Figure 1

SEM of the perovskite layer on substrates with different surface roughness. The grain size form of the perovskites correlates with the surface roughness of the substrate. (A) Perovskite on a smooth ITO substrate showing relative straight grains. (B) Perovskite on SnO2/FTO, the roughest substrate, with ca. 48 nm surface roughness showing less orientation orthogonal to the substrate. (C) Top-view SEM image of perovskites layers on ITO and on (D) FTO. Voids between crystals are more clearly pronounced on the ITO substrate.