Cross-sectional SEM images of perovskite films with (a) 0, (b) 1 % H2O additive concentration coated on the PEDOT:PSS/ITO/glass
substrate. (c,d) Corresponding morphology images across a 2 μm × 2 μm scanned area by AFM, where the RMS roughness is measured to be 4.9
and 4.4 nm fo...