images of (i) pure 3D and (j) 3D@2D PSCs.